regexp: match everything exept a single word

Question

I don't get how to create a regular expression that matches everything, except a fixed, single word. Can somebody help me?

Background: alias map for mailserver which redirects all mail to one user. /.*/ -> user1 produces a redirection loop, so i need to exclude user1 from the regexp.

Edit:

The regex should match everything, EXCEPT the single word user1. It should also match input that contains that word, i.e., user11.

i.e.: /.*/ without user1

Edit2:

POSIX Basic Regular Expressions

Can you give us some sample input text, and then describe what the expected output is? Also, what regex tool/language are you using? — Tim Biegeleisen, Sep 01 '18 at 15:29
As Tim Biegeleisen said, what Tool/programming language are you using? There's a lot of different RegEx out there. — Poul Bak, Sep 01 '18 at 16:46

41686d6564 stands w. Palestine · Answer 1 · 2018-09-01T17:17:07.950

0

If you're okay with getting your value from the first group, you can use something like this:

(?:\buser1\b)?(.+?)(?:\buser1\b|$)

Demo.

This will match anything before or after the word user1 or everything if it doesn't exist.

edited Sep 01 '18 at 17:17

answered Sep 01 '18 at 17:03

41686d6564 stands w. Palestine

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dawg · Answer 2 · 2018-09-01T17:27:40.370

0

With grep you can invert the match:

$ echo "user2
user3
user1" | grep -v '^user1$'
user2
user3

Or, with sed you can delete the match:

$ echo "user10
user2
user1" | sed -E '/^user1$/d'
user10
user2

edited Sep 01 '18 at 17:27

answered Sep 01 '18 at 17:21

dawg

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score 0 · Answer 3 · answered Sep 01 '18 at 17:53

You can use the ^(?!user1$). for checking purpose, you can use python as:

import re
if(re.match('^(?!user1$)','user11')):
  print('user11 matched')

if(re.match('^(?!user1$)','user1')):
  print('user1 matched')

if(re.match('^(?!user1$)','AnyThingElseBeforeuser1')):
  print('AnyThingElseBeforeuser1 matched')

the output is as you desire:

user11 matched

AnyThingElseBeforeuser1 matched

regexp: match everything exept a single word

3 Answers3