warn on multithreaded fork
[bpt/guile.git] / doc / ref / posix.texi
1 @c -*-texinfo-*-
2 @c This is part of the GNU Guile Reference Manual.
3 @c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2007,
4 @c 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
5 @c See the file guile.texi for copying conditions.
6
7 @node POSIX
8 @section @acronym{POSIX} System Calls and Networking
9 @cindex POSIX
10
11 @menu
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.
26 * Encryption::
27 @end menu
28
29 @node Conventions
30 @subsection @acronym{POSIX} Interface Conventions
31
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)}).
36
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}.
41
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.
46
47 General naming conventions are as follows:
48
49 @itemize @bullet
50 @item
51 The Scheme name is often identical to the name of the underlying Unix
52 facility.
53 @item
54 Underscores in Unix procedure names are converted to hyphens.
55 @item
56 Procedures which destructively modify Scheme data have exclamation
57 marks appended, e.g., @code{recv!}.
58 @item
59 Predicates (returning only @code{#t} or @code{#f}) have question marks
60 appended, e.g., @code{access?}.
61 @item
62 Some names are changed to avoid conflict with dissimilar interfaces
63 defined by scsh, e.g., @code{primitive-fork}.
64 @item
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
67 with hyphens).
68 @end itemize
69
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
74 the documentation.
75
76 For ways to deal with exceptions, see @ref{Exceptions}.
77
78 @cindex @code{errno}
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,
84
85 @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))
91
92 (catch 'system-error
93 (lambda () (dup2 -123 -456))
94 my-handler)
95
96 @print{}
97 system-error
98 dup2
99 Bad file descriptor
100 (9)
101 @end example
102
103
104 @sp 1
105 @defun system-error-errno arglist
106 @cindex @code{errno}
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,
110
111 @example
112 (catch
113 'system-error
114 (lambda ()
115 (mkdir "/this-ought-to-fail-if-I'm-not-root"))
116 (lambda stuff
117 (let ((errno (system-error-errno stuff)))
118 (cond
119 ((= errno EACCES)
120 (display "You're not allowed to do that."))
121 ((= errno EEXIST)
122 (display "Already exists."))
123 (#t
124 (display (strerror errno))))
125 (newline))))
126 @end example
127 @end defun
128
129
130 @node Ports and File Descriptors
131 @subsection Ports and File Descriptors
132 @cindex file descriptor
133
134 Conventions generally follow those of scsh, @ref{The Scheme shell (scsh)}.
135
136 File ports are implemented using low-level operating system I/O
137 facilities, with optional buffering to improve efficiency; see
138 @ref{File Ports}.
139
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}.
144
145 The @code{force-output} and @code{drain-input} procedures can be used
146 to clear the buffers.
147
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
151 environment.
152
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.
159
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.
167
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.
175
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}.
183
184 @deffn {Scheme Procedure} port-revealed port
185 @deffnx {C Function} scm_port_revealed (port)
186 Return the revealed count for @var{port}.
187 @end deffn
188
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.
193 @end deffn
194
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.
199 @end deffn
200
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.
204 @end deffn
205
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}).
212 @end deffn
213
214 @deffn {Scheme Procedure} fdes->ports fdes
215 @deffnx {C Function} scm_fdes_to_ports (fdes)
216 Return a list of existing ports which have @var{fdes} as an
217 underlying file descriptor, without changing their revealed
218 counts.
219 @end deffn
220
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.
225 @end deffn
226
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.
231 @end deffn
232
233 @deffn {Scheme Procedure} primitive-move->fdes port fdes
234 @deffnx {C Function} scm_primitive_move_to_fdes (port, fdes)
235 Moves the underlying file descriptor for @var{port} to the integer
236 value @var{fdes} without changing the revealed count of @var{port}.
237 Any other ports already using this descriptor will be automatically
238 shifted to new descriptors and their revealed counts reset to zero.
239 The return value is @code{#f} if the file descriptor already had the
240 required value or @code{#t} if it was moved.
241 @end deffn
242
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.
249 @end deffn
250
251 @deffn {Scheme Procedure} release-port-handle port
252 Decrements the revealed count for a port.
253 @end deffn
254
255 @deffn {Scheme Procedure} fsync port_or_fd
256 @deffnx {C Function} scm_fsync (port_or_fd)
257 Copies any unwritten data for the specified output file descriptor to disk.
258 If @var{port_or_fd} is a port, its buffer is flushed before the underlying
259 file descriptor is fsync'd.
260 The return value is unspecified.
261 @end deffn
262
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).
270
271 @var{flags} can be constructed by combining variables using @code{logior}.
272 Basic flags are:
273
274 @defvar O_RDONLY
275 Open the file read-only.
276 @end defvar
277 @defvar O_WRONLY
278 Open the file write-only.
279 @end defvar
280 @defvar O_RDWR
281 Open the file read/write.
282 @end defvar
283 @defvar O_APPEND
284 Append to the file instead of truncating.
285 @end defvar
286 @defvar O_CREAT
287 Create the file if it does not already exist.
288 @end defvar
289
290 @xref{File Status Flags,,,libc,The GNU C Library Reference Manual},
291 for additional flags.
292 @end deffn
293
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
297 a port.
298 @end deffn
299
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.
307 @end deffn
308
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.
315 @end deffn
316
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
323 used.
324 @end deffn
325
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.
331 @end deffn
332
333 @deffn {Scheme Procedure} pipe
334 @deffnx {C Function} scm_pipe ()
335 @cindex 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}.
343
344 @defvar PIPE_BUF
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}).
349 @end defvar
350
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.
354 @end deffn
355
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.
361
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.
365
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.
371 @end deffn
372
373 @deffn {Scheme Procedure} dup->inport port/fd [newfd]
374 Returns a new input port using the new file descriptor.
375 @end deffn
376
377 @deffn {Scheme Procedure} dup->outport port/fd [newfd]
378 Returns a new output port using the new file descriptor.
379 @end deffn
380
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.
384 @end deffn
385
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}).
389 @end deffn
390
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.
396
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
400 port.
401
402 This procedure is equivalent to @code{(dup->port @var{port} @var{modes})}.
403 @end deffn
404
405 @deffn {Scheme Procedure} redirect-port old_port new_port
406 @deffnx {C Function} scm_redirect_port (old_port, new_port)
407 This procedure takes two ports and duplicates the underlying file
408 descriptor from @var{old_port} into @var{new_port}. The
409 current file descriptor in @var{new_port} will be closed.
410 After the redirection the two ports will share a file position
411 and file status flags.
412
413 The return value is unspecified.
414
415 Unexpected behaviour can result if both ports are subsequently used
416 and the original and/or duplicate ports are buffered.
417
418 This procedure does not have any side effects on other ports or
419 revealed counts.
420 @end deffn
421
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
428 be integers.
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.
432 @end deffn
433
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.
439 @end deffn
440
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.
451
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}
455 cookie.
456 @end deffn
457
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:
462
463 @defvar _IONBF
464 non-buffered
465 @end defvar
466 @defvar _IOLBF
467 line buffered
468 @end defvar
469 @defvar _IOFBF
470 block buffered, using a newly allocated buffer of @var{size} bytes.
471 If @var{size} is omitted, a default size will be used.
472 @end defvar
473 @end deffn
474
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.
480
481 Values for @var{cmd} are:
482
483 @defvar F_DUPFD
484 Duplicate the file descriptor, the same as @code{dup->fdes} above
485 does.
486 @end defvar
487
488 @defvar F_GETFD
489 @defvarx F_SETFD
490 Get or set flags associated with the file descriptor. The only flag
491 is the following,
492
493 @defvar FD_CLOEXEC
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
496 flag,
497
498 @example
499 (fcntl port F_SETFD FD_CLOEXEC)
500 @end example
501
502 Or better, set it but leave any other possible future flags unchanged,
503
504 @example
505 (fcntl port F_SETFD (logior FD_CLOEXEC
506 (fcntl port F_GETFD)))
507 @end example
508 @end defvar
509 @end defvar
510
511 @defvar F_GETFL
512 @defvarx F_SETFL
513 Get or set flags associated with the open file. These flags are
514 @code{O_RDONLY} etc described under @code{open} above.
515
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.
518
519 @example
520 (fcntl sock F_SETFL (logior O_NONBLOCK
521 (fcntl sock F_GETFL)))
522 @end example
523 @end defvar
524
525 @defvar F_GETOWN
526 @defvarx F_SETOWN
527 Get or set the process ID of a socket's owner, for @code{SIGIO} signals.
528 @end defvar
529 @end deffn
530
531 @deffn {Scheme Procedure} flock file operation
532 @deffnx {C Function} scm_flock (file, operation)
533 @cindex file locking
534 Apply or remove an advisory lock on an open file.
535 @var{operation} specifies the action to be done:
536
537 @defvar LOCK_SH
538 Shared lock. More than one process may hold a shared lock
539 for a given file at a given time.
540 @end defvar
541 @defvar LOCK_EX
542 Exclusive lock. Only one process may hold an exclusive lock
543 for a given file at a given time.
544 @end defvar
545 @defvar LOCK_UN
546 Unlock the file.
547 @end defvar
548 @defvar LOCK_NB
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}).
553 @end defvar
554
555 The return value is not specified. @var{file} may be an open
556 file descriptor or an open file descriptor port.
557
558 Note that @code{flock} does not lock files across NFS.
559 @end deffn
560
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.
568
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.
576
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.
585
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.
592 @end deffn
593
594 @node File System
595 @subsection File System
596 @cindex file system
597
598 These procedures allow querying and setting file system attributes
599 (such as owner,
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.
603
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
609 not.
610
611 @var{how} is an integer which is one of the following values, or a
612 bitwise-OR (@code{logior}) of multiple values.
613
614 @defvar R_OK
615 Test for read permission.
616 @end defvar
617 @defvar W_OK
618 Test for write permission.
619 @end defvar
620 @defvar X_OK
621 Test for execute permission.
622 @end defvar
623 @defvar F_OK
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.
626 @end defvar
627
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.
633
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
638 catch any exception.
639
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}.
645 @end deffn
646
647 @findex fstat
648 @deffn {Scheme Procedure} stat object
649 @deffnx {C Function} scm_stat (object)
650 Return an object containing various information about the file
651 determined by @var{object}. @var{object} can be a string containing
652 a file name or a port or integer file descriptor which is open
653 on a file (in which case @code{fstat} is used as the underlying
654 system call).
655
656 The object returned by @code{stat} can be passed as a single
657 parameter to the following procedures, all of which return
658 integers:
659
660 @deffn {Scheme Procedure} stat:dev st
661 The device number containing the file.
662 @end deffn
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.
666 @end deffn
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.
671 @end deffn
672 @deffn {Scheme Procedure} stat:nlink st
673 The number of hard links to the file.
674 @end deffn
675 @deffn {Scheme Procedure} stat:uid st
676 The user ID of the file's owner.
677 @end deffn
678 @deffn {Scheme Procedure} stat:gid st
679 The group ID of the file.
680 @end deffn
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}.
685 @end deffn
686 @deffn {Scheme Procedure} stat:size st
687 The size of a regular file in bytes.
688 @end deffn
689 @deffn {Scheme Procedure} stat:atime st
690 The last access time for the file, in seconds.
691 @end deffn
692 @deffn {Scheme Procedure} stat:mtime st
693 The last modification time for the file, in seconds.
694 @end deffn
695 @deffn {Scheme Procedure} stat:ctime st
696 The last modification time for the attributes of the file, in seconds.
697 @end deffn
698 @deffn {Scheme Procedure} stat:atimensec st
699 @deffnx {Scheme Procedure} stat:mtimensec st
700 @deffnx {Scheme Procedure} stat:ctimensec st
701 The fractional part of a file's access, modification, or attribute modification
702 time, in nanoseconds. Nanosecond timestamps are only available on some operating
703 systems and file systems. If Guile cannot retrieve nanosecond-level timestamps
704 for a file, these fields will be set to 0.
705 @end deffn
706 @deffn {Scheme Procedure} stat:blksize st
707 The optimal block size for reading or writing the file, in bytes. On
708 some systems this field is not available, in which case
709 @code{stat:blksize} returns a sensible suggested block size.
710 @end deffn
711 @deffn {Scheme Procedure} stat:blocks st
712 The amount of disk space that the file occupies measured in units of
713 512 byte blocks. On some systems this field is not available, in
714 which case @code{stat:blocks} returns @code{#f}.
715 @end deffn
716
717 In addition, the following procedures return the information
718 from @code{stat:mode} in a more convenient form:
719
720 @deffn {Scheme Procedure} stat:type st
721 A symbol representing the type of file. Possible values are
722 @samp{regular}, @samp{directory}, @samp{symlink},
723 @samp{block-special}, @samp{char-special}, @samp{fifo}, @samp{socket},
724 and @samp{unknown}.
725 @end deffn
726 @deffn {Scheme Procedure} stat:perms st
727 An integer representing the access permission bits.
728 @end deffn
729 @end deffn
730
731 @deffn {Scheme Procedure} lstat path
732 @deffnx {C Function} scm_lstat (path)
733 Similar to @code{stat}, but does not follow symbolic links, i.e.,
734 it will return information about a symbolic link itself, not the
735 file it points to. @var{path} must be a string.
736 @end deffn
737
738 @deffn {Scheme Procedure} readlink path
739 @deffnx {C Function} scm_readlink (path)
740 Return the value of the symbolic link named by @var{path} (a
741 string), i.e., the file that the link points to.
742 @end deffn
743
744 @findex fchown
745 @findex lchown
746 @deffn {Scheme Procedure} chown object owner group
747 @deffnx {C Function} scm_chown (object, owner, group)
748 Change the ownership and group of the file referred to by @var{object}
749 to the integer values @var{owner} and @var{group}. @var{object} can
750 be a string containing a file name or, if the platform supports
751 @code{fchown} (@pxref{File Owner,,,libc,The GNU C Library Reference
752 Manual}), a port or integer file descriptor which is open on the file.
753 The return value is unspecified.
754
755 If @var{object} is a symbolic link, either the
756 ownership of the link or the ownership of the referenced file will be
757 changed depending on the operating system (lchown is
758 unsupported at present). If @var{owner} or @var{group} is specified
759 as @code{-1}, then that ID is not changed.
760 @end deffn
761
762 @findex fchmod
763 @deffn {Scheme Procedure} chmod object mode
764 @deffnx {C Function} scm_chmod (object, mode)
765 Changes the permissions of the file referred to by @var{object}.
766 @var{object} can be a string containing a file name or a port or integer file
767 descriptor which is open on a file (in which case @code{fchmod} is used
768 as the underlying system call).
769 @var{mode} specifies
770 the new permissions as a decimal number, e.g., @code{(chmod "foo" #o755)}.
771 The return value is unspecified.
772 @end deffn
773
774 @deffn {Scheme Procedure} utime pathname [actime [modtime [actimens [modtimens [flags]]]]]
775 @deffnx {C Function} scm_utime (pathname, actime, modtime, actimens, modtimens, flags)
776 @code{utime} sets the access and modification times for the
777 file named by @var{pathname}. If @var{actime} or @var{modtime} is
778 not supplied, then the current time is used. @var{actime} and
779 @var{modtime} must be integer time values as returned by the
780 @code{current-time} procedure.
781
782 The optional @var{actimens} and @var{modtimens} are nanoseconds
783 to add @var{actime} and @var{modtime}. Nanosecond precision is
784 only supported on some combinations of file systems and operating
785 systems.
786 @lisp
787 (utime "foo" (- (current-time) 3600))
788 @end lisp
789 will set the access time to one hour in the past and the
790 modification time to the current time.
791 @end deffn
792
793 @findex unlink
794 @deffn {Scheme Procedure} delete-file str
795 @deffnx {C Function} scm_delete_file (str)
796 Deletes (or ``unlinks'') the file whose path is specified by
797 @var{str}.
