Can't figure out how to make this regex pattern

Question

I need a pattern that matches any set of letters, numbers and underscore bounded by whitespace, . or :.

Answer 1

It sounds like you want something like this:

^[ .:]\w+[ .:]$

Explanation

• The ^ anchor asserts that we are at the beginning of the string
• [ .:] matches one space char, period or colon
• \w+ matches one or more letters, digits or underscore
• [ .:] matches one space char, period or colon
• The $ anchor asserts that we are at the end of the string

Potential Tweaks

• In regex terms, "white-space" does not only mean the space characters, but also tabs, carriage returns and other forms of spacing. If this is what you mean, use \s in place of the space inside [ .:]
• If you want to allow more than one space character, colon or dot, you can tweak the regex like so: ^[ .:]+\w+[ .:]+$

Answer 2

This is very simple. This should work:

([\s\d][ .:])+[\s\d]+

Basically the [\s\d] is the letters, numbers or underscores, and the [ .:] is the space, dot, or colon.