.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved. The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\" @(#)wait.2 6.3 (Berkeley) %G%
wait, waitpid, wait4, wait3 \- wait for process to terminate
pid = waitpid(wpid, status, options)
#include <sys/resource.h>
pid = wait4(wpid, status, options, rusage)
pid = wait3(status, options, rusage)
causes its caller to delay until a signal is received or
If any child has died since the last
return is immediate, returning the process id and
exit status of one of the terminated
If there are no children, return is immediate with
On return from a successful
area contains termination information about the process that exited
call provides a more general interface for programs
that wish to wait for certain child processes,
that wish resource utilization statistics accummulated by child processes,
The other wait functions are implemented using
parameter specifies the set of child processes for which to wait.
is \-1, the call waits for any child process.
the call waits for any child process in the process group of the caller.
is greater than zero, the call waits for the process with process id
is less than \-1, the call waits for any process whose process group id
equals the absolute value of
parameter is defined below. The
parameter contains the bitwise OR of any of the following options.
is used to indicate that the call should not block if
there are no processes that wish to report status.
If the WUNTRACED option is set,
children of the current process that are stopped
due to a SIGTTIN, SIGTTOU, SIGTSTP, or SIGSTOP signal also have
is non-zero, a summary of the resources used by the terminated
children is returned (this information is currently not available
When the WNOHANG option is specified and no processes
The following macros may be used to test the manner of exit of the process.
One of the first three macros will evaluate to a non-zero (true) value:
True if the process terminated normally by a call to
True if the process terminated due to receipt of a signal.
True if the process has not terminated, but has stopped and can be restarted.
This macro can be true only if the wait call specified the
or if the child process is being traced (see
Depending on the values of those macros, the following macros
produce the remaining status information about the child process:
If WIFEXITED(status) is true, evaluates to the low-order 8 bits
of the argument passed to
If WIFSIGNALED(status) is true, evaluates to the number of the signal
that caused the termination of the process.
If WIFSIGNALED(status) is true, evaluates as true if the termination
of the process was accompanied by the creation of a core file
containing an image of the process when the signal was received.
If WIFSTOPPED(status) is true, evaluates to the number of the signal
that caused the process to stop.
for a list of termination signals.
A status of 0 indicates normal termination.
If the parent process terminates without
the initialization process
If a signal is caught while any of the
the call may be interrupted or restarted when the signal-catching routine
depending on the options in effect for the signal;
If \fIwait\fP returns due to a stopped
or terminated child process, the process ID of the child
is returned to the calling process. Otherwise, a value of \-1
is returned and \fIerrno\fP is set to indicate the error.
or terminated child process, the process ID of the child
is returned to the calling process.
If there are no children not previously awaited,
Otherwise, if WNOHANG is specified and there are
no stopped or exited children,
If an error is detected or a caught signal aborts the call,
is returned and \fIerrno\fP is set to indicate the error.
will fail and return immediately if one or more of the following
The calling process has no existing unwaited-for
The \fIstatus\fP or \fIrusage\fP arguments point to an illegal address.
(May not be detected before exit of a child process.)
The call was interrupted by a caught signal,
or the signal did not have the SA_RESTART flag set.
functions are defined by POSIX;
are not specified by POSIX.
and the ability to restart a pending
call are extensions to the POSIX interface.