798 @end deffn
799
800 @deffn {Scheme Procedure} copy-file oldfile newfile
801 @deffnx {C Function} scm_copy_file (oldfile, newfile)
802 Copy the file specified by @var{oldfile} to @var{newfile}.
803 The return value is unspecified.
804 @end deffn
805
806 @findex rename
807 @deffn {Scheme Procedure} rename-file oldname newname
808 @deffnx {C Function} scm_rename (oldname, newname)
809 Renames the file specified by @var{oldname} to @var{newname}.
810 The return value is unspecified.
811 @end deffn
812
813 @deffn {Scheme Procedure} link oldpath newpath
814 @deffnx {C Function} scm_link (oldpath, newpath)
815 Creates a new name @var{newpath} in the file system for the
816 file named by @var{oldpath}. If @var{oldpath} is a symbolic
817 link, the link may or may not be followed depending on the
818 system.
819 @end deffn
820
821 @deffn {Scheme Procedure} symlink oldpath newpath
822 @deffnx {C Function} scm_symlink (oldpath, newpath)
823 Create a symbolic link named @var{newpath} with the value (i.e., pointing to)
824 @var{oldpath}. The return value is unspecified.
825 @end deffn
826
827 @deffn {Scheme Procedure} mkdir path [mode]
828 @deffnx {C Function} scm_mkdir (path, mode)
829 Create a new directory named by @var{path}. If @var{mode} is omitted
830 then the permissions of the directory file are set using the current
831 umask (@pxref{Processes}). Otherwise they are set to the decimal
832 value specified with @var{mode}. The return value is unspecified.
833 @end deffn
834
835 @deffn {Scheme Procedure} rmdir path
836 @deffnx {C Function} scm_rmdir (path)
837 Remove the existing directory named by @var{path}. The directory must
838 be empty for this to succeed. The return value is unspecified.
839 @end deffn
840
841 @deffn {Scheme Procedure} opendir dirname
842 @deffnx {C Function} scm_opendir (dirname)
843 @cindex directory contents
844 Open the directory specified by @var{dirname} and return a directory
845 stream.
846
847 Before using this and the procedures below, make sure to see the
848 higher-level procedures for directory traversal that are available
849 (@pxref{File Tree Walk}).
850 @end deffn
851
852 @deffn {Scheme Procedure} directory-stream? object
853 @deffnx {C Function} scm_directory_stream_p (object)
854 Return a boolean indicating whether @var{object} is a directory
855 stream as returned by @code{opendir}.
856 @end deffn
857
858 @deffn {Scheme Procedure} readdir stream
859 @deffnx {C Function} scm_readdir (stream)
860 Return (as a string) the next directory entry from the directory stream
861 @var{stream}. If there is no remaining entry to be read then the
862 end of file object is returned.
863 @end deffn
864
865 @deffn {Scheme Procedure} rewinddir stream
866 @deffnx {C Function} scm_rewinddir (stream)
867 Reset the directory port @var{stream} so that the next call to
868 @code{readdir} will return the first directory entry.
869 @end deffn
870
871 @deffn {Scheme Procedure} closedir stream
872 @deffnx {C Function} scm_closedir (stream)
873 Close the directory stream @var{stream}.
874 The return value is unspecified.
875 @end deffn
876
877 Here is an example showing how to display all the entries in a
878 directory:
879
880 @lisp
881 (define dir (opendir "/usr/lib"))
882 (do ((entry (readdir dir) (readdir dir)))
883 ((eof-object? entry))
884 (display entry)(newline))
885 (closedir dir)
886 @end lisp
887
888 @deffn {Scheme Procedure} sync
889 @deffnx {C Function} scm_sync ()
890 Flush the operating system disk buffers.
891 The return value is unspecified.
892 @end deffn
893
894 @deffn {Scheme Procedure} mknod path type perms dev
895 @deffnx {C Function} scm_mknod (path, type, perms, dev)
896 @cindex device file
897 Creates a new special file, such as a file corresponding to a device.
898 @var{path} specifies the name of the file. @var{type} should be one
899 of the following symbols: @samp{regular}, @samp{directory},
900 @samp{symlink}, @samp{block-special}, @samp{char-special},
901 @samp{fifo}, or @samp{socket}. @var{perms} (an integer) specifies the
902 file permissions. @var{dev} (an integer) specifies which device the
903 special file refers to. Its exact interpretation depends on the kind
904 of special file being created.
905
906 E.g.,
907 @lisp
908 (mknod "/dev/fd0" 'block-special #o660 (+ (* 2 256) 2))
909 @end lisp
910
911 The return value is unspecified.
912 @end deffn
913
914 @deffn {Scheme Procedure} tmpnam
915 @deffnx {C Function} scm_tmpnam ()
916 @cindex temporary file
917 Return an auto-generated name of a temporary file, a file which
918 doesn't already exist. The name includes a path, it's usually in
919 @file{/tmp} but that's system dependent.
920
921 Care must be taken when using @code{tmpnam}. In between choosing the
922 name and creating the file another program might use that name, or an
923 attacker might even make it a symlink pointing at something important
924 and causing you to overwrite that.
925
926 The safe way is to create the file using @code{open} with
927 @code{O_EXCL} to avoid any overwriting. A loop can try again with
928 another name if the file exists (error @code{EEXIST}).
929 @code{mkstemp!} below does that.
930 @end deffn
931
932 @deffn {Scheme Procedure} mkstemp! tmpl
933 @deffnx {C Function} scm_mkstemp (tmpl)
934 @cindex temporary file
935 Create a new unique file in the file system and return a new buffered
936 port open for reading and writing to the file.
937
938 @var{tmpl} is a string specifying where the file should be created: it
939 must end with @samp{XXXXXX} and those @samp{X}s will be changed in the
940 string to return the name of the file. (@code{port-filename} on the
941 port also gives the name.)
942
943 POSIX doesn't specify the permissions mode of the file, on GNU and
944 most systems it's @code{#o600}. An application can use @code{chmod}
945 to relax that if desired. For example @code{#o666} less @code{umask},
946 which is usual for ordinary file creation,
947
948 @example
949 (let ((port (mkstemp! (string-copy "/tmp/myfile-XXXXXX"))))
950 (chmod port (logand #o666 (lognot (umask))))
951 ...)
952 @end example
953 @end deffn
954
955 @deffn {Scheme Procedure} tmpfile
956 @deffnx {C Function} scm_tmpfile ()
957 Return an input/output port to a unique temporary file
958 named using the path prefix @code{P_tmpdir} defined in
959 @file{stdio.h}.
960 The file is automatically deleted when the port is closed
961 or the program terminates.
962 @end deffn
963
964 @deffn {Scheme Procedure} dirname filename
965 @deffnx {C Function} scm_dirname (filename)
966 Return the directory name component of the file name
967 @var{filename}. If @var{filename} does not contain a directory
968 component, @code{.} is returned.
969 @end deffn
970
971 @deffn {Scheme Procedure} basename filename [suffix]
972 @deffnx {C Function} scm_basename (filename, suffix)
973 Return the base name of the file name @var{filename}. The
974 base name is the file name without any directory components.
975 If @var{suffix} is provided, and is equal to the end of
976 @var{basename}, it is removed also.
977
978 @lisp
979 (basename "/tmp/test.xml" ".xml")
980 @result{} "test"
981 @end lisp
982 @end deffn
983
984 @deffn {Scheme Procedure} file-exists? filename
985 Return @code{#t} if the file named @var{filename} exists, @code{#f} if
986 not.
987 @end deffn
988
989
990 @node User Information
991 @subsection User Information
992 @cindex user information
993 @cindex password file
994 @cindex group file
995
996 The facilities in this section provide an interface to the user and
997 group database.
998 They should be used with care since they are not reentrant.
999
1000 The following functions accept an object representing user information
1001 and return a selected component:
1002
1003 @deffn {Scheme Procedure} passwd:name pw
1004 The name of the userid.
1005 @end deffn
1006 @deffn {Scheme Procedure} passwd:passwd pw
1007 The encrypted passwd.
1008 @end deffn
1009 @deffn {Scheme Procedure} passwd:uid pw
1010 The user id number.
1011 @end deffn
1012 @deffn {Scheme Procedure} passwd:gid pw
1013 The group id number.
1014 @end deffn
1015 @deffn {Scheme Procedure} passwd:gecos pw
1016 The full name.
1017 @end deffn
1018 @deffn {Scheme Procedure} passwd:dir pw
1019 The home directory.
1020 @end deffn
1021 @deffn {Scheme Procedure} passwd:shell pw
1022 The login shell.
1023 @end deffn
1024 @sp 1
1025
1026 @deffn {Scheme Procedure} getpwuid uid
1027 Look up an integer userid in the user database.
1028 @end deffn
1029
1030 @deffn {Scheme Procedure} getpwnam name
1031 Look up a user name string in the user database.
1032 @end deffn
1033
1034 @deffn {Scheme Procedure} setpwent
1035 Initializes a stream used by @code{getpwent} to read from the user database.
1036 The next use of @code{getpwent} will return the first entry. The
1037 return value is unspecified.
1038 @end deffn
1039
1040 @deffn {Scheme Procedure} getpwent
1041 Read the next entry in the user database stream. The return is a
1042 passwd user object as above, or @code{#f} when no more entries.
1043 @end deffn
1044
1045 @deffn {Scheme Procedure} endpwent
1046 Closes the stream used by @code{getpwent}. The return value is unspecified.
1047 @end deffn
1048
1049 @deffn {Scheme Procedure} setpw [arg]
1050 @deffnx {C Function} scm_setpwent (arg)
1051 If called with a true argument, initialize or reset the password data
1052 stream. Otherwise, close the stream. The @code{setpwent} and
1053 @code{endpwent} procedures are implemented on top of this.
1054 @end deffn
1055
1056 @deffn {Scheme Procedure} getpw [user]
1057 @deffnx {C Function} scm_getpwuid (user)
1058 Look up an entry in the user database. @var{user} can be an integer,
1059 a string, or omitted, giving the behaviour of getpwuid, getpwnam
1060 or getpwent respectively.
1061 @end deffn
1062
1063 The following functions accept an object representing group information
1064 and return a selected component:
1065
1066 @deffn {Scheme Procedure} group:name gr
1067 The group name.
1068 @end deffn
1069 @deffn {Scheme Procedure} group:passwd gr
1070 The encrypted group password.
1071 @end deffn
1072 @deffn {Scheme Procedure} group:gid gr
1073 The group id number.
1074 @end deffn
1075 @deffn {Scheme Procedure} group:mem gr
1076 A list of userids which have this group as a supplementary group.
1077 @end deffn
1078 @sp 1
1079
1080 @deffn {Scheme Procedure} getgrgid gid
1081 Look up an integer group id in the group database.
1082 @end deffn
1083
1084 @deffn {Scheme Procedure} getgrnam name
1085 Look up a group name in the group database.
1086 @end deffn
1087
1088 @deffn {Scheme Procedure} setgrent
1089 Initializes a stream used by @code{getgrent} to read from the group database.
1090 The next use of @code{getgrent} will return the first entry.
1091 The return value is unspecified.
1092 @end deffn
1093
1094 @deffn {Scheme Procedure} getgrent
1095 Return the next entry in the group database, using the stream set by
1096 @code{setgrent}.
1097 @end deffn
1098
1099 @deffn {Scheme Procedure} endgrent
1100 Closes the stream used by @code{getgrent}.
1101 The return value is unspecified.
1102 @end deffn
1103
1104 @deffn {Scheme Procedure} setgr [arg]
1105 @deffnx {C Function} scm_setgrent (arg)
1106 If called with a true argument, initialize or reset the group data
1107 stream. Otherwise, close the stream. The @code{setgrent} and
1108 @code{endgrent} procedures are implemented on top of this.
1109 @end deffn
1110
1111 @deffn {Scheme Procedure} getgr [group]
1112 @deffnx {C Function} scm_getgrgid (group)
1113 Look up an entry in the group database. @var{group} can be an integer,
1114 a string, or omitted, giving the behaviour of getgrgid, getgrnam
1115 or getgrent respectively.
1116 @end deffn
1117
1118 In addition to the accessor procedures for the user database, the
1119 following shortcut procedure is also available.
1120
1121 @deffn {Scheme Procedure} getlogin
1122 @deffnx {C Function} scm_getlogin ()
1123 Return a string containing the name of the user logged in on
1124 the controlling terminal of the process, or @code{#f} if this
1125 information cannot be obtained.
1126 @end deffn
1127
1128
1129 @node Time
1130 @subsection Time
1131 @cindex time
1132
1133 @deffn {Scheme Procedure} current-time
1134 @deffnx {C Function} scm_current_time ()
1135 Return the number of seconds since 1970-01-01 00:00:00 @acronym{UTC},
1136 excluding leap seconds.
1137 @end deffn
1138
1139 @deffn {Scheme Procedure} gettimeofday
1140 @deffnx {C Function} scm_gettimeofday ()
1141 Return a pair containing the number of seconds and microseconds
1142 since 1970-01-01 00:00:00 @acronym{UTC}, excluding leap seconds. Note:
1143 whether true microsecond resolution is available depends on the
1144 operating system.
1145 @end deffn
1146
1147 The following procedures either accept an object representing a broken down
1148 time and return a selected component, or accept an object representing
1149 a broken down time and a value and set the component to the value.
1150 The numbers in parentheses give the usual range.
1151
1152 @deffn {Scheme Procedure} tm:sec tm
1153 @deffnx {Scheme Procedure} set-tm:sec tm val
1154 Seconds (0-59).
1155 @end deffn
1156 @deffn {Scheme Procedure} tm:min tm
1157 @deffnx {Scheme Procedure} set-tm:min tm val
1158 Minutes (0-59).
1159 @end deffn
1160 @deffn {Scheme Procedure} tm:hour tm
1161 @deffnx {Scheme Procedure} set-tm:hour tm val
1162 Hours (0-23).
1163 @end deffn
1164 @deffn {Scheme Procedure} tm:mday tm
1165 @deffnx {Scheme Procedure} set-tm:mday tm val
1166 Day of the month (1-31).
1167 @end deffn
1168 @deffn {Scheme Procedure} tm:mon tm
1169 @deffnx {Scheme Procedure} set-tm:mon tm val
1170 Month (0-11).
1171 @end deffn
1172 @deffn {Scheme Procedure} tm:year tm
1173 @deffnx {Scheme Procedure} set-tm:year tm val
1174 Year (70-), the year minus 1900.
1175 @end deffn
1176 @deffn {Scheme Procedure} tm:wday tm
1177 @deffnx {Scheme Procedure} set-tm:wday tm val
1178 Day of the week (0-6) with Sunday represented as 0.
1179 @end deffn
1180 @deffn {Scheme Procedure} tm:yday tm
1181 @deffnx {Scheme Procedure} set-tm:yday tm val
1182 Day of the year (0-364, 365 in leap years).
1183 @end deffn
1184 @deffn {Scheme Procedure} tm:isdst tm
1185 @deffnx {Scheme Procedure} set-tm:isdst tm val
1186 Daylight saving indicator (0 for ``no'', greater than 0 for ``yes'', less than
1187 0 for ``unknown'').
1188 @end deffn
1189 @deffn {Scheme Procedure} tm:gmtoff tm
1190 @deffnx {Scheme Procedure} set-tm:gmtoff tm val
1191 Time zone offset in seconds west of @acronym{UTC} (-46800 to 43200).
1192 For example on East coast USA (zone @samp{EST+5}) this would be 18000
1193 (ie.@: @m{5\times60\times60,5*60*60}) in winter, or 14400
1194 (ie.@: @m{4\times60\times60,4*60*60}) during daylight savings.
1195
1196 Note @code{tm:gmtoff} is not the same as @code{tm_gmtoff} in the C
1197 @code{tm} structure. @code{tm_gmtoff} is seconds east and hence the
1198 negative of the value here.
1199 @end deffn
1200 @deffn {Scheme Procedure} tm:zone tm
1201 @deffnx {Scheme Procedure} set-tm:zone tm val
1202 Time zone label (a string), not necessarily unique.
1203 @end deffn
1204 @sp 1
1205
1206 @deffn {Scheme Procedure} localtime time [zone]
1207 @deffnx {C Function} scm_localtime (time, zone)
1208 @cindex local time
1209 Return an object representing the broken down components of
1210 @var{time}, an integer like the one returned by
1211 @code{current-time}. The time zone for the calculation is
1212 optionally specified by @var{zone} (a string), otherwise the
1213 @env{TZ} environment variable or the system default is used.
