From 187222614a6c57c18cbe6b32ab817232eabbf7df Mon Sep 17 00:00:00 2001
From: William Melody <hi@williammelody.com>
Date: Tue, 23 Feb 2016 18:14:21 -0800
Subject: [PATCH] Use braces in all variable references.

Braces are only required in certain cases, but the cognitive overhead in
keeping track of which cases require braces can be reduced by simply
always using them.

Example: `${NAME}`

Retain more widely-used braces `$NAME` convention in documentation.
---
 hosts              | 256 +++++++++++++++++++++++----------------------
 test/add.bats      |  90 ++++++++--------
 test/disable.bats  | 114 ++++++++++----------
 test/disabled.bats |  40 +++----
 test/enable.bats   | 152 +++++++++++++--------------
 test/enabled.bats  |  40 +++----
 test/file.bats     |  18 ++--
 test/help.bats     |  20 ++--
 test/hosts.bats    |   6 +-
 test/list.bats     | 130 +++++++++++------------
 test/remove.bats   | 180 +++++++++++++++----------------
 test/show.bats     |  84 +++++++--------
 test/version.bats  |  30 +++---
 13 files changed, 584 insertions(+), 576 deletions(-)

diff --git a/hosts b/hosts
index 80f4c87..b98f89e 100755
--- a/hosts
+++ b/hosts
@@ -77,7 +77,7 @@ _debug() {
   then
     # Prefix debug message with "bug (U+1F41B)"
     printf "🐛  "
-    "$@"
+    "${@}"
     printf "――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――\n"
   fi
 }
@@ -90,7 +90,7 @@ _debug() {
 #
 # This is a shortcut for the _debug() function that simply echos the message.
 debug() {
-  _debug echo "$@"
+  _debug echo "${@}"
 }
 
 ###############################################################################
@@ -108,7 +108,7 @@ debug() {
 _die() {
   # Prefix die message with "cross mark (U+274C)", often displayed as a red x.
   printf "❌  "
-  "$@" 1>&2
+  "${@}" 1>&2
   exit 1
 }
 # die()
@@ -120,7 +120,7 @@ _die() {
 #
 # This is a shortcut for the _die() function that simply echos the message.
 die() {
-  _die echo "$@"
+  _die echo "${@}"
 }
 
 ###############################################################################
@@ -128,7 +128,7 @@ die() {
 ###############################################################################
 
 # Get raw options for any commands that expect them.
-_RAW_OPTIONS="$*"
+_RAW_OPTIONS="${*}"
 
 # Steps:
 #
@@ -166,9 +166,9 @@ optstring=h
 # argument to the option, such as wget -qO-)
 unset options
 # while the number of arguments is greater than 0
-while (($#))
+while ((${#}))
 do
-  case $1 in
+  case ${1} in
     # if option is of type -ab
     -[!-]?*)
       # loop over each character starting with the second
@@ -177,11 +177,11 @@ do
         # extract 1 character from position 'i'
         c=${1:i:1}
         # add current char to options
-        options+=("-$c")
+        options+=("-${c}")
 
         # if option takes a required argument, and it's not the last char
         # make the rest of the string its argument
-        if [[ $optstring = *"$c:"* && ${1:i+1} ]]
+        if [[ ${optstring} = *"${c}:"* && ${1:i+1} ]]
         then
           options+=("${1:i+1}")
           break
@@ -196,12 +196,12 @@ do
     --)
       options+=(--endopts)
       shift
-      options+=("$@")
+      options+=("${@}")
       break
       ;;
     # otherwise, nothing special
     *)
-      options+=("$1")
+      options+=("${1}")
       ;;
   esac
 
@@ -219,17 +219,17 @@ unset options
 # command. This is essentially the same as the program arguments, minus those
 # that have been filtered out in the program option parsing loop. This array
 # is initialized with $0, which is the program's name.
-_COMMAND_ARGV=("$0")
+_COMMAND_ARGV=("${0}")
 # Initialize $_CMD and `$_USE_DEBUG`, which can continue to be blank depending
 # on what the program needs.
 _CMD=""
 _USE_DEBUG=0
 
-while [ $# -gt 0 ]
+while [ ${#} -gt 0 ]
 do
-  opt="$1"
+  opt="${1}"
   shift
-  case "$opt" in
+  case "${opt}" in
     -h|--help)
       _CMD="help"
       ;;
@@ -242,11 +242,11 @@ do
     *)
       # The first non-option argument is assumed to be the command name.
       # All subsequent arguments are added to $_COMMAND_ARGV.
-      if [[ -n $_CMD ]]
+      if [[ -n ${_CMD} ]]
       then
-        _COMMAND_ARGV+=("$opt")
+        _COMMAND_ARGV+=("${opt}")
       else
-        _CMD="$opt"
+        _CMD="${opt}"
       fi
       ;;
   esac
@@ -263,10 +263,18 @@ done
 _COMMAND_PARAMETERS=(${_COMMAND_ARGV[*]})
 unset _COMMAND_PARAMETERS[0]
 
-_debug printf "\$_CMD: %s\n" "$_CMD"
-_debug printf "\$_RAW_OPTIONS (one per line):\n%s\n" "$_RAW_OPTIONS"
-_debug printf "\$_COMMAND_ARGV: %s\n" "${_COMMAND_ARGV[*]}"
-_debug printf "\$_COMMAND_PARAMETERS: %s\n" "${_COMMAND_PARAMETERS[*]:-}"
+_debug printf \
+  "\${_CMD}: %s\n" \
+  "${_CMD}"
+_debug printf \
+  "\${_RAW_OPTIONS} (one per line):\n%s\n" \
+  "${_RAW_OPTIONS}"
+_debug printf \
+  "\${_COMMAND_ARGV[*]}: %s\n" \
+  "${_COMMAND_ARGV[*]}"
+_debug printf \
+  "\${_COMMAND_PARAMETERS[*]:-}: %s\n" \
+  "${_COMMAND_PARAMETERS[*]:-}"
 
 ###############################################################################
 # Environment
@@ -275,9 +283,9 @@ _debug printf "\$_COMMAND_PARAMETERS: %s\n" "${_COMMAND_PARAMETERS[*]:-}"
 # $_ME
 #
 # Set to the program's basename.
-_ME=$(basename "$0")
+_ME=$(basename "${0}")
 
-_debug printf "\$_ME: %s\n" "$_ME"
+_debug printf "\${_ME}: %s\n" "${_ME}"
 
 ###############################################################################
 # Load Commands
@@ -308,25 +316,25 @@ _load_commands() {
     # Each element has the format `declare -f function_name`, so set the name
     # to only the 'function_name' part of the string.
     local function_name
-    function_name=$(printf "%s" "$c" | awk '{ print $3 }')
+    function_name=$(printf "%s" "${c}" | awk '{ print $3 }')
 
