I need to match these characters. This quote is from an API documentation (external to our pany):

Valid characters: 0-9 A-Z a-z & # - . , ( ) / : ; ' @ "

I used this Regex to match characters:

^[0-9a-z&#-\.,()/:;'""@]*$

However, this wrongly matches characters like %, $, and many other characters. What's wrong?

You can test this regular expression online using /, and this regular expression is meant to work in both .NET and JavaScript.

I need to match these characters. This quote is from an API documentation (external to our pany):

Valid characters: 0-9 A-Z a-z & # - . , ( ) / : ; ' @ "

I used this Regex to match characters:

^[0-9a-z&#-\.,()/:;'""@]*$

However, this wrongly matches characters like %, $, and many other characters. What's wrong?

You can test this regular expression online using http://regexhero/tester/, and this regular expression is meant to work in both .NET and JavaScript.

• javascript
• regex

• dont suppose escaping the extra hyphen in there (or moving it to the beginning or end) would change anything. – machinaut Commented Oct 8, 2011 at 13:42

5 Answers 5

You are not escaping the dash -, which is a reserved character. If you add replace the dash with \- then the regex no longer matches those characters between # and \

Move the literal - to the front of the character set:

^[-0-9a-z&#\.,()/:;'""@]*$

otherwise it is taken as specifying a range like when you use it in 0-9.

- sign, when not escaped, has special meaning in square brackets. #-\. is transformed into #-. (BTW, backslash before dot is not necessary in square brackets), which means "any character between # (ASCII 0x23) and . (ASCII 0x2E). The correct notation is

^[0-9a-z&#\-.,()/:;'"@]*$

The special characters in a character class are the closing bracket (]), the backslash (\), the caret (^) and the hyphen (-).

As such, you should either escape them with a backslash (\), or put them in a position where there is no ambiguity and they do not need escaping. In the case of a hyphen, this would be the first or last position.

You also do not need to escape the dot (.).

Your regex thus bees:

^[-0-9a-z&#.,()/:;'"@]*$

Typing your original regex in it and hovering over the hyphen shows:
Matches characters in the range '#-\'

Try that

^[0-9a-zA-Z\&\#\-\.\,\(\)\/\:\;\'\"\@]*$