1214 @end deffn
1215
1216 @deffn {Scheme Procedure} gmtime time
1217 @deffnx {C Function} scm_gmtime (time)
1218 Return an object representing the broken down components of
1219 @var{time}, an integer like the one returned by
1220 @code{current-time}. The values are calculated for @acronym{UTC}.
1221 @end deffn
1222
1223 @deffn {Scheme Procedure} mktime sbd-time [zone]
1224 @deffnx {C Function} scm_mktime (sbd_time, zone)
1225 For a broken down time object @var{sbd-time}, return a pair the
1226 @code{car} of which is an integer time like @code{current-time}, and
1227 the @code{cdr} of which is a new broken down time with normalized
1228 fields.
1229
1230 @var{zone} is a timezone string, or the default is the @env{TZ}
1231 environment variable or the system default (@pxref{TZ Variable,,
1232 Specifying the Time Zone with @env{TZ}, libc, GNU C Library Reference
1233 Manual}). @var{sbd-time} is taken to be in that @var{zone}.
1234
1235 The following fields of @var{sbd-time} are used: @code{tm:year},
1236 @code{tm:mon}, @code{tm:mday}, @code{tm:hour}, @code{tm:min},
1237 @code{tm:sec}, @code{tm:isdst}. The values can be outside their usual
1238 ranges. For example @code{tm:hour} normally goes up to 23, but a
1239 value say 33 would mean 9 the following day.
1240
1241 @code{tm:isdst} in @var{sbd-time} says whether the time given is with
1242 daylight savings or not. This is ignored if @var{zone} doesn't have
1243 any daylight savings adjustment amount.
1244
1245 The broken down time in the return normalizes the values of
1246 @var{sbd-time} by bringing them into their usual ranges, and using the
1247 actual daylight savings rule for that time in @var{zone} (which may
1248 differ from what @var{sbd-time} had). The easiest way to think of
1249 this is that @var{sbd-time} plus @var{zone} converts to the integer
1250 UTC time, then a @code{localtime} is applied to get the normal
1251 presentation of that time, in @var{zone}.
1252 @end deffn
1253
1254 @deffn {Scheme Procedure} tzset
1255 @deffnx {C Function} scm_tzset ()
1256 Initialize the timezone from the @env{TZ} environment variable
1257 or the system default. It's not usually necessary to call this procedure
1258 since it's done automatically by other procedures that depend on the
1259 timezone.
1260 @end deffn
1261
1262 @deffn {Scheme Procedure} strftime format tm
1263 @deffnx {C Function} scm_strftime (format, tm)
1264 @cindex time formatting
1265 Return a string which is broken-down time structure @var{tm} formatted
1266 according to the given @var{format} string.
1267
1268 @var{format} contains field specifications introduced by a @samp{%}
1269 character. See @ref{Formatting Calendar Time,,, libc, The GNU C
1270 Library Reference Manual}, or @samp{man 3 strftime}, for the available
1271 formatting.
1272
1273 @lisp
1274 (strftime "%c" (localtime (current-time)))
1275 @result{} "Mon Mar 11 20:17:43 2002"
1276 @end lisp
1277
1278 If @code{setlocale} has been called (@pxref{Locales}), month and day
1279 names are from the current locale and in the locale character set.
1280 @end deffn
1281
1282 @deffn {Scheme Procedure} strptime format string
1283 @deffnx {C Function} scm_strptime (format, string)
1284 @cindex time parsing
1285 Performs the reverse action to @code{strftime}, parsing
1286 @var{string} according to the specification supplied in
1287 @var{format}. The interpretation of month and day names is
1288 dependent on the current locale. The value returned is a pair.
1289 The @acronym{CAR} has an object with time components
1290 in the form returned by @code{localtime} or @code{gmtime},
1291 but the time zone components
1292 are not usefully set.
1293 The @acronym{CDR} reports the number of characters from @var{string}
1294 which were used for the conversion.
1295 @end deffn
1296
1297 @defvar internal-time-units-per-second
1298 The value of this variable is the number of time units per second
1299 reported by the following procedures.
1300 @end defvar
1301
1302 @deffn {Scheme Procedure} times
1303 @deffnx {C Function} scm_times ()
1304 Return an object with information about real and processor
1305 time. The following procedures accept such an object as an
1306 argument and return a selected component:
1307
1308 @deffn {Scheme Procedure} tms:clock tms
1309 The current real time, expressed as time units relative to an
1310 arbitrary base.
1311 @end deffn
1312 @deffn {Scheme Procedure} tms:utime tms
1313 The CPU time units used by the calling process.
1314 @end deffn
1315 @deffn {Scheme Procedure} tms:stime tms
1316 The CPU time units used by the system on behalf of the calling
1317 process.
1318 @end deffn
1319 @deffn {Scheme Procedure} tms:cutime tms
1320 The CPU time units used by terminated child processes of the
1321 calling process, whose status has been collected (e.g., using
1322 @code{waitpid}).
1323 @end deffn
1324 @deffn {Scheme Procedure} tms:cstime tms
1325 Similarly, the CPU times units used by the system on behalf of
1326 terminated child processes.
1327 @end deffn
1328 @end deffn
1329
1330 @deffn {Scheme Procedure} get-internal-real-time
1331 @deffnx {C Function} scm_get_internal_real_time ()
1332 Return the number of time units since the interpreter was
1333 started.
1334 @end deffn
1335
1336 @deffn {Scheme Procedure} get-internal-run-time
1337 @deffnx {C Function} scm_get_internal_run_time ()
1338 Return the number of time units of processor time used by the
1339 interpreter. Both @emph{system} and @emph{user} time are
1340 included but subprocesses are not.
1341 @end deffn
1342
1343 @node Runtime Environment
1344 @subsection Runtime Environment
1345
1346 @deffn {Scheme Procedure} program-arguments
1347 @deffnx {Scheme Procedure} command-line
1348 @deffnx {Scheme Procedure} set-program-arguments
1349 @deffnx {C Function} scm_program_arguments ()
1350 @deffnx {C Function} scm_set_program_arguments_scm (lst)
1351 @cindex command line
1352 @cindex program arguments
1353 Get the command line arguments passed to Guile, or set new arguments.
1354
1355 The arguments are a list of strings, the first of which is the invoked
1356 program name. This is just @nicode{"guile"} (or the executable path)
1357 when run interactively, or it's the script name when running a script
1358 with @option{-s} (@pxref{Invoking Guile}).
1359
1360 @example
1361 guile -L /my/extra/dir -s foo.scm abc def
1362
1363 (program-arguments) @result{} ("foo.scm" "abc" "def")
1364 @end example
1365
1366 @code{set-program-arguments} allows a library module or similar to
1367 modify the arguments, for example to strip options it recognises,
1368 leaving the rest for the mainline.
1369
1370 The argument list is held in a fluid, which means it's separate for
1371 each thread. Neither the list nor the strings within it are copied at
1372 any point and normally should not be mutated.
1373
1374 The two names @code{program-arguments} and @code{command-line} are an
1375 historical accident, they both do exactly the same thing. The name
1376 @code{scm_set_program_arguments_scm} has an extra @code{_scm} on the
1377 end to avoid clashing with the C function below.
1378 @end deffn
1379
1380 @deftypefn {C Function} void scm_set_program_arguments (int argc, char **argv, char *first)
1381 @cindex command line
1382 @cindex program arguments
1383 Set the list of command line arguments for @code{program-arguments}
1384 and @code{command-line} above.
1385
1386 @var{argv} is an array of null-terminated strings, as in a C
1387 @code{main} function. @var{argc} is the number of strings in
1388 @var{argv}, or if it's negative then a @code{NULL} in @var{argv} marks
1389 its end.
1390
1391 @var{first} is an extra string put at the start of the arguments, or
1392 @code{NULL} for no such extra. This is a convenient way to pass the
1393 program name after advancing @var{argv} to strip option arguments.
1394 Eg.@:
1395
1396 @example
1397 @{
1398 char *progname = argv[0];
1399 for (argv++; argv[0] != NULL && argv[0][0] == '-'; argv++)
1400 @{
1401 /* munch option ... */
1402 @}
1403 /* remaining args for scheme level use */
1404 scm_set_program_arguments (-1, argv, progname);
1405 @}
1406 @end example
1407
1408 This sort of thing is often done at startup under
1409 @code{scm_boot_guile} with options handled at the C level removed.
1410 The given strings are all copied, so the C data is not accessed again
1411 once @code{scm_set_program_arguments} returns.
1412 @end deftypefn
1413
1414 @deffn {Scheme Procedure} getenv name
1415 @deffnx {C Function} scm_getenv (name)
1416 @cindex environment
1417 Looks up the string @var{name} in the current environment. The return
1418 value is @code{#f} unless a string of the form @code{NAME=VALUE} is
1419 found, in which case the string @code{VALUE} is returned.
1420 @end deffn
1421
1422 @deffn {Scheme Procedure} setenv name value
1423 Modifies the environment of the current process, which is
1424 also the default environment inherited by child processes.
1425
1426 If @var{value} is @code{#f}, then @var{name} is removed from the
1427 environment. Otherwise, the string @var{name}=@var{value} is added
1428 to the environment, replacing any existing string with name matching
1429 @var{name}.
1430
1431 The return value is unspecified.
1432 @end deffn
1433
1434 @deffn {Scheme Procedure} unsetenv name
1435 Remove variable @var{name} from the environment. The
1436 name can not contain a @samp{=} character.
1437 @end deffn
1438
1439 @deffn {Scheme Procedure} environ [env]
1440 @deffnx {C Function} scm_environ (env)
1441 If @var{env} is omitted, return the current environment (in the
1442 Unix sense) as a list of strings. Otherwise set the current
1443 environment, which is also the default environment for child
1444 processes, to the supplied list of strings. Each member of
1445 @var{env} should be of the form @var{name}=@var{value} and values of
1446 @var{name} should not be duplicated. If @var{env} is supplied
1447 then the return value is unspecified.
1448 @end deffn
1449
1450 @deffn {Scheme Procedure} putenv str
1451 @deffnx {C Function} scm_putenv (str)
1452 Modifies the environment of the current process, which is
1453 also the default environment inherited by child processes.
1454
1455 If @var{str} is of the form @code{NAME=VALUE} then it will be written
1456 directly into the environment, replacing any existing environment string
1457 with
1458 name matching @code{NAME}. If @var{str} does not contain an equal
1459 sign, then any existing string with name matching @var{str} will
1460 be removed.
1461
1462 The return value is unspecified.
1463 @end deffn
1464
1465
1466 @node Processes
1467 @subsection Processes
1468 @cindex processes
1469 @cindex child processes
1470
1471 @findex cd
1472 @deffn {Scheme Procedure} chdir str
1473 @deffnx {C Function} scm_chdir (str)
1474 @cindex current directory
1475 Change the current working directory to @var{str}.
1476 The return value is unspecified.
1477 @end deffn
1478
1479 @findex pwd
1480 @deffn {Scheme Procedure} getcwd
1481 @deffnx {C Function} scm_getcwd ()
1482 Return the name of the current working directory.
1483 @end deffn
1484
1485 @deffn {Scheme Procedure} umask [mode]
1486 @deffnx {C Function} scm_umask (mode)
1487 If @var{mode} is omitted, returns a decimal number representing the
1488 current file creation mask. Otherwise the file creation mask is set
1489 to @var{mode} and the previous value is returned. @xref{Setting
1490 Permissions,,Assigning File Permissions,libc,The GNU C Library
1491 Reference Manual}, for more on how to use umasks.
1492
1493 E.g., @code{(umask #o022)} sets the mask to octal 22/decimal 18.
1494 @end deffn
1495
1496 @deffn {Scheme Procedure} chroot path
1497 @deffnx {C Function} scm_chroot (path)
1498 Change the root directory to that specified in @var{path}.
1499 This directory will be used for path names beginning with
1500 @file{/}. The root directory is inherited by all children
1501 of the current process. Only the superuser may change the
1502 root directory.
1503 @end deffn
1504
1505 @deffn {Scheme Procedure} getpid
1506 @deffnx {C Function} scm_getpid ()
1507 Return an integer representing the current process ID.
1508 @end deffn
1509
1510 @deffn {Scheme Procedure} getgroups
1511 @deffnx {C Function} scm_getgroups ()
1512 Return a vector of integers representing the current
1513 supplementary group IDs.
1514 @end deffn
1515
1516 @deffn {Scheme Procedure} getppid
1517 @deffnx {C Function} scm_getppid ()
1518 Return an integer representing the process ID of the parent
1519 process.
1520 @end deffn
1521
1522 @deffn {Scheme Procedure} getuid
1523 @deffnx {C Function} scm_getuid ()
1524 Return an integer representing the current real user ID.
1525 @end deffn
1526
1527 @deffn {Scheme Procedure} getgid
1528 @deffnx {C Function} scm_getgid ()
1529 Return an integer representing the current real group ID.
1530 @end deffn
1531
1532 @deffn {Scheme Procedure} geteuid
1533 @deffnx {C Function} scm_geteuid ()
1534 Return an integer representing the current effective user ID.
1535 If the system does not support effective IDs, then the real ID
1536 is returned. @code{(provided? 'EIDs)} reports whether the
1537 system supports effective IDs.
1538 @end deffn
1539
1540 @deffn {Scheme Procedure} getegid
1541 @deffnx {C Function} scm_getegid ()
1542 Return an integer representing the current effective group 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.
1546 @end deffn
1547
1548 @deffn {Scheme Procedure} setgroups vec
1549 @deffnx {C Function} scm_setgroups (vec)
1550 Set the current set of supplementary group IDs to the integers in the
1551 given vector @var{vec}. The return value is unspecified.
1552
1553 Generally only the superuser can set the process group IDs
1554 (@pxref{Setting Groups, Setting the Group IDs,, libc, The GNU C
1555 Library Reference Manual}).
1556 @end deffn
1557
1558 @deffn {Scheme Procedure} setuid id
1559 @deffnx {C Function} scm_setuid (id)
1560 Sets both the real and effective user IDs to the integer @var{id}, provided
1561 the process has appropriate privileges.
1562 The return value is unspecified.
1563 @end deffn
1564
1565 @deffn {Scheme Procedure} setgid id
1566 @deffnx {C Function} scm_setgid (id)
1567 Sets both the real and effective group IDs to the integer @var{id}, provided
1568 the process has appropriate privileges.
1569 The return value is unspecified.
1570 @end deffn
1571
1572 @deffn {Scheme Procedure} seteuid id
1573 @deffnx {C Function} scm_seteuid (id)
1574 Sets the effective user ID to the integer @var{id}, provided the process
1575 has appropriate privileges. If effective IDs are not supported, the
1576 real ID is set instead---@code{(provided? 'EIDs)} reports whether the
1577 system supports effective IDs.
1578 The return value is unspecified.
1579 @end deffn
1580
1581 @deffn {Scheme Procedure} setegid id
1582 @deffnx {C Function} scm_setegid (id)
1583 Sets the effective group ID to the integer @var{id}, provided the process
1584 has appropriate privileges. If effective IDs are not supported, the
1585 real ID is set instead---@code{(provided? 'EIDs)} reports whether the
1586 system supports effective IDs.
1587 The return value is unspecified.
1588 @end deffn
1589
1590 @deffn {Scheme Procedure} getpgrp
1591 @deffnx {C Function} scm_getpgrp ()
1592 Return an integer representing the current process group ID.
1593 This is the @acronym{POSIX} definition, not @acronym{BSD}.
1594 @end deffn
1595
1596 @deffn {Scheme Procedure} setpgid pid pgid
1597 @deffnx {C Function} scm_setpgid (pid, pgid)
1598 Move the process @var{pid} into the process group @var{pgid}. @var{pid} or
1599 @var{pgid} must be integers: they can be zero to indicate the ID of the
1600 current process.
1601 Fails on systems that do not support job control.
1602 The return value is unspecified.
1603 @end deffn
1604
1605 @deffn {Scheme Procedure} setsid
1606 @deffnx {C Function} scm_setsid ()
1607 Creates a new session. The current process becomes the session leader
1608 and is put in a new process group. The process will be detached
1609 from its controlling terminal if it has one.
