WAIT(2)                  DOMAIN/IX SYS5                   WAIT(2)



NAME
     wait - wait for child process to stop or terminate

USAGE
     int wait(stat_loc)
     int *stat_loc;
     int wait ((int *)0)


DESCRIPTION
     Wait suspends the calling process until one of its children
     terminates.  The wait system call will return prematurely if
     a signal is received.  If a child process stopped or ter-
     minated before the call to wait, it returns immediately.

     If stat_loc (taken as an integer) is non-zero, 16 bits of
     "status," information are stored in the low order 16 bits of
     the location pointed to by stat_loc.  This status informa-
     tion can be used to differentiate between stopped and ter-
     minated child processes, and, when a child process has ter-
     minated, to identify the cause of termination and pass use-
     ful information to the parent.  This is accomplished in the
     following manner:

     ⊕  If the child process terminated because of an exit call,
        the low order 8 bits of status will be zero and the high
        order 8 bits will contain the low order 8 bits of the
        argument that the child process passed to exit; see
        exit(2).

     ⊕  If the child process terminated due to a signal, the high
        order 8 bits of status will be zero and the low order 8
        bits will contain the number of the signal that caused
        the termination.  On some implementations, the low order
        seventh bit (i.e., bit 200) is set to indicate that a
        "core image" has been produced.  DOMAIN/IX programs do
        not produce a core image.  Instead, they leave a process
        dump, which can be examined with the /com/fmpd command.

     If a parent process terminates without waiting for its child
     processes to terminate, the parent process ID of each child
     process is set to 1.  This means that the initialization
     process inherits the child processes; see intro(2).

RETURN VALUE
     If wait returns because it received a signal, a value of -1
     is returned to the calling process and errno is set to
     EINTR.  If wait returns because of a stopped or terminated
     child process, the process ID of the child is returned to
     the calling process.  Otherwise, a value of -1 is returned



Printed 12/4/86                                            WAIT-1

WAIT(2)                  DOMAIN/IX SYS5                   WAIT(2)



     and errno is set to indicate the error.

ERRORS
     Wait will fail and return immediately, if one or more of the
     following is true:

     [ECHILD]  The calling process has no existing unwaited-for
               child processes.

     [EFAULT]  Stat_loc points to an illegal address.

RELATED INFORMATION
     exec(2), exit(2), fork(2), pause(2), signal(2)








































WAIT-2                                            Printed 12/4/86