diff --git a/cd.sh b/cd.sh
index eddae10..5058593 100644
--- a/cd.sh
+++ b/cd.sh
@@ -1,11 +1,11 @@
 #! /usr/bin/env sh
 
 # defaults
-[ -n "${CD_DNS}" ] || CD_DNS="\
+[ "${CD_DNS}" ] || CD_DNS="\
 9.9.9.9 \
 "
-[ -n "${CD_GIT_CHILD}" ] || CD_GIT_CHILD="cd"
-[ -n "${CD_GIT_PARENT}" ] || CD_GIT_PARENT="rwx"
+[ "${CD_GIT_CHILD}" ] || CD_GIT_CHILD="cd"
+[ "${CD_GIT_PARENT}" ] || CD_GIT_PARENT="rwx"
 
 # main
 cd_main () {
@@ -40,9 +40,6 @@ cd_main () {
 
 cd_set_environment_variables () {
     cd_step "Set environment variables"
-    # set path
-    CD_PATH="$(realpath "${0}")"
-    cd_echo "CD_PATH"
     # set operating system id
     CD_OS_ID="$(cd_grep_os ID)"
     case "${CD_OS_ID}" in
@@ -68,7 +65,6 @@ cd_set_environment_variables () {
         "${CD_OS_DEBIAN}"|"${CD_OS_UBUNTU}")
             CD_OS_VERSION="$(cd_grep_os VERSION_CODENAME)"
         ;;
-        *)
     esac
     # check operating system version
     case "${CD_OS_ID}" in
@@ -108,9 +104,7 @@ cd_set_environment_variables () {
                 *) cd_error_os "CD_OS_VERSION" ;;
             esac
         ;;
-        *)
     esac
-    cd_split
     cd_echo "CD_OS_ID" "CD_OS_VERSION"
     # universal
     CD_DNS_FILE="/etc/resolv.conf"
@@ -139,7 +133,6 @@ cd_set_environment_variables () {
             CD_CA_ROOT="/usr/local/share/ca-certificates"
             CD_CMD_CA="update-ca-certificates"
         ;;
-        *)
     esac
     cd_split
     cd_echo "CD_CA_ROOT" "CD_CMD_CA"
@@ -157,7 +150,6 @@ cd_set_environment_variables () {
         "${CD_OS_ARCH}")
             CD_PM="${CD_PM_PACMAN}"
         ;;
-        *)
     esac
     cd_split
     cd_echo "CD_PM"
@@ -231,7 +223,6 @@ Dir::Etc::SourceParts \"\";
 Acquire::https::Verify-Peer False;
 "
         ;;
-        *)
     esac
     cd_split
     cd_echo "CD_PM_CLEAN" \
@@ -261,36 +252,34 @@ Acquire::https::Verify-Peer False;
         "${CD_OS_UBUNTU}")
             CD_URL_DEFAULT="http://archive.ubuntu.com/ubuntu"
         ;;
-        *)
     esac
     CD_URL_CHOSEN="${CD_URL_DEFAULT}"
     case "${CD_OS_ID}" in
         "${CD_OS_ALMA}")
-            [ -n "${CD_URL_ALMA}" ] && CD_URL_CHOSEN="${CD_URL_ALMA}"
+            [ "${CD_URL_ALMA}" ] && CD_URL_CHOSEN="${CD_URL_ALMA}"
         ;;
         "${CD_OS_ALPINE}")
-            [ -n "${CD_URL_ALPINE}" ] && CD_URL_CHOSEN="${CD_URL_ALPINE}"
+            [ "${CD_URL_ALPINE}" ] && CD_URL_CHOSEN="${CD_URL_ALPINE}"
         ;;
         "${CD_OS_ARCH}")
-            [ -n "${CD_URL_ARCH}" ] && CD_URL_CHOSEN="${CD_URL_ARCH}"
+            [ "${CD_URL_ARCH}" ] && CD_URL_CHOSEN="${CD_URL_ARCH}"
         ;;
         "${CD_OS_DEBIAN}")
-            [ -n "${CD_URL_DEBIAN}" ] && CD_URL_CHOSEN="${CD_URL_DEBIAN}" \
+            [ "${CD_URL_DEBIAN}" ] && CD_URL_CHOSEN="${CD_URL_DEBIAN}" \
             || CD_URL_CHOSEN="https://deb.debian.org/debian"
         ;;
         "${CD_OS_FEDORA}")
-            [ -n "${CD_URL_FEDORA}" ] && CD_URL_CHOSEN="${CD_URL_FEDORA}" \
+            [ "${CD_URL_FEDORA}" ] && CD_URL_CHOSEN="${CD_URL_FEDORA}" \
             || CD_URL_CHOSEN="https://rpmfind.net/linux/fedora/linux/releases"
         ;;
         "${CD_OS_ROCKY}")
-            [ -n "${CD_URL_ROCKY}" ] && CD_URL_CHOSEN="${CD_URL_ROCKY}" \
+            [ "${CD_URL_ROCKY}" ] && CD_URL_CHOSEN="${CD_URL_ROCKY}" \
             || CD_URL_CHOSEN="https://dl.rockylinux.org/\$contentdir"
