[screen-lua.git] / src / doc / screen.texinfo

\input texinfo @c -*-texinfo-*-
@c %**start of header
@c vi:set wm=5
@setfilename screen.info
@settitle Screen User's Manual
@dircategory General Commands
@finalout
@setchapternewpage odd
@c %**end of header
@set version 4.1.0

@direntry
* Screen: (screen).             Full-screen window manager.
@end direntry

@c For examples, use a literal escape in info.
@ifinfo
@set esc ^[
@end ifinfo
@iftex
@set esc <ESC>
@end iftex

@ifinfo
This file documents the @code{Screen} virtual terminal manager.

Copyright (c) 1993-2003 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end ifinfo

@titlepage
@title Screen
@subtitle The virtual terminal manager
@subtitle for Version @value{version}
@subtitle Aug 2003

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1993-2003 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end titlepage

@node Top, Overview, (dir), (dir)

@ifinfo
@top Screen
This file documents the @code{Screen} virtual terminal manager, version
@value{version}.
@end ifinfo

@menu
* Overview::                    Preliminary information.
* Getting Started::             An introduction to @code{screen}.
* Invoking Screen::             Command line options for @code{screen}.
* Customization::               The @file{.screenrc} file.
* Commands::                    List all of the commands.
* New Window::                  Running a program in a new window.
* Selecting::                   Selecting a window to display.
* Session Management::          Suspend/detach, grant access, connect sessions.
* Regions::                     Split-screen commands.
* Window Settings::             Titles, logging, etc.
* Virtual Terminal::            Controlling the @code{screen} VT100 emulation.
* Copy and Paste::              Exchanging text between windows and sessions.
* Subprocess Execution::        I/O filtering with @code{exec}.
* Key Binding::                 Binding commands to keys.
* Flow Control::                Trap or pass flow control characters.
* Termcap::                     Tweaking your terminal's termcap entry.
* Message Line::                The @code{screen} message line.
* Logging::                     Keeping a record of your session.
* Startup::                     Functions only useful at @code{screen} startup.
* Miscellaneous::               Various other commands.
* String Escapes::              Inserting current information into strings
* Environment::                 Environment variables used by @code{screen}.
* Files::                       Files used by @code{screen}.
* Credits::                     Who's who of @code{screen}.
* Bugs::                        What to do if you find a bug.
* Installation::                Getting @code{screen} running on your system.
* Concept Index::               Index of concepts.
* Command Index::               Index of all @code{screen} commands.
* Keystroke Index::             Index of default key bindings.
@end menu

@node Overview, Getting Started, Top, Top
@chapter Overview
@cindex overview

Screen is a full-screen window manager that multiplexes a physical
terminal between several processes, typically interactive shells.  Each
virtual terminal provides the functions of the DEC VT100 terminal and,
in addition, several control functions from the ISO 6429 (ECMA 48, ANSI X3.64)
and ISO 2022 standards (e.g. insert/delete line and support for multiple
character sets).  There is a scrollback history buffer for each virtual
terminal and a copy-and-paste mechanism that allows the user to move
text regions between windows.
 
When @code{screen} is called, it creates a single window with a shell in
it (or the specified command) and then gets out of your way so that you
can use the program as you normally would.  Then, at any time, you can
create new (full-screen) windows with other programs in them (including
more shells), kill the current window, view a list of the active
windows, turn output logging on and off, copy text between windows, view
the scrollback history, switch between windows, etc.  All windows run
their programs completely independent of each other.  Programs continue
to run when their window is currently not visible and even when the
whole screen session is detached from the user's terminal.

When a program terminates, @code{screen} (per default) kills the window
that contained it.  If this window was in the foreground, the display
switches to the previously displayed window; if none are left,
@code{screen} exits.

Everything you type is sent to the program running in the current
window.  The only exception to this is the one keystroke that is used to
initiate a command to the window manager.  By default, each command
begins with a control-a (abbreviated @kbd{C-a} from now on), and is
followed by one other keystroke.  The command character (@pxref{Command
Character}) and all the key bindings (@pxref{Key Binding}) can be fully
customized to be anything you like, though they are always two
characters in length.

@code{Screen} does not understand the prefix @kbd{C-} to mean control.
Please use the caret notation (@kbd{^A} instead of @kbd{C-a}) as arguments
to e.g. the @code{escape} command or the @code{-e} option. @code{Screen}
will also print out control characters in caret notation.

The standard way to create a new window is to type @kbd{C-a c}.  This
creates a new window running a shell and switches to that window
immediately, regardless of the state of the process running in the
current window.  Similarly, you can create a new window with a custom
command in it by first binding the command to a keystroke (in your
@file{.screenrc} file or at the @kbd{C-a :} command line) and then using it 
just like the @kbd{C-a c} command.  In addition, new windows can be created by 
running a command like:

@example
screen emacs prog.c
@end example

@noindent
from a shell prompt within a previously created window.  This will not
run another copy of @code{screen}, but will instead supply the command
name and its arguments to the window manager (specified in the $STY environment
variable) who will use it to create the new window.  The above example would 
start the @code{emacs} editor (editing @file{prog.c}) and switch to its window.

If @file{/etc/utmp} is writable by @code{screen}, an appropriate record
will be written to this file for each window, and removed when the
window is closed.  This is useful for working with @code{talk},
@code{script}, @code{shutdown}, @code{rsend}, @code{sccs} and other
similar programs that use the utmp file to determine who you are. As
long as @code{screen} is active on your terminal, the terminal's own
record is removed from the utmp file.  @xref{Login}.

@node Getting Started, Invoking Screen, Overview, Top
@chapter Getting Started
@cindex introduction

Before you begin to use @code{screen} you'll need to make sure you have
correctly selected your terminal type, just as you would for any other
termcap/terminfo program.  (You can do this by using @code{tset},
@code{qterm}, or just @code{set term=mytermtype}, for example.)

If you're impatient and want to get started without doing a lot more
reading, you should remember this one command: @kbd{C-a ?} (@pxref{Key
Binding}).  Typing these two characters will display a list of the
available @code{screen} commands and their bindings. Each keystroke is
discussed in the section on keystrokes (@pxref{Default Key Bindings}).
Another section (@pxref{Customization}) deals with the contents of your
@file{.screenrc}.

If your terminal is a ``true'' auto-margin terminal (it doesn't allow
the last position on the screen to be updated without scrolling the
screen) consider using a version of your terminal's termcap that has
automatic margins turned @emph{off}.  This will ensure an accurate
and optimal update of the screen in all circumstances.  Most terminals
nowadays have ``magic'' margins (automatic margins plus usable last
column).  This is the VT100 style type and perfectly suited for
@code{screen}.
If all you've got is a ``true'' auto-margin terminal @code{screen}
will be content to use it, but updating a character put into the last
position on the screen may not be possible until the screen scrolls or
the character is moved into a safe position in some other way. This
delay can be shortened by using a terminal with insert-character
capability.

@xref{Special Capabilities}, for more information about telling
@code{screen} what kind of terminal you have.

@node Invoking Screen, Customization, Getting Started, Top
@chapter Invoking @code{Screen}
@cindex invoking
@cindex options
@cindex command line options

Screen has the following command-line options:

@table @samp
@item -a
Include @emph{all} capabilities (with some minor exceptions) in each
window's termcap, even if @code{screen} must redraw parts of the display
in order to implement a function.

@item -A
Adapt the sizes of all windows to the size of the display.  By default,
@code{screen} may try to restore its old window sizes when attaching to
resizable terminals (those with @samp{WS} in their descriptions, e.g.
@code{suncmd} or some varieties of @code{xterm}).

@item -c @var{file}
Use @var{file} as the user's configuration file instead of the default
of @file{$HOME/.screenrc}.

@item -d [@var{pid.sessionname}]
@itemx -D [@var{pid.sessionname}]
Do not start @code{screen}, but instead detach a @code{screen} session
running elsewhere (@pxref{Detach}).  @samp{-d} has the same effect as
typing @kbd{C-a d} from the controlling terminal for the session.
@samp{-D} is the equivalent to the power detach key.  If no session can
be detached, this option is ignored.  In combination with the 
@code{-r}/@code{-R} option more powerful effects can be achieved:

@table @code
@item -d -r
Reattach a session and if necessary detach it first.
@item -d -R   
Reattach a session and if necessary detach  or  even create it first.
@item -d -RR  
Reattach a session and if necessary detach or create it.
Use the first session if more than one session is available.
@item -D -r   
Reattach a session. If necessary detach  and  logout remotely first.
@item -D -R   
Attach here and now. In detail this means: If a session  is running, 
then reattach. If necessary detach and logout remotely first.  If it
was not running create it and notify the user.
This is the author's favorite.
@item -D -RR  
Attach here and now. Whatever that  means, just do it.
@end table

@emph{Note}: It is a good idea to check the status of your sessions
with @code{screen -list} before using this option.

@item -e @var{xy}
Set the command character to @var{x}, and the character generating a
literal command character (when typed after the command character) to
@var{y}.  The defaults are @kbd{C-a} and @kbd{a}, which can be specified
as @samp{-e^Aa}.  When creating a @code{screen} session, this option
sets the default command character. In a multiuser session all users
added will start off with this command character. But when attaching
to an already running session, this option only changes the command
character of the attaching user.
This option is equivalent to the commands @code{defescape} or 
@code{escape} respectively.  (@pxref{Command Character}).

@item -f
@itemx -fn
@itemx -fa
Set flow-control to on, off, or automatic switching mode, respectively.
This option is equivalent to the @code{defflow} command (@pxref{Flow
Control}).

@item -h @var{num}
Set the history scrollback buffer to be @var{num} lines high.
Equivalent to the @code{defscrollback} command (@pxref{Copy}).

@item -i
Cause the interrupt key (usually @kbd{C-c}) to interrupt the display
immediately when flow control is on.  This option is equivalent to the
@code{interrupt} argument to the @code{defflow} command (@pxref{Flow
Control}). Its use is discouraged.

@item -l
@itemx -ln
Turn login mode on or off (for @file{/etc/utmp} updating).  This option
is equivalent to the @code{deflogin} command (@pxref{Login}).

@item -ls [@var{match}]
@itemx -list [@var{match}]
Do not start @code{screen}, but instead print a list of session
identification strings (usually of the form @var{pid.tty.host};
@pxref{Session Name}).  Sessions marked @samp{detached} can be resumed
with @code{screen -r}.  Those marked @samp{attached} are running and
have a controlling terminal.  If the session runs in multiuser mode,
it is marked @samp{multi}.  Sessions marked as @samp{unreachable} either
live on a different host or are dead. 
An unreachable session is considered dead, when its name matches either the
name of the local host, or the specified parameter, if any.
See the @code{-r} flag for a description how to construct matches.
Sessions marked as @samp{dead} should be thoroughly checked and removed.  
Ask your system administrator if you are not sure.
Remove sessions with the @samp{-wipe} option.

@item -L
Tell @code{screen} to turn on automatic output logging for the
windows.

@item -m
Tell @code{screen} to ignore the @code{$STY} environment variable.  When
this option is used, a new session will always be created, regardless of
whether @code{screen} is being called from within another @code{screen}
session or not. This flag has a special meaning in connection
with the @samp{-d} option:
@table @code
@item -d -m
Start @code{screen} in @emph{detached} mode. This creates a new
session but doesn't attach to it. This is useful for system startup
scripts.
@item -D -m
This also starts @code{screen} in @emph{detached} mode, but doesn't fork
a new process. The command exits if the session terminates.
@end table

@item -p @var{name_or_number}
Preselect a window. This is useful when you want to reattach to a
specific window or you want to send a command via the @samp{-X}
option to a specific window. As with screen's select command, @samp{-}
selects the blank window. As a special case for reattach, @samp{=}
brings up the windowlist on the blank window.

@item -q
Suppress printing of error messages. In combination with @samp{-ls} the exit 
value is set as follows: 9 indicates a directory without sessions. 10 
indicates a directory with running but not attachable sessions. 11 (or more) 
indicates 1 (or more) usable sessions.
In combination with @samp{-r} the exit value is as follows: 10 indicates that 
there is no session to resume. 12 (or more) indicates that there are 2 (or 
more) sessions to resume and you should specify which one to choose. 
In all other cases @samp{-q} has no effect.

@item -r [@var{pid.sessionname}]
@itemx -r @var{sessionowner}/[@var{pid.sessionname}]
Resume a detached @code{screen} session.  No other options (except
combinations with @samp{-d} or @samp{-D}) may be specified, though 
the session name
(@pxref{Session Name}) may be needed to distinguish between multiple
detached @code{screen} sessions.
The second form is used to connect to another user's screen session which
runs in multiuser mode. This indicates that screen should look for
sessions in another user's directory. This requires setuid-root.

@item -R
Resume the first appropriate detached @code{screen} session.  If
successful, all other command-line options are ignored.  If no detached
session exists, start a new session using the specified options, just as
if @samp{-R} had not been specified.  This option is set by default if
screen is run as a login-shell (actually screen uses @samp{-xRR} in
that case).
For combinations with the 
@samp{-D}/@samp{-d} option see there.

@item -s @var{program}
Set the default shell to be @var{program}.  By default, @code{screen}
uses the value of the environment variable @code{$SHELL}, or
@file{/bin/sh} if it is not defined.  This option is equivalent to the
@code{shell} command (@pxref{Shell}).

@item -S @var{sessionname}
Set the name of the new session to @var{sessionname}.  This option can
be used to specify a meaningful name for the session in place of the
default @var{tty.host} suffix.  This name identifies the session for the
@code{screen -list} and @code{screen -r} commands.  This option is
equivalent to the @code{sessionname} command (@pxref{Session Name}).

@item -t @var{name}
Set the title (name) for the default shell or specified program.
This option is equivalent to the @code{shelltitle} command
(@pxref{Shell}).

@item -U
Run screen in UTF-8 mode. This option tells screen that your terminal
sends and understands UTF-8 encoded characters. It also sets the default
encoding for new windows to @samp{utf8}.

@item -v
Print the version number.

@item -wipe [@var{match}]
List available screens like @code{screen -ls}, but remove destroyed
sessions instead of marking them as @samp{dead}. 
An unreachable session is considered dead, when its name matches either 
the name of the local host, or the explicitly given parameter, if any.
See the @code{-r} flag for a description how to construct matches.

@item -x
Attach to a session which is already attached elsewhere (multi-display
mode). 
@code{Screen} refuses to attach from within itself. 
But when cascading multiple screens, loops are not detected; take care.


@item -X
Send the specified command to a running screen session. You can use
the @code{-d} or @code{-r} option to tell screen to look only for 
attached or detached screen sessions. Note that this command doesn't
work if the session is password protected.

@end table

@node Customization, Commands, Invoking Screen, Top
@chapter Customizing @code{Screen}
@cindex customization

You can modify the default settings for @code{screen} to fit your tastes
either through a personal @file{.screenrc} file which contains commands
to be executed at startup, or on the fly using the @code{colon} command.

@menu
* Startup Files::               The @file{.screenrc} file.
* Source::                      Read commands from a file.
* Colon::                       Entering customization commands interactively.
@end menu

@node Startup Files, Source,  , Customization
@section The @file{.screenrc} file
@cindex .screenrc
@cindex screenrc
When @code{screen} is invoked, it executes initialization commands from
the files @file{.screenrc} in the user's home directory and
@file{/usr/local/etc/screenrc}.  These defaults can be overridden in the 
following ways:
For the global screenrc file @code{screen} searches for the environment
variable @code{$SYSSCREENRC} (this override feature may be disabled at
compile-time).  The user specific screenrc file is
searched for in @code{$SCREENRC}, then 
@file{@code{$HOME}/.screenrc}.  The command line option @samp{-c}
specifies which file to use (@pxref{Invoking Screen}.  Commands in these
files are used to set options, bind commands to keys, and to
automatically establish one or more windows at the beginning of
your @code{screen} session.  Commands are listed one per line, with
empty lines being ignored.  A command's arguments are separated by tabs
or spaces, and may be surrounded by single or double quotes.  A @samp{#}
turns the rest of the line into a comment, except in quotes.
Unintelligible lines are warned about and ignored.  Commands may contain
references to environment variables.  The syntax is the shell-like
@code{$VAR} or @code{$@{VAR@}}.  Note that this causes incompatibility
with previous @code{screen} versions, as now the '$'-character has to be
protected with '\' if no variable substitution is intended. A string in 
single-quotes is also protected from variable substitution.

Two configuration files are shipped as examples with your screen
distribution: @file{etc/screenrc} and @file{etc/etcscreenrc}. They
contain a number of useful examples for various commands.

@node Source, Colon, Startup Files, Customization
@section Source
@deffn Command source file
(none)@*
Read and execute commands from file @var{file}. Source  commands
may be nested to a maximum recursion level of ten. If @var{file}
is not an absolute path and  screen  is already processing  a
source command, the parent directory of the running source
command file is used to search for the new command file  before
screen's current directory.

Note  that termcap/terminfo/termcapinfo commands only work
at startup and reattach time, so they must be reached  via
the default screenrc files to have an effect.
@end deffn

@node Colon,  , Source, Customization
@section Colon
Customization can also be done online, with this command:

@kindex :
@deffn Command colon
(@kbd{C-a :})@* 
Allows you to enter @file{.screenrc} command lines.  Useful for
on-the-fly modification of key bindings, specific window creation and
changing settings.  Note that the @code{set} keyword no longer exists,
as of version 3.3.  Change default settings with commands starting with
@samp{def}.  You might think of this as the @code{ex} command mode of
@code{screen}, with @code{copy} as its @code{vi} command mode
(@pxref{Copy and Paste}).
@end deffn

@node Commands, New Window, Customization, Top
@chapter Commands

A command in @code{screen} can either be bound to a key, invoked from a
screenrc file, or called from the @code{colon} prompt
(@pxref{Customization}).  As of version 3.3, all commands can be bound
to keys, although some may be less useful than others.
For a number of real life working examples of the most important
commands see the files @file{etc/screenrc} and @file{etc/etcscreenrc}
of your screen distribution.

In this manual, a command definition looks like this:

@table @asis
@item -- Command: command [-n] ARG1 [ARG2] @dots{}
(@var{keybindings})@*
This command does something, but I can't remember what.
@end table

An argument in square brackets (@samp{[]}) is optional.  Many commands
take an argument of @samp{on} or @samp{off}, which is indicated as
@var{state} in the definition.

@menu
* Default Key Bindings::        @code{screen} keyboard commands.
* Command Summary::             List of all commands.
@end menu

@node Default Key Bindings, Command Summary,  , Commands
@section Default Key Bindings

As mentioned previously, each keyboard command consists of a
@kbd{C-a} followed by one other character.  For your convenience, all
commands that are bound to lower-case letters are also bound to their
control character counterparts (with the exception of @kbd{C-a a}; see
below).  Thus, both @kbd{C-a c} and @kbd{C-a C-c} can be used to create
a window.

The following table shows the default key bindings:

@table @asis
@item @kbd{C-a '}
(select)@*
Prompt for a window identifier and switch.
@xref{Selecting}.

@item @kbd{C-a "}
(windowlist -b)@*
Present a list of all windows for selection.
@xref{Selecting}.

@item @kbd{C-a 0@dots{}9, -}
(select 0@dots{}select 9, select -)@*
Switch to window number 0@dots{}9, or the blank window.
@xref{Selecting}.

@item @kbd{C-a @key{Tab}}
(focus)@*
Switch the input focus to the next region.  @xref{Regions}.

@item @kbd{C-a C-a}
(other)@*
Toggle to the window displayed previously.  If this window does no 
longer exist, @code{other} has the same effect as @code{next}.
@xref{Selecting}.

@item @kbd{C-a a}
(meta)@*
Send the command character (C-a) to window. See @code{escape} command.
@xref{Command Character}. 

@item @kbd{C-a A}
(title)@*
Allow the user to enter a title for the current window.
@xref{Naming Windows}.

@item @kbd{C-a b}
@itemx @kbd{C-a C-b}
(break)@*
Send a break to the tty.
@xref{Break}.

@item @kbd{C-a B}
(pow_break)@*
Close and reopen the tty-line.
@xref{Break}.

@item @kbd{C-a c}
@itemx @kbd{C-a C-c}
(screen)@*
Create a new window with a shell and switch to that window.
@xref{Screen Command}.

@item @kbd{C-a C}
(clear)@*
Clear the screen.  @xref{Clear}.

@item @kbd{C-a d}
@itemx @kbd{C-a C-d}
(detach)@*
Detach @code{screen} from this terminal.  @xref{Detach}.

@item @kbd{C-a D D}
(pow_detach)@*
Detach and logout.  @xref{Power Detach}.

@item @kbd{C-a f}
@itemx @kbd{C-a C-f}
(flow)@*
Cycle flow among @samp{on}, @samp{off} or @samp{auto}.  @xref{Flow}.

@item @kbd{C-a F}
(fit)@*
Resize the window to the current region size.  @xref{Window Size}.

@item @kbd{C-a C-g}
(vbell)@*
Toggle visual bell mode.  @xref{Bell}.

@item @kbd{C-a h}
(hardcopy)@*
Write a hardcopy of the current window to the file ``hardcopy.@var{n}''.
@xref{Hardcopy}.

@item @kbd{C-a H}
(log)@* 
Toggle logging of the current window to the file ``screenlog.@var{n}''.
@xref{Log}.

@item @kbd{C-a i}
@itemx @kbd{C-a C-i}
(info)@*
Show info about the current window.  @xref{Info}.

@item @kbd{C-a k}
@itemx @kbd{C-a C-k}
(kill)@*
Destroy the current window.  @xref{Kill}.

@item @kbd{C-a l}
@itemx @kbd{C-a C-l}
(redisplay)@*
Fully refresh the current window.  @xref{Redisplay}.

@item @kbd{C-a L}
(login)@*
Toggle the current window's login state.  @xref{Login}.

@item @kbd{C-a m}
@itemx @kbd{C-a C-m}
(lastmsg)@*
Repeat the last message displayed in the message line.
@xref{Last Message}.

@item @kbd{C-a M}
(monitor)
Toggle monitoring of the current window.  @xref{Monitor}.

@item @kbd{C-a @key{SPC}}
@itemx @kbd{C-a n}
@itemx @kbd{C-a C-n}
(next)@*
Switch to the next window.  @xref{Selecting}.

@item @kbd{C-a N}
(number)@*
Show the number (and title) of the current window.  @xref{Number}.

@item @kbd{C-a p}
@itemx @kbd{C-a C-p}
@itemx @kbd{C-a C-h}
@itemx @kbd{C-a @key{BackSpace}}
(prev)@*
Switch to the previous window (opposite of @kbd{C-a n}).
@xref{Selecting}.

@item @kbd{C-a q}
@itemx @kbd{C-a C-q}
(xon)@*
Send a ^Q (ASCII XON) to the current window.  @xref{XON/XOFF}.

@item @kbd{C-a Q}
(only)@*
Delete all regions but the current one.  @xref{Regions}.

