Improved build.xml

[vimdoclet.git] / sample / java.lang.ProcessBuilder.txt

*java.lang.ProcessBuilder* *ProcessBuilder* This class is used to create operati

public final class ProcessBuilder
  extends    |java.lang.Object|

|java.lang.ProcessBuilder_Description|
|java.lang.ProcessBuilder_Fields|
|java.lang.ProcessBuilder_Constructors|
|java.lang.ProcessBuilder_Methods|

================================================================================

*java.lang.ProcessBuilder_Constructors*
|java.lang.ProcessBuilder(List)|Constructs a process builder with the specified
|java.lang.ProcessBuilder(String[])|Constructs a process builder with the speci

*java.lang.ProcessBuilder_Methods*
|java.lang.ProcessBuilder.command()|Returns this process builder's operating sy
|java.lang.ProcessBuilder.command(List)|Sets this process builder's operating s
|java.lang.ProcessBuilder.command(String[])|Sets this process builder's operati
|java.lang.ProcessBuilder.directory()|Returns this process builder's working di
|java.lang.ProcessBuilder.directory(File)|Sets this process builder's working d
|java.lang.ProcessBuilder.environment()|Returns a string map view of this proce
|java.lang.ProcessBuilder.redirectErrorStream()|Tells whether this process buil
|java.lang.ProcessBuilder.redirectErrorStream(boolean)|Sets this process builde
|java.lang.ProcessBuilder.start()|Starts a new process using the attributes of 

*java.lang.ProcessBuilder_Description*

This class is used to create operating system processes. 

Each ProcessBuilder instance manages a collection of process attributes. The 
(|java.lang.ProcessBuilder|) method creates a new (|java.lang.Process|) 
instance with those attributes. The (|java.lang.ProcessBuilder|) method can be 
invoked repeatedly from the same instance to create new subprocesses with 
identical or related attributes. 

Each process builder manages these process attributes: 



a command, a list of strings which signifies the external program file to be 
invoked and its arguments, if any. Which string lists represent a valid 
operating system command is system-dependent. For example, it is common for 
each conceptual argument to be an element in this list, but there are operating 
systems where programs are expected to tokenize command line strings themselves 
- on such a system a Java implementation might require commands to contain 
exactly two elements. 

an environment, which is a system-dependent mapping from variables to values. 
The initial value is a copy of the environment of the current process (see 
(|java.lang.System|) ). 

a working directory. The default value is the current working directory of the 
current process, usually the directory named by the system property user.dir. 

a redirectErrorStream property. Initially, this property is false, meaning that 
the standard output and error output of a subprocess are sent to two separate 
streams, which can be accessed using the (|java.lang.Process|) and 
(|java.lang.Process|) methods. If the value is set to true, the standard error 
is merged with the standard output. This makes it easier to correlate error 
messages with the corresponding output. In this case, the merged data can be 
read from the stream returned by (|java.lang.Process|) , while reading from the 
stream returned by (|java.lang.Process|) will get an immediate end of file. 



Modifying a process builder's attributes will affect processes subsequently 
started by that object's (|java.lang.ProcessBuilder|) method, but will never 
affect previously started processes or the Java process itself. 

Most error checking is performed by the (|java.lang.ProcessBuilder|) method. It 
is possible to modify the state of an object so that 
(|java.lang.ProcessBuilder|) will fail. For example, setting the command 
attribute to an empty list will not throw an exception unless 
(|java.lang.ProcessBuilder|) is invoked. 

Note that this class is not synchronized. If multiple threads access a 
ProcessBuilder instance concurrently, and at least one of the threads modifies 
one of the attributes structurally, it must be synchronized externally. 

Starting a new process which uses the default working directory and environment 
is easy: 



Process p = new ProcessBuilder("myCommand", "myArg").start(); 

Here is an example that starts a process with a modified working directory and 
environment: 



ProcessBuilder pb = new ProcessBuilder("myCommand", "myArg1", "myArg2"); 
Map<String, String> env = pb.environment(); env.put("VAR1", "myValue"); 
env.remove("OTHERVAR"); env.put("VAR2", env.get("VAR1") + "suffix"); 
pb.directory("myDir"); Process p = pb.start(); 

To start a process with an explicit set of environment variables, first call 
Map.clear()(|java.util.Map|) before adding environment variables. 


*java.lang.ProcessBuilder(List)*

public ProcessBuilder(java.util.List command)

Constructs a process builder with the specified operating system program and 
arguments. This constructor does not make a copy of the command list. 
Subsequent updates to the list will be reflected in the state of the process 
builder. It is not checked whether command corresponds to a valid operating 
system command. 

    command - The list containing the program and its arguments 

*java.lang.ProcessBuilder(String[])*

public ProcessBuilder(java.lang.String[] command)

Constructs a process builder with the specified operating system program and 
arguments. This is a convenience constructor that sets the process builder's 
command to a string list containing the same strings as the command array, in 
the same order. It is not checked whether command corresponds to a valid 
operating system command. 

    command - A string array containing the program and its arguments 

*java.lang.ProcessBuilder.command()*

public |java.util.List| command()

Returns this process builder's operating system program and arguments. The 
returned list is not a copy. Subsequent updates to the list will be reflected 
in the state of this process builder. 


