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waitid(2)                        System Calls                        waitid(2)



NAME
       waitid - wait for child process to change state

SYNOPSIS
       #include <wait.h>

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

DESCRIPTION
       The  waitid()  function  suspends  the calling process until one of its
       child processes changes state. It records the current state of a  child
       in  the   structure  pointed  to  by infop. It returns immediately if a
       child process changed state prior to the call.

       The idtype and  id arguments specify which  children   waitid()  is  to
       wait for, as follows:

         o  If   idtype  is P_PID, waitid() waits for the child with a process
            ID equal to (pid_t)id.

         o  If idtype is P_PGID,  waitid() waits for any child with a  process
            group ID equal to (pid_t)id.

         o  If  idtype  is  P_ALL,  waitid()  waits  for  any  child and id is
            ignored.


       The options argument is used to specify which state changes waitid() is
       to wait for. It is formed by bitwise OR operation of any of the follow-
       ing flags:

       WCONTINUED      Return the status for any child that  was  stopped  and
                       has been continued.



       WEXITED         Wait for process(es) to exit.



       WNOHANG         Return immediately.



       WNOWAIT         Keep the process in a waitable state.



       WSTOPPED        Wait  for  and  return  the process status of any child
                       that has  stopped upon receipt of a signal.



       WTRAPPED        Wait for traced process(es) to become trapped or  reach
                       a breakpoint (see ptrace(3C)).



       The  infop  argument must point to a siginfo_t structure, as defined in
       siginfo.h(3HEAD). If waitid() returns because a child process was found
       that  satisfies  the  conditions  indicated by the arguments idtype and
       options, then the structure pointed to by infop will be filled  by  the
       system with the status of the process.
        The si_signo member will always be equal to SIGCHLD.

       One instance of a SIGCHLD signal is queued for each child process whose
       status has changed. If waitid() returns because the status of  a  child
       process  is  available  and  WNOWAIT  was not specified in options, any
       pending SIGCHLD signal associated with the process  ID  of  that  child
       process is discarded. Any other pending SIGCHLD signals remain pending.

RETURN VALUES
       If waitid() returns due to a change of state of one of its children and
       WNOHANG was not used,  0 is returned.  Otherwise, -1  is  returned  and
       errno  is  set  to  indicate  the error. If WNOHANG was used,  0 can be
       returned (indicating no error); however, no children may  have  changed
       state if info->&gt;si_pid is 0.

ERRORS
       The waitid() function will fail if:

       ECHILD          The  set  of  processes specified by idtype and id does
                       not contain any unwaited processes.



       EFAULT          The infop argument points to an illegal address.



       EINTR           The  waitid()  function  was  interrupted  due  to  the
                       receipt of a signal by the calling process.



       EINVAL          An  invalid  value was specified for options, or idtype
                       and id specify an invalid set of processes.



USAGE
       With options equal to WEXITED | WTRAPPED,  waitid()  is  equivalent  to
       waitpid(3C).  With idtype equal to P_ALL and options equal to WEXITED |
       WTRAPPED, waitid() is equivalent to wait(3C).

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


       tab()    allbox;    cw(2.750000i)|     cw(2.750000i)     lw(2.750000i)|
       lw(2.750000i).   ATTRIBUTE TYPEATTRIBUTE VALUE Interface StabilityStan-
       dard MT-LevelAsync-Signal-Safe


SEE ALSO
       intro(2),   exec(2),   exit(2),   fork(2),   pause(2),    sigaction(2),
       ptrace(3C),   signal(3C),   siginfo.h(3HEAD),   wait(3C),  waitpid(3C),
       attributes(5), standards(5)



SunOS 5.10                        9 Jun 2004                         waitid(2)