@item @kbd{C-a r}
@itemx @kbd{C-a C-r}
(wrap)@*
Toggle the current window's line-wrap setting (turn the current window's
automatic margins on or off).  @xref{Wrap}.

@item @kbd{C-a s}
@itemx @kbd{C-a C-s}
(xoff)@*
Send a ^S (ASCII XOFF) to the current window.  @xref{XON/XOFF}.

@item @kbd{C-a S}
(split)@*
Split the current region into two new ones.  @xref{Regions}.

@item @kbd{C-a t}
@itemx @kbd{C-a C-t}
(time)@*
Show the load average and xref.  @xref{Time}.

@item @kbd{C-a v}
(version)@*
Display the version and compilation date.  @xref{Version}.

@item @kbd{C-a C-v}
(digraph)@*
Enter digraph.  @xref{Digraph}.

@item @kbd{C-a w}
@itemx @kbd{C-a C-w}
(windows)@*
Show a list of active windows.  @xref{Windows}.

@item @kbd{C-a W}
(width)@*
Toggle between 80 and 132 columns.  @xref{Window Size}.

@item @kbd{C-a x}
@itemx @kbd{C-a C-x}
(lockscreen)@*
Lock your terminal.  @xref{Lock}.

@item @kbd{C-a X}
(remove)@*
Kill the current region.  @xref{Regions}.

@item @kbd{C-a z}
@itemx @kbd{C-a C-z}
(suspend)@*
Suspend @code{screen}.  @xref{Suspend}.

@item @kbd{C-a Z}
(reset)@*
Reset the virtual terminal to its ``power-on'' values.  
@xref{Reset}.

@item @kbd{C-a .}
(dumptermcap)@*
Write out a @file{.termcap} file.  @xref{Dump Termcap}.

@item @kbd{C-a ?}
(help)@*
Show key bindings.  @xref{Help}.

@item @kbd{C-a C-\}
(quit)@*
Kill all windows and terminate @code{screen}.  @xref{Quit}.

@item @kbd{C-a :}
(colon)@*
Enter a command line.  @xref{Colon}.

@item @kbd{C-a [}
@itemx @kbd{C-a C-[}
@itemx @kbd{C-a @key{ESC}}
(copy)@*
Enter copy/scrollback mode.  @xref{Copy}.

@item @kbd{C-a ]}
@itemx @kbd{C-a C-]}
(paste .)@*
Write the contents of the paste buffer to the stdin queue of the
current window.  @xref{Paste}.

@item @kbd{C-a @{}
@itemx @kbd{C-a @}}
(history)@*
Copy and paste a previous (command) line.  @xref{History}.

@item @kbd{C-a >}
(writebuf)@*
Write the paste buffer out to the screen-exchange file.
@xref{Screen Exchange}.

@item @kbd{C-a <}
(readbuf)@*
Read the screen-exchange file into the paste buffer.
@xref{Screen Exchange}.

@item @kbd{C-a =}
(removebuf)@*
Delete the screen-exchange file.  @xref{Screen Exchange}.

@item @kbd{C-a _}
(silence)@*
Start/stop monitoring the current window for inactivity. @xref{Silence},

@item @kbd{C-a ,}
(license)@*
Show the copyright page.

@item @kbd{C-a *}
(displays)@*
Show the listing of attached displays.
@end table

@node Command Summary,  , Default Key Bindings, Commands
@section Command Summary
@cindex command summary 

@table @code
@item acladd @var{usernames}
Allow other users in this session.  @xref{Multiuser Session}.
@item aclchg @var{usernames permbits list}
Change a user's permissions.  @xref{Multiuser Session}.
@item acldel @var{username}
Disallow other user in this session.  @xref{Multiuser Session}.
@item aclgrp @var{usrname} [@var{groupname}]
Inherit permissions granted to a group leader. @xref{Multiuser Session}.
@item aclumask [@var{users}]+/-@var{bits} ...
Predefine access to new windows. @xref{Umask}.
@item activity @var{message}
Set the activity notification message.  @xref{Monitor}.
@item addacl @var{usernames}
Synonym to @code{acladd}.  @xref{Multiuser Session}.
@item allpartial @var{state}
Set all windows to partial refresh.  @xref{Redisplay}.
@item altscreen @var{state}
Enables support for the "alternate screen" terminal capability.  @xref{Redisplay}.
@item at [@var{ident}][@kbd{#}@var{|}@kbd{*}@var{|}@kbd{%}] @var{command} [@var{args}]
Execute a command at other displays or windows.  @xref{At}.
@item attrcolor @var{attrib} [@var{attribute/color-modifier}]
Map attributes to colors.  @xref{Attrcolor}.
@item autodetach @var{state}
Automatically detach the session on SIGHUP.  @xref{Detach}.
@item autonuke @var{state}
Enable a clear screen to discard unwritten output.  @xref{Autonuke}.
@item backtick @var{id} @var{lifespan} @var{autorefresh} @var{command} [@var{args}]
Define a command for the backtick string escape.  @xref{Backtick}.
@item bce [@var{state}]
Change background color erase.  @xref{Character Processing}.
@item bell_msg [@var{message}]
Set the bell notification message.  @xref{Bell}.
@item bind [-c @var{class}] @var{key} [@var{command} [@var{args}]]
Bind a command to a key.  @xref{Bind}.
@item bindkey [@var{opts}] [@var{string} [@var{cmd args}]]
Bind a string to a series of keystrokes. @xref{Bindkey}.
@item blanker
Blank the screen.  @xref{Screen Saver}.
@item blankerprg
Define a blanker program.  @xref{Screen Saver}.
@item break [@var{duration}]
Send a break signal to the current window.  @xref{Break}.
@item breaktype [@var{tcsendbreak} | @var{TCSBRK} | @var{TIOCSBRK}]
Specify how to generate breaks.  @xref{Break}.
@item bufferfile [@var{exchange-file}]
Select a file for screen-exchange.  @xref{Screen Exchange}.
@item c1 [@var{state}]
Change c1 code processing.  @xref{Character Processing}.
@item caption @var{mode} [@var{string}]
Change caption mode and string.  @xref{Regions}.
@item chacl @var{usernames permbits list}
Synonym to @code{aclchg}. @xref{Multiuser Session}.
@item charset @var{set}
Change character set slot designation.  @xref{Character Processing}.
@item chdir [@var{directory}]
Change the current directory for future windows.  @xref{Chdir}.
@item clear
Clear the window screen.  @xref{Clear}.
@item colon
Enter a @code{screen} command.  @xref{Colon}.
@item command [-c @var{class}]
Simulate the screen escape key.  @xref{Command Character}.
@item compacthist [@var{state}]
Selects compaction of trailing empty lines.  @xref{Scrollback}.
@item console [@var{state}]
Grab or ungrab console output.  @xref{Console}.
@item copy
Enter copy mode.  @xref{Copy}.
@item copy_reg [@var{key}]
Removed. Use @code{paste} instead.  @xref{Registers}.
@item crlf @var{state}
Select line break behavior for copying.  @xref{Line Termination}.
@item debug @var{state}
Suppress/allow debugging output.  @xref{Debug}.
@item defautonuke @var{state}
Select default autonuke behavior.  @xref{Autonuke}.
@item defbce @var{state}
Select background color erase.  @xref{Character Processing}.
@item defbreaktype [@var{tcsendbreak} | @var{TCSBRK} | @var{TIOCSBRK}]
Specify the default for generating breaks.  @xref{Break}.
@item defc1 @var{state}
Select default c1 processing behavior.  @xref{Character Processing}.
@item defcharset [@var{set}]
Change defaul character set slot designation.  @xref{Character Processing}.
@item defencoding @var{enc}
Select default window encoding.  @xref{Character Processing}.
@item defescape @var{xy}
Set the default command and @code{meta} characters.  @xref{Command Character}.
@item defflow @var{fstate}
Select default flow control behavior.  @xref{Flow}.
@item defgr @var{state}
Select default GR processing behavior.  @xref{Character Processing}.
@item defhstatus [@var{status}]
Select default window hardstatus line.  @xref{Hardstatus}.
@item deflog @var{state}
Select default window logging behavior.  @xref{Log}.
@item deflogin @var{state}
Select default utmp logging behavior.  @xref{Login}.
@item defmode @var{mode}
Select default file mode for ptys.  @xref{Mode}.
@item defmonitor @var{state}
Select default activity monitoring behavior.  @xref{Monitor}.
@item defnonblock @var{state}|@var{numsecs}
Select default nonblock mode.  @xref{Nonblock}.
@item defobuflimit @var{limit}
Select default output buffer limit.  @xref{Obuflimit}.
@item defscrollback @var{num}
Set default lines of scrollback.  @xref{Scrollback}.
@item defshell @var{command}
Set the default program for new windows.  @xref{Shell}.
@item defsilence @var{state}
Select default idle monitoring behavior.  @xref{Silence}.
@item defslowpaste @var{msec}
Select the default inter-character timeout when pasting.  @xref{Paste}.
@item defutf8 @var{state}
Select default character encoding.  @xref{Character Processing}.
@item defwrap @var{state}
Set default line-wrapping behavior.  @xref{Wrap}.
@item defwritelock @var{on|off|auto}
Set default writelock behavior.  @xref{Multiuser Session}.
@item defzombie [@var{keys}]
Keep dead windows.  @xref{Zombie}.
@item detach [-h]
Disconnect @code{screen} from the terminal.  @xref{Detach}.
@item digraph
Enter digraph sequence.  @xref{Digraph}.
@item dinfo
Display terminal information.  @xref{Info}.
@item displays
List currently active user interfaces. @xref{Displays}.
@item dumptermcap
Write the window's termcap entry to a file.  @xref{Dump Termcap}.
@item echo [-n] @var{message}
Display a message on startup.  @xref{Startup}.
@item encoding @var{enc} [@var{denc}]
Set the encoding of a window.  @xref{Character Processing}.
@item escape @var{xy}
Set the command and @code{meta} characters.  @xref{Command Character}.
@item eval @var{command1} [@var{command2} ...]
Parse and execute each argument. @xref{Eval}.
@item exec [[@var{fdpat}] @var{command} [@var{args} ...]]
Run a subprocess (filter).  @xref{Exec}.
@item fit
Change window size to current display size.  @xref{Window Size}.
@item flow [@var{fstate}]
Set flow control behavior.  @xref{Flow}.
@item focus
Move focus to next region.  @xref{Regions}.
@item gr [@var{state}]
Change GR charset processing.  @xref{Character Processing}.
@item hardcopy [-h] [@var{file}]
Write out the contents of the current window.  @xref{Hardcopy}.
@item hardcopy_append @var{state}
Append to hardcopy files.  @xref{Hardcopy}.
@item hardcopydir @var{directory}
Place, where to dump hardcopy files.  @xref{Hardcopy}.
@item hardstatus [@var{state}]
Use the hardware status line.  @xref{Hardware Status Line}.
@item height [@var{lines} [@var{cols}]]
Set display height.  @xref{Window Size}.
@item help [-c @var{class}]
Display current key bindings.  @xref{Help}.
@item history
Find previous command beginning @dots{}.  @xref{History}.
@item hstatus @var{status}
Change the window's hardstatus line.  @xref{Hardstatus}.
@item idle [@var{timeout} [@var{cmd} @var{args}]]
Define a screen saver command.  @xref{Screen Saver}.
@item ignorecase [@var{state}]
Ignore character case in searches.  @xref{Searching}.
@item info
Display window settings.  @xref{Info}.
@item ins_reg [@var{key}]
Removed, use @code{paste} instead.  @xref{Registers}.
@item kill
Destroy the current window.  @xref{Kill}.
@item lastmsg
Redisplay the last message.  @xref{Last Message}.
@item license
Display licensing information.  @xref{Startup}.
@item lockscreen
Lock the controlling terminal.  @xref{Lock}.
@item log [@var{state}]
Log all output in the current window.  @xref{Log}.
@item logfile @var{filename}
Place where to collect logfiles.  @xref{Log}.
@item login [@var{state}]
Log the window in @file{/etc/utmp}.  @xref{Login}.
@item logtstamp [@var{state}]
Configure logfile time-stamps.  @xref{Log}.
@item mapdefault
Use only the default mapping table for the next keystroke.  @xref{Bindkey Control}.
@item mapnotnext
Don't try to do keymapping on the next keystroke.  @xref{Bindkey Control}.
@item maptimeout @var{timo}
Set the inter-character timeout used for keymapping. @xref{Bindkey Control}.
@item markkeys @var{string}
Rebind keys in copy mode.  @xref{Copy Mode Keys}.
@item maxwin @var{n}
Set the maximum window number. @xref{Maxwin}.
@item meta
Insert the command character.  @xref{Command Character}.
@item monitor [@var{state}]
Monitor activity in window.  @xref{Monitor}.
@item msgminwait @var{sec}
Set minimum message wait.  @xref{Message Wait}.
@item msgwait @var{sec}
Set default message wait.  @xref{Message Wait}.
@item multiuser @var{state}
Go into single or multi user mode. @xref{Multiuser Session}.
@item nethack @var{state}
Use @code{nethack}-like error messages.  @xref{Nethack}.
@item next
Switch to the next window.  @xref{Selecting}.
@item nonblock [@var{state}|@var{numsecs}]
Disable flow control to the current display. @xref{Nonblock}.|@var{numsecs}]
@item number [@var{n}]
Change/display the current window's number.  @xref{Number}.
@item obuflimit [@var{limit}]
Select output buffer limit.  @xref{Obuflimit}.
@item only
Kill all other regions.  @xref{Regions}.
@item other
Switch to the window you were in last.  @xref{Selecting}.
@item partial @var{state}
Set window to partial refresh.  @xref{Redisplay}.
@item password [@var{crypted_pw}]
Set reattach password.  @xref{Detach}.
@item paste [@var{src_regs} [@var{dest_reg}]]
Paste contents of paste buffer or registers somewhere.  @xref{Paste}.
@item pastefont [@var{state}]
Include font information in the paste buffer.  @xref{Paste}.
@item pow_break
Close and Reopen the window's terminal.  @xref{Break}.
@item pow_detach
Detach and hang up.  @xref{Power Detach}.
@item pow_detach_msg [@var{message}]
Set message displayed on @code{pow_detach}.  @xref{Power Detach}.
@item prev
Switch to the previous window.  @xref{Selecting}.
@item printcmd [@var{cmd}]
Set a command for VT100 printer port emulation.  @xref{Printcmd}.
@item process [@var{key}]
Treat a register as input to @code{screen}.  @xref{Registers}.
@item quit
Kill all windows and exit.  @xref{Quit}.
@item readbuf [-e @var{encoding}] [@var{filename}]
Read the paste buffer from the screen-exchange file.  @xref{Screen Exchange}.
@item readreg [-e @var{encoding}] [@var{reg} [@var{file}]]
Load a register from paste buffer or file.  @xref{Registers}.
@item redisplay
Redisplay the current window.  @xref{Redisplay}.
@item register [-e @var{encoding}] @var{key} @var{string}
Store a string to a register.  @xref{Registers}.
@item remove
Kill current region.  @xref{Regions}.
@item removebuf
Delete the screen-exchange file.  @xref{Screen Exchange}.
@item reset
Reset the terminal settings for the window.  @xref{Reset}.
@item resize [(+/-)lines]
Grow or shrink a region
@item screen [@var{opts}] [@var{n}] [@var{cmd} [@var{args}]]
Create a new window.  @xref{Screen Command}.
@item scrollback @var{num}
Set size of scrollback buffer.  @xref{Scrollback}.
@item select [@var{n}]
Switch to a specified window.  @xref{Selecting}.
@item sessionname [@var{name}]
Name this session.  @xref{Session Name}.
@item setenv [@var{var} [@var{string}]]
Set an environment variable for new windows.  @xref{Setenv}.
@item setsid @var{state}
Controll process group creation for windows.  @xref{Setsid}.
@item shell @var{command}
Set the default program for new windows.  @xref{Shell}.
@item shelltitle @var{title}
Set the default name for new windows.  @xref{Shell}.
@item silence [@var{state}|@var{seconds}]
Monitor a window for inactivity.  @xref{Silence}.
@item silencewait @var{seconds}
Default timeout to trigger an inactivity notify.  @xref{Silence}.
@item sleep @var{num}
Pause during startup.  @xref{Startup}.
@item slowpaste @var{msec}
Slow down pasting in windows.  @xref{Paste}.
@item source @var{file}
Run commands from a file.  @xref{Source}.
@item sorendition [@var{attr} [@var{color}]]
Change text highlighting.  @xref{Sorendition}.
@item split
Split region into two parts.  @xref{Regions}.
@item startup_message @var{state}
Display copyright notice on startup.  @xref{Startup}.
@item stuff @var{string}
Stuff a string in the input buffer of a window.  @xref{Paste}.
@item su [@var{username} [@var{password} [@var{password2}]]]
Identify a user. @xref{Multiuser Session}.
@item suspend
Put session in background.  @xref{Suspend}.
@item term @var{term}
Set @code{$TERM} for new windows.  @xref{Term}.
@item termcap @var{term} @var{terminal-tweaks} [@var{window-tweaks}]
Tweak termcap entries for best performance.  @xref{Termcap Syntax}.
@item terminfo @var{term} @var{terminal-tweaks} [@var{window-tweaks}]
Ditto, for terminfo systems.  @xref{Termcap Syntax}.
@item termcapinfo @var{term} @var{terminal-tweaks} [@var{window-tweaks}]
Ditto, for both systems.  @xref{Termcap Syntax}.
@item time [@var{string}]
Display time and load average.  @xref{Time}.
@item title [@var{windowtitle}]
Set the name of the current window.  @xref{Title Command}.
@item umask [@var{users}]+/-@var{bits} ...
Synonym to @code{aclumask}. @xref{Umask}.
@item unsetenv @var{var}
Unset environment variable for new windows.  @xref{Setenv}.
@item utf8 [@var{state} [@var{dstate}]]
Select character encoding of the current window.  @xref{Character Processing}.
@item vbell [@var{state}]
Use visual bell.  @xref{Bell}.
@item vbell_msg [@var{message}]
Set vbell message.  @xref{Bell}.
@item vbellwait @var{sec}
Set delay for vbell message.  @xref{Bell}.
@item version
Display @code{screen} version.  @xref{Version}.
@item wall @var{message}
Write a message to all displays.  @xref{Multiuser Session}.
@item width [@var{cols} [@var{lines}]]
Set the width of the window.  @xref{Window Size}.
@item windowlist [-b] | string [@var{string}] | title [@var{title}]
Present a list of all windows for selection.  @xref{Windowlist}.
@item windows
List active windows.  @xref{Windows}.
@item wrap [@var{state}]
Control line-wrap behavior.  @xref{Wrap}.
@item writebuf [-e @var{encoding}] [@var{filename}]
Write paste buffer to screen-exchange file.  @xref{Screen Exchange}.
@item writelock @var{on}|@var{off}|@var{auto}
Grant exclusive write permission.  @xref{Multiuser Session}.
@item xoff
Send an XOFF character.  @xref{XON/XOFF}.
@item xon
Send an XON character.  @xref{XON/XOFF}.
@item zmodem [off|auto|catch|pass]
Define how screen treats zmodem requests.  @xref{Zmodem}.
@item zombie [@var{keys} [onerror] ]
Keep dead windows.  @xref{Zombie}.
@end table

@node New Window, Selecting, Commands, Top
@chapter New Window

This section describes the commands for creating a new window for
running programs.  When a new window is created, the first available
number from the range 0@dots{}9 is assigned to it.
The number of windows is limited at compile-time by the MAXWIN
configuration parameter.

@menu
* Chdir::                       Change the working directory for new windows.
* Screen Command::              Create a new window.
* Setenv::                      Set environment variables for new windows.
* Shell::                       Parameters for shell windows.
* Term::                        Set the terminal type for new windows.
* Window Types::                Creating different types of windows.
@end menu

@node Chdir, Screen Command,  , New Window
@section Chdir
@deffn Command chdir [directory]
(none)@*
Change the current directory of @code{screen} to the specified directory
or, if called without an argument, to your home directory (the value of
the environment variable @code{$HOME}).  All windows that are created by means
of the @code{screen} command from within @file{.screenrc} or by means of
@kbd{C-a : screen @dots{}} or @kbd{C-a c} use this as their default
directory.  Without a @code{chdir} command, this would be the directory
from which @code{screen} was invoked.  Hardcopy and log files are always
written to the @emph{window's} default directory, @emph{not} the current
directory of the process running in the window.  You can use this
command multiple times in your @file{.screenrc} to start various windows
in different default directories, but the last @code{chdir} value will
affect all the windows you create interactively.
@end deffn

@node Screen Command, Setenv, Chdir, New Window
@section Screen Command
@kindex c
@kindex C-c
@deffn Command screen [opts] [n] [cmd [args]]
(@kbd{C-a c}, @kbd{C-a C-c})@*
Establish a new window.  The flow-control options (@samp{-f}, @samp{-fn}
and @samp{-fa}), title option (@samp{-t}), login options
(@samp{-l} and @samp{-ln}) , terminal type option (@samp{-T @var{term}}),
the all-capability-flag (@samp{-a}) and scrollback option 
(@samp{-h @var{num}}) may be specified with each command. 
The option (@samp{-M}) turns monitoring on for this window.
The option (@samp{-L}) turns output logging on for this window.
If an optional number @var{n} in the range 0@dots{}9 is given,
the window number @var{n} is assigned to the newly created window (or,
if this number is already in-use, the next available number).  If a
command is specified after @code{screen}, this command (with the given
arguments) is started in the window; otherwise, a shell is created.

Screen has built in some functionality of @samp{cu} and @samp{telnet}.
@xref{Window Types}.
@end deffn

Thus, if your @file{.screenrc} contains the lines

@example
# example for .screenrc:
screen 1
screen -fn -t foobar 2 -L telnet foobar
@end example

@noindent
@code{screen} creates a shell window (in window #1) and a window with a
TELNET connection to the machine foobar (with no flow-control using the
title @samp{foobar} in window #2) and will write a logfile @samp{screenlog.2}
of the telnet session.  If you do not include any
@code{screen} commands in your @file{.screenrc} file, then @code{screen}
defaults to creating a single shell window, number zero.  When the
initialization is completed, @code{screen} switches to the last window
specified in your .screenrc file or, if none, it opens default window
#0.

@node Setenv, Shell, Screen Command, New Window
@section Setenv
@deffn Command setenv var string
(none)@*
Set the environment variable @var{var} to value @var{string}.
If only @var{var} is specified, the user will be prompted to enter a value.
If no parameters are specified, the user will be prompted for both variable
and value. The environment is inherited by all subsequently forked shells.
@end deffn

@deffn Command unsetenv var
(none)@*
Unset an environment variable.
@end deffn

@node Shell, Term, Setenv, New Window
@section Shell
@deffn Command shell command
@deffnx Command defshell command
(none)@*
Set the command to be used to create a new shell.  This overrides the
value of the environment variable @code{$SHELL}.  This is useful if
you'd like to run a tty-enhancer which is expecting to execute the
program specified in @code{$SHELL}.  If the command begins with
a @samp{-} character, the shell will be started as a login-shell.

