2 @c This is part of the GNU Guile Reference Manual.
3 @c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2007,
4 @c 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
5 @c See the file guile.texi for copying conditions.
8 @section @acronym{POSIX} System Calls and Networking
12 * Conventions:: Conventions employed by the POSIX interface.
13 * Ports and File Descriptors:: Scheme ``ports'' and Unix file descriptors
14 have different representations.
15 * File System:: stat, chown, chmod, etc.
16 * User Information:: Retrieving a user's GECOS (/etc/passwd) entry.
17 * Time:: gettimeofday, localtime, strftime, etc.
18 * Runtime Environment:: Accessing and modifying Guile's environment.
19 * Processes:: getuid, getpid, etc.
20 * Signals:: sigaction, kill, pause, alarm, setitimer, etc.
21 * Terminals and Ptys:: ttyname, tcsetpgrp, etc.
22 * Pipes:: Communicating data between processes.
23 * Networking:: gethostbyaddr, getnetent, socket, bind, listen.
24 * System Identification:: Obtaining information about the system.
25 * Locales:: setlocale, etc.
30 @subsection @acronym{POSIX} Interface Conventions
32 These interfaces provide access to operating system facilities.
33 They provide a simple wrapping around the underlying C interfaces
34 to make usage from Scheme more convenient. They are also used
35 to implement the Guile port of scsh (@pxref{The Scheme shell (scsh)}).
37 Generally there is a single procedure for each corresponding Unix
38 facility. There are some exceptions, such as procedures implemented for
39 speed and convenience in Scheme with no primitive Unix equivalent,
40 e.g.@: @code{copy-file}.
42 The interfaces are intended as far as possible to be portable across
43 different versions of Unix. In some cases procedures which can't be
44 implemented on particular systems may become no-ops, or perform limited
45 actions. In other cases they may throw errors.
47 General naming conventions are as follows:
51 The Scheme name is often identical to the name of the underlying Unix
54 Underscores in Unix procedure names are converted to hyphens.
56 Procedures which destructively modify Scheme data have exclamation
57 marks appended, e.g., @code{recv!}.
59 Predicates (returning only @code{#t} or @code{#f}) have question marks
60 appended, e.g., @code{access?}.
62 Some names are changed to avoid conflict with dissimilar interfaces
63 defined by scsh, e.g., @code{primitive-fork}.
65 Unix preprocessor names such as @code{EPERM} or @code{R_OK} are converted
66 to Scheme variables of the same name (underscores are not replaced
70 Unexpected conditions are generally handled by raising exceptions.
71 There are a few procedures which return a special value if they don't
72 succeed, e.g., @code{getenv} returns @code{#f} if it the requested
73 string is not found in the environment. These cases are noted in
76 For ways to deal with exceptions, see @ref{Exceptions}.
79 Errors which the C library would report by returning a null pointer or
80 through some other means are reported by raising a @code{system-error}
81 exception with @code{scm-error} (@pxref{Error Reporting}). The
82 @var{data} parameter is a list containing the Unix @code{errno} value
83 (an integer). For example,
86 (define (my-handler key func fmt fmtargs data)
87 (display key) (newline)
88 (display func) (newline)
89 (apply format #t fmt fmtargs) (newline)
90 (display data) (newline))
93 (lambda () (dup2 -123 -456))
105 @defun system-error-errno arglist
107 Return the @code{errno} value from a list which is the arguments to an
108 exception handler. If the exception is not a @code{system-error},
109 then the return is @code{#f}. For example,
115 (mkdir "/this-ought-to-fail-if-I'm-not-root"))
117 (let ((errno (system-error-errno stuff)))
120 (display "You're not allowed to do that."))
122 (display "Already exists."))
124 (display (strerror errno))))
130 @node Ports and File Descriptors
131 @subsection Ports and File Descriptors
132 @cindex file descriptor
134 Conventions generally follow those of scsh, @ref{The Scheme shell (scsh)}.
136 File ports are implemented using low-level operating system I/O
137 facilities, with optional buffering to improve efficiency; see
140 Note that some procedures (e.g., @code{recv!}) will accept ports as
141 arguments, but will actually operate directly on the file descriptor
142 underlying the port. Any port buffering is ignored, including the
143 buffer which implements @code{peek-char} and @code{unread-char}.
145 The @code{force-output} and @code{drain-input} procedures can be used
146 to clear the buffers.
148 Each open file port has an associated operating system file descriptor.
149 File descriptors are generally not useful in Scheme programs; however
150 they may be needed when interfacing with foreign code and the Unix
153 A file descriptor can be extracted from a port and a new port can be
154 created from a file descriptor. However a file descriptor is just an
155 integer and the garbage collector doesn't recognize it as a reference
156 to the port. If all other references to the port were dropped, then
157 it's likely that the garbage collector would free the port, with the
158 side-effect of closing the file descriptor prematurely.
160 To assist the programmer in avoiding this problem, each port has an
161 associated @dfn{revealed count} which can be used to keep track of how many
162 times the underlying file descriptor has been stored in other places.
163 If a port's revealed count is greater than zero, the file descriptor
164 will not be closed when the port is garbage collected. A programmer
165 can therefore ensure that the revealed count will be greater than
166 zero if the file descriptor is needed elsewhere.
168 For the simple case where a file descriptor is ``imported'' once to become
169 a port, it does not matter if the file descriptor is closed when the
170 port is garbage collected. There is no need to maintain a revealed
171 count. Likewise when ``exporting'' a file descriptor to the external
172 environment, setting the revealed count is not required provided the
173 port is kept open (i.e., is pointed to by a live Scheme binding) while
174 the file descriptor is in use.
176 To correspond with traditional Unix behaviour, three file descriptors
177 (0, 1, and 2) are automatically imported when a program starts up and
178 assigned to the initial values of the current/standard input, output,
179 and error ports, respectively. The revealed count for each is
180 initially set to one, so that dropping references to one of these
181 ports will not result in its garbage collection: it could be retrieved
182 with @code{fdopen} or @code{fdes->ports}.
184 @deffn {Scheme Procedure} port-revealed port
185 @deffnx {C Function} scm_port_revealed (port)
186 Return the revealed count for @var{port}.
189 @deffn {Scheme Procedure} set-port-revealed! port rcount
190 @deffnx {C Function} scm_set_port_revealed_x (port, rcount)
191 Sets the revealed count for a @var{port} to @var{rcount}.
192 The return value is unspecified.
195 @deffn {Scheme Procedure} fileno port
196 @deffnx {C Function} scm_fileno (port)
197 Return the integer file descriptor underlying @var{port}. Does
198 not change its revealed count.
201 @deffn {Scheme Procedure} port->fdes port
202 Returns the integer file descriptor underlying @var{port}. As a
203 side effect the revealed count of @var{port} is incremented.
206 @deffn {Scheme Procedure} fdopen fdes modes
207 @deffnx {C Function} scm_fdopen (fdes, modes)
208 Return a new port based on the file descriptor @var{fdes}. Modes are
209 given by the string @var{modes}. The revealed count of the port is
210 initialized to zero. The @var{modes} string is the same as that
211 accepted by @code{open-file} (@pxref{File Ports, open-file}).
214 @deffn {Scheme Procedure} fdes->ports fdes
215 @deffnx {C Function} scm_fdes_to_ports (fdes)
216 Return a list of existing ports which have @var{fdes} as an
217 underlying file descriptor, without changing their revealed
221 @deffn {Scheme Procedure} fdes->inport fdes
222 Returns an existing input port which has @var{fdes} as its underlying file
223 descriptor, if one exists, and increments its revealed count.
224 Otherwise, returns a new input port with a revealed count of 1.
227 @deffn {Scheme Procedure} fdes->outport fdes
228 Returns an existing output port which has @var{fdes} as its underlying file
229 descriptor, if one exists, and increments its revealed count.
230 Otherwise, returns a new output port with a revealed count of 1.
233 @deffn {Scheme Procedure} primitive-move->fdes port fdes
234 @deffnx {C Function} scm_primitive_move_to_fdes (port, fdes)
235 Moves the underlying file descriptor for @var{port} to the integer
236 value @var{fdes} without changing the revealed count of @var{port}.
237 Any other ports already using this descriptor will be automatically
238 shifted to new descriptors and their revealed counts reset to zero.
239 The return value is @code{#f} if the file descriptor already had the
240 required value or @code{#t} if it was moved.
243 @deffn {Scheme Procedure} move->fdes port fdes
244 Moves the underlying file descriptor for @var{port} to the integer
245 value @var{fdes} and sets its revealed count to one. Any other ports
246 already using this descriptor will be automatically
247 shifted to new descriptors and their revealed counts reset to zero.
248 The return value is unspecified.
251 @deffn {Scheme Procedure} release-port-handle port
252 Decrements the revealed count for a port.
255 @deffn {Scheme Procedure} fsync port_or_fd
256 @deffnx {C Function} scm_fsync (port_or_fd)
257 Copies any unwritten data for the specified output file descriptor to disk.
258 If @var{port_or_fd} is a port, its buffer is flushed before the underlying
259 file descriptor is fsync'd.
260 The return value is unspecified.
263 @deffn {Scheme Procedure} open path flags [mode]
264 @deffnx {C Function} scm_open (path, flags, mode)
265 Open the file named by @var{path} for reading and/or writing.
266 @var{flags} is an integer specifying how the file should be opened.
267 @var{mode} is an integer specifying the permission bits of the file,
268 if it needs to be created, before the umask (@pxref{Processes}) is
269 applied. The default is 666 (Unix itself has no default).
271 @var{flags} can be constructed by combining variables using @code{logior}.
275 Open the file read-only.
278 Open the file write-only.
281 Open the file read/write.
284 Append to the file instead of truncating.
287 Create the file if it does not already exist.
290 @xref{File Status Flags,,,libc,The GNU C Library Reference Manual},
291 for additional flags.
294 @deffn {Scheme Procedure} open-fdes path flags [mode]
295 @deffnx {C Function} scm_open_fdes (path, flags, mode)
296 Similar to @code{open} but return a file descriptor instead of
300 @deffn {Scheme Procedure} close fd_or_port
301 @deffnx {C Function} scm_close (fd_or_port)
302 Similar to @code{close-port} (@pxref{Closing, close-port}),
303 but also works on file descriptors. A side
304 effect of closing a file descriptor is that any ports using that file
305 descriptor are moved to a different file descriptor and have
306 their revealed counts set to zero.
309 @deffn {Scheme Procedure} close-fdes fd
310 @deffnx {C Function} scm_close_fdes (fd)
311 A simple wrapper for the @code{close} system call. Close file
312 descriptor @var{fd}, which must be an integer. Unlike @code{close},
313 the file descriptor will be closed even if a port is using it. The
314 return value is unspecified.
317 @deffn {Scheme Procedure} unread-char char [port]
318 @deffnx {C Function} scm_unread_char (char, port)
319 Place @var{char} in @var{port} so that it will be read by the next
320 read operation on that port. If called multiple times, the unread
321 characters will be read again in ``last-in, first-out'' order (i.e.@:
322 a stack). If @var{port} is not supplied, the current input port is
326 @deffn {Scheme Procedure} unread-string str port
327 Place the string @var{str} in @var{port} so that its characters will be
328 read in subsequent read operations. If called multiple times, the
329 unread characters will be read again in last-in first-out order. If
330 @var{port} is not supplied, the current-input-port is used.
333 @deffn {Scheme Procedure} pipe
334 @deffnx {C Function} scm_pipe ()
336 Return a newly created pipe: a pair of ports which are linked
337 together on the local machine. The @acronym{CAR} is the input
338 port and the @acronym{CDR} is the output port. Data written (and
339 flushed) to the output port can be read from the input port.
340 Pipes are commonly used for communication with a newly forked
341 child process. The need to flush the output port can be
342 avoided by making it unbuffered using @code{setvbuf}.
345 A write of up to @code{PIPE_BUF} many bytes to a pipe is atomic,
346 meaning when done it goes into the pipe instantaneously and as a
347 contiguous block (@pxref{Pipe Atomicity,, Atomicity of Pipe I/O, libc,
348 The GNU C Library Reference Manual}).
351 Note that the output port is likely to block if too much data has been
352 written but not yet read from the input port. Typically the capacity
353 is @code{PIPE_BUF} bytes.
356 The next group of procedures perform a @code{dup2}
357 system call, if @var{newfd} (an
358 integer) is supplied, otherwise a @code{dup}. The file descriptor to be
359 duplicated can be supplied as an integer or contained in a port. The
360 type of value returned varies depending on which procedure is used.
362 All procedures also have the side effect when performing @code{dup2} that any
363 ports using @var{newfd} are moved to a different file descriptor and have
364 their revealed counts set to zero.
366 @deffn {Scheme Procedure} dup->fdes fd_or_port [fd]
367 @deffnx {C Function} scm_dup_to_fdes (fd_or_port, fd)
368 Return a new integer file descriptor referring to the open file
369 designated by @var{fd_or_port}, which must be either an open
370 file port or a file descriptor.
373 @deffn {Scheme Procedure} dup->inport port/fd [newfd]
374 Returns a new input port using the new file descriptor.
377 @deffn {Scheme Procedure} dup->outport port/fd [newfd]
378 Returns a new output port using the new file descriptor.
381 @deffn {Scheme Procedure} dup port/fd [newfd]
382 Returns a new port if @var{port/fd} is a port, with the same mode as the
383 supplied port, otherwise returns an integer file descriptor.
386 @deffn {Scheme Procedure} dup->port port/fd mode [newfd]
387 Returns a new port using the new file descriptor. @var{mode} supplies a
388 mode string for the port (@pxref{File Ports, open-file}).
391 @deffn {Scheme Procedure} duplicate-port port modes
392 Returns a new port which is opened on a duplicate of the file
393 descriptor underlying @var{port}, with mode string @var{modes}
394 as for @ref{File Ports, open-file}. The two ports
395 will share a file position and file status flags.
397 Unexpected behaviour can result if both ports are subsequently used
398 and the original and/or duplicate ports are buffered.
399 The mode string can include @code{0} to obtain an unbuffered duplicate
402 This procedure is equivalent to @code{(dup->port @var{port} @var{modes})}.
405 @deffn {Scheme Procedure} redirect-port old_port new_port
406 @deffnx {C Function} scm_redirect_port (old_port, new_port)
407 This procedure takes two ports and duplicates the underlying file
408 descriptor from @var{old_port} into @var{new_port}. The
409 current file descriptor in @var{new_port} will be closed.
410 After the redirection the two ports will share a file position
411 and file status flags.
413 The return value is unspecified.
415 Unexpected behaviour can result if both ports are subsequently used
416 and the original and/or duplicate ports are buffered.
418 This procedure does not have any side effects on other ports or
422 @deffn {Scheme Procedure} dup2 oldfd newfd
423 @deffnx {C Function} scm_dup2 (oldfd, newfd)
424 A simple wrapper for the @code{dup2} system call.
425 Copies the file descriptor @var{oldfd} to descriptor
426 number @var{newfd}, replacing the previous meaning
427 of @var{newfd}. Both @var{oldfd} and @var{newfd} must
429 Unlike for @code{dup->fdes} or @code{primitive-move->fdes}, no attempt
430 is made to move away ports which are using @var{newfd}.
431 The return value is unspecified.
434 @deffn {Scheme Procedure} port-mode port
435 Return the port modes associated with the open port @var{port}.
436 These will not necessarily be identical to the modes used when
437 the port was opened, since modes such as ``append'' which are
438 used only during port creation are not retained.
441 @deffn {Scheme Procedure} port-for-each proc
442 @deffnx {C Function} scm_port_for_each (SCM proc)
443 @deffnx {C Function} scm_c_port_for_each (void (*proc)(void *, SCM), void *data)
444 Apply @var{proc} to each port in the Guile port table
445 (FIXME: what is the Guile port table?)