         ;;
         "${CD_OS_UBUNTU}")
-            [ -n "${CD_URL_UBUNTU}" ] && CD_URL_CHOSEN="${CD_URL_UBUNTU}" \
+            [ "${CD_URL_UBUNTU}" ] && CD_URL_CHOSEN="${CD_URL_UBUNTU}" \
             || CD_URL_CHOSEN="https://ubuntu.mirrors.ovh.net/ubuntu"
         ;;
-        *)
     esac
     cd_split
     cd_echo "CD_URL_DEFAULT" "CD_URL_CHOSEN"
@@ -312,7 +301,6 @@ Acquire::https::Verify-Peer False;
             case "${CD_OS_VERSION}" in
                 "bookworm") CD_PYTHON_COMMAND="python3.11" ;;
                 "bullseye") CD_PYTHON_COMMAND="python3.9" ;;
-                *)
             esac
             CD_PYTHON_PACKAGE="python3"
         ;;
@@ -324,11 +312,9 @@ Acquire::https::Verify-Peer False;
             case "${CD_OS_VERSION}" in
                 "noble") CD_PYTHON_COMMAND="python3.12" ;;
                 "jammy") CD_PYTHON_COMMAND="python3.10" ;;
-                *)
             esac
             CD_PYTHON_PACKAGE="python3"
         ;;
-        *)
     esac
     # set python packages
     case "${CD_OS_ID}" in
@@ -341,20 +327,19 @@ Acquire::https::Verify-Peer False;
         "${CD_OS_DEBIAN}"|"${CD_OS_UBUNTU}")
             CD_PYTHON_PACKAGES="/usr/lib/${CD_PYTHON_ALIAS}/dist-packages"
         ;;
-        *)
     esac
     cd_split
     cd_echo "CD_PYTHON_COMMAND" "CD_PYTHON_PACKAGE" "CD_PYTHON_PACKAGES"
     # variables
-    [ -n "${CD_CA_1}" ] && CD_CA=true
+    [ "${CD_CA_1}" ] && CD_CA=true
     # continuous integration platform
-    if [ -n "${GITHUB_ACTIONS}" ] ; then
+    if [ "${GITHUB_ACTIONS}" ] ; then
         # github → gitea → forgejo
         CD_SERVER_URL="${GITHUB_SERVER_URL}"
         CD_PROJECTS_GROUP="$(dirname "${GITHUB_REPOSITORY}")"
         CD_PROJECT_NAME="$(basename "${GITHUB_REPOSITORY}")"
         CD_PROJECT_BRANCH="${GITHUB_REF_NAME}"
-    elif [ -n "${GITLAB_CI}" ] ; then
+    elif [ "${GITLAB_CI}" ] ; then
         # gitlab
         CD_SERVER_URL="${CI_SERVER_URL}"
         CD_PROJECTS_GROUP="$(dirname "${CI_PROJECT_PATH}")"
@@ -364,12 +349,13 @@ Acquire::https::Verify-Peer False;
         # unsupported
         cd_error_ci "ø"
     fi
-    [ -n "${CD_SERVER_URL}" ] || cd_error_ci "CD_SERVER_URL"
-    [ -n "${CD_PROJECTS_GROUP}" ] || cd_error_ci "CD_PROJECTS_GROUP"
-    [ -n "${CD_PROJECT_NAME}" ] || cd_error_ci "CD_PROJECT_NAME"
-    [ -n "${CD_PROJECT_BRANCH}" ] || cd_error_ci "CD_PROJECT_BRANCH"
+    [ "${CD_SERVER_URL}" ] || cd_error_ci "CD_SERVER_URL"
+    [ "${CD_PROJECTS_GROUP}" ] || cd_error_ci "CD_PROJECTS_GROUP"
+    [ "${CD_PROJECT_NAME}" ] || cd_error_ci "CD_PROJECT_NAME"
+    [ "${CD_PROJECT_BRANCH}" ] || cd_error_ci "CD_PROJECT_BRANCH"
     #
     CD_PROJECTS_URL="${CD_SERVER_URL}/${CD_PROJECTS_GROUP}"
+    CD_PROJECT_URL="${CD_PROJECTS_URL}/${CD_PROJECT_NAME}"
     #
     cd_split
     cd_echo "CD_CA"
@@ -377,42 +363,40 @@ Acquire::https::Verify-Peer False;
     cd_echo "CD_SERVER_URL" \
         "CD_PROJECTS_GROUP" "CD_PROJECT_NAME" "CD_PROJECT_BRANCH"
     cd_split
-    cd_echo "CD_PROJECTS_URL"
+    cd_echo "CD_PROJECTS_URL" "CD_PROJECT_URL"
     # TODO move to Python
     case "${CD_PM}" in
         "${CD_PM_APK}"|"${CD_PM_APT}") CD_PKG_SSH="openssh-client" ;;
         "${CD_PM_DNF}") CD_PKG_SSH="openssh-clients" ;;
         "${CD_PM_PACMAN}") CD_PKG_SSH="openssh" ;;
-        *)
     esac
 }
 