@code{defshell} is currently a synonym to the @code{shell} command.
@end deffn

@deffn Command shelltitle title
(none)@*
Set the title for all shells created during startup or by the C-a C-c
command.  @xref{Naming Windows}, for details about what titles are.
@end deffn

@node Term, Window Types , Shell, New Window
@section Term
@deffn Command term term
(none)@*
In each window @code{screen} opens, it sets the @code{$TERM}
variable to @code{screen} by default, unless no description for
@code{screen} is installed in the local termcap or terminfo data base.
In that case it pretends that the terminal emulator is @samp{vt100}.
This won't do much harm, as @code{screen} is VT100/ANSI compatible.  The
use of the @code{term} command is discouraged for non-default purpose.
That is, one may want to specify special @code{$TERM} settings (e.g. vt100) for
the next @code{screen rlogin othermachine} command. Use the command
@code{screen -T vt100 rlogin othermachine} rather than setting
and resetting the default.
@end deffn

@node Window Types, , Term, New Window
@section Window Types
@cindex window types
Screen provides three different window types. New windows are created
with @code{screen}'s @samp{screen} command (@pxref{Screen Command}).
The first parameter to the @samp{screen} command defines which
type of window is created. The different window types are all
special cases of the normal type. They have been added in order
to allow @code{screen} to be used efficiently as a console
with 100 or more windows.
@itemize @bullet
@item
The normal window contains a shell (default, if no parameter is given)
or any other system command that could be executed from a shell.
(e.g. @samp{slogin}, etc...).

@item
If a tty (character special device) name (e.g. @samp{/dev/ttya})
is specified as the first parameter, then the window is directly
connected to this device.
This window type is similar to @samp{screen cu -l /dev/ttya}.
Read and write access is required on the device node,
an exclusive open is attempted on the node to mark the connection line
as busy.
An optional parameter is allowed consisting of a comma separated
list of flags in the notation used by @samp{stty(1)}:
@table @code
@item <baud_rate>
Usually 300, 1200, 9600 or 19200. This affects transmission as well as
receive speed.
@item cs8 or cs7
Specify the transmission of eight (or seven) bits per byte.
@item ixon or -ixon
Enables (or disables) software flow-control (CTRL-S/CTRL-Q) for sending
data.
@item ixoff or -ixoff
Enables (or disables) software flow-control for receiving data.
@item istrip or -istrip
Clear (or keep) the eight bit in each received byte.
@end table

You may want to specify as many of these options as applicable.
Unspecified options cause the terminal driver to make up the parameter
values of the connection. These values are system-dependent and may be
in defaults or values saved from a previous connection.

For tty windows, the @code{info} command shows some of the modem
control lines in the status line.
These may include @samp{RTS}, @samp{CTS}, @samp{DTR}, @samp{CD} and
more. This depends rather on on the available @code{ioctl()}'s and system
header files than on the physical capabilities of the serial board. 
The name of a logical low (inactive) signal is preceded by an 
exclamation mark (@samp{!}), otherwise the signal is logical high (active).
Unsupported but shown signals are usually shown low.
When the @code{CLOCAL} status bit is true, the whole set of modem signals is 
placed inside curly braces (@samp{@{} and @samp{@}}).
When the @code{CRTSCTS} or @code{TIOCSOFTCAR} bit is true, the signals 
@samp{CTS} or @samp{CD} are shown in parenthesis, respectively.

For tty windows, the command @code{break} causes the Data transmission
line (TxD) to go low for a specified period of time. This is expected
to be interpreted as break signal on the other side.
No data is sent and no modem control line is changed when a
@code{break} is issued.

@item
If the first parameter is @code{//telnet}, the second parameter is
expected to be a host name, and an optional third parameter may specify
a TCP port number (default decimal 23). Screen will connect to a
server listening on the remote host and use the telnet protocol to
communicate with that server.

For telnet windows, the command @code{info} shows details about
the connection in square brackets (@samp{[} and @samp{]}) at the end of
the status line.
@table @code
@item b
BINARY. The connection is in binary mode.
@item e
ECHO. Local echo is disabled.
@item c
SGA. The connection is in `character mode' (default: `line mode').
@item t
TTYPE. The terminal type has been requested by the remote host. Screen
sends the name @code{screen} unless instructed otherwise (see also the
command @samp{term}).
@item w
NAWS. The remote site is notified about window size changes.
@item f
LFLOW. The remote host will send flow control information.
(Ignored at the moment.)
@end table
Additional flags for debugging are @samp{x}, @samp{t} and @samp{n}
(XDISPLOC, TSPEED and NEWENV).

For telnet windows, the command @code{break} sends the telnet code
@code{IAC BREAK} (decimal 243) to the remote host.

@end itemize

@node Selecting, Session Management, New Window, Top
@chapter Selecting a Window

This section describes the commands for switching between windows in an
@code{screen} session.  The windows are numbered from 0 to 9, and are created
in that order by default (@pxref{New Window}).

@menu
* Next and Previous::           Forward or back one window.
* Other Window::                Switch back and forth between two windows.
* Select::                      Switch to a window (and to one after @code{kill}).
* Windowlist::                  Present a list of all windows for selection.
@end menu

@node Next and Previous, Other Window,  , Selecting
@section Moving Back and Forth
@kindex SPC
@kindex n
@kindex C-n
@deffn Command next
(@kbd{C-a @key{SPC}}, @kbd{C-a n}, @kbd{C-a C-n})@*
Switch to the next window.  This command can be used repeatedly to
cycle through the list of windows.  (On some terminals, C-@key{SPC}
generates a NUL character, so you must release the control key before
pressing space.)
@end deffn

@kindex p
@kindex C-p
@deffn Command prev
(@kbd{C-a p}, @kbd{C-a C-p})@*
Switch to the previous window (the opposite of @kbd{C-a n}).
@end deffn

@node Other Window, Select, Next and Previous, Selecting
@section Other Window
@kindex C-a
@deffn Command other
(@kbd{C-a C-a})@*
Switch to the last window displayed.  Note that this command
defaults to the command character typed twice, unless overridden.
For instance, if you use the option @samp{-e]x}, 
this command becomes @kbd{]]} (@pxref{Command Character}).
@end deffn

@node Select, Windowlist, Other Window, Selecting
@section Select
@kindex 0@dots{}9
@kindex '
@deffn Command select [n]
(@kbd{C-a @var{n}}, @kbd{C-a '})@*
Switch to the window with the number @var{n}.
If no window number is specified, you get prompted for an 
identifier. This can be a window name (title) or a number.
When a new window is established, the lowest available number
is assigned to this window.
Thus, the first window can be activated by @code{select 0}; there
can be no more than 10 windows present simultaneously (unless screen is
compiled with a higher MAXWIN setting).
There are two special arguments, @code{select -} switches to the
internal blank window and @code{select .} switches to the
current window. The latter is useful if used with screen's
@code{-X} option.

@end deffn

@node Windowlist, , Select, Selecting
@section Windowlist
@kindex "
@deffn Command windowlist [-b] [-m]
@deffnx Command windowlist string [@var{string}]
@deffnx Command windowlist title [@var{title}]
(@kbd{C-a "})@*
Display all windows in a table for visual window selection.
The desired window can be selected via the standard
movement keys (@pxref{Movement}) and activated via
the return key.  If the @code{-b} option is given, screen will
switch to the blank window before presenting the list, so
that the current window is also selectable.
The @code{-m} option changes the order of the windows, instead of
sorting by window numbers screen uses its internal most-recently-used
list.

The table format can be changed with the string and title
option, the title is displayed as table heading, while the
lines are made by using the string setting.  The default
setting is @samp{Num Name%=Flags} for the title and
@samp{%3n %t%=%f} for the lines. See the string escapes chapter
(@pxref{String Escapes}) for more codes (e.g. color settings).

@end deffn

@node Session Management, Regions, Selecting, Top
@chapter Session Management Commands

Perhaps the most useful feature of @code{screen} is the way it allows
the user to move a session between terminals, by detaching and
reattaching.  This also makes life easier for modem users who have to
deal with unexpected loss of carrier.

@menu
* Detach::                      Disconnect @code{screen} from your terminal.
* Power Detach::                Detach and log out.
* Lock::                        Lock your terminal temporarily.
* Multiuser Session::           Changing number of allowed users.
* Session Name::                Rename your session for later reattachment.
* Suspend::                     Suspend your session.
* Quit::                        Terminate your session.
@end menu

@node Detach, Power Detach,  , Session Management
@section Detach

@deffn Command autodetach state
(none)@*
Sets whether @code{screen} will automatically detach upon hangup, which
saves all your running programs until they are resumed with a
@code{screen -r} command.  When turned off, a hangup signal will
terminate @code{screen} and all the processes it contains. Autodetach is
on by default.
@end deffn

@kindex d
@kindex C-d
@deffn Command detach
(@kbd{C-a d}, @kbd{C-a C-d})@*
Detach the @code{screen} session (disconnect it from the terminal and
put it into the background).  A detached @code{screen} can be resumed by
invoking @code{screen} with the @code{-r} option (@pxref{Invoking
Screen}).
The @code{-h} option tells screen to immediately close the connection
to the terminal (@samp{hangup}).
@end deffn

@deffn Command password [crypted_pw]
(none)@*
Present a crypted password in your @file{.screenrc} file and screen will
ask for it, whenever someone attempts to resume a detached session. This
is useful, if you have privileged programs running under @code{screen}
and you want to protect your session from reattach attempts by users
that managed to assume your uid. (I.e. any superuser.)  If no crypted
password is specified, screen prompts twice a password and places its
encryption in the paste buffer.  Default is `none', which disables
password checking.
@end deffn

@node Power Detach, Lock, Detach, Session Management
@section Power Detach

@kindex D
@deffn Command pow_detach
(@kbd{C-a D D})@*
Mainly the same as @code{detach}, but also sends a HANGUP signal
to the parent process of @code{screen}.@*
@emph{Caution}: This will result in a
logout if @code{screen} was started from your login shell.
@end deffn

@deffn Command pow_detach_msg [message]
(none)@*
The @var{message} specified here is output whenever a power detach is
performed. It may be used as a replacement for a logout message or to reset 
baud rate, etc.
Without parameter, the current message is shown.
@end deffn

@node Lock, Multiuser Session, Power Detach, Session Management
@section Lock
@kindex x
@kindex C-x
@deffn Command lockscreen
(@kbd{C-a x}, @kbd{C-a C-x})@*
Call a screenlock program (@file{/local/bin/lck} or @file{/usr/bin/lock}
or a builtin, if no other is available). Screen does not accept any
command keys until this program terminates. Meanwhile processes in the
windows may continue, as the windows are in the detached state.
The screenlock program may be changed through the environment variable
@code{$LOCKPRG} (which must be set in the shell from which @code{screen}
is started) and is executed with the user's uid and gid.

Warning: When you leave other shells unlocked and have no password set
on @code{screen}, the lock is void: One could easily re-attach from an
unlocked shell. This feature should rather be called
@code{lockterminal}.
@end deffn

@node Multiuser Session, Session Name, Lock, Session Management
@section Multiuser Session
@cindex multiuser session 

These commands allow other users to gain access to one single @code{screen}
session. When attaching to a multiuser @code{screen} the sessionname is 
specified as @code{username/sessionname} to the @code{-S} command line option.
@code{Screen} must be compiled with multiuser support to enable features 
described here.

@menu
* Multiuser::                   Enable / Disable multiuser mode.
* Acladd::                      Enable a specific user.
* Aclchg::                      Change a users permissions.
* Acldel::                      Disable a specific user.
* Aclgrp::                      Grant a user permissions to other users.
* Displays::                    List all active users at their displays.
* Umask::                       Predefine access to new windows.
* Wall::                        Write a message to all users.
* Writelock::                   Grant exclusive window access.
* Su::                          Substitute user.
@end menu

@node Multiuser, Acladd,  , Multiuser Session
@subsection Multiuser
@deffn Command multiuser @var{state}
(none)@*
Switch between single-user and multi-user mode. Standard screen operation is 
single-user. In multi-user mode the commands @code{acladd}, @code{aclchg} and 
@code{acldel} can be used to enable (and disable) other users accessing this 
@code{screen}.  
@end deffn

@node Acladd, Aclchg, Multiuser, Multiuser Session
@subsection Acladd
@deffn Command acladd @var{usernames}
@deffnx Command addacl @var{usernames}
(none)@*
Enable users to fully access this screen session. @var{Usernames} can be one 
user or a comma separated list of users. This command enables to attach to
the @code{screen} session and performs the equivalent of
@code{aclchg @var{usernames} +rwx "#?"}. To add a user with restricted access,
use the @code{aclchg} command below. 
@code{Addacl} is a synonym to @code{acladd}.
Multi-user mode only.
@end deffn

@node Aclchg, Acldel, Acladd, Multiuser Session
@subsection Aclchg
@deffn Command aclchg @var{usernames permbits list}
@deffnx Command chacl @var{usernames permbits list}
(none)@*
Change permissions for a comma separated list of users. 
Permission bits are represented as @samp{r}, @samp{w} and @samp{x}. 
Prefixing @samp{+} grants the permission, @samp{-} removes it. The third 
parameter is a comma separated list of commands or windows (specified either 
by number or title). The special list @samp{#} refers to all windows, @samp{?} 
to all commands. If @var{usernames} consists of a single @samp{*}, all 
known users are affected. 
A command can be executed when the user has the @samp{x} bit for it. The user
can type input to a window when he has its @samp{w} bit set and no other
user obtains a writelock for this window. Other bits are currently ignored.
To withdraw the writelock from another user in e.g. window 2:
@samp{aclchg @var{username} -w+w 2}. To allow read-only access 
to the session: @samp{aclchg @var{username} -w "#"}. As soon as a user's name 
is known to screen, he can attach to the session and (per default) has full 
permissions for all command and windows. Execution permission for the acl 
commands, @code{at} and others should also be removed or the user may be able 
to regain write permission.
@code{Chacl} is a synonym to @code{aclchg}.
Multi-user mode only.
@end deffn

@node Acldel, Aclgrp, Aclchg, Multiuser Session
@subsection Acldel
@deffn Command acldel @var{username}
(none)@*
Remove a user from screen's access control list. If currently attached, all the
user's displays are detached from the session. He cannot attach again.
Multi-user mode only.
@end deffn

@node Aclgrp, Displays, Acldel, Multiuser Session
@subsection Aclgrp
@deffn Command aclgrp @var{username} [@var{groupname}]
(none)@*
Creates groups of users that share common access rights. The
name  of the group is the username of the group leader. Each
member of  the  group  inherits  the  permissions  that  are
granted  to the group leader. That means, if a user fails an
access check, another check is made for the group leader.
A user is removed from all groups the special value @samp{none}
is used for @var{groupname}. If the second parameter is omitted
all groups the user is in are listed.
@end deffn

@node Displays, Umask, Aclgrp, Multiuser Session
@subsection Displays
@kindex *
@deffn Command displays
(@kbd{C-a *})@*
Shows a tabular listing  of  all  currently  connected  user
front-ends  (displays).   This  is most useful for multiuser
sessions.
@end deffn

@node Umask, Wall, Displays, Multiuser Session
@subsection aclumask
@deffn Command aclumask [@var{users}]+/-@var{bits} ...
@deffnx Command umask [@var{users}]+/-@var{bits} ...
(none)@*
This specifies the access other users have to  windows  that
will  be  created  by  the caller of the command. @var{Users} may be no,
one or a comma separated list of known usernames.  If  no  users  are
specified,  a  list of all currently known users is assumed.
@var{Bits} is any  combination  of  access  control  bits  allowed
defined  with the @code{aclchg} command. The special username @samp{?}
predefines the access that  not  yet  known  users  will  be
granted  to any window initially.  The special username @samp{??}
predefines the access that not yet known users  are  granted
to any command. Rights of the special username nobody cannot
be changed (see the @code{su} command).
@code{Umask} is a synonym to @code{aclumask}.
@end deffn


@node Wall, Writelock, Umask, Multiuser Session
@subsection Wall
@deffn Command wall @var{message}
(none)@*
Write a message to all displays. The message will appear in the terminal's
status line.
@end deffn

@node Writelock, Su , Wall, Multiuser Session
@subsection Writelock
@deffn Command writelock @var{on|off|auto}
(none)@*
In addition to access control lists, not all users may be able to write to
the same window at once. Per default, writelock is in @samp{auto} mode and
grants exclusive input permission to the user who is the first to switch
to the particular window. When he leaves the window, other users may obtain
the writelock (automatically). The writelock of the current window is disabled
by the command @code{writelock off}. If the user issues the command
@code{writelock on} he keeps the exclusive write permission while switching
to other windows.
@end deffn

@deffn Command defwritelock @var{on|off|auto}
(none)@*
Sets the default writelock behavior for new windows. Initially all windows
will be created with no writelocks.
@end deffn

@node Su,  , Writelock, Multiuser Session
@subsection Su
@deffn Command su [@var{username} [@var{password} [@var{password2}]]]
(none)@*
Substitute the user of a display. The  command  prompts  for
all parameters that are omitted. If passwords are specified
as parameters, they have  to  be  specified  un-crypted.  The
first  password  is matched against the systems passwd database,
the second password  is  matched  against  the @code{screen}
password  as  set  with the commands @code{acladd} or @code{password}.
@code{Su} may be useful for the @code{screen} administrator to test
multiuser  setups.
When  the  identification  fails,  the  user has
access to the commands available for user @samp{nobody}. These are
@code{detach}, @code{license}, @code{version}, @code{help} and
@code{displays}.
@end deffn

@node Session Name, Suspend, Multiuser Session, Session Management
@section Session Name
@deffn Command sessionname [@var{name}]
(none)@*
Rename the current session. Note that for @code{screen -list} the name
shows up with the process-id prepended. If the argument @var{name} is
omitted, the name of this session is displayed.@*
@emph{Caution}: The @code{$STY}
environment variable still reflects the old name. This may result in
confusion.  The default is constructed from the tty and host names.
@end deffn

@node Suspend, Quit, Session Name, Session Management
@section Suspend
@kindex z
@kindex C-z
@deffn Command suspend
(@kbd{C-a z}, @kbd{C-a C-z})@*
Suspend @code{screen}.  The windows are in the detached state while
@code{screen} is suspended.  This feature relies on the parent shell
being able to do job control.
@end deffn

@node Quit,  , Suspend, Session Management
@section Quit
@kindex C-\
@deffn Command quit
(@kbd{C-a C-\})@*
Kill all windows and terminate @code{screen}.  Note that on VT100-style
terminals the keys @kbd{C-4} and @kbd{C-\} are identical.  So be careful
not to type @kbd{C-a C-4} when selecting window no. 4.  Use the empty
bind command (as in @code{bind "^\"}) to remove a key binding
(@pxref{Key Binding}).
@end deffn

@node Regions, Window Settings, Session Management, Top
@chapter Regions
@cindex regions
Screen has the ability to display more than one window on the
user's display. This is done by splitting the screen in regions,
which can contain different windows.

@menu
* Split::                       Split a region into two
* Focus::                       Change to the next region
* Only::                        Delete all other regions
* Remove::                      Delete the current region
* Resize::                      Grow or shrink a region
* Caption::                     Control the window's caption
* Fit::                         Resize a window to fit the region
@end menu

@node Split, Focus,  , Regions
@section Split
@kindex S
@deffn Command split
(@kbd{C-a S})@*
Split the current region into two new ones. All regions on the
display are resized to make room for the new region. The blank
window is displayed on the new region.
@end deffn

@node Focus, Only, Split, Regions
@section Focus
@kindex TAB
@deffn Command focus
(@kbd{C-a @key{Tab}})@*
Move the input focus to the next region. This is done in a cyclic
way so that the top region is selected after the bottom one. If
no subcommand is given it defaults to `down'. `up' cycles in the
opposite order, `top' and `bottom' go to the top and bottom
region respectively. Useful bindings are (j and k as in vi)
@example
bind j focus down
bind k focus up
bind t focus top
bind b focus bottom
@end example
@end deffn

@node Only, Remove, Focus, Regions
@section Only
@kindex Q
@deffn Command only
(@kbd{C-a Q})@*
Kill all regions but the current one.
@end deffn

@node Remove, Resize, Only, Regions
@section Remove
@kindex X
@deffn Command remove
(@kbd{C-a X})@*
Kill the current region. This is a no-op if there is only one region.
@end deffn

@node Resize, Caption, Remove, Regions
@section Resize
@deffn Command resize [(+/-)@var{lines}]
(none)@*
Resize the current region. The space will be removed from or added to
the region below or if there's not enough space from the region above.
@example
resize +N       increase current region height by N
resize -N       decrease current region height by N
resize  N       set current region height to N
resize  =       make all windows equally high
resize  max     maximize current region height
resize  min     minimize current region height
@end example
@end deffn

@node Caption, Fit, Resize, Regions
@section Caption
@deffn Command caption @code{always}|@code{splitonly} [string]
@deffnx Command caption @code{string} [string]
(none)@*
This command controls the display of the window captions. Normally
a caption is only used if more than one window is shown on the
display (split screen mode). But if the type is set to
@code{always}, @code{screen} shows a caption
even if only one window is displayed. The default
is @samp{splitonly}.

The second form changes the text used for the caption. You can use
all string escapes (@pxref{String Escapes}). @code{Screen} uses
a default of @samp{%3n %t}.

You can mix both forms by providing the string as an additional
argument.
@end deffn

@node Fit, , Caption, Regions
@section Fit
@kindex F
@deffn Command fit
(@kbd{C-a F})@*
Change the window size to the size of the current region. This
command is needed because screen doesn't adapt the window size
automatically if the window is displayed more than once.
@end deffn

@node Window Settings, Virtual Terminal, Regions, Top
@chapter Window Settings

These commands control the way @code{screen} treats individual windows
in a session.  @xref{Virtual Terminal}, for commands to control the
terminal emulation itself.

@menu
* Naming Windows::              Control the name of the window
* Console::                     See the host's console messages
* Kill::                        Destroy an unwanted window
* Login::                       Control @file{/etc/utmp} logging
* Mode::                        Control the file mode of the pty
* Monitor::                     Watch for activity in a window
* Windows::                     List the active windows
* Hardstatus::                  Set a window's hardstatus line
@end menu

@node Naming Windows, Console,  , Window Settings
@section Naming Windows (Titles)
@cindex title

You can customize each window's name in the window display (viewed with
the @code{windows} command (@pxref{Windows}) by setting it with
one of the title commands.  Normally the name displayed is the actual
command name of the program created in the window.  However, it is
sometimes useful to distinguish various programs of the same name or to
change the name on-the-fly to reflect the current state of the window.

The default name for all shell windows can be set with the
@code{shelltitle} command (@pxref{Shell}).  You can specify the name you
want for a window with the @samp{-t} option to the @code{screen} command
when the window is created (@pxref{Screen Command}).  To change the name after
the window has been created you can use the title-string escape-sequence
(@kbd{@key{ESC} k @var{name} @key{ESC} \}) and the @code{title} command
(C-a A).  The former can be output from an application to control the
window's name under software control, and the latter will prompt for a
name when typed.  You can also bind predefined names to keys with the
@code{title} command to set things quickly without prompting.

