对waitpid 的学习

 
[root@localhost wait]# cat waittest.c
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdio.h>
#include<stdlib.h>
main()
{
    pid_t pc, pr; 
    pc=fork();
    if(pc<0)  
      printf("Error occured on forking.\n");
    else if(pc==0)
    {  
      sleep(4); 
      exit(0);
    }
    
    do
    {
       pr=waitpid(pc, NULL, WNOHANG); 
       if(pr==0)
       {   
          printf("No child exited\n");
          sleep(1);
       }
    }while(pr==0);
    
    if(pr==pc)
         printf("successfully release child %d\n", pr);
    else
         printf("some error occured\n");
}
[root@localhost wait]#