Environment Variables
This page documents all environment variables relevant to the ADL desktop environment, organized by category.
Display Variables
Variables that control how graphical output is rendered.
| Variable | Default Value | Purpose | Example |
|---|---|---|---|
DISPLAY | :0 or :1 | X11 display server connection | export DISPLAY=:1 |
WAYLAND_DISPLAY | wayland-0 | Wayland compositor socket name | export WAYLAND_DISPLAY=wayland-0 |
XDG_SESSION_TYPE | x11 | Session type identifier (x11, wayland, tty) | export XDG_SESSION_TYPE=wayland |
When running a nested X server (such as Xephyr), set DISPLAY to the nested display number to direct applications into it.
Audio Variables
Variables that configure audio routing and device selection.
| Variable | Default Value | Purpose | Example |
|---|---|---|---|
PULSE_SERVER | tcp:127.0.0.1:4713 or unix:/tmp/pulse-socket | PulseAudio server address | export PULSE_SERVER=tcp:127.0.0.1:4713 |
AUDIODEV | (none) | Preferred audio output device | export AUDIODEV=/dev/snd/pcmC0D0p |
On Termux, set PULSE_SERVER to point at the Android host's PulseAudio daemon so that desktop applications can produce sound through the device speakers.
XDG Base Directories
Standardized directories for application data, configuration, and caches.
| Variable | Default Value | Purpose | Example |
|---|---|---|---|
XDG_DATA_HOME | $HOME/.local/share | User-specific data files | export XDG_DATA_HOME=$HOME/.local/share |
XDG_CONFIG_HOME | $HOME/.config | User-specific configuration | export XDG_CONFIG_HOME=$HOME/.config |
XDG_CACHE_HOME | $HOME/.cache | User-specific non-essential cached data | export XDG_CACHE_HOME=$HOME/.cache |
XDG_STATE_HOME | $HOME/.local/state | User-specific state data (logs, history) | export XDG_STATE_HOME=$HOME/.local/state |
XDG_RUNTIME_DIR | /run/user/$UID | Runtime files (sockets, PIDs) | export XDG_RUNTIME_DIR=/tmp/runtime-user |
XDG_DATA_DIRS | /usr/local/share:/usr/share | System-wide data search path | export XDG_DATA_DIRS=/usr/local/share:/usr/share |
XDG_CONFIG_DIRS | /etc/xdg | System-wide configuration search path | export XDG_CONFIG_DIRS=/etc/xdg |
XDG_CURRENT_DESKTOP | (none) | Current desktop environment name | export XDG_CURRENT_DESKTOP=XFCE |
XDG_SESSION_DESKTOP | (none) | Desktop session identifier | export XDG_SESSION_DESKTOP=xfce |
XDG_RUNTIME_DIR must be owned by the user, have permissions 0700, and reside on a local filesystem. Applications may fail if this directory is missing or misconfigured.
Path Variables
Variables that control executable and library lookup paths.
| Variable | Default Value | Purpose | Example |
|---|---|---|---|
PATH | /usr/local/bin:/usr/bin:/bin | Executable search path | export PATH=$HOME/.local/bin:$PATH |
LD_LIBRARY_PATH | (none) | Shared library search path | export LD_LIBRARY_PATH=/opt/lib:$LD_LIBRARY_PATH |
PKG_CONFIG_PATH | (none) | pkg-config metadata search path | export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig |
MANPATH | (system default) | Manual page search path | export MANPATH=$HOME/.local/share/man:$MANPATH |
Always prepend to PATH rather than replacing it. Use export PATH=$HOME/.local/bin:$PATH to add directories without losing system defaults.
Termux-Specific Variables
Variables set automatically by Termux or required for compatibility with the Android environment.
| Variable | Default Value | Purpose | Example |
|---|---|---|---|
PREFIX | /data/data/com.termux/files/usr | Termux root prefix for installed packages | echo $PREFIX |
HOME | /data/data/com.termux/files/home | User home directory in Termux | cd $HOME |
TMPDIR | /data/data/com.termux/files/usr/tmp | Temporary file directory | export TMPDIR=$PREFIX/tmp |
ANDROID_ROOT | /system | Android system partition root | echo $ANDROID_ROOT |
ANDROID_DATA | /data | Android data partition root | echo $ANDROID_DATA |
These variables are set by Termux at shell startup. Overriding them may break package management and other Termux utilities.
Locale and Language
Variables that control language, character encoding, and regional formatting.
| Variable | Default Value | Purpose | Example |
|---|---|---|---|
LANG | C.UTF-8 | Default locale for all categories | export LANG=en_US.UTF-8 |
LC_ALL | (none) | Override for all LC_* categories | export LC_ALL=en_US.UTF-8 |
LANGUAGE | (none) | Ordered list of preferred languages | export LANGUAGE=en_US:en |
LC_CTYPE | (from LANG) | Character classification and conversion | export LC_CTYPE=en_US.UTF-8 |
LC_MESSAGES | (from LANG) | Language of system messages | export LC_MESSAGES=en_US.UTF-8 |
LC_NUMERIC | (from LANG) | Numeric formatting | export LC_NUMERIC=en_US.UTF-8 |
LC_TIME | (from LANG) | Date and time formatting | export LC_TIME=en_US.UTF-8 |
LC_COLLATE | (from LANG) | String collation order | export LC_COLLATE=en_US.UTF-8 |
Set LANG to configure all locale categories at once. Use individual LC_* variables only when you need a specific category to differ from the default.
Application Variables
Variables that define default applications for common tasks.
| Variable | Default Value | Purpose | Example |
|---|---|---|---|
EDITOR | nano | Default text editor (terminal) | export EDITOR=vim |
VISUAL | (none) | Preferred visual/GUI editor | export VISUAL=code |
BROWSER | (none) | Default web browser | export BROWSER=firefox |
TERMINAL | (none) | Default terminal emulator | export TERMINAL=xfce4-terminal |
PAGER | less | Default pager for long output | export PAGER=less |
SHELL | /bin/bash | Current user shell | export SHELL=/bin/bash |
Setting Variables Permanently
Where to place environment variable definitions so they persist across sessions.
| File | Scope | When Loaded |
|---|---|---|
~/.bashrc | Current user, interactive bash shells | Each new interactive shell |
~/.profile | Current user, login shells | Login (console, SSH, display manager) |
/etc/environment | All users | PAM session initialization |
/etc/profile.d/*.sh | All users, login shells | Login shells (sourced by /etc/profile) |
For a single user, add exports to ~/.profile for login-time variables and ~/.bashrc for interactive shell settings:
echo 'export EDITOR=vim' >> ~/.profileFor system-wide variables, create a file in /etc/profile.d/:
echo 'export EDITOR=vim' | sudo tee /etc/profile.d/adl-defaults.shUse ~/.profile for variables that should apply to your entire session (including graphical applications launched from a display manager). Reserve ~/.bashrc for shell-specific aliases and functions.
Checking Current Values
Commands for inspecting environment variables.
| Command | Purpose | Example |
|---|---|---|
echo $VAR | Print a single variable | echo $DISPLAY |
printenv VAR | Print a single variable (no $ prefix) | printenv HOME |
printenv | List all exported variables | printenv | sort |
env | List all variables (similar to printenv) | env | grep XDG |
export | List all exported variables with declarations | export -p |
set | List all shell variables (exported and local) | set | head -50 |
To verify a variable is set and exported:
printenv DISPLAYTo search for all variables matching a pattern:
env | grep -i audio