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/*waitpid.c*/ 
#include  
#include  
#include  
#include  
#include  
 
int main() 
{ 
	pid_t pc,pr; 
	pc=fork(); 
	if(pc<0) 
		printf("Error fork.\n"); 
/*子进程*/ 
	else if(pc==0){  
/*子进程暂停5秒*/ 
		sleep(5); 
/*子进程正常退出*/ 
		exit(0); 
	} 
/*父进程*/ 
	else{  
/*循环测试子进程是否退出*/ 
		do{  
/*调用waitpid，且父进程不阻塞*/ 
			pr=waitpid(pc,NULL,WNOHANG); 
/*若子进程还未退出，则父进程暂停1秒*/ 
			if(pr==0){  
				printf("The child process has not exited\n"); 
				sleep(1); 
			} 
		}while(pr==0); 
/*若发现子进程退出，打印出相应情况*/ 
		if(pr==pc)  
			printf("Get child %d\n",pr); 
		else 
			printf("some error occured.\n"); 
	} 
}