wait((int *)0)的含义 [英] Meaning of wait((int *)0)

问题描述

使用这样的等待功能的这样的程序是这样的:

One such program that uses a wait function like this is this one:

#include<stdio.h> 
#include<stdlib.h> 
int main() 
{ 
    int pid,fd[2]; int n; char line[20];        
    if(pipe(fd)<0) { 
        printf("Error creating pipe"); 
    } else { 
        pid=fork(); 
        if(pid<0) { 
            printf("Error while forking"); 
        } else { 
            if(pid>0) { 
                close(fd[0]); 
                write(fd[1],"Hello\n",6); 
                while(wait((int *)0)!=pid);
            } else { 
                close(fd[1]); 
                n=read(fd[0],line,20); 
                if(n<0) 
                printf("Error reading a file"); 
                write(1,line,n); 
            } 
        } 
    } 
    return 0; 
}   

推荐答案

stager的答案是正确的.尽管应该指出，强制转换完全没有必要，因为根据标准，指针上下文中使用的0是NULL指针.

stager's answer is correct. Though it should be noted that the cast is entirely unnecessary since according to the standard, 0 used in a pointer context is the NULL pointer.

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