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 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 fd
215 @deffnx {C Function} scm_fdes_to_ports (fd)
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 fd
234 @deffnx {C Function} scm_primitive_move_to_fdes (port, fd)
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 object
256 @deffnx {C Function} scm_fsync (object)
257 Copies any unwritten data for the specified output file descriptor to disk.
258 If @var{port/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 new
406 @deffnx {C Function} scm_redirect_port (old, new)
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{obj}. @var{obj} 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.
692 @deffn {Scheme Procedure} stat:mtime st
693 The last modification time for the file.
695 @deffn {Scheme Procedure} stat:ctime st
696 The last modification time for the attributes of the file.
698 @deffn {Scheme Procedure} stat:blksize st
699 The optimal block size for reading or writing the file, in bytes. On
700 some systems this field is not available, in which case
701 @code{stat:blksize} returns a sensible suggested block size.
703 @deffn {Scheme Procedure} stat:blocks st
704 The amount of disk space that the file occupies measured in units of
705 512 byte blocks. On some systems this field is not available, in
706 which case @code{stat:blocks} returns @code{#f}.
709 In addition, the following procedures return the information
710 from @code{stat:mode} in a more convenient form:
712 @deffn {Scheme Procedure} stat:type st
713 A symbol representing the type of file. Possible values are
714 @samp{regular}, @samp{directory}, @samp{symlink},
715 @samp{block-special}, @samp{char-special}, @samp{fifo}, @samp{socket},
718 @deffn {Scheme Procedure} stat:perms st
719 An integer representing the access permission bits.
723 @deffn {Scheme Procedure} lstat str
724 @deffnx {C Function} scm_lstat (str)
725 Similar to @code{stat}, but does not follow symbolic links, i.e.,
726 it will return information about a symbolic link itself, not the
727 file it points to. @var{path} must be a string.
730 @deffn {Scheme Procedure} readlink path
731 @deffnx {C Function} scm_readlink (path)
732 Return the value of the symbolic link named by @var{path} (a
733 string), i.e., the file that the link points to.
738 @deffn {Scheme Procedure} chown object owner group
739 @deffnx {C Function} scm_chown (object, owner, group)
740 Change the ownership and group of the file referred to by @var{object}
741 to the integer values @var{owner} and @var{group}. @var{object} can
742 be a string containing a file name or, if the platform supports
743 @code{fchown} (@pxref{File Owner,,,libc,The GNU C Library Reference
744 Manual}), a port or integer file descriptor which is open on the file.
745 The return value is unspecified.
747 If @var{object} is a symbolic link, either the
748 ownership of the link or the ownership of the referenced file will be
749 changed depending on the operating system (lchown is
750 unsupported at present). If @var{owner} or @var{group} is specified
751 as @code{-1}, then that ID is not changed.
755 @deffn {Scheme Procedure} chmod object mode
756 @deffnx {C Function} scm_chmod (object, mode)
757 Changes the permissions of the file referred to by @var{obj}.
758 @var{obj} can be a string containing a file name or a port or integer file
759 descriptor which is open on a file (in which case @code{fchmod} is used
760 as the underlying system call).
762 the new permissions as a decimal number, e.g., @code{(chmod "foo" #o755)}.
763 The return value is unspecified.
766 @deffn {Scheme Procedure} utime pathname [actime [modtime]]
767 @deffnx {C Function} scm_utime (pathname, actime, modtime)
769 @code{utime} sets the access and modification times for the
770 file named by @var{path}. If @var{actime} or @var{modtime} is
771 not supplied, then the current time is used. @var{actime} and
772 @var{modtime} must be integer time values as returned by the
773 @code{current-time} procedure.
775 (utime "foo" (- (current-time) 3600))
777 will set the access time to one hour in the past and the
778 modification time to the current time.
782 @deffn {Scheme Procedure} delete-file str
783 @deffnx {C Function} scm_delete_file (str)
784 Deletes (or ``unlinks'') the file whose path is specified by
788 @deffn {Scheme Procedure} copy-file oldfile newfile
789 @deffnx {C Function} scm_copy_file (oldfile, newfile)
790 Copy the file specified by @var{oldfile} to @var{newfile}.
791 The return value is unspecified.
795 @deffn {Scheme Procedure} rename-file oldname newname
796 @deffnx {C Function} scm_rename (oldname, newname)
797 Renames the file specified by @var{oldname} to @var{newname}.
798 The return value is unspecified.
801 @deffn {Scheme Procedure} link oldpath newpath
802 @deffnx {C Function} scm_link (oldpath, newpath)
803 Creates a new name @var{newpath} in the file system for the
804 file named by @var{oldpath}. If @var{oldpath} is a symbolic
805 link, the link may or may not be followed depending on the
809 @deffn {Scheme Procedure} symlink oldpath newpath
810 @deffnx {C Function} scm_symlink (oldpath, newpath)
811 Create a symbolic link named @var{newpath} with the value (i.e., pointing to)
812 @var{oldpath}. The return value is unspecified.
815 @deffn {Scheme Procedure} mkdir path [mode]
816 @deffnx {C Function} scm_mkdir (path, mode)
817 Create a new directory named by @var{path}. If @var{mode} is omitted
818 then the permissions of the directory file are set using the current
819 umask (@pxref{Processes}). Otherwise they are set to the decimal
820 value specified with @var{mode}. The return value is unspecified.
823 @deffn {Scheme Procedure} rmdir path
824 @deffnx {C Function} scm_rmdir (path)
825 Remove the existing directory named by @var{path}. The directory must
826 be empty for this to succeed. The return value is unspecified.
829 @deffn {Scheme Procedure} opendir dirname
830 @deffnx {C Function} scm_opendir (dirname)
831 @cindex directory contents
832 Open the directory specified by @var{dirname} and return a directory
836 @deffn {Scheme Procedure} directory-stream? object
837 @deffnx {C Function} scm_directory_stream_p (object)
838 Return a boolean indicating whether @var{object} is a directory
839 stream as returned by @code{opendir}.
842 @deffn {Scheme Procedure} readdir stream
843 @deffnx {C Function} scm_readdir (stream)
844 Return (as a string) the next directory entry from the directory stream
845 @var{stream}. If there is no remaining entry to be read then the
846 end of file object is returned.
849 @deffn {Scheme Procedure} rewinddir stream
850 @deffnx {C Function} scm_rewinddir (stream)
851 Reset the directory port @var{stream} so that the next call to
852 @code{readdir} will return the first directory entry.
855 @deffn {Scheme Procedure} closedir stream
856 @deffnx {C Function} scm_closedir (stream)
857 Close the directory stream @var{stream}.
858 The return value is unspecified.
861 Here is an example showing how to display all the entries in a
865 (define dir (opendir "/usr/lib"))
866 (do ((entry (readdir dir) (readdir dir)))
867 ((eof-object? entry))
868 (display entry)(newline))
872 @deffn {Scheme Procedure} sync
873 @deffnx {C Function} scm_sync ()
874 Flush the operating system disk buffers.
875 The return value is unspecified.
878 @deffn {Scheme Procedure} mknod path type perms dev
879 @deffnx {C Function} scm_mknod (path, type, perms, dev)
881 Creates a new special file, such as a file corresponding to a device.
882 @var{path} specifies the name of the file. @var{type} should be one
883 of the following symbols: @samp{regular}, @samp{directory},
884 @samp{symlink}, @samp{block-special}, @samp{char-special},
885 @samp{fifo}, or @samp{socket}. @var{perms} (an integer) specifies the
886 file permissions. @var{dev} (an integer) specifies which device the
887 special file refers to. Its exact interpretation depends on the kind
888 of special file being created.
892 (mknod "/dev/fd0" 'block-special #o660 (+ (* 2 256) 2))
895 The return value is unspecified.
898 @deffn {Scheme Procedure} tmpnam
899 @deffnx {C Function} scm_tmpnam ()
900 @cindex temporary file
901 Return an auto-generated name of a temporary file, a file which
902 doesn't already exist. The name includes a path, it's usually in
903 @file{/tmp} but that's system dependent.
905 Care must be taken when using @code{tmpnam}. In between choosing the
906 name and creating the file another program might use that name, or an
907 attacker might even make it a symlink pointing at something important
908 and causing you to overwrite that.
910 The safe way is to create the file using @code{open} with
911 @code{O_EXCL} to avoid any overwriting. A loop can try again with
912 another name if the file exists (error @code{EEXIST}).
913 @code{mkstemp!} below does that.
916 @deffn {Scheme Procedure} mkstemp! tmpl
917 @deffnx {C Function} scm_mkstemp (tmpl)
918 @cindex temporary file
919 Create a new unique file in the file system and return a new buffered
920 port open for reading and writing to the file.
922 @var{tmpl} is a string specifying where the file should be created: it
923 must end with @samp{XXXXXX} and those @samp{X}s will be changed in the
924 string to return the name of the file. (@code{port-filename} on the
925 port also gives the name.)
927 POSIX doesn't specify the permissions mode of the file, on GNU and
928 most systems it's @code{#o600}. An application can use @code{chmod}
929 to relax that if desired. For example @code{#o666} less @code{umask},
930 which is usual for ordinary file creation,
933 (let ((port (mkstemp! (string-copy "/tmp/myfile-XXXXXX"))))
934 (chmod port (logand #o666 (lognot (umask))))
939 @deffn {Scheme Procedure} dirname filename
940 @deffnx {C Function} scm_dirname (filename)
941 Return the directory name component of the file name
942 @var{filename}. If @var{filename} does not contain a directory
943 component, @code{.} is returned.
946 @deffn {Scheme Procedure} basename filename [suffix]
947 @deffnx {C Function} scm_basename (filename, suffix)
948 Return the base name of the file name @var{filename}. The
949 base name is the file name without any directory components.
950 If @var{suffix} is provided, and is equal to the end of
951 @var{basename}, it is removed also.
954 (basename "/tmp/test.xml" ".xml")
959 @deffn {Scheme Procedure} file-exists? filename
960 Return @code{#t} if the file named @var{filename} exists, @code{#f} if
965 @node User Information
966 @subsection User Information
967 @cindex user information
968 @cindex password file
971 The facilities in this section provide an interface to the user and
973 They should be used with care since they are not reentrant.
975 The following functions accept an object representing user information
976 and return a selected component:
978 @deffn {Scheme Procedure} passwd:name pw
979 The name of the userid.
981 @deffn {Scheme Procedure} passwd:passwd pw
982 The encrypted passwd.
984 @deffn {Scheme Procedure} passwd:uid pw
987 @deffn {Scheme Procedure} passwd:gid pw
990 @deffn {Scheme Procedure} passwd:gecos pw
993 @deffn {Scheme Procedure} passwd:dir pw
996 @deffn {Scheme Procedure} passwd:shell pw
1001 @deffn {Scheme Procedure} getpwuid uid
1002 Look up an integer userid in the user database.
1005 @deffn {Scheme Procedure} getpwnam name
1006 Look up a user name string in the user database.
1009 @deffn {Scheme Procedure} setpwent
1010 Initializes a stream used by @code{getpwent} to read from the user database.
1011 The next use of @code{getpwent} will return the first entry. The
1012 return value is unspecified.
1015 @deffn {Scheme Procedure} getpwent
1016 Read the next entry in the user database stream. The return is a
1017 passwd user object as above, or @code{#f} when no more entries.
1020 @deffn {Scheme Procedure} endpwent
1021 Closes the stream used by @code{getpwent}. The return value is unspecified.
1024 @deffn {Scheme Procedure} setpw [arg]
1025 @deffnx {C Function} scm_setpwent (arg)
1026 If called with a true argument, initialize or reset the password data
1027 stream. Otherwise, close the stream. The @code{setpwent} and
1028 @code{endpwent} procedures are implemented on top of this.