446 in turn. The return value is unspecified. More specifically,
447 @var{proc} is applied exactly once to every port that exists in the
448 system at the time @code{port-for-each} is invoked. Changes to the
449 port table while @code{port-for-each} is running have no effect as far
450 as @code{port-for-each} is concerned.
452 The C function @code{scm_port_for_each} takes a Scheme procedure
453 encoded as a @code{SCM} value, while @code{scm_c_port_for_each} takes
454 a pointer to a C function and passes along a arbitrary @var{data}
458 @deffn {Scheme Procedure} setvbuf port mode [size]
459 @deffnx {C Function} scm_setvbuf (port, mode, size)
460 @cindex port buffering
461 Set the buffering mode for @var{port}. @var{mode} can be:
470 block buffered, using a newly allocated buffer of @var{size} bytes.
471 If @var{size} is omitted, a default size will be used.
475 @deffn {Scheme Procedure} fcntl port/fd cmd [value]
476 @deffnx {C Function} scm_fcntl (object, cmd, value)
477 Apply @var{cmd} on @var{port/fd}, either a port or file descriptor.
478 The @var{value} argument is used by the @code{SET} commands described
479 below, it's an integer value.
481 Values for @var{cmd} are:
484 Duplicate the file descriptor, the same as @code{dup->fdes} above
490 Get or set flags associated with the file descriptor. The only flag
494 ``Close on exec'', meaning the file descriptor will be closed on an
495 @code{exec} call (a successful such call). For example to set that
499 (fcntl port F_SETFD FD_CLOEXEC)
502 Or better, set it but leave any other possible future flags unchanged,
505 (fcntl port F_SETFD (logior FD_CLOEXEC
506 (fcntl port F_GETFD)))
513 Get or set flags associated with the open file. These flags are
514 @code{O_RDONLY} etc described under @code{open} above.
516 A common use is to set @code{O_NONBLOCK} on a network socket. The
517 following sets that flag, and leaves other flags unchanged.
520 (fcntl sock F_SETFL (logior O_NONBLOCK
521 (fcntl sock F_GETFL)))
527 Get or set the process ID of a socket's owner, for @code{SIGIO} signals.
531 @deffn {Scheme Procedure} flock file operation
532 @deffnx {C Function} scm_flock (file, operation)
534 Apply or remove an advisory lock on an open file.
535 @var{operation} specifies the action to be done:
538 Shared lock. More than one process may hold a shared lock
539 for a given file at a given time.
542 Exclusive lock. Only one process may hold an exclusive lock
543 for a given file at a given time.
549 Don't block when locking. This is combined with one of the other
550 operations using @code{logior} (@pxref{Bitwise Operations}). If
551 @code{flock} would block an @code{EWOULDBLOCK} error is thrown
552 (@pxref{Conventions}).
555 The return value is not specified. @var{file} may be an open
556 file descriptor or an open file descriptor port.
558 Note that @code{flock} does not lock files across NFS.
561 @deffn {Scheme Procedure} select reads writes excepts [secs [usecs]]
562 @deffnx {C Function} scm_select (reads, writes, excepts, secs, usecs)
563 This procedure has a variety of uses: waiting for the ability
564 to provide input, accept output, or the existence of
565 exceptional conditions on a collection of ports or file
566 descriptors, or waiting for a timeout to occur.
567 It also returns if interrupted by a signal.
569 @var{reads}, @var{writes} and @var{excepts} can be lists or
570 vectors, with each member a port or a file descriptor.
571 The value returned is a list of three corresponding
572 lists or vectors containing only the members which meet the
573 specified requirement. The ability of port buffers to
574 provide input or accept output is taken into account.
575 Ordering of the input lists or vectors is not preserved.
577 The optional arguments @var{secs} and @var{usecs} specify the
578 timeout. Either @var{secs} can be specified alone, as
579 either an integer or a real number, or both @var{secs} and
580 @var{usecs} can be specified as integers, in which case
581 @var{usecs} is an additional timeout expressed in
582 microseconds. If @var{secs} is omitted or is @code{#f} then
583 select will wait for as long as it takes for one of the other
584 conditions to be satisfied.
586 The scsh version of @code{select} differs as follows:
587 Only vectors are accepted for the first three arguments.
588 The @var{usecs} argument is not supported.
589 Multiple values are returned instead of a list.
590 Duplicates in the input vectors appear only once in output.
591 An additional @code{select!} interface is provided.
595 @subsection File System
598 These procedures allow querying and setting file system attributes
600 permissions, sizes and types of files); deleting, copying, renaming and
601 linking files; creating and removing directories and querying their
602 contents; syncing the file system and creating special files.
604 @deffn {Scheme Procedure} access? path how
605 @deffnx {C Function} scm_access (path, how)
606 Test accessibility of a file under the real UID and GID of the calling
607 process. The return is @code{#t} if @var{path} exists and the
608 permissions requested by @var{how} are all allowed, or @code{#f} if
611 @var{how} is an integer which is one of the following values, or a
612 bitwise-OR (@code{logior}) of multiple values.
615 Test for read permission.
618 Test for write permission.
621 Test for execute permission.
624 Test for existence of the file. This is implied by each of the other
625 tests, so there's no need to combine it with them.
628 It's important to note that @code{access?} does not simply indicate
629 what will happen on attempting to read or write a file. In normal
630 circumstances it does, but in a set-UID or set-GID program it doesn't
631 because @code{access?} tests the real ID, whereas an open or execute
632 attempt uses the effective ID.
634 A program which will never run set-UID/GID can ignore the difference
635 between real and effective IDs, but for maximum generality, especially
636 in library functions, it's best not to use @code{access?} to predict
637 the result of an open or execute, instead simply attempt that and
640 The main use for @code{access?} is to let a set-UID/GID program
641 determine what the invoking user would have been allowed to do,
642 without the greater (or perhaps lesser) privileges afforded by the
643 effective ID. For more on this, see @ref{Testing File Access,,, libc,
644 The GNU C Library Reference Manual}.
648 @deffn {Scheme Procedure} stat object
649 @deffnx {C Function} scm_stat (object)
650 Return an object containing various information about the file
651 determined by @var{object}. @var{object} can be a string containing
652 a file name or a port or integer file descriptor which is open
653 on a file (in which case @code{fstat} is used as the underlying
656 The object returned by @code{stat} can be passed as a single
657 parameter to the following procedures, all of which return
660 @deffn {Scheme Procedure} stat:dev st
661 The device number containing the file.
663 @deffn {Scheme Procedure} stat:ino st
664 The file serial number, which distinguishes this file from all
665 other files on the same device.
667 @deffn {Scheme Procedure} stat:mode st
668 The mode of the file. This is an integer which incorporates file type
669 information and file permission bits. See also @code{stat:type} and
670 @code{stat:perms} below.
672 @deffn {Scheme Procedure} stat:nlink st
673 The number of hard links to the file.
675 @deffn {Scheme Procedure} stat:uid st
676 The user ID of the file's owner.
678 @deffn {Scheme Procedure} stat:gid st
679 The group ID of the file.
681 @deffn {Scheme Procedure} stat:rdev st
682 Device ID; this entry is defined only for character or block special
683 files. On some systems this field is not available at all, in which
684 case @code{stat:rdev} returns @code{#f}.
686 @deffn {Scheme Procedure} stat:size st
687 The size of a regular file in bytes.
689 @deffn {Scheme Procedure} stat:atime st
690 The last access time for the file, in seconds.
692 @deffn {Scheme Procedure} stat:mtime st
693 The last modification time for the file, in seconds.
695 @deffn {Scheme Procedure} stat:ctime st
696 The last modification time for the attributes of the file, in seconds.
698 @deffn {Scheme Procedure} stat:atimensec st
699 @deffnx {Scheme Procedure} stat:mtimensec st
700 @deffnx {Scheme Procedure} stat:ctimensec st
701 The fractional part of a file's access, modification, or attribute modification
702 time, in nanoseconds. Nanosecond timestamps are only available on some operating
703 systems and file systems. If Guile cannot retrieve nanosecond-level timestamps
704 for a file, these fields will be set to 0.
706 @deffn {Scheme Procedure} stat:blksize st
707 The optimal block size for reading or writing the file, in bytes. On
708 some systems this field is not available, in which case
709 @code{stat:blksize} returns a sensible suggested block size.
711 @deffn {Scheme Procedure} stat:blocks st
712 The amount of disk space that the file occupies measured in units of
713 512 byte blocks. On some systems this field is not available, in
714 which case @code{stat:blocks} returns @code{#f}.
717 In addition, the following procedures return the information
718 from @code{stat:mode} in a more convenient form:
720 @deffn {Scheme Procedure} stat:type st
721 A symbol representing the type of file. Possible values are
722 @samp{regular}, @samp{directory}, @samp{symlink},
723 @samp{block-special}, @samp{char-special}, @samp{fifo}, @samp{socket},
726 @deffn {Scheme Procedure} stat:perms st
727 An integer representing the access permission bits.
731 @deffn {Scheme Procedure} lstat path
732 @deffnx {C Function} scm_lstat (path)
733 Similar to @code{stat}, but does not follow symbolic links, i.e.,
734 it will return information about a symbolic link itself, not the
735 file it points to. @var{path} must be a string.
738 @deffn {Scheme Procedure} readlink path
739 @deffnx {C Function} scm_readlink (path)
740 Return the value of the symbolic link named by @var{path} (a
741 string), i.e., the file that the link points to.
746 @deffn {Scheme Procedure} chown object owner group
747 @deffnx {C Function} scm_chown (object, owner, group)
748 Change the ownership and group of the file referred to by @var{object}
749 to the integer values @var{owner} and @var{group}. @var{object} can
750 be a string containing a file name or, if the platform supports
751 @code{fchown} (@pxref{File Owner,,,libc,The GNU C Library Reference
752 Manual}), a port or integer file descriptor which is open on the file.
753 The return value is unspecified.
755 If @var{object} is a symbolic link, either the
756 ownership of the link or the ownership of the referenced file will be
757 changed depending on the operating system (lchown is
758 unsupported at present). If @var{owner} or @var{group} is specified
759 as @code{-1}, then that ID is not changed.
763 @deffn {Scheme Procedure} chmod object mode
764 @deffnx {C Function} scm_chmod (object, mode)
765 Changes the permissions of the file referred to by @var{object}.
766 @var{object} can be a string containing a file name or a port or integer file
767 descriptor which is open on a file (in which case @code{fchmod} is used
768 as the underlying system call).
770 the new permissions as a decimal number, e.g., @code{(chmod "foo" #o755)}.
771 The return value is unspecified.
774 @deffn {Scheme Procedure} utime pathname [actime [modtime [actimens [modtimens [flags]]]]]
775 @deffnx {C Function} scm_utime (pathname, actime, modtime, actimens, modtimens, flags)
776 @code{utime} sets the access and modification times for the
777 file named by @var{pathname}. If @var{actime} or @var{modtime} is
778 not supplied, then the current time is used. @var{actime} and
779 @var{modtime} must be integer time values as returned by the
780 @code{current-time} procedure.
782 The optional @var{actimens} and @var{modtimens} are nanoseconds
783 to add @var{actime} and @var{modtime}. Nanosecond precision is
784 only supported on some combinations of file systems and operating
787 (utime "foo" (- (current-time) 3600))
789 will set the access time to one hour in the past and the
790 modification time to the current time.
794 @deffn {Scheme Procedure} delete-file str
795 @deffnx {C Function} scm_delete_file (str)
796 Deletes (or ``unlinks'') the file whose path is specified by
800 @deffn {Scheme Procedure} copy-file oldfile newfile
801 @deffnx {C Function} scm_copy_file (oldfile, newfile)
802 Copy the file specified by @var{oldfile} to @var{newfile}.
803 The return value is unspecified.
806 @deffn {Scheme Procedure} sendfile out in count [offset]
807 @deffnx {C Function} scm_sendfile (out, in, count, offset)
808 Send @var{count} bytes from @var{in} to @var{out}, both of which
809 must be either open file ports or file descriptors. When
810 @var{offset} is omitted, start reading from @var{in}'s current
811 position; otherwise, start reading at @var{offset}. Return
812 the number of bytes actually sent.
814 When @var{in} is a port, it is often preferable to specify @var{offset},
815 because @var{in}'s offset as a port may be different from the offset of
816 its underlying file descriptor.
818 On systems that support it, such as GNU/Linux, this procedure uses the
819 @code{sendfile} libc function, which usually corresponds to a system
820 call. This is faster than doing a series of @code{read} and
821 @code{write} system calls. A typical application is to send a file over
824 In some cases, the @code{sendfile} libc function may return
825 @code{EINVAL} or @code{ENOSYS}. In that case, Guile's @code{sendfile}
826 procedure automatically falls back to doing a series of @code{read} and
829 In other cases, the libc function may send fewer bytes than
830 @var{count}---for instance because @var{out} is a slow or limited
831 device, such as a pipe. When that happens, Guile's @code{sendfile}
832 automatically retries until exactly @var{count} bytes were sent or an
837 @deffn {Scheme Procedure} rename-file oldname newname
838 @deffnx {C Function} scm_rename (oldname, newname)
839 Renames the file specified by @var{oldname} to @var{newname}.
840 The return value is unspecified.
843 @deffn {Scheme Procedure} link oldpath newpath
844 @deffnx {C Function} scm_link (oldpath, newpath)
845 Creates a new name @var{newpath} in the file system for the
846 file named by @var{oldpath}. If @var{oldpath} is a symbolic
847 link, the link may or may not be followed depending on the
851 @deffn {Scheme Procedure} symlink oldpath newpath
852 @deffnx {C Function} scm_symlink (oldpath, newpath)
853 Create a symbolic link named @var{newpath} with the value (i.e., pointing to)
854 @var{oldpath}. The return value is unspecified.
857 @deffn {Scheme Procedure} mkdir path [mode]
858 @deffnx {C Function} scm_mkdir (path, mode)
859 Create a new directory named by @var{path}. If @var{mode} is omitted
860 then the permissions of the directory file are set using the current
861 umask (@pxref{Processes}). Otherwise they are set to the decimal
862 value specified with @var{mode}. The return value is unspecified.
865 @deffn {Scheme Procedure} rmdir path
866 @deffnx {C Function} scm_rmdir (path)
867 Remove the existing directory named by @var{path}. The directory must
868 be empty for this to succeed. The return value is unspecified.
871 @deffn {Scheme Procedure} opendir dirname
872 @deffnx {C Function} scm_opendir (dirname)
873 @cindex directory contents
874 Open the directory specified by @var{dirname} and return a directory
877 Before using this and the procedures below, make sure to see the
878 higher-level procedures for directory traversal that are available
879 (@pxref{File Tree Walk}).
882 @deffn {Scheme Procedure} directory-stream? object
883 @deffnx {C Function} scm_directory_stream_p (object)
884 Return a boolean indicating whether @var{object} is a directory
885 stream as returned by @code{opendir}.
888 @deffn {Scheme Procedure} readdir stream
889 @deffnx {C Function} scm_readdir (stream)
890 Return (as a string) the next directory entry from the directory stream
891 @var{stream}. If there is no remaining entry to be read then the
892 end of file object is returned.
895 @deffn {Scheme Procedure} rewinddir stream
896 @deffnx {C Function} scm_rewinddir (stream)
897 Reset the directory port @var{stream} so that the next call to
898 @code{readdir} will return the first directory entry.
901 @deffn {Scheme Procedure} closedir stream
902 @deffnx {C Function} scm_closedir (stream)
903 Close the directory stream @var{stream}.
904 The return value is unspecified.
907 Here is an example showing how to display all the entries in a
911 (define dir (opendir "/usr/lib"))
912 (do ((entry (readdir dir) (readdir dir)))
913 ((eof-object? entry))
914 (display entry)(newline))
918 @deffn {Scheme Procedure} sync
919 @deffnx {C Function} scm_sync ()
920 Flush the operating system disk buffers.
921 The return value is unspecified.
924 @deffn {Scheme Procedure} mknod path type perms dev
925 @deffnx {C Function} scm_mknod (path, type, perms, dev)
927 Creates a new special file, such as a file corresponding to a device.
928 @var{path} specifies the name of the file. @var{type} should be one
929 of the following symbols: @samp{regular}, @samp{directory},
930 @samp{symlink}, @samp{block-special}, @samp{char-special},
931 @samp{fifo}, or @samp{socket}. @var{perms} (an integer) specifies the
932 file permissions. @var{dev} (an integer) specifies which device the
933 special file refers to. Its exact interpretation depends on the kind
934 of special file being created.
