Problem with scanf

Question

Possible Duplicate:
Simple C scanf does not work?

Why does scanf("%c", &letter); not working. the rest is working

#include <stdio.h>

main(){
    int number;
    float number1;
    char letter;
    char letter2 [5];

    printf("Enter an int: ");
    scanf("%d", &number);
    printf("Enter a float: ");
    scanf("%f", &number1);
    printf("Enter a letter: ");
    scanf("%c", &letter);
    printf("Enter a string: ");
    scanf("%s", letter2);

    printf("INT = %d\n", number);
    printf("FLOAT = %f\n", number1);
    printf("LETTER = %c\n", letter);
    printf("LETTER2= %s\n", letter2);

    getch();
}

what do you mean by not working? does the program crash? or the pritf result for letter is not the desirable? Then what is the result? — Vladimir Ivanov, Dec 06 '10 at 12:43
I think `scanf` leaves the `\n` in the buffer and `letter` becomes `\n`. Not sure though. — khachik, Dec 06 '10 at 12:44
From what sample says it looks like Khachik is on the money here. TBH I have never, in over a decade of C programming, used scanf(). In this case it might be neater to do fgets() on stdin and use atoi or some similar function. One advantage is that then you can perform checks on the input to make sure it is correct/what you expect. — AlastairG, Dec 06 '10 at 12:46
possible duplicate of [Simple C scanf does not work?](http://stackoverflow.com/questions/3744776/simple-c-scanf-does-not-work) (among several others - try a SO search for scanf) — The Archetypal Paul, Dec 06 '10 at 12:47

score 4 · Accepted Answer · edited May 23 '17 at 12:10

4

This is because the newline (return key) after feeding float is counted as a character.

This is not a bug but it is due to fact that "\n" is considered a character in C and if you have to ignore it, you need to do that manually.

The simplest solution for your case is to eat up the newline as follows:

scanf("%f", &number1);
getchar();

This Link will help.

edited May 23 '17 at 12:10

Community

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answered Dec 06 '10 at 12:47

sud03r

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@sample: No, please see the link provided by Paul in the comment, your question is a duplicate of the other question. – Bobby Dec 06 '10 at 12:54
@sample c is most robust language thats why it is use for device drivers.How you can say that c having problem. – Ishu Dec 06 '10 at 12:56

score 3 · Answer 2 · answered Dec 06 '10 at 12:49

3

scanf reads the whitespace that is left in the buffer from the previous line. To skip the whitespace, add a space to the scanf:

scanf(" %c", &letter);

The space means "skip whitespace" and the the %c means "read the following character.

answered Dec 06 '10 at 12:49

Yakov Galka

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is it a bug in c? or does it serves another purpose? – sample Dec 06 '10 at 12:52
1

@sample: c can't have bugs, it's not a program, it's a language. And not, It's meant to be that way. – Yakov Galka Dec 06 '10 at 12:53
@sample [no](http://programmers.stackexchange.com/questions/24022/rulesmaxims-for-programmers/24026#24026) – khachik Dec 06 '10 at 12:54

Problem with scanf

2 Answers2