waitid man page on DigitalUNIX

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waitid(2)							     waitid(2)

       waitid - Wait for child process to change state

       #include <sys/wait.h>

       int waitid(
	       idtype_t idtype,
	       id_t id,
	       siginfo_t *infop,
	       int options );

       Interfaces  documented on this reference page conform to industry stan‐
       dards as follows:

       waitid(): XPG4-UNIX

       Refer to the standards(5) reference page	 for  more  information	 about
       industry standards and associated tags.

       Identifies the type of process to be affected.  Used with the id param‐
       eter, it suspends execution for the specified child process.  Specifies
       either  the  process ID or process group ID of the child process.  Used
       with the idtype parameter, it  suspends	execution  for	the  specified
       process.	  Specifies a pointer to a siginfo_t structure.	 Specifies the
       conditions that must occur before a wait operation is performed by  the
       waitid() function.

       The  waitid()  function	holds  a  calling process until the state of a
       child process changes.  The current state of the child is recorded in a
       structure pointed to by the infop parameter. If a child process changed
       state prior to the call to the waitid() function, the waitid() function
       returns immediately.

       The idtype and id parameters determine which child process the waitid()
       function is to act  upon.   If  the  idtype  parameter  is  P_PID,  the
       waitid()	 function  waits  for  the  child  with	 a process ID equal to
       (pid_t)id.  If the idtype parameter is P_PGID,  the  waitid()  function
       waits for any child with a process group ID equal to (pid_t)id.	If the
       idtype parameter is P_ALL, the waitid function waits for any child  and
       the id parameter is ignored.

       The options parameter specifies the conditions that must occur before a
       wait operation is performed by the waitid()  function.	To  specify  a
       condition,  use	at  least  one	of the following flags in a logical OR
       operation: Return the status for any child that	was  stopped  and  has
       been  continued.	 Wait for processes to exit.  Return immediately if no
       child processes in the requested state are  present.   Keep  the	 child
       process whose status is returned in infop in a waitable state.  Another
       wait for that child may occur with the  same  results.	Wait  for  and
       return the process status of any child that has stopped upon receipt of
       a signal.  [Tru64 UNIX]	Wait for traced processes to become trapped or
       reach a breakpoint (see ptrace(2)).

       The  infop  parameter must point to a siginfo_t structure as defined in
       siginfo(5). This structure contains the status explaining why a process
       is in a wait state.

       The  waitid()  function returns if a child process is found that satis‐
       fies the conditions defined by the idtype and  options  parameters.  In
       this  case,  the	 system fills in the structure pointed to by the infop
       parameter with the process status. The system always sets the  si_signo
       structure member to SIGCHLD.

       If  the	waitid() function returns because the state of a child process
       changes, it returns a value of zero (0).	 Otherwise, a value of	-1  is
       returned and errno is set to indicate the error.

       The  waitid()  function sets errno to the specified values for the fol‐
       lowing conditions: The calling process has no unwaited-for  child  pro‐
       cesses.	 [Tru64	 UNIX]	The  infop  parameter  points  to  an  invalid
       address.	 The waitid() function was interrupted due to the receipt of a
       signal  by  the	calling	 process.   An invalid value was used with the
       options parameter, or the idtype and id parameters specify  an  invalid
       set of processes.

       Functions:  intro(2),  exec(2),	exit(2), fork(2), pause(3), ptrace(2),
       sigaction(2), signal(2), wait(2)

       Routines:  pause(3)

       Files:  siginfo(5)

       Standards:  standards(5)


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