wait(3C)						   Standard C Library Functions 						  wait(3C)

NAME

       wait - wait for child process to stop or terminate

SYNOPSIS

       #include <sys/types.h>
       #include <sys/wait.h>

       pid_t wait(int *stat_loc);

DESCRIPTION

       The  wait()  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 wait(), waitpid(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  wait(),  return
       will be immediate.

       If  wait()  returns  because  the  status  of  a child process is available, it returns the process ID of the child process. If the calling
       process specified a non-zero value for stat_loc, the status of the child process is stored in the location pointed  to  by  stat_loc.  That
       status can be evaluated with the macros described on the wait.h(3HEAD) manual page.

       In the following, status is the object pointed to by stat_loc:

	 o  If	the  child process terminated due to an _exit() call, the low order 8 bits of status will be 0 and the high order 8 bits will con-
	    tain the low order 7 bits of the argument that the child process passed to _exit(); see exit(2).

	 o  If the child process terminated due to a signal, the high order 8 bits of status will be 0 and the low order 7bits	will  contain  the
	    number  of the signal that caused the termination. In addition, if	WCOREFLG is set, a "core image" will have been	produced; see sig-
	    nal.h(3HEAD) and wait.h(3HEAD).

       One instance of a SIGCHLD signal is queued for each child process whose status has changed. If wait() returns because the status of a child
       process	is  available,	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 wait() will fail and set errno to ECHILD.

       If  a parent process terminates without waiting for its child processes to terminate, the parent process ID of each child process is set to
       1, with the initialization process inheriting the child processes; see intro(2).

RETURN VALUES

       When wait() returns due to a terminated child process, the process ID of the child is returned to the calling  process.	Otherwise,  -1	is
       returned and errno is set to indicate the error.

ERRORS

       The wait() function will fail if:

       ECHILD	       The calling process has no existing unwaited-for child processes.

       EINTR	       The function was interrupted by a signal.

USAGE

       Since  wait()  blocks  on  a  stopped  child,  a calling process wanting to see the return results of such a call should use waitpid(3C) or
       waitid(2) instead of wait(). The wait() function is implemented as a call to waitpid(-1, stat_loc, 0).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       intro(2),  exec(2),  exit(2),  fork(2),	pause(2),  waitid(2),  ptrace(3C),  signal(3C),   signal.h(3HEAD),   waitpid(3C),   wait.h(3HEAD),
       attributes(5)

SunOS 5.10							    9 Jun 2004								  wait(3C)