diff --git a/README.md b/README.md
index b5cf731..1c6fd38 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # goto
 
-`goto` is a bash utility allowing users to change faster to aliased directories supporting auto-completion :feet:
+`goto` is a shell utility allowing users to change faster to aliased directories supporting auto-completion :feet:
 
 ## How does it work?
 
@@ -17,7 +17,7 @@ goto dev
 
 ## goto completion
 
-`goto` comes with a nice auto-completion script so that whenever you press the `tab` key after the `goto` command, bash prompts with suggestions of the available aliases:
+`goto` comes with a nice auto-completion script so that whenever you press the `tab` key after the `goto` command, bash or zsh prompts with suggestions of the available aliases:
 
 ```bash
 $ goto <tab>
@@ -28,12 +28,21 @@ rubies /home/iridakos/.rvm/rubies
 
 ## Installation
 
-Copy the file `goto.bash` somewhere in your filesystem and add a line in your `.bashrc` to source it.
+### Via script
+Clone the repository and run the install script as super user or root:
+```bash
+git clone https://github.com/iridakos/goto.git
+cd goto
+sudo ./install
+```
 
-For example, if you placed the file in your home folder, all you have to do is add the following line to your `.bashrc` file:
+### Manually
+Copy the file `goto.sh` somewhere in your filesystem and add a line in your `.zshrc` or `.bashrc` to source it.
+
+For example, if you placed the file in your home folder, all you have to do is add the following line to your `.zshrc` or `.bashrc` file:
 
 ```bash
-source ~/goto.bash
+source ~/goto.sh
 ```
 
 ## Usage
@@ -98,7 +107,7 @@ goto --register blog /mnt/external/projects/html/blog
 goto -r last_release .
 ```
 and it will automatically be aliased to the whole path.
-* Pressing the `tab` key after the alias name, you have the default directory suggestions by bash.
+* Pressing the `tab` key after the alias name, you have the default directory suggestions by the shell.
 
