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1 .\" Copyright (c) 2009 Bill O. Gallmeister (bgallmeister@gmail.com)
2 .\" and Copyright 2010 Michael Kerrisk <mtk.manpages@gmail.com>
3 .\"
4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
5 .\"
6 .\" References consulted:
7 .\" Linux glibc source code
8 .\" POSIX 1003.1-2004 documentation
9 .\" (http://www.opengroup.org/onlinepubs/009695399)
10 .\"
11 .TH posix_spawn 3 (date) "Linux man-pages (unreleased)"
12 .SH NAME
13 posix_spawn, posix_spawnp \- spawn a process
14 .SH LIBRARY
15 Standard C library
16 .RI ( libc ", " \-lc )
17 .SH SYNOPSIS
18 .nf
19 .B #include <spawn.h>
20 .P
21 .BI "int posix_spawn(pid_t *restrict " pid ", const char *restrict " path ,
22 .BI " const posix_spawn_file_actions_t *restrict " file_actions ,
23 .BI " const posix_spawnattr_t *restrict " attrp ,
24 .BI " char *const " argv [restrict],
25 .BI " char *const " envp [restrict]);
26 .BI "int posix_spawnp(pid_t *restrict " pid ", const char *restrict " file ,
27 .BI " const posix_spawn_file_actions_t *restrict " file_actions ,
28 .BI " const posix_spawnattr_t *restrict " attrp ,
29 .BI " char *const " argv [restrict],
30 .BI " char *const " envp [restrict]);
31 .fi
32 .SH DESCRIPTION
33 The
34 .BR posix_spawn ()
35 and
36 .BR posix_spawnp ()
37 functions are used to create a new child process that executes
38 a specified file.
39 These functions were specified by POSIX to provide a standardized method
40 of creating new processes on machines that lack the capability
41 to support the
42 .BR fork (2)
43 system call.
44 These machines are generally small, embedded systems lacking MMU support.
45 .P
46 The
47 .BR posix_spawn ()
48 and
49 .BR posix_spawnp ()
50 functions provide the functionality of a combined
51 .BR fork (2)
52 and
53 .BR exec (3),
54 with some optional housekeeping steps in the child process before the
55 .BR exec (3).
56 These functions are not meant to replace the
57 .BR fork (2)
58 and
59 .BR execve (2)
60 system calls.
61 In fact, they provide only a subset of the functionality
62 that can be achieved by using the system calls.
63 .P
64 The only difference between
65 .BR posix_spawn ()
66 and
67 .BR posix_spawnp ()
68 is the manner in which they specify the file to be executed by
69 the child process.
70 With
71 .BR posix_spawn (),
72 the executable file is specified as a pathname
73 (which can be absolute or relative).
74 With
75 .BR posix_spawnp (),
76 the executable file is specified as a simple filename;
77 the system searches for this file in the list of directories specified by
78 .B PATH
79 (in the same way as for
80 .BR execvp (3)).
81 For the remainder of this page, the discussion is phrased in terms of
82 .BR posix_spawn (),
83 with the understanding that
84 .BR posix_spawnp ()
85 differs only on the point just described.
86 .P
87 The remaining arguments to these two functions are as follows:
88 .TP
89 .I pid
90 points to a buffer that is used to return the process ID
91 of the new child process.
92 .TP
93 .I file_actions
94 points to a
95 .I "spawn file actions object"
96 that specifies file-related actions to be performed in the child
97 between the
98 .BR fork (2)
99 and
100 .BR exec (3)
101 steps.
102 This object is initialized and populated before the
103 .BR posix_spawn ()
104 call using
105 .BR posix_spawn_file_actions_init (3)
106 and the
107 .BR posix_spawn_file_actions_* ()
108 functions.
109 .TP
110 .I attrp
111 points to an
112 .I attributes objects
113 that specifies various attributes of the created child process.
114 This object is initialized and populated before the
115 .BR posix_spawn ()
116 call using
117 .BR posix_spawnattr_init (3)
118 and the
119 .BR posix_spawnattr_* ()
120 functions.
