diff --git a/install_and_cache_pkgs.sh b/install_and_cache_pkgs.sh
index e4f6c2c..f3cdfe5 100755
--- a/install_and_cache_pkgs.sh
+++ b/install_and_cache_pkgs.sh
@@ -8,7 +8,7 @@ script_dir="$(dirname -- "$(realpath -- "${0}")")"
 source "${script_dir}/lib.sh"
 
 # Directory that holds the cached packages.
-cache_dir=$1
+cache_dir="${1}"
 
 # List of the packages to use.
 input_packages="${@:2}"
diff --git a/lib.sh b/lib.sh
old mode 100644
new mode 100755
index 3802483..2a31aac
--- a/lib.sh
+++ b/lib.sh
@@ -17,7 +17,3 @@ function get_package_name_ver {
   fi
   echo 'package_name="${name}"; package_ver="${ver}"'
 }
-
-function blah {
-  > /dev/null 2>&1
-}
\ No newline at end of file
diff --git a/post_cache_action.sh b/post_cache_action.sh
index 5503013..56fda54 100755
--- a/post_cache_action.sh
+++ b/post_cache_action.sh
@@ -4,23 +4,23 @@
 set -e
 
 # Directory that holds the cached packages.
-cache_dir=$1
+cache_dir="${1}"
 
 # Root directory to untar the cached packages to.
 # Typically filesystem root '/' but can be changed for testing.
-cache_restore_root=$2
+cache_restore_root="${2}"
 
 # Indicates that the cache was found.
-cache_hit=$3
+cache_hit="${3}"
 
 # List of the packages to use.
 packages="${@:4}"
 
-script_dir=$(dirname $0)
+script_dir="$(dirname -- "$(realpath -- "${0}")")"
 
 if [ "$cache_hit" == true ]; then
-  $script_dir/restore_pkgs.sh ~/cache-apt-pkgs $cache_restore_root
+  ${script_dir}/restore_pkgs.sh ~/cache-apt-pkgs ${cache_restore_root}
 else
-  $script_dir/install_and_cache_pkgs.sh ~/cache-apt-pkgs $packages
+  ${script_dir}/install_and_cache_pkgs.sh ~/cache-apt-pkgs ${packages}
 fi
 echo ""
diff --git a/pre_cache_action.sh b/pre_cache_action.sh
index 05d2fbe..4bd63d4 100755
--- a/pre_cache_action.sh
+++ b/pre_cache_action.sh
@@ -5,10 +5,10 @@ script_dir="$(dirname -- "$(realpath -- "${0}")")"
 source "${script_dir}/lib.sh"
 
 # Directory that holds the cached packages.
-cache_dir=$1
+cache_dir=${1}
 
 # Version of the cache to create or load.
-version=$2
+version=${2}
 
 # List of the packages to use.
 input_packages="${@:3}"
@@ -17,12 +17,12 @@ input_packages="${@:3}"
 packages="$(normalize_package_list "${input_packages}")"
 
 # Create cache directory so artifacts can be saved.
-mkdir -p $cache_dir
+mkdir -p ${cache_dir}
 
-echo -n "Validating action arguments (version='$version', packages='$packages')...";
+echo -n "Validating action arguments (version='${version}', packages='${packages}')...";
 if grep -q " " <<< "${cache_version}"; then
   echo "aborted." 
-  echo "Version value '$version' cannot contain spaces." >&2
+  echo "Version value '${version}' cannot contain spaces." >&2
   exit 1
 fi
 
@@ -39,7 +39,7 @@ echo -n "Verifying packages..."
 for package in ${packages}; do 
   if test ! "$(apt show "${package}")"; then
     echo "aborted."
-    echo "Package '$package' not found." >&2
+    echo "Package '${package}' not found." >&2
     exit 3
   fi
   get_package_name_ver "${package}" # -> package_name, package_ver  
@@ -64,6 +64,6 @@ echo "- Value hashed as '${key}'."
 
 echo "done."
 
-key_filepath="$cache_dir/cache_key.md5"
-echo $key > $key_filepath
-echo "Hash value written to $key_filepath"
+key_filepath="${cache_dir}/cache_key.md5"
+echo ${key} > ${key_filepath}
+echo "Hash value written to ${key_filepath}"
diff --git a/restore_pkgs.sh b/restore_pkgs.sh
index 4c710f3..3cee703 100755
--- a/restore_pkgs.sh
+++ b/restore_pkgs.sh
@@ -4,16 +4,16 @@
 set -e
 
 # Directory that holds the cached packages.
-cache_dir=$1
+cache_dir="${1}"
 
 # Root directory to untar the cached packages to.
 # Typically filesystem root '/' but can be changed for testing.
-cache_restore_root=$2
+cache_restore_root="${2}"
 
-cache_filepaths=$(ls -1 $cache_dir | sort)
-echo "Found $(echo $cache_filepaths | wc -w) files in the cache."
-for cache_filepath in $cache_filepaths; do
-  echo "- $(basename $cache_filepath)"
+cache_filepaths=$(ls -1 ${cache_dir} | sort)
+echo "Found $(echo ${cache_filepaths} | wc -w) files in the cache."
+for cache_filepath in ${cache_filepaths}; do
+  echo "- $(basename ${cache_filepath})"
 done
 
 echo "Reading from manifest..."
@@ -23,12 +23,12 @@ done
 echo "done."
 
 # Only search for archived results. Manifest and cache key also live here.
-cache_pkg_filepaths=$(ls -1 $cache_dir/*.tar.gz | sort)
-cache_pkg_filecount=$(echo $cache_pkg_filepaths | wc -w)
-echo "Restoring $cache_pkg_filecount packages from cache..."
-for cache_pkg_filepath in $cache_pkg_filepaths; do
-  echo -n "- $(basename $cache_pkg_filepath) restoring..."
-  sudo tar -xf $cache_pkg_filepath -C $cache_restore_root > /dev/null
+cache_pkg_filepaths=$(ls -1 ${cache_dir}/*.tar.gz | sort)
+cache_pkg_filecount=$(echo ${cache_pkg_filepaths} | wc -w)
+echo "Restoring ${cache_pkg_filecount} packages from cache..."
+for cache_pkg_filepath in ${cache_pkg_filepaths}; do
+  echo -n "- $(basename ${cache_pkg_filepath}) restoring..."
+  sudo tar -xf ${cache_pkg_filepath} -C ${cache_restore_root} > /dev/null
   echo "done."
 done
 echo "done."