1610 The return value is an integer representing the new process group ID.
1611 @end deffn
1612
1613 @deffn {Scheme Procedure} getsid pid
1614 @deffnx {C Function} scm_getsid (pid)
1615 Returns the session ID of process @var{pid}. (The session
1616 ID of a process is the process group ID of its session leader.)
1617 @end deffn
1618
1619 @deffn {Scheme Procedure} waitpid pid [options]
1620 @deffnx {C Function} scm_waitpid (pid, options)
1621 This procedure collects status information from a child process which
1622 has terminated or (optionally) stopped. Normally it will
1623 suspend the calling process until this can be done. If more than one
1624 child process is eligible then one will be chosen by the operating system.
1625
1626 The value of @var{pid} determines the behaviour:
1627
1628 @table @asis
1629 @item @var{pid} greater than 0
1630 Request status information from the specified child process.
1631 @item @var{pid} equal to -1 or @code{WAIT_ANY}
1632 @vindex WAIT_ANY
1633 Request status information for any child process.
1634 @item @var{pid} equal to 0 or @code{WAIT_MYPGRP}
1635 @vindex WAIT_MYPGRP
1636 Request status information for any child process in the current process
1637 group.
1638 @item @var{pid} less than -1
1639 Request status information for any child process whose process group ID
1640 is @minus{}@var{pid}.
1641 @end table
1642
1643 The @var{options} argument, if supplied, should be the bitwise OR of the
1644 values of zero or more of the following variables:
1645
1646 @defvar WNOHANG
1647 Return immediately even if there are no child processes to be collected.
1648 @end defvar
1649
1650 @defvar WUNTRACED
1651 Report status information for stopped processes as well as terminated
1652 processes.
1653 @end defvar
1654
1655 The return value is a pair containing:
1656
1657 @enumerate
1658 @item
1659 The process ID of the child process, or 0 if @code{WNOHANG} was
1660 specified and no process was collected.
1661 @item
1662 The integer status value.
1663 @end enumerate
1664 @end deffn
1665
1666 The following three
1667 functions can be used to decode the process status code returned
1668 by @code{waitpid}.
1669
1670 @deffn {Scheme Procedure} status:exit-val status
1671 @deffnx {C Function} scm_status_exit_val (status)
1672 Return the exit status value, as would be set if a process
1673 ended normally through a call to @code{exit} or @code{_exit},
1674 if any, otherwise @code{#f}.
1675 @end deffn
1676
1677 @deffn {Scheme Procedure} status:term-sig status
1678 @deffnx {C Function} scm_status_term_sig (status)
1679 Return the signal number which terminated the process, if any,
1680 otherwise @code{#f}.
1681 @end deffn
1682
1683 @deffn {Scheme Procedure} status:stop-sig status
1684 @deffnx {C Function} scm_status_stop_sig (status)
1685 Return the signal number which stopped the process, if any,
1686 otherwise @code{#f}.
1687 @end deffn
1688
1689 @deffn {Scheme Procedure} system [cmd]
1690 @deffnx {C Function} scm_system (cmd)
1691 Execute @var{cmd} using the operating system's ``command
1692 processor''. Under Unix this is usually the default shell
1693 @code{sh}. The value returned is @var{cmd}'s exit status as
1694 returned by @code{waitpid}, which can be interpreted using the
1695 functions above.
1696
1697 If @code{system} is called without arguments, return a boolean
1698 indicating whether the command processor is available.
1699 @end deffn
1700
1701 @deffn {Scheme Procedure} system* arg1 arg2 @dots{}
1702 @deffnx {C Function} scm_system_star (args)
1703 Execute the command indicated by @var{arg1} @var{arg2} @enddots{}. The
1704 first element must be a string indicating the command to be executed,
1705 and the remaining items must be strings representing each of the
1706 arguments to that command.
1707
1708 This function returns the exit status of the command as provided by
1709 @code{waitpid}. This value can be handled with @code{status:exit-val}
1710 and the related functions.
1711
1712 @code{system*} is similar to @code{system}, but accepts only one
1713 string per-argument, and performs no shell interpretation. The
1714 command is executed using fork and execlp. Accordingly this function
1715 may be safer than @code{system} in situations where shell
1716 interpretation is not required.
1717
1718 Example: (system* "echo" "foo" "bar")
1719 @end deffn
1720
1721 @deffn {Scheme Procedure} primitive-exit [status]
1722 @deffnx {Scheme Procedure} primitive-_exit [status]
1723 @deffnx {C Function} scm_primitive_exit (status)
1724 @deffnx {C Function} scm_primitive__exit (status)
1725 Terminate the current process without unwinding the Scheme stack. The
1726 exit status is @var{status} if supplied, otherwise zero.
1727
1728 @code{primitive-exit} uses the C @code{exit} function and hence runs
1729 usual C level cleanups (flush output streams, call @code{atexit}
1730 functions, etc, see @ref{Normal Termination,,, libc, The GNU C Library
1731 Reference Manual})).
1732
1733 @code{primitive-_exit} is the @code{_exit} system call
1734 (@pxref{Termination Internals,,, libc, The GNU C Library Reference
1735 Manual}). This terminates the program immediately, with neither
1736 Scheme-level nor C-level cleanups.
1737
1738 The typical use for @code{primitive-_exit} is from a child process
1739 created with @code{primitive-fork}. For example in a Gdk program the
1740 child process inherits the X server connection and a C-level
1741 @code{atexit} cleanup which will close that connection. But closing
1742 in the child would upset the protocol in the parent, so
1743 @code{primitive-_exit} should be used to exit without that.
1744 @end deffn
1745
1746 @deffn {Scheme Procedure} execl filename arg @dots{}
1747 @deffnx {C Function} scm_execl (filename, args)
1748 Executes the file named by @var{filename} as a new process image.
1749 The remaining arguments are supplied to the process; from a C program
1750 they are accessible as the @code{argv} argument to @code{main}.
1751 Conventionally the first @var{arg} is the same as @var{filename}.
1752 All arguments must be strings.
1753
1754 If @var{arg} is missing, @var{filename} is executed with a null
1755 argument list, which may have system-dependent side-effects.
1756
1757 This procedure is currently implemented using the @code{execv} system
1758 call, but we call it @code{execl} because of its Scheme calling interface.
1759 @end deffn
1760
1761 @deffn {Scheme Procedure} execlp filename arg @dots{}
1762 @deffnx {C Function} scm_execlp (filename, args)
1763 Similar to @code{execl}, however if
1764 @var{filename} does not contain a slash
1765 then the file to execute will be located by searching the
1766 directories listed in the @code{PATH} environment variable.
1767
1768 This procedure is currently implemented using the @code{execvp} system
1769 call, but we call it @code{execlp} because of its Scheme calling interface.
1770 @end deffn
1771
1772 @deffn {Scheme Procedure} execle filename env arg @dots{}
1773 @deffnx {C Function} scm_execle (filename, env, args)
1774 Similar to @code{execl}, but the environment of the new process is
1775 specified by @var{env}, which must be a list of strings as returned by the
1776 @code{environ} procedure.
1777
1778 This procedure is currently implemented using the @code{execve} system
1779 call, but we call it @code{execle} because of its Scheme calling interface.
1780 @end deffn
1781
1782 @deffn {Scheme Procedure} primitive-fork
1783 @deffnx {C Function} scm_fork ()
1784 Creates a new ``child'' process by duplicating the current ``parent'' process.
1785 In the child the return value is 0. In the parent the return value is
1786 the integer process ID of the child.
1787
1788 Note that it is unsafe to fork a process that has multiple threads
1789 running, as only the thread that calls @code{primitive-fork} will
1790 persist in the child. Any resources that other threads held, such as
1791 locked mutexes or open file descriptors, are lost. Indeed, @acronym{POSIX}
1792 specifies that only async-signal-safe procedures are safe to call after
1793 a multithreaded fork, which is a very limited set. Guile issues a
1794 warning if it detects a fork from a multi-threaded program.
1795
1796 If you are going to @code{exec} soon after forking, the procedures in
1797 @code{(ice-9 popen)} may be useful to you, as they fork and exec within
1798 an async-signal-safe function carefully written to ensure robust program
1799 behavior, even in the presence of threads. @xref{Pipes}, for more.
1800
1801 This procedure has been renamed from @code{fork} to avoid a naming conflict
1802 with the scsh fork.
1803 @end deffn
1804
1805 @deffn {Scheme Procedure} nice incr
1806 @deffnx {C Function} scm_nice (incr)
1807 @cindex process priority
1808 Increment the priority of the current process by @var{incr}. A higher
1809 priority value means that the process runs less often.
1810 The return value is unspecified.
1811 @end deffn
1812
1813 @deffn {Scheme Procedure} setpriority which who prio
1814 @deffnx {C Function} scm_setpriority (which, who, prio)
1815 @vindex PRIO_PROCESS
1816 @vindex PRIO_PGRP
1817 @vindex PRIO_USER
1818 Set the scheduling priority of the process, process group
1819 or user, as indicated by @var{which} and @var{who}. @var{which}
1820 is one of the variables @code{PRIO_PROCESS}, @code{PRIO_PGRP}
1821 or @code{PRIO_USER}, and @var{who} is interpreted relative to
1822 @var{which} (a process identifier for @code{PRIO_PROCESS},
1823 process group identifier for @code{PRIO_PGRP}, and a user
1824 identifier for @code{PRIO_USER}. A zero value of @var{who}
1825 denotes the current process, process group, or user.
1826 @var{prio} is a value in the range [@minus{}20,20]. The default
1827 priority is 0; lower priorities (in numerical terms) cause more
1828 favorable scheduling. Sets the priority of all of the specified
1829 processes. Only the super-user may lower priorities. The return
1830 value is not specified.
1831 @end deffn
1832
1833 @deffn {Scheme Procedure} getpriority which who
1834 @deffnx {C Function} scm_getpriority (which, who)
1835 @vindex PRIO_PROCESS
1836 @vindex PRIO_PGRP
1837 @vindex PRIO_USER
1838 Return the scheduling priority of the process, process group
1839 or user, as indicated by @var{which} and @var{who}. @var{which}
1840 is one of the variables @code{PRIO_PROCESS}, @code{PRIO_PGRP}
1841 or @code{PRIO_USER}, and @var{who} should be interpreted depending on
1842 @var{which} (a process identifier for @code{PRIO_PROCESS},
1843 process group identifier for @code{PRIO_PGRP}, and a user
1844 identifier for @code{PRIO_USER}). A zero value of @var{who}
1845 denotes the current process, process group, or user. Return
1846 the highest priority (lowest numerical value) of any of the
1847 specified processes.
1848 @end deffn
1849
1850 @cindex affinity, CPU
1851
1852 @deffn {Scheme Procedure} getaffinity pid
1853 @deffnx {C Function} scm_getaffinity (pid)
1854 Return a bitvector representing the CPU affinity mask for
1855 process @var{pid}. Each CPU the process has affinity with
1856 has its corresponding bit set in the returned bitvector.
1857 The number of bits set is a good estimate of how many CPUs
1858 Guile can use without stepping on other processes' toes.
1859
1860 Currently this procedure is only defined on GNU variants
1861 (@pxref{CPU Affinity, @code{sched_getaffinity},, libc, The
1862 GNU C Library Reference Manual}).
1863 @end deffn
1864
1865 @deffn {Scheme Procedure} setaffinity pid mask
1866 @deffnx {C Function} scm_setaffinity (pid, mask)
1867 Install the CPU affinity mask @var{mask}, a bitvector, for
1868 the process or thread with ID @var{pid}. The return value
1869 is unspecified.
1870
1871 Currently this procedure is only defined on GNU variants
1872 (@pxref{CPU Affinity, @code{sched_setaffinity},, libc, The
1873 GNU C Library Reference Manual}).
1874 @end deffn
1875
1876 @deffn {Scheme Procedure} total-processor-count
1877 @deffnx {C Function} scm_total_processor_count ()
1878 Return the total number of processors of the machine, which
1879 is guaranteed to be at least 1. A ``processor'' here is a
1880 thread execution unit, which can be either:
1881
1882 @itemize
1883 @item an execution core in a (possibly multi-core) chip, in a
1884 (possibly multi- chip) module, in a single computer, or
1885 @item a thread execution unit inside a core in the case of
1886 @dfn{hyper-threaded} CPUs.
1887 @end itemize
1888
1889 Which of the two definitions is used, is unspecified.
1890 @end deffn
1891
1892 @deffn {Scheme Procedure} current-processor-count
1893 @deffnx {C Function} scm_current_processor_count ()
1894 Like @code{total-processor-count}, but return the number of
1895 processors available to the current process. See
1896 @code{setaffinity} and @code{getaffinity} for more
1897 information.
1898 @end deffn
1899
1900
1901 @node Signals
1902 @subsection Signals
1903 @cindex signal
1904
1905 The following procedures raise, handle and wait for signals.
1906
1907 Scheme code signal handlers are run via a system async (@pxref{System
1908 asyncs}), so they're called in the handler's thread at the next safe
1909 opportunity. Generally this is after any currently executing
1910 primitive procedure finishes (which could be a long time for
1911 primitives that wait for an external event).
1912
1913 @deffn {Scheme Procedure} kill pid sig
1914 @deffnx {C Function} scm_kill (pid, sig)
1915 Sends a signal to the specified process or group of processes.
1916
1917 @var{pid} specifies the processes to which the signal is sent:
1918
1919 @table @asis
1920 @item @var{pid} greater than 0
1921 The process whose identifier is @var{pid}.
1922 @item @var{pid} equal to 0
1923 All processes in the current process group.
1924 @item @var{pid} less than -1
1925 The process group whose identifier is -@var{pid}
1926 @item @var{pid} equal to -1
1927 If the process is privileged, all processes except for some special
1928 system processes. Otherwise, all processes with the current effective
1929 user ID.
1930 @end table
1931
1932 @var{sig} should be specified using a variable corresponding to
1933 the Unix symbolic name, e.g.,
1934
1935 @defvar SIGHUP
1936 Hang-up signal.
1937 @end defvar
1938
1939 @defvar SIGINT
1940 Interrupt signal.
1941 @end defvar
1942
1943 A full list of signals on the GNU system may be found in @ref{Standard
1944 Signals,,,libc,The GNU C Library Reference Manual}.
1945 @end deffn
1946
1947 @deffn {Scheme Procedure} raise sig
1948 @deffnx {C Function} scm_raise (sig)
1949 Sends a specified signal @var{sig} to the current process, where
1950 @var{sig} is as described for the @code{kill} procedure.
1951 @end deffn
1952
1953 @deffn {Scheme Procedure} sigaction signum [handler [flags [thread]]]
1954 @deffnx {C Function} scm_sigaction (signum, handler, flags)
1955 @deffnx {C Function} scm_sigaction_for_thread (signum, handler, flags, thread)
1956 Install or report the signal handler for a specified signal.
1957
1958 @var{signum} is the signal number, which can be specified using the value
1959 of variables such as @code{SIGINT}.
1960
1961 If @var{handler} is omitted, @code{sigaction} returns a pair: the
1962 @acronym{CAR} is the current signal hander, which will be either an
1963 integer with the value @code{SIG_DFL} (default action) or
1964 @code{SIG_IGN} (ignore), or the Scheme procedure which handles the
1965 signal, or @code{#f} if a non-Scheme procedure handles the signal.
1966 The @acronym{CDR} contains the current @code{sigaction} flags for the
1967 handler.
1968
1969 If @var{handler} is provided, it is installed as the new handler for
1970 @var{signum}. @var{handler} can be a Scheme procedure taking one
1971 argument, or the value of @code{SIG_DFL} (default action) or
1972 @code{SIG_IGN} (ignore), or @code{#f} to restore whatever signal handler
1973 was installed before @code{sigaction} was first used. When a scheme
1974 procedure has been specified, that procedure will run in the given
1975 @var{thread}. When no thread has been given, the thread that made this
1976 call to @code{sigaction} is used.
1977
1978 @var{flags} is a @code{logior} (@pxref{Bitwise Operations}) of the
1979 following (where provided by the system), or @code{0} for none.
