A regular expression to exclude a word/string

I have a regular expression as follows:

^/[a-z0-9]+$

This matches strings such as /hello or /hello123.

However, I would like it to exclude a couple of string values such as /ignoreme and /ignoreme2.

I've tried a few variants but can't seem to get any to work!

My latest feeble attempt was

^/(((?!ignoreme)|(?!ignoreme2))[a-z0-9])+$

Any help would be gratefully appreciated :-)

1

6 Answers

Here's yet another way (using a negative look-ahead):

^/(?!ignoreme|ignoreme2|ignoremeN)([a-z0-9]+)$ 

Note: There's only one capturing expression: ([a-z0-9]+).

4

This should do it:

^/\b([a-z0-9]+)\b(?<!ignoreme|ignoreme2|ignoreme3)

You can add as much ignored words as you like, here is a simple PHP implementation:

$ignoredWords = array('ignoreme', 'ignoreme2', 'ignoreme...');
preg_match('~^/\b([a-z0-9]+)\b(?<!' . implode('|', array_map('preg_quote', $ignoredWords)) . ')~i', $string);

3

As you want to exclude both words, you need a conjuction:

^/(?!ignoreme$)(?!ignoreme2$)[a-z0-9]+$

Now both conditions must be true (neither ignoreme nor ignoreme2 is allowed) to have a match.

2

This excludes all rows containing ignoreme from search results. It will also work pretty well when there are any character in a row

^((?!ignoreme).)*$

This worked for me:^((?!\ignoreme1\b)(?!\ignoreme2\b)(?!\ignoreme3\b).)*$

simpler:

re.findall(r'/(?!ignoreme)(\w+)', "/hello /ignoreme and /ignoreme2 /ignoreme2M.")

you will get:

['hello']