Error with C Strings

Question

The phrase "TYPE THE STREET" should only appear immediately after being inserted what asks the "ENTER A NUMBER FOR CONTACT". What must have happened?

---

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


typedef struct aluno
{

char nome[50];
char nasc[10]; 
char tel[20];
char end[20]; 
char bairro[10]; 
char cidade[10];
char mae[20]; 
char pai[20];
} aluno;
      aluno CAD_ALUNO;

int main()
{

printf ("\n CADASTRO DE ALUNO:");

printf ("\n DIGITE O NOME DO ALUNO: ");
fgets(CAD_ALUNO.nome, 50, stdin);

printf (" DIGITE A DATA DE NASCIMENTO: ");
fgets(CAD_ALUNO.nasc, 10, stdin);

printf (" DIGITE UM NUMERO PARA CONTATO: ");
fgets(CAD_ALUNO.tel, 20, stdin);

printf (" DIGITE A RUA ");
fgets(CAD_ALUNO.end, 20, stdin);

printf (" DIGITE O BAIRRO ");
fgets(CAD_ALUNO.bairro, 10, stdin);

printf (" DIGITE A CIDADE ");
fgets(CAD_ALUNO.cidade, 10, stdin);

printf (" DIGITE O NOME DA MAE ");
fgets(CAD_ALUNO.mae, 20, stdin);

printf (" DIGITE O NOME DO PAI ");
fgets(CAD_ALUNO.pai, 20, stdin);

system ("pause");
return 0;
}

Answer 1

This problem you are having there is due to the fact of buffer keyboard not being clean, when you press enter gets a /n stored in the keyboard buffer, to end this error just clear the buffer.

For this use the function setbuf, it serves to assign a value to the buffer. In this case we will assign a null value, then before each fgets you give you will add the following setbuf (stdin, NULL);, because then you will be saying that you want to assign the value of NULL, that is, zero to stdin which is the keyboard buffer, such that its main stay that way:

int main()
{
printf ("\n CADASTRO DE ALUNO:");

printf ("\n DIGITE O NOME DO ALUNO: "); 
setbuf (stdin, NULL);
fgets(CAD_ALUNO.nome, 50, stdin); 

printf (" DIGITE A DATA DE NASCIMENTO: "); 
setbuf (stdin, NULL);
fgets(CAD_ALUNO.nasc, 10, stdin); 

printf (" DIGITE UM NUMERO PARA 
CONTATO: "); 
setbuf (stdin, NULL);
fgets(CAD_ALUNO.tel, 20, stdin); 

printf (" DIGITE A RUA ");
setbuf (stdin, NULL);
fgets(CAD_ALUNO.end, 20, stdin); 

printf (" DIGITE O BAIRRO "); 
setbuf (stdin, NULL);
fgets(CAD_ALUNO.bairro, 10, stdin); 

printf (" DIGITE A CIDADE "); 
setbuf (stdin, NULL);
fgets(CAD_ALUNO.cidade, 10, stdin); 

printf (" DIGITE O NOME DA MAE "); 
setbuf (stdin, NULL);
fgets(CAD_ALUNO.mae, 20, stdin); 

printf (" DIGITE O NOME DO PAI "); 
setbuf (stdin, NULL);
fgets(CAD_ALUNO.pai, 20, stdin);

system("pause");
returne 0;
}

This is the first step, plus by good programming practices take that global variable that you are using, and incorporate it into the main , because this way you have a code more beautiful and less susceptible to errors.

Plus it’s remarkable that when you type 3 APRIL 2001 you’re giving a buffer overflow, because you created a string, to store the date, of only 10 characters, remembering that the last one is reserved to the \0 soon you will only have 9 characters available, and this sentence, 03 APRIL 2001, has 20 counting on the \0, then you would need a larger string, ie to solve the second error just increase the size of the string to a more suitable size, I believe 30 is more than enough, after the changes your code will be like this:

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


typedef struct aluno
{

    char nome[50];
    char nasc[30];
    char tel[20];
    char end[20];
    char bairro[10];
    char cidade[10];
    char mae[20];
    char pai[20];
} aluno;

int main()
{
    aluno CAD_ALUNO;

    printf ("\n CADASTRO DE ALUNO:");

    printf ("\n DIGITE O NOME DO ALUNO: ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.nome, 50, stdin);

    printf (" DIGITE A DATA DE NASCIMENTO: ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.nasc, 30, stdin);

    printf (" DIGITE UM NUMERO PARA CONTATO: ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.tel, 20, stdin);

    printf (" DIGITE A RUA ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.end, 20, stdin);

    printf (" DIGITE O BAIRRO ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.bairro, 10, stdin);

    printf (" DIGITE A CIDADE ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.cidade, 10, stdin);

    printf (" DIGITE O NOME DA MAE ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.mae, 20, stdin);

    printf (" DIGITE O NOME DO PAI ");
    setbuf (stdin, NULL);
    fgets(CAD_ALUNO.pai, 20, stdin);

    system ("pause");
    return 0;
}

In addition there are also other ways to read a string with spaces, I particularly do not like the use of fgets for this, I prefer to use the scanf.

To be able to read everything \n with the scanf just do the following, scanf(" %[^\n]s", nome_da_string);, so you’re adding a condition in it saying it’s for him to read up the \n, that is, until the end of the line, also do not forget to put the space between the quotation marks (") and the percent (%), so you will not have buffer error, and will not have to clean the buffer, that way the code in the main would look like this:

int main()
{
    aluno CAD_ALUNO;

    printf ("\n CADASTRO DE ALUNO:");

    printf ("\n DIGITE O NOME DO ALUNO: ");
    scanf(" %[^\n]s", CAD_ALUNO.nome);

    printf (" DIGITE A DATA DE NASCIMENTO: ");
    scanf(" %[^\n]s", CAD_ALUNO.nasc);

    printf (" DIGITE UM NUMERO PARA CONTATO: ");
    scanf(" %[^\n]s", CAD_ALUNO.tel);

    printf (" DIGITE A RUA ");
    scanf(" %[^\n]s", CAD_ALUNO.end);

    printf (" DIGITE O BAIRRO ");
    scanf(" %[^\n]s", CAD_ALUNO.bairro);

    printf (" DIGITE A CIDADE ");
    scanf(" %[^\n]s", CAD_ALUNO.cidade);

    printf (" DIGITE O NOME DA MAE ");
    scanf(" %[^\n]s", CAD_ALUNO.mae);

    printf (" DIGITE O NOME DO PAI ");
    scanf(" %[^\n]s", CAD_ALUNO.pai);

    system ("pause");
    return 0;
}

I hope I’ve helped, anything just ask, and good luck in programming studies (^_^)/