inability to input sentences with white space

Question

I'm trying to make the 20 questions game using c. The following is the code excerpt of one of the functions.

int question_input(void)
{
    char q[100];
    int i=0;
    printf("Enter the question or say if you want to guess\n");
    scanf("%[^\n]",q);
    i=check_if_guess(q);
    if(i==0)
    {
        printf("Say yes or no\n");
        scanf("%s",q);
    }
    return i;
}

I get a general protection fault when I execute and on debugging, I found that the problem is with the

scanf("%[^\n]",q)

statement.

If the same statement is changed to "%s", then, I get no segmentation fault. Functions like gets (general protection fault) and fgets(doesn't ask for input at all) also fail to take inputs.

The thing which is more curious is that when I execute these statements in a seperate file, without the rest of the code, they execute properly.

Even if I try "%99[^\r\n]", it shows the same.

Please help

this might help http://stackoverflow.com/questions/13726499/how-can-i-scan-strings-with-spaces-in-them-using-scanf — Derlin, Apr 10 '17 at 14:59
Possible duplicate of [How can I scan strings with spaces in them using scanf()?](http://stackoverflow.com/questions/13726499/how-can-i-scan-strings-with-spaces-in-them-using-scanf) — Gaurav Pathak, Apr 10 '17 at 15:00
`scanf("%[^\n]",q);` --> `fgets(q, sizeof q, stdin); q[strcspn(q,"\n"]=0;` — chux - Reinstate Monica, Apr 10 '17 at 15:08
Do not mix `scanf()` with `fgets()`. Best to just use `fgets()`. — chux - Reinstate Monica, Apr 10 '17 at 15:10
@ameyCU The error is with the statement before the check_if_guess function. Hence I don't think, it is required. So please help with this. — Siddharth Kailasam, Apr 10 '17 at 15:11
This is bad because you do not limit input to the size of buffer and fail to test the return value of `scanf`. And misuses `scanf` where `fgets` should be used. But it should not be enough to have a general protection fault. Please show a [mcve]. — Serge Ballesta, Apr 10 '17 at 15:14
@Derlin and Gaurav Pathak I tried "%99[^\r\n]" just now. It still didn't work. — Siddharth Kailasam, Apr 10 '17 at 15:15
@ChrisTurner and chux, I did try using fgets also. It didn't even take an input from me. Just skipped it. — Siddharth Kailasam, Apr 10 '17 at 15:18
Can you provide the full code? We might be able to spot something. gets or fgets not taking input is not normal. — Mohammed Bakr Sikal, Apr 10 '17 at 15:23
@ChrisTurner I just replaced the scanf statement with fgets(q,100,stdin) — Siddharth Kailasam, Apr 10 '17 at 15:39
@SiddharthKailasam that is right, so it must be something to do with the rest of your code. maybe you're not processing the `\n` from the previous line first? — Chris Turner, Apr 10 '17 at 15:41
@MohammedBakrSikal Pls share ur mail id so that I could mail u the code — Siddharth Kailasam, Apr 10 '17 at 15:41
@SiddharthKailasam replace the spaces in my name with dots, and the rest is gmail generic stuff — Mohammed Bakr Sikal, Apr 10 '17 at 15:43
@SiddharthKailasam `fgets` stops as soon as it gets a `\n` or it runs out of buffer space. because we can't see the rest of your code, we don't know what else it is doing - it might be reading in part of a line and then calling this function. — Chris Turner, Apr 10 '17 at 15:50
@ChrisTurne rpls send me ur mail id also, so that I can send it to u too — Siddharth Kailasam, Apr 10 '17 at 15:58

score 0 · Answer 1 · answered Apr 13 '17 at 14:27

Well, I found an answer to my question by myself. One of my previous functions in my code had

scanf("%d",&n)

It is a known fact that after we enter our input we press the enter key. This is taken as a '\n' by the compiler and is stored in the buffer. My next scanf statement( the one which I got error in)(scanf("%[^\n]",q) straight away took the '\n' from the buffer. Hence it could not take any input, since \n terminates input. The compiler I use is turbo C++. In some cases of empty strings, it reports an error. Hence I got the error message. To solve this problem, I had to use

getchar()

statement before the scanf("%[^\n]",q) statement, so that the '\n' is removed from the buffer and taken as an input for the getchar statement.

inability to input sentences with white space

1 Answers1