1980
1981 @defvar SA_NOCLDSTOP
1982 By default, @code{SIGCHLD} is signalled when a child process stops
1983 (ie.@: receives @code{SIGSTOP}), and when a child process terminates.
1984 With the @code{SA_NOCLDSTOP} flag, @code{SIGCHLD} is only signalled
1985 for termination, not stopping.
1986
1987 @code{SA_NOCLDSTOP} has no effect on signals other than
1988 @code{SIGCHLD}.
1989 @end defvar
1990
1991 @defvar SA_RESTART
1992 If a signal occurs while in a system call, deliver the signal then
1993 restart the system call (as opposed to returning an @code{EINTR} error
1994 from that call).
1995 @end defvar
1996
1997 The return value is a pair with information about the old handler as
1998 described above.
1999
2000 This interface does not provide access to the ``signal blocking''
2001 facility. Maybe this is not needed, since the thread support may
2002 provide solutions to the problem of consistent access to data
2003 structures.
2004 @end deffn
2005
2006 @deffn {Scheme Procedure} restore-signals
2007 @deffnx {C Function} scm_restore_signals ()
2008 Return all signal handlers to the values they had before any call to
2009 @code{sigaction} was made. The return value is unspecified.
2010 @end deffn
2011
2012 @deffn {Scheme Procedure} alarm i
2013 @deffnx {C Function} scm_alarm (i)
2014 Set a timer to raise a @code{SIGALRM} signal after the specified
2015 number of seconds (an integer). It's advisable to install a signal
2016 handler for
2017 @code{SIGALRM} beforehand, since the default action is to terminate
2018 the process.
2019
2020 The return value indicates the time remaining for the previous alarm,
2021 if any. The new value replaces the previous alarm. If there was
2022 no previous alarm, the return value is zero.
2023 @end deffn
2024
2025 @deffn {Scheme Procedure} pause
2026 @deffnx {C Function} scm_pause ()
2027 Pause the current process (thread?) until a signal arrives whose
2028 action is to either terminate the current process or invoke a
2029 handler procedure. The return value is unspecified.
2030 @end deffn
2031
2032 @deffn {Scheme Procedure} sleep secs
2033 @deffnx {Scheme Procedure} usleep usecs
2034 @deffnx {C Function} scm_sleep (secs)
2035 @deffnx {C Function} scm_usleep (usecs)
2036 Wait the given period @var{secs} seconds or @var{usecs} microseconds
2037 (both integers). If a signal arrives the wait stops and the return
2038 value is the time remaining, in seconds or microseconds respectively.
2039 If the period elapses with no signal the return is zero.
2040
2041 On most systems the process scheduler is not microsecond accurate and
2042 the actual period slept by @code{usleep} might be rounded to a system
2043 clock tick boundary, which might be 10 milliseconds for instance.
2044
2045 See @code{scm_std_sleep} and @code{scm_std_usleep} for equivalents at
2046 the C level (@pxref{Blocking}).
2047 @end deffn
2048
2049 @deffn {Scheme Procedure} getitimer which_timer
2050 @deffnx {Scheme Procedure} setitimer which_timer interval_seconds interval_microseconds periodic_seconds periodic_microseconds
2051 @deffnx {C Function} scm_getitimer (which_timer)
2052 @deffnx {C Function} scm_setitimer (which_timer, interval_seconds, interval_microseconds, periodic_seconds, periodic_microseconds)
2053 Get or set the periods programmed in certain system timers. These
2054 timers have a current interval value which counts down and on reaching
2055 zero raises a signal. An optional periodic value can be set to
2056 restart from there each time, for periodic operation.
2057 @var{which_timer} is one of the following values
2058
2059 @defvar ITIMER_REAL
2060 A real-time timer, counting down elapsed real time. At zero it raises
2061 @code{SIGALRM}. This is like @code{alarm} above, but with a higher
2062 resolution period.
2063 @end defvar
2064
2065 @defvar ITIMER_VIRTUAL
2066 A virtual-time timer, counting down while the current process is
2067 actually using CPU. At zero it raises @code{SIGVTALRM}.
2068 @end defvar
2069
2070 @defvar ITIMER_PROF
2071 A profiling timer, counting down while the process is running (like
2072 @code{ITIMER_VIRTUAL}) and also while system calls are running on the
2073 process's behalf. At zero it raises a @code{SIGPROF}.
2074
2075 This timer is intended for profiling where a program is spending its
2076 time (by looking where it is when the timer goes off).
2077 @end defvar
2078
2079 @code{getitimer} returns the current timer value and its programmed
2080 restart value, as a list containing two pairs. Each pair is a time in
2081 seconds and microseconds: @code{((@var{interval_secs}
2082 . @var{interval_usecs}) (@var{periodic_secs}
2083 . @var{periodic_usecs}))}.
2084
2085 @code{setitimer} sets the timer values similarly, in seconds and
2086 microseconds (which must be integers). The periodic value can be zero
2087 to have the timer run down just once. The return value is the timer's
2088 previous setting, in the same form as @code{getitimer} returns.
2089
2090 @example
2091 (setitimer ITIMER_REAL
2092 5 500000 ;; first SIGALRM in 5.5 seconds time
2093 2 0) ;; then repeat every 2 seconds
2094 @end example
2095
2096 Although the timers are programmed in microseconds, the actual
2097 accuracy might not be that high.
2098 @end deffn
2099
2100
2101 @node Terminals and Ptys
2102 @subsection Terminals and Ptys
2103
2104 @deffn {Scheme Procedure} isatty? port
2105 @deffnx {C Function} scm_isatty_p (port)
2106 @cindex terminal
2107 Return @code{#t} if @var{port} is using a serial non--file
2108 device, otherwise @code{#f}.
2109 @end deffn
2110
2111 @deffn {Scheme Procedure} ttyname port
2112 @deffnx {C Function} scm_ttyname (port)
2113 @cindex terminal
2114 Return a string with the name of the serial terminal device
2115 underlying @var{port}.
2116 @end deffn
2117
2118 @deffn {Scheme Procedure} ctermid
2119 @deffnx {C Function} scm_ctermid ()
2120 @cindex terminal
2121 Return a string containing the file name of the controlling
2122 terminal for the current process.
2123 @end deffn
2124
2125 @deffn {Scheme Procedure} tcgetpgrp port
2126 @deffnx {C Function} scm_tcgetpgrp (port)
2127 @cindex process group
2128 Return the process group ID of the foreground process group
2129 associated with the terminal open on the file descriptor
2130 underlying @var{port}.
2131
2132 If there is no foreground process group, the return value is a
2133 number greater than 1 that does not match the process group ID
2134 of any existing process group. This can happen if all of the
2135 processes in the job that was formerly the foreground job have
2136 terminated, and no other job has yet been moved into the
2137 foreground.
2138 @end deffn
2139
2140 @deffn {Scheme Procedure} tcsetpgrp port pgid
2141 @deffnx {C Function} scm_tcsetpgrp (port, pgid)
2142 @cindex process group
2143 Set the foreground process group ID for the terminal used by the file
2144 descriptor underlying @var{port} to the integer @var{pgid}.
2145 The calling process
2146 must be a member of the same session as @var{pgid} and must have the same
2147 controlling terminal. The return value is unspecified.
2148 @end deffn
2149
2150 @node Pipes
2151 @subsection Pipes
2152 @cindex pipe
2153
2154 The following procedures are similar to the @code{popen} and
2155 @code{pclose} system routines. The code is in a separate ``popen''
2156 module:
2157
2158 @lisp
2159 (use-modules (ice-9 popen))
2160 @end lisp
2161
2162 @findex popen
2163 @deffn {Scheme Procedure} open-pipe command mode
2164 @deffnx {Scheme Procedure} open-pipe* mode prog [args...]
2165 Execute a command in a subprocess, with a pipe to it or from it, or
2166 with pipes in both directions.
2167
2168 @code{open-pipe} runs the shell @var{command} using @samp{/bin/sh -c}.
2169 @code{open-pipe*} executes @var{prog} directly, with the optional
2170 @var{args} arguments (all strings).
2171
2172 @var{mode} should be one of the following values. @code{OPEN_READ} is
2173 an input pipe, ie.@: to read from the subprocess. @code{OPEN_WRITE}
2174 is an output pipe, ie.@: to write to it.
2175
2176 @defvar OPEN_READ
2177 @defvarx OPEN_WRITE
2178 @defvarx OPEN_BOTH
2179 @end defvar
2180
2181 For an input pipe, the child's standard output is the pipe and
2182 standard input is inherited from @code{current-input-port}. For an
2183 output pipe, the child's standard input is the pipe and standard
2184 output is inherited from @code{current-output-port}. In all cases
2185 cases the child's standard error is inherited from
2186 @code{current-error-port} (@pxref{Default Ports}).
2187
2188 If those @code{current-X-ports} are not files of some kind, and hence
2189 don't have file descriptors for the child, then @file{/dev/null} is
2190 used instead.
2191
2192 Care should be taken with @code{OPEN_BOTH}, a deadlock will occur if
2193 both parent and child are writing, and waiting until the write
2194 completes before doing any reading. Each direction has
2195 @code{PIPE_BUF} bytes of buffering (@pxref{Ports and File
2196 Descriptors}), which will be enough for small writes, but not for say
2197 putting a big file through a filter.
2198 @end deffn
2199
2200 @deffn {Scheme Procedure} open-input-pipe command
2201 Equivalent to @code{open-pipe} with mode @code{OPEN_READ}.
2202
2203 @lisp
2204 (let* ((port (open-input-pipe "date --utc"))
2205 (str (read-line port)))
2206 (close-pipe port)
2207 str)
2208 @result{} "Mon Mar 11 20:10:44 UTC 2002"
2209 @end lisp
2210 @end deffn
2211
2212 @deffn {Scheme Procedure} open-output-pipe command
2213 Equivalent to @code{open-pipe} with mode @code{OPEN_WRITE}.
2214
2215 @lisp
2216 (let ((port (open-output-pipe "lpr")))
2217 (display "Something for the line printer.\n" port)
2218 (if (not (eqv? 0 (status:exit-val (close-pipe port))))
2219 (error "Cannot print")))
2220 @end lisp
2221 @end deffn
2222
2223 @deffn {Scheme Procedure} open-input-output-pipe command
2224 Equivalent to @code{open-pipe} with mode @code{OPEN_BOTH}.
2225 @end deffn
2226
2227 @findex pclose
2228 @deffn {Scheme Procedure} close-pipe port
2229 Close a pipe created by @code{open-pipe}, wait for the process to
2230 terminate, and return the wait status code. The status is as per
2231 @code{waitpid} and can be decoded with @code{status:exit-val} etc
2232 (@pxref{Processes})
2233 @end deffn
2234
2235 @sp 1
2236 @code{waitpid WAIT_ANY} should not be used when pipes are open, since
2237 it can reap a pipe's child process, causing an error from a subsequent
2238 @code{close-pipe}.
2239
2240 @code{close-port} (@pxref{Closing}) can close a pipe, but it doesn't
2241 reap the child process.
2242
2243 The garbage collector will close a pipe no longer in use, and reap the
2244 child process with @code{waitpid}. If the child hasn't yet terminated
2245 the garbage collector doesn't block, but instead checks again in the
2246 next GC.
2247
2248 Many systems have per-user and system-wide limits on the number of
2249 processes, and a system-wide limit on the number of pipes, so pipes
2250 should be closed explicitly when no longer needed, rather than letting
2251 the garbage collector pick them up at some later time.
2252
2253
2254 @node Networking
2255 @subsection Networking
2256 @cindex network
2257
2258 @menu
2259 * Network Address Conversion::
2260 * Network Databases::
2261 * Network Socket Address::
2262 * Network Sockets and Communication::
2263 * Internet Socket Examples::
2264 @end menu
2265
2266 @node Network Address Conversion
2267 @subsubsection Network Address Conversion
2268 @cindex network address
2269
2270 This section describes procedures which convert internet addresses
2271 between numeric and string formats.
2272
2273 @subsubheading IPv4 Address Conversion
2274 @cindex IPv4
2275
2276 An IPv4 Internet address is a 4-byte value, represented in Guile as an
2277 integer in host byte order, so that say ``0.0.0.1'' is 1, or
2278 ``1.0.0.0'' is 16777216.
2279
2280 Some underlying C functions use network byte order for addresses,
2281 Guile converts as necessary so that at the Scheme level its host byte
2282 order everywhere.
2283
2284 @defvar INADDR_ANY
2285 For a server, this can be used with @code{bind} (@pxref{Network
2286 Sockets and Communication}) to allow connections from any interface on
2287 the machine.
2288 @end defvar
2289
2290 @defvar INADDR_BROADCAST
2291 The broadcast address on the local network.
2292 @end defvar
2293
2294 @defvar INADDR_LOOPBACK
2295 The address of the local host using the loopback device, ie.@:
2296 @samp{127.0.0.1}.
2297 @end defvar
2298
2299 @c INADDR_NONE is defined in the code, but serves no purpose.
2300 @c inet_addr() returns it as an error indication, but that function
2301 @c isn't provided, for the good reason that inet_aton() does the same
2302 @c job and gives an unambiguous error indication. (INADDR_NONE is a
2303 @c valid 4-byte value, in glibc it's the same as INADDR_BROADCAST.)
2304 @c
2305 @c @defvar INADDR_NONE
2306 @c No address.
2307 @c @end defvar
2308
2309 @deffn {Scheme Procedure} inet-aton address
2310 @deffnx {C Function} scm_inet_aton (address)
2311 This function is deprecated in favor of @code{inet-pton}.
2312
2313 Convert an IPv4 Internet address from printable string
2314 (dotted decimal notation) to an integer. E.g.,
2315
2316 @lisp
2317 (inet-aton "127.0.0.1") @result{} 2130706433
2318 @end lisp
2319 @end deffn
2320
2321 @deffn {Scheme Procedure} inet-ntoa inetid
2322 @deffnx {C Function} scm_inet_ntoa (inetid)
2323 This function is deprecated in favor of @code{inet-ntop}.
2324
2325 Convert an IPv4 Internet address to a printable
2326 (dotted decimal notation) string. E.g.,
2327
2328 @lisp
2329 (inet-ntoa 2130706433) @result{} "127.0.0.1"
2330 @end lisp
2331 @end deffn
2332
2333 @deffn {Scheme Procedure} inet-netof address
2334 @deffnx {C Function} scm_inet_netof (address)
2335 Return the network number part of the given IPv4
2336 Internet address. E.g.,
2337
2338 @lisp
2339 (inet-netof 2130706433) @result{} 127
2340 @end lisp
2341 @end deffn
2342
2343 @deffn {Scheme Procedure} inet-lnaof address
2344 @deffnx {C Function} scm_lnaof (address)
2345 Return the local-address-with-network part of the given
2346 IPv4 Internet address, using the obsolete class A/B/C system.
2347 E.g.,
2348
2349 @lisp
2350 (inet-lnaof 2130706433) @result{} 1
2351 @end lisp
2352 @end deffn
2353
2354 @deffn {Scheme Procedure} inet-makeaddr net lna
2355 @deffnx {C Function} scm_inet_makeaddr (net, lna)
2356 Make an IPv4 Internet address by combining the network number
2357 @var{net} with the local-address-within-network number
2358 @var{lna}. E.g.,
2359
2360 @lisp
2361 (inet-makeaddr 127 1) @result{} 2130706433
2362 @end lisp
2363 @end deffn
2364
2365 @subsubheading IPv6 Address Conversion
2366 @cindex IPv6
2367
2368 An IPv6 Internet address is a 16-byte value, represented in Guile as
2369 an integer in host byte order, so that say ``::1'' is 1.
2370
2371 @deffn {Scheme Procedure} inet-ntop family address
2372 @deffnx {C Function} scm_inet_ntop (family, address)
2373 Convert a network address from an integer to a printable string.
2374 @var{family} can be @code{AF_INET} or @code{AF_INET6}. E.g.,
2375
2376 @lisp
2377 (inet-ntop AF_INET 2130706433) @result{} "127.0.0.1"
2378 (inet-ntop AF_INET6 (- (expt 2 128) 1))
2379 @result{} "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"
2380 @end lisp
2381 @end deffn
2382
2383 @deffn {Scheme Procedure} inet-pton family address
2384 @deffnx {C Function} scm_inet_pton (family, address)
2385 Convert a string containing a printable network address to an integer
2386 address. @var{family} can be @code{AF_INET} or @code{AF_INET6}.
