More consistent $ escapes

install/00-apt.sh

@@ -11,5 +11,5 @@ update
 upgrade
 
 # Package installs
-readonly package_list=$(cat $install_dir/$package_list_file)
+readonly package_list="$(cat $install_dir/$package_list_file)"
 install -y "$package_list"

install/01-fish.sh

@@ -23,7 +23,7 @@ printf "fish is installed\n"
 fish --version
 
 # 2. fish shell is default login shell
-readonly fish_path=$(which fish)
+readonly fish_path="$(which fish)"
 if [ "$SHELL" != fish_path ]; then
 
     # Update default login shell

install/12-docker.sh

@@ -41,7 +41,8 @@ if not_installed "docker-compose"; then
     printf "Installing docker-compose...\n"
 
     # Docker-compose
-    curl -L https://github.com/docker/compose/releases/download/1.21.2/docker-compose-$(uname -s)-$(uname -m) -o /usr/local/bin/docker-compose
+    readonly docker_compose_url="https://github.com/docker/compose/releases/download/1.21.2/docker-compose-$(uname -s)-$(uname -m)"
+    curl -L docker_compose_url -o /usr/local/bin/docker-compose
     sudo chmod +x /usr/local/bin/docker-compose
 
 fi
@@ -56,7 +57,7 @@ fi
 printf "group '$docker_group' is created\n"
 
 # 4. user is in docker group
-if ! groups $USER | grep -q "\b$docker_group\b"; then
+if ! groups "$USER" | grep -q "\b$docker_group\b"; then
     sudo usermod -aG docker "$USER"
 fi
 printf "user '$USER' is in '$docker_group' group\n"