121 .TP
122 .I argv
123 .TQ
124 .I envp
125 specify the argument list and environment for the program
126 that is executed in the child process, as for
127 .BR execve (2).
128 .P
129 Below, the functions are described in terms of a three-step process: the
130 .BR fork ()
131 step, the
132 .RB pre- exec ()
133 step (executed in the child),
134 and the
135 .BR exec ()
136 step (executed in the child).
137 .SS fork() step
138 Since glibc 2.24, the
139 .BR posix_spawn ()
140 function commences by calling
141 .BR clone (2)
142 with
143 .B CLONE_VM
144 and
145 .B CLONE_VFORK
146 flags.
147 Older implementations use
148 .BR fork (2),
149 or possibly
150 .BR vfork (2)
151 (see below).
152 .P
153 The PID of the new child process is placed in
154 .IR *pid .
155 The
156 .BR posix_spawn ()
157 function then returns control to the parent process.
158 .P
159 Subsequently, the parent can use one of the system calls described in
160 .BR wait (2)
161 to check the status of the child process.
162 If the child fails in any of the housekeeping steps described below,
163 or fails to execute the desired file,
164 it exits with a status of 127.
165 .P
166 Before glibc 2.24, the child process is created using
167 .BR vfork (2)
168 instead of
169 .BR fork (2)
170 when either of the following is true:
171 .IP \[bu] 3
172 the
173 .I spawn-flags
174 element of the attributes object pointed to by
175 .I attrp
176 contains the GNU-specific flag
177 .BR POSIX_SPAWN_USEVFORK ;
178 or
179 .IP \[bu]
180 .I file_actions
181 is NULL and the
182 .I spawn-flags
183 element of the attributes object pointed to by
184 .I attrp
185 does \fInot\fP contain
186 .BR POSIX_SPAWN_SETSIGMASK ,
187 .BR POSIX_SPAWN_SETSIGDEF ,
188 .BR POSIX_SPAWN_SETSCHEDPARAM ,
189 .BR POSIX_SPAWN_SETSCHEDULER ,
190 .BR POSIX_SPAWN_SETPGROUP ,
191 or
192 .BR POSIX_SPAWN_RESETIDS .
193 .P
194 In other words,
195 .BR vfork (2)
196 is used if the caller requests it,
197 or if there is no cleanup expected in the child before it
198 .BR exec (3)s
199 the requested file.
200 .SS pre-exec() step: housekeeping
201 In between the
202 .B fork()
203 and the
204 .B exec()
205 steps, a child process may need to perform a set of housekeeping actions.
206 The
207 .BR posix_spawn ()
208 and
209 .BR posix_spawnp ()
210 functions support a small, well-defined set of system tasks that the child
211 process can accomplish before it executes the executable file.
212 These operations are controlled by the attributes object pointed to by
213 .I attrp
214 and the file actions object pointed to by
215 .IR file_actions .
216 In the child, processing is done in the following sequence:
217 .IP (1) 5
218 Process attribute actions: signal mask, signal default handlers,
219 scheduling algorithm and parameters,
220 process group, and effective user and group IDs
221 are changed as specified by the attributes object pointed to by
222 .IR attrp .
223 .IP (2)
224 File actions, as specified in the
225 .I file_actions
226 argument,
227 are performed in the order that they were specified using calls to the
228 .BR posix_spawn_file_actions_add* ()
229 functions.
230 .IP (3)
231 File descriptors with the
232 .B FD_CLOEXEC
233 flag set are closed.
234 .P
235 All process attributes in the child,
236 other than those affected by attributes specified in the
237 object pointed to by
238 .I attrp
239 and the file actions in the object pointed to by
240 .IR file_actions ,
241 will be affected as though the child was created with
242 .BR fork (2)
243 and it executed the program with
244 .BR execve (2).
245 .P
246 The process attributes actions are defined by the attributes object
247 pointed to by
248 .IR attrp .
