Linux杀死fork产生的子进程的僵尸进程defunct

僵尸进程 就是 已经结束,但是还没有清理出去的.用kill -9 $PID 也无法杀死.

所以程序中应该避免出现僵尸进程.

用fork之后,父进程如果没有wait /waitpid 等待子进程的话,子进程完毕后,就成了僵尸进程.

但是父进程如果等待wait/waitpid的话,就没法干别的事情了...尤其在多个子进程的情况下.所以 中断 信号量 是一个好办法:

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

void sig_child(){
    pid_t   pid; 
    int       status; 
    while((pid   =   waitpid(-1,   &status,   WNOHANG))   >   0)   {} 
    //Key !!!!!!!!  wait or waitpid
    return; 
}
void nodefunct_sig(){
    signal(SIGCHLD,sig_child);//prevent defunct
    
    int child=0;
    pid_t status=0;
    int i=0;
    while(1){
        if(child=fork()==0){
            childf();
            printf("child(%d):I will be exit...pgid=%d\n",getpid(),getpgid(getpid()));//getpgrp()
            abort();
            char cmd[1024]="";
            sprintf(cmd,"kill -9 %d",getpid());
            system(cmd);
            exit(5);
        }else{
            printf("Parent(%d):Main process...\n",getpid());
            //kill(child,SIGABRT);
            system("ps -A|grep a.out");
            
             sleep(3);
        }
        printf("Parent: waitting child...pgid=%d\n\n",getpgid(getpid()));
       //waitpid(child,&status,
    }
}
void main(){
    nodefunct_sig();
}

参考自:http://topic.csdn.net/t/20020424/21/673887.html