1031 @deffn {Scheme Procedure} getpw [user]
1032 @deffnx {C Function} scm_getpwuid (user)
1033 Look up an entry in the user database. @var{obj} can be an integer,
1034 a string, or omitted, giving the behaviour of getpwuid, getpwnam
1035 or getpwent respectively.
1038 The following functions accept an object representing group information
1039 and return a selected component:
1041 @deffn {Scheme Procedure} group:name gr
1044 @deffn {Scheme Procedure} group:passwd gr
1045 The encrypted group password.
1047 @deffn {Scheme Procedure} group:gid gr
1048 The group id number.
1050 @deffn {Scheme Procedure} group:mem gr
1051 A list of userids which have this group as a supplementary group.
1055 @deffn {Scheme Procedure} getgrgid gid
1056 Look up an integer group id in the group database.
1059 @deffn {Scheme Procedure} getgrnam name
1060 Look up a group name in the group database.
1063 @deffn {Scheme Procedure} setgrent
1064 Initializes a stream used by @code{getgrent} to read from the group database.
1065 The next use of @code{getgrent} will return the first entry.
1066 The return value is unspecified.
1069 @deffn {Scheme Procedure} getgrent
1070 Return the next entry in the group database, using the stream set by
1074 @deffn {Scheme Procedure} endgrent
1075 Closes the stream used by @code{getgrent}.
1076 The return value is unspecified.
1079 @deffn {Scheme Procedure} setgr [arg]
1080 @deffnx {C Function} scm_setgrent (arg)
1081 If called with a true argument, initialize or reset the group data
1082 stream. Otherwise, close the stream. The @code{setgrent} and
1083 @code{endgrent} procedures are implemented on top of this.
1086 @deffn {Scheme Procedure} getgr [name]
1087 @deffnx {C Function} scm_getgrgid (name)
1088 Look up an entry in the group database. @var{obj} can be an integer,
1089 a string, or omitted, giving the behaviour of getgrgid, getgrnam
1090 or getgrent respectively.
1093 In addition to the accessor procedures for the user database, the
1094 following shortcut procedures are also available.
1096 @deffn {Scheme Procedure} cuserid
1097 @deffnx {C Function} scm_cuserid ()
1098 Return a string containing a user name associated with the
1099 effective user id of the process. Return @code{#f} if this
1100 information cannot be obtained.
1102 This function has been removed from the latest POSIX specification,
1103 Guile provides it only if the system has it. Using @code{(getpwuid
1104 (geteuid))} may be a better idea.
1107 @deffn {Scheme Procedure} getlogin
1108 @deffnx {C Function} scm_getlogin ()
1109 Return a string containing the name of the user logged in on
1110 the controlling terminal of the process, or @code{#f} if this
1111 information cannot be obtained.
1119 @deffn {Scheme Procedure} current-time
1120 @deffnx {C Function} scm_current_time ()
1121 Return the number of seconds since 1970-01-01 00:00:00 @acronym{UTC},
1122 excluding leap seconds.
1125 @deffn {Scheme Procedure} gettimeofday
1126 @deffnx {C Function} scm_gettimeofday ()
1127 Return a pair containing the number of seconds and microseconds
1128 since 1970-01-01 00:00:00 @acronym{UTC}, excluding leap seconds. Note:
1129 whether true microsecond resolution is available depends on the
1133 The following procedures either accept an object representing a broken down
1134 time and return a selected component, or accept an object representing
1135 a broken down time and a value and set the component to the value.
1136 The numbers in parentheses give the usual range.
1138 @deffn {Scheme Procedure} tm:sec tm
1139 @deffnx {Scheme Procedure} set-tm:sec tm val
1142 @deffn {Scheme Procedure} tm:min tm
1143 @deffnx {Scheme Procedure} set-tm:min tm val
1146 @deffn {Scheme Procedure} tm:hour tm
1147 @deffnx {Scheme Procedure} set-tm:hour tm val
1150 @deffn {Scheme Procedure} tm:mday tm
1151 @deffnx {Scheme Procedure} set-tm:mday tm val
1152 Day of the month (1-31).
1154 @deffn {Scheme Procedure} tm:mon tm
1155 @deffnx {Scheme Procedure} set-tm:mon tm val
1158 @deffn {Scheme Procedure} tm:year tm
1159 @deffnx {Scheme Procedure} set-tm:year tm val
1160 Year (70-), the year minus 1900.
1162 @deffn {Scheme Procedure} tm:wday tm
1163 @deffnx {Scheme Procedure} set-tm:wday tm val
1164 Day of the week (0-6) with Sunday represented as 0.
1166 @deffn {Scheme Procedure} tm:yday tm
1167 @deffnx {Scheme Procedure} set-tm:yday tm val
1168 Day of the year (0-364, 365 in leap years).
1170 @deffn {Scheme Procedure} tm:isdst tm
1171 @deffnx {Scheme Procedure} set-tm:isdst tm val
1172 Daylight saving indicator (0 for ``no'', greater than 0 for ``yes'', less than
1175 @deffn {Scheme Procedure} tm:gmtoff tm
1176 @deffnx {Scheme Procedure} set-tm:gmtoff tm val
1177 Time zone offset in seconds west of @acronym{UTC} (-46800 to 43200).
1178 For example on East coast USA (zone @samp{EST+5}) this would be 18000
1179 (ie.@: @m{5\times60\times60,5*60*60}) in winter, or 14400
1180 (ie.@: @m{4\times60\times60,4*60*60}) during daylight savings.
1182 Note @code{tm:gmtoff} is not the same as @code{tm_gmtoff} in the C
1183 @code{tm} structure. @code{tm_gmtoff} is seconds east and hence the
1184 negative of the value here.
1186 @deffn {Scheme Procedure} tm:zone tm
1187 @deffnx {Scheme Procedure} set-tm:zone tm val
1188 Time zone label (a string), not necessarily unique.
1192 @deffn {Scheme Procedure} localtime time [zone]
1193 @deffnx {C Function} scm_localtime (time, zone)
1195 Return an object representing the broken down components of
1196 @var{time}, an integer like the one returned by
1197 @code{current-time}. The time zone for the calculation is
1198 optionally specified by @var{zone} (a string), otherwise the
1199 @env{TZ} environment variable or the system default is used.
1202 @deffn {Scheme Procedure} gmtime time
1203 @deffnx {C Function} scm_gmtime (time)
1204 Return an object representing the broken down components of
1205 @var{time}, an integer like the one returned by
1206 @code{current-time}. The values are calculated for @acronym{UTC}.
1209 @deffn {Scheme Procedure} mktime sbd-time [zone]
1210 @deffnx {C Function} scm_mktime (sbd_time, zone)
1211 For a broken down time object @var{sbd-time}, return a pair the
1212 @code{car} of which is an integer time like @code{current-time}, and
1213 the @code{cdr} of which is a new broken down time with normalized
1216 @var{zone} is a timezone string, or the default is the @env{TZ}
1217 environment variable or the system default (@pxref{TZ Variable,,
1218 Specifying the Time Zone with @env{TZ}, libc, GNU C Library Reference
1219 Manual}). @var{sbd-time} is taken to be in that @var{zone}.
1221 The following fields of @var{sbd-time} are used: @code{tm:year},
1222 @code{tm:mon}, @code{tm:mday}, @code{tm:hour}, @code{tm:min},
1223 @code{tm:sec}, @code{tm:isdst}. The values can be outside their usual
1224 ranges. For example @code{tm:hour} normally goes up to 23, but a
1225 value say 33 would mean 9 the following day.
1227 @code{tm:isdst} in @var{sbd-time} says whether the time given is with
1228 daylight savings or not. This is ignored if @var{zone} doesn't have
1229 any daylight savings adjustment amount.
1231 The broken down time in the return normalizes the values of
1232 @var{sbd-time} by bringing them into their usual ranges, and using the
1233 actual daylight savings rule for that time in @var{zone} (which may
1234 differ from what @var{sbd-time} had). The easiest way to think of
1235 this is that @var{sbd-time} plus @var{zone} converts to the integer
1236 UTC time, then a @code{localtime} is applied to get the normal
1237 presentation of that time, in @var{zone}.
1240 @deffn {Scheme Procedure} tzset
1241 @deffnx {C Function} scm_tzset ()
1242 Initialize the timezone from the @env{TZ} environment variable
1243 or the system default. It's not usually necessary to call this procedure
1244 since it's done automatically by other procedures that depend on the
1248 @deffn {Scheme Procedure} strftime format tm
1249 @deffnx {C Function} scm_strftime (format, tm)
1250 @cindex time formatting
1251 Return a string which is broken-down time structure @var{tm} formatted
1252 according to the given @var{format} string.
1254 @var{format} contains field specifications introduced by a @samp{%}
1255 character. See @ref{Formatting Calendar Time,,, libc, The GNU C
1256 Library Reference Manual}, or @samp{man 3 strftime}, for the available
1260 (strftime "%c" (localtime (current-time)))
1261 @result{} "Mon Mar 11 20:17:43 2002"
1264 If @code{setlocale} has been called (@pxref{Locales}), month and day
1265 names are from the current locale and in the locale character set.
1267 Note that @samp{%Z} might print the @code{tm:zone} in @var{tm} or it
1268 might print just the current zone (@code{tzset} above). A GNU system
1269 prints @code{tm:zone}, a strict C99 system like NetBSD prints the
1270 current zone. Perhaps in the future Guile will try to get
1271 @code{tm:zone} used always.
1273 @c The issue in the above is not just whether tm_zone exists in
1274 @c struct tm, but whether libc feels it should read it. Being a
1275 @c non-C99 field, a strict C99 program won't know to set it, quite
1276 @c likely leaving garbage there. NetBSD, which has the field,
1277 @c therefore takes the view that it mustn't read it. See the PR
1280 @c http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=21722
1282 @c Uniformly making tm:zone used on all systems (all those which have
1283 @c %Z at all of course) might be nice (either mung TZ and tzset, or
1284 @c mung tzname[]). On the other hand it would make us do more than
1285 @c C99 says, and we really don't want to get intimate with the gory
1286 @c details of libc time funcs, no more than can be helped.
1290 @deffn {Scheme Procedure} strptime format string
1291 @deffnx {C Function} scm_strptime (format, string)
1292 @cindex time parsing
1293 Performs the reverse action to @code{strftime}, parsing
1294 @var{string} according to the specification supplied in
1295 @var{template}. The interpretation of month and day names is
1296 dependent on the current locale. The value returned is a pair.
1297 The @acronym{CAR} has an object with time components
1298 in the form returned by @code{localtime} or @code{gmtime},
1299 but the time zone components
1300 are not usefully set.
1301 The @acronym{CDR} reports the number of characters from @var{string}
1302 which were used for the conversion.
1305 @defvar internal-time-units-per-second
1306 The value of this variable is the number of time units per second
1307 reported by the following procedures.
1310 @deffn {Scheme Procedure} times
1311 @deffnx {C Function} scm_times ()
1312 Return an object with information about real and processor
1313 time. The following procedures accept such an object as an
1314 argument and return a selected component:
1316 @deffn {Scheme Procedure} tms:clock tms
1317 The current real time, expressed as time units relative to an
1320 @deffn {Scheme Procedure} tms:utime tms
1321 The CPU time units used by the calling process.
1323 @deffn {Scheme Procedure} tms:stime tms
1324 The CPU time units used by the system on behalf of the calling
1327 @deffn {Scheme Procedure} tms:cutime tms
1328 The CPU time units used by terminated child processes of the
1329 calling process, whose status has been collected (e.g., using
1332 @deffn {Scheme Procedure} tms:cstime tms
1333 Similarly, the CPU times units used by the system on behalf of
1334 terminated child processes.
