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WAIT3(3C)							     WAIT3(3C)

NAME
       wait3, wait4 - wait for process to terminate or stop

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

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

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

DESCRIPTION
       The  wait3()  function  delays its caller until a signal is received or
       one of its child processes terminates or stops due to tracing.  If  any
       child  process  has  died  or  stopped  due to tracing and this has not
       already been reported, return is immediate, returning  the  process  ID
       and status of one of those children. If that child process has died, it
       is discarded. If there are no children, −1 is returned immediately.  If
       there  are  only	 running or stopped but reported children, the calling
       process is blocked.

       If statusp is not a null pointer, then  on  return  from	 a  successful
       wait3()	call, the status of the child process is stored in the integer
       pointed to by statusp. *statusp indicates the cause of termination  and
       other information about the terminated process in the following manner:

	   o	  If  the  low-order 8 bits of *statusp are equal to 0177, the
		  child process has stopped; the 8 bits	 higher	 up  from  the
		  low-order  8 bits of *statusp contain the number of the sig‐
		  nal that caused the process to stop. See signal.h(3HEAD).

	   o	  If the low-order 8 bits of *statusp are non-zero and are not
		  equal to 0177, the child process terminated due to a signal;
		  the low-order 7 bits of *statusp contain the number  of  the
		  signal that terminated the process. In addition, if the low-
		  order seventh bit of *statusp (that is, bit 0200) is set,  a
		  ``core  image''  of  the  process  was  produced;  see  sig‐
		  nal.h(3HEAD).

	   o	  Otherwise, the child process terminated  due	to  an	exit()
		  call;	 the  8	 bits  higher  up from the low-order 8 bits of
		  *statusp contain the low-order 8 bits of the	argument  that
		  the child process passed to exit(); see exit(2).

       The  options  argument  is constructed from the bitwise inclusive OR of
       zero or more of the following flags, defined in <sys/wait.h>:

       WNOHANG
		    Execution of the calling process is not suspended if  sta‐
		    tus is not immediately available for any child process.

       WUNTRACED
		    The	 status	 of  any child processes that are stopped, and
		    whose status has not yet been reported since they stopped,
		    are also reported to the requesting process.

       If rusage is not a null pointer, a summary of the resources used by the
       terminated process and all its children is returned. Only the user time
       used  and  the  system  time  used  are	currently  available. They are
       returned in the ru_utime and ru_stime, members of the rusage structure,
       respectively.

       When  the  WNOHANG  option is specified and no processes have status to
       report, wait3() returns 0. The WNOHANG and  WUNTRACED  options  may  be
       combined by the bitwise OR operation of the two values.

       The wait4() function is an extended interface.  If pid is 0, wait4() is
       equivalent to wait3(). If pid has a nonzero value, wait4() returns sta‐
       tus only for the indicated process ID, but not for any other child pro‐
       cesses. If pid has a negative value, wait4()  return  status  only  for
       child  processes	 whose process group ID is equal to the absolute value
       of pid. The status  can	be  evaluated  using  the  macros  defined  by
       wait.h(3HEAD).

RETURN VALUES
       If  wait3()  or	wait4()	 returns  due to a stopped or 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.

       If wait3() or wait4() return due to the delivery of  a  signal  to  the
       calling	process, −1 is returned and errno is set to EINTR.  If WNOHANG
       was set in options, it has at least one child process specified by  pid
       for  which status is not available, and status is not available for any
       process specified by pid, 0 is returned.	 Otherwise, −1 is returned and
       errno is set to indicate the error.

       The  wait3() and wait4() functions return 0 if WNOHANG is specified and
       there are no stopped or exited children, and return the process	ID  of
       the  child  process if they return due to a stopped or terminated child
       process. Otherwise, they return −1 and set errno to indicate the error.

ERRORS
       The wait3() and wait4() functions will fail and return immediately if:

       ECHILD
		 The calling process has no existing unwaited-for  child  pro‐
		 cesses.

       EFAULT
		 The statusp or rusage arguments point to an illegal address.

       EINTR
		 The  function	was  interrupted by a signal. The value of the
		 location pointed to by statusp is undefined.

       EINVAL
		 The value of options is not valid.

       The wait4() function may fail if:

       ECHILD
		 The process specified by pid does not exist or is not a child
		 of the calling process.

       The wait3()and wait4() functions will terminate prematurely, return −1,
       and set errno to EINTR upon the arrival of a  signal  whose  SA_RESTART
       bit in its flags field is not set (see sigaction(2)).

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

       ┌───────────────┬───────────────────┐
       │ATTRIBUTE TYPE │  ATTRIBUTE VALUE  │
       ├───────────────┼───────────────────┤
       │MT-Level       │ Async-Signal-Safe │
       └───────────────┴───────────────────┘

SEE ALSO
       kill(1),	 exit(2),  waitid(2),  waitpid(3C), getrusage(3C), signal(3C),
       signal.h(3HEAD), wait(3C), wait.h(3HEAD), proc(4), attributes(5)

NOTES
       If a parent process terminates without waiting  on  its	children,  the
       initialization process (process ID = 1) inherits the children.

       The  wait3()  and  wait4() functions are automatically restarted when a
       process receives	 a  signal  while  awaiting  termination  of  a	 child
       process,	 unless	 the  SA_RESTART  bit is not set in the flags for that
       signal.

				  Nov 4, 2005			     WAIT3(3C)
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