-    _debug printf "_load_commands() \$function_name: %s\n" "$function_name"
+    _debug printf "_load_commands() \${function_name}: %s\n" "${function_name}"
 
     # Add the function name to the $_DEFINED_COMMANDS array unless it starts
     # with an underscore or is one of the desc(), debug(), or die() functions,
     # since these are treated as having 'private' visibility.
-    if ! ( [[ "$function_name" =~ ^_(.*)  ]] || \
-           [[ "$function_name" == "desc"  ]] || \
-           [[ "$function_name" == "debug" ]] || \
-           [[ "$function_name" == "die"   ]]
+    if ! ( [[ "${function_name}" =~ ^_(.*)  ]] || \
+           [[ "${function_name}" == "desc"  ]] || \
+           [[ "${function_name}" == "debug" ]] || \
+           [[ "${function_name}" == "die"   ]]
     )
     then
-      _DEFINED_COMMANDS+=("$function_name")
+      _DEFINED_COMMANDS+=("${function_name}")
     fi
   done
 
   _debug printf \
-    "commands() \$_DEFINED_COMMANDS:\n%s\n" \
+    "commands() \${_DEFINED_COMMANDS[*]:-}:\n%s\n" \
     "${_DEFINED_COMMANDS[*]:-}"
 }
 
@@ -344,24 +352,24 @@ _load_commands() {
 # NOTE: must be called at end of program after all commands have been defined.
 _main() {
   _debug printf "main(): entering...\n"
-  _debug printf "main() \$_CMD (upon entering): %s\n" "$_CMD"
+  _debug printf "main() \${_CMD} (upon entering): %s\n" "${_CMD}"
 
   # If $_CMD is blank, then set to `$DEFAULT_COMMAND`
-  if [[ -z $_CMD ]]
+  if [[ -z ${_CMD} ]]
   then
-    _CMD="$DEFAULT_COMMAND"
+    _CMD="${DEFAULT_COMMAND}"
   fi
 
   # Load all of the commands.
   _load_commands
 
   # If the command is defined, run it, otherwise return an error.
-  if _contains "$_CMD" "${_DEFINED_COMMANDS[*]:-}"
+  if _contains "${_CMD}" "${_DEFINED_COMMANDS[*]:-}"
   then
     # Pass all comment arguments to the program except for the first ($0).
-    $_CMD "${_COMMAND_PARAMETERS[@]:-}"
+    ${_CMD} "${_COMMAND_PARAMETERS[@]:-}"
   else
-    _die printf "Unknown command: %s\n" "$_CMD"
+    _die printf "Unknown command: %s\n" "${_CMD}"
   fi
 }
 
@@ -377,7 +385,7 @@ _main() {
 # Takes a potential function name as an argument and returns whether a function
 # exists with that name.
 _function_exists() {
-  [ "$(type -t "$1")" == 'function' ]
+  [ "$(type -t "${1}")" == 'function' ]
 }
 
 # _command_exists()
@@ -391,7 +399,7 @@ _function_exists() {
 # For information on why `hash` is used here, see:
 # http://stackoverflow.com/a/677212
 _command_exists() {
-  hash "$1" 2>/dev/null
+  hash "${1}" 2>/dev/null
 }
 
 # _contains()
@@ -404,10 +412,10 @@ _contains() {
   local test_list=(${*:2})
   for _test_element in "${test_list[@]:-}"
   do
-    _debug printf "_contains() \$_test_element: %s\n" "$_test_element"
-    if [[ "$_test_element" == "$1" ]]
+    _debug printf "_contains() \${_test_element}: %s\n" "${_test_element}"
+    if [[ "${_test_element}" == "${1}" ]]
     then
-      _debug printf "_contains() match: %s\n" "$1"
+      _debug printf "_contains() match: %s\n" "${1}"
       return 0
     fi
   done
@@ -427,7 +435,7 @@ _join() {
   local target_array
   local dirty
   local clean
-  separator="$1"
+  separator="${1}"
   target_array=(${@:2})
   dirty="$(printf "${separator}%s"  "${target_array[@]}")"
   clean="${dirty:${#separator}}"
@@ -445,7 +453,7 @@ _join() {
 # This is a shortcut for simple cases where a command wants to check for the
 # presence of options quickly without parsing the options again.
 _command_argv_includes() {
-  _contains "$1" "${_COMMAND_ARGV[*]}"
+  _contains "${1}" "${_COMMAND_ARGV[*]}"
 }
 
 # _blank()
@@ -512,16 +520,16 @@ sudo !!\n"
 # escaping backslashes, which is more common.
 desc() {
   set +e
-  [[ -z $1 ]] && _die printf "desc: No command name specified.\n"
+  [[ -z ${1} ]] && _die printf "desc: No command name specified.\n"
   if [[ -n ${2:-} ]]
   then
-    read -d '' "_desc_$1" <<EOM
-$2
+    read -d '' "_desc_${1}" <<EOM
+${2}
 EOM
-    _debug printf "desc() set with argument: _desc_%s\n" "$1"
+    _debug printf "desc() set with argument: _desc_%s\n" "${1}"
   else
-    read -d '' "_desc_$1"
-    _debug printf "desc() set with pipe: _desc_%s\n" "$1"
+    read -d '' "_desc_${1}"
+    _debug printf "desc() set with pipe: _desc_%s\n" "${1}"
   fi
   set -e
 }
@@ -534,12 +542,12 @@ EOM
 # Prints the description for a given command, provided the description has been
 # set using the desc() function.
 _print_desc() {
-  local var="_desc_$1"
+  local var="_desc_${1}"
   if [[ -n ${!var:-} ]]
   then
     printf "%s\n" "${!var}"
   else
-    printf "No additional information for \`%s\`\n" "$1"
+    printf "No additional information for \`%s\`\n" "${1}"
   fi
 }
 
@@ -551,25 +559,25 @@ _print_desc() {
 
 desc "version" <<EOM
 Usage:
-  $_ME (version | --version)
+  ${_ME} (version | --version)
 
 Description:
   Display the current program version.
 
-  To save you the trouble, the current version is $_VERSION
+  To save you the trouble, the current version is ${_VERSION}
 EOM
 version() {
-  printf "%s\n" "$_VERSION"
+  printf "%s\n" "${_VERSION}"
 }
 
 # Help ########################################################################
 
 desc "help" <<EOM
 Usage:
-  $_ME help [<command>]
+  ${_ME} help [<command>]
 
 Description:
-  Display help information for $_ME or a specified command.
+  Display help information for ${_ME} or a specified command.
 EOM
 help() {
   if [[ ${#_COMMAND_ARGV[@]} = 1 ]]
@@ -583,34 +591,34 @@ help() {
 
 A program for managing host file entries.
 