@menu
* Title Command::                 The @code{title} command.
* Dynamic Titles::                Make shell windows change titles dynamically.
* Title Prompts::                 Set up your shell prompt for dynamic Titles.
* Title Screenrc::                Set up Titles in your @file{.screenrc}.
@end menu

@node Title Command, Dynamic Titles,  , Naming Windows
@subsection Title Command
@kindex A
@deffn Command title [windowtitle]
(@kbd{C-a A})@*
Set the name of the current window to @var{windowtitle}. If no name is 
specified, screen prompts for one.
@end deffn

@node Dynamic Titles, Title Prompts, Title Command, Naming Windows
@subsection Dynamic Titles
@code{screen} has a shell-specific heuristic that is enabled by
setting the window's name to @var{search|name} and arranging to have a
null title escape-sequence output as a part of your prompt.  The
@var{search} portion specifies an end-of-prompt search string, while the
@var{name} portion specifies the default shell name for the window.  If
the @var{name} ends in a @samp{:} @code{screen} will add what it
believes to be the current command running in the window to the end of
the specified name (e.g. @var{name:cmd}).  Otherwise the current
command name supersedes the shell name while it is running.

Here's how it works: you must modify your shell prompt to output a null
title-escape-sequence (@key{ESC} k @key{ESC} \) as a part of your prompt.
The last part of your prompt must be the same as the string you
specified for the @var{search} portion of the title.  Once this is set
up, @code{screen} will use the title-escape-sequence to clear the previous
command name and get ready for the next command.  Then, when a newline
is received from the shell, a search is made for the end of the prompt.
If found, it will grab the first word after the matched string and use
it as the command name.  If the command name begins with @samp{!},
@samp{%}, or @samp{^}, @code{screen} will use the first word on the
following line (if found) in preference to the just-found name.  This
helps csh users get more accurate titles when using job control or
history recall commands.

@node Title Prompts, Title Screenrc, Dynamic Titles, Naming Windows
@subsection Setting up your prompt for shell titles
One thing to keep in mind when adding a null title-escape-sequence to your
prompt is that some shells (like the csh) count all the non-control
characters as part of the prompt's length.  If these invisible
characters aren't a multiple of 8 then backspacing over a tab will
result in an incorrect display.  One way to get around this is to use a
prompt like this:

@example
set prompt='@value{esc}[0000m@value{esc}k@value{esc}\% '
@end example

The escape-sequence @samp{@value{esc}[0000m} not only normalizes the
character attributes, but all the zeros round the length of the
invisible characters up to 8.

Tcsh handles escape codes in the prompt more intelligently, so you can
specify your prompt like this:

@example
set prompt="%@{\ek\e\\%@}\% "
@end example

Bash users will probably want to echo the escape sequence in the
PROMPT_COMMAND:

@example
PROMPT_COMMAND='printf "\033k\033\134"'
@end example

(I used @samp{\134} to output a @samp{\} because of a bug in v1.04).

@node Title Screenrc,  , Title Prompts, Naming Windows
@subsection Setting up shell titles in your @file{.screenrc}
Here are some .screenrc examples:

@example
screen -t top 2 nice top
@end example

Adding this line to your .screenrc would start a niced version of the
@code{top} command in window 2 named @samp{top} rather than @samp{nice}.

@example
shelltitle '> |csh'
screen 1
@end example

This file would start a shell using the given shelltitle.  The title
specified is an auto-title that would expect the prompt and the typed
command to look something like the following:

@example
/usr/joe/src/dir> trn
@end example

(it looks after the '> ' for the command name).
The window status would show the name @samp{trn} while the command was
running, and revert to @samp{csh} upon completion.

@example
bind R screen -t '% |root:' su
@end example

Having this command in your .screenrc would bind the key sequence
@kbd{C-a R} to the @code{su} command and give it an auto-title name of
@samp{root:}.  For this auto-title to work, the screen could look
something like this:

@example
% !em
emacs file.c
@end example

Here the user typed the csh history command @code{!em} which ran the
previously entered @code{emacs} command.  The window status would show
@samp{root:emacs} during the execution of the command, and revert to
simply @samp{root:} at its completion.

@example
bind o title
bind E title ""
bind u title (unknown)
@end example

The first binding doesn't have any arguments, so it would prompt you for
a title when you type @kbd{C-a o}.  The second binding would clear an
auto-titles current setting (C-a E).  The third binding would set the
current window's title to @samp{(unknown)} (C-a u).

@node Console, Kill, Naming Windows, Window Settings
@section Console
@deffn Command console [@var{state}]
(none)@*
Grabs or un-grabs the machines console output to a window. When the argument
is omitted the current state is displayed.
@emph{Note}: Only the owner of @file{/dev/console} can grab the console
output. This command is only available if the host supports the ioctl
@code{TIOCCONS}.
@end deffn

@node Kill, Login, Console, Window Settings
@section Kill

@kindex k
@kindex C-k
@deffn Command kill
(@kbd{C-a k}, @kbd{C-a C-k})@*
Kill the current window.@*
If there is an @code{exec} command running (@pxref{Exec}) then it is killed.
Otherwise the process (e.g. shell) running in the window receives a 
@code{HANGUP} condition, 
the window structure is removed and screen (your display) switches to another
window. When the last window is destroyed, @code{screen} exits.
After a kill screen switches to the previously displayed window.
@* 
@emph{Caution}: @code{emacs} users may find themselves killing their
@code{emacs} session when trying to delete the current line.  For this
reason, it is probably wise to use a different command character
(@pxref{Command Character}) or rebind @code{kill} to another key
sequence, such as @kbd{C-a K} (@pxref{Key Binding}).
@end deffn

@node Login, Mode, Kill, Window Settings
@section Login

@deffn Command deflogin state
(none)@*
Same as the @code{login} command except that the default setting for new
windows is changed.  This defaults to `on' unless otherwise specified at
compile time (@pxref{Installation}). Both commands are only present when
@code{screen} has been compiled with utmp support.
@end deffn

@kindex L
@deffn Command login [state]
(@kbd{C-a L})@*
Adds or removes the entry in @file{/etc/utmp} for the current window.
This controls whether or not the window is @dfn{logged in}.  In addition
to this toggle, it is convenient to have ``log in'' and ``log out''
keys.  For instance, @code{bind I login on} and @code{bind O 
login off} will map these keys to be @kbd{C-a I} and @kbd{C-a O}
(@pxref{Key Binding}).
@end deffn

@node Mode, Monitor, Login, Window Settings
@section Mode
@deffn Command defmode mode
(none)@*
The mode of each newly allocated pseudo-tty is set to @var{mode}.
@var{mode} is an octal number as used by chmod(1).  Defaults to 0622 for
windows which are logged in, 0600 for others (e.g. when @code{-ln} was 
specified for creation, @pxref{Screen Command}).
@end deffn

@node Monitor, Windows, Mode, Window Settings
@section Monitoring

@deffn Command activity message
(none)@*
When any activity occurs in a background window that is being monitored,
@code{screen} displays a notification in the message line.  The
notification message can be redefined by means of the @code{activity}
command.  Each occurrence of @samp{%} in @var{message} is replaced by
the number of the window in which activity has occurred, and each
occurrence of @samp{^G} is replaced by the definition for bell in your
termcap (usually an audible bell).  The default message is

@example
'Activity in window %n'
@end example

Note that monitoring is off for all windows by default, but can be altered
by use of the @code{monitor} command (@kbd{C-a M}).
@end deffn

@deffn Command defmonitor state
(none)@*
Same as the @code{monitor} command except that the default setting for
new windows is changed.  Initial setting is `off'.
@end deffn

@kindex M
@deffn Command monitor [state]
(@kbd{C-a M})@*
Toggles monitoring of the current window.  When monitoring is turned on
and the affected window is switched into the background, the activity
notification message will be displayed in the status line at the first
sign of output, and the window will also be marked with an @samp{@@} in
the window-status display (@pxref{Windows}).  Monitoring defaults to
@samp{off} for all windows.
@end deffn

@node Windows, Hardstatus, Monitor, Window Settings
@section Windows
@kindex w
@kindex C-w
@deffn Command windows
(@kbd{C-a w}, @kbd{C-a C-w})@*
Uses the message line to display a list of all the windows.  Each
window is listed by number with the name of the program running in the
window (or its title). 

The current window is marked with a @samp{*};
the previous window is marked with a @samp{-}; 
all the windows that are logged in are marked with a @samp{$} (@pxref{Login});
a background window that has received a bell is marked with a @samp{!};
a background window that is being monitored and has had activity occur is 
marked with an @samp{@@} (@pxref{Monitor});
a window which has output logging turned on is marked with @samp{(L)};
windows occupied by other users are marked with @samp{&}
or @samp{&&} if the window is shared by other users;
windows in the zombie state are marked with @samp{Z}. 

If this list is too long to fit on the terminal's status line only the
portion around the current window is displayed.
@end deffn

@node Hardstatus, , Windows, Window Settings
@section Hardstatus

@code{Screen} maintains a hardstatus line for every window. If a window
gets selected, the display's hardstatus will be updated to match
the window's hardstatus line.
The hardstatus line can be changed with the ANSI Application
Program Command (APC): @samp{ESC_<string>ESC\}. As a convenience
for xterm users the sequence @samp{ESC]0..2;<string>^G} is
also accepted.

@deffn Command defhstatus [status]
(none)@*
The hardstatus line that all new windows will get is set to
@var{status}.
This command is useful to make the hardstatus of every window
display the window number or title or the like.  @var{status}
may contain the same directives as in the window messages, but
the directive escape character is @samp{^E} (octal 005) instead
of @samp{%}.  This was done to make a misinterpretation of program
generated hardstatus lines impossible.
If the parameter @var{status}
is omitted, the current default string is displayed.
Per default the hardstatus line of new windows is empty.
@end deffn

@deffn Command hstatus status
(none)@*
Changes the current window's hardstatus line to @var{status}.
@end deffn

@node Virtual Terminal, Copy and Paste, Window Settings, Top
@chapter Virtual Terminal

Each window in a @code{screen} session emulates a VT100 terminal, with
some extra functions added. The VT100 emulator is hard-coded, no other
terminal types can be emulated. 
The commands described here modify the terminal emulation.

@menu
* Control Sequences::           Details of the internal VT100 emulation.
* Input Translation::           How keystrokes are remapped.
* Digraph::                     Entering digraph sequences.
* Bell::                        Getting your attention.
* Clear::                       Clear the window display.
* Info::                        Terminal emulation statistics.
* Redisplay::                   When the display gets confusing.
* Wrap::                        Automatic margins.
* Reset::                       Recovering from ill-behaved applications.
* Window Size::                 Changing the size of your terminal.
* Character Processing::        Change the effect of special characters.
@end menu

@node Control Sequences, Input Translation,  , Virtual Terminal
@section Control Sequences
@cindex control sequences
The following is a list of control sequences recognized by
@code{screen}.  @samp{(V)} and @samp{(A)} indicate VT100-specific and
ANSI- or ISO-specific functions, respectively.

@example
ESC E                           Next Line
ESC D                           Index
ESC M                           Reverse Index
ESC H                           Horizontal Tab Set
ESC Z                           Send VT100 Identification String
ESC 7                   (V)     Save Cursor and Attributes
ESC 8                   (V)     Restore Cursor and Attributes
ESC [s                  (A)     Save Cursor and Attributes
ESC [u                  (A)     Restore Cursor and Attributes
ESC c                           Reset to Initial State
ESC g                           Visual Bell
ESC Pn p                        Cursor Visibility (97801)
    Pn = 6                      Invisible
         7                      Visible
ESC =                   (V)     Application Keypad Mode
ESC >                   (V)     Numeric Keypad Mode
ESC # 8                 (V)     Fill Screen with E's
ESC \                   (A)     String Terminator
ESC ^                   (A)     Privacy Message String (Message Line)
ESC !                           Global Message String (Message Line)
ESC k                           Title Definition String
ESC P                   (A)     Device Control String
                                Outputs a string directly to the host
                                terminal without interpretation.
ESC _                   (A)     Application Program Command (Hardstatus)
ESC ] 0 ; string ^G     (A)     Operating System Command (Hardstatus, xterm
                                title hack)
ESC ] 83 ; cmd ^G       (A)     Execute screen command. This only works if
                                multi-user support is compiled into screen.
                                The pseudo-user ":window:" is used to check
                                the access control list. Use "addacl :window:
                                -rwx #?" to create a user with no rights and
                                allow only the needed commands.
Control-N               (A)     Lock Shift G1 (SO)
Control-O               (A)     Lock Shift G0 (SI)
ESC n                   (A)     Lock Shift G2
ESC o                   (A)     Lock Shift G3
ESC N                   (A)     Single Shift G2
ESC O                   (A)     Single Shift G3
ESC ( Pcs               (A)     Designate character set as G0
ESC ) Pcs               (A)     Designate character set as G1
ESC * Pcs               (A)     Designate character set as G2
ESC + Pcs               (A)     Designate character set as G3
ESC [ Pn ; Pn H                 Direct Cursor Addressing
ESC [ Pn ; Pn f                 same as above
ESC [ Pn J                      Erase in Display
      Pn = None or 0            From Cursor to End of Screen
           1                    From Beginning of Screen to Cursor
           2                    Entire Screen
ESC [ Pn K                      Erase in Line
      Pn = None or 0            From Cursor to End of Line
           1                    From Beginning of Line to Cursor
           2                    Entire Line
ESC [ Pn X                      Erase character
ESC [ Pn A                      Cursor Up
ESC [ Pn B                      Cursor Down
ESC [ Pn C                      Cursor Right
ESC [ Pn D                      Cursor Left
ESC [ Pn E                      Cursor next line
ESC [ Pn F                      Cursor previous line
ESC [ Pn G                      Cursor horizontal position
ESC [ Pn `                      same as above
ESC [ Pn d                      Cursor vertical position
ESC [ Ps ;...; Ps m             Select Graphic Rendition
      Ps = None or 0            Default Rendition
           1                    Bold
           2            (A)     Faint
           3            (A)     @i{Standout} Mode (ANSI: Italicized)
           4                    Underlined
           5                    Blinking
           7                    Negative Image
           22           (A)     Normal Intensity
           23           (A)     @i{Standout} Mode off (ANSI: Italicized off)
           24           (A)     Not Underlined
           25           (A)     Not Blinking
           27           (A)     Positive Image
           30           (A)     Foreground Black
           31           (A)     Foreground Red
           32           (A)     Foreground Green
           33           (A)     Foreground Yellow
           34           (A)     Foreground Blue
           35           (A)     Foreground Magenta
           36           (A)     Foreground Cyan
           37           (A)     Foreground White
           39           (A)     Foreground Default
           40           (A)     Background Black
           ...                  ...
           49           (A)     Background Default
ESC [ Pn g                      Tab Clear
      Pn = None or 0            Clear Tab at Current Position
           3                    Clear All Tabs
ESC [ Pn ; Pn r         (V)     Set Scrolling Region
ESC [ Pn I              (A)     Horizontal Tab
ESC [ Pn Z              (A)     Backward Tab
ESC [ Pn L              (A)     Insert Line
ESC [ Pn M              (A)     Delete Line
ESC [ Pn @@              (A)     Insert Character
ESC [ Pn P              (A)     Delete Character
ESC [ Pn S                      Scroll Scrolling Region Up
ESC [ Pn T                      Scroll Scrolling Region Down
ESC [ Pn ^                      same as above
ESC [ Ps ;...; Ps h             Set Mode
ESC [ Ps ;...; Ps l             Reset Mode
      Ps = 4            (A)     Insert Mode
           20           (A)     @samp{Automatic Linefeed} Mode.
           34                   Normal Cursor Visibility
           ?1           (V)     Application Cursor Keys
           ?3           (V)     Change Terminal Width to 132 columns
           ?5           (V)     Reverse Video
           ?6           (V)     @samp{Origin} Mode
           ?7           (V)     @samp{Wrap} Mode
           ?9                   X10 mouse tracking
           ?25          (V)     Visible Cursor
           ?47                  Alternate Screen (old xterm code)
           ?1000        (V)     VT200 mouse tracking
           ?1047                Alternate Screen (new xterm code)
           ?1049                Alternate Screen (new xterm code)
ESC [ 5 i               (A)     Start relay to printer (ANSI Media Copy)
ESC [ 4 i               (A)     Stop relay to printer (ANSI Media Copy)
ESC [ 8 ; Ph ; Pw t             Resize the window to @samp{Ph} lines and
                                @samp{Pw} columns (SunView special)
ESC [ c                         Send VT100 Identification String
ESC [ x                 (V)     Send Terminal Parameter Report
ESC [ > c                       Send Secondary Device Attributes String
ESC [ 6 n                       Send Cursor Position Report

@end example


@node Input Translation, Digraph, Control Sequences, Virtual Terminal
@section Input Translation
@cindex input translation
In order to do a full VT100 emulation @code{screen} has to detect
that a sequence of characters in the input stream was generated
by a keypress on the user's keyboard and insert the VT100
style escape sequence. @code{Screen} has a very flexible way of doing
this by making it possible to map arbitrary commands on arbitrary
sequences of characters. For standard VT100 emulation the command
will always insert a string in the input buffer of the window
(see also command @code{stuff}, @pxref{Paste}).
Because the sequences generated by a keypress can
change after a reattach from a different terminal type, it is
possible to bind commands to the termcap name of the keys.
@code{Screen} will insert the correct binding after each
reattach. See @ref{Bindkey} for further details on the syntax and examples.

Here is the table of the default key bindings. (A) means that the
command is executed if the keyboard is switched into application
mode.
@example

Key name        Termcap name    Command
-----------------------------------------------------
Cursor up            ku         stuff \033[A
                                stuff \033OA      (A)
Cursor down          kd         stuff \033[B
                                stuff \033OB      (A)
Cursor right         kr         stuff \033[C
                                stuff \033OC      (A)
Cursor left          kl         stuff \033[D
                                stuff \033OD      (A)
Function key 0       k0         stuff \033[10~
Function key 1       k1         stuff \033OP
Function key 2       k2         stuff \033OQ
Function key 3       k3         stuff \033OR
Function key 4       k4         stuff \033OS
Function key 5       k5         stuff \033[15~
Function key 6       k6         stuff \033[17~
Function key 7       k7         stuff \033[18~
Function key 8       k8         stuff \033[19~
Function key 9       k9         stuff \033[20~
Function key 10      k;         stuff \033[21~
Function key 11      F1         stuff \033[23~
Function key 12      F2         stuff \033[24~
Home                 kh         stuff \033[1~
End                  kH         stuff \033[4~
Insert               kI         stuff \033[2~
Delete               kD         stuff \033[3~
Page up              kP         stuff \033[5~
Page down            kN         stuff \033[6~
Keypad 0             f0         stuff 0
                                stuff \033Op      (A)
Keypad 1             f1         stuff 1
                                stuff \033Oq      (A)
Keypad 2             f2         stuff 2
                                stuff \033Or      (A)
Keypad 3             f3         stuff 3
                                stuff \033Os      (A)
Keypad 4             f4         stuff 4
                                stuff \033Ot      (A)
Keypad 5             f5         stuff 5
                                stuff \033Ou      (A)
Keypad 6             f6         stuff 6
                                stuff \033Ov      (A)
Keypad 7             f7         stuff 7
                                stuff \033Ow      (A)
Keypad 8             f8         stuff 8
                                stuff \033Ox      (A)
Keypad 9             f9         stuff 9
                                stuff \033Oy      (A)
Keypad +             f+         stuff +
                                stuff \033Ok      (A)
Keypad -             f-         stuff -
                                stuff \033Om      (A)
Keypad *             f*         stuff *
                                stuff \033Oj      (A)
Keypad /             f/         stuff /
                                stuff \033Oo      (A)
Keypad =             fq         stuff =
                                stuff \033OX      (A)
Keypad .             f.         stuff .
                                stuff \033On      (A)
Keypad ,             f,         stuff ,
                                stuff \033Ol      (A)
Keypad enter         fe         stuff \015
                                stuff \033OM      (A)
@end example

@node Digraph, Bell, Input Translation, Virtual Terminal
@section Digraph

@kindex C-v
@deffn Command digraph [preset]
(none)@*
This command prompts the user for a digraph sequence. The next
two characters typed are looked up in a builtin table and the
resulting character is inserted in the input stream. For example,
if the user enters @samp{a"}, an a-umlaut will be inserted. If the
first character entered is a 0 (zero), @code{screen}
will treat the following characters (up to three) as an octal
number instead.  The optional argument @var{preset}
is treated as user input, thus one can create an "umlaut" key.
For example the command @samp{bindkey ^K digraph '"'} enables the user
to generate an a-umlaut by typing @samp{CTRL-K a}.
@end deffn

@node Bell, Clear, Digraph, Virtual Terminal
@section Bell

@deffn Command bell_msg [message]
(none)@*
When a bell character is sent to a background window, @code{screen}
displays a notification in the message line.  The notification message
can be re-defined by this command.  Each occurrence
of @samp{%} in @var{message} is replaced by the number of the window to
which a bell has been sent, and each occurrence of @samp{^G} is replaced
by the definition for bell in your termcap (usually an audible bell).
The default message is

@example
'Bell in window %n'
@end example

An empty message can be supplied to the @code{bell_msg} command to suppress
output of a message line (@code{bell_msg ""}).
Without parameter, the current message is shown.
@end deffn

@kindex C-g
@deffn Command vbell [state]
(@kbd{C-a C-g})@*
Sets or toggles the visual bell setting for the current window. If 
@code{vbell} is switched to @samp{on}, but your
terminal does not support a visual bell, the visual bell message is
displayed in the status line when the bell character is received. 
Visual bell support of a terminal is 
defined by the termcap variable @code{vb}. @xref{Bell, , Visual Bell, 
termcap, The Termcap Manual}, for more information on visual bells. 
The equivalent terminfo capability is @code{flash}.