938 (mknod "/dev/fd0" 'block-special #o660 (+ (* 2 256) 2))
941 The return value is unspecified.
944 @deffn {Scheme Procedure} tmpnam
945 @deffnx {C Function} scm_tmpnam ()
946 @cindex temporary file
947 Return an auto-generated name of a temporary file, a file which
948 doesn't already exist. The name includes a path, it's usually in
949 @file{/tmp} but that's system dependent.
951 Care must be taken when using @code{tmpnam}. In between choosing the
952 name and creating the file another program might use that name, or an
953 attacker might even make it a symlink pointing at something important
954 and causing you to overwrite that.
956 The safe way is to create the file using @code{open} with
957 @code{O_EXCL} to avoid any overwriting. A loop can try again with
958 another name if the file exists (error @code{EEXIST}).
959 @code{mkstemp!} below does that.
962 @deffn {Scheme Procedure} mkstemp! tmpl
963 @deffnx {C Function} scm_mkstemp (tmpl)
964 @cindex temporary file
965 Create a new unique file in the file system and return a new buffered
966 port open for reading and writing to the file.
968 @var{tmpl} is a string specifying where the file should be created: it
969 must end with @samp{XXXXXX} and those @samp{X}s will be changed in the
970 string to return the name of the file. (@code{port-filename} on the
971 port also gives the name.)
973 POSIX doesn't specify the permissions mode of the file, on GNU and
974 most systems it's @code{#o600}. An application can use @code{chmod}
975 to relax that if desired. For example @code{#o666} less @code{umask},
976 which is usual for ordinary file creation,
979 (let ((port (mkstemp! (string-copy "/tmp/myfile-XXXXXX"))))
980 (chmod port (logand #o666 (lognot (umask))))
985 @deffn {Scheme Procedure} tmpfile
986 @deffnx {C Function} scm_tmpfile ()
987 Return an input/output port to a unique temporary file
988 named using the path prefix @code{P_tmpdir} defined in
990 The file is automatically deleted when the port is closed
991 or the program terminates.
994 @deffn {Scheme Procedure} dirname filename
995 @deffnx {C Function} scm_dirname (filename)
996 Return the directory name component of the file name
997 @var{filename}. If @var{filename} does not contain a directory
998 component, @code{.} is returned.
1001 @deffn {Scheme Procedure} basename filename [suffix]
1002 @deffnx {C Function} scm_basename (filename, suffix)
1003 Return the base name of the file name @var{filename}. The
1004 base name is the file name without any directory components.
1005 If @var{suffix} is provided, and is equal to the end of
1006 @var{basename}, it is removed also.
1009 (basename "/tmp/test.xml" ".xml")
1014 @deffn {Scheme Procedure} file-exists? filename
1015 Return @code{#t} if the file named @var{filename} exists, @code{#f} if
1019 @cindex file name separator
1020 @cindex absolute file name
1022 Many operating systems, such as GNU, use @code{/} (forward slash) to
1023 separate the components of a file name; any file name starting with
1024 @code{/} is considered an @dfn{absolute file name}. These conventions
1025 are specified by the POSIX Base Definitions, which refer to conforming
1026 file names as ``pathnames''. Some operating systems use a different
1027 convention; in particular, Windows uses @code{\} (backslash) as the file
1028 name separator, and also has the notion of @dfn{volume names} like
1029 @code{C:\} for absolute file names. The following procedures and
1030 variables provide support for portable file name manipulations.
1032 @deffn {Scheme Procedure} system-file-name-convention
1033 Return either @code{posix} or @code{windows}, depending on
1034 what kind of system this Guile is running on.
1037 @deffn {Scheme Procedure} file-name-separator? c
1038 Return true if character @var{c} is a file name separator on the host
1042 @deffn {Scheme Procedure} absolute-file-name? file-name
1043 Return true if @var{file-name} denotes an absolute file name on the host
1047 @defvr {Scheme Variable} file-name-separator-string
1048 The preferred file name separator.
1050 Note that on MinGW builds for Windows, both @code{/} and @code{\} are
1051 valid separators. Thus, programs should not assume that
1052 @code{file-name-separator-string} is the @emph{only} file name
1053 separator---e.g., when extracting the components of a file name.
1057 @node User Information
1058 @subsection User Information
1059 @cindex user information
1060 @cindex password file
1063 The facilities in this section provide an interface to the user and
1065 They should be used with care since they are not reentrant.
1067 The following functions accept an object representing user information
1068 and return a selected component:
1070 @deffn {Scheme Procedure} passwd:name pw
1071 The name of the userid.
1073 @deffn {Scheme Procedure} passwd:passwd pw
1074 The encrypted passwd.
1076 @deffn {Scheme Procedure} passwd:uid pw
1079 @deffn {Scheme Procedure} passwd:gid pw
1080 The group id number.
1082 @deffn {Scheme Procedure} passwd:gecos pw
1085 @deffn {Scheme Procedure} passwd:dir pw
1088 @deffn {Scheme Procedure} passwd:shell pw
1093 @deffn {Scheme Procedure} getpwuid uid
1094 Look up an integer userid in the user database.
1097 @deffn {Scheme Procedure} getpwnam name
1098 Look up a user name string in the user database.
1101 @deffn {Scheme Procedure} setpwent
1102 Initializes a stream used by @code{getpwent} to read from the user database.
1103 The next use of @code{getpwent} will return the first entry. The
1104 return value is unspecified.
1107 @deffn {Scheme Procedure} getpwent
1108 Read the next entry in the user database stream. The return is a
1109 passwd user object as above, or @code{#f} when no more entries.
1112 @deffn {Scheme Procedure} endpwent
1113 Closes the stream used by @code{getpwent}. The return value is unspecified.
1116 @deffn {Scheme Procedure} setpw [arg]
1117 @deffnx {C Function} scm_setpwent (arg)
1118 If called with a true argument, initialize or reset the password data
1119 stream. Otherwise, close the stream. The @code{setpwent} and
1120 @code{endpwent} procedures are implemented on top of this.
1123 @deffn {Scheme Procedure} getpw [user]
1124 @deffnx {C Function} scm_getpwuid (user)
1125 Look up an entry in the user database. @var{user} can be an integer,
1126 a string, or omitted, giving the behaviour of getpwuid, getpwnam
1127 or getpwent respectively.
1130 The following functions accept an object representing group information
1131 and return a selected component:
1133 @deffn {Scheme Procedure} group:name gr
1136 @deffn {Scheme Procedure} group:passwd gr
1137 The encrypted group password.
1139 @deffn {Scheme Procedure} group:gid gr
1140 The group id number.
1142 @deffn {Scheme Procedure} group:mem gr
1143 A list of userids which have this group as a supplementary group.
1147 @deffn {Scheme Procedure} getgrgid gid
1148 Look up an integer group id in the group database.
1151 @deffn {Scheme Procedure} getgrnam name
1152 Look up a group name in the group database.
1155 @deffn {Scheme Procedure} setgrent
1156 Initializes a stream used by @code{getgrent} to read from the group database.
1157 The next use of @code{getgrent} will return the first entry.
1158 The return value is unspecified.
1161 @deffn {Scheme Procedure} getgrent
1162 Return the next entry in the group database, using the stream set by
1166 @deffn {Scheme Procedure} endgrent
1167 Closes the stream used by @code{getgrent}.
1168 The return value is unspecified.
1171 @deffn {Scheme Procedure} setgr [arg]
1172 @deffnx {C Function} scm_setgrent (arg)
1173 If called with a true argument, initialize or reset the group data
1174 stream. Otherwise, close the stream. The @code{setgrent} and
1175 @code{endgrent} procedures are implemented on top of this.
1178 @deffn {Scheme Procedure} getgr [group]
1179 @deffnx {C Function} scm_getgrgid (group)
1180 Look up an entry in the group database. @var{group} can be an integer,
1181 a string, or omitted, giving the behaviour of getgrgid, getgrnam
1182 or getgrent respectively.
1185 In addition to the accessor procedures for the user database, the
1186 following shortcut procedure is also available.
1188 @deffn {Scheme Procedure} getlogin
1189 @deffnx {C Function} scm_getlogin ()
1190 Return a string containing the name of the user logged in on
1191 the controlling terminal of the process, or @code{#f} if this
1192 information cannot be obtained.
1200 @deffn {Scheme Procedure} current-time
1201 @deffnx {C Function} scm_current_time ()
1202 Return the number of seconds since 1970-01-01 00:00:00 @acronym{UTC},
1203 excluding leap seconds.
1206 @deffn {Scheme Procedure} gettimeofday
1207 @deffnx {C Function} scm_gettimeofday ()
1208 Return a pair containing the number of seconds and microseconds
1209 since 1970-01-01 00:00:00 @acronym{UTC}, excluding leap seconds. Note:
1210 whether true microsecond resolution is available depends on the
1214 The following procedures either accept an object representing a broken down
1215 time and return a selected component, or accept an object representing
1216 a broken down time and a value and set the component to the value.
1217 The numbers in parentheses give the usual range.
1219 @deffn {Scheme Procedure} tm:sec tm
1220 @deffnx {Scheme Procedure} set-tm:sec tm val
1223 @deffn {Scheme Procedure} tm:min tm
1224 @deffnx {Scheme Procedure} set-tm:min tm val
1227 @deffn {Scheme Procedure} tm:hour tm
1228 @deffnx {Scheme Procedure} set-tm:hour tm val
1231 @deffn {Scheme Procedure} tm:mday tm
1232 @deffnx {Scheme Procedure} set-tm:mday tm val
1233 Day of the month (1-31).
1235 @deffn {Scheme Procedure} tm:mon tm
1236 @deffnx {Scheme Procedure} set-tm:mon tm val
1239 @deffn {Scheme Procedure} tm:year tm
1240 @deffnx {Scheme Procedure} set-tm:year tm val
1241 Year (70-), the year minus 1900.
1243 @deffn {Scheme Procedure} tm:wday tm
1244 @deffnx {Scheme Procedure} set-tm:wday tm val
1245 Day of the week (0-6) with Sunday represented as 0.
1247 @deffn {Scheme Procedure} tm:yday tm
1248 @deffnx {Scheme Procedure} set-tm:yday tm val
1249 Day of the year (0-364, 365 in leap years).
1251 @deffn {Scheme Procedure} tm:isdst tm
1252 @deffnx {Scheme Procedure} set-tm:isdst tm val
1253 Daylight saving indicator (0 for ``no'', greater than 0 for ``yes'', less than
1256 @deffn {Scheme Procedure} tm:gmtoff tm
1257 @deffnx {Scheme Procedure} set-tm:gmtoff tm val
1258 Time zone offset in seconds west of @acronym{UTC} (-46800 to 43200).
1259 For example on East coast USA (zone @samp{EST+5}) this would be 18000
1260 (ie.@: @m{5\times60\times60,5*60*60}) in winter, or 14400
1261 (ie.@: @m{4\times60\times60,4*60*60}) during daylight savings.
1263 Note @code{tm:gmtoff} is not the same as @code{tm_gmtoff} in the C
1264 @code{tm} structure. @code{tm_gmtoff} is seconds east and hence the
1265 negative of the value here.
1267 @deffn {Scheme Procedure} tm:zone tm
1268 @deffnx {Scheme Procedure} set-tm:zone tm val
1269 Time zone label (a string), not necessarily unique.
1273 @deffn {Scheme Procedure} localtime time [zone]
1274 @deffnx {C Function} scm_localtime (time, zone)
1276 Return an object representing the broken down components of
1277 @var{time}, an integer like the one returned by
1278 @code{current-time}. The time zone for the calculation is
1279 optionally specified by @var{zone} (a string), otherwise the
1280 @env{TZ} environment variable or the system default is used.
1283 @deffn {Scheme Procedure} gmtime time
1284 @deffnx {C Function} scm_gmtime (time)
1285 Return an object representing the broken down components of
1286 @var{time}, an integer like the one returned by
1287 @code{current-time}. The values are calculated for @acronym{UTC}.
1290 @deffn {Scheme Procedure} mktime sbd-time [zone]
1291 @deffnx {C Function} scm_mktime (sbd_time, zone)
1292 For a broken down time object @var{sbd-time}, return a pair the
1293 @code{car} of which is an integer time like @code{current-time}, and
1294 the @code{cdr} of which is a new broken down time with normalized
1297 @var{zone} is a timezone string, or the default is the @env{TZ}
1298 environment variable or the system default (@pxref{TZ Variable,,
1299 Specifying the Time Zone with @env{TZ}, libc, GNU C Library Reference
1300 Manual}). @var{sbd-time} is taken to be in that @var{zone}.
1302 The following fields of @var{sbd-time} are used: @code{tm:year},
1303 @code{tm:mon}, @code{tm:mday}, @code{tm:hour}, @code{tm:min},
1304 @code{tm:sec}, @code{tm:isdst}. The values can be outside their usual
1305 ranges. For example @code{tm:hour} normally goes up to 23, but a
1306 value say 33 would mean 9 the following day.
1308 @code{tm:isdst} in @var{sbd-time} says whether the time given is with
1309 daylight savings or not. This is ignored if @var{zone} doesn't have
1310 any daylight savings adjustment amount.
1312 The broken down time in the return normalizes the values of
1313 @var{sbd-time} by bringing them into their usual ranges, and using the
1314 actual daylight savings rule for that time in @var{zone} (which may
1315 differ from what @var{sbd-time} had). The easiest way to think of
1316 this is that @var{sbd-time} plus @var{zone} converts to the integer
1317 UTC time, then a @code{localtime} is applied to get the normal
1318 presentation of that time, in @var{zone}.
1321 @deffn {Scheme Procedure} tzset
1322 @deffnx {C Function} scm_tzset ()
1323 Initialize the timezone from the @env{TZ} environment variable
1324 or the system default. It's not usually necessary to call this procedure
1325 since it's done automatically by other procedures that depend on the
1329 @deffn {Scheme Procedure} strftime format tm
1330 @deffnx {C Function} scm_strftime (format, tm)
1331 @cindex time formatting
1332 Return a string which is broken-down time structure @var{tm} formatted
1333 according to the given @var{format} string.
1335 @var{format} contains field specifications introduced by a @samp{%}
1336 character. See @ref{Formatting Calendar Time,,, libc, The GNU C
1337 Library Reference Manual}, or @samp{man 3 strftime}, for the available
1341 (strftime "%c" (localtime (current-time)))
1342 @result{} "Mon Mar 11 20:17:43 2002"
1345 If @code{setlocale} has been called (@pxref{Locales}), month and day
1346 names are from the current locale and in the locale character set.
1349 @deffn {Scheme Procedure} strptime format string
1350 @deffnx {C Function} scm_strptime (format, string)
1351 @cindex time parsing
1352 Performs the reverse action to @code{strftime}, parsing
1353 @var{string} according to the specification supplied in
1354 @var{format}. The interpretation of month and day names is
1355 dependent on the current locale. The value returned is a pair.
1356 The @acronym{CAR} has an object with time components
1357 in the form returned by @code{localtime} or @code{gmtime},
1358 but the time zone components
1359 are not usefully set.
1360 The @acronym{CDR} reports the number of characters from @var{string}
1361 which were used for the conversion.
1364 @defvar internal-time-units-per-second
1365 The value of this variable is the number of time units per second
1366 reported by the following procedures.
