Demo of handling zombie process.

test-handlezombie.c

/*
 * Demo of handling zombie process.
 * Build: gcc test-handlezombie.c -o test-handlezombie
 * Run: ./test-handlezombie
 */

#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <signal.h>

static void sig_child(int signo);

int main()
{
  pid_t pid;
  //创建捕捉子进程退出信号
  signal(SIGCHLD,sig_child);
  pid = fork();
  if (pid < 0)
  {
    perror("fork error:");
    exit(1);
  }
  else if (pid == 0)
  {
    printf("I am child process,pid id %d.I am exiting.\n",getpid());
    exit(0);
  }
  printf("I am father process.I will sleep two seconds\n");
  //等待子进程先退出
  sleep(2);
  //输出进程信息
  system("ps -o pid,ppid,state,tty,command");
  printf("father process is exiting.\n");
  return 0;
}

static void sig_child(int signo)
{
  pid_t        pid;
  int        stat;
  //处理僵尸进程
  while ((pid = waitpid(-1, &stat, WNOHANG)) >0)
    printf("child %d terminated.\n", pid);
}

Program output:

I am father process.I will sleep two seconds
I am child process,pid id 107310.I am exiting.
child 107310 terminated.
PID PPID S TT COMMAND
98698 98697 S pts/0 -bash
107309 98698 S pts/0 ./test-handlezombie.out
107311 107309 R pts/0 ps -o pid,ppid,state,tty,command
father process is exiting.

----------------no zombie process