Per  default, @code{vbell} is @samp{off}, thus the audible bell is used.
@end deffn

@deffn Command vbell_msg [message]
(none)@*
Sets the visual bell message. @var{Message} is printed to the status
line if the window receives a bell character (^G), @code{vbell} is
set to @samp{on} and the terminal does not support a visual bell.
The default message is @samp{Wuff, Wuff!!}.
Without parameter, the current message is shown.
@end deffn

@deffn Command vbellwait sec
(none)@*
Define a delay in seconds after each display of @code{screen} 's visual
bell message. The default is 1 second.
@end deffn

@node Clear, Info, Bell, Virtual Terminal
@section Clear
@kindex C
@deffn Command clear
(@kbd{C-a C})@*
Clears the screen and saves its contents to the scrollback buffer.
@end deffn

@node Info, Redisplay, Clear, Virtual Terminal
@section Info
@kindex i
@kindex C-i
@deffn Command info
(@kbd{C-a i}, @kbd{C-a C-i})@*
Uses the message line to display some information about the current
window: the cursor position in the form @samp{(@var{column},@var{row})}
starting with @samp{(1,1)}, the terminal width and height plus the size
of the scrollback buffer in lines, like in @samp{(80,24)+50}, 
the current state of window XON/XOFF flow control is shown like this
(@pxref{Flow Control}):
@example
  +flow     automatic flow control, currently on.
  -flow     automatic flow control, currently off.
  +(+)flow  flow control enabled. Agrees with automatic control.
  -(+)flow  flow control disabled. Disagrees with automatic control.
  +(-)flow  flow control enabled. Disagrees with automatic control.
  -(-)flow  flow control disabled. Agrees with automatic control.
@end example

The current line wrap setting (@samp{+wrap} indicates enabled, @samp{-wrap}
not) is also shown. The flags @samp{ins}, @samp{org}, @samp{app}, @samp{log},
@samp{mon} and @samp{nored} are displayed when the window is in insert mode,
origin mode, application-keypad mode, has output logging,
activity monitoring or partial redraw enabled.

The currently active 
character set (@samp{G0}, @samp{G1}, @samp{G2}, or @samp{G3}), and in
square brackets the terminal character sets that are currently
designated as @samp{G0} through @samp{G3}.  
If the window is in UTF-8 mode, the string @samp{UTF-8} is shown instead.
Additional modes depending on the type of the window are displayed at
the end of the status line (@pxref{Window Types}).

If the state machine of the terminal emulator is in a non-default state,
the info line is started with a string identifying the current state.

For system information use @code{time}.
@end deffn

@deffn Command dinfo
(none)@*
Show what screen thinks about your terminal. Useful if you want to know
why features like color or the alternate charset don't work.
@end deffn

@node Redisplay, Wrap, Info, Virtual Terminal
@section Redisplay

@deffn Command allpartial state
(none)@*
If set to on, only the current cursor line is refreshed on window change.
This affects all windows and is useful for slow terminal lines. The 
previous setting of full/partial refresh for each window is restored
with @code{allpartial off}. This is a global flag that immediately takes effect
on all windows overriding the @code{partial} settings. It does not change the 
default redraw behavior of newly created windows. 
@end deffn

@deffn Command altscreen state
(none)@*
If set to on, "alternate screen" support is enabled in virtual terminals,
just like in xterm.  Initial setting is @samp{off}.
@end deffn

@deffn Command partial state
(none)@*
Defines whether the display should be refreshed (as with
@code{redisplay}) after switching to the current window. This command
only affects the current window.  To immediately affect all windows use the
@code{allpartial} command.  Default is @samp{off}, of course.  This default is 
fixed, as there is currently no @code{defpartial} command. 
@end deffn

@kindex l
@kindex C-l
@deffn Command redisplay
(@kbd{C-a l}, @kbd{C-a C-l})@*
Redisplay the current window.  Needed to get a full redisplay in
partial redraw mode.
@end deffn

@node Wrap, Reset, Redisplay, Virtual Terminal
@section Wrap

@kindex r
@kindex C-r
@deffn Command wrap state
(@kbd{C-a r}, @kbd{C-a C-r}) @*
Sets the line-wrap setting for the current window.  When line-wrap is
on, the second consecutive printable character output at the last column
of a line will wrap to the start of the following line.  As an added
feature, backspace (^H) will also wrap through the left margin to the
previous line.  Default is @samp{on}.
@end deffn

@deffn Command defwrap state
(none) @*
Same as the @code{wrap} command except that the default setting for new 
windows is changed. Initially line-wrap is on and can be toggled with the 
@code{wrap} command (@kbd{C-a r}) or by means of "C-a : wrap on|off".
@end deffn

@node Reset, Window Size, Wrap, Virtual Terminal
@section Reset
@kindex Z
@deffn Command reset
(@kbd{C-a Z})@*
Reset the virtual terminal to its ``power-on'' values. Useful when strange
settings (like scroll regions or graphics character set) are left over from
an application.
@end deffn

@node Window Size, Character Processing, Reset, Virtual Terminal
@section Window Size
@kindex W
@deffn Command width [@code{-w}|@code{-d}] [cols [lines]]
(@kbd{C-a W})@*
Toggle the window width between 80 and 132 columns, or set it to
@var{cols} columns if an argument is specified.  This requires a
capable terminal and the termcap entries @samp{Z0} and @samp{Z1}.  See
the @code{termcap} command (@pxref{Termcap}), for more information.
You can also specify a height if you want to
change  both  values.  The @code{-w} option tells screen to leave
the display size unchanged and just set the  window  size,
@code{-d} vice versa.
@end deffn

@deffn Command height [@code{-w}|@code{-d}] [lines [cols]]
(none)@*
Set the display height to a specified number of lines. When no
argument is given it toggles between 24 and 42 lines display.
@end deffn

@node Character Processing, ,Window Size, Virtual Terminal
@section Character Processing

@deffn Command c1 [state]
(none)@*
Change c1 code processing. @samp{c1 on} tells screen to treat
the input characters between 128 and 159 as control functions.
Such an 8-bit code is normally the same as ESC followed by the 
corresponding 7-bit code. The default setting is to process c1 
codes and can be changed with the @samp{defc1} command.
Users with fonts that have usable characters in the 
c1 positions may want to turn this off.

@end deffn
@deffn Command gr [state]
(none)@*
Turn GR charset switching on/off. Whenever screen sees an input
char with an 8th bit set, it will use the charset stored in the
GR slot and print the character with the 8th bit stripped. The
default (see also @samp{defgr}) is not to process GR switching because
otherwise the ISO88591 charset would not work.
@end deffn

@deffn Command bce [state]
(none)@*
Change background-color-erase setting. If @samp{bce} is set to
on, all characters cleared by an erase/insert/scroll/clear
operation will be displayed in the current background color.
Otherwise the default background color is used.
@end deffn

@deffn Command encoding enc [denc]
(none)@*
Tell screen how to interpret the input/output. The first argument
sets the encoding of the current window.
Each window can emulate a different encoding. The optional second
parameter overwrites the encoding of the connected terminal.
It should never be needed as screen uses the locale setting to detect
the encoding.
There is also a way to select a terminal encoding depending on
the terminal type by using the @samp{KJ} termcap entry. @xref{Special Capabilities}.

Supported encodings are
@code{eucJP}, @code{SJIS}, @code{eucKR},
@code{eucCN}, @code{Big5}, @code{GBK}, @code{KOI8-R}, @code{CP1251},
@code{UTF-8}, @code{ISO8859-2}, @code{ISO8859-3},
@code{ISO8859-4}, @code{ISO8859-5}, @code{ISO8859-6},
@code{ISO8859-7}, @code{ISO8859-8}, @code{ISO8859-9},
@code{ISO8859-10}, @code{ISO8859-15}, @code{jis}.

See also @samp{defencoding}, which changes the default setting of a new
window.
@end deffn

@deffn Command charset set
(none)@*
Change the current character set slot designation and charset
mapping.  The first four character of @var{set}
are treated as charset designators while the fifth and sixth
character must be in range @samp{0} to @samp{3} and set the GL/GR
charset mapping. On every position a @samp{.} may be used to indicate
that the corresponding charset/mapping should not be changed
(@var{set} is padded to six characters internally by appending
@samp{.} chars). New windows have @samp{BBBB02} as default
charset, unless a @samp{encoding} command is active.

The current setting can be viewed with the @ref{Info} command.
@end deffn

@deffn Command utf8 [state [dstate]]
(none)@*
Change the encoding used in the current window. If utf8 is enabled, the
strings sent to the window will be UTF-8 encoded and vice versa.
Omitting the
parameter toggles the setting. If a second parameter is given, the
display's
encoding is also changed (this should rather be done with screen's
@samp{-U} option).
See also @samp{defutf8}, which changes the default setting of a new
window.
@end deffn

@deffn Command defc1 state
(none)@*
Same as the @samp{c1} command except that the default setting for
new windows is changed. Initial setting is @samp{on}.
@end deffn

@deffn Command defgr state
(none)@*
Same as the @samp{gr} command except that the default setting for
new windows is changed. Initial setting is @samp{off}.
@end deffn

@deffn Command defbce state
(none)@*
Same as the @samp{bce} command except that the default setting for
new windows is changed. Initial setting is @samp{off}.
@end deffn

@deffn Command defencoding enc
(none)@*
Same as the @samp{encoding} command except that the default setting for
new windows is changed. Initial setting is the encoding taken from the
terminal.
@end deffn

@deffn Command defcharset [set]
Like the @samp{charset} command except that the default setting for
new windows is changed. Shows current default if called without
argument.
@end deffn

@deffn Command defutf8 state
(none)@*
Same as the @samp{utf8} command except that the default setting for new
windows is changed. Initial setting is @code{on} if screen was started
with @samp{-U}, otherwise @code{off}.
@end deffn

@node Copy and Paste, Subprocess Execution, Virtual Terminal, Top
@chapter Copy and Paste
@cindex copy and paste

For those confined to a hardware terminal, these commands provide a cut
and paste facility more powerful than those provided by most windowing
systems.

@menu
* Copy::                        Copy from scrollback to buffer
* Paste::                       Paste from buffer into window
* Registers::                   Longer-term storage
* Screen Exchange::             Sharing data between screen users
* History::                     Recalling previous input
@end menu

@node Copy, Paste,  , Copy and Paste
@section Copying
@cindex marking
@cindex scrollback
@kindex [
@kindex C-[
@kindex ESC
@deffn Command copy
(@kbd{C-a [}, @kbd{C-a C-[}, @kbd{C-a @key{ESC}})@*
Enter copy/scrollback mode. This allows you to copy text from the
current window and its history into the paste buffer. In this mode a
@code{vi}-like full screen editor is active, with controls as
outlined below.
@end deffn

@menu
* Line Termination::            End copied lines with CR/LF
* Scrollback::                  Set the size of the scrollback buffer
* Copy Mode Keys::              Remap keys in copy mode
* Movement::                    Move around in the scrollback buffer
* Marking::                     Select the text you want
* Repeat count::                Repeat a command
* Searching::                   Find the text you want
* Specials::                    Other random keys
@end menu

@node Line Termination, Scrollback,  , Copy
@subsection CR/LF
@deffn Command crlf [state]
(none)@*
This affects the copying of text regions with the @kbd{C-a [} command.
If it is set to @samp{on}, lines will be separated by the two character
sequence @samp{CR}/@samp{LF}.  Otherwise only @samp{LF} is used.
@code{crlf} is off by default.
When no parameter is given, the state is toggled.
@end deffn

@node Scrollback, Copy Mode Keys, Line Termination, Copy
@subsection Scrollback
@deffn Command defscrollback num
(none)@*
Same as the @code{scrollback} command except that the default setting
for new windows is changed.  Defaults to 100.
@end deffn

@deffn Command scrollback num
(none)@*
Set the size of the scrollback buffer for the current window to
@var{num} lines.  The default scrollback is 100 lines.  Use @kbd{C-a i}
to view the current setting.
@end deffn

@deffn Command compacthist [state]
(none)@*
This tells screen whether to suppress trailing blank lines when
scrolling up text into the history buffer. Turn compacting @samp{on}
to hold more useful lines in your scrollback buffer.
@end deffn

@node Copy Mode Keys, Movement, Scrollback, Copy
@subsection markkeys
@deffn Command markkeys string
(none)@*
This is a method of changing the keymap used for copy/history mode.  The
string is made up of @var{oldchar}=@var{newchar} pairs which are
separated by @samp{:}. Example: The command @code{markkeys
h=^B:l=^F:$=^E} would set some keys to be more familiar to @code{emacs}
users.
If your terminal sends characters, that cause you to abort copy mode,
then this command may help by binding these characters to do nothing.
The no-op character is `@@' and is used like this: @code{markkeys @@=L=H}
if you do not want to use the `H' or `L' commands any longer. 
As shown in this example, multiple keys can be assigned to one function
in a single statement.
@end deffn

@node Movement, Marking, Copy Mode Keys, Copy
@subsection Movement Keys

@noindent
@kbd{h}, @kbd{j}, @kbd{k}, @kbd{l} move the cursor line by line or
column by column.

@noindent
@kbd{0}, @kbd{^} and @kbd{$} move to the leftmost column or to the first
or last non-whitespace character on the line.

@noindent
@kbd{H}, @kbd{M} and @kbd{L} move the cursor to the leftmost column
of the top, center or bottom line of the window. 

@noindent
@kbd{+} and @kbd{-} move the cursor to the leftmost column of the next
or previous line.

@noindent
@kbd{G} moves to the specified absolute line (default: end of buffer).
 
@noindent
@kbd{|} moves to the specified absolute column.

@noindent
@kbd{w}, @kbd{b}, @kbd{e} move the cursor word by word.
 
@noindent
@kbd{B}, @kbd{E} move the cursor WORD by WORD (as in vi).

@noindent
@kbd{C-u} and @kbd{C-d} scroll the display up/down by the specified
amount of lines while preserving the cursor position. (Default: half
screenful).

@noindent
@kbd{C-b} and @kbd{C-f} move the cursor up/down a full screen.

@noindent
@kbd{g} moves to the beginning of the buffer.

@noindent
@kbd{%} jumps to the specified percentage of the buffer.

Note that Emacs-style movement keys can be specified by a .screenrc
command. (@code{markkeys "h=^B:l=^F:$=^E"}) There is no simple method for
a full emacs-style keymap, however, as this involves multi-character codes.

@node Marking, Repeat count, Movement, Copy
@subsection Marking

The copy range is specified by setting two marks. The text between these
marks will be highlighted. Press @kbd{space} to set the first or second
mark respectively.

@noindent
@kbd{Y} and @kbd{y} can be used to mark one whole line or to mark from 
start of line.

@noindent
@kbd{W} marks exactly one word. 
 
@node Repeat count, Searching, Marking, Copy
@subsection Repeat Count

Any command in copy mode can be prefixed with a number (by pressing
digits @kbd{0@dots{}9}) which is taken as a repeat count. Example:
@kbd{C-a C-[ H 10 j 5 Y} will copy lines 11 to 15 into the paste buffer.

@node Searching, Specials, Repeat count, Copy
@subsection Searching

@noindent
@kbd{/} @code{vi}-like search forward.

@noindent
@kbd{?} @code{vi}-like search backward.

@noindent
@kbd{C-a s} @code{emacs} style incremental search forward.

@noindent
@kbd{C-r} @code{emacs} style reverse i-search.

@deffn Command ignorecase [state]
(none)@*
Tell screen to ignore the case of characters in searches. Default is
@code{off}.
@end deffn

@node Specials,  , Searching, Copy
@subsection Specials

There are, however, some keys that act differently here from in
@code{vi}.  @code{Vi} does not allow to yank rectangular blocks of text,
but @code{screen} does. Press

@noindent
@kbd{c} or @kbd{C} to set the left or right margin respectively. If no
repeat count is given, both default to the current cursor position.@*
Example: Try this on a rather full text screen: 
@kbd{C-a [ M 20 l SPACE c 10 l 5 j C SPACE}.

@noindent
This moves one to the middle line of the screen, moves in 20 columns left,
marks the beginning of the paste buffer, sets the left column, moves 5 columns
down, sets the right column, and then marks the end of
the paste buffer. Now try:@*
@kbd{C-a [ M 20 l SPACE 10 l 5 j SPACE}

@noindent
and notice the difference in the amount of text copied.

@noindent
@kbd{J} joins lines. It toggles between 4 modes: lines separated by a
newline character (012), lines glued seamless, lines separated by a single
space or comma separated lines. Note that you can prepend the newline
character with a carriage return character, by issuing a @code{set crlf
on}.

@noindent
@kbd{v} is for all the @code{vi} users who use @code{:set numbers} - it
toggles the left margin between column 9 and 1.

@noindent
@kbd{a} before the final space key turns on append mode. Thus
the contents of the paste buffer will not be overwritten, but appended to.

@noindent
@kbd{A} turns on append mode and sets a (second) mark.

@noindent
@kbd{>} sets the (second) mark and writes the contents of the paste buffer
to the screen-exchange file (@file{/tmp/screen-exchange} per default)
once copy-mode is finished.  @xref{Screen Exchange}.@*
This example demonstrates how to dump the
whole scrollback buffer to that file: @*@kbd{C-a [ g SPACE G $ >}.

@noindent
@kbd{C-g} gives information about the current line and column.

@noindent
@kbd{x} exchanges the first mark and the current cursor position. You
can use this to adjust an already placed mark.

@noindent
@kbd{@@} does nothing.  Absolutely nothing.  Does not even exit copy
mode.

@noindent
All keys not described here exit copy mode.

@node Paste, Registers, Copy, Copy and Paste
@section Paste

@kindex ]
@kindex C-]
@deffn Command paste [registers [destination]]
(@kbd{C-a ]}, @kbd{C-a C-]})@*
Write the (concatenated) contents of the specified registers to the stdin 
stream of the current window.  The register @samp{.} is treated as the
paste buffer. If no parameter is specified the user is prompted to enter a 
single register. The paste buffer can be filled with the 
@code{copy}, @code{history} and @code{readbuf} commands.
Other registers can be filled with the @code{register}, @code{readreg} and
@code{paste} commands.
If @code{paste} is called with a second argument, the contents of the specified
registers is pasted into the named destination register rather than
the window. If @samp{.} is used as the second argument, the display's paste 
buffer is the destination.
Note, that @code{paste} uses a wide variety of resources: Usually both, a 
current window and a current display are required. But whenever a second
argument is specified no current window is needed. When the source specification
only contains registers (not the paste buffer) then there need not be a current
display (terminal attached), as the registers are a global resource. The
paste buffer exists once for every user.
@end deffn

@deffn Command stuff string
(none)@*
Stuff the string @var{string} in the input buffer of the current window.
This is like the @code{paste} command, but with much less overhead.
You cannot paste large buffers with the @code{stuff} command. It is most
useful for key bindings. @xref{Bindkey}.
@end deffn

@deffn Command pastefont [state]
Tell screen to include font information in the paste buffer. The
default is not to do so. This command is especially useful for
multi character fonts like kanji.
@end deffn

@deffn Command slowpaste msec
@deffnx Command defslowpaste msec
(none)@*
Define the speed text is inserted in the current window by the @code{paste} 
command. If the slowpaste value is nonzero text is written character by 
character.
@code{screen} will pause for @var{msec} milliseconds after each write
to allow the application to process the input. only use @code{slowpaste} if 
your underlying system exposes flow control problems while pasting large 
amounts of text. 
@code{defslowpaste} specifies the default for new windows.
@end deffn

@deffn Command readreg [-e encoding] [register [filename]]
(none)@*
Does one of two things, dependent on number of arguments: with zero or one
arguments it it duplicates the paste buffer contents into the register specified
or entered at the prompt. With two arguments it reads the contents of the named
file into the register, just as @code{readbuf} reads the screen-exchange file
into the paste buffer.
You can tell screen the encoding of the file via the @code{-e} option.
The following example will paste the system's password file into
the screen window (using register p, where a copy remains):

@example
C-a : readreg p /etc/passwd
C-a : paste p
@end example
@end deffn

@node Registers, Screen Exchange, Paste, Copy and Paste
@section Registers

@deffn Command copy_reg [key]
(none)@*
Removed. Use @code{readreg} instead.
@end deffn

@deffn Command ins_reg [key]
(none)@*
Removed. Use @code{paste} instead.
@end deffn

@deffn Command process [key]
(none)@*
Stuff the contents of the specified register into the @code{screen}
input queue. If no argument is given you are prompted for a
register name. The text is parsed as if it had been typed in from the user's
keyboard. This command can be used to bind multiple actions to a single key.
@end deffn

@deffn Command register [-e encoding] key string
(none)@*
Save the specified @var{string} to the register @var{key}.
The encoding of the string can be specified via the @code{-e} option.
@end deffn

@node Screen Exchange, History, Registers, Copy and Paste
@section Screen Exchange

@deffn Command bufferfile [@var{exchange-file}]
(none)@*
Change the filename used for reading and writing with the paste buffer.
If the @var{exchange-file} parameter is omitted, @code{screen} reverts
to the default of @file{/tmp/screen-exchange}.  The following example
will paste the system's password file into the screen window (using the 
paste buffer, where a copy remains):

@example
C-a : bufferfile /etc/passwd
C-a < C-a ]
C-a : bufferfile
@end example
@end deffn

@kindex <
@deffn Command readbuf [-e @var{encoding}] [@var{filename}]
(@kbd{C-a <})@*
Reads the contents of the specified file into the paste buffer.
You can tell screen the encoding of the file via the @code{-e} option.
If no file is specified, the screen-exchange filename is used.
@end deffn

@kindex =
@deffn Command removebuf
(@kbd{C-a =})@*
Unlinks the screen-exchange file.
@end deffn

@kindex >
@deffn Command writebuf [-e @var{encoding}] [@var{filename}]
(@kbd{C-a >})@*
Writes the contents of the paste buffer to the specified file, or the
public accessible screen-exchange file if no filename is given.
This is thought of as a primitive means of
communication between @code{screen} users on the same host.
If an encoding is specified the paste buffer is recoded on the fly to
match the encoding.
See also
@kbd{C-a @key{ESC}} (@pxref{Copy}).
@end deffn

@node History,  , Screen Exchange, Copy and Paste
@section History

@kindex @{
@deffn Command history
(@kbd{C-a @{})@*
Usually users work with a shell that allows easy access to previous
commands.  For example, @code{csh} has the command @code{!!} to repeat
the last command executed.  @code{screen} provides a primitive way of
recalling ``the command that started @dots{}'': You just type the first
letter of that command, then hit @kbd{C-a @{} and @code{screen} tries to
find a previous line that matches with the prompt character to the left
of the cursor. This line is pasted into this window's input queue.  Thus
you have a crude command history (made up by the visible window and its
scrollback buffer).
@end deffn

@node Subprocess Execution, Key Binding, Copy and Paste, Top
@chapter Subprocess Execution
Control Input or Output of a window by another filter process.
Use with care!

@menu
* Exec::                        The @code{exec} command syntax.
* Using Exec::                  Weird things that filters can do.
@end menu

@node Exec, Using Exec,  , Subprocess Execution
@section Exec
@deffn Command exec [[@var{fdpat}] @var{newcommand} [@var{args} ... ]]
(none)@*
Run a unix subprocess (specified by an executable path @var{newcommand} and 
its optional arguments) in the current window. The flow of data between
newcommands stdin/stdout/stderr, the process originally started (let us call it 
"application-process") and 
screen itself (window) is controlled by the file descriptor pattern @var{fdpat}.
This pattern is basically a three character sequence representing stdin, stdout
and stderr of newcommand. A dot (@code{.}) connects the file descriptor
to screen. An exclamation mark (@code{!}) causes the file descriptor to be
connected to the application-process. A colon (@code{:}) combines both.
@*
User input will go to newcommand unless newcommand receives the 
application-process'
output (@var{fdpat}s first character is @samp{!} or @samp{:}) or a pipe symbol
(@samp{|}) is added to the end of @var{fdpat}.
@*
Invoking @code{exec} without arguments shows name and arguments of the currently
running subprocess in this window. Only one subprocess can be running per 
window.
@*
When a subprocess is running the @code{kill} command will affect it instead of 
the windows process. Only one subprocess a time can be running in each window.
@*
Refer to the postscript file @file{doc/fdpat.ps} for a confusing
illustration of all 21 possible combinations. Each drawing shows the digits
2, 1, 0 representing the three file descriptors of newcommand. The box
marked `W' is usual pty that has the application-process on its slave side.
The box marked `P' is the secondary pty that now has screen at its master
side.
@end deffn

@node Using Exec,  , Exec, Subprocess Execution
@section Using Exec
@noindent 
Abbreviations:

@itemize @bullet
@item
Whitespace between the word @samp{exec} and @var{fdpat} and the command name
can be omitted. 