1338 @deffn {Scheme Procedure} get-internal-real-time
1339 @deffnx {C Function} scm_get_internal_real_time ()
1340 Return the number of time units since the interpreter was
1344 @deffn {Scheme Procedure} get-internal-run-time
1345 @deffnx {C Function} scm_get_internal_run_time ()
1346 Return the number of time units of processor time used by the
1347 interpreter. Both @emph{system} and @emph{user} time are
1348 included but subprocesses are not.
1351 @node Runtime Environment
1352 @subsection Runtime Environment
1354 @deffn {Scheme Procedure} program-arguments
1355 @deffnx {Scheme Procedure} command-line
1356 @deffnx {Scheme Procedure} set-program-arguments
1357 @deffnx {C Function} scm_program_arguments ()
1358 @deffnx {C Function} scm_set_program_arguments_scm (lst)
1359 @cindex command line
1360 @cindex program arguments
1361 Get the command line arguments passed to Guile, or set new arguments.
1363 The arguments are a list of strings, the first of which is the invoked
1364 program name. This is just @nicode{"guile"} (or the executable path)
1365 when run interactively, or it's the script name when running a script
1366 with @option{-s} (@pxref{Invoking Guile}).
1369 guile -L /my/extra/dir -s foo.scm abc def
1371 (program-arguments) @result{} ("foo.scm" "abc" "def")
1374 @code{set-program-arguments} allows a library module or similar to
1375 modify the arguments, for example to strip options it recognises,
1376 leaving the rest for the mainline.
1378 The argument list is held in a fluid, which means it's separate for
1379 each thread. Neither the list nor the strings within it are copied at
1380 any point and normally should not be mutated.
1382 The two names @code{program-arguments} and @code{command-line} are an
1383 historical accident, they both do exactly the same thing. The name
1384 @code{scm_set_program_arguments_scm} has an extra @code{_scm} on the
1385 end to avoid clashing with the C function below.
1388 @deftypefn {C Function} void scm_set_program_arguments (int argc, char **argv, char *first)
1389 @cindex command line
1390 @cindex program arguments
1391 Set the list of command line arguments for @code{program-arguments}
1392 and @code{command-line} above.
1394 @var{argv} is an array of null-terminated strings, as in a C
1395 @code{main} function. @var{argc} is the number of strings in
1396 @var{argv}, or if it's negative then a @code{NULL} in @var{argv} marks
1399 @var{first} is an extra string put at the start of the arguments, or
1400 @code{NULL} for no such extra. This is a convenient way to pass the
1401 program name after advancing @var{argv} to strip option arguments.
1406 char *progname = argv[0];
1407 for (argv++; argv[0] != NULL && argv[0][0] == '-'; argv++)
1409 /* munch option ... */
1411 /* remaining args for scheme level use */
1412 scm_set_program_arguments (-1, argv, progname);
1416 This sort of thing is often done at startup under
1417 @code{scm_boot_guile} with options handled at the C level removed.
1418 The given strings are all copied, so the C data is not accessed again
1419 once @code{scm_set_program_arguments} returns.
1422 @deffn {Scheme Procedure} getenv nam
1423 @deffnx {C Function} scm_getenv (nam)
1425 Looks up the string @var{name} in the current environment. The return
1426 value is @code{#f} unless a string of the form @code{NAME=VALUE} is
1427 found, in which case the string @code{VALUE} is returned.
1430 @deffn {Scheme Procedure} setenv name value
1431 Modifies the environment of the current process, which is
1432 also the default environment inherited by child processes.
1434 If @var{value} is @code{#f}, then @var{name} is removed from the
1435 environment. Otherwise, the string @var{name}=@var{value} is added
1436 to the environment, replacing any existing string with name matching
1439 The return value is unspecified.
1442 @deffn {Scheme Procedure} unsetenv name
1443 Remove variable @var{name} from the environment. The
1444 name can not contain a @samp{=} character.
1447 @deffn {Scheme Procedure} environ [env]
1448 @deffnx {C Function} scm_environ (env)
1449 If @var{env} is omitted, return the current environment (in the
1450 Unix sense) as a list of strings. Otherwise set the current
1451 environment, which is also the default environment for child
1452 processes, to the supplied list of strings. Each member of
1453 @var{env} should be of the form @var{NAME}=@var{VALUE} and values of
1454 @var{NAME} should not be duplicated. If @var{env} is supplied
1455 then the return value is unspecified.
1458 @deffn {Scheme Procedure} putenv str
1459 @deffnx {C Function} scm_putenv (str)
1460 Modifies the environment of the current process, which is
1461 also the default environment inherited by child processes.
1463 If @var{string} is of the form @code{NAME=VALUE} then it will be written
1464 directly into the environment, replacing any existing environment string
1466 name matching @code{NAME}. If @var{string} does not contain an equal
1467 sign, then any existing string with name matching @var{string} will
1470 The return value is unspecified.
1475 @subsection Processes
1477 @cindex child processes
1480 @deffn {Scheme Procedure} chdir str
1481 @deffnx {C Function} scm_chdir (str)
1482 @cindex current directory
1483 Change the current working directory to @var{path}.
1484 The return value is unspecified.
1488 @deffn {Scheme Procedure} getcwd
1489 @deffnx {C Function} scm_getcwd ()
1490 Return the name of the current working directory.
1493 @deffn {Scheme Procedure} umask [mode]
1494 @deffnx {C Function} scm_umask (mode)
1495 If @var{mode} is omitted, returns a decimal number representing the
1496 current file creation mask. Otherwise the file creation mask is set
1497 to @var{mode} and the previous value is returned. @xref{Setting
1498 Permissions,,Assigning File Permissions,libc,The GNU C Library
1499 Reference Manual}, for more on how to use umasks.
1501 E.g., @code{(umask #o022)} sets the mask to octal 22/decimal 18.
1504 @deffn {Scheme Procedure} chroot path
1505 @deffnx {C Function} scm_chroot (path)
1506 Change the root directory to that specified in @var{path}.
1507 This directory will be used for path names beginning with
1508 @file{/}. The root directory is inherited by all children
1509 of the current process. Only the superuser may change the
1513 @deffn {Scheme Procedure} getpid
1514 @deffnx {C Function} scm_getpid ()
1515 Return an integer representing the current process ID.
1518 @deffn {Scheme Procedure} getgroups
1519 @deffnx {C Function} scm_getgroups ()
1520 Return a vector of integers representing the current
1521 supplementary group IDs.
1524 @deffn {Scheme Procedure} getppid
1525 @deffnx {C Function} scm_getppid ()
1526 Return an integer representing the process ID of the parent
1530 @deffn {Scheme Procedure} getuid
1531 @deffnx {C Function} scm_getuid ()
1532 Return an integer representing the current real user ID.
1535 @deffn {Scheme Procedure} getgid
1536 @deffnx {C Function} scm_getgid ()
1537 Return an integer representing the current real group ID.
1540 @deffn {Scheme Procedure} geteuid
1541 @deffnx {C Function} scm_geteuid ()
1542 Return an integer representing the current effective user ID.
1543 If the system does not support effective IDs, then the real ID
1544 is returned. @code{(provided? 'EIDs)} reports whether the
1545 system supports effective IDs.
1548 @deffn {Scheme Procedure} getegid
1549 @deffnx {C Function} scm_getegid ()
1550 Return an integer representing the current effective group ID.
1551 If the system does not support effective IDs, then the real ID
1552 is returned. @code{(provided? 'EIDs)} reports whether the
1553 system supports effective IDs.
1556 @deffn {Scheme Procedure} setgroups vec
1557 @deffnx {C Function} scm_setgroups (vec)
1558 Set the current set of supplementary group IDs to the integers in the
1559 given vector @var{vec}. The return value is unspecified.
1561 Generally only the superuser can set the process group IDs
1562 (@pxref{Setting Groups, Setting the Group IDs,, libc, The GNU C
1563 Library Reference Manual}).
1566 @deffn {Scheme Procedure} setuid id
1567 @deffnx {C Function} scm_setuid (id)
1568 Sets both the real and effective user IDs to the integer @var{id}, provided
1569 the process has appropriate privileges.
1570 The return value is unspecified.
1573 @deffn {Scheme Procedure} setgid id
1574 @deffnx {C Function} scm_setgid (id)
1575 Sets both the real and effective group IDs to the integer @var{id}, provided
1576 the process has appropriate privileges.
1577 The return value is unspecified.
1580 @deffn {Scheme Procedure} seteuid id
1581 @deffnx {C Function} scm_seteuid (id)
1582 Sets the effective user ID to the integer @var{id}, provided the process
1583 has appropriate privileges. If effective IDs are not supported, the
1584 real ID is set instead---@code{(provided? 'EIDs)} reports whether the
1585 system supports effective IDs.
1586 The return value is unspecified.
1589 @deffn {Scheme Procedure} setegid id
1590 @deffnx {C Function} scm_setegid (id)
1591 Sets the effective group ID to the integer @var{id}, provided the process
1592 has appropriate privileges. If effective IDs are not supported, the
1593 real ID is set instead---@code{(provided? 'EIDs)} reports whether the
1594 system supports effective IDs.
1595 The return value is unspecified.
1598 @deffn {Scheme Procedure} getpgrp
1599 @deffnx {C Function} scm_getpgrp ()
1600 Return an integer representing the current process group ID.
1601 This is the @acronym{POSIX} definition, not @acronym{BSD}.
1604 @deffn {Scheme Procedure} setpgid pid pgid
1605 @deffnx {C Function} scm_setpgid (pid, pgid)
1606 Move the process @var{pid} into the process group @var{pgid}. @var{pid} or
1607 @var{pgid} must be integers: they can be zero to indicate the ID of the
1609 Fails on systems that do not support job control.
1610 The return value is unspecified.
1613 @deffn {Scheme Procedure} setsid
1614 @deffnx {C Function} scm_setsid ()
1615 Creates a new session. The current process becomes the session leader
1616 and is put in a new process group. The process will be detached
1617 from its controlling terminal if it has one.
1618 The return value is an integer representing the new process group ID.
1621 @deffn {Scheme Procedure} waitpid pid [options]
1622 @deffnx {C Function} scm_waitpid (pid, options)
1623 This procedure collects status information from a child process which
1624 has terminated or (optionally) stopped. Normally it will
1625 suspend the calling process until this can be done. If more than one
1626 child process is eligible then one will be chosen by the operating system.
1628 The value of @var{pid} determines the behaviour:
1631 @item @var{pid} greater than 0
1632 Request status information from the specified child process.
1633 @item @var{pid} equal to -1 or @code{WAIT_ANY}
1635 Request status information for any child process.
1636 @item @var{pid} equal to 0 or @code{WAIT_MYPGRP}
1638 Request status information for any child process in the current process
1640 @item @var{pid} less than -1
1641 Request status information for any child process whose process group ID
1642 is @minus{}@var{pid}.
1645 The @var{options} argument, if supplied, should be the bitwise OR of the
1646 values of zero or more of the following variables:
1649 Return immediately even if there are no child processes to be collected.
1653 Report status information for stopped processes as well as terminated
1657 The return value is a pair containing:
1661 The process ID of the child process, or 0 if @code{WNOHANG} was
1662 specified and no process was collected.
1664 The integer status value.
1669 functions can be used to decode the process status code returned
1672 @deffn {Scheme Procedure} status:exit-val status
1673 @deffnx {C Function} scm_status_exit_val (status)
1674 Return the exit status value, as would be set if a process
1675 ended normally through a call to @code{exit} or @code{_exit},
1676 if any, otherwise @code{#f}.
1679 @deffn {Scheme Procedure} status:term-sig status
1680 @deffnx {C Function} scm_status_term_sig (status)
1681 Return the signal number which terminated the process, if any,
1682 otherwise @code{#f}.
1685 @deffn {Scheme Procedure} status:stop-sig status
1686 @deffnx {C Function} scm_status_stop_sig (status)
1687 Return the signal number which stopped the process, if any,
1688 otherwise @code{#f}.
1691 @deffn {Scheme Procedure} system [cmd]
1692 @deffnx {C Function} scm_system (cmd)
1693 Execute @var{cmd} using the operating system's ``command
1694 processor''. Under Unix this is usually the default shell
1695 @code{sh}. The value returned is @var{cmd}'s exit status as
1696 returned by @code{waitpid}, which can be interpreted using the
1699 If @code{system} is called without arguments, return a boolean
1700 indicating whether the command processor is available.
1703 @deffn {Scheme Procedure} system* . args
1704 @deffnx {C Function} scm_system_star (args)
1705 Execute the command indicated by @var{args}. The first element must
1706 be a string indicating the command to be executed, and the remaining
1707 items must be strings representing each of the arguments to that
1710 This function returns the exit status of the command as provided by
1711 @code{waitpid}. This value can be handled with @code{status:exit-val}
1712 and the related functions.
1714 @code{system*} is similar to @code{system}, but accepts only one
1715 string per-argument, and performs no shell interpretation. The
1716 command is executed using fork and execlp. Accordingly this function
1717 may be safer than @code{system} in situations where shell
1718 interpretation is not required.
1720 Example: (system* "echo" "foo" "bar")
1723 @deffn {Scheme Procedure} primitive-exit [status]
1724 @deffnx {Scheme Procedure} primitive-_exit [status]
1725 @deffnx {C Function} scm_primitive_exit (status)
1726 @deffnx {C Function} scm_primitive__exit (status)
1727 Terminate the current process without unwinding the Scheme stack. The
1728 exit status is @var{status} if supplied, otherwise zero.
1730 @code{primitive-exit} uses the C @code{exit} function and hence runs
1731 usual C level cleanups (flush output streams, call @code{atexit}
1732 functions, etc, see @ref{Normal Termination,,, libc, The GNU C Library
1733 Reference Manual})).
1735 @code{primitive-_exit} is the @code{_exit} system call
1736 (@pxref{Termination Internals,,, libc, The GNU C Library Reference
1737 Manual}). This terminates the program immediately, with neither
1738 Scheme-level nor C-level cleanups.
1740 The typical use for @code{primitive-_exit} is from a child process
1741 created with @code{primitive-fork}. For example in a Gdk program the
1742 child process inherits the X server connection and a C-level
1743 @code{atexit} cleanup which will close that connection. But closing
1744 in the child would upset the protocol in the parent, so
1745 @code{primitive-_exit} should be used to exit without that.
1748 @deffn {Scheme Procedure} execl filename . args
1749 @deffnx {C Function} scm_execl (filename, args)
1750 Executes the file named by @var{path} as a new process image.
1751 The remaining arguments are supplied to the process; from a C program
1752 they are accessible as the @code{argv} argument to @code{main}.
1753 Conventionally the first @var{arg} is the same as @var{path}.
1754 All arguments must be strings.
1756 If @var{arg} is missing, @var{path} is executed with a null
1757 argument list, which may have system-dependent side-effects.
1759 This procedure is currently implemented using the @code{execv} system
1760 call, but we call it @code{execl} because of its Scheme calling interface.
1763 @deffn {Scheme Procedure} execlp filename . args
1764 @deffnx {C Function} scm_execlp (filename, args)
1765 Similar to @code{execl}, however if
1766 @var{filename} does not contain a slash
1767 then the file to execute will be located by searching the
1768 directories listed in the @code{PATH} environment variable.
1770 This procedure is currently implemented using the @code{execvp} system
1771 call, but we call it @code{execlp} because of its Scheme calling interface.
1774 @deffn {Scheme Procedure} execle filename env . args
1775 @deffnx {C Function} scm_execle (filename, env, args)
1776 Similar to @code{execl}, but the environment of the new process is
1777 specified by @var{env}, which must be a list of strings as returned by the
1778 @code{environ} procedure.
1780 This procedure is currently implemented using the @code{execve} system
1781 call, but we call it @code{execle} because of its Scheme calling interface.
1784 @deffn {Scheme Procedure} primitive-fork
1785 @deffnx {C Function} scm_fork ()
1786 Creates a new ``child'' process by duplicating the current ``parent'' process.
1787 In the child the return value is 0. In the parent the return value is
1788 the integer process ID of the child.
1790 This procedure has been renamed from @code{fork} to avoid a naming conflict
1794 @deffn {Scheme Procedure} nice incr
1795 @deffnx {C Function} scm_nice (incr)
1796 @cindex process priority
1797 Increment the priority of the current process by @var{incr}. A higher
1798 priority value means that the process runs less often.
1799 The return value is unspecified.
1802 @deffn {Scheme Procedure} setpriority which who prio
1803 @deffnx {C Function} scm_setpriority (which, who, prio)
1804 @vindex PRIO_PROCESS
1807 Set the scheduling priority of the process, process group
1808 or user, as indicated by @var{which} and @var{who}. @var{which}
1809 is one of the variables @code{PRIO_PROCESS}, @code{PRIO_PGRP}
1810 or @code{PRIO_USER}, and @var{who} is interpreted relative to
1811 @var{which} (a process identifier for @code{PRIO_PROCESS},
1812 process group identifier for @code{PRIO_PGRP}, and a user
1813 identifier for @code{PRIO_USER}. A zero value of @var{who}
1814 denotes the current process, process group, or user.
1815 @var{prio} is a value in the range [@minus{}20,20]. The default
1816 priority is 0; lower priorities (in numerical terms) cause more
1817 favorable scheduling. Sets the priority of all of the specified
1818 processes. Only the super-user may lower priorities. The return
1819 value is not specified.
1822 @deffn {Scheme Procedure} getpriority which who
1823 @deffnx {C Function} scm_getpriority (which, who)
1824 @vindex PRIO_PROCESS
1827 Return the scheduling priority of the process, process group
1828 or user, as indicated by @var{which} and @var{who}. @var{which}
1829 is one of the variables @code{PRIO_PROCESS}, @code{PRIO_PGRP}
1830 or @code{PRIO_USER}, and @var{who} should be interpreted depending on
1831 @var{which} (a process identifier for @code{PRIO_PROCESS},
1832 process group identifier for @code{PRIO_PGRP}, and a user
1833 identifier for @code{PRIO_USER}). A zero value of @var{who}
1834 denotes the current process, process group, or user. Return
1835 the highest priority (lowest numerical value) of any of the
1836 specified processes.
1844 The following procedures raise, handle and wait for signals.
1846 Scheme code signal handlers are run via a system async (@pxref{System
1847 asyncs}), so they're called in the handler's thread at the next safe
1848 opportunity. Generally this is after any currently executing
1849 primitive procedure finishes (which could be a long time for
1850 primitives that wait for an external event).
1852 @deffn {Scheme Procedure} kill pid sig
1853 @deffnx {C Function} scm_kill (pid, sig)
1854 Sends a signal to the specified process or group of processes.
1856 @var{pid} specifies the processes to which the signal is sent:
1859 @item @var{pid} greater than 0
1860 The process whose identifier is @var{pid}.
1861 @item @var{pid} equal to 0
1862 All processes in the current process group.
1863 @item @var{pid} less than -1
1864 The process group whose identifier is -@var{pid}
1865 @item @var{pid} equal to -1
1866 If the process is privileged, all processes except for some special
1867 system processes. Otherwise, all processes with the current effective
1871 @var{sig} should be specified using a variable corresponding to
1872 the Unix symbolic name, e.g.,
1882 A full list of signals on the GNU system may be found in @ref{Standard
1883 Signals,,,libc,The GNU C Library Reference Manual}.
1886 @deffn {Scheme Procedure} raise sig
1887 @deffnx {C Function} scm_raise (sig)
1888 Sends a specified signal @var{sig} to the current process, where
1889 @var{sig} is as described for the @code{kill} procedure.
1892 @deffn {Scheme Procedure} sigaction signum [handler [flags [thread]]]
1893 @deffnx {C Function} scm_sigaction (signum, handler, flags)
1894 @deffnx {C Function} scm_sigaction_for_thread (signum, handler, flags, thread)
1895 Install or report the signal handler for a specified signal.
1897 @var{signum} is the signal number, which can be specified using the value
1898 of variables such as @code{SIGINT}.
1900 If @var{handler} is omitted, @code{sigaction} returns a pair: the
1901 @acronym{CAR} is the current signal hander, which will be either an
1902 integer with the value @code{SIG_DFL} (default action) or
1903 @code{SIG_IGN} (ignore), or the Scheme procedure which handles the
1904 signal, or @code{#f} if a non-Scheme procedure handles the signal.
1905 The @acronym{CDR} contains the current @code{sigaction} flags for the
1908 If @var{handler} is provided, it is installed as the new handler for
1909 @var{signum}. @var{handler} can be a Scheme procedure taking one
1910 argument, or the value of @code{SIG_DFL} (default action) or
1911 @code{SIG_IGN} (ignore), or @code{#f} to restore whatever signal handler
1912 was installed before @code{sigaction} was first used. When a scheme
1913 procedure has been specified, that procedure will run in the given
1914 @var{thread}. When no thread has been given, the thread that made this
1915 call to @code{sigaction} is used.
1917 @var{flags} is a @code{logior} (@pxref{Bitwise Operations}) of the
1918 following (where provided by the system), or @code{0} for none.
1920 @defvar SA_NOCLDSTOP
1921 By default, @code{SIGCHLD} is signalled when a child process stops
1922 (ie.@: receives @code{SIGSTOP}), and when a child process terminates.
1923 With the @code{SA_NOCLDSTOP} flag, @code{SIGCHLD} is only signalled
1924 for termination, not stopping.
1926 @code{SA_NOCLDSTOP} has no effect on signals other than
1931 If a signal occurs while in a system call, deliver the signal then
1932 restart the system call (as opposed to returning an @code{EINTR} error
1935 Guile always enables this flag where available, no matter what
1936 @var{flags} are specified. This avoids spurious error returns in low
1940 The return value is a pair with information about the old handler as
1943 This interface does not provide access to the ``signal blocking''
1944 facility. Maybe this is not needed, since the thread support may
1945 provide solutions to the problem of consistent access to data
1949 @deffn {Scheme Procedure} restore-signals
1950 @deffnx {C Function} scm_restore_signals ()
1951 Return all signal handlers to the values they had before any call to
1952 @code{sigaction} was made. The return value is unspecified.
1955 @deffn {Scheme Procedure} alarm i
1956 @deffnx {C Function} scm_alarm (i)
1957 Set a timer to raise a @code{SIGALRM} signal after the specified
1958 number of seconds (an integer). It's advisable to install a signal
1960 @code{SIGALRM} beforehand, since the default action is to terminate
1963 The return value indicates the time remaining for the previous alarm,
1964 if any. The new value replaces the previous alarm. If there was
1965 no previous alarm, the return value is zero.
1968 @deffn {Scheme Procedure} pause
1969 @deffnx {C Function} scm_pause ()
1970 Pause the current process (thread?) until a signal arrives whose
1971 action is to either terminate the current process or invoke a
1972 handler procedure. The return value is unspecified.
1975 @deffn {Scheme Procedure} sleep secs
1976 @deffnx {Scheme Procedure} usleep usecs
1977 @deffnx {C Function} scm_sleep (secs)
1978 @deffnx {C Function} scm_usleep (usecs)
1979 Wait the given period @var{secs} seconds or @var{usecs} microseconds
1980 (both integers). If a signal arrives the wait stops and the return
1981 value is the time remaining, in seconds or microseconds respectively.
