diff --git a/bin/install-etcd-system b/bin/install-etcd-system
index a4b8175..a4b78c5 100755
--- a/bin/install-etcd-system
+++ b/bin/install-etcd-system
@@ -19,7 +19,7 @@ if [[ $OSTYPE =~ linux ]]; then
 elif [[  $OSTYPE =~ darwin ]]; then
     OS=darwin
 else
-    echo unknown os: $OSTYPE
+    echo unknown os: "$OSTYPE"
     exit 1
 fi
 
@@ -27,37 +27,38 @@ ARCH=
 if [[ $(uname -m) == x86_64 ]]; then
     ARCH=amd64
 else
-    echo arch not yet supported: $(uname -m)
+    echo arch not yet supported: "$(uname -m)"
     exit 1
 fi
 URL=https://github.com/etcd-io/etcd/releases/download/${VERSION}/etcd-${VERSION}-${OS}-${ARCH}.tar.gz
 
-[[ -d ${APP_DEST_DIR} ]] || sudo mkdir -p ${APP_DEST_DIR}
+[[ -d ${APP_DEST_DIR} ]] || sudo mkdir -p "${APP_DEST_DIR}"
 
 TMP_DIR=
 if [[ ! -d ${APP_DEST_DIR}/bin ]]; then
     TMP_DIR=$(mktemp --directory)
     DEST_FILE=$TMP_DIR/${APP}.tar.gz
-    echo downloading ${APP} ${VERSION} to temp directory ${TMP_DIR}
-    curl --silent --location --output ${DEST_FILE} ${URL}
+    echo downloading "${APP}" "${VERSION}" to temp directory "${TMP_DIR}"
+    curl --silent --location --output "${DEST_FILE}" "${URL}"
 
-    sudo tar xf ${DEST_FILE} --directory ${APP_DEST_DIR} --strip-components 1
-    sudo chown --recursive root:root ${APP_DEST_DIR}
+    sudo tar xf "${DEST_FILE}" --directory "${APP_DEST_DIR}" --strip-components 1
+    sudo chown --recursive root:root "${APP_DEST_DIR}"
 else
-    echo ${APP} ${VERSION} already installed
+    echo "${APP}" "${VERSION}" already installed
 fi
 
 cd ${APP_PREFIX_DIR}
 [[ -s current ]] && sudo unlink current
-sudo ln --symbolic ${APP_DEST_DIR} current
-echo current version set to ${VERSION}
+sudo ln --symbolic "${APP_DEST_DIR}" current
+echo current version set to "${VERSION}"
 
 cd ${BIN_DIR}
+# shellcheck disable=SC2044
 for bin in $(find ${APP_CURRENT}/ -maxdepth 1 -executable -type f -exec basename {} \;); do
-    [[ -s $bin ]] || sudo ln --symbolic ${APP_CURRENT}/$bin
+    [[ -s $bin ]] || sudo ln --symbolic "${APP_CURRENT}/$bin"
 done
 
 if [[ $TMP_DIR != "" ]]; then
-    rm -rf ${TMP_DIR}
-    echo removed up temp directory ${TMP_DIR}
+    rm -rf "${TMP_DIR}"
+    echo removed up temp directory "${TMP_DIR}"
 fi
diff --git a/bin/install-go-system b/bin/install-go-system
index 1e1c170..0f49b71 100755
--- a/bin/install-go-system
+++ b/bin/install-go-system
@@ -9,7 +9,6 @@ PREFIX_DIR=/usr/local
 
 GO_PREFIX_DIR=${PREFIX_DIR}/golang
 GO_DEST_DIR=${GO_PREFIX_DIR}/${GO_VERSION}
-GO_CURRENT=${PREFIX_DIR}/go
 
 OS=
 if [[ $OSTYPE =~ linux ]]; then
@@ -17,7 +16,7 @@ if [[ $OSTYPE =~ linux ]]; then
 elif [[  $OSTYPE =~ darwin ]]; then
     OS=darwin
 else
-    echo unknown os: $OSTYPE
+    echo unknown os: "$OSTYPE"
     exit 1
 fi
 
@@ -25,36 +24,36 @@ ARCH=
 if [[ $(uname -m) == x86_64 ]]; then
     ARCH=amd64
 else
-    echo arch not yet supported: $(uname -m)
+    echo arch not yet supported: "$(uname -m)"
     exit 1
 fi
 
-[[ -d ${GO_DEST_DIR} ]] || sudo mkdir -p ${GO_DEST_DIR}
+[[ -d ${GO_DEST_DIR} ]] || sudo mkdir -p "${GO_DEST_DIR}"
 
 TMP_DIR=
 if [[ ! -d ${GO_DEST_DIR}/bin ]]; then
     TMP_DIR=$(mktemp --directory)
     DEST_FILE=$TMP_DIR/go.tar.gz
     URL=https://dl.google.com/go/go${GO_VERSION}.${OS}-${ARCH}.tar.gz
-    echo downloading go $GO_VERSION to temp directory ${TMP_DIR}
-    curl --silent --output ${DEST_FILE} ${URL}
+    echo downloading go "$GO_VERSION" to temp directory "${TMP_DIR}"
+    curl --silent --output "${DEST_FILE}" "${URL}"
 
