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WAITID
Section: POSIX Programmer's Manual (3P)
Updated: 2003
Index
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PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
NAME
waitid - wait for a child process to change state
SYNOPSIS
#include <sys/wait.h>
int waitid(idtype_t idtype, id_t id, siginfo_t
*infop, int
options);
DESCRIPTION
The waitid() function shall suspend the calling thread until
one child of the process containing the calling thread
changes state. It records the current state of a child in the structure
pointed to by infop. If a child process changed
state prior to the call to waitid(), waitid() shall return
immediately. If more than one thread is suspended in wait()
or waitpid() waiting for termination
of the same process, exactly one thread shall return the process status
at the time of the target process termination.
The idtype and id arguments are used to specify which
children waitid() waits for.
If idtype is P_PID, waitid() shall wait for the child
with a process ID equal to (pid_t)id.
If idtype is P_PGID, waitid() shall wait for any child
with a process group ID equal to
(pid_t)id.
If idtype is P_ALL, waitid() shall wait for any children
and id is ignored.
The options argument is used to specify which state changes
waitid() shall wait for. It is formed by OR'ing
together one or more of the following flags:
- WEXITED
-
Wait for processes that have exited.
- WSTOPPED
-
Status shall be returned for any child that has stopped upon receipt
of a signal.
- WCONTINUED
-
Status shall be returned for any child that was stopped and has been
continued.
- WNOHANG
-
Return immediately if there are no children to wait for.
- WNOWAIT
-
Keep the process whose status is returned in infop in a waitable
state. This shall not affect the state of the process;
the process may be waited for again after this call completes.
The application shall ensure that the infop argument points
to a siginfo_t structure. If waitid() returns
because a child process was found that satisfied the conditions indicated
by the arguments idtype and options, then
the structure pointed to by infop shall be filled in by the
system with the status of the process. The si_signo
member shall always be equal to SIGCHLD.
RETURN VALUE
If WNOHANG was specified and there are no children to wait for, 0
shall be returned. If waitid() returns due to the
change of state of one of its children, 0 shall be returned. Otherwise,
-1 shall be returned and errno set to indicate the
error.
ERRORS
The waitid() function shall fail if:
- ECHILD
-
The calling process has no existing unwaited-for child processes.
- EINTR
-
The waitid() function was interrupted by a signal.
- EINVAL
-
An invalid value was specified for options, or idtype
and id specify an invalid set of processes.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
exec(), exit(), wait(), the Base Definitions
volume of IEEE Std 1003.1-2001, <sys/wait.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version 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 .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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