pipe 2 linux commands in c

Question

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Is it possible to have pipe between two child processes created by same parent (LINUX, POSIX)

I want to create a program in C. This program has to be able to do the same that piping 2 linux commands do. For Example: ps aux | grep ssh

I need to be able to do this command in a c script.

I know I can use, fork, pipe, exec and dup but I don't quite know how to put them together... Can someone help me with this?

How far have you gone? Can you show us some code you've written? — Bertrand Marron, Jun 15 '11 at 22:46
Do you just want your program to be able to work within a pipe? Then just read from `stdin` and write to `stdout`, and you automatically get that behaviour. — Kerrek SB, Jun 15 '11 at 23:14

score 0 · Answer 1 · answered Jun 16 '11 at 02:07

As a simple example, this should give you a brief idea of how those system calls work together.

void spawn(char *program,char *argv[]){    
     if(pipe(pipe_fd)==0){
          char message[]="test";
          int write_count=0;

          pid_t child_pid=vfork();

          if(child_pid>0){
               close(pipe_fd[0]); //first close the idle end
               write_count=write(pipe_fd[1],message,strlen(message));
               printf("The parent process (%d) wrote %d chars to the pipe \n",(int)getpid(),write_count);
               close(pipe_fd[1]);
          }else{
               close(pipe_fd[1]);
               dup2(pipe_fd[0],0);

               printf("The new process (%d) will execute the program %s with %s as input\n",(int)getpid(),program,message);
               execvp(program,argv);
               exit(EXIT_FAILURE);
          }
     }
}

pipe 2 linux commands in c

1 Answers1