Pressing enter in C input programm

Question

I've been trying to teach myself C off the website http://www.cprogramming.com/. I've come to the code which requires an input number.

Here is the code:

#include <stdio.h>

int main()
{
  int this_is_a_number;
  printf( "Please enter a number: " );
  scanf( "%d", &this_is_a_number );
  printf( "You entered %d", this_is_a_number );
  getchar();
  return 0;
}

However when I run this, and try to enter a number into the prompt, the command window just closes. Any help would greatly be appreciated.

Just run the program from a terminal and you don't need to mess around with "keeping a window open"... — Kerrek SB, Jan 12 '17 at 11:52
@KerrekSB, while your statement is true, this would just immediately lead to the slightly modified question why `getchar()` is not waiting. Nothing gained there... — Gerhardh, Jan 12 '17 at 12:30
@Gerhardh: I would welcome that as a full win for the site, since such a question would be precise and searchable. — Kerrek SB, Jan 12 '17 at 12:34
@KerrekSB ... precise, searchable and still a duplicate of docens nearly identical questions. That's not so much of a win for the site, I would say. — Gerhardh, Jan 12 '17 at 12:37

score 2 · Answer 1 · answered Jan 12 '17 at 11:51

2

scanf reads the number, but leaves the newline character you inputted in the input stream.

So getchar fetches it immediately instead of waiting for extra input.

You can add another call to getchar. It's probably the simplest solution for your simple program.

answered Jan 12 '17 at 11:51

StoryTeller - Unslander Monica

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score 1 · Answer 2 · answered Jan 12 '17 at 11:52

Use another getchar(); to consume the newline character left by the scanf() call; so that, the second getchar(); would hold the prompt.

getchar();
getchar();
...

Normally, you wouldn't need this. But if you are running exe (typically Windows) and want to wait at the end (which appears to be the case here), this trick would do.

Pressing enter in C input programm

2 Answers2