-    sudo tar xf ${DEST_FILE} --directory ${GO_DEST_DIR} --strip-components 1
-    sudo chown --recursive root:root ${GO_DEST_DIR}
+    sudo tar xf "${DEST_FILE}" --directory "${GO_DEST_DIR}" --strip-components 1
+    sudo chown --recursive root:root "${GO_DEST_DIR}"
 else
-    echo go $GO_VERSION already installed
+    echo go "$GO_VERSION" already installed
 fi
 
 cd ${PREFIX_DIR}
 [[ -s go ]] && sudo unlink go
-sudo ln --symbolic ${GO_DEST_DIR} go
-echo current version set to ${GO_VERSION}
+sudo ln --symbolic "${GO_DEST_DIR}" go
+echo current version set to "${GO_VERSION}"
 
 [[ -f /etc/profile.d/go-path.sh ]] \
-    || echo 'export PATH=$PATH:/usr/local/go/bin' \
+    || echo "export PATH=\$PATH:/usr/local/go/bin" \
     | sudo tee /etc/profile.d/go-path.sh
 
 if [[ $TMP_DIR != "" ]]; then
-    rm -rf ${TMP_DIR}
-    echo removed up temp directory ${TMP_DIR}
+    rm -rf "${TMP_DIR}"
+    echo removed up temp directory "${TMP_DIR}"
 fi
diff --git a/bin/install-minikube-system b/bin/install-minikube-system
index 9c8e2f2..be12382 100755
--- a/bin/install-minikube-system
+++ b/bin/install-minikube-system
@@ -16,7 +16,7 @@ if [[ $(uname) =~ Linux ]]; then
 elif [[  $(uname) =~ Darwin ]]; then
     OS=darwin
 else
-    echo unsupported os: $(uname)
+    echo "unsupported os: $(uname)"
     exit 1
 fi
 
@@ -24,34 +24,34 @@ ARCH=
 if [[ $(uname -m) == x86_64 ]]; then
     ARCH=amd64
 else
-    echo arch not yet supported: $(uname -m)
+    echo arch not yet supported: "$(uname -m)"
     exit 1
 fi
 
 TMP_DIR=
 if [[ ! -d ${MINIKUBE_DEST_DIR} ]]; then
-    sudo mkdir -p ${MINIKUBE_DEST_DIR}
+    sudo mkdir -p "${MINIKUBE_DEST_DIR}"
     TMP_DIR=$(mktemp --directory)
-    DEST_FILE=${TMP_DIR}/minikube
-    URL=https://github.com/kubernetes/minikube/releases/download/${MINIKUBE_VERSION}/minikube-${OS}-${ARCH}
-    echo downloading minikube ${MINIKUBE_VERSION} to temp directory ${TMP_DIR}
-    curl --silent --location --output ${DEST_FILE} ${URL}
-
-    sudo chmod 755 ${DEST_FILE}
-    sudo mv ${DEST_FILE} ${MINIKUBE_DEST_DIR}
-    sudo chown --recursive root:root ${MINIKUBE_DEST_DIR}
+    DEST_FILE="${TMP_DIR}"/minikube
+    URL="https://github.com/kubernetes/minikube/releases/download/${MINIKUBE_VERSION}/minikube-${OS}-${ARCH}"
+    echo downloading minikube "${MINIKUBE_VERSION}" to temp directory "${TMP_DIR}"
+    curl --silent --location --output "${DEST_FILE}" "${URL}"
+
+    sudo chmod 755 "${DEST_FILE}"
+    sudo mv "${DEST_FILE}" "${MINIKUBE_DEST_DIR}"
+    sudo chown --recursive root:root "${MINIKUBE_DEST_DIR}"
 else
-    echo minikube ${MINIKUBE_VERSION} already installed
+    echo minikube "${MINIKUBE_VERSION}" already installed
 fi
 
-cd ${MINIKUBE_PREFIX_DIR}
+cd "${MINIKUBE_PREFIX_DIR}"
 [[ -s current ]] && sudo unlink current
-sudo ln --symbolic ${MINIKUBE_VERSION}/ current
-echo current version set to ${MINIKUBE_VERSION}
+sudo ln --symbolic "${MINIKUBE_VERSION}"/ current
+echo current version set to "${MINIKUBE_VERSION}"
 cd ${BIN_DIR}
 [[ -L ${BIN_DIR}/minikube ]] || sudo ln --symbolic ${MINIKUBE_CURRENT}/minikube
 
 if [[ $TMP_DIR != "" ]]; then
-    rm -rf ${TMP_DIR}
-    echo removed up temp directory ${TMP_DIR}
+    rm -rf "${TMP_DIR}"
+    echo removed up temp directory "${TMP_DIR}"
 fi
diff --git a/bin/install-node-system b/bin/install-node-system
index f36f284..b3310af 100755
--- a/bin/install-node-system
+++ b/bin/install-node-system
@@ -18,7 +18,7 @@ if [[ $OSTYPE =~ linux ]]; then
 elif [[  $OSTYPE =~ darwin ]]; then
     OS=darwin
 else
-    echo unknown os: $OSTYPE
+    echo unknown os: "$OSTYPE"
     exit 1
 fi
 
