Question

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How to scanf only integer and repeat reading if the user enter non numeric characters?

Hi i’m new to c and i am writing a program that asks the user to enter an integer and if it does not match the criteria of being within a certain range, like lass than 20, but greater than 5. It asks the user to enter the value again.

However i wondered what would happen if i entered a character, and well it creates an infinite loop.

So i want to know is there a way or a specific function that will check the entered value to see if it is the correct data type. And i not repromts the user.

Answer 1

you can read with scanf("%d") and if the user enter a string containing a non numeric character then you have to clean the stdin buffer before reading again with scanf("%d").

when you clean the stdin, you will stop the infinite loop

Use the following function to clean your stdin

int clean_stdin()
{
    while (getchar()!='\n');
    return 1;
}

And The read of your integer from stdin could be done in this way:

char c;
do
{  
    printf("\nEnter an integer from 5 to 20: ");

} while (((scanf("%d%c", &rows, &c)!=2 || c!='\n') && clean_stdin()) || rows<5 || rows>20);