Multiple Pipes, C++ - c++

Question

I've been stuck on an issue with my program and just hoping for any help at this point :(
or guidance towards the right direction. In my code, I'm implenting a mini shell in c++ where the user can pipe 2 or more processes together, yet an issue keeps coming up whenever I execute it. Only the first and last commands actually execute so say I run:
cat b.txt | sort | tail -2
only cat b.txt and tail -2 would execute.
Here is my attempt at the whole program, also referenced to this which helped me tremendously with the setup.
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <sstream>
#include <stdlib.h>
#include <sys/utsname.h>
#include <unistd.h>
using namespace std;
//this variable will take in the line of input submitted by the user
char buf[1024];
//PIDs for the two child processes
pid_t pid[300];
//these will be use to check the status of each child in the parent process
int status;
int status2;
int pid_num = 1;
//initializes the pipe
int pipeA[2] = {-1,-1};
int g = 0;
void first_command(int pipeA[], char * command[], bool pipeExists){
if(pipeExists){
dup2(pipeA[1], 1);
close(pipeA[0]);
}
// this will run command[0] as the file to execute, and command as the arg
execvp(command[0], command);
printf("Can not execute FIRST command, please enter a valid command \n");
exit(127);
}
void other_command(int pipeA[], char * command0[], int index){
dup2(pipeA[0], 0);
close(pipeA[1]);
execvp(command0[0], command0);
printf("Can not execute SECOND command, please enter a valid command\n");
exit(127);
}
void main_func() {
//stay inside the loop and keep asking the user for input until the user quits the program
while (fgets(buf,1024,stdin) != NULL){
//initialize a boolean to check if user wants to pipe something, set to false by default until we check with user
bool pipeExists = false;
//initialize this arrays to NULL so anything that store in them gets cleared out.
//these arrays will hold the commands that the user wants to carry out.
char * command[1024] = {NULL, NULL, NULL};
char *command0[1024] = {NULL, NULL, NULL};
char *command1[] = {NULL, NULL, NULL};
char *command2[] = {NULL, NULL, NULL};
char *command3[] = {NULL, NULL, NULL};
char ** my_commands[] = {
command0,
command1,
command2,
command3,
NULL
};
//Important to delete mark the last byte as 0 in our input
buf[strlen(buf) -1] = 0;
//initialize this number to zero to start save the tokens at this index
int index = 0;
//a char * to hold the token saved by strtok
char * ptr;
ptr = strtok(buf, " \"");
//Loop through 'buf' and save tokens accordingly
while(ptr != NULL){
// if the user types exit at any moment, the program will exit gracefully and terminate
if(strcmp( ptr, "exit" ) == 0){
exit(0);
}
//if ptr is equal to | user wants to pipe something and we change pipeExists to true
if(strcmp( ptr, "|" ) == 0){
pipeExists = true;
index= 0;
ptr = strtok(NULL, " ");
}
//enter here while user doesnt want to user pipes
if(!pipeExists){
command[index] = ptr;
ptr = strtok(NULL, " ");
index++;
}
//enter here if user want to use pipes
if(pipeExists){
command0[index] = ptr;
ptr = strtok(NULL, " ");
index++;
}
g++;
printf("%s %i\n", ptr, g);
}
for (int s = 0; my_commands[s] != NULL; s++) {
cout << command0[s] << " \n" << endl;
}
//if pipes exists then initialize it
if(pipeExists){
pipe(pipeA);
}
//create first child
if ((pid[0] = fork()) == 0) {
//pass in the pipe, commands and pipe to function to execute
first_command(pipeA, command, pipeExists);
}
else if(pid[0] < 0){
//error with child
cerr<<"error forking first child"<<endl;
}
// if pipe exists create a second process to execute the second part of the command
if(pipeExists){
for(int f = 0; my_commands[f] != NULL; f++) {
//create second child
if ((pid[f] = fork()) == 0) {
other_command(pipeA, command0, index);
}
else if(pid[f] < 0){
//error with second child
cerr<<"error forking child "<< pid_num << endl;
}
}
pid_num++;
}
//if the pipe was created then we close its ends
if(pipeExists){
for(int z = 0; z < pid_num; z++) {
close(pipeA[z]);
}
}
//wait for the first child that ALWAYS executes
if ( (pid[0] = waitpid(pid[0], &status, 0)) < 0)
cerr<<"error waiting for first child"<<endl;
//wait for the second child but only if user wanted to created to use piping
if(pipeExists){
for(int j = 1; j < pid_num; j++) {
if ( (pid[j] = waitpid(pid[j], &status2, 0)) < 0){
printf("Status: %d", pid[j]);
cerr<<"error waiting for child " << j <<endl;
}
}
}
pid_num = 1;
}//endwhile
}