1982 If the period elapses with no signal the return is zero.
1984 On most systems the process scheduler is not microsecond accurate and
1985 the actual period slept by @code{usleep} might be rounded to a system
1986 clock tick boundary, which might be 10 milliseconds for instance.
1988 See @code{scm_std_sleep} and @code{scm_std_usleep} for equivalents at
1989 the C level (@pxref{Blocking}).
1992 @deffn {Scheme Procedure} getitimer which_timer
1993 @deffnx {Scheme Procedure} setitimer which_timer interval_seconds interval_microseconds periodic_seconds periodic_microseconds
1994 @deffnx {C Function} scm_getitimer (which_timer)
1995 @deffnx {C Function} scm_setitimer (which_timer, interval_seconds, interval_microseconds, periodic_seconds, periodic_microseconds)
1996 Get or set the periods programmed in certain system timers. These
1997 timers have a current interval value which counts down and on reaching
1998 zero raises a signal. An optional periodic value can be set to
1999 restart from there each time, for periodic operation.
2000 @var{which_timer} is one of the following values
2003 A real-time timer, counting down elapsed real time. At zero it raises
2004 @code{SIGALRM}. This is like @code{alarm} above, but with a higher
2008 @defvar ITIMER_VIRTUAL
2009 A virtual-time timer, counting down while the current process is
2010 actually using CPU. At zero it raises @code{SIGVTALRM}.
2014 A profiling timer, counting down while the process is running (like
2015 @code{ITIMER_VIRTUAL}) and also while system calls are running on the
2016 process's behalf. At zero it raises a @code{SIGPROF}.
2018 This timer is intended for profiling where a program is spending its
2019 time (by looking where it is when the timer goes off).
2022 @code{getitimer} returns the current timer value and its programmed
2023 restart value, as a list containing two pairs. Each pair is a time in
2024 seconds and microseconds: @code{((@var{interval_secs}
2025 . @var{interval_usecs}) (@var{periodic_secs}
2026 . @var{periodic_usecs}))}.
2028 @code{setitimer} sets the timer values similarly, in seconds and
2029 microseconds (which must be integers). The periodic value can be zero
2030 to have the timer run down just once. The return value is the timer's
2031 previous setting, in the same form as @code{getitimer} returns.
2034 (setitimer ITIMER_REAL
2035 5 500000 ;; first SIGALRM in 5.5 seconds time
2036 2 0) ;; then repeat every 2 seconds
2039 Although the timers are programmed in microseconds, the actual
2040 accuracy might not be that high.
2044 @node Terminals and Ptys
2045 @subsection Terminals and Ptys
2047 @deffn {Scheme Procedure} isatty? port
2048 @deffnx {C Function} scm_isatty_p (port)
2050 Return @code{#t} if @var{port} is using a serial non--file
2051 device, otherwise @code{#f}.
2054 @deffn {Scheme Procedure} ttyname port
2055 @deffnx {C Function} scm_ttyname (port)
2057 Return a string with the name of the serial terminal device
2058 underlying @var{port}.
2061 @deffn {Scheme Procedure} ctermid
2062 @deffnx {C Function} scm_ctermid ()
2064 Return a string containing the file name of the controlling
2065 terminal for the current process.
2068 @deffn {Scheme Procedure} tcgetpgrp port
2069 @deffnx {C Function} scm_tcgetpgrp (port)
2070 @cindex process group
2071 Return the process group ID of the foreground process group
2072 associated with the terminal open on the file descriptor
2073 underlying @var{port}.
2075 If there is no foreground process group, the return value is a
2076 number greater than 1 that does not match the process group ID
2077 of any existing process group. This can happen if all of the
2078 processes in the job that was formerly the foreground job have
2079 terminated, and no other job has yet been moved into the
2083 @deffn {Scheme Procedure} tcsetpgrp port pgid
2084 @deffnx {C Function} scm_tcsetpgrp (port, pgid)
2085 @cindex process group
2086 Set the foreground process group ID for the terminal used by the file
2087 descriptor underlying @var{port} to the integer @var{pgid}.
2089 must be a member of the same session as @var{pgid} and must have the same
2090 controlling terminal. The return value is unspecified.
2097 The following procedures are similar to the @code{popen} and
2098 @code{pclose} system routines. The code is in a separate ``popen''
2102 (use-modules (ice-9 popen))
2106 @deffn {Scheme Procedure} open-pipe command mode
2107 @deffnx {Scheme Procedure} open-pipe* mode prog [args...]
2108 Execute a command in a subprocess, with a pipe to it or from it, or
2109 with pipes in both directions.
2111 @code{open-pipe} runs the shell @var{command} using @samp{/bin/sh -c}.
2112 @code{open-pipe*} executes @var{prog} directly, with the optional
2113 @var{args} arguments (all strings).
2115 @var{mode} should be one of the following values. @code{OPEN_READ} is
2116 an input pipe, ie.@: to read from the subprocess. @code{OPEN_WRITE}
2117 is an output pipe, ie.@: to write to it.
2124 For an input pipe, the child's standard output is the pipe and
2125 standard input is inherited from @code{current-input-port}. For an
2126 output pipe, the child's standard input is the pipe and standard
2127 output is inherited from @code{current-output-port}. In all cases
2128 cases the child's standard error is inherited from
2129 @code{current-error-port} (@pxref{Default Ports}).
2131 If those @code{current-X-ports} are not files of some kind, and hence
2132 don't have file descriptors for the child, then @file{/dev/null} is
2135 Care should be taken with @code{OPEN_BOTH}, a deadlock will occur if
2136 both parent and child are writing, and waiting until the write
2137 completes before doing any reading. Each direction has
2138 @code{PIPE_BUF} bytes of buffering (@pxref{Ports and File
2139 Descriptors}), which will be enough for small writes, but not for say
2140 putting a big file through a filter.
2143 @deffn {Scheme Procedure} open-input-pipe command
2144 Equivalent to @code{open-pipe} with mode @code{OPEN_READ}.
2147 (let* ((port (open-input-pipe "date --utc"))
2148 (str (read-line port)))
2151 @result{} "Mon Mar 11 20:10:44 UTC 2002"
2155 @deffn {Scheme Procedure} open-output-pipe command
2156 Equivalent to @code{open-pipe} with mode @code{OPEN_WRITE}.
2159 (let ((port (open-output-pipe "lpr")))
2160 (display "Something for the line printer.\n" port)
2161 (if (not (eqv? 0 (status:exit-val (close-pipe port))))
2162 (error "Cannot print")))
2166 @deffn {Scheme Procedure} open-input-output-pipe command
2167 Equivalent to @code{open-pipe} with mode @code{OPEN_BOTH}.
2171 @deffn {Scheme Procedure} close-pipe port
2172 Close a pipe created by @code{open-pipe}, wait for the process to
2173 terminate, and return the wait status code. The status is as per
2174 @code{waitpid} and can be decoded with @code{status:exit-val} etc
2179 @code{waitpid WAIT_ANY} should not be used when pipes are open, since
2180 it can reap a pipe's child process, causing an error from a subsequent
2183 @code{close-port} (@pxref{Closing}) can close a pipe, but it doesn't
2184 reap the child process.
2186 The garbage collector will close a pipe no longer in use, and reap the
2187 child process with @code{waitpid}. If the child hasn't yet terminated
2188 the garbage collector doesn't block, but instead checks again in the
2191 Many systems have per-user and system-wide limits on the number of
2192 processes, and a system-wide limit on the number of pipes, so pipes
2193 should be closed explicitly when no longer needed, rather than letting
2194 the garbage collector pick them up at some later time.
2198 @subsection Networking
2202 * Network Address Conversion::
2203 * Network Databases::
2204 * Network Socket Address::
2205 * Network Sockets and Communication::
2206 * Internet Socket Examples::
2209 @node Network Address Conversion
2210 @subsubsection Network Address Conversion
2211 @cindex network address
2213 This section describes procedures which convert internet addresses
2214 between numeric and string formats.
2216 @subsubheading IPv4 Address Conversion
2219 An IPv4 Internet address is a 4-byte value, represented in Guile as an
2220 integer in host byte order, so that say ``0.0.0.1'' is 1, or
2221 ``1.0.0.0'' is 16777216.
2223 Some underlying C functions use network byte order for addresses,
2224 Guile converts as necessary so that at the Scheme level its host byte
2228 For a server, this can be used with @code{bind} (@pxref{Network
2229 Sockets and Communication}) to allow connections from any interface on
2233 @defvar INADDR_BROADCAST
2234 The broadcast address on the local network.
2237 @defvar INADDR_LOOPBACK
2238 The address of the local host using the loopback device, ie.@:
2242 @c INADDR_NONE is defined in the code, but serves no purpose.
2243 @c inet_addr() returns it as an error indication, but that function
2244 @c isn't provided, for the good reason that inet_aton() does the same
2245 @c job and gives an unambiguous error indication. (INADDR_NONE is a
2246 @c valid 4-byte value, in glibc it's the same as INADDR_BROADCAST.)
2248 @c @defvar INADDR_NONE
2252 @deffn {Scheme Procedure} inet-aton address
2253 @deffnx {C Function} scm_inet_aton (address)
2254 Convert an IPv4 Internet address from printable string
2255 (dotted decimal notation) to an integer. E.g.,
2258 (inet-aton "127.0.0.1") @result{} 2130706433
2262 @deffn {Scheme Procedure} inet-ntoa inetid
2263 @deffnx {C Function} scm_inet_ntoa (inetid)
2264 Convert an IPv4 Internet address to a printable
2265 (dotted decimal notation) string. E.g.,
2268 (inet-ntoa 2130706433) @result{} "127.0.0.1"
2272 @deffn {Scheme Procedure} inet-netof address
2273 @deffnx {C Function} scm_inet_netof (address)
2274 Return the network number part of the given IPv4
2275 Internet address. E.g.,
2278 (inet-netof 2130706433) @result{} 127
2282 @deffn {Scheme Procedure} inet-lnaof address
2283 @deffnx {C Function} scm_lnaof (address)
2284 Return the local-address-with-network part of the given
2285 IPv4 Internet address, using the obsolete class A/B/C system.
2289 (inet-lnaof 2130706433) @result{} 1
2293 @deffn {Scheme Procedure} inet-makeaddr net lna
2294 @deffnx {C Function} scm_inet_makeaddr (net, lna)
2295 Make an IPv4 Internet address by combining the network number
2296 @var{net} with the local-address-within-network number
2300 (inet-makeaddr 127 1) @result{} 2130706433
2304 @subsubheading IPv6 Address Conversion
2307 An IPv6 Internet address is a 16-byte value, represented in Guile as
2308 an integer in host byte order, so that say ``::1'' is 1.
2310 @deffn {Scheme Procedure} inet-ntop family address
2311 @deffnx {C Function} scm_inet_ntop (family, address)
2312 Convert a network address from an integer to a printable string.
2313 @var{family} can be @code{AF_INET} or @code{AF_INET6}. E.g.,
2316 (inet-ntop AF_INET 2130706433) @result{} "127.0.0.1"
2317 (inet-ntop AF_INET6 (- (expt 2 128) 1)) @result{}
2318 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2322 @deffn {Scheme Procedure} inet-pton family address
2323 @deffnx {C Function} scm_inet_pton (family, address)
2324 Convert a string containing a printable network address to an integer
2325 address. @var{family} can be @code{AF_INET} or @code{AF_INET6}.
