drd/tests/fork.c

   1 #include <stdio.h>
   2 #include <pthread.h>
   3 #include <stdlib.h>
   4 #include <string.h>
   5 #include <unistd.h>
   6 #include <sys/wait.h>
   7
   8 #define NUM_THREADS 2
   9
  10 static pthread_t tid[NUM_THREADS];
  11 static pid_t pids[NUM_THREADS];
  12
  13 static void *startproc(void *arg)
  14 {
  15   pid_t pid;
  16   char *argv[] = { "/bin/ls", "/bin/ls", NULL };
  17
  18   if ((pid = fork()) == -1) {
  19     perror("fork error");
  20   } else if (pid == 0) {
  21     dup2(2, 1);    // redirect stdout to stderr
  22     execv(argv[0], argv); // child
  23   } else {
  24     *((pid_t*)arg) = pid;
  25   }
  26
  27   return NULL;
  28 }
  29
  30 int main(int argc, char **argv)
  31 {
  32   // No arguments means serialize the fork() calls. One argument means perform
  33   // both fork() calls concurrently.
  34   int serialize_fork = argc == 1;
  35   int i = 0;
  36   int err;
  37
  38   for (i = 0; i < NUM_THREADS; i++) {
  39     err = pthread_create(&tid[i], NULL, &startproc, &pids[i]);
  40     if (err != 0)
  41       perror("pthread_create()");
  42     if (serialize_fork)
  43       pthread_join(tid[i], NULL);
  44   }
  45   if (!serialize_fork) {
  46     for (i = 0; i < NUM_THREADS; i++)
  47       if (tid[i])
  48         pthread_join(tid[i], NULL);
  49   }
  50   for (i = 0; i < NUM_THREADS; i++)
  51     waitpid(pids[i], &err, 0);
  52
  53   return 0;
  54 }