Check if directory contains only hidden files and no directories

Question

I'm trying to put a third check whether the directory contains only hidden files:

if [ ! "$(ls -A "$dir")" ]; then
  echo "Specified directory is empty"
  exit 1
elif [[ -z "$(find "$dir" -maxdepth 1 -type f)" ]]; then
  echo "Specified directory contains only subdirectories and no files"
  exit 1
elif [[ -z "$(find "$dir" -maxdepth 1 -type f | grep -v '"$dir"/.*')" ]]; then
  echo "Specified directory contains only hidden files"
  exit 1
fi

The third check is what is not working. I tried getting a list of all files that don't match '.*' and checking if it's empty with -z, but it always tests true. Do you have an idea?

See: [Difference between single and double quotes in bash](http://stackoverflow.com/q/6697753/3776858) — Cyrus, Oct 22 '20 at 11:12
`grep -v '"$dir"/.*'` - do `'!' -name '.*'`. `if directory contains only hidden files and no directories` if a directory has only files, it has no directories. — KamilCuk, Oct 22 '20 at 11:17

score 1 · Accepted Answer · answered Oct 22 '20 at 11:29

Generally don't use ls in scripts.

Assuming you have the default values for nullglob etc,

files=(./*)
if [[ "${files[@]}" = './*' ]]; then
  echo "Specified directory is empty" >&2
  exit 1
fi
dirs=(./*/)
if [[ "${#dirs[@]}" = "${#files[@]}" ]]; then
  echo "Specified directory contains only subdirectories and no files" >&2
  exit 1
fi
hidden=(./.*)
if [[ "${#hidden[@]}" = "${#files[@]}" ]]; then
  echo "Specified directory contains only hidden files" >&2
  exit 1
fi

There is an obvious race condition here, in that another process could add a new hidden file after files gets assigned, but before hidden gets assigned, for example.

The use of arrays makes this Bash-only; this should be obvious, but many beginners are confused about the difference between sh and bash.

The immediate error in your attempt is that '"$dir"/.*' is in single quotes, and so gets interpreted verbatim (and even if you fixed the quoting, . in a regex matches any character, not a literal dot). But more broadly, it seems excessive to use find when the shell itself can tell you what files you have.

Thank you! Yes, the problem was the regex (and the qotes) indeed. I solved it like this: [[ -z "$(find "$dir" -maxdepth 1 -type f | grep -v ""$dir"/\..*")" ]] I guess it's overkill, so I'll probably try your solution. What does >&2 do if I can ask? — shin, Oct 22 '20 at 11:52
Diagnostic messages should be displayed on standard error, not standard output. It makes less of a difference here, but it's good practice. — tripleee, Oct 22 '20 at 11:57

Check if directory contains only hidden files and no directories

1 Answers1