 cd_set_packages_repositories () {
+local expression
+local file
     cd_step "Set packages repositories"
     case "${CD_OS_ID}" in
         "${CD_OS_ALMA}")
             case "${CD_OS_VERSION}" in
-                "8") \
-cd_set_packages_repositories__file="/etc/yum.repos.d/almalinux.repo" ;;
-                "9") \
-cd_set_packages_repositories__file="/etc/yum.repos.d/almalinux-baseos.repo" ;;
-                *)
+                "8") file="/etc/yum.repos.d/almalinux.repo" ;;
+                "9") file="/etc/yum.repos.d/almalinux-baseos.repo" ;;
             esac
-            cd_sed "${cd_set_packages_repositories__file}" \
+            cd_sed "${file}" \
             "|^mirrorlist|# mirrorlist|" \
             "|${CD_URL_DEFAULT}|${CD_URL_CHOSEN}|" \
             "|^# baseurl|baseurl|"
         ;;
         "${CD_OS_ALPINE}")
-            cd_set_packages_repositories__file="/etc/apk/repositories"
-            cd_write "${cd_set_packages_repositories__file}" "\
+            file="/etc/apk/repositories"
+            cd_write "${file}" "\
 ${CD_URL_CHOSEN}/v${CD_OS_VERSION}/main
 ${CD_URL_CHOSEN}/v${CD_OS_VERSION}/community
 "
         ;;
         "${CD_OS_DEBIAN}")
-            cd_set_packages_repositories__file="/etc/apt/sources.list"
-            cd_write "${cd_set_packages_repositories__file}" "\
+            file="/etc/apt/sources.list"
+            cd_write "${file}" "\
 deb ${CD_URL_CHOSEN} ${CD_OS_VERSION} main
 deb ${CD_URL_CHOSEN} ${CD_OS_VERSION}-backports main
 deb ${CD_URL_CHOSEN} ${CD_OS_VERSION}-updates main
@@ -421,27 +405,23 @@ deb ${CD_URL_CHOSEN}-security ${CD_OS_VERSION}-security main
         ;;
         "${CD_OS_ROCKY}")
             case "${CD_OS_VERSION}" in
-                "8") \
-cd_set_packages_repositories__file="/etc/yum.repos.d/Rocky-BaseOS.repo" ;;
-                "9") \
-cd_set_packages_repositories__file="/etc/yum.repos.d/rocky.repo" ;;
-                *)
+                "8") file="/etc/yum.repos.d/Rocky-BaseOS.repo" ;;
+                "9") file="/etc/yum.repos.d/rocky.repo" ;;
             esac
-            cd_sed "${cd_set_packages_repositories__file}" \
+            cd_sed "${file}" \
             "|^mirrorlist|# mirrorlist|" \
             "|${CD_URL_DEFAULT}|${CD_URL_CHOSEN}|" \
             "|^#baseurl|baseurl|"
         ;;
         "${CD_OS_UBUNTU}")
-            cd_set_packages_repositories__file="/etc/apt/sources.list"
-            cd_write "${cd_set_packages_repositories__file}" "\
+            file="/etc/apt/sources.list"
+            cd_write "${file}" "\
 deb ${CD_URL_CHOSEN} ${CD_OS_VERSION} main
 deb ${CD_URL_CHOSEN} ${CD_OS_VERSION}-backports main
 deb ${CD_URL_CHOSEN} ${CD_OS_VERSION}-updates main
 deb ${CD_URL_CHOSEN} ${CD_OS_VERSION}-security main
 "
         ;;
-        *)
     esac
 }
 
