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25 .\" $FreeBSD: src/lib/libstand/libstand.3,v 1.5.2.11 2002/06/26 19:14:43 schweikh Exp $
32 .Nd support library for standalone executables
37 provides a set of supporting functions for standalone
38 applications, mimicking where possible the standard
41 environment. The following sections group these functions by kind.
42 Unless specifically described here, see the corresponding section 3
43 manpages for the given functions.
45 String functions are available as documented in
53 .Fn malloc "size_t size"
58 bytes of memory from the heap using a best-fit algorithm.
64 Free the allocated object at
68 .Fn setheap "void *start" "void *limit"
71 Initialise the heap. This function must be called before calling
73 for the first time. The region between
77 will be used for the heap; attempting to allocate beyond this will result
84 Provides the behaviour of
86 ie. returns the highest point that the heap has reached. This value can
87 be used during testing to determine the actual heap usage. The
92 A set of functions are provided for manipulating a flat variable space similar
93 to the traditional shell-supported environment. Major enhancements are support
94 for set/unset hook functions.
98 .Fn getenv "const char *name"
102 .Fn setenv "const char *name" "char *value" "int overwrite"
106 .Fn putenv "const char *string"
110 .Fn unsetenv "const char *name"
113 These functions behave similarly to their standard library counterparts.
115 .Ft "struct env_var *"
116 .Fn env_getenv "const char *name"
119 Looks up a variable in the environment and returns its entire
123 .Fn env_setenv "const char *name" "int flags" "char *value" "ev_sethook_t sethook" "ev_unsethook_t unsethook"
126 Creates a new or sets an existing environment variable called
128 If creating a new variable, the
132 arguments may be specified.
134 The set hook is invoked whenever an attempt
135 is made to set the variable, unless the EV_NOHOOK flag is set. Typically
136 a set hook will validate the
138 argument, and then call
140 again with EV_NOHOOK set to actually save the value. The predefined function
142 may be specified to refuse all attempts to set a variable.
144 The unset hook is invoked when an attempt is made to unset a variable.
146 returns zero, the variable will be unset. The predefined function
148 may be used to prevent a variable being unset.
150 .Sh STANDARD LIBRARY SUPPORT
154 .Fn getopt "int argc" "char * const *argv" "const char *optstring"
158 .Fn strtol "const char *nptr" "char **endptr" "int base"
162 .Fn srandom "unsigned long seed"
170 .Fn strerror "int error"
173 Returns error messages for the subset of errno values supported by
175 .It Fn assert expression
181 .Fn setjmp "jmp_buf env"
185 .Fn longjmp "jmp_buf env" "int val"
192 respectively as there is no signal state to manipulate. Requires
202 Read characters from the console into
204 All of the standard cautions apply to this function.
207 .Fn ngets "char *buf" "size_t size"
212 - 1 characters from the console into
216 is less than 1, the function's behaviour is as for
220 .Fn fgetstr "char *buf" "int size" "int fd"
223 Read a line of at most
227 Line terminating characters are stripped, and the buffer is always nul
228 terminated. Returns the number of characters in
230 if successful, or -1 if a read error occurs.
233 .Fn printf "const char *fmt" "..."
237 .Fn vprintf "const char *fmt" "va_list ap"
241 .Fn sprintf "char *buf" "const char *fmt" "..."
245 .Fn vsprintf "char *buf" "const char *fmt" "va_list ap"
248 The *printf functions implement a subset of the standard
250 family functionality and some extensions. The following standard conversions
251 are supported: c,d,n,o,p,s,u,x. The following modifiers are supported:
252 +,-,#,*,0,field width,precision,l.
256 conversion is provided to decode error registers. Its usage is:
258 .Bd -ragged -offset indent
266 where <base> is the output expressed as a control character, eg. \e10 gives
267 octal, \e20 gives hex. Each <arg> is a sequence of characters, the first of
268 which gives the bit number to be inspected (origin 1) and the next characters
269 (up to a character less than 32) give the text to be displayed if the bit is set.
272 .Bd -ragged -offset indent
276 .Qq \e10\e2BITTWO\e1BITONE\en
280 would give the output
282 .Bd -ragged -offset indent
288 conversion provides a hexdump facility, eg.
290 .Bd -ragged -offset indent
296 .Qq XX:XX:XX:XX:XX:XX
298 .Bd -ragged -offset indent
308 .Sh CHARACTER TESTS AND CONVERSIONS
351 .Fn open "const char *path" "int flags"
354 Similar to the behaviour as specified in
356 except that file creation is not supported, so the mode parameter is not
359 argument may be one of O_RDONLY, O_WRONLY and O_RDWR (although no filesystems
360 currently support writing).