2387 E.g.,
2388
2389 @lisp
2390 (inet-pton AF_INET "127.0.0.1") @result{} 2130706433
2391 (inet-pton AF_INET6 "::1") @result{} 1
2392 @end lisp
2393 @end deffn
2394
2395
2396 @node Network Databases
2397 @subsubsection Network Databases
2398 @cindex network database
2399
2400 This section describes procedures which query various network databases.
2401 Care should be taken when using the database routines since they are not
2402 reentrant.
2403
2404 @subsubheading @code{getaddrinfo}
2405
2406 @cindex @code{addrinfo} object type
2407 @cindex host name lookup
2408 @cindex service name lookup
2409
2410 The @code{getaddrinfo} procedure maps host and service names to socket addresses
2411 and associated information in a protocol-independent way.
2412
2413 @deffn {Scheme Procedure} getaddrinfo name service [hint_flags [hint_family [hint_socktype [hint_protocol]]]]
2414 @deffnx {C Function} scm_getaddrinfo (name, service, hint_flags, hint_family, hint_socktype, hint_protocol)
2415 Return a list of @code{addrinfo} structures containing
2416 a socket address and associated information for host @var{name}
2417 and/or @var{service} to be used in creating a socket with
2418 which to address the specified service.
2419
2420 @example
2421 (let* ((ai (car (getaddrinfo "www.gnu.org" "http")))
2422 (s (socket (addrinfo:fam ai) (addrinfo:socktype ai)
2423 (addrinfo:protocol ai))))
2424 (connect s (addrinfo:addr ai))
2425 s)
2426 @end example
2427
2428 When @var{service} is omitted or is @code{#f}, return
2429 network-level addresses for @var{name}. When @var{name}
2430 is @code{#f} @var{service} must be provided and service
2431 locations local to the caller are returned.
2432
2433 Additional hints can be provided. When specified,
2434 @var{hint_flags} should be a bitwise-or of zero or more
2435 constants among the following:
2436
2437 @table @code
2438 @item AI_PASSIVE
2439 Socket address is intended for @code{bind}.
2440
2441 @item AI_CANONNAME
2442 Request for canonical host name, available via
2443 @code{addrinfo:canonname}. This makes sense mainly when
2444 DNS lookups are involved.
2445
2446 @item AI_NUMERICHOST
2447 Specifies that @var{name} is a numeric host address string
2448 (e.g., @code{"127.0.0.1"}), meaning that name resolution
2449 will not be used.
2450
2451 @item AI_NUMERICSERV
2452 Likewise, specifies that @var{service} is a numeric port
2453 string (e.g., @code{"80"}).
2454
2455 @item AI_ADDRCONFIG
2456 Return only addresses configured on the local system It is
2457 highly recommended to provide this flag when the returned
2458 socket addresses are to be used to make connections;
2459 otherwise, some of the returned addresses could be unreachable
2460 or use a protocol that is not supported.
2461
2462 @item AI_V4MAPPED
2463 When looking up IPv6 addresses, return mapped IPv4 addresses if
2464 there is no IPv6 address available at all.
2465
2466 @item AI_ALL
2467 If this flag is set along with @code{AI_V4MAPPED} when looking up IPv6
2468 addresses, return all IPv6 addresses as well as all IPv4 addresses, the latter
2469 mapped to IPv6 format.
2470 @end table
2471
2472 When given, @var{hint_family} should specify the requested
2473 address family, e.g., @code{AF_INET6}. Similarly,
2474 @var{hint_socktype} should specify the requested socket type
2475 (e.g., @code{SOCK_DGRAM}), and @var{hint_protocol} should
2476 specify the requested protocol (its value is interpreted
2477 as in calls to @code{socket}).
2478
2479 On error, an exception with key @code{getaddrinfo-error} is
2480 thrown, with an error code (an integer) as its argument:
2481
2482 @example
2483 (catch 'getaddrinfo-error
2484 (lambda ()
2485 (getaddrinfo "www.gnu.org" "gopher"))
2486 (lambda (key errcode)
2487 (cond ((= errcode EAI_SERVICE)
2488 (display "doesn't know about Gopher!\n"))
2489 ((= errcode EAI_NONAME)
2490 (display "www.gnu.org not found\\n"))
2491 (else
2492 (format #t "something wrong: ~a\n"
2493 (gai-strerror errcode))))))
2494 @end example
2495
2496 Error codes are:
2497
2498 @table @code
2499 @item EAI_AGAIN
2500 The name or service could not be resolved at this time. Future
2501 attempts may succeed.
2502
2503 @item EAI_BADFLAGS
2504 @var{hint_flags} contains an invalid value.
2505
2506 @item EAI_FAIL
2507 A non-recoverable error occurred when attempting to
2508 resolve the name.
2509
2510 @item EAI_FAMILY
2511 @var{hint_family} was not recognized.
2512
2513 @item EAI_NONAME
2514 Either @var{name} does not resolve for the supplied parameters,
2515 or neither @var{name} nor @var{service} were supplied.
2516
2517 @item EAI_NODATA
2518 This non-POSIX error code can be returned on some systems (GNU
2519 and Darwin, at least), for example when @var{name} is known
2520 but requests that were made turned out no data. Error handling
2521 code should be prepared to handle it when it is defined.
2522
2523 @item EAI_SERVICE
2524 @var{service} was not recognized for the specified socket type.
2525
2526 @item EAI_SOCKTYPE
2527 @var{hint_socktype} was not recognized.
2528
2529 @item EAI_SYSTEM
2530 A system error occurred; the error code can be found in
2531 @code{errno}.
2532 @end table
2533
2534 Users are encouraged to read the
2535 @url{http://www.opengroup.org/onlinepubs/9699919799/functions/getaddrinfo.html,
2536 "POSIX specification} for more details.
2537 @end deffn
2538
2539 The following procedures take an @code{addrinfo} object as returned by
2540 @code{getaddrinfo}:
2541
2542 @deffn {Scheme Procedure} addrinfo:flags ai
2543 Return flags for @var{ai} as a bitwise or of @code{AI_} values (see above).
2544 @end deffn
2545
2546 @deffn {Scheme Procedure} addrinfo:fam ai
2547 Return the address family of @var{ai} (a @code{AF_} value).
2548 @end deffn
2549
2550 @deffn {Scheme Procedure} addrinfo:socktype ai
2551 Return the socket type for @var{ai} (a @code{SOCK_} value).
2552 @end deffn
2553
2554 @deffn {Scheme Procedure} addrinfo:protocol ai
2555 Return the protocol of @var{ai}.
2556 @end deffn
2557
2558 @deffn {Scheme Procedure} addrinfo:addr ai
2559 Return the socket address associated with @var{ai} as a @code{sockaddr}
2560 object (@pxref{Network Socket Address}).
2561 @end deffn
2562
2563 @deffn {Scheme Procedure} addrinfo:canonname ai
2564 Return a string for the canonical name associated with @var{ai} if
2565 the @code{AI_CANONNAME} flag was supplied.
2566 @end deffn
2567
2568 @subsubheading The Host Database
2569 @cindex @file{/etc/hosts}
2570 @cindex network database
2571
2572 A @dfn{host object} is a structure that represents what is known about a
2573 network host, and is the usual way of representing a system's network
2574 identity inside software.
2575
2576 The following functions accept a host object and return a selected
2577 component:
2578
2579 @deffn {Scheme Procedure} hostent:name host
2580 The ``official'' hostname for @var{host}.
2581 @end deffn
2582 @deffn {Scheme Procedure} hostent:aliases host
2583 A list of aliases for @var{host}.
2584 @end deffn
2585 @deffn {Scheme Procedure} hostent:addrtype host
2586 The host address type, one of the @code{AF} constants, such as
2587 @code{AF_INET} or @code{AF_INET6}.
2588 @end deffn
2589 @deffn {Scheme Procedure} hostent:length host
2590 The length of each address for @var{host}, in bytes.
2591 @end deffn
2592 @deffn {Scheme Procedure} hostent:addr-list host
2593 The list of network addresses associated with @var{host}. For
2594 @code{AF_INET} these are integer IPv4 address (@pxref{Network Address
2595 Conversion}).
2596 @end deffn
2597
2598 The following procedures can be used to search the host database. However,
2599 @code{getaddrinfo} should be preferred over them since it's more generic and
2600 thread-safe.
2601
2602 @deffn {Scheme Procedure} gethost [host]
2603 @deffnx {Scheme Procedure} gethostbyname hostname
2604 @deffnx {Scheme Procedure} gethostbyaddr address
2605 @deffnx {C Function} scm_gethost (host)
2606 Look up a host by name or address, returning a host object. The
2607 @code{gethost} procedure will accept either a string name or an integer
2608 address; if given no arguments, it behaves like @code{gethostent} (see
2609 below). If a name or address is supplied but the address can not be
2610 found, an error will be thrown to one of the keys:
2611 @code{host-not-found}, @code{try-again}, @code{no-recovery} or
2612 @code{no-data}, corresponding to the equivalent @code{h_error} values.
2613 Unusual conditions may result in errors thrown to the
2614 @code{system-error} or @code{misc_error} keys.
2615
2616 @lisp
2617 (gethost "www.gnu.org")
2618 @result{} #("www.gnu.org" () 2 4 (3353880842))
2619
2620 (gethostbyname "www.emacs.org")
2621 @result{} #("emacs.org" ("www.emacs.org") 2 4 (1073448978))
2622 @end lisp
2623 @end deffn
2624
2625 The following procedures may be used to step through the host
2626 database from beginning to end.
2627
2628 @deffn {Scheme Procedure} sethostent [stayopen]
2629 Initialize an internal stream from which host objects may be read. This
2630 procedure must be called before any calls to @code{gethostent}, and may
2631 also be called afterward to reset the host entry stream. If
2632 @var{stayopen} is supplied and is not @code{#f}, the database is not
2633 closed by subsequent @code{gethostbyname} or @code{gethostbyaddr} calls,
2634 possibly giving an efficiency gain.
2635 @end deffn
2636
2637 @deffn {Scheme Procedure} gethostent
2638 Return the next host object from the host database, or @code{#f} if
2639 there are no more hosts to be found (or an error has been encountered).
2640 This procedure may not be used before @code{sethostent} has been called.
2641 @end deffn
2642
2643 @deffn {Scheme Procedure} endhostent
2644 Close the stream used by @code{gethostent}. The return value is unspecified.
2645 @end deffn
2646
2647 @deffn {Scheme Procedure} sethost [stayopen]
2648 @deffnx {C Function} scm_sethost (stayopen)
2649 If @var{stayopen} is omitted, this is equivalent to @code{endhostent}.
2650 Otherwise it is equivalent to @code{sethostent stayopen}.
2651 @end deffn
2652
2653 @subsubheading The Network Database
2654 @cindex network database
2655
2656 The following functions accept an object representing a network
2657 and return a selected component:
2658
2659 @deffn {Scheme Procedure} netent:name net
2660 The ``official'' network name.
2661 @end deffn
2662 @deffn {Scheme Procedure} netent:aliases net
2663 A list of aliases for the network.
2664 @end deffn
2665 @deffn {Scheme Procedure} netent:addrtype net
2666 The type of the network number. Currently, this returns only
2667 @code{AF_INET}.
2668 @end deffn
2669 @deffn {Scheme Procedure} netent:net net
2670 The network number.
2671 @end deffn
2672
2673 The following procedures are used to search the network database:
2674
2675 @deffn {Scheme Procedure} getnet [net]
2676 @deffnx {Scheme Procedure} getnetbyname net-name
2677 @deffnx {Scheme Procedure} getnetbyaddr net-number
2678 @deffnx {C Function} scm_getnet (net)
2679 Look up a network by name or net number in the network database. The
2680 @var{net-name} argument must be a string, and the @var{net-number}
2681 argument must be an integer. @code{getnet} will accept either type of
2682 argument, behaving like @code{getnetent} (see below) if no arguments are
2683 given.
2684 @end deffn
2685
2686 The following procedures may be used to step through the network
2687 database from beginning to end.
2688
2689 @deffn {Scheme Procedure} setnetent [stayopen]
2690 Initialize an internal stream from which network objects may be read. This
2691 procedure must be called before any calls to @code{getnetent}, and may
2692 also be called afterward to reset the net entry stream. If
2693 @var{stayopen} is supplied and is not @code{#f}, the database is not
2694 closed by subsequent @code{getnetbyname} or @code{getnetbyaddr} calls,
2695 possibly giving an efficiency gain.
2696 @end deffn
2697
2698 @deffn {Scheme Procedure} getnetent
2699 Return the next entry from the network database.
2700 @end deffn
2701
2702 @deffn {Scheme Procedure} endnetent
2703 Close the stream used by @code{getnetent}. The return value is unspecified.
2704 @end deffn
2705
2706 @deffn {Scheme Procedure} setnet [stayopen]
2707 @deffnx {C Function} scm_setnet (stayopen)
2708 If @var{stayopen} is omitted, this is equivalent to @code{endnetent}.
2709 Otherwise it is equivalent to @code{setnetent stayopen}.
2710 @end deffn
2711
2712 @subsubheading The Protocol Database
2713 @cindex @file{/etc/protocols}
2714 @cindex protocols
2715 @cindex network protocols
2716
2717 The following functions accept an object representing a protocol
2718 and return a selected component:
2719
2720 @deffn {Scheme Procedure} protoent:name protocol
2721 The ``official'' protocol name.
2722 @end deffn
2723 @deffn {Scheme Procedure} protoent:aliases protocol
2724 A list of aliases for the protocol.
2725 @end deffn
2726 @deffn {Scheme Procedure} protoent:proto protocol
2727 The protocol number.
2728 @end deffn
2729
2730 The following procedures are used to search the protocol database:
2731
2732 @deffn {Scheme Procedure} getproto [protocol]
2733 @deffnx {Scheme Procedure} getprotobyname name
2734 @deffnx {Scheme Procedure} getprotobynumber number
2735 @deffnx {C Function} scm_getproto (protocol)
2736 Look up a network protocol by name or by number. @code{getprotobyname}
2737 takes a string argument, and @code{getprotobynumber} takes an integer
2738 argument. @code{getproto} will accept either type, behaving like
2739 @code{getprotoent} (see below) if no arguments are supplied.
2740 @end deffn
2741
2742 The following procedures may be used to step through the protocol
2743 database from beginning to end.
2744
2745 @deffn {Scheme Procedure} setprotoent [stayopen]
2746 Initialize an internal stream from which protocol objects may be read. This
2747 procedure must be called before any calls to @code{getprotoent}, and may
2748 also be called afterward to reset the protocol entry stream. If
2749 @var{stayopen} is supplied and is not @code{#f}, the database is not
2750 closed by subsequent @code{getprotobyname} or @code{getprotobynumber} calls,
2751 possibly giving an efficiency gain.
2752 @end deffn
2753
2754 @deffn {Scheme Procedure} getprotoent
2755 Return the next entry from the protocol database.
2756 @end deffn
2757
2758 @deffn {Scheme Procedure} endprotoent
2759 Close the stream used by @code{getprotoent}. The return value is unspecified.
2760 @end deffn
2761
2762 @deffn {Scheme Procedure} setproto [stayopen]
2763 @deffnx {C Function} scm_setproto (stayopen)
2764 If @var{stayopen} is omitted, this is equivalent to @code{endprotoent}.
2765 Otherwise it is equivalent to @code{setprotoent stayopen}.
2766 @end deffn
2767
2768 @subsubheading The Service Database
2769 @cindex @file{/etc/services}
2770 @cindex services
2771 @cindex network services
2772
2773 The following functions accept an object representing a service
2774 and return a selected component:
2775
2776 @deffn {Scheme Procedure} servent:name serv
2777 The ``official'' name of the network service.
2778 @end deffn
2779 @deffn {Scheme Procedure} servent:aliases serv
2780 A list of aliases for the network service.
2781 @end deffn
2782 @deffn {Scheme Procedure} servent:port serv
2783 The Internet port used by the service.
2784 @end deffn
2785 @deffn {Scheme Procedure} servent:proto serv
2786 The protocol used by the service. A service may be listed many times
2787 in the database under different protocol names.
