bash中的for循环通过具有两个特定扩展名的文件 [英] for loop in bash go though files with two specific extensions

问题描述

我希望以下循环遍历m4a文件和webm文件.目前，我使用了两个不同的循环，另一个循环只是替换了该循环中的所有m4a. ffmpeg输出的文件也应该删除m4a扩展名(如果它是m4a文件)和webm扩展名(如果它是webm文件).并将其替换为mp3. (与m4a一样).我不知道该怎么做，我认为它与正则表达式有关，但是我不知道如何真正使用它们，也没有找到一个好的教程/文档，所以如果您有的话，也请链接它

for i in *.m4a ; do
        echo "Converting file $converted / $numfiles : $i"
        ffmpeg -hide_banner -loglevel fatal -i "$i" "./mp3/${i/.m4a}.mp3"
        mv "$i" ./done
        converted=$((converted + 1))
done

解决方案

尝试以下操作:

for i in *.m4a *.webm; do
  echo "Converting file $converted / $numfiles : $i"
  ffmpeg -hide_banner -loglevel fatal -i "$i" "./mp3/${i%.*}.mp3"
  mv "$i" ./done
  converted=$((converted + 1))
done

• 您可以将for与多个模式(全局)一起使用，如此处所示:*.m4a *.webm将扩展为for进行迭代的单个令牌列表.

  • 您可能希望在循环前添加shopt -s nullglob，以便在没有匹配文件的情况下，不使用未展开模式输入它.

• ${i%.*}.mp3使用参数扩展-具体来说，%用于最短后缀删除-从文件名中删除所有现有扩展名，然后附加.mp3.

请注意，以上技术使用的是模式，而不是正则表达式.虽然关系密切，但存在根本差异；模式更简单，但局限性更大；参见模式匹配.

^{PS:您可以将converted=$((converted + 1))简化为(( ++converted )).}

I want the following loop to go through m4a files AND webm files. At the moment I use two diffrent loops, the other one just replaces all the m4a from this loop. Also the files that ffmpeg outputs should remove a m4a extension if it was a m4a file, and a webm extension if it was a webm file. And replace that with mp3. (As it does here with m4a). I have no Idea how to do it, I think it has something to do with regex expressions, but I have no idea how really use them nor have I ever found a good tutorial/documentation, so if you have one, please link it aswell.

for i in *.m4a ; do
        echo "Converting file $converted / $numfiles : $i"
        ffmpeg -hide_banner -loglevel fatal -i "$i" "./mp3/${i/.m4a}.mp3"
        mv "$i" ./done
        converted=$((converted + 1))
done

解决方案

Try the following:

for i in *.m4a *.webm; do
  echo "Converting file $converted / $numfiles : $i"
  ffmpeg -hide_banner -loglevel fatal -i "$i" "./mp3/${i%.*}.mp3"
  mv "$i" ./done
  converted=$((converted + 1))
done

• You can use for with multiple patterns (globs), as demonstrated here: *.m4a *.webm will expand to a single list of tokens that for iterates over.

  • You may want to add shopt -s nullglob before the loop so that it isn't entered with the unexpanded patterns in the event that there are no matching files.

• ${i%.*}.mp3 uses parameter expansion - specifically, % for shortest-suffix removal - to strip any existing extension from the filename, and then appends .mp3.

Note that the techniques above use patterns, not regular expressions. While distantly related, there are fundamental differences; patterns are simpler, but much more limited; see pattern matching.

^{P.S.: You can simplify converted=$((converted + 1)) to (( ++converted )).}

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