ubuntu - Why doesn't this for loop work?

This is on Ubuntu 12.04 I'm trying to figure out how to get ffmpeg to do a batch conversion of FLACs to MP3, recursively. If I cd into a directory and use

for f in *.flac; do ffmpeg -i "$f" -c:a libmp3lame -q:a 2 "${f/%flac/mp3}"; done

that works perfectly fine. However, when I try this, it doesn't work:

for f in "$(find . -type f -name *.flac)"; do ffmpeg -i "$f" -c:a libmp3lame -q:a 2 "${f/%flac/mp3}"; done

It doesn't even throw up any useful errors (but here is the output anyway, no need to complain):

evilsoup@enchantment:~/Music/Jean Sibelius$ for f in "$(find . -type f -name *.flac)"; do ffmpeg -i "$f" -c:a libmp3lame -q:a 2 "${f/%flac/mp3}"; done
ffmpeg version git-2012-12-18-b7e085a Copyright (c) 2000-2012 the FFmpeg developers
  built on Dec 18 2012 19:23:11 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --enable-gpl --enable-libfaac --enable-libfdk-aac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-librtmp --enable-libtheora --enable-libvorbis --enable-libvpx --enable-x11grab --enable-libx264 --enable-nonfree --enable-version3
  libavutil      52. 12.100 / 52. 12.100
  libavcodec     54. 80.100 / 54. 80.100
  libavformat    54. 49.102 / 54. 49.102
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 28.100 /  3. 28.100
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/02. Symphony No.1.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/03. Symphony No.1.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/stripped2.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/05. Symphony No.1.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/stripped3.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/09. Andante festivo.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/08. Symphony No.3.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/01. Finlandia.flac
./Symphonies 1, 2, 3 & 5 (Oslo Philharmonic Orchestra Conducted by Mariss Jansons) Disc 1/07. Symphony No.3.flac
./Symphonies 1, 2, 3 & 5

I've tested the find command on its own, and it works as expected, so the problem has to be something to do with the interaction between find and for.

I'm aware that I could do something with find's -exec option, but I can't find any way to do string substitution as I can with a bash for loop, and I'd rather not have a bunch of file.flac.mp3s to deal with, even if they could be fixed with a simple rename.

Answer

The double quotes around the $(find ...) command make for see find's output as one single filename, which obviously is not what you want.

There are several ways to achieve what you want:

• 
  

  Make find execute ffmpeg directly (no piping, no loops):

  
  

  find . -type f -name *.flac -exec bash -c '
     ffmpeg -i "$0" -c:a libmp3lame -q:a 2 "${0/%flac/mp3}"
  ' {} \;
  



• 
  

  Use find ... -print0 | xargs -0 ... instead of for, which is specifically made for these purposes:

  
  

  find . -type f -name *.flac -print0 | xargs -0 -I {} bash -c '
      ffmpeg -i "$0" -c:a libmp3lame -q:a 2 "${0/%flac/mp3}"
  ' {}
  



• 
  

  Change IFS to newline only, the use the same command as before, minus the double quotes:

  
  

  IFS=$'\n'
  for f in $(find . -type f -name *.flac); do
      ffmpeg -i "$f" -c:a libmp3lame -q:a 2 "${f/%flac/mp3}"
  done
  unset IFS
  

  
  

  The command unset IFS changes the IFS back to it's default value (not needed inside a shell script, unless it interferes with subsequent commands).