@@ -452,7 +432,6 @@ cd_set_packages_configuration () {
         "${CD_OS_DEBIAN}"|"${CD_OS_UBUNTU}")
             export DEBIAN_FRONTEND="noninteractive"
         ;;
-        *)
     esac
 }
 
@@ -460,12 +439,11 @@ cd_set_packages_configuration () {
 
 cd_list_working_directory () {
     cd_step "List working directory"
-    cd_list_working_directory__path="$(realpath .)"
-    cd_ls "${cd_list_working_directory__path}"
+    cd_ls "$(realpath .)"
 }
 
 cd_set_https_verification_off () {
-    if [ -n "${CD_CA}" ] || [ "${CD_PM}" = "${CD_PM_APT}" ] ; then
+    if [ "${CD_CA}" -o "${CD_PM}" = "${CD_PM_APT}" ] ; then
         cd_step "Set HTTPS verification off"
         cd_mkdir "$(dirname "${CD_PM_HTTPS_PATH}")"
         cd_write "${CD_PM_HTTPS_PATH}" "${CD_PM_HTTPS_TEXT}"
@@ -473,13 +451,14 @@ cd_set_https_verification_off () {
 }
 
 cd_set_dns_resolving () {
+local server
+local text=""
     cd_step "Set DNS resolving"
-    for cd_set_dns_resolving__server in ${CD_DNS} ; do
-        cd_set_dns_resolving__text="${cd_set_dns_resolving__text}\
-nameserver ${cd_set_dns_resolving__server}
+    for server in ${CD_DNS} ; do
+        text="${text}nameserver ${server}
 "
     done
-    cd_write "${CD_DNS_FILE}" "${cd_set_dns_resolving__text}"
+    cd_write "${CD_DNS_FILE}" "${text}"
 }
 
 cd_update_packages_catalog () {
@@ -498,22 +477,20 @@ cd_install_ca_certificates () {
 }
 
