管道pipe

pipe是popen的底層函式

子程式呼叫 pipe3程式，傳給pipe3 管道的檔案描述符
pipe3對檔案描述符進行讀操作
實現不用程式之間的資料傳輸

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>                                                                                                                 

int main(){
    pid_t fork_result;
    const char some_data[] = "123";
    int file_pipes[2];
    char buffer[BUFSIZ + 1];    
    int data_processed;

    memset(buffer,'\0',sizeof(buffer));

    if(pipe(file_pipes) == 0){ 
        fork_result = fork();
        //child thread
        if(fork_result == 0){ 
            sprintf(buffer,"%d",file_pipes[0]);
            execl("pipe3","pipe3",buffer,(char *)0);
            exit(0);
        }else{
            data_processed = write(file_pipes[1],some_data,strlen(some_data));
            printf("%d - wrote %d bytes\n",getpid(),data_processed);
        }   
    }   
    exit(0);
}

pipe3

#include<stdio.h>
#include<stdlib.h>
#include<string.h>


int main(int argc,char *argv[]){
    char buffer[BUFSIZ + 1]; 
    int file_descriptor;

    memset(buffer,'\0',sizeof(buffer));

    sscanf(argv[1],"%d",&file_descriptor);
    read(file_descriptor,buffer,BUFSIZ);
    printf("get data:%s\n",buffer);
    exit(0);                                                                                                                       
}