Reading character using scanf

Question

Can someone please explain me why the scanf behaves differently in these two programs. I have prepared a sample test program to demo it.

Program Version 1

#include <stdio.h>

int main()
{
  int i;
  char c;
  for(i=0;i<4;i++)
  {
    scanf("%c",&c);
    printf("%c",c);
  }
return 0;
}

Program Version 2 (see scanf)

#include <stdio.h>

int main()
{
  int i;
  char c;
  for(i=0;i<4;i++)
  {
    scanf(" %c",&c); //The only difference is space
    printf("%c",c);
  }
return 0;
}

In program 1 I can enter
a
b
c
d

But in program 2 I can only enter
a
b

Why?

Please read the [man-page for `scanf`](http://man7.org/linux/man-pages/man3/scanf.3.html). — Deduplicator, Aug 08 '14 at 16:14
Are you sure that's the behavior of the programs? Seems like it should be the other way around. — Drew McGowen, Aug 08 '14 at 16:15

programmerjake · Answer 1 · 2014-08-08T16:10:17.723

1

the space in scanf means to skip whitespace characters at that point in the format string.

for the version without the space, the parsed characters are 'a', '\n', 'b', '\n'

for the version with the space, the parsed characters are 'a', skipped whitespace, 'b', skipped whitespace, 'c', skipped whitespace, 'd'

edited Aug 08 '14 at 16:10

answered Aug 08 '14 at 16:05

programmerjake

1,794
11
15

score -1 · Answer 2 · answered Aug 08 '14 at 16:15

-1

So going off of what programmerjake said, in the second program the white spaces are assigned to the i variable. a + space + b + space and then the loop stops.

answered Aug 08 '14 at 16:15

Mexicutioner91

21
5

1

You just described the exact opposite of what @programmerjake stated. – Drew McGowen Aug 08 '14 at 16:17

Reading character using scanf

2 Answers2