345 lines
8.6 KiB
Groff
345 lines
8.6 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993, 1994
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)wait.2 8.2 (Berkeley) 4/19/94
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd November 12, 2005
|
|
.Dt WAIT 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm wait ,
|
|
.Nm waitpid ,
|
|
.Nm wait4 ,
|
|
.Nm wait3
|
|
.Nd wait for process termination
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/types.h
|
|
.In sys/wait.h
|
|
.Ft pid_t
|
|
.Fn wait "int *status"
|
|
.In sys/time.h
|
|
.In sys/resource.h
|
|
.Ft pid_t
|
|
.Fn waitpid "pid_t wpid" "int *status" "int options"
|
|
.Ft pid_t
|
|
.Fn wait3 "int *status" "int options" "struct rusage *rusage"
|
|
.Ft pid_t
|
|
.Fn wait4 "pid_t wpid" "int *status" "int options" "struct rusage *rusage"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn wait
|
|
function suspends execution of its calling process until
|
|
.Fa status
|
|
information is available for a terminated child process,
|
|
or a signal is received.
|
|
On return from a successful
|
|
.Fn wait
|
|
call,
|
|
the
|
|
.Fa status
|
|
area contains termination information about the process that exited
|
|
as defined below.
|
|
.Pp
|
|
The
|
|
.Fn wait4
|
|
system call provides a more general interface for programs
|
|
that need to wait for certain child processes,
|
|
that need resource utilization statistics accumulated by child processes,
|
|
or that require options.
|
|
The other wait functions are implemented using
|
|
.Fn wait4 .
|
|
.Pp
|
|
The
|
|
.Fa wpid
|
|
argument specifies the set of child processes for which to wait.
|
|
If
|
|
.Fa wpid
|
|
is -1, the call waits for any child process.
|
|
If
|
|
.Fa wpid
|
|
is 0,
|
|
the call waits for any child process in the process group of the caller.
|
|
If
|
|
.Fa wpid
|
|
is greater than zero, the call waits for the process with process id
|
|
.Fa wpid .
|
|
If
|
|
.Fa wpid
|
|
is less than -1, the call waits for any process whose process group id
|
|
equals the absolute value of
|
|
.Fa wpid .
|
|
.Pp
|
|
The
|
|
.Fa status
|
|
argument is defined below.
|
|
The
|
|
.Fa options
|
|
argument contains the bitwise OR of any of the following options.
|
|
The
|
|
.Dv WCONTINUED
|
|
option indicates that children of the current process that
|
|
have continued from a job control stop, by receiving a
|
|
.Dv SIGCONT
|
|
signal, should also have their status reported.
|
|
The
|
|
.Dv WNOHANG
|
|
option
|
|
is used to indicate that the call should not block if
|
|
there are no processes that wish to report status.
|
|
If the
|
|
.Dv WUNTRACED
|
|
option is set,
|
|
children of the current process that are stopped
|
|
due to a
|
|
.Dv SIGTTIN , SIGTTOU , SIGTSTP ,
|
|
or
|
|
.Dv SIGSTOP
|
|
signal also have
|
|
their status reported.
|
|
.Pp
|
|
If
|
|
.Fa rusage
|
|
is non-zero, a summary of the resources used by the terminated
|
|
process and all its
|
|
children is returned (this information is currently not available
|
|
for stopped or continued processes).
|
|
.Pp
|
|
When the
|
|
.Dv WNOHANG
|
|
option is specified and no processes
|
|
wish to report status,
|
|
.Fn wait4
|
|
returns a
|
|
process id
|
|
of 0.
|
|
.Pp
|
|
The
|
|
.Fn waitpid
|
|
function is identical to
|
|
.Fn wait4
|
|
with an
|
|
.Fa rusage
|
|
value of zero.
|
|
The older
|
|
.Fn wait3
|
|
call is the same as
|
|
.Fn wait4
|
|
with a
|
|
.Fa wpid
|
|
value of -1.
|
|
.Pp
|
|
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:
|
|
.Bl -tag -width Ds
|
|
.It Fn WIFCONTINUED status
|
|
True if the process has not terminated, and
|
|
has continued after a job control stop.
|
|
This macro can be true only if the wait call specified the
|
|
.Dv WCONTINUED
|
|
option).
|
|
.It Fn WIFEXITED status
|
|
True if the process terminated normally by a call to
|
|
.Xr _exit 2
|
|
or
|
|
.Xr exit 3 .
|
|
.It Fn WIFSIGNALED status
|
|
True if the process terminated due to receipt of a signal.
|
|
.It Fn WIFSTOPPED status
|
|
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
|
|
.Dv WUNTRACED
|
|
option
|
|
or if the child process is being traced (see
|
|
.Xr ptrace 2 ) .