249 The
250 .I spawn-flags
251 attribute (set using
252 .BR posix_spawnattr_setflags (3))
253 controls the general actions that occur,
254 and other attributes in the object specify values
255 to be used during those actions.
256 .P
257 The effects of the flags that may be specified in
258 .I spawn-flags
259 are as follows:
260 .TP
261 .B POSIX_SPAWN_SETSIGMASK
262 Set the signal mask to the signal set specified in the
263 .I spawn-sigmask
264 attribute
265 .\" FIXME .
266 .\" (see
267 .\" .BR posix_spawnattr_setsigmask (3))
268 of the object pointed to by
269 .IR attrp .
270 If the
271 .B POSIX_SPAWN_SETSIGMASK
272 flag is not set, then the child inherits the parent's signal mask.
273 .TP
274 .B POSIX_SPAWN_SETSIGDEF
275 Reset the disposition of all signals in the set specified in the
276 .I spawn-sigdefault
277 attribute
278 .\" FIXME .
279 .\" (see
280 .\" .BR posix_spawnattr_setsigdefault (3))
281 of the object pointed to by
282 .I attrp
283 to the default.
284 For the treatment of the dispositions of signals not specified in the
285 .I spawn-sigdefault
286 attribute, or the treatment when
287 .B POSIX_SPAWN_SETSIGDEF
288 is not specified, see
289 .BR execve (2).
290 .TP
291 .B POSIX_SPAWN_SETSCHEDPARAM
292 .\" (POSIX_PRIORITY_SCHEDULING only)
293 If this flag is set, and the
294 .B POSIX_SPAWN_SETSCHEDULER
295 flag is not set, then set the scheduling parameters
296 to the parameters specified in the
297 .I spawn-schedparam
298 attribute
299 .\" FIXME .
300 .\" (see
301 .\" .BR posix_spawnattr_setschedparam (3))
302 of the object pointed to by
303 .IR attrp .
304 .TP
305 .B POSIX_SPAWN_SETSCHEDULER
306 Set the scheduling policy algorithm and parameters of the child,
307 as follows:
308 .RS
309 .IP \[bu] 3
310 The scheduling policy is set to the value specified in the
311 .I spawn-schedpolicy
312 attribute
313 .\" FIXME .
314 .\" (see
315 .\" .BR posix_spawnattr_setpolicy (3))
316 of the object pointed to by
317 .IR attrp .
318 .IP \[bu]
319 The scheduling parameters are set to the value specified in the
320 .I spawn-schedparam
321 attribute
322 .\" FIXME .
323 .\" (see
324 .\" .BR posix_spawnattr_setschedparam (3))
325 of the object pointed to by
326 .I attrp
327 (but see BUGS).
328 .P
329 If the
330 .B POSIX_SPAWN_SETSCHEDPARAM
331 and
332 .B POSIX_SPAWN_SETSCHEDPOLICY
333 flags are not specified,
334 the child inherits the corresponding scheduling attributes from the parent.
335 .RE
336 .TP
337 .B POSIX_SPAWN_RESETIDS
338 If this flag is set,
339 reset the effective UID and GID to the
340 real UID and GID of the parent process.
341 If this flag is not set,
342 then the child retains the effective UID and GID of the parent.
343 In either case, if the set-user-ID and set-group-ID permission
344 bits are enabled on the executable file, their effect will override
345 the setting of the effective UID and GID (se
346 .BR execve (2)).
347 .TP
348 .B POSIX_SPAWN_SETPGROUP
349 Set the process group to the value specified in the
350 .I spawn-pgroup
351 attribute
352 .\" FIXME .
353 .\" (see
354 .\" .BR posix_spawnattr_setpgroup (3))
355 of the object pointed to by
356 .IR attrp .
357 If the
358 .I spawn-pgroup
359 attribute has the value 0,
360 the child's process group ID is made the same as its process ID.
361 If the
362 .B POSIX_SPAWN_SETPGROUP
363 flag is not set, the child inherits the parent's process group ID.
