diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..31e7ecc
--- /dev/null
+++ b/.envrc
@@ -0,0 +1,97 @@
+# -*- mode: sh; -*-
+# Thanks <https://github.com/direnv/direnv/issues/73#issuecomment-152284914>
+export_function()
+{
+  local name=$1
+  local alias_dir=$PWD/.direnv/aliases
+  mkdir -p "$alias_dir"
+  PATH_add "$alias_dir"
+  local target="$alias_dir/$name"
+  if declare -f "$name" >/dev/null; then
+    echo "#!$SHELL" > "$target"
+    declare -f "$name" >> "$target" 2>/dev/null
+    # Notice that we add shell variables to the function trigger.
+    echo "$name \$*" >> "$target"
+    chmod +x "$target"
+  fi
+}
+
+use_guix()
+{
+    # Set GitHub token.
+    export GUIX_GITHUB_TOKEN="xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+
+    # Unset 'GUIX_PACKAGE_PATH'.
+    export GUIX_PACKAGE_PATH=""
+
+    # Recreate a garbage collector root.
+    gcroots="$HOME/.config/guix/gcroots"
+    mkdir -p "$gcroots"
+    gcroot="$gcroots/guix"
+    if [ -L "$gcroot" ]
+    then
+        rm -v "$gcroot"
+    fi
+
+    # Miscellaneous packages.
+    PACKAGES_MAINTENANCE=(
+        direnv
+        git
+        git:send-email
+        git-cal
+        gnupg
+        guile-colorized
+        guile-readline
+        less
+        ncurses
+        openssh
+        xdot
+    )
+
+    # Environment packages.
+    PACKAGES=(help2man guile-sqlite3 guile-gcrypt
+    autoconf autoconf-archive automake libtool
+    pkg-config openssl libxml2)
+
+    # Thanks <https://lists.gnu.org/archive/html/guix-devel/2016-09/msg00859.html>
+    eval "$(guix environment --search-paths --root="$gcroot" --pure guix json-c --ad-hoc ${PACKAGES[@]} ${PACKAGES_MAINTENANCE[@]} "$@")"
+
+    export CC=gcc
+
+    # Predefine configure flags.
+    configure()
+    {
+        ./configure --localstatedir=/var --prefix=
+    }
+    export_function configure
+
+    # Run make and optionally build something.
+    build()
+    {
+        make -j 2
+        if [ $# -gt 0 ]
+        then
+            ./pre-inst-env guix build "$@"
+        fi
+    }
+    export_function build
+
+    # Predefine push Git command.
+    push()
+    {
+        git push --set-upstream origin
+    }
+    export_function push
+
+    clear                        # Clean up the screen.
+    git-cal --author='Your Name' # Show contributions calendar.
+
+    # Show commands help.
+    echo "
+build          build a package or just a project if no argument provided
+configure      run ./configure with predefined parameters
+push           push to upstream Git repository
+"
+}
+
+use guix
diff --git a/.gitignore b/.gitignore
index 28a8c3c..93fe681 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+.direnv
 *~
 compile_commands.json
 cscope*