test8.c

这个是学习嵌入式开发的重要例子

#include <stdio.h>
#include <sys/types.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/wait.h>

static void child_process_main(void);
void restart(void);
void monitoring(pid_t pid);

int main(int argc, char **argv)
{
  pid_t pid;

  if ((pid = fork()) < 0)
  {
    fprintf(stderr, "fork failed: %s\n", strerror(errno));
    exit(1);
  }
  else if (pid == 0)
  {
    // Child process
    child_process_main();
    exit(0);
    //abort();
  }
  else
  {
    monitoring(pid);
  }

  return 0;
}

static void child_process_main(void)
{
  printf("I'm child process, pid = %d, sleep 50 seconds.\n", getpid());
  sleep(50);
  printf("child process is waked up.\n");
}

void monitoring(pid_t pid)
{
  int status;
  pid_t returned_pid;

  // XXX: parent process will be blocked until child process exited.
  // pid_t wait(int *stat_loc);
  returned_pid = wait(&status);

  if (returned_pid != pid)
  {
    printf("wait() returned pid is not equal fork() returned pid.\n");
  }

  printf("child %d is exited, status = %d.\n", returned_pid, status);

  if (WIFEXITED(status))
  {
    printf("child process is normal termination, status = %d\n", WEXITSTATUS(status));
  }
  else if (WIFSIGNALED(status))
  {
    printf("child process is abnormal termination, status = %d.\n", WTERMSIG(status));

#ifdef WCOREDUMP
    if (WCOREDUMP(status))
    {
      printf("core dump file generated.\n");
    }
    else
    {
      printf("no core dump file generated.\n");
    }
#endif
  }
  else
  {
    printf("child process is paused.\n");
  }

  // parent process
  printf("I'm parent process, continue.\n");

  restart();
}

void restart(void)
{
  printf("Restarting child process ...\n");
  pid_t pid;

  if ((pid = fork()) < 0)
  {
    // FIXME: process this error.
  }
  else if (pid == 0)
  {
    child_process_main();
    exit(0);
  }
  else
  {
    monitoring(pid);
  }
}