waitid(2)                                                            waitid(2)


NAME
     waitid - wait for child process to change state

SYNOPSIS
     #include <sys/types.h>
     #include <wait.h>
     int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options);

DESCRIPTION
     waitid suspends the calling process until one of its children changes
     state.  It records the current state of a child in the structure pointed
     to by infop.  If a child process changed state prior to the call to
     waitid, waitid returns immediately.

     The idtype and id arguments specify which children waitid is to wait for.

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

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

          If idtype is P_ALL, waitid waits for any children and id is ignored.

     The options argument is used to specify which state changes waitid is to
     wait for.  It is formed by an OR of any of the following flags:

     WEXITED        Wait for process(es) to exit.

     WTRAPPED       Wait for traced process(es) to become trapped or reach a
                    breakpoint (see ptrace(2)).

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

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

     WNOHANG        Return immediately.

     WNOWAIT        Keep the process in a waitable state.

     infop must point to a siginfo_t structure, as defined in siginfo(5).
     siginfo_t is filled in by the system with the status of the process being
     waited for.

     waitid fails if one or more of the following is true.

     EFAULT         infop points to an invalid address.


     EINTR          waitid was interrupted due to the receipt of a signal by
                    the calling process.

     EINVAL         An invalid value was specified for options.

     EINVAL         idtype and id specify an invalid set of processes.

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

DIAGNOSTICS
     If waitid returns due to a change of state of one of its children, a
     value of 0 is returned.  If WNOHANG was specified, 0 may also be returned
     indicating no error.  Otherwise, a value of -1 is returned and errno is
     set to indicate the error.

SEE ALSO
     exec(2), exit(2), fork(2), intro(2), pause(2), ptrace(2), sigaction(2),
     signal(2), wait(2), siginfo(5)


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