364 .TP
365 .B POSIX_SPAWN_USEVFORK
366 Since glibc 2.24, this flag has no effect.
367 On older implementations, setting this flag forces the
368 .B fork()
369 step to use
370 .BR vfork (2)
371 instead of
372 .BR fork (2).
373 The
374 .B _GNU_SOURCE
375 feature test macro must be defined to obtain the definition of this constant.
376 .TP
377 .BR POSIX_SPAWN_SETSID " (since glibc 2.26)"
378 If this flag is set,
379 the child process shall create a new session and become the session leader.
380 The child process shall also become the process group leader of the new process
381 group in the session (see
382 .BR setsid (2)).
383 The
384 .B _GNU_SOURCE
385 feature test macro must be defined to obtain the definition of this constant.
386 .\" This flag has been accepted in POSIX, see:
387 .\" http://austingroupbugs.net/view.php?id=1044
388 .\" and has been implemented since glibc 2.26
389 .\" commit daeb1fa2e1b33323e719015f5f546988bd4cc73b
390 .P
391 If
392 .I attrp
393 is NULL, then the default behaviors described above for each flag apply.
394 .\" mtk: I think we probably don't want to say the following, since it
395 .\" could lead people to do the wrong thing
396 .\" The POSIX standard tells you to call
397 .\" this function to de-initialize the attributes object pointed to by
398 .\" .I attrp
399 .\" when you are done with it;
400 .\" however, on Linux systems this operation is a no-op.
401 .P
402 The
403 .I file_actions
404 argument specifies a sequence of file operations
405 that are performed in the child process after
406 the general processing described above, and before it performs the
407 .BR exec (3).
408 If
409 .I file_actions
410 is NULL, then no special action is taken, and standard
411 .BR exec (3)
412 semantics apply\[em]file descriptors open before the exec
413 remain open in the new process,
414 except those for which the
415 .B FD_CLOEXEC
416 flag has been set.
417 File locks remain in place.
418 .P
419 If
420 .I file_actions
421 is not NULL, then it contains an ordered set of requests to
422 .BR open (2),
423 .BR close (2),
424 and
425 .BR dup2 (2)
426 files.
427 These requests are added to the
428 .I file_actions
429 by
430 .BR posix_spawn_file_actions_addopen (3),
431 .BR posix_spawn_file_actions_addclose (3),
432 and
433 .BR posix_spawn_file_actions_adddup2 (3).
434 The requested operations are performed in the order they were added to
435 .IR file_actions .
436 .\" FIXME . I think the following is best placed in the
437 .\" posix_spawn_file_actions_adddup2(3) page, and a similar statement is
438 .\" also needed in posix_spawn_file_actions_addclose(3)
439 .\" Note that you can specify file descriptors in
440 .\" .I posix_spawn_file_actions_adddup2 (3)
441 .\" which would not be usable if you called
442 .\" .BR dup2 (2)
443 .\" at that time--i.e., file descriptors that are opened or
444 .\" closed by the earlier operations
445 .\" added to
446 .\" .I file_actions .
447 .P
448 If any of the housekeeping actions fails
449 (due to bogus values being passed or other reasons why signal handling,
450 process scheduling, process group ID functions,
451 and file descriptor operations might fail),
452 the child process exits with exit value 127.
453 .SS exec() step
454 Once the child has successfully forked and performed
455 all requested pre-exec steps,
456 the child runs the requested executable.
457 .P
458 The child process takes its environment from the
459 .I envp
460 argument, which is interpreted as if it had been passed to
461 .BR execve (2).
462 The arguments to the created process come from the
463 .I argv
464 argument, which is processed as for
465 .BR execve (2).
466 .SH RETURN VALUE
467 Upon successful completion,
468 .BR posix_spawn ()
469 and
470 .BR posix_spawnp ()
471 place the PID of the child process in
472 .IR pid ,
473 and return 0.
474 If there is an error during the
475 .B fork()
476 step,
477 then no child is created,
478 the contents of
479 .I *pid
480 are unspecified,
481 and these functions return an error number as described below.