1369 @deffn {Scheme Procedure} times
1370 @deffnx {C Function} scm_times ()
1371 Return an object with information about real and processor
1372 time. The following procedures accept such an object as an
1373 argument and return a selected component:
1375 @deffn {Scheme Procedure} tms:clock tms
1376 The current real time, expressed as time units relative to an
1379 @deffn {Scheme Procedure} tms:utime tms
1380 The CPU time units used by the calling process.
1382 @deffn {Scheme Procedure} tms:stime tms
1383 The CPU time units used by the system on behalf of the calling
1386 @deffn {Scheme Procedure} tms:cutime tms
1387 The CPU time units used by terminated child processes of the
1388 calling process, whose status has been collected (e.g., using
1391 @deffn {Scheme Procedure} tms:cstime tms
1392 Similarly, the CPU times units used by the system on behalf of
1393 terminated child processes.
1397 @deffn {Scheme Procedure} get-internal-real-time
1398 @deffnx {C Function} scm_get_internal_real_time ()
1399 Return the number of time units since the interpreter was
1403 @deffn {Scheme Procedure} get-internal-run-time
1404 @deffnx {C Function} scm_get_internal_run_time ()
1405 Return the number of time units of processor time used by the
1406 interpreter. Both @emph{system} and @emph{user} time are
1407 included but subprocesses are not.
1410 @node Runtime Environment
1411 @subsection Runtime Environment
1413 @deffn {Scheme Procedure} program-arguments
1414 @deffnx {Scheme Procedure} command-line
1415 @deffnx {Scheme Procedure} set-program-arguments
1416 @deffnx {C Function} scm_program_arguments ()
1417 @deffnx {C Function} scm_set_program_arguments_scm (lst)
1418 @cindex command line
1419 @cindex program arguments
1420 Get the command line arguments passed to Guile, or set new arguments.
1422 The arguments are a list of strings, the first of which is the invoked
1423 program name. This is just @nicode{"guile"} (or the executable path)
1424 when run interactively, or it's the script name when running a script
1425 with @option{-s} (@pxref{Invoking Guile}).
1428 guile -L /my/extra/dir -s foo.scm abc def
1430 (program-arguments) @result{} ("foo.scm" "abc" "def")
1433 @code{set-program-arguments} allows a library module or similar to
1434 modify the arguments, for example to strip options it recognises,
1435 leaving the rest for the mainline.
1437 The argument list is held in a fluid, which means it's separate for
1438 each thread. Neither the list nor the strings within it are copied at
1439 any point and normally should not be mutated.
1441 The two names @code{program-arguments} and @code{command-line} are an
1442 historical accident, they both do exactly the same thing. The name
1443 @code{scm_set_program_arguments_scm} has an extra @code{_scm} on the
1444 end to avoid clashing with the C function below.
1447 @deftypefn {C Function} void scm_set_program_arguments (int argc, char **argv, char *first)
1448 @cindex command line
1449 @cindex program arguments
1450 Set the list of command line arguments for @code{program-arguments}
1451 and @code{command-line} above.
1453 @var{argv} is an array of null-terminated strings, as in a C
1454 @code{main} function. @var{argc} is the number of strings in
1455 @var{argv}, or if it's negative then a @code{NULL} in @var{argv} marks
1458 @var{first} is an extra string put at the start of the arguments, or
1459 @code{NULL} for no such extra. This is a convenient way to pass the
1460 program name after advancing @var{argv} to strip option arguments.
1465 char *progname = argv[0];
1466 for (argv++; argv[0] != NULL && argv[0][0] == '-'; argv++)
1468 /* munch option ... */
1470 /* remaining args for scheme level use */
1471 scm_set_program_arguments (-1, argv, progname);
1475 This sort of thing is often done at startup under
1476 @code{scm_boot_guile} with options handled at the C level removed.
1477 The given strings are all copied, so the C data is not accessed again
1478 once @code{scm_set_program_arguments} returns.
1481 @deffn {Scheme Procedure} getenv name
1482 @deffnx {C Function} scm_getenv (name)
1484 Looks up the string @var{name} in the current environment. The return
1485 value is @code{#f} unless a string of the form @code{NAME=VALUE} is
1486 found, in which case the string @code{VALUE} is returned.
1489 @deffn {Scheme Procedure} setenv name value
1490 Modifies the environment of the current process, which is
1491 also the default environment inherited by child processes.
1493 If @var{value} is @code{#f}, then @var{name} is removed from the
1494 environment. Otherwise, the string @var{name}=@var{value} is added
1495 to the environment, replacing any existing string with name matching
1498 The return value is unspecified.
1501 @deffn {Scheme Procedure} unsetenv name
1502 Remove variable @var{name} from the environment. The
1503 name can not contain a @samp{=} character.
1506 @deffn {Scheme Procedure} environ [env]
1507 @deffnx {C Function} scm_environ (env)
1508 If @var{env} is omitted, return the current environment (in the
1509 Unix sense) as a list of strings. Otherwise set the current
1510 environment, which is also the default environment for child
1511 processes, to the supplied list of strings. Each member of
1512 @var{env} should be of the form @var{name}=@var{value} and values of
1513 @var{name} should not be duplicated. If @var{env} is supplied
1514 then the return value is unspecified.
1517 @deffn {Scheme Procedure} putenv str
1518 @deffnx {C Function} scm_putenv (str)
1519 Modifies the environment of the current process, which is
1520 also the default environment inherited by child processes.
1522 If @var{str} is of the form @code{NAME=VALUE} then it will be written
1523 directly into the environment, replacing any existing environment string
1525 name matching @code{NAME}. If @var{str} does not contain an equal
1526 sign, then any existing string with name matching @var{str} will
1529 The return value is unspecified.
1534 @subsection Processes
1536 @cindex child processes
1539 @deffn {Scheme Procedure} chdir str
1540 @deffnx {C Function} scm_chdir (str)
1541 @cindex current directory
1542 Change the current working directory to @var{str}.
1543 The return value is unspecified.
1547 @deffn {Scheme Procedure} getcwd
1548 @deffnx {C Function} scm_getcwd ()
1549 Return the name of the current working directory.
1552 @deffn {Scheme Procedure} umask [mode]
1553 @deffnx {C Function} scm_umask (mode)
1554 If @var{mode} is omitted, returns a decimal number representing the
1555 current file creation mask. Otherwise the file creation mask is set
1556 to @var{mode} and the previous value is returned. @xref{Setting
1557 Permissions,,Assigning File Permissions,libc,The GNU C Library
1558 Reference Manual}, for more on how to use umasks.
1560 E.g., @code{(umask #o022)} sets the mask to octal 22/decimal 18.
1563 @deffn {Scheme Procedure} chroot path
1564 @deffnx {C Function} scm_chroot (path)
1565 Change the root directory to that specified in @var{path}.
1566 This directory will be used for path names beginning with
1567 @file{/}. The root directory is inherited by all children
1568 of the current process. Only the superuser may change the
1572 @deffn {Scheme Procedure} getpid
1573 @deffnx {C Function} scm_getpid ()
1574 Return an integer representing the current process ID.
1577 @deffn {Scheme Procedure} getgroups
1578 @deffnx {C Function} scm_getgroups ()
1579 Return a vector of integers representing the current
1580 supplementary group IDs.
1583 @deffn {Scheme Procedure} getppid
1584 @deffnx {C Function} scm_getppid ()
1585 Return an integer representing the process ID of the parent
1589 @deffn {Scheme Procedure} getuid
1590 @deffnx {C Function} scm_getuid ()
1591 Return an integer representing the current real user ID.
1594 @deffn {Scheme Procedure} getgid
1595 @deffnx {C Function} scm_getgid ()
1596 Return an integer representing the current real group ID.
1599 @deffn {Scheme Procedure} geteuid
1600 @deffnx {C Function} scm_geteuid ()
1601 Return an integer representing the current effective user ID.
1602 If the system does not support effective IDs, then the real ID
1603 is returned. @code{(provided? 'EIDs)} reports whether the
1604 system supports effective IDs.
1607 @deffn {Scheme Procedure} getegid
1608 @deffnx {C Function} scm_getegid ()
1609 Return an integer representing the current effective group ID.
1610 If the system does not support effective IDs, then the real ID
1611 is returned. @code{(provided? 'EIDs)} reports whether the
1612 system supports effective IDs.
1615 @deffn {Scheme Procedure} setgroups vec
1616 @deffnx {C Function} scm_setgroups (vec)
1617 Set the current set of supplementary group IDs to the integers in the
1618 given vector @var{vec}. The return value is unspecified.
1620 Generally only the superuser can set the process group IDs
1621 (@pxref{Setting Groups, Setting the Group IDs,, libc, The GNU C
1622 Library Reference Manual}).
1625 @deffn {Scheme Procedure} setuid id
1626 @deffnx {C Function} scm_setuid (id)
1627 Sets both the real and effective user IDs to the integer @var{id}, provided
1628 the process has appropriate privileges.
1629 The return value is unspecified.
1632 @deffn {Scheme Procedure} setgid id
1633 @deffnx {C Function} scm_setgid (id)
1634 Sets both the real and effective group IDs to the integer @var{id}, provided
1635 the process has appropriate privileges.
1636 The return value is unspecified.
1639 @deffn {Scheme Procedure} seteuid id
1640 @deffnx {C Function} scm_seteuid (id)
1641 Sets the effective user ID to the integer @var{id}, provided the process
1642 has appropriate privileges. If effective IDs are not supported, the
1643 real ID is set instead---@code{(provided? 'EIDs)} reports whether the
1644 system supports effective IDs.
1645 The return value is unspecified.
1648 @deffn {Scheme Procedure} setegid id
1649 @deffnx {C Function} scm_setegid (id)
1650 Sets the effective group ID to the integer @var{id}, provided the process
1651 has appropriate privileges. If effective IDs are not supported, the
1652 real ID is set instead---@code{(provided? 'EIDs)} reports whether the
1653 system supports effective IDs.
1654 The return value is unspecified.
1657 @deffn {Scheme Procedure} getpgrp
1658 @deffnx {C Function} scm_getpgrp ()
1659 Return an integer representing the current process group ID.
1660 This is the @acronym{POSIX} definition, not @acronym{BSD}.
1663 @deffn {Scheme Procedure} setpgid pid pgid
1664 @deffnx {C Function} scm_setpgid (pid, pgid)
1665 Move the process @var{pid} into the process group @var{pgid}. @var{pid} or
1666 @var{pgid} must be integers: they can be zero to indicate the ID of the
1668 Fails on systems that do not support job control.
1669 The return value is unspecified.
1672 @deffn {Scheme Procedure} setsid
1673 @deffnx {C Function} scm_setsid ()
1674 Creates a new session. The current process becomes the session leader
1675 and is put in a new process group. The process will be detached
1676 from its controlling terminal if it has one.
1677 The return value is an integer representing the new process group ID.
1680 @deffn {Scheme Procedure} getsid pid
1681 @deffnx {C Function} scm_getsid (pid)
1682 Returns the session ID of process @var{pid}. (The session
1683 ID of a process is the process group ID of its session leader.)
1686 @deffn {Scheme Procedure} waitpid pid [options]
1687 @deffnx {C Function} scm_waitpid (pid, options)
1688 This procedure collects status information from a child process which
1689 has terminated or (optionally) stopped. Normally it will
1690 suspend the calling process until this can be done. If more than one
1691 child process is eligible then one will be chosen by the operating system.
1693 The value of @var{pid} determines the behaviour:
1696 @item @var{pid} greater than 0
1697 Request status information from the specified child process.
1698 @item @var{pid} equal to -1 or @code{WAIT_ANY}
1700 Request status information for any child process.
1701 @item @var{pid} equal to 0 or @code{WAIT_MYPGRP}
1703 Request status information for any child process in the current process
1705 @item @var{pid} less than -1
1706 Request status information for any child process whose process group ID
1707 is @minus{}@var{pid}.
1710 The @var{options} argument, if supplied, should be the bitwise OR of the
1711 values of zero or more of the following variables:
1714 Return immediately even if there are no child processes to be collected.
1718 Report status information for stopped processes as well as terminated
1722 The return value is a pair containing:
1726 The process ID of the child process, or 0 if @code{WNOHANG} was
1727 specified and no process was collected.
1729 The integer status value.
1734 functions can be used to decode the process status code returned
1737 @deffn {Scheme Procedure} status:exit-val status
1738 @deffnx {C Function} scm_status_exit_val (status)
1739 Return the exit status value, as would be set if a process
1740 ended normally through a call to @code{exit} or @code{_exit},
1741 if any, otherwise @code{#f}.
1744 @deffn {Scheme Procedure} status:term-sig status
1745 @deffnx {C Function} scm_status_term_sig (status)
1746 Return the signal number which terminated the process, if any,
1747 otherwise @code{#f}.
1750 @deffn {Scheme Procedure} status:stop-sig status
1751 @deffnx {C Function} scm_status_stop_sig (status)
1752 Return the signal number which stopped the process, if any,
1753 otherwise @code{#f}.
1756 @deffn {Scheme Procedure} system [cmd]
1757 @deffnx {C Function} scm_system (cmd)
1758 Execute @var{cmd} using the operating system's ``command
1759 processor''. Under Unix this is usually the default shell
1760 @code{sh}. The value returned is @var{cmd}'s exit status as
1761 returned by @code{waitpid}, which can be interpreted using the
1764 If @code{system} is called without arguments, return a boolean
1765 indicating whether the command processor is available.
1768 @deffn {Scheme Procedure} system* arg1 arg2 @dots{}
1769 @deffnx {C Function} scm_system_star (args)
1770 Execute the command indicated by @var{arg1} @var{arg2} @enddots{}. The
1771 first element must be a string indicating the command to be executed,
1772 and the remaining items must be strings representing each of the
1773 arguments to that command.
1775 This function returns the exit status of the command as provided by
1776 @code{waitpid}. This value can be handled with @code{status:exit-val}
1777 and the related functions.
1779 @code{system*} is similar to @code{system}, but accepts only one
1780 string per-argument, and performs no shell interpretation. The
1781 command is executed using fork and execlp. Accordingly this function
1782 may be safer than @code{system} in situations where shell
1783 interpretation is not required.
1785 Example: (system* "echo" "foo" "bar")
1788 @deffn {Scheme Procedure} quit [status]
1789 @deffnx {Scheme Procedure} exit [status]
1790 Terminate the current process with proper unwinding of the Scheme stack.
1791 The exit status zero if @var{status} is not supplied. If @var{status}
1792 is supplied, and it is an integer, that integer is used as the exit
1793 status. If @var{status} is @code{#t} or @code{#f}, the exit status is 0
1796 The procedure @code{exit} is an alias of @code{quit}. They have the
1800 @deffn {Scheme Procedure} primitive-exit [status]
1801 @deffnx {Scheme Procedure} primitive-_exit [status]
1802 @deffnx {C Function} scm_primitive_exit (status)
1803 @deffnx {C Function} scm_primitive__exit (status)
1804 Terminate the current process without unwinding the Scheme stack. The
1805 exit status is @var{status} if supplied, otherwise zero.
1807 @code{primitive-exit} uses the C @code{exit} function and hence runs
1808 usual C level cleanups (flush output streams, call @code{atexit}
1809 functions, etc, see @ref{Normal Termination,,, libc, The GNU C Library
1810 Reference Manual})).
1812 @code{primitive-_exit} is the @code{_exit} system call
1813 (@pxref{Termination Internals,,, libc, The GNU C Library Reference
1814 Manual}). This terminates the program immediately, with neither
1815 Scheme-level nor C-level cleanups.
1817 The typical use for @code{primitive-_exit} is from a child process
1818 created with @code{primitive-fork}. For example in a Gdk program the
1819 child process inherits the X server connection and a C-level
1820 @code{atexit} cleanup which will close that connection. But closing
1821 in the child would upset the protocol in the parent, so
1822 @code{primitive-_exit} should be used to exit without that.
1825 @deffn {Scheme Procedure} execl filename arg @dots{}
1826 @deffnx {C Function} scm_execl (filename, args)
1827 Executes the file named by @var{filename} as a new process image.
1828 The remaining arguments are supplied to the process; from a C program
1829 they are accessible as the @code{argv} argument to @code{main}.
