fork and exec.c

#include <stdio.h>

#include <unistd.h>

#include <fcntl.h>

int g_fd;

int main(){

char* args[2];

char* env[2];

args[0] = "/bin/ps | grep ps";

args[1] = 0;

env[0] = 0;

env[1] = 0;

g_fd = open("tmp", O_RDWR|O_CREAT);

printf("g_fd : %d\n", g_fd);

int pid = fork();

// child.

if(pid==0){

dup2( g_fd, fileno(stdout) );

execve( args[0], args, env );

}

else{

char buf[1024];

int n;

sleep(1);

lseek(g_fd, 0, SEEK_SET);

while( n=read(g_fd, buf, 1024) ){

buf[n]=0;

printf("parent(%d) : [%s]\n", n, buf);

}

printf("n:%d\n",n); 

}

printf("end\n");

return 0;

}