FILENAME='birthday_0' $(cat command_ffmpeg_SYNCAUD) cat prints out a file without altering it’s contents. If it’s important to keep the commands in a separate file, you could use sed to find/replace, or use eval, or use some external template engine (lookup “bash expand variables in file”). What you probably want to do instead, I assume, is to replace the external files with regular bash variables: filename="some-file" command="ffmpg -i ${filename}.mpg -bla -blabla ${filename}.mkv" echo "$command"