2.9BSD/usr/man/cat2/wait.2

WAIT(2)             UNIX Programmer's Manual              WAIT(2)

NAME
     wait - wait for process to terminate

SYNOPSIS
     wait(status)
     int *status;

     wait((int *) 0)

DESCRIPTION
     _W_a_i_t causes its caller to delay until a signal is received
     or one of its child processes terminates.  If any child has
     died since the last _w_a_i_t, return is immediate; if there are
     no children, return is immediate with the error bit set
     (resp. with a value of -1 returned).  The normal return
     yields the process ID of the terminated child.  In the case
     of several children several _w_a_i_t calls are needed to learn
     of all the deaths.

     If (int)_s_t_a_t_u_s is nonzero, the high byte of the word pointed
     to receives the low byte of the argument of _e_x_i_t when the
     child terminated.  The low byte receives the termination
     status of the process.  See _s_i_g_n_a_l(2) for a list of termina-
     tion statuses (signals); 0 status indicates normal termina-
     tion.  A special status (0177) is returned for a stopped
     process which has not terminated and can be restarted.  See
     _p_t_r_a_c_e(2).  If the 0200 bit of the termination status is
     set, a core image of the process was produced by the system.

     If the parent process terminates without waiting on its
     children, the initialization process (process ID = 1) inher-
     its the children.

RETURN VALUE
     If _w_a_i_t returns due to the receipt of a signal, a value of
     -1 is returned to the calling process and the _e_r_r_n_o is set
     to EINTR.  If _w_a_i_t returns due to 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 _e_r_r_n_o is set to indicate the error.

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

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

     [EFAULT]            The _s_t_a_t_u_s argument points to an address
                         outside the process's allocated address
                         space.

Printed 5/22/83                                                 1

WAIT(2)             UNIX Programmer's Manual              WAIT(2)

SEE ALSO
     exit(2), fork(2), signal(2), wait2(2J)

ASSEMBLER
     (wait = 7.)
     sys wait
     (process ID in r0)
     (status in r1)

     The high byte of the status is the low byte of r0 in the
     child at termination.

Printed 5/22/83                                                 2