A solution to convert .flac files to .mp3 files from the command line:

  • install lame and flac;
  • move the .flac files into one directory;
  • from that directory, run the following bash script:
for file in *.flac;
  do $(flac -cd "$file" | lame -h - "${file%.flac}.mp3");
done

On Mac OS X, the most convenient options to install lame and flac are: