管道学习

/*
@@
    Author:    JustinZhang
    Email:    uestczhangchao@gmail.com
    Time:    2012-9-1 23:32:22
    desc:    Example from man, write by hand, test under ubuntu gcc.
            For the purpose of reviewing pipe.
@@
*/

#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
int main(int argc, char *argv[])
{
    int pipefd[2];
    pid_t cpid;
    char buf;
    if(argc !=2)
    {
        fprintf(stderr, "Usage:%s <string>\n",argv[0]);
        exit(EXIT_FAILURE);
    }
    if(pipe(pipefd)==-1)
    {
        perror("pipe");
        exit(EXIT_FAILURE);
    }
    cpid = fork();
    if(cpid == -1)
    {
        perror("fork");
        exit(EXIT_FAILURE);
    }
    /*return from child*/
    if(cpid==0)
    {
        /*close the write side of pipe*/
        close(pipefd[1]);
        while(read(pipefd[0], &buf, 1)>0)
        {
            write(STDOUT_FILENO, &buf, 1);
        }
        write(STDOUT_FILENO, "\n", 1);
        close(pipefd[0]);
        _exit(EXIT_SUCCESS);
    }
    else /*return from parent, write arg[1] to pipe*/
    {
        close(pipefd[0]);
        write(pipefd[1],argv[1],strlen(argv[1]));
        close(pipefd[1]);
        wait(NULL);
        exit(EXIT_SUCCESS);
    }
    return 0;
}