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38 .Nd wait for processes to change status
44 .Fn wait "int *status"
46 .Fn waitpid "pid_t wpid" "int *status" "int options"
49 .Fn waitid "idtype_t idtype" "id_t id" "siginfo_t *info" "int options"
53 .Fn wait3 "int *status" "int options" "struct rusage *rusage"
55 .Fn wait4 "pid_t wpid" "int *status" "int options" "struct rusage *rusage"
58 .Fa "idtype_t idtype" "id_t id"
61 .Fa "struct __wrusage *wrusage"
62 .Fa "siginfo_t *infop"
67 function suspends execution of its calling thread until
69 information is available for a child process
70 or a signal is received.
71 On return from a successful
76 area contains information about the process that reported a status change
83 system calls provide a more general interface for programs
84 that need to wait for specific child processes,
85 that need resource utilization statistics accumulated by child processes,
86 or that require options.
87 The other wait functions are implemented using either
94 function is the most general function in this family and its distinct
97 All of the desired process statuses to be waited on must be explicitly
106 functions all implicitly wait for exited and trapped processes,
111 functions require the corresponding
115 flags to be explicitly specified.
116 This allows waiting for processes which have experienced other
117 status changes without having to also handle the exit status from
118 terminated processes.
124 argument which points to a structure defined as:
127 struct rusage wru_self;
128 struct rusage wru_children;
132 This allows the calling process to collect resource usage statistics
133 from both its own child process as well as from its grand children.
134 When no resource usage statistics are needed this pointer can be
146 the structure is filled with the same data as for a
148 signal delivered when the process changed state.
150 The set of child processes to be queried is specified by the arguments
158 arguments support many other types of
159 identifiers in addition to process IDs and process group IDs.
160 .Bl -bullet -offset indent
169 wait for the child process with a process ID equal to
179 wait for the child process with a process group ID equal to
189 wait for any child process and the
205 wait for any child process in the same process group as the caller.
208 Non-standard identifier types supported by this
214 .Bl -tag -width P_JAILID
216 Wait for processes whose effective user ID is equal to
219 Wait for processes whose effective group ID is equal to
222 Wait for processes whose session ID is equal to
224 .\" This is just how sessions work, not sure this needs to be documented here
225 If the child process started its own session,
226 its session ID will be the same as its process ID.
227 Otherwise the session ID of a child process will match the caller's session ID.
229 Waits for processes within a jail whose jail identifier is equal to
237 functions, the single
239 argument specifies the set of child processes for which to wait.
240 .Bl -bullet -offset indent
244 is -1, the call waits for any child process.
249 the call waits for any child process in the process group of the caller.
253 is greater than zero, the call waits for the process with process ID
258 is less than -1, the call waits for any process whose process group ID
259 equals the absolute value of
265 argument is defined below.
269 argument contains the bitwise OR of any of the following options.
270 .Bl -tag -width WCONTINUED
272 Report the status of selected processes that
273 have continued from a job control stop by receiving a
278 there are no processes wishing to report status.
280 Report the status of selected processes which are stopped due to a
281 .Dv SIGTTIN , SIGTTOU , SIGTSTP ,
289 Report the status of selected processes which are being traced via
291 and have trapped or reached a breakpoint.
292 This flag is implicitly set for the functions
303 functions, the flag has to be explicitly included in
305 if status reports from trapped processes are expected.
307 Report the status of selected processes which have terminated.
308 This flag is implicitly set for the functions
319 functions, the flag has to be explicitly included in
321 if status reports from terminated processes are expected.
323 Keep the process whose status is returned in a waitable state.
324 The process may be waited for again after this call completes.
331 functions, at least one of the options
339 Otherwise there will be no events for the call to report.
340 To avoid hanging indefinitely in such a case these functions
348 is non-NULL, a summary of the resources used by the terminated
349 process and all its children is returned.
353 is non-NULL, separate summaries are returned for the resources used
354 by the terminated process and the resources used by all its children.