 cd_write_ca_certificates () {
+local index
+local path
+local text
     cd_step "Write CA certificates"
     cd_mkdir "${CD_CA_ROOT}"
-    cd_write_ca_certificates__index=1
-    eval "cd_write_ca_certificates__text=\
-\"\${CD_CA_${cd_write_ca_certificates__index}}\""
-    while [ -n "${cd_write_ca_certificates__text}" ] ; do
-        cd_write_ca_certificates__path="\
-${CD_CA_ROOT}/${cd_write_ca_certificates__index}.crt"
+    index=1
+    eval "text=\"\${CD_CA_${index}}\""
+    while [ "${text}" ] ; do
+        path="${CD_CA_ROOT}/${index}.crt"
         cd_split
-        cd_write \
-        "${cd_write_ca_certificates__path}" \
-        "${cd_write_ca_certificates__text}"
-        cd_openssl "${cd_write_ca_certificates__path}"
-        cd_write_ca_certificates__index=$((cd_write_ca_certificates__index+1))
-        eval "cd_write_ca_certificates__text=\
-\"\${CD_CA_${cd_write_ca_certificates__index}}\""
+        cd_write "${path}" "${text}"
+        cd_openssl "${path}"
+        index=$((index+1))
+        eval "text=\"\${CD_CA_${index}}\""
     done
 }
 
@@ -562,174 +539,169 @@ cd_clean_packages_cache () {
 }
 
 cd_install_python_modules () {
+local path
+local repository
+local root
+local url
     cd_step "Install Python modules"
-    cd_install_python_modules__root="$(mktemp --directory)" || exit
-    echo "→ ${cd_install_python_modules__root}"
-    for cd_install_python_modules__repository \
-    in "${CD_GIT_CHILD}" "${CD_GIT_PARENT}" ; do
+    root="$(mktemp --directory)" || exit
+    echo "→ ${root}"
+    for repository in "${CD_GIT_CHILD}" "${CD_GIT_PARENT}" ; do
         cd_split
-        cd_install_python_modules__url="\
-${CD_PROJECTS_URL}/${cd_install_python_modules__repository}"
-        echo "\
-${cd_install_python_modules__url}
-↓"
-        git clone \
-        "${cd_install_python_modules__url}" \
-        "${cd_install_python_modules__root}\
-/${cd_install_python_modules__repository}" \
-        || exit
-        cd_install_python_modules__path="\
-${cd_install_python_modules__root}\
-/${cd_install_python_modules__repository}\
-/${cd_install_python_modules__repository}"
-        echo "\
-${cd_install_python_modules__path}
+        url="${CD_PROJECTS_URL}/${repository}"
+        echo -n "\
+${url}
 ↓
-${CD_PYTHON_PACKAGES}"
+"
+        git clone \
+        "${url}" "${root}/${repository}" \
+        || exit
+        path="${root}/${repository}/${repository}"
+        echo -n "\
+${path}
+↓
+${CD_PYTHON_PACKAGES}
+"
         cp --recursive \
-        "${cd_install_python_modules__path}" "${CD_PYTHON_PACKAGES}" \
+        "${path}" "${CD_PYTHON_PACKAGES}" \
         || exit
     done
     cd_split
     cd_ls "${CD_PYTHON_PACKAGES}"
     cd_split
-    cd_rm "${cd_install_python_modules__root}"
+    cd_rm "${root}"
 }
 
 cd_write_python_module () {
     cd_step "Write Python module"
-    for cd_write_python_module__variable \
-    in OPEN DOWN VERT SPLT __UP SHUT OS_ID OS_VERSION ; do
-        cd_write_python_module__value="\
-$(cd_echo "CD_${cd_write_python_module__variable}")"
-        cd_write_python_module__text="${cd_write_python_module__text}\
-${cd_write_python_module__value}
-"
-    done
-    cd_write "${CD_PYTHON_PACKAGES}/env.py" "${cd_write_python_module__text}\
+    cd_write "${CD_PYTHON_PACKAGES}/env.py" "\
+$(cd_echo CD_OPEN CD_DOWN)
+$(cd_echo CD_VERT CD_SPLT)
+$(cd_echo CD___UP CD_SHUT)
+
+$(cd_echo CD_OS_ID CD_OS_VERSION)
+
 CD_STEP = $((CD_STEP+1))
 "
 }
 
