pipe_example.c

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

enum {
  READ = 0,
  WRITE,
};

int main(void)
{
  int fd[2];
  pipe(fd);

  if ( fork() > 0 ) {
    dup2(fd[WRITE], STDOUT_FILENO);
    execv("/bin/cat", (char *[]){"cat", "tst.c", NULL});
  }

  dup2(fd[READ], STDIN_FILENO);
  execv("/bin/grep", (char *[]){"grep", "exec", NULL});

  return 0;
}