1 .\" Copyright (c) Michael Smith
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25 .\" $FreeBSD: src/lib/libstand/libstand.3,v 1.5.2.11 2002/06/26 19:14:43 schweikh Exp $
26 .\" $DragonFly: src/lib/libstand/libstand.3,v 1.7 2007/09/14 19:47:03 swildner Exp $
28 .Dd September 13, 2004
33 .Nd support library for standalone executables
40 provides a set of supporting functions for standalone
41 applications, mimicking where possible the standard
44 environment. The following sections group these functions by kind.
45 Unless specifically described here, see the corresponding section 3
46 manpages for the given functions.
48 String functions are available as documented in
56 .Fn malloc "size_t size"
61 bytes of memory from the heap using a best-fit algorithm.
67 Free the allocated object at
71 .Fn setheap "void *start" "void *limit"
74 Initialise the heap. This function must be called before calling
76 for the first time. The region between
80 will be used for the heap; attempting to allocate beyond this will result
87 Provides the behaviour of
89 ie. returns the highest point that the heap has reached. This value can
90 be used during testing to determine the actual heap usage. The
95 A set of functions are provided for manipulating a flat variable space similar
96 to the traditional shell-supported environment. Major enhancements are support
97 for set/unset hook functions.
101 .Fn getenv "const char *name"
105 .Fn setenv "const char *name" "char *value" "int overwrite"
109 .Fn putenv "const char *string"
113 .Fn unsetenv "const char *name"
116 These functions behave similarly to their standard library counterparts.
118 .Ft "struct env_var *"
119 .Fn env_getenv "const char *name"
122 Looks up a variable in the environment and returns its entire
126 .Fn env_setenv "const char *name" "int flags" "char *value" "ev_sethook_t sethook" "ev_unsethook_t unsethook"
129 Creates a new or sets an existing environment variable called
131 If creating a new variable, the
135 arguments may be specified.
137 The set hook is invoked whenever an attempt
138 is made to set the variable, unless the EV_NOHOOK flag is set. Typically
139 a set hook will validate the
141 argument, and then call
143 again with EV_NOHOOK set to actually save the value. The predefined function
145 may be specified to refuse all attempts to set a variable.
147 The unset hook is invoked when an attempt is made to unset a variable.
149 returns zero, the variable will be unset. The predefined function
151 may be used to prevent a variable being unset.
153 .Sh STANDARD LIBRARY SUPPORT
157 .Fn getopt "int argc" "char * const *argv" "const char *optstring"
161 .Fn strtol "const char *nptr" "char **endptr" "int base"
165 .Fn srandom "unsigned long seed"
173 .Fn strerror "int error"
176 Returns error messages for the subset of
180 .It Fn assert expression
186 .Fn setjmp "jmp_buf env"
190 .Fn longjmp "jmp_buf env" "int val"
197 respectively as there is no signal state to manipulate. Requires
207 Read characters from the console into
209 All of the standard cautions apply to this function.
212 .Fn ngets "char *buf" "size_t size"
217 - 1 characters from the console into
221 is less than 1, the function's behaviour is as for
225 .Fn fgetstr "char *buf" "int size" "int fd"
228 Read a line of at most
232 Line terminating characters are stripped, and the buffer is always nul
233 terminated. Returns the number of characters in
235 if successful, or -1 if a read error occurs.
238 .Fn printf "const char *fmt" "..."
242 .Fn vprintf "const char *fmt" "va_list ap"
246 .Fn sprintf "char *buf" "const char *fmt" "..."
250 .Fn vsprintf "char *buf" "const char *fmt" "va_list ap"
253 The *printf functions implement a subset of the standard
255 family functionality and some extensions. The following standard conversions
256 are supported: c,d,n,o,p,s,u,x. The following modifiers are supported:
257 +,-,#,*,0,field width,precision,l.
261 conversion is provided to decode error registers. Its usage is:
263 .Bd -ragged -offset indent
271 where <base> is the output expressed as a control character, eg. \e10 gives
272 octal, \e20 gives hex. Each <arg> is a sequence of characters, the first of
273 which gives the bit number to be inspected (origin 1) and the next characters
274 (up to a character less than 32) give the text to be displayed if the bit is set.
277 .Bd -ragged -offset indent
281 .Qq \e10\e2BITTWO\e1BITONE\en
285 would give the output
287 .Bd -ragged -offset indent
293 conversion provides a hexdump facility, eg.