 cd_switch_to_python () {
+local path
     cd_step "Switch to Python"
-    echo "\
-${CD_PATH}
+    #
+    path="$(realpath "${0}")"
+    echo -n "\
+${path}
 ↓
-${CD_PYTHON_PACKAGES}/${CD_GIT_CHILD}"
+${CD_PYTHON_PACKAGES}/${CD_GIT_CHILD}
+"
     "${CD_PYTHON_ALIAS}" -m "${CD_GIT_CHILD}" "${@}"
 }
 
 # functions
 
 cd_cat () {
-    cd_cat__file="${1}"
-    if [ -n "${cd_cat__file}" ] ; then
-        cd_open "${cd_cat__file}"
-        cat "${cd_cat__file}" || exit
-        cd_shut "${cd_cat__file}"
+    if [ -f "${1}" ] ; then
+        cd_open "${1}"
+        cat "${1}" || exit
+        cd_shut "${1}"
     fi
 }
 
 cd_echo () {
-    if [ -n "${1}" ] ; then
-        for cd_echo__name in "${@}" ; do
-            eval "echo ${cd_echo__name} = \\\"\${${cd_echo__name}}\\\""
+local name
+    if [ "${1}" ] ; then
+        for name in "${@}" ; do
+            eval "echo ${name} = \\\"\${${name}}\\\""
         done
     fi
 }
 
 cd_error_ci () {
-    echo "× CI: ${*}"
-    exit "${CD_ERROR_CI}"
+    echo "× CI: ${1}"
+    exit ${CD_ERROR_CI}
 }
 
 cd_error_os () {
-    cd_error_os__variable="${1}"
-    printf "× OS: "
-    cd_echo "${cd_error_os__variable}"
-    exit "${CD_ERROR_OS}"
+local variable="${1}"
+    echo -n "× OS: "
+    cd_echo "${variable}"
+    exit ${CD_ERROR_OS}
 }
 
 cd_grep_os () {
-    cd_grep_os__variable="${1}"
-    if [ -n "${cd_grep_os__variable}" ] ; then
-        grep "^${cd_grep_os__variable}=" "/etc/os-release" \
-        | sed "s|^${cd_grep_os__variable}=||" \
+local variable="${1}"
+    if [ "${variable}" ] ; then
+        grep "^${variable}=" "/etc/os-release" \
+        | sed "s|^${variable}=||" \
         | sed "s|^\"\(.*\)\"$|\1|"
     fi
 }
 
 cd_install_package () {
-    cd_install_package__name="${1}"
-    if [ -n "${cd_install_package__name}" ] ; then
-        ${CD_PM_INSTALL} "${cd_install_package__name}" || exit
+    if [ "${1}" ] ; then
+        ${CD_PM_INSTALL} "${1}" || exit
     fi
 }
 
 cd_ln_python () {
-    cd_ln_python__command="${1}"
-    if [ -n "${cd_ln_python__command}" ] ; then
-        echo "→ ${CD_PYTHON_ALIAS} → ${cd_ln_python__command}"
-        ln -f -s "${cd_ln_python__command}" "/usr/bin/${CD_PYTHON_ALIAS}" \
-        || exit
+local command="${1}"
+    if [ "${command}" ] ; then
+        echo "→ ${CD_PYTHON_ALIAS} → ${command}"
+        ln -f -s "${command}" "/usr/bin/${CD_PYTHON_ALIAS}" || exit
     fi
 }
 