-Version: $_VERSION
+Version: ${_VERSION}
 
 Usage:
-  $_ME
-  $_ME add <ip> <hostname> [<comment>]
-  $_ME disable (<ip> | <hostname> | <search string>)
-  $_ME disabled
-  $_ME edit
-  $_ME enable (<ip> | <hostname> | <search string>)
-  $_ME enabled
-  $_ME file
-  $_ME list [enabled | disabled | <search string>]
-  $_ME show (<ip> | <hostname> | <search string>)
-  $_ME remove (<ip> | <hostname> | <search string>) [--force]
-  $_ME -h | --help
-  $_ME --version
+  ${_ME}
+  ${_ME} add <ip> <hostname> [<comment>]
+  ${_ME} disable (<ip> | <hostname> | <search string>)
+  ${_ME} disabled
+  ${_ME} edit
+  ${_ME} enable (<ip> | <hostname> | <search string>)
+  ${_ME} enabled
+  ${_ME} file
+  ${_ME} list [enabled | disabled | <search string>]
+  ${_ME} show (<ip> | <hostname> | <search string>)
+  ${_ME} remove (<ip> | <hostname> | <search string>) [--force]
+  ${_ME} -h | --help
+  ${_ME} --version
 
 Options:
   -h --help  Display this help information.
   --version  Display version information.
 
 Help:
-  $_ME help [<command>]
+  ${_ME} help [<command>]
 
 $(commands)
 EOM
   else
-    _print_desc "$1"
+    _print_desc "${1}"
   fi
 }
 
@@ -618,7 +626,7 @@ EOM
 
 desc "commands" <<EOM
 Usage:
-  $_ME commands [--raw]
+  ${_ME} commands [--raw]
 
 Options:
   --raw  Display the command list without formatting.
@@ -667,15 +675,15 @@ commands() {
 
 desc "add" <<EOM
 Usage:
-  $_ME add <ip> <hostname> [<comment>]
+  ${_ME} add <ip> <hostname> [<comment>]
 
 Description:
   Add a given IP address and hostname pair, along with an optional comment.
 EOM
 add() {
-  _debug printf "add() \$1: %s\n" "${1:-}"
-  _debug printf "add() \$2: %s\n" "${2:-}"
-  _debug printf "add() \$3: %s\n" "${3:-}"
+  _debug printf "add() \${1}: %s\n" "${1:-}"
+  _debug printf "add() \${2}: %s\n" "${2:-}"
+  _debug printf "add() \${3}: %s\n" "${3:-}"
 
   _verify_write_permissions
   local ip=${1:-}
@@ -683,12 +691,12 @@ add() {
   local comment=${*:3}
   if [[ -z ${ip} ]]
   then
-    $_ME help add
+    ${_ME} help add
     exit 1
   elif [[ -z ${hostname} ]]
   then
     printf "Please include a hostname\n"
-    $_ME help add
+    ${_ME} help add
     exit 1
   elif grep \
     -e "^${ip}\t${hostname}$" \
@@ -725,7 +733,7 @@ add() {
 
 desc "disable" <<EOM
 Usage:
-  $_ME disable (<ip> | <hostname> | <search string>)
+  ${_ME} disable (<ip> | <hostname> | <search string>)
 
 Description:
   Disable one or more records based on a given ip address, hostname, or
@@ -733,13 +741,13 @@ Description:
 EOM
 disable() {
   _verify_write_permissions
-  local search_string=$1
+  local search_string="${1}"
   if [[ -z "${search_string}" ]]
   then
-    $_ME help disable
+    ${_ME} help disable
     exit 1
   else
-    _debug printf "disable() \$search_string: %s\n" "$search_string"
+    _debug printf "disable() \${search_string}: %s\n" "${search_string}"
 
     target_regex_ip="^\(${search_string}[${_TAB_SPACE_}]..*\)$"
     target_regex_commented_hostname="^\([^#]..*[${_TAB_SPACE_}]${search_string}[${_TAB_SPACE_}]..*\)$"
@@ -757,7 +765,7 @@ disable() {
         -e "s/${target_regex_hostname}/\1/p" \
         "${HOSTS_PATH}"
     )
-    _debug printf "disable() \$targets: %s\n" "$targets"
+    _debug printf "disable() \${targets}: %s\n" "${targets}"
     if [[ -z "${targets}" ]]
     then
       _die printf "Not found: %s\n" "${search_string}"
@@ -779,31 +787,31 @@ disable() {
 
 desc "disabled" <<EOM
 Usage:
-  $_ME disabled
+  ${_ME} disabled
 
 Description:
   List all disabled records. This is an alias for \`hosts list disabled\`.
 EOM
 disabled() {
-  $_ME list disabled
+  ${_ME} list disabled
 }
 
 # ------------------------------------------------------------------------ edit
 
 desc "edit" <<EOM
 Usage:
-  $_ME edit
+  ${_ME} edit
 
 Description:
   Open the ${HOSTS_PATH} file in your \$EDITOR.
 EOM
 edit() {
   _verify_write_permissions
-  if [[ -z "$EDITOR" ]]
+  if [[ -z "${EDITOR}" ]]
   then
     _die printf "\$EDITOR not set.\n"
   else
-    "$EDITOR" "${HOSTS_PATH}"
+    "${EDITOR}" "${HOSTS_PATH}"
   fi
 }
 
@@ -811,7 +819,7 @@ edit() {
 
 desc "enable" <<EOM
 Usage:
-  $_ME enable (<ip> | <hostname> | <search string>)
+  ${_ME} enable (<ip> | <hostname> | <search string>)
 
 Description:
   Enable one or more disabled records based on a given ip address, hostname,
@@ -819,13 +827,13 @@ Description:
 EOM
 enable() {
   _verify_write_permissions
-  local search_string=$1
+  local search_string="${1}"
   if [[ -z "${search_string}" ]]
   then
-    $_ME help enable
+    ${_ME} help enable
     exit 1
   else
-    _debug printf "enable() \$search_string: %s\n" "$search_string"
+    _debug printf "enable() \${search_string}: %s\n" "${search_string}"
 
     target_regex_ip="^\#disabled: \(${search_string}[${_TAB_SPACE_}]..*\)$"
     target_regex_commented_hostname="^\#disabled: \(..*[${_TAB_SPACE_}]${search_string}[${_TAB_SPACE_}]..*\)$"
@@ -843,7 +851,7 @@ enable() {
         -e "s/${target_regex_hostname}/\1/p" \
         "${HOSTS_PATH}"
     )
-    _debug printf "enable() \$targets: %s\n" "$targets"
+    _debug printf "enable() \${targets}: %s\n" "${targets}"
     if [[ -z "${targets}" ]]
     then
       _die printf "Not found: %s\n" "${search_string}"
@@ -865,20 +873,20 @@ enable() {
 
 desc "enabled" <<EOM
 Usage:
-  $_ME enabled
+  ${_ME} enabled
 
 Description:
   List all enabled records. This is an alias for \`hosts list enabled\`.
 EOM
 enabled() {
-  $_ME list enabled
+  ${_ME} list enabled
 }
 
