WAIT(2)                                                                WAIT(2)



NAME
       wait, wait3 - wait for process to terminate

SYNOPSIS
       #include <sys/wait.h>

       pid = wait(status)
       int pid;
       union wait *status;

       pid = wait(0)
       int pid;

       #include <sys/time.h>
       #include <sys/resource.h>

       pid = wait3(status, options, rusage)
       int pid;
       union wait *status;
       int options;
       struct rusage *rusage;

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, returning the process id and exit status of
       one of the terminated children.  If there are no  children,  return  is
       immediate with the value -1 returned.

       On  return from a successful _w_a_i_t call, _s_t_a_t_u_s is nonzero, and the high
       byte of _s_t_a_t_u_s contains the low byte of the argument to  _e_x_i_t  supplied
       by  the  child process; the low byte of _s_t_a_t_u_s contains the termination
       status of the process.  A more precise definition of the _s_t_a_t_u_s word is
       given in <_s_y_s_/_w_a_i_t_._h>.

       _W_a_i_t_3  provides an alternate interface for programs that 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 there are no processes that wish to  report  status
       (WNOHANG), and/or that children of the current process that are stopped
       due to a SIGTTIN, SIGTTOU, SIGTSTP, or SIGSTOP signal should also  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 pro‐
       cesses).

       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_r’ing the two values.

NOTES
       See _s_i_g_v_e_c(2) for a list of termination statuses  (signals);  0  status
       indicates  normal termination.  A special status (0177) is returned for
       a stopped process that 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) inherits the children.

       _W_a_i_t  and  _w_a_i_t_3  are automatically restarted when a process receives a
       signal while awaiting termination of a child process.

RETURN VALUE
       If _w_a_i_t returns due to a stopped or terminated child process, the  pro‐
       cess  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 there are no children not previously waited for;  0
       is  returned if WNOHANG is specified and there are no stopped or exited
       children.

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

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

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

SEE ALSO
       exit(2)



4th Berkeley Distribution        June 30, 1985                         WAIT(2)