void checkFile(const char *key, const char *st)
    {
        // Opening files:
        // create file path strings
        char *keyPath = malloc((PATH_SZ+strlen(key)) * sizeof(char));
        if (!keyPath) die("Failed to follow key path");
        memcpy(keyPath, PATH, PATH_SZ);
        memcpy(keyPath+PATH_SZ, key, strlen(key));

        char *stPath =  malloc((PATH_SZ+strlen(st)) * sizeof(char));
        if (!stPath) die("Failed to follow key path");
        memcpy(stPath, PATH, PATH_SZ);
        memcpy(stPath+PATH_SZ, st, strlen(st));

        // open files
        FILE *keyFile = fopen(keyPath, "r");
        if (!keyFile) die("Failed to open key file");

        FILE *stFile = fopen(stPath, "r");
        if (!stFile) die("Failed to open student file");

        // Comparing files:
        char keyLine[LINE_SZ];  // strings of each line of the file
        char stLine[LINE_SZ];

        // compare first lines
        int cont = 1;
        float grade;
        fgets(keyLine, LINE_SZ, keyFile);
        fgets(stLine, LINE_SZ, stFile);
        if (strcmp(stLine, keyLine) != 0) {
            cont = 0;
            grade = 0;
            // fprintf(stdout, "%s.2f\n",  "Grade:", grade);
            printf("Grade:.2f\n", grade);
        }

        if (cont == 1) {
            int correct = 1;
            int total = 1;
            // compare the rest of the lines
            while (fgets(keyLine, LINE_SZ, keyFile)) {
                fgets(stLine, LINE_SZ, stFile);
                if (strcmp(keyLine, stLine) == 0) {
                    correct++;  // if lines are the same inc num correct
                }
                total++;
            }
            grade = round((float) correct / total * 100);
            // fprintf(stdout, "%s.2f\n",  "Grade:", grade);
            printf("Grade:.2f\n", grade);
        }

        //Cleanup:
        free(keyPath);
        free(stPath);
        fclose(keyFile);
        fclose(stFile);
    }