How to proberly deal with quotes in filenames when using variables/arrays including the filenames in bash?

Question

I have been working on a bash script for a few days and got stuck with filenames including single and double quotes. Give I want to iterate over the following files in a directory:

'file1.txt'
'file2.txt'
"file3.txt"
file"3.txt
file'4.txt
very 'bad file.txt
also "very bad.txt

I know that this is bad filenaming – but you know, not all people are programmers and know how to proberly name files. So I try to cope with this edge cases.

I would like to loop through the files and use them in some if statements like this for example:

dir="my/dir/"
files="$(ls -N "$dir"*)"
shopt -s extglob
for f in $files; do
  if [[ "$files" =  "(.png|.jpg|.jpeg|.JPG|.JPEG|*.webp)" ]]; then
    for $e in "$files"; do
      cp "$e" "$dir""somefilename.pdf"
    else
      cp "$f" "$dir""somefilename.pdf"
  fi
done

Now the problem arises, that bash is intepreting the double and single quotes in the filenames and splitting up the files – errors follow…

So my question is: How to cope with these cases in bash?

Answer 1

Don't parse the output of ls. That way lies madness and all sorts of strife. If you are trying to do things to or with all files in a given directory, let the shell take care of the filenames for you:

workdir="/path/to/directory"
for file in "${workdir}"/*; do
    case "$file" in
        *.png|*.jpg|*.jpeg|*.JPG|*.JPEG|*.webp)
            cp -- "$file" "$dir"/"somefilename.pdf"
            ;;
    esac
done

Note that I have taken the predicate directly from your question, which has the dubious logic of repeatedly overwriting somefile.pdf with each matching file, which is probably not what you want. Addressing that is beyond the scope of the question of iterating over files, the short(er) answer for which is to simply use for file in path/to/place/*; do stuff_to "$file"; done.