Regex data validation for input containing only the digits

Question

I'm trying to prompt the user to input a data value, and check that the string they enter only contains the digits 0-9:

class String
    def validate(regex)
        !self[regex].nil?
    end
end

regex = /\A[0-9]\z/

validInput = false
until validInput
    puts "Enter digits: "
    input = gets.chomp
    if !input.validate(regex)
        puts "Invalid input. Seeking integer."
    else
        validInput = true

    end
end

However this loop returns false on everything other than single digits excluding 0. I previously had this working with regex = /\A[1-9]\z/, but I going back to where it was working, it doesn't anymore, and this also means the user can't enter 0.

How can I use a regex to validate that user input only contains the digits 0-9?

Why are those new to SO in such a rush to select an answer? Take it easy. Give it some time. There's no rush. You don't want to discourage other answers and have some consideration for members still working on their answers. — Cary Swoveland
– Cary Swoveland, Commented Jun 29, 2015 at 6:45

Anshul Rai · Accepted Answer · 2015-06-29 07:39:59Z

2

Add a + quantifier after [1-9](Shouldn't it be [0-9] is you want digits from 0 to 9?). i.e. regex = /\A[0-9]+\z/

You can represent the character class [0-9] as \d so that the regex looks neater: \A\d+\z

The + checks for one(minimum) or more occurrences of a digit in the string. Right now, you are checking for presence of only ONE digit.

edited Jun 29, 2015 at 7:39

answered Jun 29, 2015 at 6:23

Anshul Rai

7827 silver badges22 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Nemo Over a year ago

Thanks for this :) Accept in 7 mins

Anshul Rai Over a year ago

@AvinashRaj OP asked for "regex to validate that user input only contains the digits 0-9?"

Cary Swoveland Over a year ago

/\A[0-9]+\z/ is customarily written /\A\d+\z/.

Nemo Over a year ago

How can I extend this to include a single decimal point (.)? So the user can enter 10.2 but not 10.2.2 or 10..2

Anshul Rai Over a year ago

@Nemo Modify it to \A[0-9]+(\.[0-9]+)?\z, here the ? is a quantifier that matches for either no occurrence or one occurrence. \A\d+(\.\d+)?\z looks neater though. :)

|

sawa · Accepted Answer · 2015-06-29 06:44:14Z

1

s !~ /\D/

.....................

answered Jun 29, 2015 at 6:44

sawa

169k51 gold badges287 silver badges398 bronze badges

Collectives™ on Stack Overflow

Regex data validation for input containing only the digits

2 Answers 2

8 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

8 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related