problems with scanf("%d\n",&i)

Question

For this code:

int i;
scanf("%d\n",&i);

I am not able to stop my program until I input two numbers.

I think it is very strange ,I know when the input is suitable,the scanf will return 1. When I input "12a 'Enter'","12 'Enter'2" and so on ,it is ok,the i=12,it seems that when I input something is different int or input a 'Enter' and something another,the scanf returns 1.

What am I missing?

I also added [tag:c++] tag since this behaviour is the same for both languages — LihO, Mar 01 '12 at 12:44
@LihO Although `scanf` is available in [tag:C++], using `istream`s would be more appropriate. Maybe the question should be left as just [tag:C]. — Peter Wood, Mar 01 '12 at 13:37

LihO · Answer 1 · 2012-03-01T13:14:39.603

14

"I am not able to stop my program until I input two numbers when I use scanf("%d\n",&i);"
Although this format makes scanf read the number and store it into i, this "reading" continues and it lasts till non-whitespace character followed by \n is found. This is the reason why input 1 2 makes this scanf stop.

You should not specify newline in the input format in this case. Use scanf("%d",&i); instead.

edited Mar 01 '12 at 13:14

answered Mar 01 '12 at 12:27

LihO

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Thank you,I never do that,and I just want to know the reason. – Sphinx Mar 02 '12 at 06:50

score 3 · Answer 2 · answered May 09 '12 at 20:35

3

It's because of the '\n in the scanf... If you want to move into a new line, just put :

printf ("\n");

and it'll give u an empty line...

answered May 09 '12 at 20:35

score 0 · Answer 3 · answered Dec 03 '14 at 06:07

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scanf("%d\n",&i);

read the number till non-whitespace character appear(ignore all whitespace and '\n' after the number).

answered Dec 03 '14 at 06:07

huoyao

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problems with scanf("%d\n",&i)

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