wait(2) — sys5



WAIT(2)         DOMAIN/IX Reference Manual (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
     information called status are stored in the low order 16
     bits of the location pointed to by stat_loc.  Status can be
     used to differentiate between stopped and terminated child
     processes and if the child process terminated, status iden-
     tifies the cause of termination and passes useful informa-
     tion 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. In addition, if the low order
          seventh bit (i.e., bit 200) is set, a ``core image''
          will have been produced; see signal(2).

     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).

NOTES
     See WARNING in signal(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
     and errno is set to indicate the error.



Printed 5/10/85                                            WAIT-1



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



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 5/10/85

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