Error '''Segmentation fault core dumped'' in C

Question

I’m a little new, but I haven’t been able to solve that problem yet, so I came to you. I use linux and I have a problem with the code I made (it’s very simple).

The code reads a number and transforms it into a letter (at least it was supposed to happen this) but is showing the following error at the end: segmentation fault core dumped.

Follows the code:

#include <stdio.h>

#include <stdlib.h>

#include <locale.h>

char nome [20];

int num;

void main(){

setlocale(LC_ALL, ("Portuguese"));

    printf(" \t\tLETRA DO ALFABETO\n ");
    printf(" \n\nOlá, digite aqui seu nome: ");
    fgets (nome, sizeof (nome), stdin);
    fflush(stdin);

        system("clear");


    printf(" \n\nOlá %s,digite aqui o número para saber qua letra ele representa: ",nome);
    scanf("%d", &num);

        system("clear");

    printf("\n\n %s, o número %d representa a letra %s\n\n",nome,num,(char)num);



return 0;

}

If you have any suggestions for code improvement, I also accept.

Answer 1

Swapping %s for %c should solve the problem since you are trying to print a single character and not a string, as already mentioned by the staff. Just make sure to report a valid value from the ASCII table (remembering that characters from 0 to 31 cannot be printed).

As improvement suggestions I would change void main to int main(), since you is returning 0 at the end of the program (or else remove Return 0), remove the system("clear") function calls if they are not necessary because they are platform dependent (this code would not work in windows, for example, that uses the cls command),use fgets to read the whole, so you wouldn’t need to more of the fflush() function (but for that you would have to convert a string into integer using atoi, for example), define a macro with the size string maximum (making it easier to change its size later), put the name and one variables inside the main function and remove the line break at the end of the string returned by fgets, so the program does not skip a line after writing the name.

Follow the code with the suggested improvements:

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <string.h> // para usar a função strlen()

#define TAMANHO_STR 20

int main()
{
    char nome[TAMANHO_STR+1];
    char num_str[TAMANHO_STR+1];
    int num;

    setlocale(LC_ALL, ("Portuguese"));

    printf("\t\tLETRA DO ALFABETO\n ");
    printf("\n\nOlá, digite aqui seu nome: ");
    fgets(nome, TAMANHO_STR+1, stdin);

    int l = strlen(nome); // descobre o comprimento da string
    if (l > 0 && nome[l-1] == '\n') // se a string não é vazia e o último caractere é \n
        nome[l-1] = 0; // define último caractere como \0

    printf(" \n\nOlá %s, digite aqui o número para saber qua letra ele representa: ",nome);

    fgets(num_str, TAMANHO_STR+1, stdin);
    num = atoi(num_str);

    printf("\n\n%s, o número %d representa a letra %c\n\n", nome, num, (char) num);

    return 0;
}

Note that the last character of every string in C is 0, so set the length of the strings to TAMANHO_STR+1 and replace the penultimate character with 0.

Edit: As well remembered by a comment here, I forgot to explain that function fgets saved in the string the line break character \n, if it fits. That is, if you type as input abc the string will receive abc\n\0 (if the string has 5 or more characters in this example). To remove this, the program finds the penultimate character and changes it to \0, so the string can be printed without line break.