 ### Unregister an alias
 
@@ -134,6 +143,26 @@ or
 goto --list
 ```
 
+### Expand an alias
+
+To expand an alias to its value, use:
+```bash
+goto -x <alias>
+```
+or
+```bash
+goto --expand <alias>
+```
+
+#### Example
+```bash
+goto -x last_release
+```
+or
+```bash
+goto --expand last_release
+```
+
 ### Cleanup
 
 To cleanup the aliases from directories that are no longer accessible in your filesystem, use:
@@ -171,7 +200,6 @@ goto --version
 ## TODO
 
 * ~~Test on macOS~~ extensively
-* Fix `zsh` issues [[#7](https://github.com/iridakos/goto/issues/7), ...]
 * Write [tests](https://github.com/iridakos/goto/issues/2)
 
 ## Contributing
diff --git a/goto.bash b/goto.sh
similarity index 63%
rename from goto.bash
rename to goto.sh
index aeceb2a..2ca533b 100644
--- a/goto.bash
+++ b/goto.sh
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+#!/usr/bin/env sh
+# shellcheck disable=SC2039
 # MIT License
 #
 # Copyright (c) 2018 Lazarus Lazaridis
@@ -23,9 +24,10 @@
 
 # Changes to the given alias directory
 # or executes a command based on the arguments.
-function goto()
+goto()
 {
   local target
+  _goto_resolve_db
 
   if [ -z "$1" ]; then
     # display usage and exit when no args
@@ -54,6 +56,9 @@ function goto()
     -l|--list)
       _goto_list_aliases
       ;;
+    -x|--expand) # Expand an alias
+      _goto_expand_alias "$@"
+      ;;
     -h|--help)
       _goto_usage
       ;;
@@ -64,9 +69,15 @@ function goto()
       _goto_directory "$subcommand"
       ;;
   esac
+  return $?
 }
 
-function _goto_usage()
+_goto_resolve_db()
+{
+  GOTO_DB="$HOME/.goto"
+}
+
+_goto_usage()
 {
   cat <<\USAGE
 usage: goto [<option>] <alias> [<directory>]
@@ -85,6 +96,8 @@ OPTIONS:
     goto -o|--pop
   -l, --list: lists aliases
     goto -l|--list
+  -x, --expand: expands an alias
+    goto -x|--expand <alias>
   -c, --cleanup: cleans up non existent directory aliases
     goto -c|--cleanup
   -h, --help: prints this help
@@ -95,40 +108,68 @@ USAGE
 }
 
 # Displays version
-function _goto_version()
+_goto_version()
 {
   echo "goto version 1.0.0"
 }
 
 # Expands directory.
 # Helpful for ~, ., .. paths
-function _goto_expand_directory()
+_goto_expand_directory()
 {
   cd "$1" 2>/dev/null && pwd
 }
 
 # Lists registered aliases.
-function _goto_list_aliases()
+_goto_list_aliases()
 {
   local IFS=$'\n'
-  if [ -f ~/.goto ]; then
-    sed '/^\s*$/d' ~/.goto 2>/dev/null
+  if [ -f "$GOTO_DB" ]; then
+    sed '/^\s*$/d' "$GOTO_DB" 2>/dev/null
   else
     echo "You haven't configured any directory aliases yet."
   fi
 }
 
+# Expands a registered alias.
+_goto_expand_alias()
+{
+  if [ "$#" -ne "1" ]; then
+    _goto_error "usage: goto -x|--expand <alias>"
+    return
+  fi
+
+  local resolved
+
+  resolved=$(_goto_find_alias_directory "$1")
+  if [ -z "$resolved" ]; then
+    _goto_error "alias '$1' does not exist"
+    return
+  fi
+
+  echo "$resolved"
+}
+
+# Lists duplicate directory aliases
+_goto_find_duplicate()
+{
+  local duplicates=
+
+  duplicates=$(sed -n 's:[^ ]* '"$1"'$:&:p' "$GOTO_DB" 2>/dev/null)
+  echo "$duplicates"
+}
+
 # Registers and alias.
-function _goto_register_alias()
+_goto_register_alias()
 {
   if [ "$#" -ne "2" ]; then
     _goto_error "usage: goto -r|--register <alias> <directory>"
-    return
+    return 1
   fi
 
   if ! [[ $1 =~ ^[[:alnum:]]+[a-zA-Z0-9_-]*$ ]]; then
     _goto_error "invalid alias - can start with letters or digits followed by letters, digits, hyphens or underscores"
-    return
+    return 1
   fi
 
   local resolved
@@ -136,38 +177,46 @@ function _goto_register_alias()
 
   if [ -n "$resolved" ]; then
     _goto_error "alias '$1' exists"
-    return
+    return 1
   fi
 
   local directory
   directory=$(_goto_expand_directory "$2")
   if [ -z "$directory" ]; then
     _goto_error "failed to register '$1' to '$2' - can't cd to directory"
-    return
+    return 1
+  fi
+
+  local duplicate