1830 Conventionally the first @var{arg} is the same as @var{filename}.
1831 All arguments must be strings.
1833 If @var{arg} is missing, @var{filename} is executed with a null
1834 argument list, which may have system-dependent side-effects.
1836 This procedure is currently implemented using the @code{execv} system
1837 call, but we call it @code{execl} because of its Scheme calling interface.
1840 @deffn {Scheme Procedure} execlp filename arg @dots{}
1841 @deffnx {C Function} scm_execlp (filename, args)
1842 Similar to @code{execl}, however if
1843 @var{filename} does not contain a slash
1844 then the file to execute will be located by searching the
1845 directories listed in the @code{PATH} environment variable.
1847 This procedure is currently implemented using the @code{execvp} system
1848 call, but we call it @code{execlp} because of its Scheme calling interface.
1851 @deffn {Scheme Procedure} execle filename env arg @dots{}
1852 @deffnx {C Function} scm_execle (filename, env, args)
1853 Similar to @code{execl}, but the environment of the new process is
1854 specified by @var{env}, which must be a list of strings as returned by the
1855 @code{environ} procedure.
1857 This procedure is currently implemented using the @code{execve} system
1858 call, but we call it @code{execle} because of its Scheme calling interface.
1861 @deffn {Scheme Procedure} primitive-fork
1862 @deffnx {C Function} scm_fork ()
1863 Creates a new ``child'' process by duplicating the current ``parent'' process.
1864 In the child the return value is 0. In the parent the return value is
1865 the integer process ID of the child.
1867 Note that it is unsafe to fork a process that has multiple threads
1868 running, as only the thread that calls @code{primitive-fork} will
1869 persist in the child. Any resources that other threads held, such as
1870 locked mutexes or open file descriptors, are lost. Indeed, @acronym{POSIX}
1871 specifies that only async-signal-safe procedures are safe to call after
1872 a multithreaded fork, which is a very limited set. Guile issues a
1873 warning if it detects a fork from a multi-threaded program.
1875 If you are going to @code{exec} soon after forking, the procedures in
1876 @code{(ice-9 popen)} may be useful to you, as they fork and exec within
1877 an async-signal-safe function carefully written to ensure robust program
1878 behavior, even in the presence of threads. @xref{Pipes}, for more.
1880 This procedure has been renamed from @code{fork} to avoid a naming conflict
1884 @deffn {Scheme Procedure} nice incr
1885 @deffnx {C Function} scm_nice (incr)
1886 @cindex process priority
1887 Increment the priority of the current process by @var{incr}. A higher
1888 priority value means that the process runs less often.
1889 The return value is unspecified.
1892 @deffn {Scheme Procedure} setpriority which who prio
1893 @deffnx {C Function} scm_setpriority (which, who, prio)
1894 @vindex PRIO_PROCESS
1897 Set the scheduling priority of the process, process group
1898 or user, as indicated by @var{which} and @var{who}. @var{which}
1899 is one of the variables @code{PRIO_PROCESS}, @code{PRIO_PGRP}
1900 or @code{PRIO_USER}, and @var{who} is interpreted relative to
1901 @var{which} (a process identifier for @code{PRIO_PROCESS},
1902 process group identifier for @code{PRIO_PGRP}, and a user
1903 identifier for @code{PRIO_USER}. A zero value of @var{who}
1904 denotes the current process, process group, or user.
1905 @var{prio} is a value in the range [@minus{}20,20]. The default
1906 priority is 0; lower priorities (in numerical terms) cause more
1907 favorable scheduling. Sets the priority of all of the specified
1908 processes. Only the super-user may lower priorities. The return
1909 value is not specified.
1912 @deffn {Scheme Procedure} getpriority which who
1913 @deffnx {C Function} scm_getpriority (which, who)
1914 @vindex PRIO_PROCESS
1917 Return the scheduling priority of the process, process group
1918 or user, as indicated by @var{which} and @var{who}. @var{which}
1919 is one of the variables @code{PRIO_PROCESS}, @code{PRIO_PGRP}
1920 or @code{PRIO_USER}, and @var{who} should be interpreted depending on
1921 @var{which} (a process identifier for @code{PRIO_PROCESS},
1922 process group identifier for @code{PRIO_PGRP}, and a user
1923 identifier for @code{PRIO_USER}). A zero value of @var{who}
1924 denotes the current process, process group, or user. Return
1925 the highest priority (lowest numerical value) of any of the
1926 specified processes.
1929 @cindex affinity, CPU
1931 @deffn {Scheme Procedure} getaffinity pid
1932 @deffnx {C Function} scm_getaffinity (pid)
1933 Return a bitvector representing the CPU affinity mask for
1934 process @var{pid}. Each CPU the process has affinity with
1935 has its corresponding bit set in the returned bitvector.
1936 The number of bits set is a good estimate of how many CPUs
1937 Guile can use without stepping on other processes' toes.
1939 Currently this procedure is only defined on GNU variants
1940 (@pxref{CPU Affinity, @code{sched_getaffinity},, libc, The
1941 GNU C Library Reference Manual}).
1944 @deffn {Scheme Procedure} setaffinity pid mask
1945 @deffnx {C Function} scm_setaffinity (pid, mask)
1946 Install the CPU affinity mask @var{mask}, a bitvector, for
1947 the process or thread with ID @var{pid}. The return value
1950 Currently this procedure is only defined on GNU variants
1951 (@pxref{CPU Affinity, @code{sched_setaffinity},, libc, The
1952 GNU C Library Reference Manual}).
1955 @deffn {Scheme Procedure} total-processor-count
1956 @deffnx {C Function} scm_total_processor_count ()
1957 Return the total number of processors of the machine, which
1958 is guaranteed to be at least 1. A ``processor'' here is a
1959 thread execution unit, which can be either:
1962 @item an execution core in a (possibly multi-core) chip, in a
1963 (possibly multi- chip) module, in a single computer, or
1964 @item a thread execution unit inside a core in the case of
1965 @dfn{hyper-threaded} CPUs.
1968 Which of the two definitions is used, is unspecified.
1971 @deffn {Scheme Procedure} current-processor-count
1972 @deffnx {C Function} scm_current_processor_count ()
1973 Like @code{total-processor-count}, but return the number of
1974 processors available to the current process. See
1975 @code{setaffinity} and @code{getaffinity} for more
1984 The following procedures raise, handle and wait for signals.
1986 Scheme code signal handlers are run via a system async (@pxref{System
1987 asyncs}), so they're called in the handler's thread at the next safe
1988 opportunity. Generally this is after any currently executing
1989 primitive procedure finishes (which could be a long time for
1990 primitives that wait for an external event).
1992 @deffn {Scheme Procedure} kill pid sig
1993 @deffnx {C Function} scm_kill (pid, sig)
1994 Sends a signal to the specified process or group of processes.
1996 @var{pid} specifies the processes to which the signal is sent:
1999 @item @var{pid} greater than 0
2000 The process whose identifier is @var{pid}.
2001 @item @var{pid} equal to 0
2002 All processes in the current process group.
2003 @item @var{pid} less than -1
2004 The process group whose identifier is -@var{pid}
2005 @item @var{pid} equal to -1
2006 If the process is privileged, all processes except for some special
2007 system processes. Otherwise, all processes with the current effective
2011 @var{sig} should be specified using a variable corresponding to
2012 the Unix symbolic name, e.g.,
2022 A full list of signals on the GNU system may be found in @ref{Standard
2023 Signals,,,libc,The GNU C Library Reference Manual}.
2026 @deffn {Scheme Procedure} raise sig
2027 @deffnx {C Function} scm_raise (sig)
2028 Sends a specified signal @var{sig} to the current process, where
2029 @var{sig} is as described for the @code{kill} procedure.
2032 @deffn {Scheme Procedure} sigaction signum [handler [flags [thread]]]
2033 @deffnx {C Function} scm_sigaction (signum, handler, flags)
2034 @deffnx {C Function} scm_sigaction_for_thread (signum, handler, flags, thread)
2035 Install or report the signal handler for a specified signal.
2037 @var{signum} is the signal number, which can be specified using the value
2038 of variables such as @code{SIGINT}.
2040 If @var{handler} is omitted, @code{sigaction} returns a pair: the
2041 @acronym{CAR} is the current signal hander, which will be either an
2042 integer with the value @code{SIG_DFL} (default action) or
2043 @code{SIG_IGN} (ignore), or the Scheme procedure which handles the
2044 signal, or @code{#f} if a non-Scheme procedure handles the signal.
2045 The @acronym{CDR} contains the current @code{sigaction} flags for the
2048 If @var{handler} is provided, it is installed as the new handler for
2049 @var{signum}. @var{handler} can be a Scheme procedure taking one
2050 argument, or the value of @code{SIG_DFL} (default action) or
2051 @code{SIG_IGN} (ignore), or @code{#f} to restore whatever signal handler
2052 was installed before @code{sigaction} was first used. When a scheme
2053 procedure has been specified, that procedure will run in the given
2054 @var{thread}. When no thread has been given, the thread that made this
2055 call to @code{sigaction} is used.
2057 @var{flags} is a @code{logior} (@pxref{Bitwise Operations}) of the
2058 following (where provided by the system), or @code{0} for none.
2060 @defvar SA_NOCLDSTOP
2061 By default, @code{SIGCHLD} is signalled when a child process stops
2062 (ie.@: receives @code{SIGSTOP}), and when a child process terminates.
2063 With the @code{SA_NOCLDSTOP} flag, @code{SIGCHLD} is only signalled
2064 for termination, not stopping.
2066 @code{SA_NOCLDSTOP} has no effect on signals other than
2071 If a signal occurs while in a system call, deliver the signal then
2072 restart the system call (as opposed to returning an @code{EINTR} error
2076 The return value is a pair with information about the old handler as
2079 This interface does not provide access to the ``signal blocking''
2080 facility. Maybe this is not needed, since the thread support may
2081 provide solutions to the problem of consistent access to data
2085 @deffn {Scheme Procedure} restore-signals
2086 @deffnx {C Function} scm_restore_signals ()
2087 Return all signal handlers to the values they had before any call to
2088 @code{sigaction} was made. The return value is unspecified.
2091 @deffn {Scheme Procedure} alarm i
2092 @deffnx {C Function} scm_alarm (i)
2093 Set a timer to raise a @code{SIGALRM} signal after the specified
2094 number of seconds (an integer). It's advisable to install a signal
2096 @code{SIGALRM} beforehand, since the default action is to terminate
2099 The return value indicates the time remaining for the previous alarm,
2100 if any. The new value replaces the previous alarm. If there was
2101 no previous alarm, the return value is zero.
2104 @deffn {Scheme Procedure} pause
2105 @deffnx {C Function} scm_pause ()
2106 Pause the current process (thread?) until a signal arrives whose
2107 action is to either terminate the current process or invoke a
2108 handler procedure. The return value is unspecified.
2111 @deffn {Scheme Procedure} sleep secs
2112 @deffnx {Scheme Procedure} usleep usecs
2113 @deffnx {C Function} scm_sleep (secs)
2114 @deffnx {C Function} scm_usleep (usecs)
2115 Wait the given period @var{secs} seconds or @var{usecs} microseconds
2116 (both integers). If a signal arrives the wait stops and the return
2117 value is the time remaining, in seconds or microseconds respectively.
2118 If the period elapses with no signal the return is zero.
2120 On most systems the process scheduler is not microsecond accurate and
2121 the actual period slept by @code{usleep} might be rounded to a system
2122 clock tick boundary, which might be 10 milliseconds for instance.
2124 See @code{scm_std_sleep} and @code{scm_std_usleep} for equivalents at
2125 the C level (@pxref{Blocking}).
2128 @deffn {Scheme Procedure} getitimer which_timer
2129 @deffnx {Scheme Procedure} setitimer which_timer interval_seconds interval_microseconds periodic_seconds periodic_microseconds
2130 @deffnx {C Function} scm_getitimer (which_timer)
2131 @deffnx {C Function} scm_setitimer (which_timer, interval_seconds, interval_microseconds, periodic_seconds, periodic_microseconds)
2132 Get or set the periods programmed in certain system timers. These
2133 timers have a current interval value which counts down and on reaching
2134 zero raises a signal. An optional periodic value can be set to
2135 restart from there each time, for periodic operation.
2136 @var{which_timer} is one of the following values
2139 A real-time timer, counting down elapsed real time. At zero it raises
2140 @code{SIGALRM}. This is like @code{alarm} above, but with a higher
2144 @defvar ITIMER_VIRTUAL
2145 A virtual-time timer, counting down while the current process is
2146 actually using CPU. At zero it raises @code{SIGVTALRM}.
2150 A profiling timer, counting down while the process is running (like
2151 @code{ITIMER_VIRTUAL}) and also while system calls are running on the
2152 process's behalf. At zero it raises a @code{SIGPROF}.
2154 This timer is intended for profiling where a program is spending its
2155 time (by looking where it is when the timer goes off).
2158 @code{getitimer} returns the current timer value and its programmed
2159 restart value, as a list containing two pairs. Each pair is a time in
2160 seconds and microseconds: @code{((@var{interval_secs}
2161 . @var{interval_usecs}) (@var{periodic_secs}
2162 . @var{periodic_usecs}))}.
2164 @code{setitimer} sets the timer values similarly, in seconds and
2165 microseconds (which must be integers). The periodic value can be zero
2166 to have the timer run down just once. The return value is the timer's
2167 previous setting, in the same form as @code{getitimer} returns.
2170 (setitimer ITIMER_REAL
2171 5 500000 ;; first SIGALRM in 5.5 seconds time
2172 2 0) ;; then repeat every 2 seconds
2175 Although the timers are programmed in microseconds, the actual
2176 accuracy might not be that high.
2180 @node Terminals and Ptys
2181 @subsection Terminals and Ptys
2183 @deffn {Scheme Procedure} isatty? port
2184 @deffnx {C Function} scm_isatty_p (port)
2186 Return @code{#t} if @var{port} is using a serial non--file
2187 device, otherwise @code{#f}.
2190 @deffn {Scheme Procedure} ttyname port
2191 @deffnx {C Function} scm_ttyname (port)
2193 Return a string with the name of the serial terminal device
2194 underlying @var{port}.
2197 @deffn {Scheme Procedure} ctermid
2198 @deffnx {C Function} scm_ctermid ()
2200 Return a string containing the file name of the controlling
2201 terminal for the current process.
2204 @deffn {Scheme Procedure} tcgetpgrp port
2205 @deffnx {C Function} scm_tcgetpgrp (port)
2206 @cindex process group
2207 Return the process group ID of the foreground process group
2208 associated with the terminal open on the file descriptor
2209 underlying @var{port}.
2211 If there is no foreground process group, the return value is a
2212 number greater than 1 that does not match the process group ID
2213 of any existing process group. This can happen if all of the
2214 processes in the job that was formerly the foreground job have
2215 terminated, and no other job has yet been moved into the
2219 @deffn {Scheme Procedure} tcsetpgrp port pgid
2220 @deffnx {C Function} scm_tcsetpgrp (port, pgid)
2221 @cindex process group
2222 Set the foreground process group ID for the terminal used by the file
2223 descriptor underlying @var{port} to the integer @var{pgid}.
2225 must be a member of the same session as @var{pgid} and must have the same
2226 controlling terminal. The return value is unspecified.
2233 The following procedures are similar to the @code{popen} and
2234 @code{pclose} system routines. The code is in a separate ``popen''
2235 module@footnote{This module is only available on systems where the
2236 @code{fork} feature is provided (@pxref{Common Feature Symbols}).}:
2239 (use-modules (ice-9 popen))
2243 @deffn {Scheme Procedure} open-pipe command mode
2244 @deffnx {Scheme Procedure} open-pipe* mode prog [args...]
2245 Execute a command in a subprocess, with a pipe to it or from it, or
2246 with pipes in both directions.