2329 (inet-pton AF_INET "127.0.0.1") @result{} 2130706433
2330 (inet-pton AF_INET6 "::1") @result{} 1
2335 @node Network Databases
2336 @subsubsection Network Databases
2337 @cindex network database
2339 This section describes procedures which query various network databases.
2340 Care should be taken when using the database routines since they are not
2343 @subsubheading The Host Database
2344 @cindex @file{/etc/hosts}
2345 @cindex network database
2347 A @dfn{host object} is a structure that represents what is known about a
2348 network host, and is the usual way of representing a system's network
2349 identity inside software.
2351 The following functions accept a host object and return a selected
2354 @deffn {Scheme Procedure} hostent:name host
2355 The ``official'' hostname for @var{host}.
2357 @deffn {Scheme Procedure} hostent:aliases host
2358 A list of aliases for @var{host}.
2360 @deffn {Scheme Procedure} hostent:addrtype host
2361 The host address type, one of the @code{AF} constants, such as
2362 @code{AF_INET} or @code{AF_INET6}.
2364 @deffn {Scheme Procedure} hostent:length host
2365 The length of each address for @var{host}, in bytes.
2367 @deffn {Scheme Procedure} hostent:addr-list host
2368 The list of network addresses associated with @var{host}. For
2369 @code{AF_INET} these are integer IPv4 address (@pxref{Network Address
2373 The following procedures are used to search the host database:
2375 @deffn {Scheme Procedure} gethost [host]
2376 @deffnx {Scheme Procedure} gethostbyname hostname
2377 @deffnx {Scheme Procedure} gethostbyaddr address
2378 @deffnx {C Function} scm_gethost (host)
2379 Look up a host by name or address, returning a host object. The
2380 @code{gethost} procedure will accept either a string name or an integer
2381 address; if given no arguments, it behaves like @code{gethostent} (see
2382 below). If a name or address is supplied but the address can not be
2383 found, an error will be thrown to one of the keys:
2384 @code{host-not-found}, @code{try-again}, @code{no-recovery} or
2385 @code{no-data}, corresponding to the equivalent @code{h_error} values.
2386 Unusual conditions may result in errors thrown to the
2387 @code{system-error} or @code{misc_error} keys.
2390 (gethost "www.gnu.org")
2391 @result{} #("www.gnu.org" () 2 4 (3353880842))
2393 (gethostbyname "www.emacs.org")
2394 @result{} #("emacs.org" ("www.emacs.org") 2 4 (1073448978))
2398 The following procedures may be used to step through the host
2399 database from beginning to end.
2401 @deffn {Scheme Procedure} sethostent [stayopen]
2402 Initialize an internal stream from which host objects may be read. This
2403 procedure must be called before any calls to @code{gethostent}, and may
2404 also be called afterward to reset the host entry stream. If
2405 @var{stayopen} is supplied and is not @code{#f}, the database is not
2406 closed by subsequent @code{gethostbyname} or @code{gethostbyaddr} calls,
2407 possibly giving an efficiency gain.
2410 @deffn {Scheme Procedure} gethostent
2411 Return the next host object from the host database, or @code{#f} if
2412 there are no more hosts to be found (or an error has been encountered).
2413 This procedure may not be used before @code{sethostent} has been called.
2416 @deffn {Scheme Procedure} endhostent
2417 Close the stream used by @code{gethostent}. The return value is unspecified.
2420 @deffn {Scheme Procedure} sethost [stayopen]
2421 @deffnx {C Function} scm_sethost (stayopen)
2422 If @var{stayopen} is omitted, this is equivalent to @code{endhostent}.
2423 Otherwise it is equivalent to @code{sethostent stayopen}.
2426 @subsubheading The Network Database
2427 @cindex network database
2429 The following functions accept an object representing a network
2430 and return a selected component:
2432 @deffn {Scheme Procedure} netent:name net
2433 The ``official'' network name.
2435 @deffn {Scheme Procedure} netent:aliases net
2436 A list of aliases for the network.
2438 @deffn {Scheme Procedure} netent:addrtype net
2439 The type of the network number. Currently, this returns only
2442 @deffn {Scheme Procedure} netent:net net
2446 The following procedures are used to search the network database:
2448 @deffn {Scheme Procedure} getnet [net]
2449 @deffnx {Scheme Procedure} getnetbyname net-name
2450 @deffnx {Scheme Procedure} getnetbyaddr net-number
2451 @deffnx {C Function} scm_getnet (net)
2452 Look up a network by name or net number in the network database. The
2453 @var{net-name} argument must be a string, and the @var{net-number}
2454 argument must be an integer. @code{getnet} will accept either type of
2455 argument, behaving like @code{getnetent} (see below) if no arguments are
2459 The following procedures may be used to step through the network
2460 database from beginning to end.
2462 @deffn {Scheme Procedure} setnetent [stayopen]
2463 Initialize an internal stream from which network objects may be read. This
2464 procedure must be called before any calls to @code{getnetent}, and may
2465 also be called afterward to reset the net entry stream. If
2466 @var{stayopen} is supplied and is not @code{#f}, the database is not
2467 closed by subsequent @code{getnetbyname} or @code{getnetbyaddr} calls,
2468 possibly giving an efficiency gain.
2471 @deffn {Scheme Procedure} getnetent
2472 Return the next entry from the network database.
2475 @deffn {Scheme Procedure} endnetent
2476 Close the stream used by @code{getnetent}. The return value is unspecified.
2479 @deffn {Scheme Procedure} setnet [stayopen]
2480 @deffnx {C Function} scm_setnet (stayopen)
2481 If @var{stayopen} is omitted, this is equivalent to @code{endnetent}.
2482 Otherwise it is equivalent to @code{setnetent stayopen}.
2485 @subsubheading The Protocol Database
2486 @cindex @file{/etc/protocols}
2488 @cindex network protocols
2490 The following functions accept an object representing a protocol
2491 and return a selected component:
2493 @deffn {Scheme Procedure} protoent:name protocol
2494 The ``official'' protocol name.
2496 @deffn {Scheme Procedure} protoent:aliases protocol
2497 A list of aliases for the protocol.
2499 @deffn {Scheme Procedure} protoent:proto protocol
2500 The protocol number.
2503 The following procedures are used to search the protocol database:
2505 @deffn {Scheme Procedure} getproto [protocol]
2506 @deffnx {Scheme Procedure} getprotobyname name
2507 @deffnx {Scheme Procedure} getprotobynumber number
2508 @deffnx {C Function} scm_getproto (protocol)
2509 Look up a network protocol by name or by number. @code{getprotobyname}
2510 takes a string argument, and @code{getprotobynumber} takes an integer
2511 argument. @code{getproto} will accept either type, behaving like
2512 @code{getprotoent} (see below) if no arguments are supplied.
2515 The following procedures may be used to step through the protocol
2516 database from beginning to end.
2518 @deffn {Scheme Procedure} setprotoent [stayopen]
2519 Initialize an internal stream from which protocol objects may be read. This
2520 procedure must be called before any calls to @code{getprotoent}, and may
2521 also be called afterward to reset the protocol entry stream. If
2522 @var{stayopen} is supplied and is not @code{#f}, the database is not
2523 closed by subsequent @code{getprotobyname} or @code{getprotobynumber} calls,
2524 possibly giving an efficiency gain.
2527 @deffn {Scheme Procedure} getprotoent
2528 Return the next entry from the protocol database.
2531 @deffn {Scheme Procedure} endprotoent
2532 Close the stream used by @code{getprotoent}. The return value is unspecified.
2535 @deffn {Scheme Procedure} setproto [stayopen]
2536 @deffnx {C Function} scm_setproto (stayopen)
2537 If @var{stayopen} is omitted, this is equivalent to @code{endprotoent}.
2538 Otherwise it is equivalent to @code{setprotoent stayopen}.
2541 @subsubheading The Service Database
2542 @cindex @file{/etc/services}
2544 @cindex network services
2546 The following functions accept an object representing a service
2547 and return a selected component:
2549 @deffn {Scheme Procedure} servent:name serv
2550 The ``official'' name of the network service.
2552 @deffn {Scheme Procedure} servent:aliases serv
2553 A list of aliases for the network service.
2555 @deffn {Scheme Procedure} servent:port serv
2556 The Internet port used by the service.
2558 @deffn {Scheme Procedure} servent:proto serv
2559 The protocol used by the service. A service may be listed many times
2560 in the database under different protocol names.
2563 The following procedures are used to search the service database:
2565 @deffn {Scheme Procedure} getserv [name [protocol]]
2566 @deffnx {Scheme Procedure} getservbyname name protocol
2567 @deffnx {Scheme Procedure} getservbyport port protocol
2568 @deffnx {C Function} scm_getserv (name, protocol)
2569 Look up a network service by name or by service number, and return a
2570 network service object. The @var{protocol} argument specifies the name
2571 of the desired protocol; if the protocol found in the network service
2572 database does not match this name, a system error is signalled.
2574 The @code{getserv} procedure will take either a service name or number
2575 as its first argument; if given no arguments, it behaves like
2576 @code{getservent} (see below).
2579 (getserv "imap" "tcp")
2580 @result{} #("imap2" ("imap") 143 "tcp")
2582 (getservbyport 88 "udp")
2583 @result{} #("kerberos" ("kerberos5" "krb5") 88 "udp")
2587 The following procedures may be used to step through the service
2588 database from beginning to end.
2590 @deffn {Scheme Procedure} setservent [stayopen]
2591 Initialize an internal stream from which service objects may be read. This
2592 procedure must be called before any calls to @code{getservent}, and may
2593 also be called afterward to reset the service entry stream. If
2594 @var{stayopen} is supplied and is not @code{#f}, the database is not
2595 closed by subsequent @code{getservbyname} or @code{getservbyport} calls,
2596 possibly giving an efficiency gain.
2599 @deffn {Scheme Procedure} getservent
2600 Return the next entry from the services database.
2603 @deffn {Scheme Procedure} endservent
2604 Close the stream used by @code{getservent}. The return value is unspecified.
2607 @deffn {Scheme Procedure} setserv [stayopen]
2608 @deffnx {C Function} scm_setserv (stayopen)
2609 If @var{stayopen} is omitted, this is equivalent to @code{endservent}.
2610 Otherwise it is equivalent to @code{setservent stayopen}.
2614 @node Network Socket Address
2615 @subsubsection Network Socket Address
2616 @cindex socket address
2617 @cindex network socket address
2618 @tpindex Socket address
2620 A @dfn{socket address} object identifies a socket endpoint for
2621 communication. In the case of @code{AF_INET} for instance, the socket
2622 address object comprises the host address (or interface on the host)
2623 and a port number which specifies a particular open socket in a
2624 running client or server process. A socket address object can be
2627 @deffn {Scheme Procedure} make-socket-address AF_INET ipv4addr port
2628 @deffnx {Scheme Procedure} make-socket-address AF_INET6 ipv6addr port [flowinfo [scopeid]]
2629 @deffnx {Scheme Procedure} make-socket-address AF_UNIX path
2630 @deffnx {C Function} scm_make_socket_address family address arglist
2631 Return a new socket address object. The first argument is the address
2632 family, one of the @code{AF} constants, then the arguments vary
2633 according to the family.
2635 For @code{AF_INET} the arguments are an IPv4 network address number
2636 (@pxref{Network Address Conversion}), and a port number.
2638 For @code{AF_INET6} the arguments are an IPv6 network address number
2639 and a port number. Optional @var{flowinfo} and @var{scopeid}
2640 arguments may be given (both integers, default 0).
2642 For @code{AF_UNIX} the argument is a filename (a string).
2644 The C function @code{scm_make_socket_address} takes the @var{family}
2645 and @var{address} arguments directly, then @var{arglist} is a list of
2646 further arguments, being the port for IPv4, port and optional flowinfo
2647 and scopeid for IPv6, or the empty list @code{SCM_EOL} for Unix
2652 The following functions access the fields of a socket address object,
2654 @deffn {Scheme Procedure} sockaddr:fam sa
2655 Return the address family from socket address object @var{sa}. This
2656 is one of the @code{AF} constants (eg. @code{AF_INET}).
