CODEWITHSUNDEEP
bashffmpeg
EarthIsHome
EarthIsHome

Reputation: 735

Bash script to convert music from one directory into another

I've modified this script from the arch forums: https://wiki.archlinux.org/index.php/Convert_Flac_to_Mp3#With_FFmpeg

I'm trying to find specific file types in a directory structure, convert them to another music file type, and place them in a "converted" directory that maintains the same directory structure.

I'm stuck at stripping the string $b of its file name.

$b holds the string ./converted/alt-j/2012\ an\ awesome\ wave/01\ Intro.flac

Is there a way I can remove the file name from the string? I don't think ffmpeg can create/force parent directories of output files.

#!/bin/bash
# file convert script
find -type f -name "*.flac" -print0 | while read -d $'\0' a; do
    b=${a/.\//.\/converted/}
    < /dev/null ffmpeg -i "$a" "${b[@]/%flac/ogg}"
    #echo "${b[@]/%flac/ogg}"

Upvotes: 1

Views: 261

Answers (1)

John1024
John1024

Reputation: 113834

I'm stuck at stripping the string $b of its file name.

Let us start with b:

$ b=./converted/alt-j/2012\ an\ awesome\ wave/01\ Intro.flac

To remove the file name, leaving the path:

$ c=${b%/*}

To verify the result:

$ echo "$c"
./converted/alt-j/2012 an awesome wave

To make sure that directory c exists, do:

$ mkdir -p "$c"

Or, all in one step:

$ mkdir -p "${b%/*}"

How it works

We are using the shell's suffix removal feature. In the form ${parameter%word}, the shell finds the shortest match of word against the end of parameter and removes it. (Note that word is a shell glob, not a regex.) In out case, word is /* which matches a slash followed by any characters. Because this removes the shortest such match, this removes only the filename part from the parameter.

Suffix Removal Detailed Documentation

From man bash:

${parameter%word}
${parameter%%word}
Remove matching suffix pattern. The word is expanded to produce a pattern just as in pathname expansion. If the pattern matches a trailing portion of the expanded value of parameter, then the result of the expansion is the expanded value of parameter with the shortest matching pattern (the %'' case) or the longest matching pattern (the%%'' case) deleted. If parameter is @ or *, the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list.

Upvotes: 2

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