2788 @end deffn
2789
2790 The following procedures are used to search the service database:
2791
2792 @deffn {Scheme Procedure} getserv [name [protocol]]
2793 @deffnx {Scheme Procedure} getservbyname name protocol
2794 @deffnx {Scheme Procedure} getservbyport port protocol
2795 @deffnx {C Function} scm_getserv (name, protocol)
2796 Look up a network service by name or by service number, and return a
2797 network service object. The @var{protocol} argument specifies the name
2798 of the desired protocol; if the protocol found in the network service
2799 database does not match this name, a system error is signalled.
2800
2801 The @code{getserv} procedure will take either a service name or number
2802 as its first argument; if given no arguments, it behaves like
2803 @code{getservent} (see below).
2804
2805 @lisp
2806 (getserv "imap" "tcp")
2807 @result{} #("imap2" ("imap") 143 "tcp")
2808
2809 (getservbyport 88 "udp")
2810 @result{} #("kerberos" ("kerberos5" "krb5") 88 "udp")
2811 @end lisp
2812 @end deffn
2813
2814 The following procedures may be used to step through the service
2815 database from beginning to end.
2816
2817 @deffn {Scheme Procedure} setservent [stayopen]
2818 Initialize an internal stream from which service objects may be read. This
2819 procedure must be called before any calls to @code{getservent}, and may
2820 also be called afterward to reset the service entry stream. If
2821 @var{stayopen} is supplied and is not @code{#f}, the database is not
2822 closed by subsequent @code{getservbyname} or @code{getservbyport} calls,
2823 possibly giving an efficiency gain.
2824 @end deffn
2825
2826 @deffn {Scheme Procedure} getservent
2827 Return the next entry from the services database.
2828 @end deffn
2829
2830 @deffn {Scheme Procedure} endservent
2831 Close the stream used by @code{getservent}. The return value is unspecified.
2832 @end deffn
2833
2834 @deffn {Scheme Procedure} setserv [stayopen]
2835 @deffnx {C Function} scm_setserv (stayopen)
2836 If @var{stayopen} is omitted, this is equivalent to @code{endservent}.
2837 Otherwise it is equivalent to @code{setservent stayopen}.
2838 @end deffn
2839
2840
2841 @node Network Socket Address
2842 @subsubsection Network Socket Address
2843 @cindex socket address
2844 @cindex network socket address
2845 @tpindex Socket address
2846
2847 A @dfn{socket address} object identifies a socket endpoint for
2848 communication. In the case of @code{AF_INET} for instance, the socket
2849 address object comprises the host address (or interface on the host)
2850 and a port number which specifies a particular open socket in a
2851 running client or server process. A socket address object can be
2852 created with,
2853
2854 @deffn {Scheme Procedure} make-socket-address AF_INET ipv4addr port
2855 @deffnx {Scheme Procedure} make-socket-address AF_INET6 ipv6addr port [flowinfo [scopeid]]
2856 @deffnx {Scheme Procedure} make-socket-address AF_UNIX path
2857 @deffnx {C Function} scm_make_socket_address (family, address, arglist)
2858 Return a new socket address object. The first argument is the address
2859 family, one of the @code{AF} constants, then the arguments vary
2860 according to the family.
2861
2862 For @code{AF_INET} the arguments are an IPv4 network address number
2863 (@pxref{Network Address Conversion}), and a port number.
2864
2865 For @code{AF_INET6} the arguments are an IPv6 network address number
2866 and a port number. Optional @var{flowinfo} and @var{scopeid}
2867 arguments may be given (both integers, default 0).
2868
2869 For @code{AF_UNIX} the argument is a filename (a string).
2870
2871 The C function @code{scm_make_socket_address} takes the @var{family}
2872 and @var{address} arguments directly, then @var{arglist} is a list of
2873 further arguments, being the port for IPv4, port and optional flowinfo
2874 and scopeid for IPv6, or the empty list @code{SCM_EOL} for Unix
2875 domain.
2876 @end deffn
2877
2878 @noindent
2879 The following functions access the fields of a socket address object,
2880
2881 @deffn {Scheme Procedure} sockaddr:fam sa
2882 Return the address family from socket address object @var{sa}. This
2883 is one of the @code{AF} constants (e.g.@: @code{AF_INET}).
2884 @end deffn
2885
2886 @deffn {Scheme Procedure} sockaddr:path sa
2887 For an @code{AF_UNIX} socket address object @var{sa}, return the
2888 filename.
2889 @end deffn
2890
2891 @deffn {Scheme Procedure} sockaddr:addr sa
2892 For an @code{AF_INET} or @code{AF_INET6} socket address object
2893 @var{sa}, return the network address number.
2894 @end deffn
2895
2896 @deffn {Scheme Procedure} sockaddr:port sa
2897 For an @code{AF_INET} or @code{AF_INET6} socket address object
2898 @var{sa}, return the port number.
2899 @end deffn
2900
2901 @deffn {Scheme Procedure} sockaddr:flowinfo sa
2902 For an @code{AF_INET6} socket address object @var{sa}, return the
2903 flowinfo value.
2904 @end deffn
2905
2906 @deffn {Scheme Procedure} sockaddr:scopeid sa
2907 For an @code{AF_INET6} socket address object @var{sa}, return the
2908 scope ID value.
2909 @end deffn
2910
2911 @tpindex @code{struct sockaddr}
2912 @tpindex @code{sockaddr}
2913 The functions below convert to and from the C @code{struct sockaddr}
2914 (@pxref{Address Formats,,, libc, The GNU C Library Reference Manual}).
2915 That structure is a generic type, an application can cast to or from
2916 @code{struct sockaddr_in}, @code{struct sockaddr_in6} or @code{struct
2917 sockaddr_un} according to the address family.
2918
2919 In a @code{struct sockaddr} taken or returned, the byte ordering in
2920 the fields follows the C conventions (@pxref{Byte Order,, Byte Order
2921 Conversion, libc, The GNU C Library Reference Manual}). This means
2922 network byte order for @code{AF_INET} host address
2923 (@code{sin_addr.s_addr}) and port number (@code{sin_port}), and
2924 @code{AF_INET6} port number (@code{sin6_port}). But at the Scheme
2925 level these values are taken or returned in host byte order, so the
2926 port is an ordinary integer, and the host address likewise is an
2927 ordinary integer (as described in @ref{Network Address Conversion}).
2928
2929 @deftypefn {C Function} {struct sockaddr *} scm_c_make_socket_address (SCM family, SCM address, SCM args, size_t *outsize)
2930 Return a newly-@code{malloc}ed @code{struct sockaddr} created from
2931 arguments like those taken by @code{scm_make_socket_address} above.
2932
2933 The size (in bytes) of the @code{struct sockaddr} return is stored
2934 into @code{*@var{outsize}}. An application must call @code{free} to
2935 release the returned structure when no longer required.
2936 @end deftypefn
2937
2938 @deftypefn {C Function} SCM scm_from_sockaddr (const struct sockaddr *address, unsigned address_size)
2939 Return a Scheme socket address object from the C @var{address}
2940 structure. @var{address_size} is the size in bytes of @var{address}.
2941 @end deftypefn
2942
2943 @deftypefn {C Function} {struct sockaddr *} scm_to_sockaddr (SCM address, size_t *address_size)
2944 Return a newly-@code{malloc}ed @code{struct sockaddr} from a Scheme
2945 level socket address object.
2946
2947 The size (in bytes) of the @code{struct sockaddr} return is stored
2948 into @code{*@var{outsize}}. An application must call @code{free} to
2949 release the returned structure when no longer required.
2950 @end deftypefn
2951
2952
2953 @node Network Sockets and Communication
2954 @subsubsection Network Sockets and Communication
2955 @cindex socket
2956 @cindex network socket
2957
2958 Socket ports can be created using @code{socket} and @code{socketpair}.
2959 The ports are initially unbuffered, to make reading and writing to the
2960 same port more reliable. A buffer can be added to the port using
2961 @code{setvbuf}; see @ref{Ports and File Descriptors}.
2962
2963 Most systems have limits on how many files and sockets can be open, so
2964 it's strongly recommended that socket ports be closed explicitly when
2965 no longer required (@pxref{Ports}).
2966
2967 Some of the underlying C functions take values in network byte order,
2968 but the convention in Guile is that at the Scheme level everything is
2969 ordinary host byte order and conversions are made automatically where
2970 necessary.
2971
2972 @deffn {Scheme Procedure} socket family style proto
2973 @deffnx {C Function} scm_socket (family, style, proto)
2974 Return a new socket port of the type specified by @var{family},
2975 @var{style} and @var{proto}. All three parameters are integers. The
2976 possible values for @var{family} are as follows, where supported by
2977 the system,
2978
2979 @defvar PF_UNIX
2980 @defvarx PF_INET
2981 @defvarx PF_INET6
2982 @end defvar
2983
2984 The possible values for @var{style} are as follows, again where
2985 supported by the system,
2986
2987 @defvar SOCK_STREAM
2988 @defvarx SOCK_DGRAM
2989 @defvarx SOCK_RAW
2990 @defvarx SOCK_RDM
2991 @defvarx SOCK_SEQPACKET
2992 @end defvar
2993
2994 @var{proto} can be obtained from a protocol name using
2995 @code{getprotobyname} (@pxref{Network Databases}). A value of zero
2996 means the default protocol, which is usually right.
2997
2998 A socket cannot by used for communication until it has been connected
2999 somewhere, usually with either @code{connect} or @code{accept} below.
3000 @end deffn
3001
3002 @deffn {Scheme Procedure} socketpair family style proto
3003 @deffnx {C Function} scm_socketpair (family, style, proto)
3004 Return a pair, the @code{car} and @code{cdr} of which are two unnamed
3005 socket ports connected to each other. The connection is full-duplex,
3006 so data can be transferred in either direction between the two.
3007
3008 @var{family}, @var{style} and @var{proto} are as per @code{socket}
3009 above. But many systems only support socket pairs in the
3010 @code{PF_UNIX} family. Zero is likely to be the only meaningful value
3011 for @var{proto}.
3012 @end deffn
3013
3014 @deffn {Scheme Procedure} getsockopt sock level optname
3015 @deffnx {Scheme Procedure} setsockopt sock level optname value
3016 @deffnx {C Function} scm_getsockopt (sock, level, optname)
3017 @deffnx {C Function} scm_setsockopt (sock, level, optname, value)
3018 Get or set an option on socket port @var{sock}. @code{getsockopt}
3019 returns the current value. @code{setsockopt} sets a value and the
3020 return is unspecified.
3021
3022 @var{level} is an integer specifying a protocol layer, either
3023 @code{SOL_SOCKET} for socket level options, or a protocol number from
3024 the @code{IPPROTO} constants or @code{getprotoent} (@pxref{Network
3025 Databases}).
3026
3027 @defvar SOL_SOCKET
3028 @defvarx IPPROTO_IP
3029 @defvarx IPPROTO_TCP
3030 @defvarx IPPROTO_UDP
3031 @end defvar
3032
3033 @var{optname} is an integer specifying an option within the protocol
3034 layer.
3035
3036 For @code{SOL_SOCKET} level the following @var{optname}s are defined
3037 (when provided by the system). For their meaning see
3038 @ref{Socket-Level Options,,, libc, The GNU C Library Reference
3039 Manual}, or @command{man 7 socket}.
3040
3041 @defvar SO_DEBUG
3042 @defvarx SO_REUSEADDR
3043 @defvarx SO_STYLE
3044 @defvarx SO_TYPE
3045 @defvarx SO_ERROR
3046 @defvarx SO_DONTROUTE
3047 @defvarx SO_BROADCAST
3048 @defvarx SO_SNDBUF
3049 @defvarx SO_RCVBUF
3050 @defvarx SO_KEEPALIVE
3051 @defvarx SO_OOBINLINE
3052 @defvarx SO_NO_CHECK
3053 @defvarx SO_PRIORITY
3054 The @var{value} taken or returned is an integer.
3055 @end defvar
3056
3057 @defvar SO_LINGER
3058 The @var{value} taken or returned is a pair of integers
3059 @code{(@var{ENABLE} . @var{TIMEOUT})}. On old systems without timeout
3060 support (ie.@: without @code{struct linger}), only @var{ENABLE} has an
3061 effect but the value in Guile is always a pair.
3062 @end defvar
3063
3064 @c Note that we refer only to ``man ip'' here. On GNU/Linux it's
3065 @c ``man 7 ip'' but on NetBSD it's ``man 4 ip''.
3066 @c
3067 For IP level (@code{IPPROTO_IP}) the following @var{optname}s are
3068 defined (when provided by the system). See @command{man ip} for what
3069 they mean.
3070
3071 @defvar IP_MULTICAST_IF
3072 This sets the source interface used by multicast traffic.
3073 @end defvar
3074
3075 @defvar IP_MULTICAST_TTL
3076 This sets the default TTL for multicast traffic. This defaults
3077 to 1 and should be increased to allow traffic to pass beyond the
3078 local network.
3079 @end defvar
3080
3081 @defvar IP_ADD_MEMBERSHIP
3082 @defvarx IP_DROP_MEMBERSHIP
3083 These can be used only with @code{setsockopt}, not @code{getsockopt}.
3084 @var{value} is a pair @code{(@var{MULTIADDR} . @var{INTERFACEADDR})}
3085 of integer IPv4 addresses (@pxref{Network Address Conversion}).
3086 @var{MULTIADDR} is a multicast address to be added to or dropped from
3087 the interface @var{INTERFACEADDR}. @var{INTERFACEADDR} can be
3088 @code{INADDR_ANY} to have the system select the interface.
3089 @var{INTERFACEADDR} can also be an interface index number, on systems
3090 supporting that.
3091 @end defvar
3092 @end deffn
3093
3094 @deffn {Scheme Procedure} shutdown sock how
3095 @deffnx {C Function} scm_shutdown (sock, how)
3096 Sockets can be closed simply by using @code{close-port}. The
3097 @code{shutdown} procedure allows reception or transmission on a
3098 connection to be shut down individually, according to the parameter
3099 @var{how}:
3100
3101 @table @asis
3102 @item 0
3103 Stop receiving data for this socket. If further data arrives, reject it.
3104 @item 1
3105 Stop trying to transmit data from this socket. Discard any
3106 data waiting to be sent. Stop looking for acknowledgement of
3107 data already sent; don't retransmit it if it is lost.
3108 @item 2
3109 Stop both reception and transmission.
3110 @end table
3111
3112 The return value is unspecified.
3113 @end deffn
3114
3115 @deffn {Scheme Procedure} connect sock sockaddr
3116 @deffnx {Scheme Procedure} connect sock AF_INET ipv4addr port
3117 @deffnx {Scheme Procedure} connect sock AF_INET6 ipv6addr port [flowinfo [scopeid]]
3118 @deffnx {Scheme Procedure} connect sock AF_UNIX path
3119 @deffnx {C Function} scm_connect (sock, fam, address, args)
3120 Initiate a connection on socket port @var{sock} to a given address.
3121 The destination is either a socket address object, or arguments the
3122 same as @code{make-socket-address} would take to make such an object
3123 (@pxref{Network Socket Address}). The return value is unspecified.
3124
3125 @example
3126 (connect sock AF_INET INADDR_LOOPBACK 23)
3127 (connect sock (make-socket-address AF_INET INADDR_LOOPBACK 23))
3128 @end example
3129 @end deffn
3130
3131 @deffn {Scheme Procedure} bind sock sockaddr
3132 @deffnx {Scheme Procedure} bind sock AF_INET ipv4addr port
3133 @deffnx {Scheme Procedure} bind sock AF_INET6 ipv6addr port [flowinfo [scopeid]]
3134 @deffnx {Scheme Procedure} bind sock AF_UNIX path
3135 @deffnx {C Function} scm_bind (sock, fam, address, args)
3136 Bind socket port @var{sock} to the given address. The address is
3137 either a socket address object, or arguments the same as
3138 @code{make-socket-address} would take to make such an object
3139 (@pxref{Network Socket Address}). The return value is unspecified.
