#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main()
{
        int pipe1[2]; /* pipe for:  sort ------> uniq */
        int pipe2[2]; /* pipe for:  uniq ------> wc   */
        int pipe3[2]; /* pipe for:  read result from wc */

        u_long uniqLines;
        pid_t pid;
        int   status;

        pipe(pipe1);

        pid = fork();

        if(pid == 0) {

                /*
                 * Child Process - sort
                 */

                close(1);
                dup(pipe1[1]);
                close(pipe1[0]);
                close(pipe1[1]);
                execlp("sort","sort","work.fp.big",NULL);

        } else {
                /*
                 * Parent Process
                 */

                pipe(pipe2);

                if (!fork()) {

                        /*
                         *     uniq
                         */       
                        close(0);
                        dup(pipe1[0]);
                        close(1);
                        dup(pipe2[1]);
                        close(pipe1[0]);
                        close(pipe1[1]);
                        close(pipe2[0]);
                        close(pipe2[1]);
                        execlp("uniq","uniq","-c",NULL);

                } else {

                        pipe(pipe3);

                        if (!fork()) {

                               /*
                                 *      wc
                                 */

                                close(0);
                                dup(pipe2[0]);
                                close(1);
                                dup(pipe3[1]);
                                close(pipe1[0]);
                                close(pipe1[1]);
                                close(pipe2[0]);
                                close(pipe2[1]);
                                close(pipe3[0]);
                                close(pipe3[1]);
                                execlp("wc","wc","-l",NULL);

                        } else {
                                close(0);
                                dup(pipe3[0]);
                                close(pipe1[0]);
                                close(pipe1[1]);
                                close(pipe2[0]);
                                close(pipe2[1]);
                                close(pipe3[0]);
                                close(pipe3[1]);
                                scanf("%lu",&uniqLines);
                        }

                }

                       /*
                        * Get status of sort
                        */

                        if (waitpid (pid, &status, 0) != pid) {
                                perror("waitpid");
                                fprintf(stderr, "\nstatus not available\n");
                        } else {
                                fprintf(stderr, "\n status = %d\n", status);
                        }

                        if ( WEXITSTATUS(status) == 0 ) {
                                  printf("Sort Success \n");
                        } else {
                                  printf("Sort failed \n");
                        }
                
        }


}