@@ -26,36 +26,36 @@ ARCH=
 if [[ $(uname -m) == x86_64 ]]; then
     ARCH=x64
 else
-    echo arch not yet supported: $(uname -m)
+    echo arch not yet supported: "$(uname -m)"
     exit 1
 fi
 
-[[ -d ${NODE_DEST_DIR} ]] || sudo mkdir -p ${NODE_DEST_DIR}
+[[ -d "${NODE_DEST_DIR}" ]] || sudo mkdir -p "${NODE_DEST_DIR}"
 
 TMP_DIR=
 if [[ ! -d ${NODE_DEST_BIN_DIR} ]]; then
     TMP_DIR=$(mktemp --directory)
     DEST_FILE=$TMP_DIR/node.tar.xz
     URL=https://nodejs.org/dist/${NODE_VERSION}/node-${NODE_VERSION}-${OS}-${ARCH}.tar.xz
-    echo downloading node $NODE_VERSION to temp directory ${TMP_DIR}
-    curl --silent --output ${DEST_FILE} ${URL}
+    echo downloading node "$NODE_VERSION" to temp directory "${TMP_DIR}"
+    curl --silent --output "${DEST_FILE}" "${URL}"
 
-    sudo tar xf ${DEST_FILE} --directory ${NODE_DEST_DIR} --strip-components 1
-    sudo chown --recursive root:root ${NODE_DEST_DIR}
+    sudo tar xf "${DEST_FILE}" --directory "${NODE_DEST_DIR}" --strip-components 1
+    sudo chown --recursive root:root "${NODE_DEST_DIR}"
 else
-    echo node $NODE_VERSION already installed
+    echo node "$NODE_VERSION" already installed
 fi
 
 cd ${NODE_PREFIX_DIR}
 [[ -s current ]] && sudo unlink current
-sudo ln --symbolic ${NODE_VERSION} current
-echo current version set to ${NODE_VERSION}
+sudo ln --symbolic "${NODE_VERSION}" current
+echo current version set to "${NODE_VERSION}"
 cd ${BIN_DIR}
-for bin in $(ls ${NODE_CURRENT}/bin); do
-    [[ -s $bin ]] || sudo ln --symbolic ${NODE_CURRENT}/bin/$bin
+for bin in "${NODE_CURRENT}/bin/"*; do
+    [[ -s $bin ]] || sudo ln --symbolic "${NODE_CURRENT}/bin/$bin"
 done
 
 if [[ $TMP_DIR != "" ]]; then
-    rm -rf ${TMP_DIR}
-    echo removed up temp directory ${TMP_DIR}
+    rm -rf "${TMP_DIR}"
+    echo removed up temp directory "${TMP_DIR}"
 fi
diff --git a/bin/install-protoc b/bin/install-protoc
index 4ea4b23..eebfd02 100755
--- a/bin/install-protoc
+++ b/bin/install-protoc
@@ -8,7 +8,7 @@ PROTOC_ZIP=protoc-$PROTOC_VERSION-linux-x86_64.zip
 TMP_DIR=$(mktemp --directory)
 DEST_FILE=$TMP_DIR/$PROTOC_ZIP
 URL=https://github.com/protocolbuffers/protobuf/releases/download/v$PROTOC_VERSION/$PROTOC_ZIP
-curl --output "$DEST_FILE" --location $URL
+curl --output "$DEST_FILE" --location "$URL"
 sudo unzip -o "$DEST_FILE" -d /usr/local bin/protoc
 sudo unzip -o "$DEST_FILE" -d /usr/local 'include/*'
 rm -rfv "$TMP_DIR"
diff --git a/bin/snow b/bin/snow
index 1f2d676..2e06fcb 100755
--- a/bin/snow
+++ b/bin/snow
@@ -15,11 +15,11 @@ function move_flake() {
         snowflakes[$i]=0
     else
         if [ "${lastflakes[$i]}" != "" ]; then
-            printf "\033[%s;%sH \033[0;0H " ${lastflakes[$i]} $i
+            printf "\033[%s;%sH \033[0;0H " "${lastflakes[$i]}" "$i"
         fi
     fi
 
-    printf "\033[%s;%sH❄\033[0;0H" ${snowflakes[$i]} $i
+    printf "\033[%s;%sH❄\033[0;0H" "${snowflakes[$i]}" "$i"
 
     lastflakes[$i]=${snowflakes[$i]}
     snowflakes[$i]=$((${snowflakes[$i]}+1))
@@ -27,7 +27,7 @@ function move_flake() {
 
 while :
 do
-    i=$(($RANDOM % $COLUMNS))
+    i=$((RANDOM % COLUMNS))
 
     move_flake $i