C Program Working Fine on Windows, Segmentation Fault on Linux

I'm writting a program in C Language and it works perfect on Windows, but gives me Segmentation Fault when selecting function 3 (settings) in the main menu. Why?

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

#ifdef _WIN32
#define CLEAR "cls"
#else
#define CLEAR "clear"
#endif


char characters[11];
int lines, columns; 
float base_score; 
FILE *fp;

void helloworld(){ 
    printf("Welcome!n");
    printf("Press <ENTER> to continue...");
    while( getchar() != 'n' ) getchar();   
}

int menuMain() { 
    int option;

    printf("MAIN MENUn");
    printf("1 - Playn");
    printf("2 - Rankingn");
    printf("3 - Settingsn");
    printf("4 - Leaven");
    printf("n");
    printf("Choose:");

    scanf("%d", &option);
    while((option!=1)&&(option!=2)&&(option!=3)&&(option!=4)) {
        printf("Invalid selection. Try again please.n");
        printf("Press <ENTER> to continue...n");
        while( getchar() != 'n' );
        getchar();  
        system(CLEAR);
        menuMain();

    }
    return option;
}

void play () {
    printf("Under construction...n");
}

void ranking () {
    printf("Under construction...n");
}


void settings();

typedef enum {
 false = 0,
 true,
} bool;

bool invalidChars() {
    if((strlen(characters)<3)||(strlen(characters)>10)) return true;
    else return false;
}

bool invalidRows() {
    if((lines<3)||(lines>9)) return true;
    else return false;

}

bool invalidCols() {
    if((lines<3)||(lines>9)) return true;
    else return false;
}

bool invalidScoreBase() {
    if((base_score<1)||(base_score>2)) return true;
    else return false;
}

int settingsMain() { 
    int option; 

    printf("SETTINGSn");
    printf("1 - Change characters: %sn", characters);
    printf("2 - Change lines: %dn", lines);
    printf("3 - Change columns: %dn", columns);
    printf("4 - Change base score: %.2fn", base_score);
    printf("5 - Main menun");
    printf("n");
    printf("Choose:");

    scanf("%d", &option);
    if((option!=1)&&(option!=2)&&(option!=3)&&(option!=4)&&(option!=5)) { 
        printf("Invalid selection. Try again please.n");
        printf("Press <ENTER> to continue...");
        while( getchar() != 'n' );
        getchar();  
        system(CLEAR); 
        settings(); 

    }
    return option;
}

void writesettings(FILE *fp) { 
    fprintf(fp, "%sn%dn%dn%fn", characters, lines, columns, base_score);
}

void readsettings() { 
    fp = fopen("EliminaLetras_settings.txt", "r+");
    if (fp == NULL) {
        strcpy(characters, "OZXM");
        lines = 6;
        columns = 9; 
        base_score = 1.5;
        writesettings(fp);
    }
    else {
        fscanf(fp, "%sn%dn%dn%fn", characters, &lines, &columns, &base_score);
        rewind(fp);
        writesettings(fp);
    }
    fclose(fp);
}

void changeChars() {
    char op;
    bool test;
    printf("Insert new characters(min 3, max 10):");
    scanf("%s", characters);
    printf("Confirm? (Y/N)?");
    scanf(" %c", &op);
    getchar();
    if((op == 'Y')||(op == 'y')) {
        test = invalidChars();
        if (test == true) {
            printf("Invalid selection. Try again please.n");
            changeChars();
        }
        else {
            fp = fopen("EliminaLetras_settings.txt", "w+");
            writesettings(fp);
            fclose(fp);
        }
    }
}
void changeRows() {
    char op;
    bool test;
    printf("Insert new number of lines(min 3, max 9):");
    scanf("%d", &lines);
    printf("Confirm? (Y/N)?");
    scanf(" %c", &op);
    getchar();
    if((op == 'Y')||(op == 'y')) {
        test = invalidRows();
        if (test == true) {
            printf("Invalid selection. Try again please.n");
            changeRows();
        }
        else {
            fp = fopen("EliminaLetras_settings.txt", "w+");
            writesettings(fp);
            fclose(fp);
        }
    }
}
void changeCols() {
    char op;
    bool test;
    printf("Insert new number of columns (min 3, max 9):");
    scanf("%d", &columns);
    printf("Confirm (Y/N)?");
    scanf(" %c", &op);
    getchar();
    if((op == 'Y')||(op == 'y')) {
        test = invalidCols();
        if (test == true) {
            printf("Invalid selection. Try again please.n");
            changeCols();
        }
        else {
            fp = fopen("EliminaLetras_settings.txt", "w+");
            writesettings(fp);
            fclose(fp);
        }
    }
}
void changeScoreBase() {
    char op;
    bool test;
    printf("Insert new base score (min 1, max 2):");
    scanf("%f", &base_score);
    printf("Confirm? (Y/N)?");
    scanf(" %c", &op);
    getchar();
    if((op == 'Y')||(op == 'y')) {
        test = invalidScoreBase();
        if (test == true) {
            printf("Invalid selection. Try again please.n");
            changeScoreBase();
        }
        else {
            fp = fopen("EliminaLetras_settings.txt", "w+");
            writesettings(fp);
            fclose(fp);
        }
    }
}

void settings () {  
    int op = 0; 
    readsettings();
    op = settingsMain();
    switch (op) {
        case 1:
            changeChars();
            system(CLEAR);
            settings();
            break;
        case 2:
            changeRows(); 
            system(CLEAR);
            settings();
            break;
        case 3:
            changeCols(); 
            system(CLEAR);
            settings();
            break;
        case 4:
            changeScoreBase();
            system(CLEAR);
            settings();
            break;
        case 5:
            system(CLEAR);
            getchar();
            main ();
            break;  
    }
}


void quit () {
    printf("Goodbye!n");
    printf("Press <ENTER> to continue...");
    while(getchar() != 'n');
    getchar();
}


int main () {
    int op;
    helloworld();
    system(CLEAR);
    op = menuMain();
    switch (op) {
        case 1:
            system(CLEAR);
            play();
            break;
        case 2:
            system(CLEAR);
            ranking();
            break;
        case 3:
            system(CLEAR);
            settings();
            break;
        case 4:
            system(CLEAR);
            quit();
            break;
    }
    return 0;
}

Sorry for the long code, but I really have no clue as to where is my mistake. My best guess is it is either on the "settings" function or main itself. Any help would be greatly appreciated.