2248 @code{open-pipe} runs the shell @var{command} using @samp{/bin/sh -c}.
2249 @code{open-pipe*} executes @var{prog} directly, with the optional
2250 @var{args} arguments (all strings).
2252 @var{mode} should be one of the following values. @code{OPEN_READ} is
2253 an input pipe, ie.@: to read from the subprocess. @code{OPEN_WRITE}
2254 is an output pipe, ie.@: to write to it.
2261 For an input pipe, the child's standard output is the pipe and
2262 standard input is inherited from @code{current-input-port}. For an
2263 output pipe, the child's standard input is the pipe and standard
2264 output is inherited from @code{current-output-port}. In all cases
2265 cases the child's standard error is inherited from
2266 @code{current-error-port} (@pxref{Default Ports}).
2268 If those @code{current-X-ports} are not files of some kind, and hence
2269 don't have file descriptors for the child, then @file{/dev/null} is
2272 Care should be taken with @code{OPEN_BOTH}, a deadlock will occur if
2273 both parent and child are writing, and waiting until the write
2274 completes before doing any reading. Each direction has
2275 @code{PIPE_BUF} bytes of buffering (@pxref{Ports and File
2276 Descriptors}), which will be enough for small writes, but not for say
2277 putting a big file through a filter.
2280 @deffn {Scheme Procedure} open-input-pipe command
2281 Equivalent to @code{open-pipe} with mode @code{OPEN_READ}.
2284 (let* ((port (open-input-pipe "date --utc"))
2285 (str (read-line port)))
2288 @result{} "Mon Mar 11 20:10:44 UTC 2002"
2292 @deffn {Scheme Procedure} open-output-pipe command
2293 Equivalent to @code{open-pipe} with mode @code{OPEN_WRITE}.
2296 (let ((port (open-output-pipe "lpr")))
2297 (display "Something for the line printer.\n" port)
2298 (if (not (eqv? 0 (status:exit-val (close-pipe port))))
2299 (error "Cannot print")))
2303 @deffn {Scheme Procedure} open-input-output-pipe command
2304 Equivalent to @code{open-pipe} with mode @code{OPEN_BOTH}.
2308 @deffn {Scheme Procedure} close-pipe port
2309 Close a pipe created by @code{open-pipe}, wait for the process to
2310 terminate, and return the wait status code. The status is as per
2311 @code{waitpid} and can be decoded with @code{status:exit-val} etc
2316 @code{waitpid WAIT_ANY} should not be used when pipes are open, since
2317 it can reap a pipe's child process, causing an error from a subsequent
2320 @code{close-port} (@pxref{Closing}) can close a pipe, but it doesn't
2321 reap the child process.
2323 The garbage collector will close a pipe no longer in use, and reap the
2324 child process with @code{waitpid}. If the child hasn't yet terminated
2325 the garbage collector doesn't block, but instead checks again in the
2328 Many systems have per-user and system-wide limits on the number of
2329 processes, and a system-wide limit on the number of pipes, so pipes
2330 should be closed explicitly when no longer needed, rather than letting
2331 the garbage collector pick them up at some later time.
2335 @subsection Networking
2339 * Network Address Conversion::
2340 * Network Databases::
2341 * Network Socket Address::
2342 * Network Sockets and Communication::
2343 * Internet Socket Examples::
2346 @node Network Address Conversion
2347 @subsubsection Network Address Conversion
2348 @cindex network address
2350 This section describes procedures which convert internet addresses
2351 between numeric and string formats.
2353 @subsubheading IPv4 Address Conversion
2356 An IPv4 Internet address is a 4-byte value, represented in Guile as an
2357 integer in host byte order, so that say ``0.0.0.1'' is 1, or
2358 ``1.0.0.0'' is 16777216.
2360 Some underlying C functions use network byte order for addresses,
2361 Guile converts as necessary so that at the Scheme level its host byte
2365 For a server, this can be used with @code{bind} (@pxref{Network
2366 Sockets and Communication}) to allow connections from any interface on
2370 @defvar INADDR_BROADCAST
2371 The broadcast address on the local network.
2374 @defvar INADDR_LOOPBACK
2375 The address of the local host using the loopback device, ie.@:
2379 @c INADDR_NONE is defined in the code, but serves no purpose.
2380 @c inet_addr() returns it as an error indication, but that function
2381 @c isn't provided, for the good reason that inet_aton() does the same
2382 @c job and gives an unambiguous error indication. (INADDR_NONE is a
2383 @c valid 4-byte value, in glibc it's the same as INADDR_BROADCAST.)
2385 @c @defvar INADDR_NONE
2389 @deffn {Scheme Procedure} inet-aton address
2390 @deffnx {C Function} scm_inet_aton (address)
2391 This function is deprecated in favor of @code{inet-pton}.
2393 Convert an IPv4 Internet address from printable string
2394 (dotted decimal notation) to an integer. E.g.,
2397 (inet-aton "127.0.0.1") @result{} 2130706433
2401 @deffn {Scheme Procedure} inet-ntoa inetid
2402 @deffnx {C Function} scm_inet_ntoa (inetid)
2403 This function is deprecated in favor of @code{inet-ntop}.
2405 Convert an IPv4 Internet address to a printable
2406 (dotted decimal notation) string. E.g.,
2409 (inet-ntoa 2130706433) @result{} "127.0.0.1"
2413 @deffn {Scheme Procedure} inet-netof address
2414 @deffnx {C Function} scm_inet_netof (address)
2415 Return the network number part of the given IPv4
2416 Internet address. E.g.,
2419 (inet-netof 2130706433) @result{} 127
2423 @deffn {Scheme Procedure} inet-lnaof address
2424 @deffnx {C Function} scm_lnaof (address)
2425 Return the local-address-with-network part of the given
2426 IPv4 Internet address, using the obsolete class A/B/C system.
2430 (inet-lnaof 2130706433) @result{} 1
2434 @deffn {Scheme Procedure} inet-makeaddr net lna
2435 @deffnx {C Function} scm_inet_makeaddr (net, lna)
2436 Make an IPv4 Internet address by combining the network number
2437 @var{net} with the local-address-within-network number
2441 (inet-makeaddr 127 1) @result{} 2130706433
2445 @subsubheading IPv6 Address Conversion
2448 An IPv6 Internet address is a 16-byte value, represented in Guile as
2449 an integer in host byte order, so that say ``::1'' is 1.
2451 @deffn {Scheme Procedure} inet-ntop family address
2452 @deffnx {C Function} scm_inet_ntop (family, address)
2453 Convert a network address from an integer to a printable string.
2454 @var{family} can be @code{AF_INET} or @code{AF_INET6}. E.g.,
2457 (inet-ntop AF_INET 2130706433) @result{} "127.0.0.1"
2458 (inet-ntop AF_INET6 (- (expt 2 128) 1))
2459 @result{} "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"
2463 @deffn {Scheme Procedure} inet-pton family address
2464 @deffnx {C Function} scm_inet_pton (family, address)
2465 Convert a string containing a printable network address to an integer
2466 address. @var{family} can be @code{AF_INET} or @code{AF_INET6}.
2470 (inet-pton AF_INET "127.0.0.1") @result{} 2130706433
2471 (inet-pton AF_INET6 "::1") @result{} 1
2476 @node Network Databases
2477 @subsubsection Network Databases
2478 @cindex network database
2480 This section describes procedures which query various network databases.
2481 Care should be taken when using the database routines since they are not
2484 @subsubheading @code{getaddrinfo}
2486 @cindex @code{addrinfo} object type
2487 @cindex host name lookup
2488 @cindex service name lookup
2490 The @code{getaddrinfo} procedure maps host and service names to socket addresses
2491 and associated information in a protocol-independent way.
2493 @deffn {Scheme Procedure} getaddrinfo name service [hint_flags [hint_family [hint_socktype [hint_protocol]]]]
2494 @deffnx {C Function} scm_getaddrinfo (name, service, hint_flags, hint_family, hint_socktype, hint_protocol)
2495 Return a list of @code{addrinfo} structures containing
2496 a socket address and associated information for host @var{name}
2497 and/or @var{service} to be used in creating a socket with
2498 which to address the specified service.
2501 (let* ((ai (car (getaddrinfo "www.gnu.org" "http")))
2502 (s (socket (addrinfo:fam ai) (addrinfo:socktype ai)
2503 (addrinfo:protocol ai))))
2504 (connect s (addrinfo:addr ai))
2508 When @var{service} is omitted or is @code{#f}, return
2509 network-level addresses for @var{name}. When @var{name}
2510 is @code{#f} @var{service} must be provided and service
2511 locations local to the caller are returned.
2513 Additional hints can be provided. When specified,
2514 @var{hint_flags} should be a bitwise-or of zero or more
2515 constants among the following:
2519 Socket address is intended for @code{bind}.
2522 Request for canonical host name, available via
2523 @code{addrinfo:canonname}. This makes sense mainly when
2524 DNS lookups are involved.
2526 @item AI_NUMERICHOST
2527 Specifies that @var{name} is a numeric host address string
2528 (e.g., @code{"127.0.0.1"}), meaning that name resolution
2531 @item AI_NUMERICSERV
2532 Likewise, specifies that @var{service} is a numeric port
2533 string (e.g., @code{"80"}).
2536 Return only addresses configured on the local system It is
2537 highly recommended to provide this flag when the returned
2538 socket addresses are to be used to make connections;
2539 otherwise, some of the returned addresses could be unreachable
2540 or use a protocol that is not supported.
2543 When looking up IPv6 addresses, return mapped IPv4 addresses if
2544 there is no IPv6 address available at all.
2547 If this flag is set along with @code{AI_V4MAPPED} when looking up IPv6
2548 addresses, return all IPv6 addresses as well as all IPv4 addresses, the latter
2549 mapped to IPv6 format.
2552 When given, @var{hint_family} should specify the requested
2553 address family, e.g., @code{AF_INET6}. Similarly,
2554 @var{hint_socktype} should specify the requested socket type
2555 (e.g., @code{SOCK_DGRAM}), and @var{hint_protocol} should
2556 specify the requested protocol (its value is interpreted
2557 as in calls to @code{socket}).
2559 On error, an exception with key @code{getaddrinfo-error} is
2560 thrown, with an error code (an integer) as its argument:
2563 (catch 'getaddrinfo-error
2565 (getaddrinfo "www.gnu.org" "gopher"))
2566 (lambda (key errcode)
2567 (cond ((= errcode EAI_SERVICE)
2568 (display "doesn't know about Gopher!\n"))
2569 ((= errcode EAI_NONAME)
2570 (display "www.gnu.org not found\\n"))
2572 (format #t "something wrong: ~a\n"
2573 (gai-strerror errcode))))))
2580 The name or service could not be resolved at this time. Future
2581 attempts may succeed.
2584 @var{hint_flags} contains an invalid value.
2587 A non-recoverable error occurred when attempting to
2591 @var{hint_family} was not recognized.
2594 Either @var{name} does not resolve for the supplied parameters,
2595 or neither @var{name} nor @var{service} were supplied.
2598 This non-POSIX error code can be returned on some systems (GNU
2599 and Darwin, at least), for example when @var{name} is known
2600 but requests that were made turned out no data. Error handling
2601 code should be prepared to handle it when it is defined.
2604 @var{service} was not recognized for the specified socket type.
2607 @var{hint_socktype} was not recognized.
2610 A system error occurred. In C, the error code can be found in
2611 @code{errno}; this value is not accessible from Scheme, but in
2612 practice it provides little information about the actual error
2614 @c See <http://bugs.gnu.org/13958>.
2617 Users are encouraged to read the
2618 @url{http://www.opengroup.org/onlinepubs/9699919799/functions/getaddrinfo.html,
2619 "POSIX specification} for more details.
2622 The following procedures take an @code{addrinfo} object as returned by
2625 @deffn {Scheme Procedure} addrinfo:flags ai
2626 Return flags for @var{ai} as a bitwise or of @code{AI_} values (see above).
2629 @deffn {Scheme Procedure} addrinfo:fam ai
2630 Return the address family of @var{ai} (a @code{AF_} value).
2633 @deffn {Scheme Procedure} addrinfo:socktype ai
2634 Return the socket type for @var{ai} (a @code{SOCK_} value).
2637 @deffn {Scheme Procedure} addrinfo:protocol ai
2638 Return the protocol of @var{ai}.
2641 @deffn {Scheme Procedure} addrinfo:addr ai
2642 Return the socket address associated with @var{ai} as a @code{sockaddr}
2643 object (@pxref{Network Socket Address}).
2646 @deffn {Scheme Procedure} addrinfo:canonname ai
2647 Return a string for the canonical name associated with @var{ai} if
2648 the @code{AI_CANONNAME} flag was supplied.
2651 @subsubheading The Host Database
2652 @cindex @file{/etc/hosts}
2653 @cindex network database
2655 A @dfn{host object} is a structure that represents what is known about a
2656 network host, and is the usual way of representing a system's network
2657 identity inside software.
2659 The following functions accept a host object and return a selected
2662 @deffn {Scheme Procedure} hostent:name host
2663 The ``official'' hostname for @var{host}.
2665 @deffn {Scheme Procedure} hostent:aliases host
2666 A list of aliases for @var{host}.
2668 @deffn {Scheme Procedure} hostent:addrtype host
2669 The host address type, one of the @code{AF} constants, such as
2670 @code{AF_INET} or @code{AF_INET6}.
2672 @deffn {Scheme Procedure} hostent:length host
2673 The length of each address for @var{host}, in bytes.
2675 @deffn {Scheme Procedure} hostent:addr-list host
2676 The list of network addresses associated with @var{host}. For
2677 @code{AF_INET} these are integer IPv4 address (@pxref{Network Address
2681 The following procedures can be used to search the host database. However,
2682 @code{getaddrinfo} should be preferred over them since it's more generic and
2685 @deffn {Scheme Procedure} gethost [host]
2686 @deffnx {Scheme Procedure} gethostbyname hostname
2687 @deffnx {Scheme Procedure} gethostbyaddr address
2688 @deffnx {C Function} scm_gethost (host)
2689 Look up a host by name or address, returning a host object. The
2690 @code{gethost} procedure will accept either a string name or an integer
2691 address; if given no arguments, it behaves like @code{gethostent} (see
2692 below). If a name or address is supplied but the address can not be
2693 found, an error will be thrown to one of the keys:
2694 @code{host-not-found}, @code{try-again}, @code{no-recovery} or
2695 @code{no-data}, corresponding to the equivalent @code{h_error} values.
2696 Unusual conditions may result in errors thrown to the
2697 @code{system-error} or @code{misc_error} keys.
2700 (gethost "www.gnu.org")
2701 @result{} #("www.gnu.org" () 2 4 (3353880842))
2703 (gethostbyname "www.emacs.org")
2704 @result{} #("emacs.org" ("www.emacs.org") 2 4 (1073448978))
2708 The following procedures may be used to step through the host
2709 database from beginning to end.
2711 @deffn {Scheme Procedure} sethostent [stayopen]
2712 Initialize an internal stream from which host objects may be read. This
2713 procedure must be called before any calls to @code{gethostent}, and may
2714 also be called afterward to reset the host entry stream. If
2715 @var{stayopen} is supplied and is not @code{#f}, the database is not
2716 closed by subsequent @code{gethostbyname} or @code{gethostbyaddr} calls,
2717 possibly giving an efficiency gain.
2720 @deffn {Scheme Procedure} gethostent
2721 Return the next host object from the host database, or @code{#f} if
2722 there are no more hosts to be found (or an error has been encountered).
