I have a little programming experience but am completely new to shell scripting.

I have several hundred mp3s which I want to split using mp3splt with the command

mp3splt -A XXX.txt XXX.mp3

I have run this command by hand in the past but now have a project where doing it by hand would be impractical due to the number of files. In my imagination it should be easy to write a script that searches a folder for all the mp3s that have a txt file of the same name and runs the above command on them.

My question just is this: Is there any obvious reason this would not work? If you (meaning: a person with experience in shell scripting) don´t see any such reason, I´d work my way through this tutorial to work out the rest. If, on the other hand, you say it is impossible, I can just stop and do it by hand.

Thanks in advance!

In case you are interested in my use case: I play irish music, which is based on short melodies played by heart. I want to learn these melodies using anki with audio files. For that, I need to have audio files with just one specific tune each.

  • DollyDuller@programming.devEnglish
    101·
    2 days ago
    find /your/mp3/directory -type f -name "*.mp3" -exec test -f "/your/mp3/directory/$(basename -s .mp3 {}).txt" \; -exec mp3splt -A "/your/mp3/directory/$(basename -s .mp3 {}).txt" {} \;

    This one liner should still work, even if your file names have spaces in them because find now looks at each individual match, not the entire output. Using a for loop with the results of find would create a lot of extra pieces of the file names because spaces separate the arguments. However, this single command is harder to read than using a for loop.

    The idea behind this one is that search operators in find evaluate to true or false. The first exec tells find to run the second exec only if the file exists. If the file doesn’t exist, it just ignores it.

    • sjohannes@programming.devEnglish
      4·
      2 days ago

      I don’t think that works, because the command substitution in "$(…).txt" runs immediately in the current shell.

      Aside from that, find -exec doesn’t use a shell to run its command, which means $(…) won’t work without an explicit sh call.

      I believe the right command in this style that will work is:

      find /my/mp3dir -type f -iname '*.mp3' -exec sh -c \
  'test -f "${0%.mp3}.txt" && mp3splt -A "${0%.mp3}.txt" "$0"' \
  '{}' ';'

      However, I would recommend the for f in *.mp3-style solution instead, as to me it’s more readable. (The Bash/Zsh recursive glob (**) syntax can be used if subdirectories are involved.)

      • DollyDuller@programming.devEnglish
        1·
        2 days ago

        You’re correct about command substitutions, the $(...) part. I had initially thought putting it inside a sh would be clearer and avoid problems with substitutions. However, $0 is the name of the shell or the script. To fix this, we can put {} inside a variable, like this: file="{}". Then, we can use the variable $file for the rest of the command.

        I also think using for loops makes the command easier to read. But dealing with files that have spaces in their names can be really frustrating when you use for loops.

    • stewie410@programming.devEnglish
      1·
      2 days ago

      Huh, I hadn’t realized you could chain -exec statements in this way; I assumed \; or {} + had to be the end of the arguments.

    • shrugs@lemmy.worldEnglish
      21·
      2 days ago

      Nice one. Doing for loops with a list of files is a common mistake. I hate the exec syntax of find though. Why the fuck do we need ; at the end

      • DollyDuller@programming.devEnglish
        2·
        2 days ago

        This helps distinguish commands that find runs from its own arguments. Imagine how find would figure out which commands it’s executing, and what their arguments are. The easiest way to do this is to use the standard end-of-command character. That way, you don’t need to create a special way to separate things. You can even put one find command inside another.