C validating input char

You can read a character string from the user with scanf, then convert it to an integer with strtol.

For example, try the following program: Test it with 123, then with 123abc.

We'll use scanf here, but will make sure that the item entered is actually a single-digit integer.

What if you want to make sure that the user enter a number of valid length?

At this point, nothing stops the user from entering the entire text of War and Peace as one long string!

As per our code, nothing bad would happen if you enter garbage.

Hi fellows, i started learning C in college but i m kind new to it.. I usually code python and php, and both have functions to do it, like is_numeric in php or isdigit() in python, but i dont know if C have one.

And another question is: i wrote some simple apps here and in windows at college they were using getch() but it didnt work in linux, so i read that i had to change that to getchar() but getchar() isnt waiting for user input at all, is there any other way to wait for a user to press a key before exiting the app?

I taught computer science at a university for over 20 years.

Let's say you are asking for a 3-digit security code; not only do we need to check for an integer, but an integer whose length is 3 digits.

The following code makes sure that the user enters a 3-digit number.

There are many ways to validate a user input, let's start with a straightforward solution that uses one of the C standard libraries.

The stdlib.h is a header file that imports the C standard library (stdlib).

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