 # ------------------------------------------------------------------------ file
 
 desc "file" <<EOM
 Usage:
-  $_ME file
+  ${_ME} file
 
 Description:
   Print the entire contents of the ${HOSTS_PATH} file.
@@ -891,7 +899,7 @@ file() {
 
 desc "list" <<EOM
 Usage:
-  $_ME list [enabled | disabled | <search string>]
+  ${_ME} list [enabled | disabled | <search string>]
 
 Description:
   List the existing IP / hostname pairs, optionally limited to a specified
@@ -905,16 +913,16 @@ list() {
     sed -n "s/^\#disabled: \(.*\)$/\1/p" "${HOSTS_PATH}"
   )
 
-  if [[ -n "$1" ]]
+  if [[ -n "${1}" ]]
   then
-    if [[ "$1" == "disabled" ]]
+    if [[ "${1}" == "disabled" ]]
     then
       printf "%s\n" "${disabled_records}"
-    elif [[ "$1" == "enabled" ]]
+    elif [[ "${1}" == "enabled" ]]
     then
       grep -v -e '^$' -e '^\s*\#' "${HOSTS_PATH}"
     else
-      $_ME show "$1"
+      ${_ME} show "${1}"
     fi
   else
     # NOTE: use separate expressions since using a | for the or results in
@@ -931,8 +939,8 @@ list() {
 
 desc "remove" <<EOM
 Usage:
-  $_ME remove (<ip> | <hostname> | <search string>) [--force]
-  $_ME remove <ip> <hostname>
+  ${_ME} remove (<ip> | <hostname> | <search string>) [--force]
+  ${_ME} remove <ip> <hostname>
 
 Options:
   --force  Skip the confirmation prompt.
@@ -951,17 +959,17 @@ remove() {
   local search_hostname=""
   local search_string=""
 
-  _debug printf "remove() \$1: %s\n" "${1:-}"
-  _debug printf "remove() \$2: %s\n" "${2:-}"
+  _debug printf "remove() \${1}: %s\n" "${1:-}"
+  _debug printf "remove() \${2}: %s\n" "${2:-}"
 
   for arg in "${_COMMAND_ARGV[@]:-}"
   do
-    case $arg in
+    case ${arg} in
       --force)
         force_skip_prompt=1
         ;;
       *)
-        arguments+=($arg)
+        arguments+=(${arg})
         ;;
     esac
   done
@@ -972,17 +980,17 @@ remove() {
 
   if [[ -z "${arguments[1]:-}" ]]
   then
-    $_ME help remove
+    ${_ME} help remove
     exit 1
   elif [[ -n "${arguments[2]:-}" ]]
   then
     search_ip="${arguments[1]}"
     search_hostname="${arguments[2]}"
     is_search_pair=1
-    _debug printf "remove() \$is_search_pair: %s\n" "$is_search_pair"
+    _debug printf "remove() \${is_search_pair}: %s\n" "${is_search_pair}"
   else
     search_string="${arguments[1]:-}"
-    _debug printf "remove() \$search_string: %s\n" "$search_string"
+    _debug printf "remove() \${search_string}: %s\n" "${search_string}"
   fi
 
   # Regular Expression Notes
@@ -1026,11 +1034,11 @@ remove() {
 
   if ! ((force_skip_prompt))
   then
-    printf "Removing the following records:\n%s\n" "$target_records"
+    printf "Removing the following records:\n%s\n" "${target_records}"
     while true
     do
       read -p "Are you sure you want to proceed? [y/N] " yn
-      case $yn in
+      case ${yn} in
         [Yy]* )
           break
           ;;
@@ -1066,34 +1074,34 @@ remove() {
 
 desc "show" <<EOM
 Usage:
-  $_ME show (<ip> | <hostname> | <search string>)
+  ${_ME} show (<ip> | <hostname> | <search string>)
 
 Description:
   Print entries matching a given IP address, hostname, or search string.
 EOM
 show() {
-  if [[ -n "$1" ]]
+  if [[ -n "${1}" ]]
   then
     # Run `sed` before `grep` to avoid conflict that supress `sed` output.
     local disabled_records
     disabled_records=$(
-      sed -n "s/^\#\(disabled: .*$1.*\)$/\1/p" "${HOSTS_PATH}"
+      sed -n "s/^\#\(disabled: .*${1}.*\)$/\1/p" "${HOSTS_PATH}"
     )
     local enabled_records
     enabled_records=$(
-      grep "^[^#]*$1" "${HOSTS_PATH}"
+      grep "^[^#]*${1}" "${HOSTS_PATH}"
     )
     # Output disabled records secondly for better organization.
-    if [[ -n "$enabled_records"  ]]
+    if [[ -n "${enabled_records}"  ]]
     then
-      printf "%s\n" "$enabled_records"
+      printf "%s\n" "${enabled_records}"
     fi
-    if [[ -n "$disabled_records" ]]
+    if [[ -n "${disabled_records}" ]]
     then
-      printf "%s\n" "$disabled_records"
+      printf "%s\n" "${disabled_records}"
     fi
   else
-    $_ME help show
+    ${_ME} help show
     exit 1
   fi
 }
diff --git a/test/add.bats b/test/add.bats
index 71732d0..c9bb457 100644
--- a/test/add.bats
+++ b/test/add.bats
@@ -5,25 +5,25 @@ load test_helper
 # `hosts add` #################################################################
 
 @test "\`add\` with no arguments exits with status 1." {
-  run "$_HOSTS" add
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 1 ]]
+  run "${_HOSTS}" add
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 1 ]]
 }
 
 @test "\`add\` with no argument does not change the hosts file." {
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" add
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "$(cat "${HOSTS_PATH}")" == "${_original}" ]]
 }
 
 @test "\`add\` with no arguments prints help information." {
-  run "$_HOSTS" add
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts add <ip> <hostname> [<comment>]" ]]
 }
@@ -31,25 +31,25 @@ load test_helper
 # `hosts add <ip>` ############################################################
 
 @test "\`add <ip>\` exits with status 1." {
-  run "$_HOSTS" add 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 1 ]]
+  run "${_HOSTS}" add 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 1 ]]
 }
 
 @test "\`add <ip>\` does not change the hosts file." {
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" add 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "$(cat "${HOSTS_PATH}")" == "${_original}" ]]
 }
 