3140
3141 Generally a socket is only explicitly bound to a particular address
3142 when making a server, i.e.@: to listen on a particular port. For an
3143 outgoing connection the system will assign a local address
3144 automatically, if not already bound.
3145
3146 @example
3147 (bind sock AF_INET INADDR_ANY 12345)
3148 (bind sock (make-socket-address AF_INET INADDR_ANY 12345))
3149 @end example
3150 @end deffn
3151
3152 @deffn {Scheme Procedure} listen sock backlog
3153 @deffnx {C Function} scm_listen (sock, backlog)
3154 Enable @var{sock} to accept connection
3155 requests. @var{backlog} is an integer specifying
3156 the maximum length of the queue for pending connections.
3157 If the queue fills, new clients will fail to connect until
3158 the server calls @code{accept} to accept a connection from
3159 the queue.
3160
3161 The return value is unspecified.
3162 @end deffn
3163
3164 @deffn {Scheme Procedure} accept sock
3165 @deffnx {C Function} scm_accept (sock)
3166 Accept a connection from socket port @var{sock} which has been enabled
3167 for listening with @code{listen} above. If there are no incoming
3168 connections in the queue, wait until one is available (unless
3169 @code{O_NONBLOCK} has been set on the socket, @pxref{Ports and File
3170 Descriptors,@code{fcntl}}).
3171
3172 The return value is a pair. The @code{car} is a new socket port,
3173 connected and ready to communicate. The @code{cdr} is a socket
3174 address object (@pxref{Network Socket Address}) which is where the
3175 remote connection is from (like @code{getpeername} below).
3176
3177 All communication takes place using the new socket returned. The
3178 given @var{sock} remains bound and listening, and @code{accept} may be
3179 called on it again to get another incoming connection when desired.
3180 @end deffn
3181
3182 @deffn {Scheme Procedure} getsockname sock
3183 @deffnx {C Function} scm_getsockname (sock)
3184 Return a socket address object which is the where @var{sock} is bound
3185 locally. @var{sock} may have obtained its local address from
3186 @code{bind} (above), or if a @code{connect} is done with an otherwise
3187 unbound socket (which is usual) then the system will have assigned an
3188 address.
3189
3190 Note that on many systems the address of a socket in the
3191 @code{AF_UNIX} namespace cannot be read.
3192 @end deffn
3193
3194 @deffn {Scheme Procedure} getpeername sock
3195 @deffnx {C Function} scm_getpeername (sock)
3196 Return a socket address object which is where @var{sock} is connected
3197 to, i.e.@: the remote endpoint.
3198
3199 Note that on many systems the address of a socket in the
3200 @code{AF_UNIX} namespace cannot be read.
3201 @end deffn
3202
3203 @deffn {Scheme Procedure} recv! sock buf [flags]
3204 @deffnx {C Function} scm_recv (sock, buf, flags)
3205 Receive data from a socket port.
3206 @var{sock} must already
3207 be bound to the address from which data is to be received.
3208 @var{buf} is a bytevector into which
3209 the data will be written. The size of @var{buf} limits
3210 the amount of
3211 data which can be received: in the case of packet
3212 protocols, if a packet larger than this limit is encountered
3213 then some data
3214 will be irrevocably lost.
3215
3216 @vindex MSG_OOB
3217 @vindex MSG_PEEK
3218 @vindex MSG_DONTROUTE
3219 The optional @var{flags} argument is a value or bitwise OR of
3220 @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3221
3222 The value returned is the number of bytes read from the
3223 socket.
3224
3225 Note that the data is read directly from the socket file
3226 descriptor:
3227 any unread buffered port data is ignored.
3228 @end deffn
3229
3230 @deffn {Scheme Procedure} send sock message [flags]
3231 @deffnx {C Function} scm_send (sock, message, flags)
3232 @vindex MSG_OOB
3233 @vindex MSG_PEEK
3234 @vindex MSG_DONTROUTE
3235 Transmit bytevector @var{message} on socket port @var{sock}.
3236 @var{sock} must already be bound to a destination address. The value
3237 returned is the number of bytes transmitted---it's possible for this
3238 to be less than the length of @var{message} if the socket is set to be
3239 non-blocking. The optional @var{flags} argument is a value or bitwise
3240 OR of @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3241
3242 Note that the data is written directly to the socket
3243 file descriptor:
3244 any unflushed buffered port data is ignored.
3245 @end deffn
3246
3247 @deffn {Scheme Procedure} recvfrom! sock buf [flags [start [end]]]
3248 @deffnx {C Function} scm_recvfrom (sock, buf, flags, start, end)
3249 Receive data from socket port @var{sock}, returning the originating
3250 address as well as the data. This function is usually for datagram
3251 sockets, but can be used on stream-oriented sockets too.
3252
3253 The data received is stored in bytevector @var{buf}, using
3254 either the whole bytevector or just the region between the optional
3255 @var{start} and @var{end} positions. The size of @var{buf}
3256 limits the amount of data that can be received. For datagram
3257 protocols if a packet larger than this is received then excess
3258 bytes are irrevocably lost.
3259
3260 The return value is a pair. The @code{car} is the number of bytes
3261 read. The @code{cdr} is a socket address object (@pxref{Network
3262 Socket Address}) which is where the data came from, or @code{#f} if
3263 the origin is unknown.
3264
3265 @vindex MSG_OOB
3266 @vindex MSG_PEEK
3267 @vindex MSG_DONTROUTE
3268 The optional @var{flags} argument is a or bitwise-OR (@code{logior})
3269 of @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3270
3271 Data is read directly from the socket file descriptor, any buffered
3272 port data is ignored.
3273
3274 @c This was linux kernel 2.6.15 and glibc 2.3.6, not sure what any
3275 @c specs are supposed to say about recvfrom threading.
3276 @c
3277 On a GNU/Linux system @code{recvfrom!} is not multi-threading, all
3278 threads stop while a @code{recvfrom!} call is in progress. An
3279 application may need to use @code{select}, @code{O_NONBLOCK} or
3280 @code{MSG_DONTWAIT} to avoid this.
3281 @end deffn
3282
3283 @deffn {Scheme Procedure} sendto sock message sockaddr [flags]
3284 @deffnx {Scheme Procedure} sendto sock message AF_INET ipv4addr port [flags]
3285 @deffnx {Scheme Procedure} sendto sock message AF_INET6 ipv6addr port [flowinfo [scopeid [flags]]]
3286 @deffnx {Scheme Procedure} sendto sock message AF_UNIX path [flags]
3287 @deffnx {C Function} scm_sendto (sock, message, fam, address, args_and_flags)
3288 Transmit bytevector @var{message} as a datagram socket port
3289 @var{sock}. The destination is specified either as a socket address
3290 object, or as arguments the same as would be taken by
3291 @code{make-socket-address} to create such an object (@pxref{Network
3292 Socket Address}).
3293
3294 The destination address may be followed by an optional @var{flags}
3295 argument which is a @code{logior} (@pxref{Bitwise Operations}) of
3296 @code{MSG_OOB}, @code{MSG_PEEK}, @code{MSG_DONTROUTE} etc.
3297
3298 The value returned is the number of bytes transmitted --
3299 it's possible for
3300 this to be less than the length of @var{message} if the
3301 socket is
3302 set to be non-blocking.
3303 Note that the data is written directly to the socket
3304 file descriptor:
3305 any unflushed buffered port data is ignored.
3306 @end deffn
3307
3308 The following functions can be used to convert short and long integers
3309 between ``host'' and ``network'' order. Although the procedures above do
3310 this automatically for addresses, the conversion will still need to
3311 be done when sending or receiving encoded integer data from the network.
3312
3313 @deffn {Scheme Procedure} htons value
3314 @deffnx {C Function} scm_htons (value)
3315 Convert a 16 bit quantity from host to network byte ordering.
3316 @var{value} is packed into 2 bytes, which are then converted
3317 and returned as a new integer.
3318 @end deffn
3319
3320 @deffn {Scheme Procedure} ntohs value
3321 @deffnx {C Function} scm_ntohs (value)
3322 Convert a 16 bit quantity from network to host byte ordering.
3323 @var{value} is packed into 2 bytes, which are then converted
3324 and returned as a new integer.
3325 @end deffn
3326
3327 @deffn {Scheme Procedure} htonl value
3328 @deffnx {C Function} scm_htonl (value)
3329 Convert a 32 bit quantity from host to network byte ordering.
3330 @var{value} is packed into 4 bytes, which are then converted
3331 and returned as a new integer.
3332 @end deffn
3333
3334 @deffn {Scheme Procedure} ntohl value
3335 @deffnx {C Function} scm_ntohl (value)
3336 Convert a 32 bit quantity from network to host byte ordering.
3337 @var{value} is packed into 4 bytes, which are then converted
3338 and returned as a new integer.
3339 @end deffn
3340
3341 These procedures are inconvenient to use at present, but consider:
3342
3343 @example
3344 (define write-network-long
3345 (lambda (value port)
3346 (let ((v (make-uniform-vector 1 1 0)))
3347 (uniform-vector-set! v 0 (htonl value))
3348 (uniform-vector-write v port))))
3349
3350 (define read-network-long
3351 (lambda (port)
3352 (let ((v (make-uniform-vector 1 1 0)))
3353 (uniform-vector-read! v port)
3354 (ntohl (uniform-vector-ref v 0)))))
3355 @end example
3356
3357
3358 @node Internet Socket Examples
3359 @subsubsection Network Socket Examples
3360 @cindex network examples
3361 @cindex socket examples
3362
3363 The following give examples of how to use network sockets.
3364
3365 @subsubheading Internet Socket Client Example
3366
3367 @cindex socket client example
3368 The following example demonstrates an Internet socket client.
3369 It connects to the HTTP daemon running on the local machine and
3370 returns the contents of the root index URL.
3371
3372 @example
3373 (let ((s (socket PF_INET SOCK_STREAM 0)))
3374 (connect s AF_INET (inet-pton AF_INET "127.0.0.1") 80)
3375 (display "GET / HTTP/1.0\r\n\r\n" s)
3376
3377 (do ((line (read-line s) (read-line s)))
3378 ((eof-object? line))
3379 (display line)
3380 (newline)))
3381 @end example
3382
3383
3384 @subsubheading Internet Socket Server Example
3385
3386 @cindex socket server example
3387 The following example shows a simple Internet server which listens on
3388 port 2904 for incoming connections and sends a greeting back to the
3389 client.
3390
3391 @example
3392 (let ((s (socket PF_INET SOCK_STREAM 0)))
3393 (setsockopt s SOL_SOCKET SO_REUSEADDR 1)
3394 ;; @r{Specific address?}
3395 ;; @r{(bind s AF_INET (inet-pton AF_INET "127.0.0.1") 2904)}
3396 (bind s AF_INET INADDR_ANY 2904)
3397 (listen s 5)
3398
3399 (simple-format #t "Listening for clients in pid: ~S" (getpid))
3400 (newline)
3401
3402 (while #t
3403 (let* ((client-connection (accept s))
3404 (client-details (cdr client-connection))
3405 (client (car client-connection)))
3406 (simple-format #t "Got new client connection: ~S"
3407 client-details)
3408 (newline)
3409 (simple-format #t "Client address: ~S"
3410 (gethostbyaddr
3411 (sockaddr:addr client-details)))
3412 (newline)
3413 ;; @r{Send back the greeting to the client port}
3414 (display "Hello client\r\n" client)
3415 (close client))))
3416 @end example
3417
3418
3419 @node System Identification
3420 @subsection System Identification
3421 @cindex system name
3422
3423 This section lists the various procedures Guile provides for accessing
3424 information about the system it runs on.
3425
3426 @deffn {Scheme Procedure} uname
3427 @deffnx {C Function} scm_uname ()
3428 Return an object with some information about the computer
3429 system the program is running on.
3430
3431 The following procedures accept an object as returned by @code{uname}
3432 and return a selected component (all of which are strings).
3433
3434 @deffn {Scheme Procedure} utsname:sysname un
3435 The name of the operating system.
3436 @end deffn
3437 @deffn {Scheme Procedure} utsname:nodename un
3438 The network name of the computer.
3439 @end deffn
3440 @deffn {Scheme Procedure} utsname:release un
3441 The current release level of the operating system implementation.
3442 @end deffn
3443 @deffn {Scheme Procedure} utsname:version un
3444 The current version level within the release of the operating system.
3445 @end deffn
3446 @deffn {Scheme Procedure} utsname:machine un
3447 A description of the hardware.
3448 @end deffn
3449 @end deffn
3450
3451 @deffn {Scheme Procedure} gethostname
3452 @deffnx {C Function} scm_gethostname ()
3453 @cindex host name
3454 Return the host name of the current processor.
3455 @end deffn
3456
3457 @deffn {Scheme Procedure} sethostname name
3458 @deffnx {C Function} scm_sethostname (name)
3459 Set the host name of the current processor to @var{name}. May
3460 only be used by the superuser. The return value is not
3461 specified.
3462 @end deffn
3463
3464 @node Locales
3465 @subsection Locales
3466 @cindex locale
3467
3468 @deffn {Scheme Procedure} setlocale category [locale]
3469 @deffnx {C Function} scm_setlocale (category, locale)
3470 Get or set the current locale, used for various internationalizations.
3471 Locales are strings, such as @samp{sv_SE}.
3472
3473 If @var{locale} is given then the locale for the given @var{category}
3474 is set and the new value returned. If @var{locale} is not given then
3475 the current value is returned. @var{category} should be one of the
3476 following values (@pxref{Locale Categories, Categories of Activities
3477 that Locales Affect,, libc, The GNU C Library Reference Manual}):
3478
3479 @defvar LC_ALL
3480 @defvarx LC_COLLATE
3481 @defvarx LC_CTYPE
3482 @defvarx LC_MESSAGES
3483 @defvarx LC_MONETARY
3484 @defvarx LC_NUMERIC
3485 @defvarx LC_TIME
3486 @end defvar
3487
3488 @cindex @code{LANG}
3489 A common usage is @samp{(setlocale LC_ALL "")}, which initializes all
3490 categories based on standard environment variables (@code{LANG} etc).
3491 For full details on categories and locale names @pxref{Locales,,
3492 Locales and Internationalization, libc, The GNU C Library Reference
3493 Manual}.
3494
3495 Note that @code{setlocale} affects locale settings for the whole
3496 process. @xref{i18n Introduction, locale objects and
3497 @code{make-locale}}, for a thread-safe alternative.
3498 @end deffn
3499
3500 @node Encryption
3501 @subsection Encryption
3502 @cindex encryption
3503
3504 Please note that the procedures in this section are not suited for
3505 strong encryption, they are only interfaces to the well-known and
3506 common system library functions of the same name. They are just as good
3507 (or bad) as the underlying functions, so you should refer to your system
3508 documentation before using them (@pxref{crypt,, Encrypting Passwords,
3509 libc, The GNU C Library Reference Manual}).
3510
3511 @deffn {Scheme Procedure} crypt key salt
3512 @deffnx {C Function} scm_crypt (key, salt)
3513 Encrypt @var{key}, with the addition of @var{salt} (both strings),
3514 using the @code{crypt} C library call.
3515 @end deffn
3516
3517 Although @code{getpass} is not an encryption procedure per se, it
3518 appears here because it is often used in combination with @code{crypt}:
3519
3520 @deffn {Scheme Procedure} getpass prompt
3521 @deffnx {C Function} scm_getpass (prompt)
3522 @cindex password
3523 Display @var{prompt} to the standard error output and read
3524 a password from @file{/dev/tty}. If this file is not
3525 accessible, it reads from standard input. The password may be
3526 up to 127 characters in length. Additional characters and the
3527 terminating newline character are discarded. While reading
3528 the password, echoing and the generation of signals by special
3529 characters is disabled.
3530 @end deffn
3531
3532
3533 @c Local Variables:
3534 @c TeX-master: "guile.texi"
3535 @c End: