diff --git a/install.sh b/install.sh
index 2fa1449..0fb33da 100755
--- a/install.sh
+++ b/install.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-if [ ! -x `which zsh` ]; then
+if [ ! -x "$(which zsh)" ]; then
 	exit
 fi
 
@@ -10,10 +10,10 @@ ln -s ~/.dotfiles/tmux/tmux.conf ~/.tmux.conf
 mkdir ~/.dotfiles/this-machine
 touch ~/.dotfiles/this-machine/zsh
 touch ~/.dotfiles/this-machine/tmux.conf
-sudo chsh -s $(which zsh) $USER
+sudo chsh -s '$(which zsh)' "$USER"
 
 # If private repo is available, add ssh config + hosts
-if [ -d $HOME/.jan ]; then
+if [ -d "$HOME/.jan" ]; then
     echo "Include ~/.dotfiles/ssh/settings" >> ~/.ssh/config
     echo "Include ~/.jan/ssh_hosts" >> ~/.ssh/config
     chmod 600 ~/.ssh/config
diff --git a/zsh/alias b/zsh/alias
index f8dc1bb..1ffce7b 100644
--- a/zsh/alias
+++ b/zsh/alias
@@ -5,24 +5,24 @@
 # Better LS
 if [[ $platform == 'Linux' ]]; then
 	alias bls='pwd; ls -lahp --color=auto --group-directories-first'
-elif [[ $platform == 'macOS' && -x `which gls` ]]; then
+elif [[ $platform == 'macOS' && -x $(which gls) ]]; then
 	alias bls='pwd; gls -lahpG --group-directories-first'
 elif [[ $platform == 'macOS' ]]; then
 	alias bls='/bin/ls -lahG'
 fi
 
 # Better exa
-if [[ -x `which exa` ]]; then
+if [[ -x $(which exa) ]]; then
 	alias exa='pwd; exa -la --group-directories-first --git -g'
 fi
 
 # Better lsd
-if [[ -x `which lsd` ]]; then
+if [[ -x $(which lsd) ]]; then
     alias lsd='pwd; lsd -laF --group-dirs=first --icon=never'
 fi
 
 # Update aliases
-if [[ -x `which brew` ]]; then
+if [[ -x $(which brew) ]]; then
 	alias brewupdate='brew update; brew upgrade; brew upgrade --cask; brew cleanup'
 fi
 
@@ -44,9 +44,9 @@ alias a2='aria2c -x4 -c -m3'
 alias sc='screen -R'
 
 # Only download mp4 version of youtube
-if [[ -x `which yt-dlp` ]]; then
+if [[ -x $(which yt-dlp) ]]; then
         alias ytmp4='yt-dlp -f "bestvideo[ext=mp4]+bestaudio[ext=m4a]/mp4"'
-elif [[ -x `which youtube-dl` ]]; then
+elif [[ -x $(which youtube-dl) ]]; then
         alias ytmp4='youtube-dl -f "bestvideo[ext=mp4]+bestaudio[ext=m4a]/mp4"'
 fi
 
@@ -58,13 +58,13 @@ alias rrsync='rsync -avhP'
 alias bcp='rsync -avzuh --progress --partial'
 
 # generate pseudo-random hash
-alias random32="echo $(date +%s | md5sum | head -c 32)"
+alias random32='echo $(date +%s | md5sum | head -c 32)'
 
 # tar
 alias untargz='tar -xzvf'
 
 # (macOS) start Firefox Profile manager
-if test -x "/Applications/Firefox.app/Contents/MacOS/firefox-bin"; then
+if test -x '/Applications/Firefox.app/Contents/MacOS/firefox-bin'; then
 	alias firefox-pm='/Applications/Firefox.app/Contents/MacOS/firefox-bin -P'
 fi
 
diff --git a/zsh/env b/zsh/env
index af6c995..a82e920 100644
--- a/zsh/env
+++ b/zsh/env
@@ -81,7 +81,7 @@ fi
 #
 
