WAIT(2)			   Linux Programmer's Manual		       WAIT(2)

NAME
       wait, waitpid - wait for process termination

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

       pid_t wait(int *status);
       pid_t waitpid(pid_t pid, int *status, int options);

DESCRIPTION
       The  wait  function  suspends  execution of the current process until a
       child has exited, or until a signal is delivered	 whose	action	is  to
       terminate  the  current	process or to call a signal handling function.
       If a child has already exited by the time  of  the  call	 (a  so-called
       "zombie"	 process),  the	 function  returns  immediately.   Any	system
       resources used by the child are freed.

       The waitpid function suspends execution of the current process until  a
       child as specified by the pid argument has exited, or until a signal is
       delivered whose action is to terminate the current process or to call a
       signal  handling	 function.  If a child as requested by pid has already
       exited by the time of the call  (a  so-called  "zombie"	process),  the
       function	 returns  immediately.	Any system resources used by the child
       are freed.

       The value of pid can be one of:

       < -1   which means to wait for any child process whose process group ID
	      is equal to the absolute value of pid.

       -1     which  means  to	wait  for  any child process; this is the same
	      behaviour which wait exhibits.

       0      which means to wait for any child process whose process group ID
	      is equal to that of the calling process.

       > 0    which  means  to wait for the child whose process ID is equal to
	      the value of pid.

       The value of options is an OR of zero or more  of  the  following  con-
       stants:

       WNOHANG
	      which means to return immediately if no child has exited.

       WUNTRACED
	      which  means  to also return for children which are stopped, and
	      whose status has not been reported.

       (For Linux-only options, see below.)

       If status is not NULL, wait or waitpid store status information in  the
       location pointed to by status.

       This  status  can  be evaluated with the following macros (these macros
       take the stat buffer (an int) as an argument