 @test "\`add <ip>\` prints help information." {
-  run "$_HOSTS" add 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Please include a hostname" ]]
   [[ "${lines[1]}" == "Usage:" ]]
   [[ "${lines[2]}" == "  hosts add <ip> <hostname> [<comment>]" ]]
@@ -58,18 +58,18 @@ load test_helper
 # `hosts add <ip> <hostname>` #################################################
 
 @test "\`add <ip> <hostname>\` exits with status 0." {
-  run "$_HOSTS" add 0.0.0.0 example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" add 0.0.0.0 example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`add <ip> <hostname>\` adds the entry to the hosts file." {
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" add 0.0.0.0 example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add 0.0.0.0 example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   _compare '0.0.0.0	example.com' "$(sed -n '11p' "${HOSTS_PATH}")"
   [[ "$(cat "${HOSTS_PATH}")" != "${_original}" ]]
@@ -77,9 +77,9 @@ load test_helper
 }
 
 @test "\`add <ip> <hostname>\` prints feedback." {
-  run "$_HOSTS" add 0.0.0.0 example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add 0.0.0.0 example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Added:" ]]
   [[ "${lines[1]}" == "0.0.0.0	example.com" ]]
 }
@@ -87,26 +87,26 @@ load test_helper
 # `hosts add <ip> <hostname> [comment]` #######################################
 
 @test "\`add <ip> <hostname> [comment]\` exits with status 0." {
-  run "$_HOSTS" add 0.0.0.0 example.com 'Comment.'
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" add 0.0.0.0 example.com 'Comment.'
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`add <ip> <hostname> [comment]\` adds the entry to the hosts file." {
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" add 0.0.0.0 example.com 'Comment.'
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add 0.0.0.0 example.com 'Comment.'
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "$(cat "${HOSTS_PATH}")" != "${_original}" ]]
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "0.0.0.0	example.com	# Comment." ]]
 }
 
 @test "\`add <ip> <hostname> [comment]\` prints feedback." {
-  run "$_HOSTS" add 0.0.0.0 example.com 'Comment.'
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" add 0.0.0.0 example.com 'Comment.'
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Added:" ]]
   [[ "${lines[1]}" == "0.0.0.0	example.com	# Comment." ]]
 }
@@ -114,14 +114,14 @@ load test_helper
 # help ########################################################################
 
 @test "\`help add\` exits with status 0." {
-  run "$_HOSTS" help add
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help add
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help add\` prints help information." {
-  run "$_HOSTS" help add
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help add
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts add <ip> <hostname> [<comment>]" ]]
 }
diff --git a/test/disable.bats b/test/disable.bats
index 6216f71..f496e0a 100644
--- a/test/disable.bats
+++ b/test/disable.bats
@@ -5,25 +5,25 @@ load test_helper
 # `hosts disable` #############################################################
 
 @test "\`disable\` with no arguments exits with status 1." {
-  run "$_HOSTS" disable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 1 ]]
+  run "${_HOSTS}" disable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 1 ]]
 }
 
 @test "\`disable\` with no argument does not change the hosts file." {
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" disable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "$(cat "${HOSTS_PATH}")" == "${_original}" ]]
 }
 
 @test "\`disable\` with no arguments prints help information." {
-  run "$_HOSTS" disable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts disable (<ip> | <hostname> | <search string>)" ]]
 }
@@ -32,26 +32,26 @@ load test_helper
 
 @test "\`disable <ip>\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 127.0.0.1 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 127.0.0.1 example.net
   }
 
-  run "$_HOSTS" disable 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" disable 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`disable <ip>\` updates the hosts file." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 127.0.0.1 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 127.0.0.1 example.net
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" disable 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.com" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "127.0.0.1	example.net" ]]
@@ -59,14 +59,14 @@ load test_helper
 
 @test "\`disable <ip>\` disables all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" disable 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.com" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.net" ]]
@@ -74,13 +74,13 @@ load test_helper
 
 @test "\`disable <ip>\` prints feedback." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 127.0.0.1 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 127.0.0.1 example.net
   }
 
-  run "$_HOSTS" disable 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Disabling:" ]]
   [[ "${lines[1]}" == "0.0.0.0	example.com" ]]
 }
@@ -89,26 +89,26 @@ load test_helper
 
 @test "\`disable <hostname>\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 127.0.0.1 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 127.0.0.1 example.net
   }
 
-  run "$_HOSTS" disable example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" disable example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`disable <hostname>\` updates the hosts file." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 127.0.0.1 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 127.0.0.1 example.net
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" disable example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.com" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "127.0.0.1	example.net" ]]
@@ -116,14 +116,14 @@ load test_helper
 
 @test "\`disable <hostname>\` disables all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 127.0.0.1 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 127.0.0.1 example.com
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" disable example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.com" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "#disabled: 127.0.0.1	example.com" ]]
@@ -131,13 +131,13 @@ load test_helper
 
 @test "\`disable <hostname>\` prints feedback." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 127.0.0.1 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 127.0.0.1 example.net
   }
 
-  run "$_HOSTS" disable example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disable example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Disabling:" ]]
   [[ "${lines[1]}" == "0.0.0.0	example.com" ]]
 }
@@ -145,14 +145,14 @@ load test_helper
 # help ########################################################################
 
 @test "\`help disable\` exits with status 0." {
-  run "$_HOSTS" help disable
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help disable
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help disable\` prints help information." {
-  run "$_HOSTS" help disable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help disable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts disable (<ip> | <hostname> | <search string>)" ]]
 }
diff --git a/test/disabled.bats b/test/disabled.bats
index 54a0e5f..8147d1a 100644
--- a/test/disabled.bats
+++ b/test/disabled.bats
@@ -6,29 +6,29 @@ load test_helper
 
 @test "\`disabled\` with no arguments exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.1 example.com
-    run "$_HOSTS" disable example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.1 example.com
+    run "${_HOSTS}" disable example.com
   }
 
-  run "$_HOSTS" disabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" disabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`disabled\` with no arguments prints list of disabled records." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.1 example.com
-    run "$_HOSTS" disable example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.1 example.com
+    run "${_HOSTS}" disable example.com
   }
 
-  run "$_HOSTS" disabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" disabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "0.0.0.0	example.com" ]]
   [[ "${lines[1]}" == "127.0.0.1	example.com" ]]
   [[ "${lines[2]}" == "" ]]
@@ -37,14 +37,14 @@ load test_helper
 # help ########################################################################
 
 @test "\`help disabled\` exits with status 0." {
-  run "$_HOSTS" help disabled
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help disabled
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help disabled\` prints help information." {
-  run "$_HOSTS" help disabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help disabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts disabled" ]]
 }
diff --git a/test/enable.bats b/test/enable.bats
index 77c76b5..157546b 100644
--- a/test/enable.bats
+++ b/test/enable.bats
@@ -5,25 +5,25 @@ load test_helper
 # `hosts enable` ##############################################################
 
