CODEWITHSUNDEEP
c++visual-studioscanf
Viodentia
Viodentia

Reputation: 37

Scanf_s is empty in c++

I can't use this code because I can't write any text. How can i solve this problem with reading?

#include "stdafx.h"
#include "stdio.h"
#include "conio.h"
#include "string.h"




int _tmain(int argc, _TCHAR* argv[])
{
    char str[1024];

    printf("Input text: ");
    scanf_s("%c", str);

    _asm                                                                                                                                                                                                                                        
    {
    //some assembly code
    }


    printf("\n\nResult = %s", str);

    printf("\n\n[Press any key]");
    _getch();

    return 0;
}

result is

Input text: sdf

Result =

[Press any key]

any ideas? I use Visual Studio 2013.

Upvotes: 1

Views: 5151

Answers (4)

Dr4n1m4t0r
Dr4n1m4t0r

Reputation: 1

I had the same problem, I gathered several answers and I got the user to write his name with spaces and numbers, Thanks!

"#include "stdafx.h"

"#include < iostream >"

"#include < stdio.h >"

"#include < locale.h >"

using namespace std;

int main()

{

    setlocale(LC_ALL, "spanish");

    char a [100];

    printf_s("\n Programa para la práctica de scanf_s ");
    printf_s("\n Introduzca su nombre completo: ");
    scanf_s("%[0-9a-zA-Z        ]s", &a, 100);
    printf_s("\n ¡Bienvenido! Sr. %s", a);

    cout << " \n This is a white space\n "<<a;
    system("PAUSE()");
    return 0;
}

Upvotes: 0

Digital_Reality
Digital_Reality

Reputation: 4738

Use as below..

scanf("%[0-9a-zA-Z ]s", str);

%c will only read one char from input value.

%s will read one word (till whitespaces)

scanf %s

Any number of non-whitespace characters, stopping at the first whitespace character found. A terminating null character is automatically added at the end of the stored sequence.

Upvotes: 0

user3072164
user3072164

Reputation:

I didn't know the function scanf_s, so I looked up the documentation. It notes, that in constrast to scanf for scanf_s buffer sizes need to be specified for format specifiers c, C, s and S as a second parameter following the usual one. An example:

char str[1024];

printf("Input text: ");
scanf_s("%s", str, 1024);

The documentation also states that in case of potential buffer overflow nothing is written to the buffer.

Upvotes: 4

simonc
simonc

Reputation: 42165

The %c format specifier in

scanf_s("%c", str);

requests that a single char is read.

printf("\n\nResult = %s", str);

later requests that the contents of str until the first char with value '\0' are printed. This results in undefined behaviour since you only initialised the first element of str. You may sometimes manage to print a range of stack memory; other times your program will crash.

Assuming you want to read a nul-terminated array of chars, you need to use the %s format specifier when reading user input instead:

scanf_s("%s", str);

Upvotes: 2

Related Questions