@item
Trailing dots and a @var{fdpat} consisting only of dots can be omitted. 

@item 
A simple @samp{|} is synonymous for the @samp{!..|} pattern.

@item
The word @samp{exec} can be omitted when the @samp{|} abbreviation is used.

@item
The word @samp{exec} can always be replaced by leading @samp{!}.
@end itemize

@noindent 
Examples:

@table @code
@item !/bin/sh
@itemx exec /bin/sh
@itemx exec ... /bin/sh
All of the above are equivalent.
Creates another shell in the same window, while the original shell is still 
running. Output of both shells is displayed and user input is sent to the new
@file{/bin/sh}.

@item !!stty 19200
@itemx exec!stty 19200
@itemx exec !.. stty 19200
All of the above are equivalent.
Set the speed of the window's tty. If your stty command operates on stdout,
then add another @samp{!}. This is a useful command, when a screen window
is directly connected to a serial line that needs to be configured.

@item |less
@itemx exec !..| less
Both are equivalent.
This adds a pager to the window output. The special character @samp{|} is 
needed to give the user control over the pager although it gets its input from 
the window's process. This works, because @samp{less} listens on stderr 
(a behavior that @code{screen} would not expect without the @samp{|}) 
when its stdin is not a tty. @code{Less} versions newer than 177 fail miserably
here; good old @code{pg} still works.

@item !:sed -n s/.*Error.*/\007/p
Sends window output to both, the user and the sed command. The sed inserts an
additional bell character (oct. 007) to the window output seen by screen.
This will cause 'Bell in window x' messages, whenever the string @samp{Error}
appears in the window.
@end table

@node Key Binding, Flow Control, Subprocess Execution, Top
@chapter Key Binding
@cindex key binding
@cindex binding

You may disagree with some of the default bindings (I know I do).  The
@code{bind} command allows you to redefine them to suit your
preferences.

@menu
* Bind::                        @code{bind} syntax.
* Bind Examples::               Using @code{bind}.
* Command Character::           The character used to start keyboard commands.
* Help::                        Show current key bindings.
* Bindkey::                     @code{bindkey} syntax.
* Bindkey Examples::            Some easy examples.
* Bindkey Control::             How to control the bindkey mechanism.
@end menu

@node Bind, Bind Examples,  , Key Binding
@section The @code{bind} command
@deffn Command bind [-c class] key [command [args]]
(none)@*
Bind a command to a key.  The @var{key} argument is either a single
character, a two-character sequence of the form @samp{^x} (meaning
@kbd{C-x}), a backslash followed by an octal number (specifying the
ASCII code of the character), or a backslash followed by a second
character, such as @samp{\^} or @samp{\\}.  The argument can also be
quoted, if you like.  If no further argument is given, any previously
established binding for this key is removed.  The @var{command}
argument can be any command (@pxref{Command Index}).

If a command class is specified via the @code{-c} option, the
key is bound for the specified class.  Use the @code{command}
command to activate a class. Command classes can be used
to create multiple command keys or multi-character bindings.

By default, most suitable commands are bound to one or more keys
(@pxref{Default Key Bindings}; for instance, the command to create a
new window is bound to @kbd{C-c} and @kbd{c}.  The @code{bind} command
can be used to redefine the key bindings and to define new bindings.
@end deffn

@node Bind Examples, Command Character, Bind, Key Binding
@section Examples of the @code{bind} command
@noindent
Some examples:

@example
bind ' ' windows
bind ^f screen telnet foobar
bind \033 screen -ln -t root -h 1000 9 su
@end example

@noindent
would bind the space key to the command that displays a list of windows
(so that the command usually invoked by @kbd{C-a C-w} would also be
available as @kbd{C-a space}), bind @kbd{C-f} to the command
``create a window with a TELNET connection to foobar'', and bind
@key{ESC} to the command that creates an non-login window with title
@samp{root} in slot #9, with a superuser shell and a scrollback buffer
of 1000 lines.

@example
bind -c demo1 0 select 10
bind -c demo1 1 select 11
bind -c demo1 2 select 12
bindkey "^B" command -c demo1
@end example
makes @kbd{C-b 0} select window 10, @kbd{C-b 1} window 11, etc.

@example
bind -c demo2 0 select 10
bind -c demo2 1 select 11
bind -c demo2 2 select 12
bind - command -c demo2
@end example
makes @kbd{C-a - 0} select window 10, @kbd{C-a - 1} window 11, etc.

@node Command Character, Help, Bind Examples, Key Binding
@cindex escape character
@cindex command character
@section Command Character

@deffn Command escape xy
(none)@*
Set the command character to @var{x} and the character generating a
literal command character (by triggering the @code{meta} command)
to @var{y} (similar to the @samp{-e} option). 
Each argument is either a single character, a two-character
sequence of the form @samp{^x} (meaning @kbd{C-x}), a backslash followed
by an octal number (specifying the ASCII code of the character), or a
backslash followed by a second character, such as @samp{\^} or
@samp{\\}.  The default is @samp{^Aa}, but @samp{``} is recommended by
one of the authors.
@end deffn

@deffn Command defescape xy
(none)@*
Set the default command characters. This is equivalent to the command 
@code{escape} except that it is useful for multiuser sessions only. 
In a multiuser session
@code{escape} changes the command character of the calling user, where 
@code{defescape} changes the default command characters for users that
will be added later.
@end deffn

@kindex a
@deffn Command meta
(@kbd{C-a a})@*
Send the command character (@kbd{C-a}) to the process in the current
window.  The keystroke for this command is the second parameter to the
@samp{-e} command line switch (@pxref{Invoking Screen}), or the
@code{escape} .screenrc directive.
@end deffn

@deffn Command command [-c @var{class}]
(none)@*
This command has the same effect as typing the screen escape character
(@kbd{C-a}). It is probably only useful for key bindings.
If the @samp{-c} option is given, select the specified command class.
@xref{Bind}, @xref{Bindkey}.
@end deffn

@node Help, Bindkey, Command Character, Key Binding
@section Help
@kindex ?
@deffn Command help
(@kbd{C-a ?})@*
Displays a help screen showing you all the key bindings.  The first
pages list all the internal commands followed by their bindings.
Subsequent pages will display the custom commands, one command per key.
Press space when you're done reading each page, or return to exit early.
All other characters are ignored.
If the @samp{-c} option is given, display all bound commands for the
specified command class.
@xref{Default Key Bindings}.
@end deffn

@node Bindkey, Bindkey Examples, Help, Key Binding
@section Bindkey
@deffn Command bindkey [@var{opts}] [@var{string} [@var{cmd} @var{args}]]
(none)@*
This command manages screen's input translation tables. Every
entry in one of the tables tells screen how to react if a certain
sequence of characters is encountered. There are three tables:
one that should contain actions programmed by the user, one for
the default actions used for terminal emulation and one for
screen's copy mode to do cursor movement. See @ref{Input Translation}
for a list of default key bindings.

If the @samp{-d}
option is given, bindkey modifies the default table, @samp{-m}
changes the copy mode table and with neither option the user
table is selected. The argument @samp{string} is the sequence of
characters to which an action is bound. This can either be a fixed
string or a termcap keyboard capability name (selectable with the
@samp{-k} option).

Some keys on a VT100 terminal can send a different
string if application mode is turned on (e.g. the cursor keys).
Such keys have two entries in the translation table. You can
select the application mode entry by specifying the @samp{-a}
option.

The @samp{-t} option tells screen not to do inter-character
timing. One cannot turn off the timing if a termcap capability is
used.

@samp{cmd} can be any of screen's commands with an arbitrary
number of @samp{args}. If @samp{cmd} is omitted the key-binding is
removed from the table. 
@end deffn

@node Bindkey Examples, Bindkey Control,Bindkey, Key Binding
@section Bindkey Examples
@noindent
Here are some examples of keyboard bindings:

@example
bindkey -d
@end example
@noindent
Show all of the default key bindings. The application mode entries
are marked with [A].

@example
bindkey -k k1 select 1
@end example
@noindent
Make the "F1" key switch to window one.

@example
bindkey -t foo stuff barfoo
@end example
@noindent
Make @samp{foo} an abbreviation of the word @samp{barfoo}. Timeout is
disabled so that users can type slowly.

@example
bindkey "\024" mapdefault
@end example
@noindent
This key-binding makes @samp{C-t} an escape character for key-bindings. If
you did the above @samp{stuff barfoo} binding, you can enter the word
@samp{foo} by typing @samp{C-t foo}. If you want to insert a
@samp{C-t} you have to press the key twice (i.e., escape the escape
binding).

@example
bindkey -k F1 command
@end example
@noindent
Make the F11 (not F1!) key an alternative screen
escape (besides @samp{C-a}).

@node Bindkey Control, , Bindkey Examples, Key Binding
@section Bindkey Control
@deffn Command mapdefault
(none)@*
Tell screen that the next input character should only be looked up
in the default bindkey table.
@end deffn
@deffn Command mapnotnext
(none)@*
Like mapdefault, but don't even look in the default bindkey table.
@end deffn
@deffn Command maptimeout timo
(none)@*
Set the inter-character timer for input sequence detection to a timeout
of @var{timo} ms. The default timeout is 300ms. Maptimeout with no
arguments shows the current setting.
@end deffn

@node Flow Control, Termcap, Key Binding, Top
@chapter Flow Control
@cindex flow control

@code{screen} can trap flow control characters or pass them to the
program, as you see fit.  This is useful when your terminal wants to use
XON/XOFF flow control and you are running a program which wants to use
^S/^Q for other purposes (i.e. @code{emacs}).

@menu
* Flow Control Summary::        The effect of @code{screen} flow control
* Flow::                        Setting the flow control behavior
* XON/XOFF::                    Sending XON or XOFF to the window
@end menu

@node Flow Control Summary, Flow,  , Flow Control
@section About @code{screen} flow control settings
Each window has a flow-control setting that determines how screen deals
with the XON and XOFF characters (and perhaps the interrupt character).
When flow-control is turned off, screen ignores the XON and XOFF
characters, which allows the user to send them to the current program by
simply typing them (useful for the @code{emacs} editor, for instance).
The trade-off is that it will take longer for output from a
``normal'' program to pause in response to an XOFF.  With
flow-control turned on, XON and XOFF characters are used to immediately
pause the output of the current window.  You can still send these
characters to the current program, but you must use the appropriate
two-character screen commands (typically @kbd{C-a q} (xon) and @kbd{C-a
s} (xoff)).  The xon/xoff commands are also useful for typing C-s and
C-q past a terminal that intercepts these characters.

Each window has an initial flow-control value set with either the
@samp{-f} option or the @code{defflow} command.  By default the
windows are set to automatic flow-switching.  It can then be toggled
between the three states 'fixed on', 'fixed off' and 'automatic'
interactively with the @code{flow} command bound to @kbd{C-a f}.

The automatic flow-switching mode deals with flow control using the
TIOCPKT mode (like @code{rlogin} does). If the tty driver does not
support TIOCPKT, screen tries to determine the right mode based on the
current setting of the application keypad --- when it is enabled,
flow-control is turned off and visa versa.  Of course, you can still
manipulate flow-control manually when needed.

If you're running with flow-control enabled and find that pressing the
interrupt key (usually C-c) does not interrupt the display until another
6-8 lines have scrolled by, try running screen with the @samp{interrupt}
option (add the @samp{interrupt} flag to the @code{flow} command in your
.screenrc, or use the @samp{-i} command-line option).  This causes the
output that @code{screen} has accumulated from the interrupted program
to be flushed.  One disadvantage is that the virtual terminal's memory
contains the non-flushed version of the output, which in rare cases can
cause minor inaccuracies in the output.  For example, if you switch
screens and return, or update the screen with @kbd{C-a l} you would see
the version of the output you would have gotten without @samp{interrupt}
being on.  Also, you might need to turn off flow-control (or use
auto-flow mode to turn it off automatically) when running a program that
expects you to type the interrupt character as input, as the
@samp{interrupt} parameter only takes effect when flow-control is
enabled.  If your program's output is interrupted by mistake, a simple
refresh of the screen with @kbd{C-a l} will restore it.  Give each mode
a try, and use whichever mode you find more comfortable.

@node Flow, XON/XOFF, Flow Control Summary, Flow Control
@section Flow
@deffn Command defflow fstate [interrupt]
(none)@*
Same as the @code{flow} command except that the default setting for new
windows is changed. Initial setting is `auto'.
Specifying @code{flow auto interrupt} has the same effect as the
command-line options @samp{-fa} and @samp{-i}.
Note that if @samp{interrupt} is enabled, all existing displays are
changed immediately to forward interrupt signals.
@end deffn

@kindex f
@kindex C-f
@deffn Command flow [fstate]
(@kbd{C-a f}, @kbd{C-a C-f})@*
Sets the flow-control mode for this window to @var{fstate}, which can be
@samp{on}, @samp{off} or @samp{auto}.
Without parameters it cycles the current window's
flow-control setting.  Default is set by `defflow'.
@end deffn

@node XON/XOFF,  , Flow, Flow Control
@section XON and XOFF
@kindex q
@kindex C-q
@deffn Command xon
(@kbd{C-a q}, @kbd{C-a C-q})@*
Send a ^Q (ASCII XON) to the program in the current window.  Redundant
if flow control is set to @samp{off} or @samp{auto}.
@end deffn

@kindex s
@kindex C-s
@deffn Command xoff
(@kbd{C-a s}, @kbd{C-a C-s})@*
Send a ^S (ASCII XOFF) to the program in the current window.
@end deffn

@node Termcap, Message Line, Flow Control, Top
@chapter Termcap

@code{screen} demands the most out of your terminal so that it can
perform its VT100 emulation most efficiently.  These functions provide
means for tweaking the termcap entries for both your physical terminal
and the one simulated by @code{screen}.

@menu
* Window Termcap::              Choosing a termcap entry for the window.
* Dump Termcap::                Write out a termcap entry for the window.
* Termcap Syntax::              The @code{termcap} and @code{terminfo} commands.
* Termcap Examples::            Uses for @code{termcap}.
* Special Capabilities::        Non-standard capabilities used by @code{screen}.
* Autonuke::                    Flush unseen output
* Obuflimit::                   Allow pending output when reading more
* Character Translation::       Emulating fonts and charsets.
@end menu

@node Window Termcap, Dump Termcap,  , Termcap
@section Choosing the termcap entry for a window
Usually @code{screen} tries to emulate as much of the VT100/ANSI
standard as possible. But if your terminal lacks certain capabilities
the emulation may not be complete. In these cases @code{screen} has to
tell the applications that some of the features are missing. This is no
problem on machines using termcap, because @code{screen} can use the
@code{$TERMCAP} variable to customize the standard screen termcap.

But if you do a rlogin on another machine or your machine supports only
terminfo this method fails. Because of this @code{screen} offers a way
to deal with these cases. Here is how it works:

When @code{screen} tries to figure out a terminal name for itself, it
first looks for an entry named @code{screen.@var{term}}, where
@var{term} is the contents of your @code{$TERM} variable.  If no such entry
exists, @code{screen} tries @samp{screen} (or @samp{screen-w}, if the
terminal is wide (132 cols or more)).  If even this entry cannot be
found, @samp{vt100} is used as a substitute.

The idea is that if you have a terminal which doesn't support an
important feature (e.g. delete char or clear to EOS) you can build a new
termcap/terminfo entry for @code{screen} (named
@samp{screen.@var{dumbterm}}) in which this capability has been
disabled.  If this entry is installed on your machines you are able to
do a rlogin and still keep the correct termcap/terminfo entry.  The
terminal name is put in the @code{$TERM} variable of all new windows.
@code{screen} also sets the @code{$TERMCAP} variable reflecting the
capabilities of the virtual terminal emulated. 
Furthermore, the variable @code{$WINDOW} is set to the window number of each
window.

The actual set of capabilities supported by the virtual terminal depends
on the capabilities supported by the physical terminal.  If, for
instance, the physical terminal does not support underscore mode,
@code{screen} does not put the @samp{us} and @samp{ue} capabilities into
the window's @code{$TERMCAP} variable, accordingly.  However, a minimum number
of capabilities must be supported by a terminal in order to run
@code{screen}; namely scrolling, clear screen, and direct cursor
addressing (in addition, @code{screen} does not run on hardcopy
terminals or on terminals that over-strike).

Also, you can customize the @code{$TERMCAP} value used by @code{screen} by
using the @code{termcap} command, or by defining the variable
@code{$SCREENCAP} prior to startup.  When the latter defined, its value will be
copied verbatim into each window's @code{$TERMCAP} variable.  This can either
be the full terminal definition, or a filename where the terminal
@samp{screen} (and/or @samp{screen-w}) is defined.

Note that @code{screen} honors the @code{terminfo} command if the system
uses the terminfo database rather than termcap.  On such machines the
@code{$TERMCAP} variable has no effect and you must use the
@code{dumptermcap} command (@pxref{Dump Termcap}) and the @code{tic}
program to generate terminfo entries for @code{screen} windows.

When the boolean @samp{G0} capability is present in the termcap entry
for the terminal on which @code{screen} has been called, the terminal
emulation of @code{screen} supports multiple character sets.  This
allows an application to make use of, for instance, the VT100 graphics
character set or national character sets.  The following control
functions from ISO 2022 are supported: @samp{lock shift G0} (@samp{SI}),
@samp{lock shift G1} (@samp{SO}), @samp{lock shift G2}, @samp{lock shift
G3}, @samp{single shift G2}, and @samp{single shift G3}.  When a virtual
terminal is created or reset, the ASCII character set is designated as
@samp{G0} through @samp{G3}.  When the @samp{G0} capability is present,
screen evaluates the capabilities @samp{S0}, @samp{E0}, and @samp{C0} if
present. @samp{S0} is the sequence the terminal uses to enable and start
the graphics character set rather than @samp{SI}.  @samp{E0} is the
corresponding replacement for @samp{SO}. @samp{C0} gives a character by
character translation string that is used during semi-graphics mode.
This string is built like the @samp{acsc} terminfo capability.

When the @samp{po} and @samp{pf} capabilities are present in the
terminal's termcap entry, applications running in a @code{screen} window
can send output to the printer port of the terminal.  This allows a user
to have an application in one window sending output to a printer
connected to the terminal, while all other windows are still active (the
printer port is enabled and disabled again for each chunk of output).
As a side-effect, programs running in different windows can send output
to the printer simultaneously.  Data sent to the printer is not
displayed in the window. The @code{info} command displays a line starting
with @samp{PRIN} while the printer is active.

Some capabilities are only put into the @code{$TERMCAP} variable of the virtual
terminal if they can be efficiently implemented by the physical
terminal.  For instance, @samp{dl} (delete line) is only put into the
@code{$TERMCAP} variable if the terminal supports either delete line itself or
scrolling regions. Note that this may provoke confusion, when the
session is reattached on a different terminal, as the value of @code{$TERMCAP}
cannot be modified by parent processes.  You can force @code{screen} to
include all capabilities in @code{$TERMCAP} with the @samp{-a}
command-line option (@pxref{Invoking Screen}).

The "alternate screen" capability is not enabled by default.
Set the @code{altscreen} @file{.screenrc} command to enable it.

@node Dump Termcap, Termcap Syntax, Window Termcap, Termcap
@section Write out the window's termcap entry
@kindex .
@deffn Command dumptermcap
(@kbd{C-a .})@*
Write the termcap entry for the virtual terminal optimized for the
currently active window to the file @file{.termcap} in the user's
@file{$HOME/.screen} directory (or wherever @code{screen} stores its
sockets. @pxref{Files}).  This termcap entry is identical to
the value of the environment variable @code{$TERMCAP} that is set up by
@code{screen} for each window. For terminfo based systems you will need
to run a converter like @code{captoinfo} and then compile the entry with
@code{tic}.
@end deffn

@node Termcap Syntax, Termcap Examples, Dump Termcap, Termcap
@section The @code{termcap} command
@deffn Command termcap term terminal-tweaks [window-tweaks]
@deffnx Command terminfo term terminal-tweaks [window-tweaks]
@deffnx Command termcapinfo term terminal-tweaks [window-tweaks]
(none)@*
Use this command to modify your terminal's termcap entry without going
through all the hassles involved in creating a custom termcap entry.
Plus, you can optionally customize the termcap generated for the
windows.  
You have to place these commands in one of the screenrc startup files, as they
are meaningless once the terminal emulator is booted.

If your system uses the terminfo database rather than termcap,
@code{screen} will understand the @code{terminfo} command, which has the
same effects as the @code{termcap} command.   Two separate commands are
provided, as there are subtle syntactic differences, e.g. when parameter
interpolation (using @samp{%}) is required. Note that the termcap names of
the capabilities should also be used with the @code{terminfo} command.

In many cases, where the arguments are valid in both terminfo and termcap
syntax, you can use the command @code{termcapinfo}, which is just a
shorthand for a pair of @code{termcap} and @code{terminfo} commands with
identical arguments.
@end deffn

The first argument specifies which terminal(s) should be affected by
this definition.  You can specify multiple terminal names by separating
them with @samp{|}s.  Use @samp{*} to match all terminals and @samp{vt*}
to match all terminals that begin with @samp{vt}.

Each @var{tweak} argument contains one or more termcap defines
(separated by @samp{:}s) to be inserted at the start of the appropriate
termcap entry, enhancing it or overriding existing values.  The first
tweak modifies your terminal's termcap, and contains definitions that
your terminal uses to perform certain functions.  Specify a null string
to leave this unchanged (e.g. "").  The second (optional) tweak modifies
all the window termcaps, and should contain definitions that screen
understands (@pxref{Virtual Terminal}).

@node Termcap Examples, Special Capabilities, Termcap Syntax, Termcap
@section Termcap Examples
Some examples:

@example
termcap xterm*  xn:hs@@
@end example

@noindent
Informs @code{screen} that all terminals that begin with @samp{xterm}
have firm auto-margins that allow the last position on the screen to be
updated (xn), but they don't really have a status line (no 'hs' --
append @samp{@@} to turn entries off).  Note that we assume @samp{xn} for
all terminal names that start with @samp{vt}, but only if you don't
specify a termcap command for that terminal.