 @test "\`enable\` with no arguments exits with status 1." {
-  run "$_HOSTS" enable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 1 ]]
+  run "${_HOSTS}" enable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 1 ]]
 }
 
 @test "\`enable\` with no argument does not change the hosts file." {
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" enable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "$(cat "${HOSTS_PATH}")" == "${_original}" ]]
 }
 
 @test "\`enable\` with no arguments prints help information." {
-  run "$_HOSTS" enable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts enable (<ip> | <hostname> | <search string>)" ]]
 }
@@ -32,31 +32,31 @@ load test_helper
 
 @test "\`enable <ip>\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 127.0.0.2
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 127.0.0.2
   }
 
-  run "$_HOSTS" enable 127.0.0.2
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" enable 127.0.0.2
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`enable <ip>\` updates the hosts file." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
-    run "$_HOSTS" disable 127.0.0.2
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
+    run "${_HOSTS}" disable 127.0.0.2
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" enable 127.0.0.2
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable 127.0.0.2
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.com" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.net" ]]
@@ -65,17 +65,17 @@ load test_helper
 
 @test "\`enable <ip>\` enables all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
-    run "$_HOSTS" disable 127.0.0.2
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
+    run "${_HOSTS}" disable 127.0.0.2
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" enable 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare \
     "${_original}" \
     "$(cat "${HOSTS_PATH}")"
@@ -96,15 +96,15 @@ load test_helper
 
 @test "\`disable <ip>\` prints feedback." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 127.0.0.2
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 127.0.0.2
   }
 
-  run "$_HOSTS" enable 127.0.0.2
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable 127.0.0.2
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Enabling:" ]]
   [[ "${lines[1]}" == "127.0.0.2	example.com" ]]
 }
@@ -113,30 +113,30 @@ load test_helper
 
 @test "\`enable <hostname>\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" enable example.net
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" enable example.net
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`enable <hostname>\` updates the hosts file." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" enable example.net
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable example.net
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "#disabled: 0.0.0.0	example.com" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "0.0.0.0	example.net" ]]
@@ -145,17 +145,17 @@ load test_helper
 
 @test "\`enable <hostname>\` enables all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
-    run "$_HOSTS" disable 127.0.0.2
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
+    run "${_HOSTS}" disable 127.0.0.2
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" enable example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare \
     "${_original}" \
     "$(cat "${HOSTS_PATH}")"
@@ -176,15 +176,15 @@ load test_helper
 
 @test "\`disable <hostname>\` prints feedback." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" enable example.net
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enable example.net
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Enabling:" ]]
   [[ "${lines[1]}" == "0.0.0.0	example.net" ]]
 }
@@ -192,14 +192,14 @@ load test_helper
 # help ########################################################################
 
 @test "\`help enable\` exits with status 0." {
-  run "$_HOSTS" help enable
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help enable
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help enable\` prints help information." {
-  run "$_HOSTS" help enable
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help enable
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts enable (<ip> | <hostname> | <search string>)" ]]
 }
diff --git a/test/enabled.bats b/test/enabled.bats
index 8d50741..2a0f039 100644
--- a/test/enabled.bats
+++ b/test/enabled.bats
@@ -6,29 +6,29 @@ load test_helper
 
 @test "\`enabled\` with no arguments exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" enabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" enabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`enabled\` with no arguments prints list of enabled records." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" enabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" enabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "127.0.0.1	localhost" ]]
   [[ "${lines[1]}" == "255.255.255.255	broadcasthost" ]]
   [[ "${lines[2]}" == "::1             localhost" ]]
@@ -39,14 +39,14 @@ load test_helper
 # help ########################################################################
 
 @test "\`help enabled\` exits with status 0." {
-  run "$_HOSTS" help enabled
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help enabled
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help enabled\` prints help information." {
-  run "$_HOSTS" help enabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help enabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts enabled" ]]
 }
diff --git a/test/file.bats b/test/file.bats
index b907112..e08a3fd 100644
--- a/test/file.bats
+++ b/test/file.bats
@@ -3,26 +3,26 @@
 load test_helper
 
 @test "\`file\` exits with status 0." {
-  run "$_HOSTS" file
-  [ "$status" -eq 0 ]
+  run "${_HOSTS}" file
+  [ "${status}" -eq 0 ]
 }
 
 @test "\`file\` prints \$HOSTS_PATH contents." {
-  run "$_HOSTS" file
-  [[ "$output" == "$(cat $HOSTS_PATH)" ]]
+  run "${_HOSTS}" file
+  [[ "${output}" == "$(cat ${HOSTS_PATH})" ]]
 }
 
 # help ########################################################################
 
 @test "\`help file\` exits with status 0." {
-  run "$_HOSTS" help file
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help file
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help file\` prints help information." {
-  run "$_HOSTS" help file
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help file
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts file" ]]
 }
diff --git a/test/help.bats b/test/help.bats
index e12bcf4..bcf17da 100644
--- a/test/help.bats
+++ b/test/help.bats
@@ -14,27 +14,27 @@ HEREDOC
 export _HELP_HEADER
 
 @test "\`help\` with no arguments exits with status 0." {
-  run "$_HOSTS" help
-  [ "$status" -eq 0 ]
+  run "${_HOSTS}" help
+  [ "${status}" -eq 0 ]
 }
 
 @test "\`help\` with no arguments prints default help." {
-  run "$_HOSTS" help
-  [[ $(IFS=$'\n'; echo "${lines[*]:0:5}") == "$_HELP_HEADER" ]]
+  run "${_HOSTS}" help
+  [[ $(IFS=$'\n'; echo "${lines[*]:0:5}") == "${_HELP_HEADER}" ]]
 }
 
 @test "\`hosts -h\` prints default help." {
-  run "$_HOSTS" -h
-  [[ $(IFS=$'\n'; echo "${lines[*]:0:5}") == "$_HELP_HEADER" ]]
+  run "${_HOSTS}" -h
+  [[ $(IFS=$'\n'; echo "${lines[*]:0:5}") == "${_HELP_HEADER}" ]]
 }
 
 @test "\`hosts --help\` prints default help." {
-  run "$_HOSTS" --help
-  [[ $(IFS=$'\n'; echo "${lines[*]:0:5}") == "$_HELP_HEADER" ]]
+  run "${_HOSTS}" --help
+  [[ $(IFS=$'\n'; echo "${lines[*]:0:5}") == "${_HELP_HEADER}" ]]
 }
 
