Function kwsysProcessFork

Source/kwsys/ProcessUNIX.c:2453–2496

#if !defined(__VMS)
static pid_t kwsysProcessFork(kwsysProcess* cp,
                              kwsysProcessCreateInformation* si)
{
  /* Create a detached process if requested.  */
  if (cp->OptionDetach) {
    /* Create an intermediate process.  */
    pid_t middle_pid = fork();
    if (middle_pid < 0) {
      /* Fork failed.  Return as if we were not detaching.  */
      return middle_pid;
    }
    if (middle_pid == 0) {
      /* This is the intermediate process.  Create the real child.  */
      pid_t child_pid = fork();
      if (child_pid == 0) {
        /* This is the real child process.  There is nothing to do here.  */
        return 0;
      }
      /* Use the error pipe to report the pid to the real parent.  */
      while ((write(si->ErrorPipe[1], &child_pid, sizeof(child_pid)) < 0) &&
             (errno == EINTR)) {
      }

      /* Exit without cleanup.  The parent holds all resources.  */
      kwsysProcessExit();
      return 0; /* Never reached, but avoids SunCC warning.  */
    }
    /* This is the original parent process.  The intermediate
        process will use the error pipe to report the pid of the
        detached child.  */
    pid_t child_pid;
    int status;
    while ((read(si->ErrorPipe[0], &child_pid, sizeof(child_pid)) < 0) &&
           (errno == EINTR)) {
    }

    /* Wait for the intermediate process to exit and clean it up.  */
    while ((waitpid(middle_pid, &status, 0) < 0) && (errno == EINTR)) {
    }
    return child_pid;
  }
  /* Not creating a detached process.  Use normal fork.  */
  return fork();
}
#endif

/* We try to obtain process information by invoking the ps command.