Sun Microsystems, Inc. gratefully acknowledges The Open Group for
permission to reproduce portions of its copyrighted documentation.
Original documentation from The Open Group can be obtained online at
http://www.opengroup.org/bookstore/.
The Institute of Electrical and Electronics Engineers and The Open
Group, have given us permission to reprint portions of their
documentation.
In the following statement, the phrase ``this text'' refers to portions
of the system documentation.
Portions of this text are reprinted and reproduced in electronic form
in the SunOS Reference Manual, from IEEE Std 1003.1, 2004 Edition,
Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6,
Copyright (C) 2001-2004 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy
between these versions and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html.
This notice shall appear on any product containing this material.
The contents of this file are subject to the terms of the
Common Development and Distribution License (the "License").
You may not use this file except in compliance with the License.
You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
or http://www.opensolaris.org/os/licensing.
See the License for the specific language governing permissions
and limitations under the License.
When distributing Covered Code, include this CDDL HEADER in each
file and include the License file at usr/src/OPENSOLARIS.LICENSE.
If applicable, add the following below this CDDL HEADER, with the
fields enclosed by brackets "[]" replaced with your own identifying
information: Portions Copyright [yyyy] [name of copyright owner]
Copyright 1989 AT&T
Portions Copyright (c) 1992, X/Open Company Limited. All Rights Reserved.
Copyright (c) 2007, Sun Microsystems, Inc. All Rights Reserved.
#include <sys/types.h> #include <sys/wait.h> pid_t waitpid(pid_t pid, int *stat_loc, int options);
The waitpid() function will suspend execution of the calling thread until status information for one of its terminated child processes is available, or until delivery of a signal whose action is either to execute a signal-catching function or to terminate the process. If more than one thread is suspended in waitpid(), wait(3C), or waitid(2) awaiting termination of the same process, exactly one thread will return the process status at the time of the target process termination. If status information is available prior to the call to waitpid(), return will be immediate.
The pid argument specifies a set of child processes for which status is requested, as follows:
If pid is less than (pid_t)-1, status is requested for any child process whose process group ID is equal to the absolute value of pid.
If pid is equal to (pid_t)-1, status is requested for any child process.
If pid is equal to (pid_t)0 status is requested for any child process whose process group ID is equal to that of the calling process.
If pid is greater than (pid_t)0, it specifies the process ID of the child process for which status is requested.
One instance of a SIGCHLD signal is queued for each child process whose status has changed. If waitpid() returns because the status of a child process is available, and WNOWAIT was not specified in options, any pending SIGCHLD signal associated with the process ID of that child process is discarded. Any other pending SIGCHLD signals remain pending.
If the calling process has SA_NOCLDWAIT set or has SIGCHLD set to SIG_IGN and the process has no unwaited children that were transformed into zombie processes, it will block until all of its children terminate, and waitpid() will fail and set errno to ECHILD.
If waitpid() returns because the status of a child process is available, then that status may be evaluated with the macros defined by wait.h(3HEAD) If the calling process had specified a non-zero value of stat_loc, the status of the child process will be stored in the location pointed to by stat_loc.
The options argument is constructed from the bitwise-inclusive OR of zero or more of the following flags, defined in the header <sys/wait.h>: WCONTINUED
The status of any continued child process specified by pid, whose status has not been reported since it continued, is also reported to the calling process.
The waitpid() function will not suspend execution of the calling process if status is not immediately available for one of the child processes specified by pid.
Keep the process whose status is returned in stat_loc in a waitable state. The process may be waited for again with identical results.
The status of any child processes specified by pid that are stopped, and whose status has not yet been reported since they stopped, is also reported to the calling process. WSTOPPED is a synonym for WUNTRACED.
If waitpid() returns because the status of a child process is available, it returns a value equal to the process ID of the child process for which status is reported. If waitpid() returns due to the delivery of a signal to the calling process, -1 is returned and errno is set to EINTR. If waitpid() was invoked with WNOHANG set in options, it has at least one child process specified by pid for which status is not available, and status is not available for any process specified by pid, then 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.
The waitpid() function will fail if: ECHILD
The process or process group specified by pid does not exist or is not a child of the calling process or can never be in the states specified by options.
The waitpid() function was interrupted due to the receipt of a signal sent by the calling process.
An invalid value was specified for options.
With options equal to 0 and pid equal to (pid_t)-1, waitpid() is identical to wait(3C). The waitpid() function is implemented as a call to the more general waitid(2) function.
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| Interface Stability Committed |
| MT-Level Async-Signal-Safe |
| Standard See standards(5). |
Intro(2), exec(2), exit(2), fork(2), pause(2), sigaction(2), ptrace(3C), signal(3C), siginfo.h(3HEAD), wait(3C), wait.h(3HEAD), attributes(5), standards(5)