how to filter certain files with a particular content

thanks a lot for the suggestion. it works.

so we have made a count of characters of each records.

Now I want to get all the records' TITILE with 30 characters.a regexp to del all the characters in the title over 30

Is it possible to ask mp3tag to get all the records' title with 30 characters?

Action "Format value"
Field: TITLE
Formatstring: $left(%TITLE%,30)
... or if you also want to trim possible trailing white space ...
Formatstring: $trimRight($left(%TITLE%,30))

DD.20151110.1820.CET

thanks a lot for the suggestion. it works.