# 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:** 20
**Page:** 1
### Author:  [@lolspops](https://community.mp3tag.de/u/lolspops)
#### Post date: [January 17, 2014, 4:18am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/1 "2014-01-17T04:18:42Z")
Hello,
I am trying to delete certain strings from my tag using expressions. First, I have tracks that are like "03/10" or "01/07" and I just want it to be "3/10" and "1/7". However, if I search specifically for "0" to replace as nothing, things like "03/10" will be "3/1" which would not work. Is there a better way say, to only delete leading zeroes?
Secondly, I have Album titles as _xxx_ [_xxx_] but I want to delete everything in and including the square brackets.
---
### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [January 17, 2014, 5:17am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/2 "2014-01-17T05:17:32Z")
At least 2 solutions:
1: use the numbering wizard and renumber your files.
2: Create an action of the type "Replace with regular expression" for TRACK
Enter as search string: ^0
Leave format string empty.
Second case, same type of action. Only this time other field and enter as search string:
' ['.\*']'
again: leave the search string empty
---
### Author:  [@lolspops](https://community.mp3tag.de/u/lolspops)
#### Post date: [January 17, 2014, 7:49am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/3 "2014-01-17T07:49:37Z")
> [@ohrenkino](#):
>
> At least 2 solutions:
> 1: use the numbering wizard and renumber your files.
> 2: Create an action of the type "Replace with regular expression" for TRACK
> Enter as search string: ^0
> Leave format string empty.
>
> Second case, same type of action. Only this time other field and enter as search string:
> ' ['.\*']'
> again: leave the search string empty
Thank you, but is it possible for the second solution to modify the total tracks too because only the current track works eg. 1/07. Also, the search string input for the square brackets one don't work.
---
### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [January 17, 2014, 9:52am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/4 "2014-01-17T09:52:15Z")
> [@lolspops](#):
>
> Thank you, but is it possible for the second solution to modify the total tracks too because only the current track works eg. 1/07. Also, the search string input for the square brackets one don't work.
Try
' [.\*]'
(fewer apostrophes, added )
For the track number stuff:
add an action of the type simple "Replace" to the already created action (Select the action group, klick Edit, klick New)
enter as search string:
/0
enter as replace string:
/
---
### Author:  [@lolspops](https://community.mp3tag.de/u/lolspops)
#### Post date: [January 17, 2014, 10:02am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/5 "2014-01-17T10:02:34Z")
> [@ohrenkino](#):
>
> Try
> ' [.\*]'
> (fewer apostrophes, added )
Still does not work
---
### Author:  [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 17, 2014, 12:29pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/6 "2014-01-17T12:29:57Z")
Patterns to remove leading zeros from the track field are:
Multiple
```
$regexp(%track%,^0+,$1)
```
single
```
$regexp(%track%,^0,$1)
```
Though removing leading zeros will 'break' sorting in Windows Explorer and media player applications, so fracks will become ordered as
1
10
11
.
.
19
2
20
21
...
and so on.
---
### Author:  [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 17, 2014, 1:08pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/7 "2014-01-17T13:08:17Z")
to remove the leading zero after the '/' will need an action group creating with running this replace first
```
$replace(%track%,/0,/)
```
then the regexp in the post above.
Never tried in MP3Tag but I don't think nested regular expressions are going to be possible.
---
### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [January 17, 2014, 5:47pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/8 "2014-01-17T17:47:47Z")
> [@lolspops](#):
>
> Still does not work
Sorry, i was puzzled and made it far too complicated.
[.\*]
will do it
---
### Author:  [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 17, 2014, 6:49pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/9 "2014-01-17T18:49:00Z")
> [@ohrenkino](#):
>
> Sorry, i was puzzled and made it far too complicated.
> [.\*]
> will do it
?????
That would just leave \ in the track field
A regex match pattern of .\* means "match any character (except newline [ASCII 13] ) 1 or more times"
---
### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [January 17, 2014, 7:20pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/10 "2014-01-17T19:20:16Z")
> [@Chris Hirst](#):
>
> ?????
You are probably right - I was refering to the second problem with the square brackets part and not the track number problem.
---
### Author:  [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 17, 2014, 8:46pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/12 "2014-01-17T20:46:33Z")
> [@ohrenkino](#):
>
> I was refering to the second problem with the square brackets part and not the track number problem.
