unix 父子进程间通信-无名管道

#include <unistd.h> 
#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <string.h> 
#include <sys/types.h> 
#include <sys/wait.h> 
 
 
 
#define MAXLINE 100 
 
char buf[MAXLINE]; 
 
 
 
int main(int argc, char** agrv) 
{ 
        int pipefd[2]; 
        int ret; 
         
        if(0 != pipe(pipefd))//创建管道 
        { 
                perror("pipe\n"); 
                exit(1); 
        } 
        //创建子程序 
        if((ret=fork()) < 0)//创建失败 
        { 
                perror("fork\n"); 
                exit(1);         
        } 
        else if(ret == 0)//子程序 
        { 
                FILE* fp; 
                 
                close(pipefd[0]);//关闭管道可读端 
                 
                fp = fopen("./main.c","r"); //打开已存在可读文件 
                if(NULL == fp) 
                { 
                        perror("fopen\n"); 
                        exit(1);                 
                } 
                 
                while(fgets(buf,MAXLINE,fp) != NULL)//将文件内容全部读入管道 
                { 
                        int n = strlen(buf); 
                        if(n != write(pipefd[1],buf,n)) 
                        { 
                                perror("write\n"); 
                                exit(1);                            
                        } 
                }//end while 
                 
                 
                if(ferror(fp))//在读的过程文件是否有报错 
                { 
                        perror("ferror\n"); 
                        exit(1);                    
                } 
                 
                close(pipefd[1]);//关闭文件可写端 
                exit(0);//退出子程序 
        } 
        else 
        { 
                close(pipefd[1]);//关闭管道可写端 
                 
                if(-1 == wait(NULL))//等待子程序完全将文件内容读入到管道 
                { 
                        perror("wait\n"); 
                        exit(1);                  
                } 
                 
                if(dup2(pipefd[0],STDIN_FILENO) != STDIN_FILENO)//重新设置标准输入为管道可读端 
                { 
                        perror("dup2\n"); 
                        exit(1);                           
                } 
                 
                if(execl("/bin/more","more",(char*)0) < 0 )//分页程序 自动调用标准输入文件 显示管道内容 
                { 
                        perror("execl\n"); 
                        exit(1);                   
                } 
         
        } 
        return 0; 
}