How to prevent users from inputting letters or numbers?

Question

I have a simple problem;

Here is the code :

#include
main(){
 int input;
 printf(\"Choose a numeric value\");
 scanf(\"%d\",&input         


        

Answer 1

Personally, I would read the input into a buffer and scan that string for my number.

char buffer[100];
float value;
do {
scanf("%s", buffer);
} while ( sscanf(buffer,"%f", &value) != 1 )

This will loop until the first thing the user enters on the line is a number. The input could be anything but will only get past this block when the first thing entered is a number.
example input:
43289 (value is 43289)
43.33 (value is 43.44)
392gifah (value is 392)
ajfgds432 (continues to loop)