diff --git a/cd.sh b/cd.sh
index 465a525..c863cda 100644
--- a/cd.sh
+++ b/cd.sh
@@ -1,11 +1,11 @@
 #! /usr/bin/env sh
 
-set 'cd' 'rwx'
+set "cd" "rwx"
 
 cd_main () {
     cd_set_environment
     cd_set_dns_resolving \
-    '9.9.9.9'
+    "9.9.9.9"
     cd_set_packages_repositories
     cd_set_packages_configuration
     cd_set_https_verification_off
@@ -25,24 +25,24 @@ cd_main () {
 #
 
 cd_set_environment () {
-    cd_step 'Set environment'
-    CD_DNS_FILE='/etc/resolv.conf'
+    cd_step "Set environment"
+    CD_DNS_FILE="/etc/resolv.conf"
     case "${CD_OS_NAME}" in
-        'debian')
-            CD_PYTHON_COMMAND='python3'
-            CD_PYTHON_PACKAGES='/usr/lib/python3/dist-packages'
+        "debian")
+            CD_PYTHON_COMMAND="python3"
+            CD_PYTHON_PACKAGES="/usr/lib/python3/dist-packages"
             case "${CD_OS_VERSION}" in
-                'bookworm')
-                    echo 'TODO'
+                "bookworm")
+                    echo "TODO"
                 ;;
                 *)
-                    echo 'CD_OS_VERSION'
+                    echo "CD_OS_VERSION"
                     exit 2
                 ;;
             esac
         ;;
         *)
-            echo 'CD_OS_NAME'
+            echo "CD_OS_NAME"
             exit 1
         ;;
     esac
@@ -50,7 +50,7 @@ cd_set_environment () {
     [ "${CI_COMMIT_BRANCH}" ] && CD_PROJECT_BRANCH="${CI_COMMIT_BRANCH}"
     [ "${GITHUB_REF_NAME}" ] && CD_PROJECT_BRANCH="${GITHUB_REF_NAME}"
     if [ ! "${CD_PROJECT_BRANCH}" ] ; then
-        echo 'CD_PROJECT_BRANCH'
+        echo "CD_PROJECT_BRANCH"
         exit 3
     fi
     # project / name
@@ -59,7 +59,7 @@ cd_set_environment () {
     [ "${GITHUB_REPOSITORY}" ] \
     && CD_PROJECT_NAME="$(basename "${GITHUB_REPOSITORY}")"
     if [ ! "${CD_PROJECT_NAME}" ] ; then
-        echo 'CD_PROJECT_NAME'
+        echo "CD_PROJECT_NAME"
         exit 3
     fi
     # projects / group
@@ -68,7 +68,7 @@ cd_set_environment () {
     [ "${GITHUB_REPOSITORY}" ] \
     && CD_PROJECTS_GROUP="$(dirname "${GITHUB_REPOSITORY}")"
     if [ ! "${CD_PROJECTS_GROUP}" ] ; then
-        echo 'CD_PROJECTS_GROUP'
+        echo "CD_PROJECTS_GROUP"
         exit 3
     fi
     # projects / url
@@ -77,7 +77,7 @@ cd_set_environment () {
     if [ "${CD_PROJECTS_URL}" ] ; then
         CD_PROJECTS_URL="${CD_PROJECTS_URL}/${CD_PROJECTS_GROUP}"
     else
-        echo 'CD_PROJECTS_URL'
+        echo "CD_PROJECTS_URL"
         exit 3
     fi
     # project / url
@@ -86,8 +86,8 @@ cd_set_environment () {
 
 cd_set_dns_resolving () {
 local server
-local text=''
-    cd_step 'Set DNS resolving'
+local text=""
+    cd_step "Set DNS resolving"
     for server in "${@}" ; do
         text="${text}nameserver ${server}
 "
@@ -96,10 +96,10 @@ local text=''
 }
 
 cd_set_packages_repositories () {
-    cd_step 'Set packages repositories'
+    cd_step "Set packages repositories"
     case "${CD_OS_NAME}" in
-        'debian')
-            cd_write '/etc/apt/sources.list' "\
+        "debian")
+            cd_write "/etc/apt/sources.list" "\
 deb https://deb.debian.org/debian bookworm main
 deb https://deb.debian.org/debian bookworm-backports main
 deb https://deb.debian.org/debian bookworm-updates main
@@ -111,11 +111,11 @@ deb https://deb.debian.org/debian-security bookworm-security main
 }
 
