Bash脚本找不到文件

Question

I am writing a simple script to iterate over all the m4a files in a folder and encode them to mp3. I want to do the encoding of the files in different threads to increase the speed of execution and take advantage of all the cores in my PC, so I am sending the tasks to background, please advice me if this is the right approach. Anyway, I am getting a No such file or direcory error for every single file that I want to encode, even though the file is there; and the funny thing is that if I copy the exact same instruction to a terminal, it will be executed correctly. Can you please help me to find out what am I doing wrong?

Thanks in advance.

#!/bin/bash

function encode {
    echo "<<<<<<<<<<< encode >>>>>>>>>>>>>>>>"
    cd "$1"
    find . -mindepth 1 -maxdepth 1 | while read f
    do
        if [ -f "${f}" ]
        then
            if [ ${f: -4} == ".m4a" ]
            then
                if [ ! -d "converted" ]
                then
                    mkdir converted
                fi
                newPath="${f%m4a}mp3"
                echo "ffmpeg -i \""$f"\" -ac 2 -b:a 320k -y \""$newPath"\" </dev/null >/dev/null &"
                ffmpeg -i \""$f"\" -ac 2 -b:a 320k -y \""$newPath"\" </dev/null >/dev/null &
            fi
        elif [ -d "${f}" ]
        then
            echo "folder $f"
            encode "$f"
        fi
    done
}


encode "$1"

Answer 1

The problem you allude to is that you are adding literal quotes to the name of the file; "$f" is sufficient to pass the value of $f as-is to the ffmpeg command. You don't need to use find to iterate over the immediate contents of a directory; just use a glob with a for loop (which also avoids the need to stop ffmpeg from reading from standard input).

More subtlely, you also need encode to restore the original working directory before it returns, so that recursive calls don't "unexpectedly" change the working directory while iterating over the current directory. pushd (instead of cd ) and popd make this simple.

encode () {
  echo "<<<<<<<<<<< encode >>>>>>>>>>>>>>>>"
  pushd "$1"
  for f in *; do
    if [ -d "$f" ]; then
      encode "$f"
    elif [[ $f = *.m4a ]]; then
      mkdir -p converted
      newPath="${f%.m4a}.mp3"
      ffmpeg -i "$f" -ac 2 -b:a 320k -y "$newPath" > /dev/null &
    fi
  done
  popd
}