2723 This procedure may not be used before @code{sethostent} has been called.
2726 @deffn {Scheme Procedure} endhostent
2727 Close the stream used by @code{gethostent}. The return value is unspecified.
2730 @deffn {Scheme Procedure} sethost [stayopen]
2731 @deffnx {C Function} scm_sethost (stayopen)
2732 If @var{stayopen} is omitted, this is equivalent to @code{endhostent}.
2733 Otherwise it is equivalent to @code{sethostent stayopen}.
2736 @subsubheading The Network Database
2737 @cindex network database
2739 The following functions accept an object representing a network
2740 and return a selected component:
2742 @deffn {Scheme Procedure} netent:name net
2743 The ``official'' network name.
2745 @deffn {Scheme Procedure} netent:aliases net
2746 A list of aliases for the network.
2748 @deffn {Scheme Procedure} netent:addrtype net
2749 The type of the network number. Currently, this returns only
2752 @deffn {Scheme Procedure} netent:net net
2756 The following procedures are used to search the network database:
2758 @deffn {Scheme Procedure} getnet [net]
2759 @deffnx {Scheme Procedure} getnetbyname net-name
2760 @deffnx {Scheme Procedure} getnetbyaddr net-number
2761 @deffnx {C Function} scm_getnet (net)
2762 Look up a network by name or net number in the network database. The
2763 @var{net-name} argument must be a string, and the @var{net-number}
2764 argument must be an integer. @code{getnet} will accept either type of
2765 argument, behaving like @code{getnetent} (see below) if no arguments are
2769 The following procedures may be used to step through the network
2770 database from beginning to end.
2772 @deffn {Scheme Procedure} setnetent [stayopen]
2773 Initialize an internal stream from which network objects may be read. This
2774 procedure must be called before any calls to @code{getnetent}, and may
2775 also be called afterward to reset the net entry stream. If
2776 @var{stayopen} is supplied and is not @code{#f}, the database is not
2777 closed by subsequent @code{getnetbyname} or @code{getnetbyaddr} calls,
2778 possibly giving an efficiency gain.
2781 @deffn {Scheme Procedure} getnetent
2782 Return the next entry from the network database.
2785 @deffn {Scheme Procedure} endnetent
2786 Close the stream used by @code{getnetent}. The return value is unspecified.
2789 @deffn {Scheme Procedure} setnet [stayopen]
2790 @deffnx {C Function} scm_setnet (stayopen)
2791 If @var{stayopen} is omitted, this is equivalent to @code{endnetent}.
2792 Otherwise it is equivalent to @code{setnetent stayopen}.
2795 @subsubheading The Protocol Database
2796 @cindex @file{/etc/protocols}
2798 @cindex network protocols
2800 The following functions accept an object representing a protocol
2801 and return a selected component:
2803 @deffn {Scheme Procedure} protoent:name protocol
2804 The ``official'' protocol name.
2806 @deffn {Scheme Procedure} protoent:aliases protocol
2807 A list of aliases for the protocol.
2809 @deffn {Scheme Procedure} protoent:proto protocol
2810 The protocol number.
2813 The following procedures are used to search the protocol database:
2815 @deffn {Scheme Procedure} getproto [protocol]
2816 @deffnx {Scheme Procedure} getprotobyname name
2817 @deffnx {Scheme Procedure} getprotobynumber number
2818 @deffnx {C Function} scm_getproto (protocol)
2819 Look up a network protocol by name or by number. @code{getprotobyname}
2820 takes a string argument, and @code{getprotobynumber} takes an integer
2821 argument. @code{getproto} will accept either type, behaving like
2822 @code{getprotoent} (see below) if no arguments are supplied.
2825 The following procedures may be used to step through the protocol
2826 database from beginning to end.
2828 @deffn {Scheme Procedure} setprotoent [stayopen]
2829 Initialize an internal stream from which protocol objects may be read. This
2830 procedure must be called before any calls to @code{getprotoent}, and may
2831 also be called afterward to reset the protocol entry stream. If
2832 @var{stayopen} is supplied and is not @code{#f}, the database is not
2833 closed by subsequent @code{getprotobyname} or @code{getprotobynumber} calls,
2834 possibly giving an efficiency gain.
2837 @deffn {Scheme Procedure} getprotoent
2838 Return the next entry from the protocol database.
2841 @deffn {Scheme Procedure} endprotoent
2842 Close the stream used by @code{getprotoent}. The return value is unspecified.
2845 @deffn {Scheme Procedure} setproto [stayopen]
2846 @deffnx {C Function} scm_setproto (stayopen)
2847 If @var{stayopen} is omitted, this is equivalent to @code{endprotoent}.
2848 Otherwise it is equivalent to @code{setprotoent stayopen}.
2851 @subsubheading The Service Database
2852 @cindex @file{/etc/services}
2854 @cindex network services
2856 The following functions accept an object representing a service
2857 and return a selected component:
2859 @deffn {Scheme Procedure} servent:name serv
2860 The ``official'' name of the network service.
2862 @deffn {Scheme Procedure} servent:aliases serv
2863 A list of aliases for the network service.
2865 @deffn {Scheme Procedure} servent:port serv
2866 The Internet port used by the service.
2868 @deffn {Scheme Procedure} servent:proto serv
2869 The protocol used by the service. A service may be listed many times
2870 in the database under different protocol names.
2873 The following procedures are used to search the service database:
2875 @deffn {Scheme Procedure} getserv [name [protocol]]
2876 @deffnx {Scheme Procedure} getservbyname name protocol
2877 @deffnx {Scheme Procedure} getservbyport port protocol
2878 @deffnx {C Function} scm_getserv (name, protocol)
2879 Look up a network service by name or by service number, and return a
2880 network service object. The @var{protocol} argument specifies the name
2881 of the desired protocol; if the protocol found in the network service
2882 database does not match this name, a system error is signalled.
2884 The @code{getserv} procedure will take either a service name or number
2885 as its first argument; if given no arguments, it behaves like
2886 @code{getservent} (see below).
2889 (getserv "imap" "tcp")
2890 @result{} #("imap2" ("imap") 143 "tcp")
2892 (getservbyport 88 "udp")
2893 @result{} #("kerberos" ("kerberos5" "krb5") 88 "udp")
2897 The following procedures may be used to step through the service
2898 database from beginning to end.
2900 @deffn {Scheme Procedure} setservent [stayopen]
2901 Initialize an internal stream from which service objects may be read. This
2902 procedure must be called before any calls to @code{getservent}, and may
2903 also be called afterward to reset the service entry stream. If
2904 @var{stayopen} is supplied and is not @code{#f}, the database is not
2905 closed by subsequent @code{getservbyname} or @code{getservbyport} calls,
2906 possibly giving an efficiency gain.
2909 @deffn {Scheme Procedure} getservent
2910 Return the next entry from the services database.
2913 @deffn {Scheme Procedure} endservent
2914 Close the stream used by @code{getservent}. The return value is unspecified.
2917 @deffn {Scheme Procedure} setserv [stayopen]
2918 @deffnx {C Function} scm_setserv (stayopen)
2919 If @var{stayopen} is omitted, this is equivalent to @code{endservent}.
2920 Otherwise it is equivalent to @code{setservent stayopen}.
2924 @node Network Socket Address
2925 @subsubsection Network Socket Address
2926 @cindex socket address
2927 @cindex network socket address
2928 @tpindex Socket address
2930 A @dfn{socket address} object identifies a socket endpoint for
2931 communication. In the case of @code{AF_INET} for instance, the socket
2932 address object comprises the host address (or interface on the host)
2933 and a port number which specifies a particular open socket in a
2934 running client or server process. A socket address object can be
2937 @deffn {Scheme Procedure} make-socket-address AF_INET ipv4addr port
2938 @deffnx {Scheme Procedure} make-socket-address AF_INET6 ipv6addr port [flowinfo [scopeid]]
2939 @deffnx {Scheme Procedure} make-socket-address AF_UNIX path
2940 @deffnx {C Function} scm_make_socket_address (family, address, arglist)
2941 Return a new socket address object. The first argument is the address
2942 family, one of the @code{AF} constants, then the arguments vary
2943 according to the family.
2945 For @code{AF_INET} the arguments are an IPv4 network address number
2946 (@pxref{Network Address Conversion}), and a port number.
2948 For @code{AF_INET6} the arguments are an IPv6 network address number
2949 and a port number. Optional @var{flowinfo} and @var{scopeid}
2950 arguments may be given (both integers, default 0).
2952 For @code{AF_UNIX} the argument is a filename (a string).
2954 The C function @code{scm_make_socket_address} takes the @var{family}
2955 and @var{address} arguments directly, then @var{arglist} is a list of
2956 further arguments, being the port for IPv4, port and optional flowinfo
2957 and scopeid for IPv6, or the empty list @code{SCM_EOL} for Unix
2962 The following functions access the fields of a socket address object,
2964 @deffn {Scheme Procedure} sockaddr:fam sa
2965 Return the address family from socket address object @var{sa}. This
2966 is one of the @code{AF} constants (e.g.@: @code{AF_INET}).
2969 @deffn {Scheme Procedure} sockaddr:path sa
2970 For an @code{AF_UNIX} socket address object @var{sa}, return the
2974 @deffn {Scheme Procedure} sockaddr:addr sa
2975 For an @code{AF_INET} or @code{AF_INET6} socket address object
2976 @var{sa}, return the network address number.
2979 @deffn {Scheme Procedure} sockaddr:port sa
2980 For an @code{AF_INET} or @code{AF_INET6} socket address object
2981 @var{sa}, return the port number.
2984 @deffn {Scheme Procedure} sockaddr:flowinfo sa
2985 For an @code{AF_INET6} socket address object @var{sa}, return the
2989 @deffn {Scheme Procedure} sockaddr:scopeid sa
2990 For an @code{AF_INET6} socket address object @var{sa}, return the
2994 @tpindex @code{struct sockaddr}
2995 @tpindex @code{sockaddr}
2996 The functions below convert to and from the C @code{struct sockaddr}
2997 (@pxref{Address Formats,,, libc, The GNU C Library Reference Manual}).
2998 That structure is a generic type, an application can cast to or from
2999 @code{struct sockaddr_in}, @code{struct sockaddr_in6} or @code{struct
3000 sockaddr_un} according to the address family.
3002 In a @code{struct sockaddr} taken or returned, the byte ordering in
3003 the fields follows the C conventions (@pxref{Byte Order,, Byte Order
3004 Conversion, libc, The GNU C Library Reference Manual}). This means
3005 network byte order for @code{AF_INET} host address
3006 (@code{sin_addr.s_addr}) and port number (@code{sin_port}), and
3007 @code{AF_INET6} port number (@code{sin6_port}). But at the Scheme
3008 level these values are taken or returned in host byte order, so the
3009 port is an ordinary integer, and the host address likewise is an
3010 ordinary integer (as described in @ref{Network Address Conversion}).
3012 @deftypefn {C Function} {struct sockaddr *} scm_c_make_socket_address (SCM family, SCM address, SCM args, size_t *outsize)
3013 Return a newly-@code{malloc}ed @code{struct sockaddr} created from
3014 arguments like those taken by @code{scm_make_socket_address} above.
3016 The size (in bytes) of the @code{struct sockaddr} return is stored
3017 into @code{*@var{outsize}}. An application must call @code{free} to
3018 release the returned structure when no longer required.
3021 @deftypefn {C Function} SCM scm_from_sockaddr (const struct sockaddr *address, unsigned address_size)
3022 Return a Scheme socket address object from the C @var{address}
3023 structure. @var{address_size} is the size in bytes of @var{address}.
3026 @deftypefn {C Function} {struct sockaddr *} scm_to_sockaddr (SCM address, size_t *address_size)
3027 Return a newly-@code{malloc}ed @code{struct sockaddr} from a Scheme
3028 level socket address object.
3030 The size (in bytes) of the @code{struct sockaddr} return is stored
3031 into @code{*@var{outsize}}. An application must call @code{free} to
3032 release the returned structure when no longer required.
3036 @node Network Sockets and Communication
3037 @subsubsection Network Sockets and Communication
3039 @cindex network socket
3041 Socket ports can be created using @code{socket} and @code{socketpair}.
3042 The ports are initially unbuffered, to make reading and writing to the
3043 same port more reliable. A buffer can be added to the port using
3044 @code{setvbuf}; see @ref{Ports and File Descriptors}.
3046 Most systems have limits on how many files and sockets can be open, so
3047 it's strongly recommended that socket ports be closed explicitly when
3048 no longer required (@pxref{Ports}).
3050 Some of the underlying C functions take values in network byte order,
3051 but the convention in Guile is that at the Scheme level everything is
3052 ordinary host byte order and conversions are made automatically where
3055 @deffn {Scheme Procedure} socket family style proto
3056 @deffnx {C Function} scm_socket (family, style, proto)
3057 Return a new socket port of the type specified by @var{family},
3058 @var{style} and @var{proto}. All three parameters are integers. The
3059 possible values for @var{family} are as follows, where supported by
3067 The possible values for @var{style} are as follows, again where
3068 supported by the system,
3074 @defvarx SOCK_SEQPACKET
3077 @var{proto} can be obtained from a protocol name using
3078 @code{getprotobyname} (@pxref{Network Databases}). A value of zero
3079 means the default protocol, which is usually right.
3081 A socket cannot by used for communication until it has been connected
3082 somewhere, usually with either @code{connect} or @code{accept} below.
3085 @deffn {Scheme Procedure} socketpair family style proto
3086 @deffnx {C Function} scm_socketpair (family, style, proto)
3087 Return a pair, the @code{car} and @code{cdr} of which are two unnamed
3088 socket ports connected to each other. The connection is full-duplex,
3089 so data can be transferred in either direction between the two.
3091 @var{family}, @var{style} and @var{proto} are as per @code{socket}
3092 above. But many systems only support socket pairs in the
3093 @code{PF_UNIX} family. Zero is likely to be the only meaningful value
3097 @deffn {Scheme Procedure} getsockopt sock level optname
3098 @deffnx {Scheme Procedure} setsockopt sock level optname value
3099 @deffnx {C Function} scm_getsockopt (sock, level, optname)
3100 @deffnx {C Function} scm_setsockopt (sock, level, optname, value)
3101 Get or set an option on socket port @var{sock}. @code{getsockopt}
3102 returns the current value. @code{setsockopt} sets a value and the
3103 return is unspecified.
3105 @var{level} is an integer specifying a protocol layer, either
3106 @code{SOL_SOCKET} for socket level options, or a protocol number from
3107 the @code{IPPROTO} constants or @code{getprotoent} (@pxref{Network
3112 @defvarx IPPROTO_TCP
3113 @defvarx IPPROTO_UDP
3116 @var{optname} is an integer specifying an option within the protocol
3119 For @code{SOL_SOCKET} level the following @var{optname}s are defined
3120 (when provided by the system). For their meaning see
3121 @ref{Socket-Level Options,,, libc, The GNU C Library Reference
3122 Manual}, or @command{man 7 socket}.
3125 @defvarx SO_REUSEADDR
3129 @defvarx SO_DONTROUTE
3130 @defvarx SO_BROADCAST
3133 @defvarx SO_KEEPALIVE
3134 @defvarx SO_OOBINLINE
3135 @defvarx SO_NO_CHECK
3136 @defvarx SO_PRIORITY
3137 @defvarx SO_REUSEPORT
3138 The @var{value} taken or returned is an integer.
3142 The @var{value} taken or returned is a pair of integers
3143 @code{(@var{ENABLE} . @var{TIMEOUT})}. On old systems without timeout
3144 support (ie.@: without @code{struct linger}), only @var{ENABLE} has an
3145 effect but the value in Guile is always a pair.
3148 @c Note that we refer only to ``man ip'' here. On GNU/Linux it's
3149 @c ``man 7 ip'' but on NetBSD it's ``man 4 ip''.
3151 For IP level (@code{IPPROTO_IP}) the following @var{optname}s are
3152 defined (when provided by the system). See @command{man ip} for what
3155 @defvar IP_MULTICAST_IF
3156 This sets the source interface used by multicast traffic.
3159 @defvar IP_MULTICAST_TTL
3160 This sets the default TTL for multicast traffic. This defaults
3161 to 1 and should be increased to allow traffic to pass beyond the
3165 @defvar IP_ADD_MEMBERSHIP
3166 @defvarx IP_DROP_MEMBERSHIP
3167 These can be used only with @code{setsockopt}, not @code{getsockopt}.
3168 @var{value} is a pair @code{(@var{MULTIADDR} . @var{INTERFACEADDR})}
3169 of integer IPv4 addresses (@pxref{Network Address Conversion}).
