_O_n_l_i_n_e _M_a_n_u_a_l             System Calls                    wait(2)



NNNNAAAAMMMMEEEE
     wait, wait3 - wait for process to terminate

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     ####iiiinnnncccclllluuuuddddeeee <<<<ssssyyyyssss////wwwwaaaaiiiitttt....hhhh>>>>
     #include <signal.h>

     ppppiiiidddd ==== wwwwaaaaiiiitttt((((ssssttttaaaattttuuuussss))))
     int pid;
     union wait *status;

     ppppiiiidddd ==== wwwwaaaaiiiitttt((((0000))))
     int pid;

     ####iiiinnnncccclllluuuuddddeeee <<<<ssssyyyyssss////ttttiiiimmmmeeee....hhhh>>>>
     #include <sys/resource.h>

     ppppiiiidddd ==== wwwwaaaaiiiitttt3333((((ssssttttaaaattttuuuussss,,,, ooooppppttttiiiioooonnnnssss,,,, rrrruuuussssaaaaggggeeee))))
     int pid;
     union wait *status;
     int options;
     struct rusage *rusage;

DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     The _w_a_i_t call causes the caller to delay until either a sig-
     nal is received or a child process terminates.  Return is
     immediate if any child died since the last _w_a_i_t.  In this
     case, a terminated child's process id and exit status are
     returned.  If there are no children, an immediate error
     return (-1 return value) occurs.

     On successful return, status.w_retcode contains the low byte
     of the argument to _e_x_i_t supplied by the child process;
     status.w_termsig _c_o_n_t_a_i_n_s _t_h_e _c_h_i_l_d'_s _t_e_r_m_i_n_a_t_i_o_n _s_t_a_t_u_s
     (_s_i_g_n_a_l _n_u_m_b_e_r); _a_n_d _s_t_a_t_u_s._w__s_i_g_c_o_d_e contains the signal
     subclass code.  Refer to the sys/wait.h _h_e_a_d_e_r _f_i_l_e _o_n _y_o_u_r
     _s_y_s_t_e_m.

     _w_a_i_t_3 provides an alternate interface for programs which
     must not block when collecting the status of child
     processes.  The _s_t_a_t_u_s parameter is defined as above.  The
     _o_p_t_i_o_n_s parameter is used to indicate the call should not
     block if no processes wish to report status (WNOHANG),
     and/or that only children of the current process which are
     stopped due to a SIGTTIN, SIGTTOU, SIGTSTP, or SIGSTOP sig-
     nal should have their status reported (WUNTRACED).  If
     _r_u_s_a_g_e is non-zero, a summary of the resources used by the
     terminated process and all its children is returned.  (This
     information is currently not available for stopped
     processes).

     When the WNOHANG option is specified and no processes wish
     to report status, _w_a_i_t_3 returns a _p_i_d of 0.  The WNOHANG and
     WUNTRACED options may be combined by _o_ring the 2 values.

NNNNOOOOTTTTEEEESSSS
     See _s_i_g_v_e_c(2) for a list of termination statuses (signals);
     0 status indicates normal termination.  A special status
     (WSTOPPED) is returned for a stopped process, which has not






     terminated and can be restarted.  If the w_coredump field of
     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.

     Both _w_a_i_t and _w_a_i_t_3 are automatically restarted when a pro-
     cess receives a signal while awaiting termination of a child
     process.

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     If _w_a_i_t returns due to a stopped or terminated child pro-
     cess, 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.

     _w_a_i_t_3 returns -1 if no children were previously awaited; 0
     is returned if WNOHANG is specified and there are no stopped
     or exited children.

EEEERRRRRRRROOOORRRRSSSS
     _w_a_i_t fails and returns immediately if one or more of the
     following is true:

     [ECHILD]       The calling process has no existing child
                    processes that are not already awaited.

     [EFAULT]       Either the _s_t_a_t_u_s or _r_u_s_a_g_e arguments point
                    to an illegal address.

SSSSEEEEEEEE AAAALLLLSSSSOOOO
     System Calls (2):  exit, sigvec

March 1989                              TX Programmer's Reference