What is the regular expression to allow uppercase/lowercase (alphabetical characters), periods, spaces and dashes only?

Question

I am having problems creating a regex validator that checks to make sure the input has uppercase or lowercase alphabetical characters, spaces, periods, underscores, and dash

Answer 1

The regex you're looking for is ^[A-Za-z.\s_-]+$

• ^ asserts that the regular expression must match at the beginning of the subject
• [] is a character class - any character that matches inside this expression is allowed
• A-Z allows a range of uppercase characters
• a-z allows a range of lowercase characters
• . matches a period rather than a range of characters
• \s matches whitespace (spaces and tabs)
• _ matches an underscore
• - matches a dash (hyphen); we have it as the last character in the character class so it doesn't get interpreted as being part of a character range. We could also escape it (\-) instead and put it anywhere in the character class, but that's less clear
• + asserts that the preceding expression (in our case, the character class) must match one or more times
• $ Finally, this asserts that we're now at the end of the subject

When you're testing regular expressions, you'll likely find a tool like regexpal helpful. This allows you to see your regular expression match (or fail to match) your sample data in real time as you write it.

Answer 2

Check out the basics of regular expressions in a tutorial. All it requires is two anchors and a repeated character class:

^[a-zA-Z ._-]*$

If you use the case-insensitive modifier, you can shorten this to

^[a-z ._-]*$

Note that the space is significant (it is just a character like any other).