Yuvalinux - Place to Learn Linux: Parent Child communication using pipes

Sunday, March 24, 2013

Parent Child communication using pipes

Parent Child communication using pipes

This is the simplest of program that you can get.

Here the parent communicates to child over a pipe.

NOTE:
if the child wants to communicate to the parent then it will have to closes(fd[0]) and Parent will closes(fd[1]).

this will only work UBUNTU, LINUX(RedHat) , Solaris, FreeBDS etc all UNIX VERSIONS. DONT TRY to use it on any compiler like gcc,turbo c, etc...

Send data from Parent to Child over a pipe:

#include <apue.h>  
#include <sys/types>  
#include <sys/wait.h>  

int main(void)  
 {  
   int   n;  
   int   fd[2];  
   pid_t  pid;  
   char  data[]="Hello world";  
   char  line[MAXLINE];  

   pid = fork();

   if (pipe(fd) < 0)  
     printf("pipe error");  
   if (pid < 0) {  
     printf("fork error");  
   } else if (pid > 0) {    /* parent */  
     close(fd[0]);  
     write(fd[1], data, strlen(data));  
   } else {        /* child */  
     close(fd[1]);  
     n = read(fd[0], line, MAXLINE);  
     write(STDOUT_FILENO, line, n);  
   }  
   exit(0);  
 }

Parent Child communication using pipes

#include <apue.h>  
#include <sys/types>  
#include <sys/wait.h>  

int main(void)  
 {  
   int   n;  
   int   fd[2];  
   pid_t  pid;  
   char  data[]="Hello world";  
   char  line[MAXLINE];  

   pid = fork();

   if (pipe(fd) < 0)  
     printf("pipe error");  
   if (pid < 0) {  
     printf("fork error");  
   } else if (pid > 0) {    /* parent */  
     close(fd[0]);  
     write(fd[1], data, strlen(data));  
   } else {        /* child */  
     close(fd[1]);  
     n = read(fd[0], line, MAXLINE);  
     write(STDOUT_FILENO, line, n);  
   }  
   exit(0);  
 }