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 ",getpid(),getpgid(getpid()));//getpgrp()
abort();
char cmd[1024]="";
sprintf(cmd,"kill -9 %d",getpid());
system(cmd);
exit(5);
}else{
printf("Parent(%d):Main process... ",getpid());
//kill(child,SIGABRT);
system("ps -A|grep a.out");
sleep(3);
}
printf("Parent: waitting child...pgid=%d ",getpgid(getpid()));
//waitpid(child,&status,
}
}
void main(){
nodefunct_sig();
}