+  duplicate=$(_goto_find_duplicate "$directory")
+  if [ -n "$duplicate" ]; then
+    _goto_warning "duplicate alias(es) found: \\n$duplicate"
   fi
 
   # Append entry to file.
-  echo "$1 $directory" >> ~/.goto
+  echo "$1 $directory" >> "$GOTO_DB"
   echo "Alias '$1' registered successfully."
 }
 
 # Unregisters the given alias.
-function _goto_unregister_alias
+_goto_unregister_alias()
 {
   if [ "$#" -ne "1" ]; then
     _goto_error "usage: goto -u|--unregister <alias>"
-    return
+    return 1
   fi
 
   local resolved
   resolved=$(_goto_find_alias_directory "$1")
   if [ -z "$resolved" ]; then
     _goto_error "alias '$1' does not exist"
-    return
+    return 1
   fi
 
+  # shellcheck disable=SC2034
+  local readonly GOTO_DB_TMP="$HOME/.goto_"
   # Delete entry from file.
-  sed "/^$1 /d" ~/.goto > ~/.goto_ && mv ~/.goto_ ~/.goto
+  sed "/^$1 /d" "$GOTO_DB" > "$GOTO_DB_TMP" && mv "$GOTO_DB_TMP" "$GOTO_DB"
   echo "Alias '$1' unregistered successfully."
 }
 
@@ -191,60 +240,67 @@ function _goto_directory_pop()
 }
 
 # Unregisters aliases whose directories no longer exist.
-function _goto_cleanup()
+_goto_cleanup()
 {
-  if ! [ -f ~/.goto ]; then
+  if ! [ -f "$GOTO_DB" ]; then
     return
   fi
 
-  local IFS=$'\n' match matches al dir
-
-  read -d '' -r -a matches < ~/.goto
-
-  IFS=' '
-  for i in "${!matches[@]}"; do
-    read -r -a match <<< "${matches[$i]}"
-
-    al="${match[0]}"
-    dir="${match[*]:1}"
-
-    if [ -n "$al" ] && [ ! -d "$dir" ]; then
-      echo "Cleaning up: $al - $dir"
-      _goto_unregister_alias "$al"
-    fi
-  done
+  while IFS= read -r i && [ -n "$i" ]; do
+    echo "Cleaning up: $i"
+    _goto_unregister_alias "$i"
+  done <<< "$(awk '{al=$1; $1=""; dir=substr($0,2);
+                    system("[ ! -d \"" dir "\" ] && echo " al)}' "$GOTO_DB")"
 }
 
 # Changes to the given alias' directory
-function _goto_directory()
+_goto_directory()
 {
   local target
 
-  target=$(_goto_resolve_alias "$1")
+  target=$(_goto_resolve_alias "$1") || return 1
 
-  if [ -n "$target" ]; then
-    cd "$target" || _goto_error "Failed to goto '$target'"
-  fi
+  cd "$target" 2> /dev/null || \
+    { _goto_error "Failed to goto '$target'" && return 1; }
 }
 
 # Fetches the alias directory.
-function _goto_find_alias_directory()
+_goto_find_alias_directory()
 {
   local resolved
 
-  resolved=$(sed -n "s/^$1 \\(.*\\)/\\1/p" ~/.goto 2>/dev/null)
+  resolved=$(sed -n "s/^$1 \\(.*\\)/\\1/p" "$GOTO_DB" 2>/dev/null)
   echo "$resolved"
 }
 
 # Displays the given error.
 # Used for common error output.
-function _goto_error()
+_goto_error()
 {
-  (>&2 echo "goto error: $1")
+  (>&2 echo -e "goto error: $1")
+}
+
+# Displays the given warning.
+# Used for common warning output.
+_goto_warning()
+{
+  (>&2 echo -e "goto warning: $1")
+}
+
+# Displays entries with aliases starting as the given one.
+_goto_print_similar()
+{
+  local similar
+
+  similar=$(sed -n "/^$1[^ ]* .*/p" "$GOTO_DB" 2>/dev/null)
+  if [ -n "$similar" ]; then
+    (>&2 echo "Did you mean:")
+    (>&2 echo "$similar" | column -t)
+  fi
 }
 
 # Fetches alias directory, errors if it doesn't exist.
-function _goto_resolve_alias()
+_goto_resolve_alias()
 {
   local resolved
 
@@ -252,28 +308,30 @@ function _goto_resolve_alias()
 
   if [ -z "$resolved" ]; then
     _goto_error "unregistered alias $1"
-    echo ""
+    _goto_print_similar "$1"
+    return 1
   else
     echo "${resolved}"
   fi
 }
 
 # Completes the goto function with the available commands
-function _complete_goto_commands()
+_complete_goto_commands()
 {
   local IFS=$' \t\n'
 
   # shellcheck disable=SC2207
-  COMPREPLY=($(compgen -W "-r --register -u --unregister -p --push -o --pop -l --list -c --cleanup -v --version" -- "$1"))
+  COMPREPLY=($(compgen -W "-r --register -u --unregister -p --push -o --pop -l --list -x --expand -c --cleanup -v --version" -- "$1"))
 }
 
 # Completes the goto function with the available aliases
-function _complete_goto_aliases()
