Ruby specifying regexp

Question

How would I write a regexp so that the string MUST equal the exact format in the regexp?

For example:

/\d:\d/ =~ 5:4

BUT

/\d:\d/ is also equal to 5:42alskjf2425

how do I make it so that my regexp checks for only a digit, followed by a colon, followed by a digit, and nothing else?

Thanks.

Matt · Accepted Answer · 2014-02-19 19:05:58Z

2

Use \A and \z anchors, to match the beginning and end of a string:

/\A\d:\d\z/ =~ '5:4'  # => 0   (boolean true)
/\A\d:\d\z/ =~ '5:4x' # => nil (boolean false)

answered Feb 19, 2014 at 19:05

Matt

20.8k1 gold badge61 silver badges76 bronze badges

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

1 Comment

@user3329470 - if the answer is what you're looking for you can accept it by clicking the check mark next to it.

the Tin Man · Accepted Answer · 2014-02-20 01:38:53Z

1

If you need to specify how many characters must be found, you can do it a couple ways:

In other words, use:

/\d{1}:\d{1}/

Check it out:

'5:4'[/\d{1}:\d{1}/]             # => "5:4"
'5:42alskjf2425'[/\d{1}:\d{1}/]  # => "5:4"

That's all documented so take the time to read through the Regexp documentation.

answered Feb 19, 2014 at 19:28

the Tin Man

161k44 gold badges222 silver badges308 bronze badges