Write a c function that implements simple piping Example ls

Solution

What is pipe command?

The pipe command ( | ) connects two commands in such a way that output of one command becomes input to the other command. By generating system calls we can achieve this in c programming.

// Executes the pipe command: ls -al | more

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

// function declaration
void pipefunctio(int pfd[]);

// The required commands to be executed in shell

char *command1[] = { \"ls\", \"-al\", 0 };
char *command2[] = { \"more\", 0 };

// main method goes here
int main()
{
// two int variables for status and id
   int pid, status;
//fd[0] for command 1 produce output and fd[1] for command 2 read output of command 1
   int fd[2];
// opening pipe
   pipe(fd);

// switch for process id pid
   switch (pid = fork()) {

   case 0: // child forck - calling function
       pipefunction(fd);
// exit after calling
       exit(0);

   case -1:
       perror(\"fork\");
       exit(1);
default: // parent process
       while ((pid = wait(&status)) != -1)
           fprintf(stderr, \"process %d exits with %d\ \", pid, WEXITSTATUS(status));
       break;
  
   }
   exit(0);
}

void pipefunction(int pfd[])
{
   int pid;

   switch (pid = fork()) {

   case 0: // child process/ fork
       dup2(pfd[0], 0);
       close(pfd[1]);   /* the child does not need this end of the pipe */
       execvp(command2[0], command2);
       perror(command2[0]);

   case -1:
       perror(\"fork\");
       exit(1);
default: // parent process
       dup2(pfd[1], 1);
       close(pfd[0]);   /* the parent does not need this end of the pipe */
       execvp(command1[0], command1);
       perror(command1[0]);
   }
}