使用scanf（）时如何区分整数和字符

Question

I am just using the function scanf() . The code is below:

scanf("%d",&a);
printf("%d",a);

When I input 1, it prints 1 like I want. But even when I input 1a, it print 1 like before. when a user inputs something not integer ((ex) 2.3,12ab,1 a) I want to show a user the warning like "input integer".

How can I solve this problem?

Answer 1

Read it all into a string with fgets() .

If you just want everything they enter to be a single int , walk the string and look for isdigit() on each char and then when you find that it is all just digits, call strtod() , if not, emit an error and re-prompt.

If you want multiple things parse from the same input line, then you need to parse the string with something like strtok() to get individual tokens one at a time, then look at each token and determine if it is a number by looking to see if each character isdigit() or is equal to '-' '.' and suchlike. If so, parse it as a number with strtol() or strtod() (etc) (depending on what you see, int or float/double.) Otherwise, parse the token as a string or emit an error.