As part of a Hazel rule to process downloaded mp3 files, I worked out a couple different methods for extracting the ID3 title tag. Not rocket science, but it took a little time to sort out. Both rely on non-standard third-party tools, both for parsing the text and for extracting the ID3 tags.

Extracting ID3 title with ffprobe

ffprobe is part of the ffmpeg suite of tools which on macOS can be installed with Homebrew. If you don’t have the latter, go install it now; because it opens up so many tools for your use. In this case, it makes ffmpeg available via brew install ffmpeg.

With that in place, extracting the title is just:

title=$(ffprobe -loglevel error -show_entries format_tags=title -of 
   default=noprint_wrappers=1:nokey=1 $file)

Extracting ID3 title with id3info

id3info is part of the id3tool suite of tools installed using - you guessed it - Homebrew. This solution also uses sd (brew install sd.) The latter is a more intuitive search and displace tool than the old stand-by sed.

IFS=$'\r\n'
tit2=""
for ln in $( id3info $file ); do
    if echo $ln | grep -q "TIT2"
    then
        tit2=$( echo $ln | sd '.*TIT2.*: (.*).*' '$1' );
        break;
    fi
done

Or a one-liner using perl:

echo $( id3info $file ) | perl -ne 'print $1 if /TIT2.*?\:\s+(.*?)\s===/;'

References

• sd - intuitive search and displace - a sed replacement
• ffmpeg - play, record, convert, and stream audio and video
• id3tool - ID3 editing tool
• Bash for loop - a short tutorial on the Bash for loop - something that I wasn’t really proficient at. Always good to revist.