Ytdyklly

With Bash and Dash, you can check for an empty directory using just the shell
(ignore dotfiles to keep things simple):

set *

if [ -e "$1" ]

then

  echo 'not empty'

else

  echo 'empty'

fi

However I recently learned that Zsh fails spectacularly in this case:

% set *

zsh: no matches found: *



% echo "$? $#"

1 0

So not only does the set command fail, but it doesn't even set $@. I suppose
I could test if $# is 0, but it appears that Zsh even stops execution:

% { set *; echo 2; }

zsh: no matches found: *

Compare with Bash and Dash:

$ { set *; echo 2; }

2

Can this be done in a way that works in bash, dash and zsh?

While zsh's default behaviour is to give an error, this is controlled by the nomatch option. You can unset the option to leave the * in place the way that bash and dash do:

setopt -o nonomatch

While that command won't work in either of the others, you can just ignore that:

setopt -o nonomatch 2>/dev/null || true ; set *

This runs setopt on zsh, and suppresses the error output (2>/dev/null) and return code (|| true) of the failed command on the others.

As written it's problematic if there is a file, for example, -e: then you will run set -e and change the shell options to terminate whenever a command fails; there are worse outcomes if you're creative. set -- * will be safer and prevent the option changes.

Most portable way would be via set and globstar for all POSIX-compliant shells. This has been shown in Gilles's answer on a related question. I've adapted the method slightly into a function:

rm -rf empty_dir/

mkdir empty_dir/

pwd

cd empty_dir/

pwd

dir_empty(){



    # https://stackoverflow.com/a/9911082/3701431

    if [ -n "$ZSH_VERSION" ]; then

        # https://unix.stackexchange.com/a/310553/85039

        setopt +o nomatch 

    fi    



    set -- * .*

    echo "$@"

    for i; do

        [ "$i" = "." ] || [ "$i" = ".." ] && continue

        [ -e "$i" ] && echo "Not empty" && return 1

    done

    echo "Empty" && return 0

}

dir_empty

touch  '*'

dir_empty

The big problem with zsh is that while ksh and bash behave in more or less consistent manner - that is when we do set * .* you will have 3 positional parameters * . .. in really empty directory - in zsh you will get * .* as positional parameters. Luckily at least for i ; do ... done to iterate over positional parameters works consistently. The rest is just iteration and check for existence of the filename, with . and .. skipped.

Try it online in ksh!

Try it online in zsh!