Diff for "BashFAQ/004"

Anchor(faq4)

How can I check whether a directory is empty or not?

• I just deleted three completely wrong answers from this question. Please, people, make sure that when you add to the FAQ, your answers

  • answer the question that was asked, and

  • actually work

  Thanks. -- GreyCat

Most modern systems have an "ls -A" which explicitly omits "." and ".." from the directory listing:

    if [ -n "$(ls -A somedir)" ]
    then
        echo directory is non-empty
    fi

This can be shortened to:

    if [ "$(ls -A somedir)" ]
    then
        echo directory is non-empty
    fi

Another way, using Bash features, involves setting a special shell option which changes the behavior of [:glob:globbing]. Some people prefer to avoid this approach, because it's so drastically different and could severely alter the behavior of scripts.

Nevertheless, if you're willing to use this approach, it does greatly simplify this particular task:

    shopt -s nullglob
    if [[ -z $(echo *) ]]; then
        echo directory is empty
    fi
    shopt -u nullglob

This can also be combined with Bash's [:BashFAQ/005:arrays]. The major advantage here is that you probably wanted to do something with all the files, so having them loaded into an array is something that will help you with the overall task:

    shopt -s nullglob
    files=(*)
    (( ${#files[*]} )) || echo directory is empty
    shopt -u nullglob 

nullglob also simplifies various other operations:

    shopt -s nullglob
    for i in *.zip; do
        blah blah "$i"  # No need to check $i is a file.
    done
    shopt -u nullglob

Without the nullglob, that would have to be:

    for i in *.zip; do
        [[ -f $i ]] || continue  # If no .zip files, i becomes *.zip
        blah blah "$i"
    done

(You may want to use the latter anyway, if there's a possibility that the glob may match directories in addition to files.)

Finally, you may wish to avoid the direct question altogether. Usually people want to know whether a directory is empty... because they want to do something involving the files therein, etc. Look to the larger question. For example, something like this may be an appropriate solution:

   find "$somedir" -type f -exec echo Found unexpected file {} \;

It's all a matter of addressing the program's actual requirements.