/*
man posix_spawn(3)

gcc -g -Wall -o test_posix_spawn test_posix_spawn.c

$ ./a.out date
PID of child: 7634
Tue Feb  1 19:47:50 CEST 2011
Child status: exited, status=0

$ ./a.out -c date
PID of child: 7636
date: write error: Bad file descriptor
Child status: exited, status=1

$ ./a.out -s sleep 60 &
[1] 7637
$ PID of child: 7638
$ kill 7638
$ kill -KILL 7638
$ Child status: killed by signal 9
[1]+  Done                    ./a.out -s sleep 60

$ ./a.out xxxxx
PID of child: 10190
Child status: exited, status=127

Hurd:
./test_posix_spawn xxxx
posix_spawn: No such file or directory

*/

#include <spawn.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <wait.h>
#include <errno.h>

#define errExit(msg)    do { perror(msg);	\
    exit(EXIT_FAILURE); } while (0)

#define errExitEN(en, msg)			\
  do { errno = en; perror(msg);			\
    exit(EXIT_FAILURE); } while (0)

char **environ;

int
main(int argc, char *argv[])
{
  pid_t child_pid;
  int s, opt, status;
  sigset_t mask;
  posix_spawnattr_t attr;
  posix_spawnattr_t *attrp;
  posix_spawn_file_actions_t file_actions;
  posix_spawn_file_actions_t *file_actionsp;

  /* Parse command-line options, which can be used to specify an
     attributes object and file actions object for the child. */

  attrp = NULL;
  file_actionsp = NULL;

  while ((opt = getopt(argc, argv, "sc")) != -1) {
    switch (opt) {
    case 'c':       /* -c: close standard output in child */

      /* Create a file actions object and add a "close"
	 action to it */

      s = posix_spawn_file_actions_init(&file_actions);
      if (s != 0)
	errExitEN(s, "posix_spawn_file_actions_init");

      s = posix_spawn_file_actions_addclose(&file_actions,
					    STDOUT_FILENO);
      if (s != 0)
	errExitEN(s, "posix_spawn_file_actions_addclose");

      file_actionsp = &file_actions;
      break;

    case 's':       /* -s: block all signals in child */

      /* Create an attributes object and add a "set signal mask"
	 action to it */

      s = posix_spawnattr_init(&attr);
      if (s != 0)
	errExitEN(s, "posix_spawnattr_init");
      s = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK);
      if (s != 0)
	errExitEN(s, "posix_spawnattr_setflags");

      sigfillset(&mask);
      s = posix_spawnattr_setsigmask(&attr, &mask);
      if (s != 0)
	errExitEN(s, "posix_spawnattr_setsigmask");

      attrp = &attr;
      break;
    }
  }

  /* Spawn the child. The name of the program to execute and the
     command-line arguments are taken from the command-line arguments
     of this program. The environment of the program execed in the
     child is made the same as the parent's environment. */

    s = posix_spawnp(&child_pid, argv[optind], file_actionsp, attrp,
		   &argv[optind], environ);
  if (s != 0)
    errExitEN(s, "posix_spawn");

  /* Destroy any objects that we created earlier */

  if (attrp != NULL) {
    s = posix_spawnattr_destroy(attrp);
    if (s != 0)
      errExitEN(s, "posix_spawnattr_destroy");
  }

  if (file_actionsp != NULL) {
    s = posix_spawn_file_actions_destroy(file_actionsp);
    if (s != 0)
      errExitEN(s, "posix_spawn_file_actions_destroy");
  }

  printf("PID of child: %ld\n", (long) child_pid);

  /* Monitor status of the child until it terminates */

  do {
#ifndef __GNU__
    s = waitpid(child_pid, &status, WUNTRACED | WCONTINUED);
#else
    s = waitpid(child_pid, &status, WUNTRACED);
#endif
    if (s == -1)
      errExit("waitpid");

    printf("Child status: ");
    if (WIFEXITED(status)) {
      printf("exited, status=%d\n", WEXITSTATUS(status));
    } else if (WIFSIGNALED(status)) {
      printf("killed by signal %d\n", WTERMSIG(status));
    } else if (WIFSTOPPED(status)) {
      printf("stopped by signal %d\n", WSTOPSIG(status));
#ifndef __GNU__
    } else if (WIFCONTINUED(status)) {
      printf("continued\n");
#endif
    }
  } while (!WIFEXITED(status) && !WIFSIGNALED(status));

  exit(EXIT_SUCCESS);
}