 cd_ls () {
-    cd_ls__path="${1}"
-    if [ -n "${cd_ls__path}" ] ; then
-        cd_open "${cd_ls__path}"
-        ls -a -l "${cd_ls__path}" || exit
-        cd_shut "${cd_ls__path}"
+    if [ -d "${1}" ] ; then
+        cd_open "${1}"
+        ls -a -l "${1}" || exit
+        cd_shut "${1}"
     fi
 }
 
 cd_mkdir () {
-    cd_mkdir__path="${1}"
-    if [ -n "${cd_mkdir__path}" ] ; then
-        echo "→ ${cd_mkdir__path}"
-        mkdir --parents "${cd_mkdir__path}" || exit
+    if [ "${1}" ] ; then
+        echo "→ ${1}"
+        mkdir --parents "${1}" || exit
     fi
 }
 
 cd_open () {
-    echo "${CD_OPEN}${*}"
+    echo "${CD_OPEN}${@}"
 }
 
 cd_openssl () {
-    cd_openssl__file="${1}"
-    if [ -f "${cd_openssl__file}" ] ; then
-        openssl x509 \
-        -in "${cd_openssl__file}" \
-        -noout -text \
-        || exit
+local file="${1}"
+    if [ -f "${file}" ] ; then
+        openssl x509 -noout -text -in "${file}" || exit
     fi
 }
 
 cd_rm () {
-    cd_rm__path="${1}"
-    if [ -e "${cd_rm__path}" ] ; then
-        echo "← ${cd_rm__path}"
-        rm -r "${cd_rm__path}" || exit
+local path="${1}"
+    if [ -e "${path}" ] ; then
+        echo "← ${path}"
+        rm -r "${path}" || exit
     fi
 }
 
 cd_sed () {
-    cd_sed__file="${1}"
-    shift
-    if [ -f "${cd_sed__file}" ] ; then
-        cd_cat "${cd_sed__file}"
-        for cd_sed__regex in "${@}" ; do
-            sed --in-place "s${cd_sed__regex}g" "${cd_sed__file}" \
-            && cd_cat "${cd_sed__file}" \
+local expression
+local file="${1}"
+shift
+    if [ -f "${file}" ] ; then
+        cd_cat "${file}"
+        for expression in "${@}" ; do
+            sed --in-place "s${expression}g" "${file}" \
+            && cd_cat "${file}" \
             || exit
         done
     fi
 }
 
 cd_shut () {
-    echo "${CD_SHUT}${*}"
+    echo "${CD_SHUT}${@}"
 }
 
 cd_split () {
@@ -738,20 +710,21 @@ cd_split () {
 
 cd_step () {
     CD_STEP=$((CD_STEP+1))
-    echo "\
+    echo -n "\
 ${CD_DOWN}
-${CD_VERT} ${CD_STEP} ${*}
-${CD___UP}"
+${CD_VERT} ${CD_STEP} ${@}
+${CD___UP}
+"
 }
 
 cd_write () {
-    cd_write__file="${1}"
-    cd_write__text="${2}"
-    if [ -n "${cd_write__file}" ] ; then
-        [ -f "${cd_write__file}" ] && cd_cat "${cd_write__file}"
-        echo "→ ${cd_write__file}"
-        printf "%s" "${cd_write__text}" > "${cd_write__file}" || exit
-        cd_cat "${cd_write__file}"
+local file="${1}"
+local text="${2}"
+    if [ "${file}" ] ; then
+        [ -f "${file}" ] && cd_cat "${file}"
+        echo "→ ${1}"
+        echo -n "${text}" > "${file}" || exit
+        cd_cat "${file}"
     fi
 }
 
diff --git a/cd/__init__.py b/cd/__init__.py
index 4ea730e..befcf35 100644
--- a/cd/__init__.py
+++ b/cd/__init__.py
@@ -6,7 +6,7 @@ import env
 from rwx import fs
 from rwx import ps
 
