Bash best practices

# https://vaneyckt.io/posts/safer_bash_scripts_with_set_euxo_pipefail/
set -Eeuxo pipefail

Best practices from Google:

# --- Process file line-by-line (don't pipe to 'while', use process substitution)
last_line='NULL'
while read line; do
  if [[ -n "${line}" ]]; then
    last_line="${line}"
  fi
done < <(your_command)
# This will output the last non-empty line from your_command
echo "${last_line}"

## ... OR ...

last_line='NULL'
readarray -t lines < <(your_command)
for line in "${lines[@]}"; do
  if [[ -n "${line}" ]]; then
    last_line="${line}"
  fi
done
echo "${last_line}"
# This will output the last non-empty line from your_command
echo "${last_line}"

# --- Testing strings
# Do this:
if [[ "${my_var}" == "some_string" ]]; then
  do_something
fi

# -z (string length is zero) and -n (string length is not zero) are
# preferred over testing for an empty string
if [[ -z "${my_var}" ]]; then
  do_something
fi

# This is OK (ensure quotes on the empty side), but not preferred:
if [[ "${my_var}" == "" ]]; then
  do_something
fi

# --- Arrays

# An array is assigned using parentheses, and can be appended to
# with +=( … ).
declare -a flags
flags=(--foo --bar='baz')
flags+=(--greeting="Hello ${name}")
mybinary "${flags[@]}"

# --- Check return status
if ! mv "${file_list[@]}" "${dest_dir}/"; then
  echo "Unable to move ${file_list[*]} to ${dest_dir}" >&2
  exit 1
fi

## ... or ...

mv "${file_list[@]}" "${dest_dir}/"
if (( $? != 0 )); then
  echo "Unable to move ${file_list[*]} to ${dest_dir}" >&2
  exit 1
fi