 # TheFuck
-if [[ -x `which thefuck` ]]; then
+if [[ -x $(which thefuck) ]]; then
 	eval "$(thefuck --alias)"
 	# You can use whatever you want as an alias, like for Mondays:
 	eval "$(thefuck --alias FUCK)"
diff --git a/zsh/ffmpeg b/zsh/ffmpeg
index 82d2381..7045e6a 100644
--- a/zsh/ffmpeg
+++ b/zsh/ffmpeg
@@ -6,8 +6,8 @@
 # source: https://yohanes.gultom.me/2016/05/21/bash-script-to-batch-convert-mkv-to-mp4-linux/
 function ff-mp4() {
 	findpath=$1
-	: ${findpath:="."}
-	find "$findpath" \( -iname '*.mkv' -o -iname '*.flv' -o -iname '*.mov' \) | while read f ; do
+	: "${findpath:="."}"
+	find "$findpath" \( -iname '*.mkv' -o -iname '*.flv' -o -iname '*.mov' \) | while read -r f ; do
 	    dir=$(dirname "$f");
 	    file=$(basename "$f");
 	    # ext="${filename##*.}";
@@ -21,8 +21,8 @@ function ff-mp4() {
 # source: https://yohanes.gultom.me/2016/05/21/bash-script-to-batch-convert-mkv-to-mp4-linux/
 function ff-ac3-to-stereo() {
         findpath=$1
-        : ${findpath:="."}
-        find "$findpath" \( -iname '*.mkv' -o -iname '*.flv' -o -iname '*.mov' -o -iname '*.mp4' \) | while read f ; do
+        : "${findpath:="."}"
+        find "$findpath" \( -iname '*.mkv' -o -iname '*.flv' -o -iname '*.mov' -o -iname '*.mp4' \) | while read -r f ; do
             dir=$(dirname "$f");
             file=$(basename "$f");
             # ext="${filename##*.}";
@@ -50,8 +50,8 @@ function ff-dts() {
 ## ffmpeg wma-to-m4a
 function ff-wma-m4a() {
         findpath=$1
-        : ${findpath:="."}
-        find "$findpath" -name '*.wma' | while read f ; do
+        : "${findpath:="."}"
+        find "$findpath" -name '*.wma' | while read -r f ; do
             dir=$(dirname "$f");
             file=$(basename "$f");
             # ext="${filename##*.}";
diff --git a/zsh/scripts b/zsh/scripts
index bbf5cc2..b0edf96 100644
--- a/zsh/scripts
+++ b/zsh/scripts
@@ -9,13 +9,13 @@ function f() {
 
 # mkdir and cd
 function mkcd() {
-    mkdir -p "$@" && cd "$_";
+    mkdir -p "$@" && cd "$_" || exit;
 }
 
 # "Fake" sha256sum
-if [[ ! -x `which sha256sum` ]]; then
+if [[ ! -x $(which sha256sum) ]]; then
     function sha256sum() {
-        shasum -a256 $1
+        shasum -a256 "$1"
     }
 fi
 
@@ -25,11 +25,11 @@ function targz() {
         echo "usage: targz filename.tar.gz directory"
         return
     fi
-    if [[ ! -x `which pigz` ]]; then
-        tar -czf $1 $2
+    if [[ ! -x $(which pigz) ]]; then
+        tar -czf "$1" "$2"
 	echo "gzip"
     else
-        tar -c $2 | pigz > $1
+        tar -c "$2" | pigz > "$1"
 	echo "pigz"
     fi
 }
@@ -47,8 +47,8 @@ function pushover() {
 # png to jpg 85
 function png2web() {
         findpath=$1
-        : ${findpath:="."}
-        find "$findpath" -name '*.png' | while read f ; do
+        : "${findpath:="."}"
+        find "$findpath" -name '*.png' | while read -r f ; do
             dir=$(dirname "$f");
             file=$(basename "$f");
             name="${file%.*}";
@@ -58,7 +58,7 @@ function png2web() {
 }
 
 function jpeg1024() {
-        magick "$1" -resize '1024x1024\>' -background black -flatten TGA:- | cjpeg -targo -quality 75 -optimize -progressive -outfile $1.jpg
+        magick "$1" -resize '1024x1024\>' -background black -flatten TGA:- | cjpeg -targo -quality 75 -optimize -progressive -outfile "$1".jpg
 }
 