-COMMANDS_PREFIX = "cd-"
+COMMANDS_PREFIX = 'cd-'
 
 projects = Projects(os.environ)
 project = Project(projects)
@@ -17,8 +17,8 @@ def cd_browse_workspace():
 
 
 def cd_build_project():
-    for extension in ["py", "sh"]:
-        path = os.path.join(project.root, f"build.{extension}")
+    for extension in ['py', 'sh']:
+        path = os.path.join(project.root, f'build.{extension}')
         if os.path.exists(path):
             ps.run(path)
             break
@@ -27,14 +27,14 @@ def cd_build_project():
 
 
 def cd_clone_branch():
-    print(f"""\
+    print(f'''\
 {project.url}
 ↓
-""", end="", flush=True)
-    ps.run("git",
-        "clone",
-        "--branch", project.branch,
-        "--",
+''', end=str(), flush=True)
+    ps.run('git',
+        'clone',
+        '--branch', project.branch,
+        '--',
         project.url,
         project.root,
     )
@@ -42,25 +42,25 @@ def cd_clone_branch():
 
 def cd_list_environment():
     for variable, value in sorted(projects.environment.items()):
-        print(variable, "=", value)
+        print(variable, '=', value)
 
 
 def cd_synchronize():
-    host = "rwx.work"
-    source = "out"
-    user = "cd"
+    host = 'rwx.work'
+    source = 'out'
+    user = 'cd'
     #
-    root = os.sep.join(["",
+    root = os.sep.join([str(),
                         user, project.branch, projects.group, project.name])
     #
-    target = f"{user}@{host}:{root}"
-    ps.run("rsync",
-        "--archive",
-        "--delete-before",
-        "--verbose",
-        f"{source}/",
-        f"{target}/",
-        "--dry-run",
+    target = f'{user}@{host}:{root}'
+    ps.run('rsync',
+        '--archive',
+        '--delete-before',
+        '--verbose',
+        f'{source}/',
+        f'{target}/',
+        '--dry-run',
     )
 
 
@@ -84,38 +84,38 @@ def cat(file: str):
 
 
 def install_commands(path):
-    step("Install commands")
-    user = "/usr/local/bin"
+    step('Install commands')
+    user = '/usr/local/bin'
     for command in [
-        "browse-workspace",
-        "build-project",
-        "clone-branch",
-        "list-environment",
-        "synchronize",
+        'browse-workspace',
+        'build-project',
+        'clone-branch',
+        'list-environment',
+        'synchronize',
     ]:
         print(command)
-        os.symlink(path, os.path.join(user, f"{COMMANDS_PREFIX}{command}"))
+        os.symlink(path, os.path.join(user, f'{COMMANDS_PREFIX}{command}'))
 
 
 def set_ssh(*arguments):
-    step("Set SSH")
+    step('Set SSH')
     #
     ssh_key, ssh_hosts = arguments
     #
-    ssh_type = "ed25519"
+    ssh_type = 'ed25519'
     #
-    home = os.path.expanduser("~")
+    home = os.path.expanduser('~')
     #
-    ssh = os.path.join(home, ".ssh")
+    ssh = os.path.join(home, '.ssh')
     os.makedirs(ssh, exist_ok=True)
     os.chmod(ssh, 0o700)
     #
-    key = os.path.join(ssh, f"id_{ssh_type}")
+    key = os.path.join(ssh, f'id_{ssh_type}')
     if ssh_key:
         fs.write(key, ssh_key)
         os.chmod(key, 0o400)
     #
-    known = os.path.join(ssh, "known_hosts")
+    known = os.path.join(ssh, 'known_hosts')
     if ssh_hosts:
         fs.write(known, ssh_hosts)
         os.chmod(known, 0o400)
@@ -125,12 +125,12 @@ def set_ssh(*arguments):
 
 
 def open(*arguments):
-    print(env.CD_OPEN, end="")
+    print(env.CD_OPEN, end=str())
     print(*arguments, flush=True)
 
 
 def shut(*arguments):
-    print(env.CD_SHUT, end="")
+    print(env.CD_SHUT, end=str())
     print(*arguments, flush=True)