Simple pipe example

pipe.c

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

int main(int argc, char *argv[])
{
  int pp[2];
  int pid;
  char* word;

  if(pipe(pp) == -1){
    perror("bad pipe");
    exit(1);
  }

  if((pid=fork()) == -1){
    perror("bad fork");
    exit(1);
  }
  if(pid == 0) {
    close(0);
    if(dup(pp[0])!=0){
      perror("bad dup for child");
      exit(1);
    }
    close(pp[0]);
    close(pp[1]);
    word = "java";
    if(argc > 1){
      word = argv[1];
    }
    execlp("grep", "grep", word, NULL);
    perror("bad exec");
    exit(1);
  }
  close(1);
  if(dup(pp[1])!=1) {
    perror("bad dup for parent");
    exit(1);
  }

  close(pp[0]);
  close(pp[1]);

  execlp("ps", "ps", "aux", NULL);
  perror("bad exec");

  return 1;
}