482 .P
483 Even when these functions return a success status,
484 the child process may still fail for a plethora of reasons related to its
485 pre-\fBexec\fR() initialization.
486 In addition, the
487 .BR exec (3)
488 may fail.
489 In all of these cases, the child process will exit with the exit value of 127.
490 .SH ERRORS
491 The
492 .BR posix_spawn ()
493 and
494 .BR posix_spawnp ()
495 functions fail only in the case where the underlying
496 .BR fork (2),
497 .BR vfork (2),
498 or
499 .BR clone (2)
500 call fails; in these cases, these functions return an error number,
501 which will be one of the errors described for
502 .BR fork (2),
503 .BR vfork (2),
504 or
505 .BR clone (2).
506 .P
507 In addition, these functions fail if:
508 .TP
509 .B ENOSYS
510 Function not supported on this system.
511 .SH STANDARDS
512 POSIX.1-2008.
513 .SH HISTORY
514 glibc 2.2.
515 POSIX.1-2001.
516 .\" FIXME . This piece belongs in spawnattr_setflags(3)
517 .\" The
518 .\" .B POSIX_SPAWN_USEVFORK
519 .\" flag is a GNU extension; the
520 .\" .B _GNU_SOURCE
521 .\" feature test macro must be defined (before including any header files)
522 .\" to obtain the definition of this constant.
523 .SH NOTES
524 The housekeeping activities in the child are controlled by
525 the objects pointed to by
526 .I attrp
527 (for non-file actions) and
528 .I file_actions
529 In POSIX parlance, the
530 .I posix_spawnattr_t
531 and
532 .I posix_spawn_file_actions_t
533 data types are referred to as objects,
534 and their elements are not specified by name.
535 Portable programs should initialize these objects using
536 only the POSIX-specified functions.
537 (In other words,
538 although these objects may be implemented as structures containing fields,
539 portable programs must avoid dependence on such implementation details.)
540 .P
541 According to POSIX, it is unspecified whether fork handlers established with
542 .BR pthread_atfork (3)
543 are called when
544 .BR posix_spawn ()
545 is invoked.
546 Since glibc 2.24, the fork handlers are not executed in any case.
547 .\" Tested on glibc 2.12
548 On older implementations,
549 fork handlers are called only if the child is created using
550 .BR fork (2).
551 .P
552 There is no "posix_fspawn" function (i.e., a function that is to
553 .BR posix_spawn ()
554 as
555 .BR fexecve (3)
556 is to
557 .BR execve (2)).
558 However, this functionality can be obtained by specifying the
559 .I path
560 argument as one of the files in the caller's
561 .I /proc/self/fd
562 directory.
563 .SH BUGS
564 POSIX.1 says that when
565 .B POSIX_SPAWN_SETSCHEDULER
566 is specified in
567 .IR spawn-flags ,
568 then the
569 .B POSIX_SPAWN_SETSCHEDPARAM
570 (if present) is ignored.
571 However, before glibc 2.14, calls to
572 .BR posix_spawn ()
573 failed with an error if
574 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12052
575 .B POSIX_SPAWN_SETSCHEDULER
576 was specified without also specifying
577 .BR POSIX_SPAWN_SETSCHEDPARAM .
578 .SH EXAMPLES
579 The program below demonstrates the use of various functions in the
580 POSIX spawn API.
581 The program accepts command-line attributes that can be used
582 to create file actions and attributes objects.
583 The remaining command-line arguments are used as the executable name
584 and command-line arguments of the program that is executed in the child.
585 .P
586 In the first run, the
587 .BR date (1)
588 command is executed in the child, and the
589 .BR posix_spawn ()
590 call employs no file actions or attributes objects.
591 .P
592 .in +4n
593 .EX
594 $ \fB./a.out date\fP
595 PID of child: 7634
596 Tue Feb 1 19:47:50 CEST 2011
597 Child status: exited, status=0
598 .EE
599 .in
600 .P
601 In the next run, the
602 .I \-c
603 command-line option is used to create a file actions object that closes
604 standard output in the child.
605 Consequently,
606 .BR date (1)
607 fails when trying to perform output and exits with a status of 1.
608 .P
609 .in +4n
610 .EX
611 $ \fB./a.out \-c date\fP
612 PID of child: 7636
613 date: write error: Bad file descriptor
614 Child status: exited, status=1
615 .EE
616 .in
617 .P
618 In the next run, the
619 .I \-s
620 command-line option is used to create an attributes object that
621 specifies that all (blockable) signals in the child should be blocked.
622 Consequently, trying to kill child with the default signal sent by
623 .BR kill (1)
624 (i.e.,
625 .BR SIGTERM )
626 fails, because that signal is blocked.
627 Therefore, to kill the child,
628 .B SIGKILL
629 is necessary
630 .RB ( SIGKILL
631 can't be blocked).
632 .P
633 .in +4n
634 .EX
635 $ \fB./a.out \-s sleep 60 &\fP
636 [1] 7637
637 $ PID of child: 7638
638 .P
639 $ \fBkill 7638\fP
640 $ \fBkill \-KILL 7638\fP
641 $ Child status: killed by signal 9
642 [1]+ Done ./a.out \-s sleep 60
643 .EE
644 .in
645 .P
646 When we try to execute a nonexistent command in the child, the
647 .BR exec (3)
648 fails and the child exits with a status of 127.
649 .P
650 .in +4n
651 .EX
652 $ \fB./a.out xxxxx
653 PID of child: 10190
654 Child status: exited, status=127
655 .EE
656 .in
657 .SS Program source
658 \&
659 .\" SRC BEGIN (posix_spawn.c)
660 .EX
661 #include <errno.h>
662 #include <spawn.h>
663 #include <stdint.h>
664 #include <stdio.h>
665 #include <stdlib.h>
666 #include <string.h>
667 #include <unistd.h>
668 #include <wait.h>
669 \&
670 #define errExit(msg) do { perror(msg); \e
671 exit(EXIT_FAILURE); } while (0)
672 \&
673 #define errExitEN(en, msg) \e
674 do { errno = en; perror(msg); \e
675 exit(EXIT_FAILURE); } while (0)
676 \&
677 char **environ;
678 \&
679 int
680 main(int argc, char *argv[])
681 {
682 pid_t child_pid;
683 int s, opt, status;
684 sigset_t mask;
685 posix_spawnattr_t attr;
686 posix_spawnattr_t *attrp;
687 posix_spawn_file_actions_t file_actions;
688 posix_spawn_file_actions_t *file_actionsp;
689 \&
690 /* Parse command\-line options, which can be used to specify an
691 attributes object and file actions object for the child. */
692 \&
693 attrp = NULL;
694 file_actionsp = NULL;
695 \&
696 while ((opt = getopt(argc, argv, "sc")) != \-1) {
697 switch (opt) {
698 case \[aq]c\[aq]: /* \-c: close standard output in child */
699 \&
700 /* Create a file actions object and add a "close"
701 action to it. */
702 \&
703 s = posix_spawn_file_actions_init(&file_actions);
704 if (s != 0)
705 errExitEN(s, "posix_spawn_file_actions_init");
706 \&
707 s = posix_spawn_file_actions_addclose(&file_actions,
708 STDOUT_FILENO);
709 if (s != 0)
710 errExitEN(s, "posix_spawn_file_actions_addclose");
711 \&
712 file_actionsp = &file_actions;
713 break;
714 \&
715 case \[aq]s\[aq]: /* \-s: block all signals in child */
716 \&
717 /* Create an attributes object and add a "set signal mask"
718 action to it. */
719 \&
720 s = posix_spawnattr_init(&attr);
721 if (s != 0)
722 errExitEN(s, "posix_spawnattr_init");
723 s = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK);