370 Close all open files.
373 .Fn read "int fd" "void *buf" "size_t len"
377 .Fn write "int fd" "void *buf" "size_t len"
380 (No filesystems currently support writing.)
383 .Fn lseek "int fd" "off_t offset" "int whence"
386 Files being automatically uncompressed during reading cannot seek backwards
387 from the current point.
390 .Fn stat "const char *path" "struct stat *sb"
394 .Fn fstat "int fd" "struct stat *sb"
401 functions only fill out the following fields in the
403 structure: st_mode,st_nlink,st_uid,st_gid,st_size. The
405 filesystem cannot provide meaningful values for this call, and the
407 filesystem always reports files having uid/gid of zero.
411 supplies a simple internal pager to ease reading the output of large commands.
418 Initialises the pager and tells it that the next line output will be the top of the
419 display. The environment variable LINES is consulted to determine the number of
420 lines to be displayed before pausing.
429 .Fn pager_output "char *lines"
432 Sends the lines in the nul-terminated buffer at
434 to the pager. Newline characters are counted in order to determine the number
435 of lines being output (wrapped lines are not accounted for).
437 will return zero when all of the lines have been output, or nonzero if the
438 display was paused and the user elected to quit.
441 .Fn pager_file "char *fname"
444 Attempts to open and display the file
446 Returns -1 on error, 0 at EOF, or 1 if the user elects to quit while reading.
455 Successive calls emit the characters in the sequence |,/,-,\\ followed by a
456 backspace in order to provide reassurance to the user.
458 .Sh REQUIRED LOW-LEVEL SUPPORT
459 The following resources are consumed by
461 - stack, heap, console and devices.
463 The stack must be established before
465 functions can be invoked. Stack requirements vary depending on the functions
466 and filesystems used by the consumer and the support layer functions detailed
469 The heap must be established before calling
475 Heap usage will vary depending on the number of simultaneously open files,
476 as well as client behaviour. Automatic decompression will allocate more
477 than 64K of data per open file.
479 Console access is performed via the
484 functions detailed below.
486 Device access is initiated via
488 and is performed through the
493 functions in the device switch structure that
497 The consumer must provide the following support functions:
504 Return a character from the console, used by
513 Returns nonzero if a character is waiting from the console.
519 Write a character to the console, used by
526 and thus by many other functions for debugging and informational output.
529 .Fn devopen "struct open_file *of" "const char *name" "char **file"
532 Open the appropriate device for the file named in
536 a pointer to the remaining body of
538 which does not refer to the device. The
542 will be set to point to the
544 structure for the opened device if successful. Device identifiers must
545 always precede the path component, but may otherwise be arbitrarily formatted.
548 and thus for all device-related I/O.
551 .Fn devclose "struct open_file *of"
553 Close the device allocated for
555 The device driver itself will already have been called for the close; this call
556 should clean up any allocation made by devopen only.
559 .Fn panic "const char *msg" "..."
562 Signal a fatal and unrecoverable error condition. The
567 .Sh INTERNAL FILESYSTEMS
568 Internal filesystems are enabled by the consumer exporting the array
569 .Vt struct fs_ops *file_system[] ,
570 which should be initialised with pointers
573 structures. The following filesystem handlers are supplied by
575 the consumer may supply other filesystems of their own:
576 .Bl -hang -width ".Va cd9660_fsops"
582 Linux ext2fs filesystem.
584 File access via TFTP.
588 ISO 9660 (CD-ROM) filesystem.
590 Stacked filesystem supporting gzipped files.
591 When trying the zipfs filesystem,
595 to the end of the filename, and then tries to locate the file using the other
596 filesystems. Placement of this filesystem in the
598 array determines whether gzipped files will be opened in preference to non-gzipped
599 files. It is only possible to seek a gzipped file forwards, and
603 on gzipped files will report an invalid length.
608 .Xr bzip2 1 Ns -compressed
614 pointers should be terminated with a NULL.
616 Devices are exported by the supporting code via the array
617 .Vt struct devsw *devsw[]
618 which is a NULL terminated array of pointers to device switch structures.
620 The lack of detailed memory usage data is unhelpful.
623 contains contributions from many sources, including:
638 .An Matthew Dillon Aq dillon@backplane.com
641 The reorganisation and port to
643 the environment functions and this manpage were written by
644 .An Mike Smith Aq msmith@FreeBSD.org .