(1)通过信号机制
子进程退出时向父进程发送SIGCHILD信号,父进程处理SIGCHILD信号,在信号处理函数中调用wait进行处理僵尸进程。
测试程序如下所示:
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/wait.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");
printf("pid = %d\n",pid);
//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);
}
}