724 if (s != 0)
725 errExitEN(s, "posix_spawnattr_setflags");
726 \&
727 sigfillset(&mask);
728 s = posix_spawnattr_setsigmask(&attr, &mask);
729 if (s != 0)
730 errExitEN(s, "posix_spawnattr_setsigmask");
731 \&
732 attrp = &attr;
733 break;
734 }
735 }
736 \&
737 /* Spawn the child. The name of the program to execute and the
738 command\-line arguments are taken from the command\-line arguments
739 of this program. The environment of the program execed in the
740 child is made the same as the parent\[aq]s environment. */
741 \&
742 s = posix_spawnp(&child_pid, argv[optind], file_actionsp, attrp,
743 &argv[optind], environ);
744 if (s != 0)
745 errExitEN(s, "posix_spawn");
746 \&
747 /* Destroy any objects that we created earlier. */
748 \&
749 if (attrp != NULL) {
750 s = posix_spawnattr_destroy(attrp);
751 if (s != 0)
752 errExitEN(s, "posix_spawnattr_destroy");
753 }
754 \&
755 if (file_actionsp != NULL) {
756 s = posix_spawn_file_actions_destroy(file_actionsp);
757 if (s != 0)
758 errExitEN(s, "posix_spawn_file_actions_destroy");
759 }
760 \&
761 printf("PID of child: %jd\en", (intmax_t) child_pid);
762 \&
763 /* Monitor status of the child until it terminates. */
764 \&
765 do {
766 s = waitpid(child_pid, &status, WUNTRACED | WCONTINUED);
767 if (s == \-1)
768 errExit("waitpid");
769 \&
770 printf("Child status: ");
771 if (WIFEXITED(status)) {
772 printf("exited, status=%d\en", WEXITSTATUS(status));
773 } else if (WIFSIGNALED(status)) {
774 printf("killed by signal %d\en", WTERMSIG(status));
775 } else if (WIFSTOPPED(status)) {
776 printf("stopped by signal %d\en", WSTOPSIG(status));
777 } else if (WIFCONTINUED(status)) {
778 printf("continued\en");
779 }
780 } while (!WIFEXITED(status) && !WIFSIGNALED(status));
781 \&
782 exit(EXIT_SUCCESS);
783 }
784 .EE
785 .\" SRC END
786 .SH SEE ALSO
787 .nh \" Disable hyphenation
788 .ad l
789 .BR close (2),
790 .BR dup2 (2),
791 .BR execl (2),
792 .BR execlp (2),
793 .BR fork (2),
794 .BR open (2),
795 .BR sched_setparam (2),
796 .BR sched_setscheduler (2),
797 .BR setpgid (2),
798 .BR setuid (2),
799 .BR sigaction (2),
800 .BR sigprocmask (2),
801 .BR posix_spawn_file_actions_addclose (3),
802 .BR posix_spawn_file_actions_adddup2 (3),
803 .BR posix_spawn_file_actions_addopen (3),
804 .BR posix_spawn_file_actions_destroy (3),
805 .BR posix_spawn_file_actions_init (3),
806 .BR posix_spawnattr_destroy (3),
807 .BR posix_spawnattr_getflags (3),
808 .BR posix_spawnattr_getpgroup (3),
809 .BR posix_spawnattr_getschedparam (3),
810 .BR posix_spawnattr_getschedpolicy (3),
811 .BR posix_spawnattr_getsigdefault (3),
812 .BR posix_spawnattr_getsigmask (3),
813 .BR posix_spawnattr_init (3),
814 .BR posix_spawnattr_setflags (3),
815 .BR posix_spawnattr_setpgroup (3),
816 .BR posix_spawnattr_setschedparam (3),
817 .BR posix_spawnattr_setschedpolicy (3),
818 .BR posix_spawnattr_setsigdefault (3),
819 .BR posix_spawnattr_setsigmask (3),
820 .BR pthread_atfork (3),
821 .IR <spawn.h> ,
822 Base Definitions volume of POSIX.1-2001,
823 .I http://www.opengroup.org/unix/online.html