3170 @var{MULTIADDR} is a multicast address to be added to or dropped from
3171 the interface @var{INTERFACEADDR}. @var{INTERFACEADDR} can be
3172 @code{INADDR_ANY} to have the system select the interface.
3173 @var{INTERFACEADDR} can also be an interface index number, on systems
3178 @deffn {Scheme Procedure} shutdown sock how
3179 @deffnx {C Function} scm_shutdown (sock, how)
3180 Sockets can be closed simply by using @code{close-port}. The
3181 @code{shutdown} procedure allows reception or transmission on a
3182 connection to be shut down individually, according to the parameter
3187 Stop receiving data for this socket. If further data arrives, reject it.
3189 Stop trying to transmit data from this socket. Discard any
3190 data waiting to be sent. Stop looking for acknowledgement of
3191 data already sent; don't retransmit it if it is lost.
3193 Stop both reception and transmission.
3196 The return value is unspecified.
3199 @deffn {Scheme Procedure} connect sock sockaddr
3200 @deffnx {Scheme Procedure} connect sock AF_INET ipv4addr port
3201 @deffnx {Scheme Procedure} connect sock AF_INET6 ipv6addr port [flowinfo [scopeid]]
3202 @deffnx {Scheme Procedure} connect sock AF_UNIX path
3203 @deffnx {C Function} scm_connect (sock, fam, address, args)
3204 Initiate a connection on socket port @var{sock} to a given address.
3205 The destination is either a socket address object, or arguments the
3206 same as @code{make-socket-address} would take to make such an object
3207 (@pxref{Network Socket Address}). The return value is unspecified.
3210 (connect sock AF_INET INADDR_LOOPBACK 23)
3211 (connect sock (make-socket-address AF_INET INADDR_LOOPBACK 23))
3215 @deffn {Scheme Procedure} bind sock sockaddr
3216 @deffnx {Scheme Procedure} bind sock AF_INET ipv4addr port
3217 @deffnx {Scheme Procedure} bind sock AF_INET6 ipv6addr port [flowinfo [scopeid]]
3218 @deffnx {Scheme Procedure} bind sock AF_UNIX path
3219 @deffnx {C Function} scm_bind (sock, fam, address, args)
3220 Bind socket port @var{sock} to the given address. The address is
3221 either a socket address object, or arguments the same as
3222 @code{make-socket-address} would take to make such an object
3223 (@pxref{Network Socket Address}). The return value is unspecified.
3225 Generally a socket is only explicitly bound to a particular address
3226 when making a server, i.e.@: to listen on a particular port. For an
3227 outgoing connection the system will assign a local address
3228 automatically, if not already bound.
3231 (bind sock AF_INET INADDR_ANY 12345)
3232 (bind sock (make-socket-address AF_INET INADDR_ANY 12345))
3236 @deffn {Scheme Procedure} listen sock backlog
3237 @deffnx {C Function} scm_listen (sock, backlog)
3238 Enable @var{sock} to accept connection
3239 requests. @var{backlog} is an integer specifying
3240 the maximum length of the queue for pending connections.
3241 If the queue fills, new clients will fail to connect until
3242 the server calls @code{accept} to accept a connection from
3245 The return value is unspecified.
3248 @deffn {Scheme Procedure} accept sock
3249 @deffnx {C Function} scm_accept (sock)
3250 Accept a connection from socket port @var{sock} which has been enabled
3251 for listening with @code{listen} above. If there are no incoming
3252 connections in the queue, wait until one is available (unless
3253 @code{O_NONBLOCK} has been set on the socket, @pxref{Ports and File
3254 Descriptors,@code{fcntl}}).
3256 The return value is a pair. The @code{car} is a new socket port,
3257 connected and ready to communicate. The @code{cdr} is a socket
3258 address object (@pxref{Network Socket Address}) which is where the
3259 remote connection is from (like @code{getpeername} below).
3261 All communication takes place using the new socket returned. The
3262 given @var{sock} remains bound and listening, and @code{accept} may be
3263 called on it again to get another incoming connection when desired.
3266 @deffn {Scheme Procedure} getsockname sock
3267 @deffnx {C Function} scm_getsockname (sock)
3268 Return a socket address object which is the where @var{sock} is bound
3269 locally. @var{sock} may have obtained its local address from
3270 @code{bind} (above), or if a @code{connect} is done with an otherwise
3271 unbound socket (which is usual) then the system will have assigned an
3274 Note that on many systems the address of a socket in the
3275 @code{AF_UNIX} namespace cannot be read.
3278 @deffn {Scheme Procedure} getpeername sock
3279 @deffnx {C Function} scm_getpeername (sock)
3280 Return a socket address object which is where @var{sock} is connected
3281 to, i.e.@: the remote endpoint.
3283 Note that on many systems the address of a socket in the
3284 @code{AF_UNIX} namespace cannot be read.
3287 @deffn {Scheme Procedure} recv! sock buf [flags]
3288 @deffnx {C Function} scm_recv (sock, buf, flags)
3289 Receive data from a socket port.
3290 @var{sock} must already
3291 be bound to the address from which data is to be received.
3292 @var{buf} is a bytevector into which
3293 the data will be written. The size of @var{buf} limits
3295 data which can be received: in the case of packet
3296 protocols, if a packet larger than this limit is encountered
3298 will be irrevocably lost.
3302 @vindex MSG_DONTROUTE
3303 The optional @var{flags} argument is a value or bitwise OR of
3304 @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3306 The value returned is the number of bytes read from the
3309 Note that the data is read directly from the socket file
3311 any unread buffered port data is ignored.
3314 @deffn {Scheme Procedure} send sock message [flags]
3315 @deffnx {C Function} scm_send (sock, message, flags)
3318 @vindex MSG_DONTROUTE
3319 Transmit bytevector @var{message} on socket port @var{sock}.
3320 @var{sock} must already be bound to a destination address. The value
3321 returned is the number of bytes transmitted---it's possible for this
3322 to be less than the length of @var{message} if the socket is set to be
3323 non-blocking. The optional @var{flags} argument is a value or bitwise
3324 OR of @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3326 Note that the data is written directly to the socket
3328 any unflushed buffered port data is ignored.
3331 @deffn {Scheme Procedure} recvfrom! sock buf [flags [start [end]]]
3332 @deffnx {C Function} scm_recvfrom (sock, buf, flags, start, end)
3333 Receive data from socket port @var{sock}, returning the originating
3334 address as well as the data. This function is usually for datagram
3335 sockets, but can be used on stream-oriented sockets too.
3337 The data received is stored in bytevector @var{buf}, using
3338 either the whole bytevector or just the region between the optional
3339 @var{start} and @var{end} positions. The size of @var{buf}
3340 limits the amount of data that can be received. For datagram
3341 protocols if a packet larger than this is received then excess
3342 bytes are irrevocably lost.
3344 The return value is a pair. The @code{car} is the number of bytes
3345 read. The @code{cdr} is a socket address object (@pxref{Network
3346 Socket Address}) which is where the data came from, or @code{#f} if
3347 the origin is unknown.
3351 @vindex MSG_DONTROUTE
3352 The optional @var{flags} argument is a or bitwise-OR (@code{logior})
3353 of @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3355 Data is read directly from the socket file descriptor, any buffered
3356 port data is ignored.
3358 @c This was linux kernel 2.6.15 and glibc 2.3.6, not sure what any
3359 @c specs are supposed to say about recvfrom threading.
3361 On a GNU/Linux system @code{recvfrom!} is not multi-threading, all
3362 threads stop while a @code{recvfrom!} call is in progress. An
3363 application may need to use @code{select}, @code{O_NONBLOCK} or
3364 @code{MSG_DONTWAIT} to avoid this.
3367 @deffn {Scheme Procedure} sendto sock message sockaddr [flags]
3368 @deffnx {Scheme Procedure} sendto sock message AF_INET ipv4addr port [flags]
3369 @deffnx {Scheme Procedure} sendto sock message AF_INET6 ipv6addr port [flowinfo [scopeid [flags]]]
3370 @deffnx {Scheme Procedure} sendto sock message AF_UNIX path [flags]
3371 @deffnx {C Function} scm_sendto (sock, message, fam, address, args_and_flags)
3372 Transmit bytevector @var{message} as a datagram socket port
3373 @var{sock}. The destination is specified either as a socket address
3374 object, or as arguments the same as would be taken by
3375 @code{make-socket-address} to create such an object (@pxref{Network
3378 The destination address may be followed by an optional @var{flags}
3379 argument which is a @code{logior} (@pxref{Bitwise Operations}) of
3380 @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3382 The value returned is the number of bytes transmitted --
3384 this to be less than the length of @var{message} if the
3386 set to be non-blocking.
3387 Note that the data is written directly to the socket
3389 any unflushed buffered port data is ignored.
3392 The following functions can be used to convert short and long integers
3393 between ``host'' and ``network'' order. Although the procedures above do
3394 this automatically for addresses, the conversion will still need to
3395 be done when sending or receiving encoded integer data from the network.
3397 @deffn {Scheme Procedure} htons value
3398 @deffnx {C Function} scm_htons (value)
3399 Convert a 16 bit quantity from host to network byte ordering.
3400 @var{value} is packed into 2 bytes, which are then converted
3401 and returned as a new integer.
3404 @deffn {Scheme Procedure} ntohs value
3405 @deffnx {C Function} scm_ntohs (value)
3406 Convert a 16 bit quantity from network to host byte ordering.
3407 @var{value} is packed into 2 bytes, which are then converted
3408 and returned as a new integer.
3411 @deffn {Scheme Procedure} htonl value
3412 @deffnx {C Function} scm_htonl (value)
3413 Convert a 32 bit quantity from host to network byte ordering.
3414 @var{value} is packed into 4 bytes, which are then converted
3415 and returned as a new integer.
3418 @deffn {Scheme Procedure} ntohl value
3419 @deffnx {C Function} scm_ntohl (value)
3420 Convert a 32 bit quantity from network to host byte ordering.
3421 @var{value} is packed into 4 bytes, which are then converted
3422 and returned as a new integer.
3425 These procedures are inconvenient to use at present, but consider:
3428 (define write-network-long
3429 (lambda (value port)
3430 (let ((v (make-uniform-vector 1 1 0)))
3431 (uniform-vector-set! v 0 (htonl value))
3432 (uniform-vector-write v port))))
3434 (define read-network-long
3436 (let ((v (make-uniform-vector 1 1 0)))
3437 (uniform-vector-read! v port)
3438 (ntohl (uniform-vector-ref v 0)))))
3442 @node Internet Socket Examples
3443 @subsubsection Network Socket Examples
3444 @cindex network examples
3445 @cindex socket examples
3447 The following give examples of how to use network sockets.
3449 @subsubheading Internet Socket Client Example
3451 @cindex socket client example
3452 The following example demonstrates an Internet socket client.
3453 It connects to the HTTP daemon running on the local machine and
3454 returns the contents of the root index URL.
3457 (let ((s (socket PF_INET SOCK_STREAM 0)))
3458 (connect s AF_INET (inet-pton AF_INET "127.0.0.1") 80)
3459 (display "GET / HTTP/1.0\r\n\r\n" s)
3461 (do ((line (read-line s) (read-line s)))
3462 ((eof-object? line))
3468 @subsubheading Internet Socket Server Example
3470 @cindex socket server example
3471 The following example shows a simple Internet server which listens on
3472 port 2904 for incoming connections and sends a greeting back to the
3476 (let ((s (socket PF_INET SOCK_STREAM 0)))
3477 (setsockopt s SOL_SOCKET SO_REUSEADDR 1)
3478 ;; @r{Specific address?}
3479 ;; @r{(bind s AF_INET (inet-pton AF_INET "127.0.0.1") 2904)}
3480 (bind s AF_INET INADDR_ANY 2904)
3483 (simple-format #t "Listening for clients in pid: ~S" (getpid))
3487 (let* ((client-connection (accept s))
3488 (client-details (cdr client-connection))
3489 (client (car client-connection)))
3490 (simple-format #t "Got new client connection: ~S"
3493 (simple-format #t "Client address: ~S"
3495 (sockaddr:addr client-details)))
3497 ;; @r{Send back the greeting to the client port}
3498 (display "Hello client\r\n" client)
3503 @node System Identification
3504 @subsection System Identification
3507 This section lists the various procedures Guile provides for accessing
3508 information about the system it runs on.
3510 @deffn {Scheme Procedure} uname
3511 @deffnx {C Function} scm_uname ()
3512 Return an object with some information about the computer
3513 system the program is running on.
3515 The following procedures accept an object as returned by @code{uname}
3516 and return a selected component (all of which are strings).
3518 @deffn {Scheme Procedure} utsname:sysname un
3519 The name of the operating system.
3521 @deffn {Scheme Procedure} utsname:nodename un
3522 The network name of the computer.
3524 @deffn {Scheme Procedure} utsname:release un
3525 The current release level of the operating system implementation.
3527 @deffn {Scheme Procedure} utsname:version un
3528 The current version level within the release of the operating system.
3530 @deffn {Scheme Procedure} utsname:machine un
3531 A description of the hardware.
3535 @deffn {Scheme Procedure} gethostname
3536 @deffnx {C Function} scm_gethostname ()
3538 Return the host name of the current processor.
3541 @deffn {Scheme Procedure} sethostname name
3542 @deffnx {C Function} scm_sethostname (name)
3543 Set the host name of the current processor to @var{name}. May
3544 only be used by the superuser. The return value is not
3552 @deffn {Scheme Procedure} setlocale category [locale]
3553 @deffnx {C Function} scm_setlocale (category, locale)
3554 Get or set the current locale, used for various internationalizations.
3555 Locales are strings, such as @samp{sv_SE}.
3557 If @var{locale} is given then the locale for the given @var{category}
3558 is set and the new value returned. If @var{locale} is not given then
3559 the current value is returned. @var{category} should be one of the
3560 following values (@pxref{Locale Categories, Categories of Activities
3561 that Locales Affect,, libc, The GNU C Library Reference Manual}):
3566 @defvarx LC_MESSAGES
3567 @defvarx LC_MONETARY
3573 A common usage is @samp{(setlocale LC_ALL "")}, which initializes all
3574 categories based on standard environment variables (@code{LANG} etc).
3575 For full details on categories and locale names @pxref{Locales,,
3576 Locales and Internationalization, libc, The GNU C Library Reference
3579 Note that @code{setlocale} affects locale settings for the whole
3580 process. @xref{i18n Introduction, locale objects and
3581 @code{make-locale}}, for a thread-safe alternative.
3585 @subsection Encryption
3588 Please note that the procedures in this section are not suited for
3589 strong encryption, they are only interfaces to the well-known and
3590 common system library functions of the same name. They are just as good
3591 (or bad) as the underlying functions, so you should refer to your system
3592 documentation before using them (@pxref{crypt,, Encrypting Passwords,
3593 libc, The GNU C Library Reference Manual}).
3595 @deffn {Scheme Procedure} crypt key salt
3596 @deffnx {C Function} scm_crypt (key, salt)
3597 Encrypt @var{key}, with the addition of @var{salt} (both strings),
3598 using the @code{crypt} C library call.
3601 Although @code{getpass} is not an encryption procedure per se, it
3602 appears here because it is often used in combination with @code{crypt}:
3604 @deffn {Scheme Procedure} getpass prompt
3605 @deffnx {C Function} scm_getpass (prompt)
3607 Display @var{prompt} to the standard error output and read
3608 a password from @file{/dev/tty}. If this file is not
3609 accessible, it reads from standard input. The password may be
3610 up to 127 characters in length. Additional characters and the
3611 terminating newline character are discarded. While reading
3612 the password, echoing and the generation of signals by special
3613 characters is disabled.
3618 @c TeX-master: "guile.texi"