@example
termcap vt*  xn
termcap vt102|vt220  Z0=\E[?3h:Z1=\E[?3l
@end example

@noindent
Specifies the firm-margined @samp{xn} capability for all terminals that
begin with @samp{vt}, and the second line will also add the
escape-sequences to switch into (Z0) and back out of (Z1)
132-character-per-line mode if this is a VT102 or VT220.  (You must
specify Z0 and Z1 in your termcap to use the width-changing commands.)

@example
termcap vt100  ""  l0=PF1:l1=PF2:l2=PF3:l3=PF4
@end example

@noindent
This leaves your vt100 termcap alone and adds the function key labels to
each window's termcap entry.

@example
termcap h19|z19  am@@:im=\E@@:ei=\EO  dc=\E[P
@end example

@noindent
Takes a h19 or z19 termcap and turns off auto-margins (am@@) and enables
the insert mode (im) and end-insert (ei) capabilities (the @samp{@@} in
the @samp{im} string is after the @samp{=}, so it is part of the
string).  Having the @samp{im} and @samp{ei} definitions put into your
terminal's termcap will cause screen to automatically advertise the
character-insert capability in each window's termcap.  Each window will
also get the delete-character capability (dc) added to its termcap,
which screen will translate into a line-update for the terminal (we're
pretending it doesn't support character deletion).

If you would like to fully specify each window's termcap entry, you
should instead set the @code{$SCREENCAP} variable prior to running
@code{screen}.  @xref{Virtual Terminal}, for the details of the
@code{screen} terminal emulation.  @xref{Top, , Termcap, termcap, The
Termcap Manual}, for more information on termcap definitions.

@node Special Capabilities, Autonuke, Termcap Examples, Termcap
@section Special Terminal Capabilities
@cindex terminal capabilities
@cindex capabilities 
The following table describes all terminal capabilities that are
recognized by @code{screen} and are not in the termcap manual
(@pxref{Top, , Termcap, termcap, The Termcap Manual}).
You can place these capabilities in your termcap entries (in
@file{/etc/termcap}) or use them with the commands @code{termcap},
@code{terminfo} and @code{termcapinfo} in your @code{screenrc} files. It is
often not possible to place these capabilities in the terminfo database.
@table @samp
@item LP
(bool)@*
Terminal has VT100 style margins (`magic margins'). Note that
this capability is obsolete --- @code{screen} now uses the standard 
@samp{xn} instead.

@item Z0
(str)@*
Change width to 132 columns.

@item Z1
(str)@*
Change width to 80 columns.

@item WS
(str)@*
Resize display. This capability has the desired width and height as
arguments.  SunView(tm) example: @samp{\E[8;%d;%dt}.

@item NF
(bool)@*
Terminal doesn't need flow control. Send ^S and ^Q direct to
the application. Same as @code{flow off}. The opposite of this
capability is @samp{nx}.

@item G0
(bool)@*
Terminal can deal with ISO 2022 font selection sequences.

@item S0
(str)@*
Switch charset @samp{G0} to the specified charset. Default
is @samp{\E(%.}.

@item E0
(str)@*
Switch charset @samp{G0} back to standard charset. Default
is @samp{\E(B}.

@item C0
(str)@*
Use the string as a conversion table for font 0. See
the @samp{ac} capability for more details.

@item CS
(str)@*
Switch cursor-keys to application mode.

@item CE
(str)@*
Switch cursor-keys to cursor mode.

@item AN
(bool)@*
Enable autonuke for displays of this terminal type.
(@pxref{Autonuke}).

@item OL
(num)@*
Set the output buffer limit. See the @samp{obuflimit} command
(@pxref{Obuflimit}) for more details.

@item KJ
(str)@*
Set the encoding of the terminal. See the @samp{encoding} command
(@pxref{Character Processing}) for valid encodings.

@item AF
(str)@*
Change character foreground color in an ANSI conform way. This
capability will almost always be set to @samp{\E[3%dm}
(@samp{\E[3%p1%dm} on terminfo machines).

@item AB
(str)@*
Same as @samp{AF}, but change background color.

@item AX
(bool)@*
Does understand ANSI set default fg/bg color (@samp{\E[39m / \E[49m}).

@item XC
(str)@*
Describe a translation of characters to strings depending on the
current font.  (@pxref{Character Translation}).

@item XT
(bool)@*
Terminal understands special xterm sequences (OSC, mouse tracking).

@item C8
(bool)@*
Terminal needs bold to display high-intensity colors (e.g. Eterm).

@item TF
(bool)@*
Add missing capabilities to the termcap/info entry. (Set by default).
@end table

@node Autonuke, Obuflimit, Special Capabilities, Termcap
@section Autonuke
@deffn Command autonuke @var{state}
(none)@*
Sets whether a clear screen sequence should nuke all the output
that has not been written to the terminal. @xref{Obuflimit}.
This property is set per display, not per window.
@end deffn

@deffn Command defautonuke @var{state}
(none)@*
Same as the @code{autonuke} command except that the default setting for
new displays is also changed. Initial setting is @code{off}. 
Note that you can use the special @code{AN} terminal capability if you
want to have a terminal type dependent setting.
@end deffn

@node Obuflimit, Character Translation, Autonuke, Termcap
@section Obuflimit
@deffn Command obuflimit [@var{limit}]
(none)@*
If the output buffer contains more bytes than the specified limit, no
more data will be read from the windows. The default value is 256. If
you have a fast display (like @code{xterm}), you can set it to some 
higher value. If no argument is specified, the current setting is displayed.
This property is set per display, not per window.
@end deffn

@deffn Command defobuflimit @var{limit}
(none)@*
Same as the @code{obuflimit} command except that the default setting for new
displays is also changed. Initial setting is 256 bytes. Note that you can use
the special @code{OL} terminal capability if you want to have a terminal
type dependent limit.
@end deffn

@node Character Translation, , Obuflimit, Termcap
@section Character Translation
@code{Screen} has a powerful mechanism to translate characters to
arbitrary strings depending on the current font and terminal type.
Use this feature if you want to work with a common standard character
set (say ISO8851-latin1) even on terminals that scatter the more
unusual characters over several national language font pages.

Syntax:

@example
    XC=@var{<charset-mapping>}@{,,@var{<charset-mapping>}@}
    @var{<charset-mapping>} := @var{<designator>}@var{<template>}@{,@var{<mapping>}@}
    @var{<mapping>} := @var{<char-to-be-mapped>}@var{<template-arg>}
@end example

The things in braces may be repeated any number of times.

A @var{<charset-mapping>} tells screen how to map characters
in font @var{<designator>} (@samp{B}: Ascii, @samp{A}: UK,
@samp{K}: german, etc.)
to strings. Every @var{<mapping>} describes to what string a single
character will be translated. A template mechanism is used, as 
most of the time the codes have a lot in common (for example
strings to switch to and from another charset). Each occurrence
of @samp{%} in @var{<template>} gets substituted with the 
@var{template-arg}
specified together with the character. If your strings are not
similar at all, then use @samp{%} as a template and place the full
string in @var{<template-arg>}. A quoting mechanism was added to make
it possible to use a real @samp{%}. The @samp{\} character quotes the
special characters @samp{\}, @samp{%}, and @samp{,}.

Here is an example:

@example
    termcap hp700 'XC=B\E(K%\E(B,\304[,\326\\\\,\334]'
@end example

This tells @code{screen}, how to translate ISOlatin1 (charset @samp{B})
upper case umlaut characters on a @code{hp700} terminal that has a
German charset. @samp{\304} gets translated to
@samp{\E(K[\E(B} and so on.
Note that this line gets parsed *three* times before the internal
lookup table is built, therefore a lot of quoting is needed to
create a single @samp{\}.

Another extension was added to allow more emulation: If a mapping
translates the unquoted @samp{%} char, it will be sent to the terminal
whenever screen switches to the corresponding @var{<designator>}.
In this
special case the template is assumed to be just @samp{%} because
the charset switch sequence and the character mappings normally
haven't much in common.

This example shows one use of the extension:
@example
    termcap xterm 'XC=K%,%\E(B,[\304,\\\\\326,]\334'
@end example

Here, a part of the German (@samp{K}) charset is emulated on an xterm.
If screen has to change to the @samp{K} charset, @samp{\E(B} will be
sent
to the terminal, i.e. the ASCII charset is used instead. The
template is just @samp{%}, so the mapping is straightforward:
@samp{[} to @samp{\304}, @samp{\} to @samp{\326}, and @samp{]} to
@samp{\334}.

@node Message Line, Logging, Termcap, Top
@chapter The Message Line
@cindex message line

@code{screen} displays informational messages and other diagnostics in a
@dfn{message line} at the bottom of the screen.  If your terminal has a
status line defined in its termcap, screen will use this for displaying
its messages, otherwise the last line of the screen will be temporarily
overwritten and output will be momentarily interrupted.  The message
line is automatically removed after a few seconds delay, but it can also
be removed early (on terminals without a status line) by beginning to
type.

@menu
* Privacy Message::             Using the message line from your program.
* Hardware Status Line::        Use the terminal's hardware status line.
* Last Message::                Redisplay the last message.
* Message Wait::                Control how long messages are displayed.
@end menu

@node Privacy Message, Hardware Status Line,  , Message Line
@section Using the message line from your program
The message line facility can be used by an application running in the
current window by means of the ANSI @dfn{Privacy message} control
sequence.  For instance, from within the shell, try something like:

@example
echo "@value{esc}^Hello world from window $WINDOW@value{esc}\"
@end example

where @samp{@value{esc}} is ASCII ESC and the @samp{^} that follows it
is a literal caret or up-arrow.

@node Hardware Status Line, Last Message, Privacy Message, Message Line
@section Hardware Status Line
@deffn Command hardstatus [state]
@deffnx Command hardstatus [@code{always}]@code{lastline}|@code{message}|@code{ignore} [string]
@deffnx Command hardstatus @code{string} [string]
(none)@*
This command configures the use and emulation of the terminal's
hardstatus line. The first form toggles whether @code{screen}
will use the hardware status line to display messages. If the
flag is set to @samp{off}, these messages
are overlaid in reverse video mode at the display line. The default
setting is @samp{on}.

The second form tells screen what to do if the terminal doesn't
have a hardstatus line (i.e. the termcap/terminfo capabilities
"hs", "ts", "fs" and "ds" are not set). If the type
@code{lastline} is used, screen will reserve the last line of the
display for the hardstatus. @code{message} uses
@code{screen}'s message mechanism and
@code{ignore} tells @code{screen} never to display the hardstatus.
If you prepend the word @code{always} to the type (e.g., @code{alwayslastline}), @code{screen} will use
the type even if the terminal supports a hardstatus line.

The third form specifies the contents of the hardstatus line.
@code{%h} is used as default string, i.e., the stored hardstatus of the
current window (settable via @samp{ESC]0;^G} or @samp{ESC_\\}) is
displayed.
You can customize this to any string you like including
string escapes (@pxref{String Escapes}).
If you leave
out the argument @var{string}, the current string is displayed.

You can mix the second and third form by providing the string as
additional argument.
@end deffn

@node Last Message, Message Wait, Hardware Status Line, Message Line
@section Display Last Message
@kindex m
@kindex C-m
@deffn Command lastmsg
(@kbd{C-a m}, @kbd{C-a C-m})@*
Repeat the last message displayed in the message line.  Useful if you're
typing when a message appears, because (unless your terminal has a
hardware status line) the message goes away when you press a key.
@end deffn

@node Message Wait,  , Last Message, Message Line
@section Message Wait
@deffn Command msgminwait sec
(none)@*
Defines the time @code{screen} delays a new message when another is
currently displayed.  Defaults to 1 second.
@end deffn

@deffn Command msgwait sec
(none)@*
Defines the time a message is displayed, if @code{screen} is not
disturbed by other activity.  Defaults to 5 seconds.
@end deffn

@node Logging, Startup, Message Line, Top
@chapter Logging

This section describes the commands for keeping a record of your session.

@menu
* Hardcopy::                    Dump the current screen to a file
* Log::                         Log the output of a window to a file
@end menu

@node Hardcopy, Log,  , Logging
@section hardcopy
@kindex h
@kindex C-h
@deffn Command hardcopy [-h] [@var{file}]
(@kbd{C-a h}, @kbd{C-a C-h})@*
Writes out the currently displayed image to the file @var{file}, or,
if no filename is specified, to @file{hardcopy.@var{n}}
in the default directory, where @var{n} is the number of the
current window.  This either appends or overwrites the file if it
exists, as determined by the @code{hardcopy_append} command.
If the option @code{-h} is specified, dump also the
contents of the scrollback buffer.
@end deffn

@deffn Command hardcopy_append state
(none)@*
If set to @samp{on}, @code{screen} will append to the
@file{hardcopy.@var{n}} files created by the command @code{hardcopy};
otherwise, these files are overwritten each time.
@end deffn

@deffn Command hardcopydir directory
(none)@*
Defines a directory where hardcopy files will be placed.
If unset, hardcopys are dumped in screen's current working
directory.
@end deffn

@node Log,  , Hardcopy, Logging
@section log

@deffn Command deflog state
(none)@*
Same as the @code{log} command except that the default setting for new
windows is changed.  Initial setting is `off'.
@end deffn

@kindex H
@deffn Command log [state]
(@kbd{C-a H})@*
Begins/ends logging of the current window to the file
@file{screenlog.@var{n}} in the window's default directory, where
@var{n} is the number of the current window.
This filename can be changed with the @samp{logfile} command.
If no parameter is given,
the logging state is toggled.  The session log is
appended to the previous contents of the file if it already exists.  The
current contents and the contents of the scrollback history are not
included in the session log.  Default is @samp{off}.
@end deffn

@deffn Command logfile filename
@deffnx Command logfile flush secs
(none)@*
Defines the name the log files will get. The default is @samp{screenlog.%n}.
The second form changes the number of seconds @code{screen}
will wait before flushing the logfile buffer to the file-system. The
default value is 10 seconds.
@end deffn

@deffn Command logtstamp [state]
@deffnx Command logtstamp @code{after} secs
@deffnx Command logtstamp @code{string} string
(none)@*
This command controls logfile time-stamp mechanism of screen. If
time-stamps are turned @samp{on}, screen adds a string containing
the current time to the logfile after two minutes of inactivity.
When output continues and more than another two minutes have passed,
a second time-stamp is added to document the restart of the
output. You can change this timeout with the second form
of the command. The third form is used for customizing the time-stamp
string (@samp{-- %n:%t -- time-stamp -- %M/%d/%y %c:%s --\n} by
default).
@end deffn

@node Startup, Miscellaneous, Logging, Top
@chapter Startup

This section describes commands which are only useful in the
@file{.screenrc} file, for use at startup.

@menu
* echo::                        Display a message.
* sleep::                       Pause execution of the @file{.screenrc}.
* Startup Message::             Control display of the copyright notice.
@end menu

@node echo, sleep,  , Startup
@section echo
@deffn Command echo [@samp{-n}] message
(none)@*
The echo command may be used to annoy @code{screen} users with a
'message of the day'. Typically installed in a global screenrc. 
The option @samp{-n} may be used to suppress the line feed.
See also @code{sleep}.  
Echo is also useful for online checking of environment variables.
@end deffn

@node sleep, Startup Message, echo, Startup
@section sleep
@deffn Command sleep num
(none)@*
This command will pause the execution of a .screenrc file for @var{num}
seconds.  Keyboard activity will end the sleep.  It may be used to give
users a chance to read the messages output by @code{echo}.
@end deffn

@node Startup Message,  , sleep, Startup
@section Startup Message
@deffn Command startup_message state
(none)@*
Select whether you want to see the copyright notice during startup.
Default is @samp{on}, as you probably noticed.
@end deffn

@node Miscellaneous, String Escapes, Startup, Top
@chapter Miscellaneous commands

The commands described here do not fit well under any of the other
categories.

@menu
* At::                          Execute a command at other displays or windows.
* Break::                       Send a break signal to the window.
* Debug::                       Suppress/allow debugging output.
* License::                     Display the disclaimer page.
* Nethack::                     Use @code{nethack}-like error messages.
* Nonblock::                    Disable flow-control to a display.
* Number::                      Change the current window's number.
* Silence::                     Notify on inactivity.
* Time::                        Display the time and load average.
* Verbose::                     Display window creation commands.
* Version::                     Display the version of @code{screen}.
* Zombie::                      Keep dead windows.
* Printcmd::                    Set command for VT100 printer port emulation.
* Sorendition::                 Change the text highlighting method.
* Attrcolor::                   Map attributes to colors.
* Setsid::                      Change process group management.
* Eval::                        Parse and execute arguments.
* Maxwin::                      Set the maximum window number.
* Backtick::                    Program a command for a backtick string escape.
* Screen Saver::                Define a screen safer.
* Zmodem::                      Define how screen treats zmodem requests.
@end menu

@node At, Break,  , Miscellaneous
@section At
@deffn Command at [identifier][#|*|%] command [args]
(none)@*
Execute a command at other displays or windows as if it had been entered there.
@code{At} changes the context (the `current window' or `current display'
setting) of the command. If the first parameter describes a non-unique context,
the command will be executed multiple times. If the first parameter is of the 
form @samp{@var{identifier}*} then identifier is matched against user names.
The command is executed once for each display of the selected user(s).
If the first parameter is of the form @samp{@var{identifier}%} identifier is
matched against displays. Displays are named after the ttys they attach. The
prefix @samp{/dev/} or @samp{/dev/tty} may be omitted from the identifier.
If @var{identifier} has a @code{#} or nothing appended it is matched against
window numbers and titles. Omitting an identifier in front of the @code{#},
@code{*} or @code{%} character selects all users, displays or windows because
a prefix-match is performed. Note that on the affected display(s) a short
message will describe what happened. 
Note that the @code{#} character works as a comment introducer when it is 
preceded by whitespace. This can be escaped by prefixing @code{#} with a 
@code{\}. 
Permission is checked for the initiator of the @code{at} command, not for the
owners of the affected display(s).
Caveat: 
When matching against windows, the command is executed at least 
once per window. Commands that change the internal arrangement of windows
(like @code{other}) may be called again. In shared windows the command will
be repeated for each attached display. Beware, when issuing toggle commands
like @code{login}!
Some commands (e.g. @code{\*Qprocess}) require
that a display is associated with the target windows.  These commands may not
work correctly under @code{at} looping over windows.
@end deffn

@node Break, Debug, At, Miscellaneous
@section Break
@deffn Command break [duration]
(none)@*
Send a break signal for @var{duration}*0.25 seconds to this window.
For non-Posix systems the time interval is rounded up to full seconds.
Most useful if a character device is attached to the window rather than
a shell process (@pxref{Window Types}). The maximum duration of
a break signal is limited to 15 seconds.
@end deffn

@deffn Command pow_break
(none)@*
Reopen the window's terminal line and send a break condition.
@end deffn

@deffn Command breaktype [tcsendbreak|TIOCSBRK|TCSBRK]
(none)@*
Choose one of the available methods of generating a break signal for
terminal devices. This command should affect the current window only.
But it still behaves identical to @code{defbreaktype}. This will be changed in
the future.
Calling @code{breaktype} with no parameter displays the break setting for the
current window.
@end deffn

@deffn Command defbreaktype [tcsendbreak|TIOCSBRK|TCSBRK]
(none)@*
Choose one of the available methods of generating a break signal for
terminal devices opened afterwards. The preferred methods are 
@code{tcsendbreak} and
@code{TIOCSBRK}. The third, @code{TCSBRK}, blocks the complete @code{screen}
session for the duration of the break, but it may be the only way to
generate long breaks. @code{tcsendbreak} and @code{TIOCSBRK} may or may not
produce long breaks with spikes (e.g. 4 per second). This is not only system
dependent, this also differs between serial board drivers.
Calling @code{defbreaktype} with no parameter displays the current setting.
@end deffn

@node Debug, License, Break, Miscellaneous
@section Debug
@deffn Command debug [on|off]
(none)@*
Turns runtime debugging on or off. If @code{screen} has been compiled with
option @code{-DDEBUG} debugging is available and is turned on per default.
Note that this command only affects debugging output from the main 
@samp{SCREEN} process correctly. Debug output from attacher processes can only
be turned off once and forever.
@end deffn

@node License, Nethack, Debug, Miscellaneous
@section License
@deffn Command license
(none)@*
Display the disclaimer page. This is done whenever @code{screen} is
started without options, which should be often enough.
@end deffn

@node Nethack, Nonblock, License, Miscellaneous
@section Nethack
@deffn Command nethack state
(none)@*
Changes the kind of error messages used by @code{screen}.  When you are
familiar with the game @code{nethack}, you may enjoy the nethack-style
messages which will often blur the facts a little, but are much funnier
to read. Anyway, standard messages often tend to be unclear as well.

This option is only available if @code{screen} was compiled with the
NETHACK flag defined (@pxref{Installation}). The default setting is then
determined by the presence of the environment variable
@code{$NETHACKOPTIONS}.
@end deffn

@node Nonblock, Number, Nethack, Miscellaneous
@section Nonblock
@deffn Command nonblock [@var{state}|@var{numsecs}]
Tell screen how to deal with user interfaces (displays) that cease to
accept output. This can happen if a user presses ^S or a TCP/modem
connection gets cut but no hangup is received. If nonblock is
@code{off} (this is the default) screen waits until the display 
restarts to accept the output. If nonblock is @code{on}, screen
waits until the timeout is reached (@code{on} is treated as 1s). If the
display still doesn't receive characters, screen will consider
it ``blocked'' and stop sending characters to it. If at
some time it restarts to accept characters, screen will unblock 
the display and redisplay the updated window contents.
@end deffn

@deffn Command defnonblock @var{state}|@var{numsecs}
Same as the @code{nonblock} command except that the default setting for
displays is changed. Initial setting is @code{off}.
@end deffn

@node Number, Silence, Nonblock, Miscellaneous
@section Number
@kindex N
@deffn Command number [@var{n}]
(@kbd{C-a N})@*
Change the current window's number. If the given number @var{n} is already
used by another window, both windows exchange their numbers. If no argument is
specified, the current window number (and title) is shown.
@end deffn

@node Silence, Time, Number, Miscellaneous
@section Silence
@deffn Command silence [@var{state}|@var{sec}]
(none)@*
Toggles silence monitoring of windows. When silence is turned on and an 
affected window is switched into the background, you will receive the
silence notification message in the status line after a specified period
of inactivity (silence). The default timeout can be changed with the
@code{silencewait} command or by specifying a number of seconds instead of
@code{on} or @code{off}. Silence is initially off for all windows.
@end deffn

@deffn Command defsilence state
(none)@*
Same as the @code{silence} command except that the default setting for
new windows is changed.  Initial setting is `off'.
@end deffn

@deffn Command silencewait @var{seconds}
(none)@*
Define the time that all windows monitored for silence should wait
before displaying a message. Default is 30 seconds.
@end deffn

@node Time, Verbose, Silence, Miscellaneous
@section Time
@kindex t
@kindex C-t
@deffn Command time [@var{string}]
(@kbd{C-a t}, @kbd{C-a C-t})@*
Uses the message line to display the time of day, the host name, and the
load averages over 1, 5, and 15 minutes (if this is available on your
system).  For window-specific information use @code{info} (@pxref{Info}).
If a @var{string} is specified, it changes the format of the time report
like it is described in the string escapes chapter (@pxref{String Escapes}). Screen uses a default of @samp{%c:%s %M %d %H%? %l%?}.
@end deffn

@node Verbose, Version, Time, Miscellaneous
@section Verbose
@deffn Command verbose [on|off]
If verbose is switched on, the command name is echoed, whenever a window
is created (or resurrected from zombie state). Default is off.
Without parameter, the current setting is shown.
@end deffn

@node Version, Zombie, Verbose, Miscellaneous
@section Version
@kindex v
@deffn Command version
(@kbd{C-a v})@*
Display the version and modification date in the message line.
@end deffn

@node Zombie, Printcmd, Version, Miscellaneous
@section Zombie
@deffn Command zombie [@var{keys} [onerror] ]
@deffnx Command defzombie [@var{keys}]
(none)@*
Per default windows are removed from the window list as soon as the
windows process (e.g. shell) exits. When a string of two keys is
specified to the zombie command, `dead' windows will remain in the list.
The @code{kill} command may be used to remove the window. Pressing the first key
in the dead window has the same effect. Pressing the second key, however,
screen will attempt to resurrect the window. The process that was initially 
running in the window will be launched again. Calling @code{zombie} without
parameters will clear the zombie setting, thus making windows disappear when
the process terminates.