+_complete_goto_aliases()
 {
-  local IFS=$'\n' matches al
+  local IFS=$'\n' matches
+  _goto_resolve_db
 
   # shellcheck disable=SC2207
-  matches=($(sed -n "/^$1/p" ~/.goto 2>/dev/null))
+  matches=($(sed -n "/^$1/p" "$GOTO_DB" 2>/dev/null))
 
   if [ "${#matches[@]}" -eq "1" ]; then
     # remove the filenames attribute from the completion method
@@ -298,7 +356,7 @@ function _complete_goto_aliases()
 }
 
 # Bash programmable completion for the goto function
-function _complete_goto()
+_complete_goto_bash()
 {
   local cur="${COMP_WORDS[$COMP_CWORD]}" prev
 
@@ -316,7 +374,10 @@ function _complete_goto()
     prev="${COMP_WORDS[1]}"
 
     if [[ $prev = "-u" ]] || [[ $prev = "--unregister" ]]; then
-      # prompt with aliases only if user tries to unregister one
+      # prompt with aliases if user tries to unregister one
+      _complete_goto_aliases "$cur"
+    elif [[ $prev = "-x" ]] || [[ $prev = "--expand" ]]; then
+      # prompt with aliases if user tries to expand one
       _complete_goto_aliases "$cur"
     elif [[ $prev = "-p" ]] || [[ $prev = "--push" ]]; then
       # prompt with aliases only if user tries to push
@@ -336,9 +397,51 @@ function _complete_goto()
   fi
 }
 
-# Register the goto compspec
-if ! [[ $(uname -s) =~ Darwin* ]]; then
-  complete -o filenames -F _complete_goto goto
+# Zsh programmable completion for the goto function
+_complete_goto_zsh()
+{
+  local all_aliases=()
+  while IFS= read -r line; do
+    all_aliases+=("$line")
+  done <<< "$(sed -e 's/ /:/g' ~/.goto 2>/dev/null)"
+
+  local state
+  local -a options=(
+    '(1)'{-r,--register}'[registers an alias]:register:->register'
+    '(- 1 2)'{-u,--unregister}'[unregisters an alias]:unregister:->unregister'
+    '(: -)'{-l,--list}'[lists aliases]'
+    '(*)'{-c,--cleanup}'[cleans up non existent directory aliases]'
+    '(: -)'{-h,--help}'[prints this help]'
+    '(* -)'{-v,--version}'[displays the version of the goto script]'
+  )
+
+  _arguments -C \
+    "${options[@]}" \
+    '1:alias:->aliases' \
+    '2:dir:_files' \
+  && ret=0
+
+  case ${state} in
+    (aliases)
+      _describe -t aliases 'goto aliases:' all_aliases && ret=0
+    ;;
+    (unregister)
+      _describe -t aliases 'unregister alias:' all_aliases && ret=0
+    ;;
+  esac
+  return $ret
+}
+
+# Register the goto completions.
+if [ -n "${BASH_VERSION}" ]; then
+  if ! [[ $(uname -s) =~ Darwin* ]]; then
+    complete -o filenames -F _complete_goto_bash goto
+  else
+    complete -F _complete_goto_bash goto
+  fi
+elif [ -n "${ZSH_VERSION}" ]; then
+  compdef _complete_goto_zsh goto
 else
-  complete -F _complete_goto goto
+  echo "Unsupported shell."
+  exit 1
 fi
diff --git a/install b/install
new file mode 100755
index 0000000..e75ad5c
--- /dev/null
+++ b/install
@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+# MIT License
+#
+# Copyright (c) 2018 Lazarus Lazaridis
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+function _goto_install_error()
+{
+	echo "$@" >&2
+}
+
+# sudo-check
+if [ $EUID -ne 0 ]; then
+	_goto_install_error 'Please run this script in sudo mode or as root user'
+	exit
+fi
+
+GOTO_FILE_LOCATION='/usr/local/share/goto.sh'
+RC=""
+if [ -f ~/.bashrc ]; then
+	RC="$HOME/.bashrc"
+elif [ -f ~/.cshrc ]; then
+	RC="$HOME/.cshrc"
+elif [ -f ~/.kshrc ]; then
+	RC="$HOME/.kshrc"
+elif [ -f ~/.zshrc ]; then
+	RC="$HOME/.zshrc"
+fi
+
+cp ./goto.sh "$GOTO_FILE_LOCATION"
+
+if [ -n "$RC" ]; then
+	# Append source to RC startup file if not already there
+	if [ "$(grep -c "source $GOTO_FILE_LOCATION" "$RC")" == "0" ]; then
+		# Append source to RC file
+		echo -e "\\n\\n# Source goto\\n[[ -s \"$GOTO_FILE_LOCATION\" ]] && source $GOTO_FILE_LOCATION\\n" >> "$RC"
+	fi
+
+	# shellcheck source=/dev/null
+	source "$GOTO_FILE_LOCATION"
+else
+	_goto_install_error "Error sourcing goto in your startup file.."
+	_goto_install_error "E.g ~/.bashrc ~/.cshrc etc.."
+fi