    Returns: This process builder's program and its arguments 
*java.lang.ProcessBuilder.command(List)*

public |java.lang.ProcessBuilder| command(java.util.List command)

Sets this process builder's operating system program and arguments. This method 
does not make a copy of the command list. Subsequent updates to the list will 
be reflected in the state of the process builder. It is not checked whether 
command corresponds to a valid operating system command. 

    command - The list containing the program and its arguments 

    Returns: This process builder 
*java.lang.ProcessBuilder.command(String[])*

public |java.lang.ProcessBuilder| command(java.lang.String[] command)

Sets this process builder's operating system program and arguments. This is a 
convenience method that sets the command to a string list containing the same 
strings as the command array, in the same order. It is not checked whether 
command corresponds to a valid operating system command. 

    command - A string array containing the program and its arguments 

    Returns: This process builder 
*java.lang.ProcessBuilder.directory()*

public |java.io.File| directory()

Returns this process builder's working directory. 

Subprocesses subsequently started by this object's (|java.lang.ProcessBuilder|) 
method will use this as their working directory. The returned value may be null 
-- this means to use the working directory of the current Java process, usually 
the directory named by the system property user.dir, as the working directory 
of the child process. 


    Returns: This process builder's working directory 
*java.lang.ProcessBuilder.directory(File)*

public |java.lang.ProcessBuilder| directory(java.io.File directory)

Sets this process builder's working directory. 

Subprocesses subsequently started by this object's (|java.lang.ProcessBuilder|) 
method will use this as their working directory. The argument may be null -- 
this means to use the working directory of the current Java process, usually 
the directory named by the system property user.dir, as the working directory 
of the child process. 

    directory - The new working directory 

    Returns: This process builder 
*java.lang.ProcessBuilder.environment()*

public |java.util.Map| environment()

Returns a string map view of this process builder's environment. 

Whenever a process builder is created, the environment is initialized to a copy 
of the current process environment (see (|java.lang.System|) ). Subprocesses 
subsequently started by this object's (|java.lang.ProcessBuilder|) method will 
use this map as their environment. 

The returned object may be modified using ordinary Map(|java.util.Map|) 
operations. These modifications will be visible to subprocesses started via the 
(|java.lang.ProcessBuilder|) method. Two ProcessBuilder instances always 
contain independent process environments, so changes to the returned map will 
never be reflected in any other ProcessBuilder instance or the values returned 
by System.getenv(|java.lang.System|) . 

If the system does not support environment variables, an empty map is returned. 

The returned map does not permit null keys or values. Attempting to insert or 
query the presence of a null key or value will throw a 
(|java.lang.NullPointerException|) . Attempting to query the presence of a key 
or value which is not of type (|java.lang.String|) will throw a 
(|java.lang.ClassCastException|) . 

The behavior of the returned map is system-dependent. A system may not allow 
modifications to environment variables or may forbid certain variable names or 
values. For this reason, attempts to modify the map may fail with 
(|java.lang.UnsupportedOperationException|) or 
(|java.lang.IllegalArgumentException|) if the modification is not permitted by 
the operating system. 

Since the external format of environment variable names and values is 
system-dependent, there may not be a one-to-one mapping between them and Java's 
Unicode strings. Nevertheless, the map is implemented in such a way that 
environment variables which are not modified by Java code will have an 
unmodified native representation in the subprocess. 

The returned map and its collection views may not obey the general contract of 
the (|java.lang.Object|) and (|java.lang.Object|) methods. 

The returned map is typically case-sensitive on all platforms. 

If a security manager exists, its checkPermission(|java.lang.SecurityManager|) 
method is called with a (|java.lang.RuntimePermission|) ("getenv.*") 
permission. This may result in a (|java.lang.SecurityException|) being thrown. 

When passing information to a Java subprocess, system properties are generally 
preferred over environment variables. 


    Returns: This process builder's environment 
*java.lang.ProcessBuilder.redirectErrorStream()*

public boolean redirectErrorStream()

Tells whether this process builder merges standard error and standard output. 

If this property is true, then any error output generated by subprocesses 
subsequently started by this object's (|java.lang.ProcessBuilder|) method will 
be merged with the standard output, so that both can be read using the 
(|java.lang.Process|) method. This makes it easier to correlate error messages 
with the corresponding output. The initial value is false. 


    Returns: This process builder's redirectErrorStream property 
*java.lang.ProcessBuilder.redirectErrorStream(boolean)*

public |java.lang.ProcessBuilder| redirectErrorStream(boolean redirectErrorStream)

Sets this process builder's redirectErrorStream property. 

If this property is true, then any error output generated by subprocesses 
subsequently started by this object's (|java.lang.ProcessBuilder|) method will 
be merged with the standard output, so that both can be read using the 
(|java.lang.Process|) method. This makes it easier to correlate error messages 
with the corresponding output. The initial value is false. 

    redirectErrorStream - The new property value 

    Returns: This process builder 
*java.lang.ProcessBuilder.start()*

public |java.lang.Process| start()
  throws |java.io.IOException|
         
Starts a new process using the attributes of this process builder. 

The new process will invoke the command and arguments given by 
(|java.lang.ProcessBuilder|) , in a working directory as given by 
(|java.lang.ProcessBuilder|) , with a process environment as given by 
(|java.lang.ProcessBuilder|) . 

This method checks that the command is a valid operating system command. Which 
commands are valid is system-dependent, but at the very least the command must 
be a non-empty list of non-null strings. 

If there is a security manager, its checkExec(|java.lang.SecurityManager|) 
method is called with the first component of this object's command array as its 
argument. This may result in a (|java.lang.SecurityException|) being thrown. 

Starting an operating system process is highly system-dependent. Among the many 
things that can go wrong are: 

The operating system program file was not found. Access to the program file was 
denied. The working directory does not exist. 

In such cases an exception will be thrown. The exact nature of the exception is 
system-dependent, but it will always be a subclass of (|java.io.IOException|) . 

Subsequent modifications to this process builder will not affect the returned 
(|java.lang.Process|) . 


    Returns: A new {@link Process} object for managing the subprocess