As the zombie setting is affected globally for all windows, this command 
should only be called @code{defzombie}. Until we need this as a per window 
setting, the commands @code{zombie} and @code{defzombie} are synonymous.

Optionally you can put the word @code{onerror} after the keys. This will
cause screen to monitor exit status of the process running in the window.
If it exits normally ('0'), the window disappears. Any other exit value
causes the window to become a zombie.
@end deffn

@node Printcmd, Sorendition, Zombie, Miscellaneous
@section Printcmd
@deffn Command printcmd [@var{cmd}]
(none)@*
If @var{cmd} is not an empty string, screen will not use the terminal
capabilities @code{po/pf} for printing if it detects an ansi print
sequence @code{ESC [ 5 i}, but pipe the output into @var{cmd}.
This should normally be a command like @samp{lpr} or
@samp{cat > /tmp/scrprint}.
@code{Printcmd} without an argument displays the current setting.
The ansi sequence @code{ESC \} ends printing and closes the pipe.

Warning: Be careful with this command! If other user have write
access to your terminal, they will be able to fire off print commands.
@end deffn

@node Sorendition, Attrcolor, Printcmd, Miscellaneous
@section Sorendition
@deffn Command sorendition [@var{attr} [@var{color}]]
(none)@*
Change the way screen does highlighting for text marking and printing
messages.
See the chapter
about string escapes (@pxref{String Escapes}) for the syntax of
the modifiers. The default is currently @samp{=s dd} (standout,
default colors).
@end deffn

@node Attrcolor, Setsid, Sorendition, Miscellaneous
@section Attrcolor
@deffn Command attrcolor @var{attrib} [@var{attribute/color-modifier}]
(none)@*
This command can be used to highlight attributes by changing the color of
the text. If the attribute
@var{attrib}
is in use, the specified attribute/color modifier is also applied. If no
modifier is given, the current one is deleted. See the chapter
about string escapes (@pxref{String Escapes}) for the syntax of
the modifier. Screen understands two pseudo-attributes, @code{i}
stands for high-intensity foreground color and @code{I} for
high-intensity background color.

@noindent 
Examples:
@table @code
@item attrcolor b "R"
Change the color to bright red if bold text is to be printed.
@item attrcolor u "-u b"
Use blue text instead of underline.
@item attrcolor b ".I"
Use bright colors for bold text. Most terminal emulators do this
already.
@item attrcolor i "+b"
Make bright colored text also bold.
@end table
@end deffn

@node Setsid, Eval, Attrcolor, Miscellaneous
@section Setsid
@deffn Command setsid state
(none)@*
Normally screen uses different sessions and process groups for
the windows. If setsid is turned @code{off}, this is not done
anymore and all windows will be in the same process group as the
screen backend process. This also breaks job-control, so be careful.
The default is @code{on}, of course. This command is probably useful
only in rare circumstances.
@end deffn

@node Eval, Maxwin, Setsid, Miscellaneous
@section Eval
@deffn Command eval @var{command1} [@var{command2} ...]
(none)@*
Parses and executes each argument as separate command.
@end deffn

@node Maxwin, Backtick, Eval, Miscellaneous
@section Maxwin
@deffn Command maxwin @var{n}
(none)@*
Set the maximum window number screen will create. Doesn't affect 
already existing windows. The number may only be decreased.
@end deffn

@node Backtick, Screen Saver, Maxwin, Miscellaneous
@section Backtick
@deffn Command backtick @var{id} @var{lifespan} @var{autorefresh} @var{command} [@var{args}]
@deffnx Command backtick @var{id}
(none)@*
Program the backtick command with the numerical id @var{id}.
The output of such a command is used for substitution of the
@code{%`} string escape (@pxref{String Escapes}).
The specified @var{lifespan} is the number
of seconds the output is considered valid. After this time, the
command is run again if a corresponding string escape is encountered.
The @var{autorefresh} parameter triggers an
automatic refresh for caption and hardstatus strings after the
specified number of seconds. Only the last line of output is used 
for substitution.

If both the @var{lifespan} and the @var{autorefresh} parameters
are zero, the backtick program is expected to stay in the
background and generate output once in a while.
In this case, the command is executed right away and screen stores
the last line of output. If a new line gets printed screen will
automatically refresh the hardstatus or the captions.

The second form of the command deletes the backtick command 
with the numerical id @var{id}.
@end deffn

@node Screen Saver, Zmodem, Backtick, Miscellaneous
@section Screen Saver
@deffn Command idle [@var{timeout} [@var{cmd} @var{args}]]
(none)@*
Sets a command that is run after the specified number of
seconds inactivity is reached. This command will normally
be the @code{blanker} command to create a screen blanker, but
it can be any screen command. If no command is specified,
only the timeout is set. A timeout of zero (ot the special
timeout @code{off}) disables the timer. If no arguments are
given, the current settings are displayed.
@end deffn

@deffn Command blanker
(none)@*
Activate the screen blanker. First the screen is cleared.
If no blanker program is defined, the cursor is turned
off, otherwise, the program is started and it's output is
written to the screen. The screen blanker is killed with
the first keypress, the read key is discarded.

This command is normally used together with the @code{idle}
command.
@end deffn

@deffn Command blankerprg [@var{program args}]
Defines a blanker program. Disables the blanker program if
no arguments are given.
@end deffn

@node Zmodem, , Screen Saver, Miscellaneous
@section Zmodem
@deffn Command zmodem [off|auto|catch|pass]
@deffnx Command zmodem sendcmd [string]
@deffnx Command zmodem recvcmd [string]
(none)@*
Define zmodem support for screen. Screen understands two
different modes when it detects a zmodem request: @code{pass}
and @code{catch}. If the mode is set to @code{pass}, screen will
relay all data to the attacher until the end of the
transmission is reached. In @code{catch} mode screen acts as a
zmodem endpoint and starts the corresponding rz/sz commands.
If the mode is set to @code{auto}, screen will use @code{catch} if
the window is a tty (e.g. a serial line), otherwise it
will use @code{pass}.

You can define the templates screen uses in @code{catch} mode
via the second and the third form.

Note also that this is an experimental feature.
@end deffn

@node String Escapes, Environment, Miscellaneous, Top
@chapter String Escapes
@cindex string escapes
Screen provides an escape mechanism to insert information like the
current time into messages or file names. The escape character
is @code{%} with one exception: inside of a window's hardstatus
@code{^%} (@code{^E}) is used instead.

Here is the full list of supported escapes:

@table @code
@item %
the escape character itself
@item a
either @code{am} or @code{pm}
@item A
either @code{AM} or @code{PM}
@item c
current time @code{HH:MM} in 24h format
@item C
current time @code{HH:MM} in 12h format
@item d
day number
@item D
weekday name
@item f
flags of the window
@item F
sets %? to true if the window has the focus
@item h
hardstatus of the window
@item H
hostname of the system
@item l
current load of the system
@item m
month number
@item M
month name
@item n
window number
@item s
seconds
@item S
session name
@item t
window title
@item u
all other users on this window
@item w
all window numbers and names. With @code{-} qualifier: up to the current
window; with @code{+} qualifier: starting with the window after the current
one.
@item W
all window numbers and names except the current one
@item y
last two digits of the year number
@item Y
full year number
@item ?
the part to the next @code{%?} is displayed only if a @code{%} escape
inside the part expands to a non-empty string
@item :
else part of @code{%?}
@item =
pad the string to the display's width (like TeX's hfill). If a
number is specified, pad to the percentage of the window's width.
A @code{0} qualifier tells screen to treat the number as absolute position.
You can specify to pad relative to the last absolute pad position
by adding a @code{+} qualifier or to pad relative to the right margin
by using @code{-}. The padding truncates the string if the specified
position lies before the current position. Add the @code{L} qualifier
to change this.
@item <
same as @code{%=} but just do truncation, do not fill with spaces
@item >
mark the current text position for the next truncation. When
screen needs to do truncation, it tries to do it in a way that
the marked position gets moved to the specified percentage of
the output area. (The area starts from the last absolute pad
position and ends with the position specified by the truncation
operator.) The @code{L} qualifier tells screen to mark the truncated
parts with @samp{...}.
@item @{
attribute/color modifier string terminated by the next @code{@}}
@item `
Substitute with the output of a `backtick' command. The length
qualifier is misused to identify one of the commands. @xref{Backtick}.
@end table
The @code{c} and @code{C} escape may be qualified with a @code{0} to
make screen use
zero instead of space as fill character.
The @code{n} and
@code{=} escapes understand
a length qualifier (e.g. @code{%3n}), @code{D} and @code{M} can be
prefixed with @code{L} to generate long names, @code{w} and
@code{W} also show the window flags if @code{L} is given.

An attribute/color modifier is is used to change the attributes or the
color settings. Its format
is @samp{[attribute modifier] [color description]}. The attribute modifier
must be prefixed by a change type indicator if it can be confused with
a color description. The following change types are known: 
@table @code
@item +
add the specified set to the current attributes
@item -
remove the set from the current attributes
@item !
invert the set in the current attributes
@item =
change the current attributes to the specified set
@end table
The attribute set can either be specified as a hexadecimal number or
a combination of the following letters: 
@table @code
@item d
dim
@item u
underline
@item b
bold
@item r
reverse
@item s
standout
@item B
blinking
@end table
Colors are coded either as a hexadecimal number or two letters specifying
the desired background and foreground color (in that order). The following
colors are known:
@table @code
@item k
black
@item r
red
@item g
green
@item y
yellow
@item b
blue
@item m
magenta
@item c
cyan
@item w
white
@item d
default color
@item .
leave color unchanged
@end table
The capitalized versions of the letter specify bright colors. You can also
use the pseudo-color @samp{i} to set just the brightness and leave the color
unchanged.

A one digit/letter color description is treated as foreground or
background color dependent on the current attributes: if reverse mode is
set, the background color is changed instead of the foreground color.
If you don't like this, prefix the color with a @samp{.}. If you want
the same behavior for two-letter color descriptions, also prefix them
with a @samp{.}.

As a special case, @samp{%@{-@}} restores the attributes and colors that
were set before the last change was made (i.e. pops one level of the
color-change stack).

@noindent
Examples:
@table @samp
@item G
set color to bright green
@item +b r
use bold red
@item = yd
clear all attributes, write in default color on yellow background.
@item %-Lw%@{= BW@}%50>%n%f* %t%@{-@}%+Lw%<
The available windows centered at the current win dow and truncated to
the available width. The current window is displayed white on blue.
This can be used with @samp{hardstatus alwayslastline}.
@item %?%F%@{.R.@}%?%3n %t%? [%h]%?
The window number and title and the window's hardstatus, if one is set.
Also use a red background if this is the active focus.
Useful for @samp{caption string}.
@end table


@node Environment, Files, String Escapes, Top
@chapter Environment Variables
@cindex environment

@table @code
@item COLUMNS
Number of columns on the terminal (overrides termcap entry).

@item HOME
Directory in which to look for .screenrc.

@item LINES
Number of lines on the terminal (overrides termcap entry).

@item LOCKPRG
Screen lock program.

@item NETHACKOPTIONS
Turns on @code{nethack} option.

@item PATH
Used for locating programs to run.

@item SCREENCAP
For customizing a terminal's @code{TERMCAP} value.

@item SCREENDIR
Alternate socket directory.

@item SCREENRC
Alternate user screenrc file.

@item SHELL
Default shell program for opening windows (default @file{/bin/sh}).

@item STY
Alternate socket name. If @code{screen} is invoked, and the environment variable
@code{STY} is set, then it creates only a window in the running @code{screen}
session rather than starting a new session.

@item SYSSCREENRC
Alternate system screenrc file.

@item TERM
Terminal name.

@item TERMCAP
Terminal description.

@item WINDOW
Window number of a window (at creation time).
@end table

@node Files, Credits, Environment, Top
@chapter Files Referenced
@cindex files

@table @file
@item .../screen-4.?.??/etc/screenrc
@itemx .../screen-4.?.??/etc/etcscreenrc
Examples in the @code{screen} distribution package for private and
global initialization files.

@item @code{$SYSSCREENRC}
@itemx /local/etc/screenrc
@code{screen} initialization commands

@item @code{$SCREENRC}
@itemx @code{$HOME}/.iscreenrc
@itemx @code{$HOME}/.screenrc
Read in after /local/etc/screenrc

@item @code{$SCREENDIR}/S-@var{login}

@item /local/screens/S-@var{login}
Socket directories (default)

@item /usr/tmp/screens/S-@var{login}
Alternate socket directories.

@item @var{socket directory}/.termcap
Written by the @code{dumptermcap} command

@item /usr/tmp/screens/screen-exchange or
@itemx /tmp/screen-exchange
@code{screen} interprocess communication buffer

@item hardcopy.[0-9]
Screen images created by the hardcopy command

@item screenlog.[0-9]
Output log files created by the log command

@item /usr/lib/terminfo/?/* or
@itemx /etc/termcap
Terminal capability databases

@item /etc/utmp
Login records

@item @code{$LOCKPRG}
Program for locking the terminal.
@end table

@node Credits, Bugs, Files, Top
@chapter Credits

@noindent
Authors @*
=======

Originally created by Oliver Laumann, this latest version was
produced by Wayne Davison, Juergen Weigert and Michael Schroeder.

@noindent
Contributors @*
============

@example
     Ken Beal (kbeal@@amber.ssd.csd.harris.com),
     Rudolf Koenig (rfkoenig@@informatik.uni-erlangen.de),
     Toerless Eckert (eckert@@informatik.uni-erlangen.de),
     Wayne Davison (davison@@borland.com),
     Patrick Wolfe (pat@@kai.com, kailand!pat),
     Bart Schaefer (schaefer@@cse.ogi.edu),
     Nathan Glasser (nathan@@brokaw.lcs.mit.edu),
     Larry W. Virden (lvirden@@cas.org),
     Howard Chu (hyc@@hanauma.jpl.nasa.gov),
     Tim MacKenzie (tym@@dibbler.cs.monash.edu.au),
     Markku Jarvinen (mta@@@{cc,cs,ee@}.tut.fi),
     Marc Boucher (marc@@CAM.ORG),
     Doug Siebert (dsiebert@@isca.uiowa.edu),
     Ken Stillson (stillson@@tsfsrv.mitre.org),
     Ian Frechett (frechett@@spot.Colorado.EDU),
     Brian Koehmstedt (bpk@@gnu.ai.mit.edu),
     Don Smith (djs6015@@ultb.isc.rit.edu),
     Frank van der Linden (vdlinden@@fwi.uva.nl),
     Martin Schweikert (schweik@@cpp.ob.open.de),
     David Vrona (dave@@sashimi.lcu.com),
     E. Tye McQueen (tye%spillman.UUCP@@uunet.uu.net),
     Matthew Green (mrg@@eterna.com.au),
     Christopher Williams (cgw@@pobox.com),
     Matt Mosley (mattm@@access.digex.net),
     Gregory Neil Shapiro (gshapiro@@wpi.WPI.EDU),
     Jason Merrill (jason@@jarthur.Claremont.EDU),
     Johannes Zellner (johannes@@zellner.org),
     Pablo Averbuj (pablo@@averbuj.com).
@end example

@noindent
Version @*
=======

This manual describes version @value{version} of the @code{screen}
program. Its roots are a merge of a custom version 2.3PR7 by Wayne
Davison and several enhancements to Oliver Laumann's version 2.0.
Note that all versions numbered 2.x are copyright by Oliver Laumann.

See also @xref{Availability}.

@node Bugs, Installation, Credits, Top
@chapter Bugs
@cindex bugs

Just like any other significant piece of software, @code{screen} has a
few bugs and missing features.  Please send in a bug report if you have
found a bug not mentioned here.

@menu
* Known Bugs::                  Problems we know about.
* Reporting Bugs::              How to contact the maintainers.
* Availability::                Where to find the latest screen version.
@end menu

@node Known Bugs, Reporting Bugs,  , Bugs
@section Known Bugs

@itemize @bullet
@item
@samp{dm} (delete mode) and @samp{xs} are not handled correctly (they
are ignored).  @samp{xn} is treated as a magic-margin indicator.

@item
@code{screen} has no clue about double-high or double-wide characters. 
But this is the only area where @code{vttest} is allowed to fail.

@item
It is not possible to change the environment variable @code{$TERMCAP}
when reattaching under a different terminal type.

@item
The support of terminfo based systems is very limited. Adding extra
capabilities to @code{$TERMCAP} may not have any effects.

@item
@code{screen} does not make use of hardware tabs.

@item
@code{screen} must be installed setuid root on most systems
in order to be able to
correctly change the owner of the tty device file for each window.
Special permission may also be required to write the file
@file{/etc/utmp}.

@item
Entries in @file{/etc/utmp} are not removed when @code{screen} is killed
with SIGKILL.  This will cause some programs (like "w" or "rwho") to
advertise that a user is logged on who really isn't.

@item
@code{screen} may give a strange warning when your tty has no utmp
entry.

@item
When the modem line was hung up, @code{screen} may not automatically detach
(or quit) unless the device driver sends a HANGUP signal. To detach such a 
@code{screen} session use the -D or -d command line option.

@item
If a password is set, the command line options -d and -D still detach a 
session without asking.

@item
Both @code{breaktype} and @code{defbreaktype} change the break generating
method used by all terminal devices. The first should change a window
specific setting, where the latter should change only the default for new
windows.

@item
When attaching to a multiuser session, the user's @file{.screenrc} file is not
sourced. Each users personal settings have to be included in the 
@file{.screenrc} file from which the session is booted, or have to be 
changed manually.

@item
A weird imagination is most useful to gain full advantage of all the
features.
@end itemize

@node Reporting Bugs, Availability, Known Bugs, Bugs
@section Reporting Bugs
@cindex bug report

If you find a bug in @code{Screen}, please send electronic mail to
@w{@samp{screen@@uni-erlangen.de}}, and also to
@w{@samp{bug-gnu-utils@@prep.ai.mit.edu}}.  Include the version number
of @code{Screen} which you are using.  Also include in your message the
hardware and operating system, the compiler used to compile, a
description of the bug behavior, and the conditions that triggered the
bug. Please recompile @code{screen} with the @samp{-DDEBUG} options
enabled, reproduce the bug, and have a look at the debug output written to
the directory @file{/tmp/debug}. If necessary quote suspect passages from the
debug output and show the contents of your @file{config.h} if it matters.

@node Availability,  , Reporting Bugs, Bugs
@section Availability
@cindex availability

@code{Screen} is available under the @code{GNU} copyleft.

The latest official release of @code{screen} available via anonymous
ftp from @samp{prep.ai.mit.edu}, @samp{nic.funet.fi} or any other
@code{GNU} distribution site.  The home site of 
@code{screen} is @samp{ftp.uni-erlangen.de
(131.188.3.71)}, in the directory @file{pub/utilities/screen}.
The subdirectory @samp{private} contains the latest beta testing release.
If you want to help, send a note to screen@@uni-erlangen.de.

@node Installation, Concept Index, Bugs, Top
@chapter Installation
@cindex installation

Since @code{screen} uses pseudo-ttys, the select system call, and
UNIX-domain sockets/named pipes, it will not run under a system that
does not include these features of 4.2 and 4.3 BSD UNIX.

@menu
* Socket Directory::            Where screen stores its handle.
* Compiling Screen::
@end menu

@node Socket Directory,
@section Socket Directory
@cindex socket directory

The socket directory defaults either to @file{$HOME/.screen} or simply to 
@file{/tmp/screens} or preferably to @file{/usr/local/screens} chosen at 
compile-time. If @code{screen} is installed
setuid root, then the administrator should compile screen with an
adequate (not NFS mounted) @code{SOCKDIR}. If @code{screen} is not
running setuid-root, the user can specify any mode 700 directory in the
environment variable @code{$SCREENDIR}.

@node Compiling Screen,  , Socket Directory, Installation
@section Compiling Screen
@cindex compiling screen

To compile and install screen:

The @code{screen} package comes with a @code{GNU Autoconf} configuration 
script. Before you compile the package run 

@center @code{sh ./configure}

This will create a @file{config.h} and @file{Makefile} for your machine.
If @code{configure} fails for some reason, then look at the examples and
comments found in the @file{Makefile.in} and @file{config.h.in} templates.
Rename @file{config.status} to @file{config.status.@var{machine}} when
you want to keep configuration data for multiple architectures. Running
@code{sh ./config.status.@var{machine}} recreates your configuration 
significantly faster than rerunning @code{configure}. 
@*
Read through the "User Configuration" section of @file{config.h}, and verify
that it suits your needs.
A comment near the top of this section explains why it's best to
install screen setuid to root.
Check for the place for the global @file{screenrc}-file and for the socket
directory.
@*
Check the compiler used in @file{Makefile}, the prefix path where to install
@code{screen}. Then run

@center @code{make}

If @code{make} fails to produce one of the files @file{term.h}, @file{comm.h}
or @file{tty.c}, then use @code{@var{filename.x}.dist} instead.
For additional information about installation of @code{screen} refer to the
file @file{INSTALLATION}, coming with this package.

@node Concept Index, Command Index, Installation, Top
@unnumbered Concept Index

@printindex cp

@node Command Index, Keystroke Index, Concept Index, Top
@unnumbered Command Index

This is a list of all the commands supported by @code{screen}.

@printindex fn

@node Keystroke Index,  , Command Index, Top
@unnumbered Keystroke Index

This is a list of the default key bindings.

The leading escape character (@pxref{Command Character}) has been omitted
from the key sequences, since it is the same for all bindings.

@printindex ky

@shortcontents
@contents
@bye