usr/include/wait.h

/*
 * This file holds definitions relevent to the wait system call.
 * Some of the options here are available only through the ``wait3''
 * entry point; the old entry point with one argument has more fixed
 * semantics, never returning status of unstopped children, hanging until
 * a process terminates if any are outstanding, and never returns
 * detailed information about process resource utilization (<vtimes.h>).
 */

/*
 * Structure of the information in the first word returned by both
 * wait and wait3.  If w_stopval==WSTOPPED, then the second structure
 * describes the information returned, else the first.  See WUNTRACED below.
 */
union wait      {
        int     w_status;               /* used in syscall */
        /*
         * Terminated process status.
         */
        struct {
                unsigned short  w_Termsig:7;    /* termination signal */
                unsigned short  w_Coredump:1;   /* core dump indicator */
                unsigned short  w_Retcode:8;    /* exit code if w_termsig==0 */
        } w_T;
        /*
         * Stopped process status.  Returned
         * only for traced children unless requested
         * with the WUNTRACED option bit.
         */
        struct {
                unsigned short  w_Stopval:8;    /* == W_STOPPED if stopped */
                unsigned short  w_Stopsig:8;    /* signal that stopped us */
        } w_S;
};
#define w_termsig       w_T.w_Termsig
#define w_coredump      w_T.w_Coredump
#define w_retcode       w_T.w_Retcode
#define w_stopval       w_S.w_Stopval
#define w_stopsig       w_S.w_Stopsig


#define WSTOPPED        0177    /* value of s.stopval if process is stopped */

/*
 * Option bits for the second argument of wait3.  WNOHANG causes the
 * wait to not hang if there are no stopped or terminated processes, rather
 * returning an error indication in this case (pid==0).  WUNTRACED
 * indicates that the caller should receive status about untraced children
 * which stop due to signals.  If children are stopped and a wait without
 * this option is done, it is as though they were still running... nothing
 * about them is returned.
 */
#define WNOHANG         1       /* dont hang in wait */
#define WUNTRACED       2       /* tell about stopped, untraced children */

#define WIFSTOPPED(x)   ((x).w_stopval == WSTOPPED)
#define WIFSIGNALED(x)  ((x).w_stopval != WSTOPPED && (x).w_termsig != 0)
#define WIFEXITED(x)    ((x).w_stopval != WSTOPPED && (x).w_termsig == 0)