2659 @deffn {Scheme Procedure} sockaddr:path sa
2660 For an @code{AF_UNIX} socket address object @var{sa}, return the
2664 @deffn {Scheme Procedure} sockaddr:addr sa
2665 For an @code{AF_INET} or @code{AF_INET6} socket address object
2666 @var{sa}, return the network address number.
2669 @deffn {Scheme Procedure} sockaddr:port sa
2670 For an @code{AF_INET} or @code{AF_INET6} socket address object
2671 @var{sa}, return the port number.
2674 @deffn {Scheme Procedure} sockaddr:flowinfo sa
2675 For an @code{AF_INET6} socket address object @var{sa}, return the
2679 @deffn {Scheme Procedure} sockaddr:scopeid sa
2680 For an @code{AF_INET6} socket address object @var{sa}, return the
2684 @tpindex @code{struct sockaddr}
2685 @tpindex @code{sockaddr}
2686 The functions below convert to and from the C @code{struct sockaddr}
2687 (@pxref{Address Formats,,, libc, The GNU C Library Reference Manual}).
2688 That structure is a generic type, an application can cast to or from
2689 @code{struct sockaddr_in}, @code{struct sockaddr_in6} or @code{struct
2690 sockaddr_un} according to the address family.
2692 In a @code{struct sockaddr} taken or returned, the byte ordering in
2693 the fields follows the C conventions (@pxref{Byte Order,, Byte Order
2694 Conversion, libc, The GNU C Library Reference Manual}). This means
2695 network byte order for @code{AF_INET} host address
2696 (@code{sin_addr.s_addr}) and port number (@code{sin_port}), and
2697 @code{AF_INET6} port number (@code{sin6_port}). But at the Scheme
2698 level these values are taken or returned in host byte order, so the
2699 port is an ordinary integer, and the host address likewise is an
2700 ordinary integer (as described in @ref{Network Address Conversion}).
2702 @deftypefn {C Function} {struct sockaddr *} scm_c_make_socket_address (SCM family, SCM address, SCM args, size_t *outsize)
2703 Return a newly-@code{malloc}ed @code{struct sockaddr} created from
2704 arguments like those taken by @code{scm_make_socket_address} above.
2706 The size (in bytes) of the @code{struct sockaddr} return is stored
2707 into @code{*@var{outsize}}. An application must call @code{free} to
2708 release the returned structure when no longer required.
2711 @deftypefn {C Function} SCM scm_from_sockaddr (const struct sockaddr *address, unsigned address_size)
2712 Return a Scheme socket address object from the C @var{address}
2713 structure. @var{address_size} is the size in bytes of @var{address}.
2716 @deftypefn {C Function} {struct sockaddr *} scm_to_sockaddr (SCM address, size_t *address_size)
2717 Return a newly-@code{malloc}ed @code{struct sockaddr} from a Scheme
2718 level socket address object.
2720 The size (in bytes) of the @code{struct sockaddr} return is stored
2721 into @code{*@var{outsize}}. An application must call @code{free} to
2722 release the returned structure when no longer required.
2726 @node Network Sockets and Communication
2727 @subsubsection Network Sockets and Communication
2729 @cindex network socket
2731 Socket ports can be created using @code{socket} and @code{socketpair}.
2732 The ports are initially unbuffered, to make reading and writing to the
2733 same port more reliable. A buffer can be added to the port using
2734 @code{setvbuf}; see @ref{Ports and File Descriptors}.
2736 Most systems have limits on how many files and sockets can be open, so
2737 it's strongly recommended that socket ports be closed explicitly when
2738 no longer required (@pxref{Ports}).
2740 Some of the underlying C functions take values in network byte order,
2741 but the convention in Guile is that at the Scheme level everything is
2742 ordinary host byte order and conversions are made automatically where
2745 @deffn {Scheme Procedure} socket family style proto
2746 @deffnx {C Function} scm_socket (family, style, proto)
2747 Return a new socket port of the type specified by @var{family},
2748 @var{style} and @var{proto}. All three parameters are integers. The
2749 possible values for @var{family} are as follows, where supported by
2757 The possible values for @var{style} are as follows, again where
2758 supported by the system,
2764 @defvarx SOCK_SEQPACKET
2767 @var{proto} can be obtained from a protocol name using
2768 @code{getprotobyname} (@pxref{Network Databases}). A value of zero
2769 means the default protocol, which is usually right.
2771 A socket cannot by used for communication until it has been connected
2772 somewhere, usually with either @code{connect} or @code{accept} below.
2775 @deffn {Scheme Procedure} socketpair family style proto
2776 @deffnx {C Function} scm_socketpair (family, style, proto)
2777 Return a pair, the @code{car} and @code{cdr} of which are two unnamed
2778 socket ports connected to each other. The connection is full-duplex,
2779 so data can be transferred in either direction between the two.
2781 @var{family}, @var{style} and @var{proto} are as per @code{socket}
2782 above. But many systems only support socket pairs in the
2783 @code{PF_UNIX} family. Zero is likely to be the only meaningful value
2787 @deffn {Scheme Procedure} getsockopt sock level optname
2788 @deffnx {Scheme Procedure} setsockopt sock level optname value
2789 @deffnx {C Function} scm_getsockopt (sock, level, optname)
2790 @deffnx {C Function} scm_setsockopt (sock, level, optname, value)
2791 Get or set an option on socket port @var{sock}. @code{getsockopt}
2792 returns the current value. @code{setsockopt} sets a value and the
2793 return is unspecified.
2795 @var{level} is an integer specifying a protocol layer, either
2796 @code{SOL_SOCKET} for socket level options, or a protocol number from
2797 the @code{IPPROTO} constants or @code{getprotoent} (@pxref{Network
2802 @defvarx IPPROTO_TCP
2803 @defvarx IPPROTO_UDP
2806 @var{optname} is an integer specifying an option within the protocol
2809 For @code{SOL_SOCKET} level the following @var{optname}s are defined
2810 (when provided by the system). For their meaning see
2811 @ref{Socket-Level Options,,, libc, The GNU C Library Reference
2812 Manual}, or @command{man 7 socket}.
2815 @defvarx SO_REUSEADDR
2819 @defvarx SO_DONTROUTE
2820 @defvarx SO_BROADCAST
2823 @defvarx SO_KEEPALIVE
2824 @defvarx SO_OOBINLINE
2825 @defvarx SO_NO_CHECK
2826 @defvarx SO_PRIORITY
2827 The @var{value} taken or returned is an integer.
2831 The @var{value} taken or returned is a pair of integers
2832 @code{(@var{ENABLE} . @var{TIMEOUT})}. On old systems without timeout
2833 support (ie.@: without @code{struct linger}), only @var{ENABLE} has an
2834 effect but the value in Guile is always a pair.
2837 @c Note that we refer only to ``man ip'' here. On GNU/Linux it's
2838 @c ``man 7 ip'' but on NetBSD it's ``man 4 ip''.
2840 For IP level (@code{IPPROTO_IP}) the following @var{optname}s are
2841 defined (when provided by the system). See @command{man ip} for what
2844 @defvar IP_ADD_MEMBERSHIP
2845 @defvarx IP_DROP_MEMBERSHIP
2846 These can be used only with @code{setsockopt}, not @code{getsockopt}.
2847 @var{value} is a pair @code{(@var{MULTIADDR} . @var{INTERFACEADDR})}
2848 of integer IPv4 addresses (@pxref{Network Address Conversion}).
2849 @var{MULTIADDR} is a multicast address to be added to or dropped from
2850 the interface @var{INTERFACEADDR}. @var{INTERFACEADDR} can be
2851 @code{INADDR_ANY} to have the system select the interface.
2852 @var{INTERFACEADDR} can also be an interface index number, on systems
2857 @deffn {Scheme Procedure} shutdown sock how
2858 @deffnx {C Function} scm_shutdown (sock, how)
2859 Sockets can be closed simply by using @code{close-port}. The
2860 @code{shutdown} procedure allows reception or transmission on a
2861 connection to be shut down individually, according to the parameter
2866 Stop receiving data for this socket. If further data arrives, reject it.
2868 Stop trying to transmit data from this socket. Discard any
2869 data waiting to be sent. Stop looking for acknowledgement of
2870 data already sent; don't retransmit it if it is lost.
2872 Stop both reception and transmission.
2875 The return value is unspecified.
2878 @deffn {Scheme Procedure} connect sock sockaddr
2879 @deffnx {Scheme Procedure} connect sock AF_INET ipv4addr port
2880 @deffnx {Scheme Procedure} connect sock AF_INET6 ipv6addr port [flowinfo [scopeid]]
2881 @deffnx {Scheme Procedure} connect sock AF_UNIX path
2882 @deffnx {C Function} scm_connect (sock, fam, address, args)
2883 Initiate a connection on socket port @var{sock} to a given address.
2884 The destination is either a socket address object, or arguments the
2885 same as @code{make-socket-address} would take to make such an object
2886 (@pxref{Network Socket Address}). The return value is unspecified.
2889 (connect sock AF_INET INADDR_LOCALHOST 23)
2890 (connect sock (make-socket-address AF_INET INADDR_LOCALHOST 23))
2894 @deffn {Scheme Procedure} bind sock sockaddr
2895 @deffnx {Scheme Procedure} bind sock AF_INET ipv4addr port
2896 @deffnx {Scheme Procedure} bind sock AF_INET6 ipv6addr port [flowinfo [scopeid]]
2897 @deffnx {Scheme Procedure} bind sock AF_UNIX path
2898 @deffnx {C Function} scm_bind (sock, fam, address, args)
2899 Bind socket port @var{sock} to the given address. The address is
2900 either a socket address object, or arguments the same as
2901 @code{make-socket-address} would take to make such an object
2902 (@pxref{Network Socket Address}). The return value is unspecified.
2904 Generally a socket is only explicitly bound to a particular address
2905 when making a server, ie. to listen on a particular port. For an
2906 outgoing connection the system will assign a local address
2907 automatically, if not already bound.
2910 (bind sock AF_INET INADDR_ANY 12345)
2911 (bind sock (make-socket-address AF_INET INADDR_ANY 12345))
2915 @deffn {Scheme Procedure} listen sock backlog
2916 @deffnx {C Function} scm_listen (sock, backlog)
2917 Enable @var{sock} to accept connection
2918 requests. @var{backlog} is an integer specifying
2919 the maximum length of the queue for pending connections.
2920 If the queue fills, new clients will fail to connect until
2921 the server calls @code{accept} to accept a connection from
2924 The return value is unspecified.
2927 @deffn {Scheme Procedure} accept sock
2928 @deffnx {C Function} scm_accept (sock)
2929 Accept a connection from socket port @var{sock} which has been enabled
2930 for listening with @code{listen} above. If there are no incoming
2931 connections in the queue, wait until one is available (unless
2932 @code{O_NONBLOCK} has been set on the socket, @pxref{Ports and File
2933 Descriptors,@code{fcntl}}).
2935 The return value is a pair. The @code{car} is a new socket port,
2936 connected and ready to communicate. The @code{cdr} is a socket
2937 address object (@pxref{Network Socket Address}) which is where the
2938 remote connection is from (like @code{getpeername} below).
2940 All communication takes place using the new socket returned. The
2941 given @var{sock} remains bound and listening, and @code{accept} may be
2942 called on it again to get another incoming connection when desired.
