WAITID(3P)						     POSIX Programmer's Manual							WAITID(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing 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 Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								WAITID(3P)