360 structure is returned with the
366 field set to the process ID of the process reporting status.
367 For the exited process, the
371 structure contains the full 32 bit exit status passed to
375 argument of other calls only returns 8 lowest bits of the exit status.
379 option is specified and no processes
380 wish to report status,
389 Checking these fields is the only way to know if a status change was reported.
393 option is specified and no processes
394 wish to report status,
418 function is identical to
433 function is identical to
446 The following macros may be used to test the current status of the process.
447 Exactly one of the following four macros will evaluate to a non-zero
451 .It Fn WIFCONTINUED status
452 True if the process has not terminated, and
453 has continued after a job control stop.
454 This macro can be true only if the wait call specified the
457 .It Fn WIFEXITED status
458 True if the process terminated normally by a call to
462 .It Fn WIFSIGNALED status
463 True if the process terminated due to receipt of a signal.
464 .It Fn WIFSTOPPED status
465 True if the process has not terminated, but has stopped and can be restarted.
466 This macro can be true only if the wait call specified the
469 or if the child process is being traced (see
473 Depending on the values of those macros, the following macros
474 produce the remaining status information about the child process:
476 .It Fn WEXITSTATUS status
479 is true, evaluates to the low-order 8 bits
480 of the argument passed to
485 .It Fn WTERMSIG status
487 .Fn WIFSIGNALED status
488 is true, evaluates to the number of the signal
489 that caused the termination of the process.
490 .It Fn WCOREDUMP status
492 .Fn WIFSIGNALED status
493 is true, evaluates as true if the termination
494 of the process was accompanied by the creation of a core file
495 containing an image of the process when the signal was received.
496 .It Fn WSTOPSIG status
498 .Fn WIFSTOPPED status
499 is true, evaluates to the number of the signal
500 that caused the process to stop.
505 for a list of termination signals.
506 A status of 0 indicates normal termination.
508 If a parent process terminates without
509 waiting for all of its child processes to terminate,
510 the remaining child processes are re-assigned to the reaper
511 of the exiting process as the parent, see
513 .Dv PROC_REAP_ACQUIRE .
514 If no specific reaper was assigned, the process with ID 1, the init process,
515 becomes the parent of the orphaned children by default.
517 If a signal is caught while any of the
520 the call may be interrupted or restarted when the signal-catching routine
522 depending on the options in effect for the signal;
528 The implementation queues one
530 signal for each child process whose
531 status has changed; if
533 returns because the status of a child process is available, the pending
534 SIGCHLD signal associated with the process ID of the child process will
538 signals remain pending.
544 returns because the status of a child process is available, the pending
546 signal will be cleared unless another status of the child process
551 returns due to a stopped, continued,
552 or terminated child process, the process ID of the child
553 is returned to the calling process.
554 Otherwise, a value of \-1
557 is set to indicate the error.
565 returns due to a stopped, continued,
566 or terminated child process, the process ID of the child
567 is returned to the calling process.
568 If there are no children not previously awaited,
575 is specified and there are
576 no stopped, continued or exited children,
578 If an error is detected or a caught signal aborts the call,
582 is set to indicate the error.
586 returns because one or more processes have a state change to report,
588 If an error is detected,
592 is set to indicate the error.
595 is specified and there are
596 no stopped, continued or exited children,
604 must be checked against zero to determine if a process reported status.
608 family of functions will not return a child process created with
610 unless specifically directed to do so by specifying its process ID.
615 will fail and return immediately if:
618 The calling process has no existing unwaited-for
621 No status from the terminated child process is available
622 because the calling process has asked the system to discard
623 such status by ignoring the signal
633 argument points to an illegal address.
634 (May not be detected before exit of a child process.)
636 The call was interrupted by a caught signal,
637 or the signal did not have the
641 An invalid value was specified for
647 do not specify a valid set of processes.
662 functions are defined by POSIX;
667 are not specified by POSIX.
671 is an extension to the POSIX interface.
673 The ability to use the
679 only permits this flag with