strstr() and exit(0) trouble in C

so I’m working on a simulated linux shell using C (homework), and I have it exiting the program if the user just simply types in “quit”.

However, if they throw “exit” somewhere inside a command… “cat file ; exit”

I need it to execute the command like normal, then quit.

I know that I still have to filter the string entered and strip it of the exit, but for now, I’m just simply trying to get it to recognize the substring of “exit” using strstr() and to exit the program. It just keeps looping if input contains a string with substring “exit” currently.

Thank you.

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

#define bSize 1000

void driveLoop();
char *userInput(void);

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

    driveLoop();

    return 0;

}

void driveLoop(void){
    char *comTokens[100];
    char *tempTokens;
    char *command;
    char *cd;
    char *cdDir;
    char *cdTemp;
    char cdBuf[bSize];
    char checkExit[] = "exit";

    for (;;){

        printf("> ");
        command = userInput();

        if (!command)
            break;

        char *exitPtr = strstr(command, checkExit); // using strstr on the pointer containing the input

        int i = 0;
        tempTokens = strtok(command, " tn");

        while (tempTokens && i < 99){
            comTokens[i++] = tempTokens;
            tempTokens = strtok(NULL, "tn");
        }

        if (strcmp(comTokens[0], "exit") == 0){ // this exit is working normally
          exit(0);
        }

        if (strcmp(comTokens[0], "cd") == 0){
            cd = getcwd(cdBuf, sizeof(cdBuf));
            cdDir = strcat(cd, "/");
            cdTemp = strcat(cdDir, comTokens[1]);
            continue;
        }

        comTokens[i] = NULL;

        pid_t cFork = fork();

        if (cFork == (pid_t) - 1){
            perror("fork");
        }

        else if (cFork == 0){
            execvp(comTokens[0], comTokens);
            perror("exec");

            if (exitPtr != NULL){ // here's where I'm calling the exit
                exit(0); // nothing happens though. It just keeps looping.
            }
        }

        else {
            int status;
            waitpid(cFork, &status, 0);
        }
    }
}

char *userInput(void){
    char *input = NULL;
    size_t size = 0;
    getline(&input, &size, stdin);
    return input;
}

Answer

    else if (cFork == 0){
        execvp(comTokens[0], comTokens);
        perror("exec");

        if (exitPtr != NULL){ // here's where I'm calling the exit
            exit(0); // nothing happens though. It just keeps looping.
        }
    }

execvp doesn’t return if it succeeds, so your if will normally never be executed. (And if execvp does return, you probably want to exit the child unconditionally, preferably with _exit().)

What you really want is for the parent process to exit. So you probably wanted to put this code in the parent branch of the fork:

    else {
        int status;
        waitpid(cFork, &status, 0);
        // add it here
        if (exitPtr != NULL){
            exit(0);
        }

    }