 @test "\`hosts help help\` prints \`help\` subcommand usage." {
-  run "$_HOSTS" help help
+  run "${_HOSTS}" help help
   _expected="$(
     cat <<HEREDOC
 Usage:
@@ -44,5 +44,5 @@ Description:
   Display help information for hosts or a specified command.
 HEREDOC
   )"
-  [[ "$output" == "$_expected" ]]
+  [[ "${output}" == "${_expected}" ]]
 }
diff --git a/test/hosts.bats b/test/hosts.bats
index 5fa791b..e1434d3 100644
--- a/test/hosts.bats
+++ b/test/hosts.bats
@@ -3,12 +3,12 @@
 load test_helper
 
 @test "\`hosts\` with no arguments exits with status 0." {
-  run "$_HOSTS"
-  [ "$status" -eq 0 ]
+  run "${_HOSTS}"
+  [ "${status}" -eq 0 ]
 }
 
 @test "\`hosts\` with no arguments prints enabled rules." {
-  run "$_HOSTS"
+  run "${_HOSTS}"
   [[ "${#lines[@]}" -eq 4 ]]
   [[ "${lines[0]}" == "127.0.0.1	localhost" ]]
   [[ "${lines[1]}" == "255.255.255.255	broadcasthost" ]]
diff --git a/test/list.bats b/test/list.bats
index a069b71..0a8daa9 100644
--- a/test/list.bats
+++ b/test/list.bats
@@ -6,29 +6,29 @@ load test_helper
 
 @test "\`list\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" list
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" list
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`list\` prints lists of enabled and disabled records." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" list
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" list
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _expected="\
 127.0.0.1	localhost
 255.255.255.255	broadcasthost
@@ -39,37 +39,37 @@ fe80::1%lo0	localhost
 Disabled:
 0.0.0.0	example.com
 0.0.0.0	example.net"
-  _compare "'$_expected'" "'$output'"
-  [[ "$output" == "$_expected" ]]
+  _compare "'${_expected}'" "'${output}'"
+  [[ "${output}" == "${_expected}" ]]
 }
 
 # `hosts list enabled` ########################################################
 
 @test "\`list enabled\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" list enabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" list enabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`list enabled\` prints list of enabled records." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" list enabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" list enabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "127.0.0.1	localhost" ]]
   [[ "${lines[1]}" == "255.255.255.255	broadcasthost" ]]
   [[ "${lines[2]}" == "::1             localhost" ]]
@@ -81,29 +81,29 @@ Disabled:
 
 @test "\`list disabled\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.1 example.com
-    run "$_HOSTS" disable example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.1 example.com
+    run "${_HOSTS}" disable example.com
   }
 
-  run "$_HOSTS" disabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" disabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`list disabled\` prints list of disabled records." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.1 example.com
-    run "$_HOSTS" disable example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.1 example.com
+    run "${_HOSTS}" disable example.com
   }
 
-  run "$_HOSTS" list disabled
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" list disabled
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "0.0.0.0	example.com" ]]
   [[ "${lines[1]}" == "127.0.0.1	example.com" ]]
   [[ "${lines[2]}" == "" ]]
@@ -113,27 +113,27 @@ Disabled:
 
 @test "\`list <search string>\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.1 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.1 example.com
   }
 
-  run "$_HOSTS" list example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" list example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`list <search string>\` prints list of matching records." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.1 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.1 example.com
   }
 
-  run "$_HOSTS" list example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" list example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "0.0.0.0	example.com" ]]
   [[ "${lines[1]}" == "127.0.0.1	example.com" ]]
   [[ "${lines[2]}" == "" ]]
@@ -142,14 +142,14 @@ Disabled:
 # help ########################################################################
 
 @test "\`help list\` exits with status 0." {
-  run "$_HOSTS" help list
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help list
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help list\` prints help information." {
-  run "$_HOSTS" help list
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help list
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts list [enabled | disabled | <search string>]" ]]
 }
diff --git a/test/remove.bats b/test/remove.bats
index d7f2488..8d380b8 100644
--- a/test/remove.bats
+++ b/test/remove.bats
@@ -5,25 +5,25 @@ load test_helper
 # `hosts remove` #################################################################
 
 @test "\`remove\` with no arguments exits with status 1." {
-  run "$_HOSTS" remove
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 1 ]]
+  run "${_HOSTS}" remove
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 1 ]]
 }
 
 @test "\`remove\` with no argument does not change the hosts file." {
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" remove
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "$(cat "${HOSTS_PATH}")" == "${_original}" ]]
 }
 
 @test "\`remove\` with no arguments prints help information." {
-  run "$_HOSTS" remove
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts remove (<ip> | <hostname> | <search string>) [--force]" ]]
 }
@@ -32,56 +32,56 @@ load test_helper
 
 @test "\`remove <invalid> --force\` exits with status 1." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
 
-  run "$_HOSTS" remove 127.0.0.3 --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 1 ]]
+  run "${_HOSTS}" remove 127.0.0.3 --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 1 ]]
 }
 
 @test "\`remove <invalid> --force\` prints error message." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
 
-  run "$_HOSTS" remove 127.0.0.3 --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $output == "No matching records found." ]]
+  run "${_HOSTS}" remove 127.0.0.3 --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${output} == "No matching records found." ]]
 }
 
 # `hosts remove <ip> --force` #################################################
 
 @test "\`remove <ip> --force\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
 
-  run "$_HOSTS" remove 127.0.0.2 --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" remove 127.0.0.2 --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`remove <ip> --force\` updates the hosts file." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" remove 127.0.0.2 --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove 127.0.0.2 --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "0.0.0.0	example.com" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "0.0.0.0	example.net" ]]
@@ -90,17 +90,17 @@ load test_helper
 
 @test "\`remove <ip>\` removes all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 0.0.0.0 example.dev
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable example.dev
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.dev
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable example.dev
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" remove 0.0.0.0 --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove 0.0.0.0 --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _expected="\
 ##
 # Host Database
@@ -113,21 +113,21 @@ load test_helper
 ::1             localhost
 fe80::1%lo0	localhost
 127.0.0.2	example.com"
-  _compare "'$_expected'" "'$(cat "${HOSTS_PATH}")'"
-  [[ "$(cat "${HOSTS_PATH}")" != "$_original" ]]
-  [[ "$(cat "${HOSTS_PATH}")" == "$_expected" ]]
+  _compare "'${_expected}'" "'$(cat "${HOSTS_PATH}")'"
+  [[ "$(cat "${HOSTS_PATH}")" != "${_original}" ]]
+  [[ "$(cat "${HOSTS_PATH}")" == "${_expected}" ]]
 }
 
 @test "\`remove <ip>\` prints feedback." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
 
-  run "$_HOSTS" remove 127.0.0.2 --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove 127.0.0.2 --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Removed:" ]]
   [[ "${lines[1]}" == "127.0.0.2	example.com" ]]
 }
@@ -136,28 +136,28 @@ fe80::1%lo0	localhost
 