|
|
.El
|
|
.Pp
|
|
Depending on the values of those macros, the following macros
|
|
produce the remaining status information about the child process:
|
|
.Bl -tag -width Ds
|
|
.It Fn WEXITSTATUS status
|
|
If
|
|
.Fn WIFEXITED status
|
|
is true, evaluates to the low-order 8 bits
|
|
of the argument passed to
|
|
.Xr _exit 2
|
|
or
|
|
.Xr exit 3
|
|
by the child.
|
|
.It Fn WTERMSIG status
|
|
If
|
|
.Fn WIFSIGNALED status
|
|
is true, evaluates to the number of the signal
|
|
that caused the termination of the process.
|
|
.It Fn WCOREDUMP status
|
|
If
|
|
.Fn 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.
|
|
.It Fn WSTOPSIG status
|
|
If
|
|
.Fn WIFSTOPPED status
|
|
is true, evaluates to the number of the signal
|
|
that caused the process to stop.
|
|
.El
|
|
.Sh NOTES
|
|
See
|
|
.Xr sigaction 2
|
|
for a list of termination signals.
|
|
A status of 0 indicates normal termination.
|
|
.Pp
|
|
If a parent process terminates without
|
|
waiting for all of its child processes to terminate,
|
|
the remaining child processes are assigned the parent
|
|
process 1 ID (the init process ID).
|
|
.Pp
|
|
If a signal is caught while any of the
|
|
.Fn wait
|
|
calls are pending,
|
|
the call may be interrupted or restarted when the signal-catching routine
|
|
returns,
|
|
depending on the options in effect for the signal;
|
|
see discussion of
|
|
.Dv SA_RESTART
|
|
in
|
|
.Xr sigaction 2 .
|
|
.Pp
|
|
The implementation queues one
|
|
.Dv SIGCHLD
|
|
signal for each child process whose
|
|
status has changed, if
|
|
.Fn wait
|
|
returns because the status of a child process is available, the pending
|
|
SIGCHLD signal associated with the process ID of the child process will
|
|
be discarded.
|
|
Any other pending
|
|
.Dv SIGCHLD
|
|
signals remain pending.
|
|
.Pp
|
|
If
|
|
.Dv SIGCHLD
|
|
is blocked,
|
|
.Fn wait
|
|
returns because the status of a child process is available, the pending
|
|
.Dv SIGCHLD
|
|
signal will be cleared unless another status of the child process
|
|
is available.
|
|
.Sh RETURN VALUES
|
|
If
|
|
.Fn wait
|
|
returns due to a stopped, continued,
|
|
or terminated child process, the process ID of the child
|
|
is returned to the calling process.
|
|
Otherwise, a value of \-1
|
|
is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Pp
|
|
If
|
|
.Fn wait4 ,
|
|
.Fn wait3 ,
|
|
or
|
|
.Fn waitpid
|
|
returns due to a stopped, continued,
|
|
or terminated child process, the process ID of the child
|
|
is returned to the calling process.
|
|
If there are no children not previously awaited,
|
|
-1 is returned with
|
|
.Va errno
|
|
set to
|
|
.Er ECHILD .
|
|
Otherwise, if
|
|
.Dv WNOHANG
|
|
is specified and there are
|
|
no stopped, continued or exited children,
|
|
0 is returned.
|
|
If an error is detected or a caught signal aborts the call,
|
|
a value of -1
|
|
is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
The
|
|
.Fn wait
|
|
function
|
|
will fail and return immediately if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ECHILD
|
|
The calling process has no existing unwaited-for
|
|
child processes.
|
|
.It Bq Er ECHILD
|
|
No status from the terminated child process is available
|
|
because the calling process has asked the system to discard
|
|
such status by ignoring the signal
|
|
.Dv SIGCHLD
|
|
or setting the flag
|
|
.Dv SA_NOCLDWAIT
|
|
for that signal.
|
|
.It Bq Er EFAULT
|
|
The
|
|
.Fa status
|
|
or
|
|
.Fa rusage
|
|
argument points to an illegal address.
|
|
(May not be detected before exit of a child process.)
|
|
.It Bq Er EINTR
|
|
The call was interrupted by a caught signal,
|
|
or the signal did not have the
|
|
.Dv SA_RESTART
|
|
flag set.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr _exit 2 ,
|
|
.Xr ptrace 2 ,
|
|
.Xr sigaction 2 ,
|
|
.Xr exit 3 ,
|
|
.Xr siginfo 3
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn wait
|
|
and
|
|
.Fn waitpid
|
|
functions are defined by POSIX;
|
|
.Fn wait4
|
|
and
|
|
.Fn wait3
|
|
are not specified by POSIX.
|
|
The
|
|
.Fn WCOREDUMP
|
|
macro
|
|
and the ability to restart a pending
|
|
.Fn wait
|
|
call are extensions to the POSIX interface.
|
|
.Sh HISTORY
|
|
The
|
|
.Fn wait
|
|
function appeared in
|
|
.At v6 .
|