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WAIT(3)								       WAIT(3)

NAME
       await, awaitnohang, awaitfor, wait, waitnohang, waitfor,	waitpid	- wait
       for a process to	exit

SYNOPSIS
       #include	<u.h>
       #include	<libc.h>

       Waitmsg*	 wait(void)

       Waitmsg*	 waitnohang(void)

       Waitmsg*	 waitfor(int pid)

       int	 waitpid(void)

       int	 await(char *s,	int n)

       int	 awaitnohang(char *s, int n)

       int	 awaitfor(int pid, char	*s, int	n)

DESCRIPTION
       Wait causes a process to	wait for any child process  (see  fork(2)  and
       rfork(3))  to exit.  It returns a Waitmsg holding information about the
       exited child.  A	Waitmsg	has this structure:

	      typedef struct Waitmsg {	     int pid;		   /* of loved
	      one */	   ulong time[3];	 /* of loved one & descendants
	      */       char *msg; } Waitmsg;

       Pid is the child's process id.  The time	array contains	the  time  the
       child  and its descendants spent	in user	code, the time spent in	system
       calls, and the child's elapsed real time, all in	units of milliseconds.
       Msg  contains  the message that the child specified in exits(3).	 For a
       normal exit, msg[0] is zero, otherwise msg is the exit string  prefixed
       by the process name, a blank, the process id, and a colon.

       If  there  are  no more children	to wait	for, wait returns immediately,
       with return value nil.

       The Waitmsg structure is	allocated by malloc(3)	and  should  be	 freed
       after use.  For programs	that only need the pid of the exiting program,
       waitpid returns just the	pid and	discards the rest of the  information.

       Waitnohang  is  like wait but does not block if there are no more chil-
       dren to wait for.  Instead it returns immediately and sets errstr.

       Waitfor is like wait but	waits for a particular pid.

       The underlying calls are	await, awaitnohang, and	awaitfor,  which  fill
       in the n-byte buffer s with a textual representation of the pid,	times,
       and exit	string.	 There is no terminal NUL.  The	return	value  is  the
       length, in bytes, of the	data.

       The  filled-in  buffer may be parsed (after appending a NUL) using tok-
       enize (see getfields(3)); the resulting fields are, in order, pid,  the
       three times, and	the exit string, which will be '' for normal exit.  If
       the representation is longer than n bytes, it is	truncated but, if pos-
       sible,  properly	 formatted.   The information that does	not fit	in the
       buffer is discarded, so a subsequent call  to  await  will  return  the
       information  about  the	next  exiting  child, not the remainder	of the
       truncated message.  In other words, each	 call  to  await  returns  the
       information  about  one	child,	blocking  if necessary if no child has
       exited.	If the calling process has no living children,	await  returns
       -1.

SOURCE
       /usr/local/plan9/src/lib9/wait.c

       /usr/local/plan9/src/lib9/await.c

SEE ALSO
       rfork(3), exits(3),

DIAGNOSTICS
       These routines set errstr.

BUGS
       To  avoid name conflicts	with the underlying system, wait, waitpid, and
       waitfor are preprocessor	 macros	 defined  as  p9wait,  p9waitpid,  and
       p9waitfor; see intro(3).

								       WAIT(3)

NAME | SYNOPSIS | DESCRIPTION | SOURCE | SEE ALSO | DIAGNOSTICS | BUGS

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