 @test "\`remove <hostname> --force\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
 
-  run "$_HOSTS" remove example.com --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" remove example.com --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`remove <hostname> --force\` updates the hosts file." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" remove example.com --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove example.com --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _compare "${_original}" "$(cat "${HOSTS_PATH}")"
   [[ "$(sed -n '11p' "${HOSTS_PATH}")" == "0.0.0.0	example.net" ]]
   [[ "$(sed -n '12p' "${HOSTS_PATH}")" == "" ]]
@@ -165,17 +165,17 @@ fe80::1%lo0	localhost
 
 @test "\`remove <hostname>\` removes all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 0.0.0.0 example.dev
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable example.dev
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 0.0.0.0 example.dev
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable example.dev
   }
   _original="$(cat "${HOSTS_PATH}")"
 
-  run "$_HOSTS" remove example.com --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove example.com --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _expected="\
 ##
 # Host Database
@@ -189,39 +189,39 @@ fe80::1%lo0	localhost
 fe80::1%lo0	localhost
 0.0.0.0	example.net
 #disabled: 0.0.0.0	example.dev"
-  _compare "'$_expected'" "'$(cat "${HOSTS_PATH}")'"
-  [[ "$(cat "${HOSTS_PATH}")" != "$_original" ]]
-  [[ "$(cat "${HOSTS_PATH}")" == "$_expected" ]]
+  _compare "'${_expected}'" "'$(cat "${HOSTS_PATH}")'"
+  [[ "$(cat "${HOSTS_PATH}")" != "${_original}" ]]
+  [[ "$(cat "${HOSTS_PATH}")" == "${_expected}" ]]
 }
 
 @test "\`remove <hostname>\` prints feedback." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
   }
 
-  run "$_HOSTS" remove example.com --force
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" remove example.com --force
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   _expected="\
 Removed:
 0.0.0.0	example.com
 127.0.0.2	example.com"
-  [[ "$output" == "$_expected" ]]
+  [[ "${output}" == "${_expected}" ]]
 }
 
 # help ########################################################################
 
 @test "\`help remove\` exits with status 0." {
-  run "$_HOSTS" help remove
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help remove
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help remove\` prints help information." {
-  run "$_HOSTS" help remove
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help remove
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts remove (<ip> | <hostname> | <search string>) [--force]" ]]
 }
diff --git a/test/show.bats b/test/show.bats
index 937e4c2..0936912 100644
--- a/test/show.bats
+++ b/test/show.bats
@@ -5,16 +5,16 @@ load test_helper
 # `hosts show` ##############################################################
 
 @test "\`show\` with no arguments exits with status 1." {
-  run "$_HOSTS" show
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 1 ]]
+  run "${_HOSTS}" show
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 1 ]]
 }
 
 @test "\`show\` with no arguments prints help information." {
-  run "$_HOSTS" show
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" show
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts show (<ip> | <hostname> | <search string>)" ]]
 }
@@ -23,29 +23,29 @@ load test_helper
 
 @test "\`show <ip>\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable example.com
   }
 
-  run "$_HOSTS" show 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" show 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`enable <ip>\` shows all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable example.com
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable example.com
   }
 
-  run "$_HOSTS" show 0.0.0.0
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" show 0.0.0.0
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
 
   [[ "${lines[0]}" == "0.0.0.0	example.net" ]]
   [[ "${lines[1]}" == "disabled: 0.0.0.0	example.com" ]]
@@ -55,29 +55,29 @@ load test_helper
 
 @test "\`show <hostname>\` exits with status 0." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" show example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" show example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`enable <hostname>\` shows all matches." {
   {
-    run "$_HOSTS" add 0.0.0.0 example.com
-    run "$_HOSTS" add 0.0.0.0 example.net
-    run "$_HOSTS" add 127.0.0.2 example.com
-    run "$_HOSTS" disable 0.0.0.0
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    run "${_HOSTS}" add 0.0.0.0 example.net
+    run "${_HOSTS}" add 127.0.0.2 example.com
+    run "${_HOSTS}" disable 0.0.0.0
   }
 
-  run "$_HOSTS" show example.com
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" show example.com
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
 
   [[ "${lines[0]}" == "127.0.0.2	example.com" ]]
   [[ "${lines[1]}" == "disabled: 0.0.0.0	example.com" ]]
@@ -86,14 +86,14 @@ load test_helper
 # help ########################################################################
 
 @test "\`help show\` exits with status 0." {
-  run "$_HOSTS" help show
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help show
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help show\` prints help information." {
-  run "$_HOSTS" help show
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help show
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts show (<ip> | <hostname> | <search string>)" ]]
 }
diff --git a/test/version.bats b/test/version.bats
index ad14e4f..1b838bc 100644
--- a/test/version.bats
+++ b/test/version.bats
@@ -3,38 +3,38 @@
 load test_helper
 
 @test "\`hosts version\` returns with 0 status." {
-  run "$_HOSTS" version
-  [[ "$status" -eq 0 ]]
+  run "${_HOSTS}" version
+  [[ "${status}" -eq 0 ]]
 }
 
 @test "\`hosts version\` prints a version number." {
-  run "$_HOSTS" version
-  printf "'%s'" "$output"
-  echo "$output" | grep -q '\d\+\.\d\+\.\d\+'
+  run "${_HOSTS}" version
+  printf "'%s'" "${output}"
+  echo "${output}" | grep -q '\d\+\.\d\+\.\d\+'
 }
 
 @test "\`hosts --version\` returns with 0 status." {
-  run "$_HOSTS" --version
-  [[ "$status" -eq 0 ]]
+  run "${_HOSTS}" --version
+  [[ "${status}" -eq 0 ]]
 }
 
 @test "\`hosts --version\` prints a version number." {
-  run "$_HOSTS" --version
-  printf "'%s'" "$output"
-  echo "$output" | grep -q '\d\+\.\d\+\.\d\+'
+  run "${_HOSTS}" --version
+  printf "'%s'" "${output}"
+  echo "${output}" | grep -q '\d\+\.\d\+\.\d\+'
 }
 
 # help ########################################################################
 
 @test "\`help version\` exits with status 0." {
-  run "$_HOSTS" help version
-  [[ $status -eq 0 ]]
+  run "${_HOSTS}" help version
+  [[ ${status} -eq 0 ]]
 }
 
 @test "\`help version\` prints help information." {
-  run "$_HOSTS" help version
-  printf "\$status: %s\n" "$status"
-  printf "\$output: '%s'\n" "$output"
+  run "${_HOSTS}" help version
+  printf "\${status}: %s\n" "${status}"
+  printf "\${output}: '%s'\n" "${output}"
   [[ "${lines[0]}" == "Usage:" ]]
   [[ "${lines[1]}" == "  hosts (version | --version)" ]]
 }