RedHat 9 (Linux i386) - man page for wait3 (redhat section 2)

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WAIT4(2)			    Linux Programmer's Manual				 WAIT4(2)

NAME
       wait3, wait4 - wait for process termination, BSD style

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

       pid_t wait3(int *status, int options,
	     struct rusage *rusage);

       pid_t wait4(pid_t pid, int *status, int options,
	     struct rusage *rusage);

DESCRIPTION
       The  wait3 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 wait4 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 equivalent to calling wait3.

       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 a bitwise OR of zero or more of the following constants:

       WNOHANG
	      which means to return immediately if no child is there to be waited for.

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

       If status is not NULL, wait3 or wait4 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 -- not a pointer to the buffer!):

       WIFEXITED(status)
	      is non-zero if the child exited normally.

       WEXITSTATUS(status)
	      evaluates to the least significant eight bits of the return code of the child which
	      terminated,  which  may have been set as the argument to a call to exit() or as the
	      argument for a return statement in the main program.  This macro can only be evalu-
	      ated if WIFEXITED returned non-zero.

       WIFSIGNALED(status)
	      returns true if the child process exited because of a signal which was not caught.

       WTERMSIG(status)
	      returns  the  number of the signal that caused the child process to terminate. This
	      macro can only be evaluated if WIFSIGNALED returned non-zero.

       WIFSTOPPED(status)
	      returns true if the child process which caused the  return  is  currently  stopped;
	      this is only possible if the call was done using WUNTRACED.

       WSTOPSIG(status)
	      returns  the  number  of the signal which caused the child to stop.  This macro can
	      only be evaluated if WIFSTOPPED returned non-zero.

       If rusage is not NULL, the struct rusage as defined in <sys/resource.h> it points to  will
       be filled with accounting information.  See getrusage(2) for details.

RETURN VALUE
       The process ID of the child which exited, -1 on error (in particular, when no unwaited-for
       child processes of the specified kind exist) or zero if WNOHANG was used and no child  was
       available yet.  In the latter two cases errno will be set appropriately.

ERRORS
       ECHILD No unwaited-for child process as specified does exist.

       EINTR  if WNOHANG was not set and an unblocked signal or a SIGCHLD was caught.

NOTES
       Including  <sys/time.h>	is  not required these days, but increases portability.  (Indeed,
       <sys/resource.h> defines the rusage structure with fields of type struct  timeval  defined
       in <sys/time.h>.)

       The  prototype  for  these  functions  is only available if _BSD_SOURCE is defined (either
       explicitly, or implicitly, by not defining  _POSIX_SOURCE  or  compiling  with  the  -ansi
       flag).

CONFORMING TO
       SVr4, POSIX.1

SEE ALSO
       signal(2), getrusage(2), wait(2), signal(7)

Linux					    1997-06-23					 WAIT4(2)
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