unix 父子進程間通信-無名管道

#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))//創建管道 
        { 
                perror("pipe\n"); 
                exit(1); 
        } 
        //創建子程序 
        if((ret=fork()) < 0)//創建失敗 
        { 
                perror("fork\n"); 
                exit(1);         
        } 
        else if(ret == 0)//子程序 
        { 
                FILE* fp; 
                 
                close(pipefd[0]);//關閉管道可讀端 
                 
                fp = fopen("./main.c","r"); //打開已存在可讀文件 
                if(NULL == fp) 
                { 
                        perror("fopen\n"); 
                        exit(1);                 
                } 
                 
                while(fgets(buf,MAXLINE,fp) != NULL)//將文件內容全部讀入管道 
                { 
                        int n = strlen(buf); 
                        if(n != write(pipefd[1],buf,n)) 
                        { 
                                perror("write\n"); 
                                exit(1);                            
                        } 
                }//end while 
                 
                 
                if(ferror(fp))//在讀的過程文件是否有報錯 
                { 
                        perror("ferror\n"); 
                        exit(1);                    
                } 
                 
                close(pipefd[1]);//關閉文件可寫端 
                exit(0);//退出子程序 
        } 
        else 
        { 
                close(pipefd[1]);//關閉管道可寫端 
                 
                if(-1 == wait(NULL))//等待子程序完全將文件內容讀入到管道 
                { 
                        perror("wait\n"); 
                        exit(1);                  
                } 
                 
                if(dup2(pipefd[0],STDIN_FILENO) != STDIN_FILENO)//重新設置標準輸入為管道可讀端 
                { 
                        perror("dup2\n"); 
                        exit(1);                           
                } 
                 
                if(execl("/bin/more","more",(char*)0) < 0 )//分頁程序 自動調用標準輸入文件 顯示管道內容 
                { 
                        perror("execl\n"); 
                        exit(1);                   
                } 
         
        } 
        return 0; 
}