Script to rename the title tag of mp3 Audiobook

Hello, I wrote this script to rename the title tag of mp3 chapter files of an audiobook. File names are like 01 La regola dell’equilibrio_Uno.mp3, 39 La regola dell’equilibrio_Trentuno.mp3. With this script, I want to assign the title “0$i_$title_mp3.mp3” to files 1-9 and the title “$i_$title_mp3.mp3” for double-digit files (10, 11, 12…). The problem is with the id3v2 command which, even though the “$title_mp3” variable is correct, during the execution of the script I get: “Couldn’t stat file ‘01\ La\ regola\ dell’equilibrio_Uno.mp3’”. Anyone know how to fix this? Using Linux OS.

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I have a few folders containing mp3 files (folder names CD#1 CD#2) with a few files in each folder. I renamed the Album name and changed the track number so my ipod should store it as one long Audiobook. But the title name is messed up, I want to rename the title so that it should display Track 1, Track 2 etc. I tried using mp3tag but was unsuccessful creating a dynamic title name (i.e that each file should have the next number Track 1, Track 2). Any way that I can do it.