Doesn't a regexp to empty a field though
You can
Ctrl+A (select all)
select in the tag panel then Ctrl+S to save
Or for scripting/Convert (Alt+5)
Set the field and an action of $replace(%field%,)
---
### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [January 17, 2014, 8:56pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/13 "2014-01-17T20:56:22Z")
> [@Chris Hirst](#):
>
> Doesn't a regexp to empty a field though
>
> You can
> Ctrl+A (select all)
> select in the tag panel then Ctrl+S to save
>
> Or for scripting/Convert (Alt+5)
>
> Set the field and an action of $replace(%field%,)
Are you discussing this theoretically or have you tried it?
The op's request was to delete a text in square brackets, but leave the rest.
And this is exactly what the [.\*] will do.
It will take that part of the string that has a square bracket at the beginning, something in between and a square bracket at the end and replace it with nothing. The rest of the field will remain unaltered.
---
### Author:  [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 17, 2014, 9:26pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/15 "2014-01-17T21:26:26Z")
> [@ohrenkino](#):
>
> Are you discussing this theoretically or have you tried it?
> The op's request was to delete a text in square brackets, but leave the rest.
> And this is exactly what the [.\*] will do.
> It will take that part of the string that has a square bracket at the beginning, something in between and a square bracket at the end and replace it with nothing. The rest of the field will remain unaltered.
Apologies I had misread the post.
---
### Author:  [@lolspops](https://community.mp3tag.de/u/lolspops)
#### Post date: [January 17, 2014, 11:07pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/16 "2014-01-17T23:07:03Z")
Thank you all for the help. One final request:
I have fields with repeated strings eg. 'DATE' = '2014-01-17 2014-01-17 2014-01-17' and looking through my tagging script it seems this is creating the duplicate strings:
> [@](#):
>
> regexpreplace "(releaseDate":")(\d\d\d\d)-(\d\d)-(\d\d)" "$1$2-$3-$4"
>
> ```
> outputto "RELEASE DATE"
> sayregexp "(?<=releaseDate\":\")[^\"]+"
>
> ```
Is there a way I can fix this or an action group to fix it afterwards?
---
### Author:  [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 18, 2014, 12:13am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/17 "2014-01-18T00:13:53Z")
Regular expressions are 'greedy' by nature, meaning they will match as much as possible,
If you add a ? after the repeat, it makes the match 'non-greedy' so it matches the shortest possible string
and instead of \d\d\d\d use a repeating set, so a 'non-greedy four digit pattern is;
```
\d{4}?
```
---
### Author:  [@lolspops](https://community.mp3tag.de/u/lolspops)
#### Post date: [January 18, 2014, 1:35am UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/18 "2014-01-18T01:35:47Z")
Thank you, it works perfectly
---
### Author:  [@dano](https://community.mp3tag.de/u/dano)
#### Post date: [January 18, 2014, 4:30pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/19 "2014-01-18T16:30:59Z")
\d{4}? The question mark there makes no sense to me, what's the difference from \d{4}
---
### Author:  [@chrishirst](https://community.mp3tag.de/u/chrishirst)
#### Post date: [January 18, 2014, 6:41pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/20 "2014-01-18T18:41:08Z")
The ? makes the match "non-greedy"
\d{4} would match any and all four digit sequences in the same string, adding the ? AFTER the repeat means it will only match the shortest possible sequence.
so $regexp(' 1234 1234 1234',\d{4} $1) will return the entire string without the spaces ie; '123412341234' (greedy), whereas $regexp(' 1234 1234 1234',\d{4}?, $1) will only return the first sequence of '1234' which is the shortest possible match from that string, so is a 'non-greedy' or a 'lazy' match.
More on "laziness' vs 'greediness' in Regular Expressions
[http://www.regular-expressions.info/repeat.html](http://www.regular-expressions.info/repeat.html)
---
### Author:  [@dano](https://community.mp3tag.de/u/dano)
#### Post date: [January 22, 2014, 6:59pm UTC](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409/21 "2014-01-22T18:59:34Z")
I thought about it and my take is that your explanation is not correct.
The ? on \d{4}? has no effect. {4} if a fixed repetition.
It only works with i.e. \d{4,6}? or \d{4,}?
You're mixing up greediness with global matching which means how often a complete pattern is matched in a string (either just one time or as often as possible). This is activated in Mp3tag (match as often as possible) and cannot be changed afaik.
Example:
$regexp(aaa,a{1},) =\> empty
$regexp(aaa,a{1}?,) =\> empty
If global matching was off (match only one time) the result would be _aa_
---
### Author:  [@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")
> [@](#):
>
> 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.
[Next page](https://community.mp3tag.de/t/expression-to-delete-defined-strings-from-tag/15409.md?page=2)