Krdytkyu

I am attempting to resolve the following problem:

Write a program in C that executes the following commands the same way a command interpreter would: paste file1 file2 | sort | nl > file3. You must consider that file1, file2 and file 3 will be parameters given to your program in the command line.

#include <stdlib.h>

#include <stdio.h>

#include <unistd.h>

#include <errno.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <sys/wait.h>



#define BUF_SIZE 1024



int main(int argc, char *argv) {

    int t[2];

    int fd;



    if (argc != 4) {

        printf("Format: %s <archivo1> <archivo2> <archivo3>.n", argv[0]);

        exit(1);

    }



    pipe(t);



    if (fork() != 0) {

        wait(NULL);

        printf("Padren");



        if (!(fd = open(argv[3], O_WRONLY))) {

            printf("Error al abrir el archivo %s.n", argv[3]);

            exit(1);

        }



        dup2(t[0], STDIN_FILENO);

        dup2(fd, STDOUT_FILENO);

        close(t[0]);

        close(t[1]);

        execlp("nl", "nl", NULL);



    } else {

        if (fork() != 0) {

            wait(NULL);

            printf("Hijo 1n");

            dup2(t[0], STDIN_FILENO);

            dup2(t[1], STDOUT_FILENO);

            close(t[0]);

            close(t[1]);

            execlp("sort", "sort", NULL);



        } else {

            printf("Hijo 2n");

            dup2(t[1], STDOUT_FILENO);

            close(t[0]);

            close(t[1]);

            execlp("paste", "paste", argv[1], argv[2], NULL);

        }

    }



    return 0;

}

But once it reaches to the section where the sort command is executed, it continues using the standard input and not the pipe. Am I missing something? Where did I go wrong?