# Expression to delete defined strings from tag

**URL:** https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409
**Category:** Support
**Created:** [January 17, 2014, 4:18am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409 "2014-01-17T04:18:42Z")
**Posts on this page:** 1
**Showing post:** 22

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### Author: ![chrishirst](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/c/4af34b/32.png) [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 22, 2014, 9:52pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/22 "2014-01-22T21:52:35Z")

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> [@](#):
>
> I thought about it and my take is that your explanation is not correct.

In that case.  
The MP3Tag help needs rewriting

> [@](#):
>
> Repeats
> 
> - repeated any number of times including zero
> 
> - repeated any number of times, but at least once  
> ? repeated zero or one times only  
> a{n} is the letter "a" repeated exactly n times  
> a{n,} represents the letter "a" repeated at least n times with no upper limit  
> a{n,m} represents the letter "a" repeated between n and m times  
> Non-greedy repeats
> 
> Non-greedy repeats are possible by appending a '?' after the repeat; a non-greedy repeat is one which will match the shortest possible string.

The document at regular-expression.info linked in earlier post.

The technical spec for a Perl regex

> [@](#):
>
> \*? Match 0 or more times, not greedily
> 
> ```
> +? Match 1 or more times, not greedily
> ?? Match 0 or 1 time, not greedily
> {n}? Match exactly n times, not greedily (redundant)
> {n,}? Match at least n times, not greedily
> {n,m}? Match at least n but not more than m times, not greedily
> 
> ```

AND The POSIX specifications for the 'Boost' regex library.  
[http://www.boost.org/doc/libs/1\_55\_0/libs/...ic\_syntax.emacs](http://www.boost.org/doc/libs/1_55_0/libs/regex/doc/html/boost_regex/syntax/basic_syntax.html#boost_regex.syntax.basic_syntax.emacs)

..... .....

But I'll take your word for the appended '?' not setting a non-greedy repeat when following a group or an atomic repeat.

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