 cd_set_packages_configuration () {
-    cd_step 'Set packages configuration'
+    cd_step "Set packages configuration"
     case "${CD_OS_NAME}" in
-        'debian')
-            export DEBIAN_FRONTEND='noninteractive'
-            cd_write '/etc/apt/apt.conf.d/apt.conf' "\
+        "debian")
+            export DEBIAN_FRONTEND="noninteractive"
+            cd_write "/etc/apt/apt.conf.d/apt.conf" "\
 Acquire::Check-Valid-Until True;
 APT::Get::Show-Versions True;
 APT::Install-Recommends False;
@@ -128,10 +128,10 @@ Dir::Etc::SourceParts \"\";
 }
 
 cd_set_https_verification_off () {
-    cd_step 'Set HTTPS verification off'
+    cd_step "Set HTTPS verification off"
     case "${CD_OS_NAME}" in
-        'debian')
-            cd_write '/etc/apt/apt.conf.d/https' "\
+        "debian")
+            cd_write "/etc/apt/apt.conf.d/https" "\
 Acquire::https::Verify-Peer False;
 "
         ;;
@@ -140,65 +140,65 @@ Acquire::https::Verify-Peer False;
 }
 
 cd_update_packages_catalog () {
-    cd_step 'Update packages catalog'
+    cd_step "Update packages catalog"
     case "${CD_OS_NAME}" in
-        'debian') apt-get update || exit ;;
+        "debian") apt-get update || exit ;;
         *) exit 1 ;;
     esac
 }
 
 cd_install_packages_tools () {
-    cd_step 'Install packages tools'
+    cd_step "Install packages tools"
     case "${CD_OS_NAME}" in
-        'debian') cd_install_package 'apt-utils' ;;
+        "debian") cd_install_package "apt-utils" ;;
         *) exit 1 ;;
     esac
 }
 
 cd_install_ca () {
-    cd_step 'Install CA'
+    cd_step "Install CA"
     case "${CD_OS_NAME}" in
-        'debian') cd_install_package 'ca-certificates' ;;
+        "debian") cd_install_package "ca-certificates" ;;
         *) exit 1 ;;
     esac
 }
 
 cd_set_https_verification_on () {
-    cd_step 'Set HTTPS verification on'
+    cd_step "Set HTTPS verification on"
     case "${CD_OS_NAME}" in
-        'debian') rm '/etc/apt/apt.conf.d/https' ;;
+        "debian") rm "/etc/apt/apt.conf.d/https" ;;
         *) exit 1 ;;
     esac
 }
 
 cd_upgrade_packages () {
-    cd_step 'Upgrade packages'
+    cd_step "Upgrade packages"
     case "${CD_OS_NAME}" in
-        'debian') apt-get upgrade --yes || exit ;;
+        "debian") apt-get upgrade --yes || exit ;;
         *) exit 1 ;;
     esac
 }
 
 cd_install_git () {
-    cd_step 'Install Git'
+    cd_step "Install Git"
     case "${CD_OS_NAME}" in
-        'debian') cd_install_package 'git' ;;
+        "debian") cd_install_package "git" ;;
         *) exit 1 ;;
     esac
 }
 
 cd_install_python () {
-    cd_step 'Install Python'
+    cd_step "Install Python"
     case "${CD_OS_NAME}" in
-        'debian') cd_install_package 'python3' ;;
+        "debian") cd_install_package "python3" ;;
         *) exit 1 ;;
     esac
 }
 
 cd_clean_packages_cache () {
-    cd_step 'Clean packages cache'
+    cd_step "Clean packages cache"
     case "${CD_OS_NAME}" in
-        'debian') apt-get clean || exit ;;
+        "debian") apt-get clean || exit ;;
         *) exit 1 ;;
     esac
 }
@@ -206,7 +206,7 @@ cd_clean_packages_cache () {
 cd_install () {
 local repository
 local root
-    cd_step 'Install'
+    cd_step "Install"
     root="$(mktemp --directory)" || exit
     for repository in "${@}" ; do
         git clone \
@@ -220,7 +220,7 @@ local root
 }
 
 cd_bootstrap () {
-    cd_step 'Bootstrap'
+    cd_step "Bootstrap"
     "${CD_PYTHON_COMMAND}" -m "${1}"
 }
 
@@ -229,7 +229,7 @@ cd_bootstrap () {
 cd_install_package () {
     if [ "${1}" ] ; then
         case "${CD_OS_NAME}" in
-            'debian') apt-get install --yes "${1}" || exit ;;
+            "debian") apt-get install --yes "${1}" || exit ;;
             *) exit 1 ;;
         esac
     fi