Thread: Reading number of digits

I need my program to be able to read how many digits are in a number that is input by the user.

For example, I'm looking for something like:

Code:

if (digits = 10) {
.... do something....
} else {
... do something else....
}

Of course, the parts in brackets are not correct code for c. I just don't know how to interpret this from English to C.

Thanks for any help!

Sorry that's not quite what I'm looking for. I should have been more clear.

I have a large number (a barcode) that I have used getchar to find each digit. However, sometimes the user might not include the 13th digit in a barcode, because that is a checksum digit that I will need to calculate.

The problem is, I can't do the division by 10 and use a counter because I have declared each digit rather than the entire barcode number as a whole.

So how can I translate:

Code:

if (thirteenth digit exists)
.....
else
.....

Ok, let me just backtrack a bit. Are you saying that the user inputs 12 characters which are digits and may input a 13th digit or another character? If so check if that character is a digit by attempting to to convert it into an integer with atoi(). If atoi fails it will return 0 and then you will know it's not an integer.

Originally Posted by Mentallic

Sorry that's not quite what I'm looking for. I should have been more clear.

I have a large number (a barcode) that I have used getchar to find each digit. However, sometimes the user might not include the 13th digit in a barcode, because that is a checksum digit that I will need to calculate.

The problem is, I can't do the division by 10 and use a counter because I have declared each digit rather than the entire barcode number as a whole.

So how can I translate:

Code:

if (thirteenth digit exists)
.....
else
.....

So how are you reading in the data? If you're reading in character-by-character, well, then you know how many characters you read and we're done.

No, the user may input a 12 or 13 digit number. I do have the issue with when they're character rather than digits, but I've asked for help with that problem in another thread.

I am finding the digits separately in that large 12/13 digit number with getchar(). I just don't know how to test whether there are 13 digits or not.

Maybe something like:

Code:

if (thirteenth_Digit >= '0' && thirteenth_Digit <= '9') {
    thirteenth_Digit = getchar ();
} else {
    ......
}

Originally Posted by tabstop

So how are you reading in the data? If you're reading in character-by-character, well, then you know how many characters you read and we're done.

How do I know how many characters I've read?

If you are reading characters one by one just a use a counter. I really don't see what your actual problem is. Maybe you should post the code you have so far and leave commented the part you can't work out.