test10.c

这个是学习嵌入式开发的重要例子

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

void child_process_main1(void);
void child_process_main2(void);
void child_process_main3(void);

int main(int argc, char **argv)
{
  pid_t pid1, pid2, pid3;

  pid1 = fork();

  if (pid1 < 0)
  {
    // output_error_message();
  }
  else if (pid1 == 0)
  {
    child_process_main1();
    exit(0);
  }

  pid2 = fork();

  if (pid2 < 0)
  {
    // output_error_message();
  }
  else if (pid2 == 0)
  {
    child_process_main2();
    exit(2);
  }

  int status;

  pid_t returned_pid;

  for (;;)
  {
    //returned_pid = wait(&status);
    //pid_t waitpid(pid_t pid, int *stat_loc, int options);
    //returned_pid = waitpid(-1, &status, 0);
    //returned_pid = waitpid(0, &status, 0);
    //returned_pid = waitpid(-1*getgid(), &status, 0);
    returned_pid = waitpid(pid2, &status, 0);

    printf("wait() returned.\n");
    printf("child process (pid = %d) exited.\n", returned_pid);

#if 0
    if (returned_pid == pid1)
    {
      printf("child process 1 exited.\n");
    }
    else if (returned_pid == pid2)
    {
      printf("child process 2 exited.\n");
    }
    else
    {
      printf("unkonwed error.\n");
    }
#endif

#if 0

    if (returned_pid < 0)
    {
      printf("wait() failed: %s.\n", strerror(errno));
    }
    else if (returned_pid != pid2)
    {
      returned_pid = wait(&status);
      printf("wait() returned.\n");
      printf("child process (pid = %d) exited.\n", returned_pid);
      break;
    }
    else
    {
      printf("child process 2 exited.\n");
      continue;
    }
#endif

    switch ((int) returned_pid)
    {
      case (int) pid1:
	//connect_to_control_center();
	break;
      case (int) pid2:
	//connect_to_device_1();
	break;
      case (int) pid3:
	//connect_to_device_2();
	break;
      default:
	break;
    }
  }

  return 0;
}

void child_process_main1(void)
{
  printf("[%d]child process main()\n", getpid());
  //connect_to_control_center();
}

void child_process_main2(void)
{
  printf("[%d]child process main()\n", getpid());
  //connect_to_device_1();
  //sleep(10);
}

void child_process_main3(void)
{
  printf("[%d]child process main()\n", getpid());
  //connect_to_device_2();
  //sleep(10);
}