Stuck on using multiple pipes in C

I'm writing a program that just chains together specifically 3 programs, etc "ls | sort | wc".

I looked through the other posts I found on google about multiple pipes but I still can't figure out what I've been doing wrong. Been stuck on this for a while. I believe my program is logically correct, but for some reason it doesn't run. What am I missing?

pipe(pipe1);
pipe(pipe2);

pid = fork();
if(pid > 0){
    close(pipe2[1]);
    dup2(pipe2[0], 0);
    execlp(argv[3], argv[3], NULL);
}
else if(pid == 0){
    pid2 = fork();
    if(pid2 == 0){
        close(pipe1[0]);
        dup2(pipe1[1], 1);
        execlp(argv[1], argv[1], NULL);
    }
    else if(pid2 > 0){
        close(pipe1[1]);
        dup2(pipe1[0], 0);
        close(pipe2[0]);
        dup2(pipe2[1], 1);
        execlp(argv[2], argv[2], NULL);
    }
}

You need to fork three times each time in the parent cases, and execute your commands only inside the child cases. Take a look here

Adjusted to your case:

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

int main(int argc, char **argv) {

  int pid;
  int pipe1[2];
  int pipe2[2];

  // create pipe1
  if (pipe(pipe1) == -1) {
    perror("bad pipe1");
    exit(1);
  }

  // fork (ps aux)
  if ((pid = fork()) == -1) {
    perror("bad fork1");
    exit(1);
  } 
  else if (pid == 0) {
    // stdin --> ps --> pipe1
    // input from stdin (already done), output to pipe1
    dup2(pipe1[1], 1);
    // close fds
    close(pipe1[0]);
    close(pipe1[1]);

    execlp(argv[1], argv[1], NULL);
    // exec didn't work, exit
    perror("bad exec ps");
    _exit(1);
  }
  // parent

  // create pipe2
  if (pipe(pipe2) == -1) {
    perror("bad pipe2");
    exit(1);
  }

  // fork (grep root)
  if ((pid = fork()) == -1) {
    perror("bad fork2");
    exit(1);
  } 
  else if (pid == 0) {
    // pipe1 --> grep --> pipe2
    // input from pipe1
    dup2(pipe1[0], 0);
    // output to pipe2
    dup2(pipe2[1], 1);
    // close fds
    close(pipe1[0]);
    close(pipe1[1]);
    close(pipe2[0]);
    close(pipe2[1]);

    execlp(argv[2], argv[2], NULL);
    // exec didn't work, exit
    perror("bad exec grep root");
    _exit(1);
  }
  // parent

  // close unused fds
  close(pipe1[0]);
  close(pipe1[1]);

  // fork (grep sbin)
  if ((pid = fork()) == -1) {
    perror("bad fork3");
    exit(1);
  } 
  else if (pid == 0) {
    // pipe2 --> grep --> stdout
    // input from pipe2
    dup2(pipe2[0], 0);
    // output to stdout (already done). Close fds
    close(pipe2[0]);
    close(pipe2[1]);

    execlp(argv[3], argv[3], NULL);
    // exec didn't work, exit
    perror("bad exec grep sbin");
    _exit(1);
  }
  // parent

  return 0;
}