295 .Bd -ragged -offset indent
301 .Qq XX:XX:XX:XX:XX:XX
303 .Bd -ragged -offset indent
313 .Sh CHARACTER TESTS AND CONVERSIONS
356 .Fn open "const char *path" "int flags"
359 Similar to the behaviour as specified in
361 except that file creation is not supported, so the mode parameter is not
364 argument may be one of O_RDONLY, O_WRONLY and O_RDWR (although no filesystems
365 currently support writing).
375 Close all open files.
378 .Fn read "int fd" "void *buf" "size_t len"
382 .Fn write "int fd" "void *buf" "size_t len"
385 (No filesystems currently support writing.)
388 .Fn lseek "int fd" "off_t offset" "int whence"
391 Files being automatically uncompressed during reading cannot seek backwards
392 from the current point.
395 .Fn stat "const char *path" "struct stat *sb"
399 .Fn fstat "int fd" "struct stat *sb"
406 functions only fill out the following fields in the
408 structure: st_mode,st_nlink,st_uid,st_gid,st_size. The
410 filesystem cannot provide meaningful values for this call, and the
412 filesystem always reports files having uid/gid of zero.
416 supplies a simple internal pager to ease reading the output of large commands.
423 Initialises the pager and tells it that the next line output will be the top of the
424 display. The environment variable LINES is consulted to determine the number of
425 lines to be displayed before pausing.
434 .Fn pager_output "char *lines"
437 Sends the lines in the nul-terminated buffer at
439 to the pager. Newline characters are counted in order to determine the number
440 of lines being output (wrapped lines are not accounted for).
442 will return zero when all of the lines have been output, or nonzero if the
443 display was paused and the user elected to quit.
446 .Fn pager_file "char *fname"
449 Attempts to open and display the file
451 Returns -1 on error, 0 at EOF, or 1 if the user elects to quit while reading.
460 Successive calls emit the characters in the sequence |,/,-,\\ followed by a
461 backspace in order to provide reassurance to the user.
463 .Sh REQUIRED LOW-LEVEL SUPPORT
464 The following resources are consumed by
466 - stack, heap, console and devices.
468 The stack must be established before
470 functions can be invoked. Stack requirements vary depending on the functions
471 and filesystems used by the consumer and the support layer functions detailed
474 The heap must be established before calling
480 Heap usage will vary depending on the number of simultaneously open files,
481 as well as client behaviour. Automatic decompression will allocate more
482 than 64K of data per open file.
484 Console access is performed via the
489 functions detailed below.
491 Device access is initiated via
493 and is performed through the
498 functions in the device switch structure that
502 The consumer must provide the following support functions:
509 Return a character from the console, used by
518 Returns nonzero if a character is waiting from the console.
524 Write a character to the console, used by
531 and thus by many other functions for debugging and informational output.
534 .Fn devopen "struct open_file *of" "const char *name" "char **file"
537 Open the appropriate device for the file named in
541 a pointer to the remaining body of
543 which does not refer to the device. The
547 will be set to point to the
549 structure for the opened device if successful. Device identifiers must
550 always precede the path component, but may otherwise be arbitrarily formatted.
553 and thus for all device-related I/O.
556 .Fn devclose "struct open_file *of"
558 Close the device allocated for
560 The device driver itself will already have been called for the close; this call
561 should clean up any allocation made by devopen only.
564 .Fn panic "const char *msg" "..."
567 Signal a fatal and unrecoverable error condition. The
572 .Sh INTERNAL FILESYSTEMS
573 Internal filesystems are enabled by the consumer exporting the array
574 .Vt struct fs_ops *file_system[] ,
575 which should be initialised with pointers
578 structures. The following filesystem handlers are supplied by
580 the consumer may supply other filesystems of their own:
581 .Bl -hang -width ".Va cd9660_fsops"
587 Linux ext2fs filesystem.
589 File access via TFTP.
593 ISO 9660 (CD-ROM) filesystem.
595 Stacked filesystem supporting gzipped files.
596 When trying the zipfs filesystem,
600 to the end of the filename, and then tries to locate the file using the other
601 filesystems. Placement of this filesystem in the
603 array determines whether gzipped files will be opened in preference to non-gzipped
604 files. It is only possible to seek a gzipped file forwards, and
608 on gzipped files will report an invalid length.
613 .Xr bzip2 1 Ns -compressed
619 pointers should be terminated with a NULL.
621 Devices are exported by the supporting code via the array
622 .Vt struct devsw *devsw[]
623 which is a NULL terminated array of pointers to device switch structures.
626 contains contributions from many sources, including:
641 .An Matthew Dillon Aq dillon@backplane.com
644 The reorganisation and port to
646 the environment functions and this manpage were written by
647 .An Mike Smith Aq msmith@FreeBSD.org .
649 The lack of detailed memory usage data is unhelpful.