vfork子进程调用exit后的退出问题？？

qfeng_zhao

代码:

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

int glob = 6;

int main()
{
int var;
pid_t pid;

var = 88;

printf("before vfork\n");

if((pid = vfork()) < 0){
printf("vfork error\n"0;
}else if(pid == 0){
glob++;
var++;
_exit(0); //问题?? 换成exit(0),输出??
}


printf("pid = %d, glob = %d, var = %d\n, getpid(), glob, var);

exit(EXIT_SUCCESS);
}

就是unix环境编程的问题,书上说如果把_exit(0), 换作exit(0),将会只输出:
before vfork
原因是子进程调用了exit,它刷新关闭了所有的标准I/0流,所以父进程调用printf时,输出流已关闭,于是printf返回-1

可我运行不是,printf照样输出,返回值是32,请问各位是什么原因呢??

haohao_h

manpage

1. 
   
2. vfork()  differs  from  fork  in that the parent is suspended until the
   
3.        child makes a call to execve(2) or _exit(2).  The child shares all mem-
   
4.        ory  with  its parent, including the stack, until execve() is issued by
   
5.        the child.  The child must not return from the current function or call
   
6.        exit(), but may call _exit().
   

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1. 
   
2. In Linux, it
   
3.        has been equivalent to fork() until 2.2.0-pre6 or so. Since  2.2.0-pre9
   
4.        (on  i386,  somewhat later on other architectures) it is an independent
   
5.        system call. Support was added in glibc 2.0.112.
   

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qfeng_zhao

to haohao_t:

不是很明白你的意识, 能否解释子进程调用exit并没有关闭父进程的stdout的原因?