test4.c

来自「这个是学习嵌入式开发的重要例子」· C语言 代码 · 共 107 行

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

void parent_process_main(pid_t child);
void child_process_main(void);

void parent_signal_handler(int s);
void child_signal_handler(int s);

int global_parent_wakeup = 0;
int global_child_sleep_flag = 0;

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);
  }

  parent_process_main(pid);

  return 0;
}

void child_process_main(void)
{
  setsid();

  signal(SIGINT, child_signal_handler);
  signal(SIGTERM, child_signal_handler);

  for (;;)
  {
    fprintf(stdout, "[%d]I'm working...\n", getpid());
    //sleep(1);

    if (global_child_sleep_flag)
    {
      sleep(5);
    }
  }
}

void parent_process_main(pid_t child)
{
  int i;

  signal(SIGINT, parent_signal_handler);

  for (;;)
  {
    if (global_parent_wakeup)
    {
      fprintf(stdout, "[%d]Parent process wake up.\n", getpid());
      break;
    }
  }

  for (i = 0; i < 10; i++)
  {
    // int kill(pid_t pid, int sig);
    if (kill(child, SIGINT) < 0)
    {
      // Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to  indi-cate the error.
      fprintf(stderr, "kill() failed: %s\n", strerror(errno));
    }
    else
    {
      fprintf(stdout, "[%d] Sending SIGINT to child process %d\n", getpid(), child);
    }

    //sleep(1);
  }

  kill(child, SIGTERM);
}

void parent_signal_handler(int s)
{
  fprintf(stdout, "[%d]Catched %d signal.\n", getpid(), s);
  global_parent_wakeup++;
}

void child_signal_handler(int s)
{
  fprintf(stdout, "[%d]Catched %d signal.\n", getpid(), s);

  if (s == SIGTERM)
  {
    global_child_sleep_flag++;
  }
}