my c program freezes after asking for user input. Please help. I've tried everything

Question

#include<stdio.h>

int main()
{
    char firstname[40];
    char lastname[40];
    printf("what's your name? \n");
    scanf(" %s %s ", firstname, lastname);
    printf("hello there %s %s \n", firstname, lastname);
    return 0;
}

the program freezes after scanning firstname and lastname

looks fine for me https://godbolt.org/z/T3ejbx – 0___________ Feb 22 '21 at 21:00 — 0___________, Feb 22 '21 at 21:00

score 2 · Answer 1 · answered Feb 22 '21 at 20:58

2

The trailing space in your format string is consuming any whitespace after you enter the first and last names, which includes newlines. This means you would need to enter some non-whitespace after the first and last name before scanf returns.

Get rid of the spaces on either end of the format string.

scanf("%s %s", firstname, lastname);

answered Feb 22 '21 at 20:58

dbush

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woah.. I always though of trailing whitespace as harmless. – Eugene Sh. Feb 22 '21 at 21:00
3

@EugeneSh. Nothing's harmless when `scanf()` gets involved. I have no idea why that gets taught so much. No one uses it in real life - at least not for long. – Andrew Henle Feb 22 '21 at 21:01
The middle space is not needed in the format string either. The first and middle spaces are harmless; the trailing space is diabolical. – Jonathan Leffler Feb 22 '21 at 21:20

my c program freezes after asking for user input. Please help. I've tried everything

1 Answers1