count_empty.bash

#!/usr/bin/env bash

output_file="${HOME}/found_empty.txt"

# For user convenience. If the user runs this using `sudo`,
# the file shall be within their own home directory, instead
# of the root's.
#
# We shall also create the file and make its ownership make sense
# for the user.
if [ -n "${SUDO_USER}" ]; then
    user_home=$(eval echo ~"${SUDO_USER}")
    output_file=$(printf "%s/found_empty.txt" "${user_home}")

    # Create file if it doesn't exist already.
    # No need to remove it if it already exists because
    # we'd write over the contents anyhow.
    [ ! -f "${output_file}" ] && touch "${output_file}"

    # Little bit of non-standard stuff for this.
    # We will set the owner of the resulting file to be
    # the same as the home directory so they can read and
    # such.
    #
    # For this being an example to be probably run on a regular
    # Linux system using GNU Coreutils this isn't an issue,
    # but for anyone trying to adapt this sample for something
    # more portable, this is worth mentioning!
    chown --reference="${user_home}" "${output_file}"
fi

# Main body of the program. We just go through
# the output of `find` line-by-line, with each line
# being stored in `${file}`, getting their sizes
# with `wc -c` which counts the bytes in a file.
#
# If the size is zero, it gets printed and thus redirected
# to the output file.
find /etc -type f | while read file; do
    size=$(wc -c ${file} | cut -d' ' -f1)
    [ "${size}" -eq 0 ] && printf "%s\n" "${file}"
done > "${output_file}"