 # Make PDFs look like scanned
@@ -73,21 +73,21 @@ function pdf-like-scanned () {
 # Extract files
 # src: https://github.com/mawalu/dotfiles/blob/master/zsh/.zsh/functions.zsh#L21
 function extract () {
-    if [ -f $1 ] ; then
+    if [ -f "$1" ] ; then
         case $1 in
-            *.tar.bz2) tar xjf $1 ;;
-            *.tar.gz) tar xzf $1 ;;
-            *.bz2) bunzip2 $1 ;;
-            *.rar) unrar x $1 ;;
-            *.gz) gunzip $1 ;;
-            *.tar) tar xf $1 ;;
-            *.tbz2) tar xjf $1 ;;
-            *.tbz) tar xjf $1 ;;
-            *.tgz) tar xzf $1 ;;
-            *.zip) unzip $1 ;;
-            *.Z) uncompress $1;;
-            *.7z) 7z x $1 ;;
-            *) echo "'$1' cannot be extracted via ex()" ;;
+            *.tar.bz2) tar xjf "$1" ;;
+            *.tar.gz) tar xzf "$1" ;;
+            *.bz2) bunzip2 "$1" ;;
+            *.rar) unrar x "$1" ;;
+            *.gz) gunzip "$1" ;;
+            *.tar) tar xf "$1" ;;
+            *.tbz2) tar xjf "$1" ;;
+            *.tbz) tar xjf "$1" ;;
+            *.tgz) tar xzf "$1" ;;
+            *.zip) unzip "$1" ;;
+            *.Z) uncompress "$1" ;;
+            *.7z) 7z x "$1" ;;
+            *) echo "'$1' cannot be extracted via extract()" ;;
        esac
     else
         echo "'$1' is not a valid file"
diff --git a/zshrc b/zshrc
index 1e8810a..e242d2c 100644
--- a/zshrc
+++ b/zshrc
@@ -10,7 +10,7 @@ prompt_color1="#ffaf00"
 prompt_color2="#000000"
 
 # Load zsh settings
-source $HOME/.dotfiles/zsh/settings
+source "$HOME/.dotfiles/zsh/settings"
 
 # Define platform
 platform='Unknown'
@@ -41,12 +41,12 @@ elif test -f "/usr/local/bin/brew"; then
 fi
 
 # Load additional settings
-source $HOME/.dotfiles/zsh/env
-source $HOME/.dotfiles/zsh/alias
-source $HOME/.dotfiles/zsh/bindings
-source $HOME/.dotfiles/zsh/scripts
-source $HOME/.dotfiles/zsh/ffmpeg
-source $HOME/.dotfiles/this-machine/zsh
+source "$HOME/.dotfiles/zsh/env"
+source "$HOME/.dotfiles/zsh/alias"
+source "$HOME/.dotfiles/zsh/bindings"
+source "$HOME/.dotfiles/zsh/scripts"
+source "$HOME/.dotfiles/zsh/ffmpeg"
+source "$HOME/.dotfiles/this-machine/zsh"
 
 # Prompt design
 prompt="%F{$prompt_color2}%K{$prompt_color1} ▓▒░%F%B%n@%m%b%F{$prompt_color1}%K{$prompt_color2}█▓▒░%F{#ffffff}%K{$prompt_color2}%B %D{%Y-%m-%d} %D{%k:%M:%S}
@@ -54,6 +54,6 @@ prompt="%F{$prompt_color2}%K{$prompt_color1} ▓▒░%F%B%n@%m%b%F{$prompt_colo
 
 # Load private information from second repo
 if [[ -d $HOME/.jan ]]; then
-    source $HOME/.jan/credentials
-    source $HOME/.jan/zsh_options
+    source "$HOME/.jan/credentials"
+    source "$HOME/.jan/zsh_options"
 fi