2945 @deffn {Scheme Procedure} getsockname sock
2946 @deffnx {C Function} scm_getsockname (sock)
2947 Return a socket address object which is the where @var{sock} is bound
2948 locally. @var{sock} may have obtained its local address from
2949 @code{bind} (above), or if a @code{connect} is done with an otherwise
2950 unbound socket (which is usual) then the system will have assigned an
2953 Note that on many systems the address of a socket in the
2954 @code{AF_UNIX} namespace cannot be read.
2957 @deffn {Scheme Procedure} getpeername sock
2958 @deffnx {C Function} scm_getpeername (sock)
2959 Return a socket address object which is where @var{sock} is connected
2960 to, ie. the remote endpoint.
2962 Note that on many systems the address of a socket in the
2963 @code{AF_UNIX} namespace cannot be read.
2966 @deffn {Scheme Procedure} recv! sock buf [flags]
2967 @deffnx {C Function} scm_recv (sock, buf, flags)
2968 Receive data from a socket port.
2969 @var{sock} must already
2970 be bound to the address from which data is to be received.
2971 @var{buf} is a string into which
2972 the data will be written. The size of @var{buf} limits
2974 data which can be received: in the case of packet
2975 protocols, if a packet larger than this limit is encountered
2977 will be irrevocably lost.
2981 @vindex MSG_DONTROUTE
2982 The optional @var{flags} argument is a value or bitwise OR of
2983 @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
2985 The value returned is the number of bytes read from the
2988 Note that the data is read directly from the socket file
2990 any unread buffered port data is ignored.
2993 @deffn {Scheme Procedure} send sock message [flags]
2994 @deffnx {C Function} scm_send (sock, message, flags)
2997 @vindex MSG_DONTROUTE
2998 Transmit the string @var{message} on a socket port @var{sock}.
2999 @var{sock} must already be bound to a destination address. The value
3000 returned is the number of bytes transmitted---it's possible for this
3001 to be less than the length of @var{message} if the socket is set to be
3002 non-blocking. The optional @var{flags} argument is a value or bitwise
3003 OR of @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3005 Note that the data is written directly to the socket
3007 any unflushed buffered port data is ignored.
3010 @deffn {Scheme Procedure} recvfrom! sock str [flags [start [end]]]
3011 @deffnx {C Function} scm_recvfrom (sock, str, flags, start, end)
3012 Receive data from socket port @var{sock}, returning the originating
3013 address as well as the data. This function is usually for datagram
3014 sockets, but can be used on stream-oriented sockets too.
3016 The data received is stored in the given @var{str}, the whole string
3017 or just the region between the optional @var{start} and @var{end}
3018 positions. The size of @var{str} limits the amount of data which can
3019 be received. For datagram protocols if a packet larger than this is
3020 received then excess bytes are irrevocably lost.
3022 The return value is a pair. The @code{car} is the number of bytes
3023 read. The @code{cdr} is a socket address object (@pxref{Network
3024 Socket Address}) which is where the data came from, or @code{#f} if
3025 the origin is unknown.
3029 @vindex MSG_DONTROUTE
3030 The optional @var{flags} argument is a or bitwise-OR (@code{logior})
3031 of @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3033 Data is read directly from the socket file descriptor, any buffered
3034 port data is ignored.
3036 @c This was linux kernel 2.6.15 and glibc 2.3.6, not sure what any
3037 @c specs are supposed to say about recvfrom threading.
3039 On a GNU/Linux system @code{recvfrom!} is not multi-threading, all
3040 threads stop while a @code{recvfrom!} call is in progress. An
3041 application may need to use @code{select}, @code{O_NONBLOCK} or
3042 @code{MSG_DONTWAIT} to avoid this.
3045 @deffn {Scheme Procedure} sendto sock message sockaddr [flags]
3046 @deffnx {Scheme Procedure} sendto sock message AF_INET ipv4addr port [flags]
3047 @deffnx {Scheme Procedure} sendto sock message AF_INET6 ipv6addr port [flowinfo [scopeid [flags]]]
3048 @deffnx {Scheme Procedure} sendto sock message AF_UNIX path [flags]
3049 @deffnx {C Function} scm_sendto (sock, message, fam, address, args_and_flags)
3050 Transmit the string @var{message} as a datagram on socket port
3051 @var{sock}. The destination is specified either as a socket address
3052 object, or as arguments the same as would be taken by
3053 @code{make-socket-address} to create such an object (@pxref{Network
3056 The destination address may be followed by an optional @var{flags}
3057 argument which is a @code{logior} (@pxref{Bitwise Operations}) of
3058 @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3060 The value returned is the number of bytes transmitted --
3062 this to be less than the length of @var{message} if the
3064 set to be non-blocking.
3065 Note that the data is written directly to the socket
3067 any unflushed buffered port data is ignored.
3070 The following functions can be used to convert short and long integers
3071 between ``host'' and ``network'' order. Although the procedures above do
3072 this automatically for addresses, the conversion will still need to
3073 be done when sending or receiving encoded integer data from the network.
3075 @deffn {Scheme Procedure} htons value
3076 @deffnx {C Function} scm_htons (value)
3077 Convert a 16 bit quantity from host to network byte ordering.
3078 @var{value} is packed into 2 bytes, which are then converted
3079 and returned as a new integer.
3082 @deffn {Scheme Procedure} ntohs value
3083 @deffnx {C Function} scm_ntohs (value)
3084 Convert a 16 bit quantity from network to host byte ordering.
3085 @var{value} is packed into 2 bytes, which are then converted
3086 and returned as a new integer.
3089 @deffn {Scheme Procedure} htonl value
3090 @deffnx {C Function} scm_htonl (value)
3091 Convert a 32 bit quantity from host to network byte ordering.
3092 @var{value} is packed into 4 bytes, which are then converted
3093 and returned as a new integer.
3096 @deffn {Scheme Procedure} ntohl value
3097 @deffnx {C Function} scm_ntohl (value)
3098 Convert a 32 bit quantity from network to host byte ordering.
3099 @var{value} is packed into 4 bytes, which are then converted
3100 and returned as a new integer.
3103 These procedures are inconvenient to use at present, but consider:
3106 (define write-network-long
3107 (lambda (value port)
3108 (let ((v (make-uniform-vector 1 1 0)))
3109 (uniform-vector-set! v 0 (htonl value))
3110 (uniform-vector-write v port))))
3112 (define read-network-long
3114 (let ((v (make-uniform-vector 1 1 0)))
3115 (uniform-vector-read! v port)
3116 (ntohl (uniform-vector-ref v 0)))))
3120 @node Internet Socket Examples
3121 @subsubsection Network Socket Examples
3122 @cindex network examples
3123 @cindex socket examples
3125 The following give examples of how to use network sockets.
3127 @subsubheading Internet Socket Client Example
3129 @cindex socket client example
3130 The following example demonstrates an Internet socket client.
3131 It connects to the HTTP daemon running on the local machine and
3132 returns the contents of the root index URL.
3135 (let ((s (socket PF_INET SOCK_STREAM 0)))
3136 (connect s AF_INET (inet-aton "127.0.0.1") 80)
3137 (display "GET / HTTP/1.0\r\n\r\n" s)
3139 (do ((line (read-line s) (read-line s)))
3140 ((eof-object? line))
3146 @subsubheading Internet Socket Server Example
3148 @cindex socket server example
3149 The following example shows a simple Internet server which listens on
3150 port 2904 for incoming connections and sends a greeting back to the
3154 (let ((s (socket PF_INET SOCK_STREAM 0)))
3155 (setsockopt s SOL_SOCKET SO_REUSEADDR 1)
3156 ;; @r{Specific address?}
3157 ;; @r{(bind s AF_INET (inet-aton "127.0.0.1") 2904)}
3158 (bind s AF_INET INADDR_ANY 2904)
3161 (simple-format #t "Listening for clients in pid: ~S" (getpid))
3165 (let* ((client-connection (accept s))
3166 (client-details (cdr client-connection))
3167 (client (car client-connection)))
3168 (simple-format #t "Got new client connection: ~S"
3171 (simple-format #t "Client address: ~S"
3173 (sockaddr:addr client-details)))
3175 ;; @r{Send back the greeting to the client port}
3176 (display "Hello client\r\n" client)
3181 @node System Identification
3182 @subsection System Identification
3185 This section lists the various procedures Guile provides for accessing
3186 information about the system it runs on.
3188 @deffn {Scheme Procedure} uname
3189 @deffnx {C Function} scm_uname ()
3190 Return an object with some information about the computer
3191 system the program is running on.
3193 The following procedures accept an object as returned by @code{uname}
3194 and return a selected component (all of which are strings).
3196 @deffn {Scheme Procedure} utsname:sysname un
3197 The name of the operating system.
3199 @deffn {Scheme Procedure} utsname:nodename un
3200 The network name of the computer.
3202 @deffn {Scheme Procedure} utsname:release un
3203 The current release level of the operating system implementation.
3205 @deffn {Scheme Procedure} utsname:version un
3206 The current version level within the release of the operating system.
3208 @deffn {Scheme Procedure} utsname:machine un
3209 A description of the hardware.
3213 @deffn {Scheme Procedure} gethostname
3214 @deffnx {C Function} scm_gethostname ()
3216 Return the host name of the current processor.
3219 @deffn {Scheme Procedure} sethostname name
3220 @deffnx {C Function} scm_sethostname (name)
3221 Set the host name of the current processor to @var{name}. May
3222 only be used by the superuser. The return value is not
3230 @deffn {Scheme Procedure} setlocale category [locale]
3231 @deffnx {C Function} scm_setlocale (category, locale)
3232 Get or set the current locale, used for various internationalizations.
3233 Locales are strings, such as @samp{sv_SE}.
3235 If @var{locale} is given then the locale for the given @var{category}
3236 is set and the new value returned. If @var{locale} is not given then
3237 the current value is returned. @var{category} should be one of the
3238 following values (@pxref{Locale Categories, Categories of Activities
3239 that Locales Affect,, libc, The GNU C Library Reference Manual}):
3244 @defvarx LC_MESSAGES
3245 @defvarx LC_MONETARY
3251 A common usage is @samp{(setlocale LC_ALL "")}, which initializes all
3252 categories based on standard environment variables (@code{LANG} etc).
3253 For full details on categories and locale names @pxref{Locales,,
3254 Locales and Internationalization, libc, The GNU C Library Reference
3257 Note that @code{setlocale} affects locale settings for the whole
3258 process. @xref{i18n Introduction, locale objects and
3259 @code{make-locale}}, for a thread-safe alternative.
3263 @subsection Encryption
3266 Please note that the procedures in this section are not suited for
3267 strong encryption, they are only interfaces to the well-known and
3268 common system library functions of the same name. They are just as good
3269 (or bad) as the underlying functions, so you should refer to your system
3270 documentation before using them (@pxref{crypt,, Encrypting Passwords,
3271 libc, The GNU C Library Reference Manual}).
3273 @deffn {Scheme Procedure} crypt key salt
3274 @deffnx {C Function} scm_crypt (key, salt)
3275 Encrypt @var{key}, with the addition of @var{salt} (both strings),
3276 using the @code{crypt} C library call.
3279 Although @code{getpass} is not an encryption procedure per se, it
3280 appears here because it is often used in combination with @code{crypt}:
3282 @deffn {Scheme Procedure} getpass prompt
3283 @deffnx {C Function} scm_getpass (prompt)
3285 Display @var{prompt} to the standard error output and read
3286 a password from @file{/dev/tty}. If this file is not
3287 accessible, it reads from standard input. The password may be
3288 up to 127 characters in length. Additional characters and the
3289 terminating newline character are discarded. While reading
3290 the password, echoing and the generation of signals by special
3291 characters is disabled.
3296 @c TeX-master: "guile.texi"