How to detect the desktop environment in a bash script?

Method #1 - $DESKTOP_SESSION

I think you can find out by interrogating the environment variable $DESKTOP_SESSION. I'm not entirely positive how widely supported this is but in my limited testing it appears to be available on Fedora & Ubuntu.

$ echo $DESKTOP_SESSION
gnome

Another choice is the $XDG_SESSION_DESKTOP variable.

Method #2 - wmctrl

There is also this method that makes use of wmctrl.

$ wmctrl  -m
Name: GNOME Shell
Class: N/A
PID: N/A
Window manager's "showing the desktop" mode: N/A

References

• How to determine which window manager is running

You can use this bash script. It can detect desktop environment name and version.

#!/bin/bash

function detect_gnome()
{
    ps -e | grep -E '^.* gnome-session$' > /dev/null
    if [ $? -ne 0 ];
    then
    return 0
    fi
    VERSION=`gnome-session --version | awk '{print $2}'`
    DESKTOP="GNOME"
    return 1
}

function detect_kde()
{
    ps -e | grep -E '^.* kded4$' > /dev/null
    if [ $? -ne 0 ];
    then
        return 0
    else    
        VERSION=`kded4 --version | grep -m 1 'KDE' | awk -F ':' '{print $2}' | awk '{print $1}'`
        DESKTOP="KDE"
        return 1
    fi
}

function detect_unity()
{
    ps -e | grep -E 'unity-panel' > /dev/null
    if [ $? -ne 0 ];
    then
    return 0
    fi
    VERSION=`unity --version | awk '{print $2}'`
    DESKTOP="UNITY"
    return 1
}

function detect_xfce()
{
    ps -e | grep -E '^.* xfce4-session$' > /dev/null
    if [ $? -ne 0 ];
    then
    return 0
    fi
    VERSION=`xfce4-session --version | grep xfce4-session | awk '{print $2}'`
    DESKTOP="XFCE"
    return 1
}

function detect_cinnamon()
{
    ps -e | grep -E '^.* cinnamon$' > /dev/null
    if [ $? -ne 0 ];
    then
    return 0
    fi
    VERSION=`cinnamon --version | awk '{print $2}'`
    DESKTOP="CINNAMON"
    return 1
}

function detect_mate()
{
    ps -e | grep -E '^.* mate-panel$' > /dev/null
    if [ $? -ne 0 ];
    then
    return 0
    fi
    VERSION=`mate-about --version | awk '{print $4}'`
    DESKTOP="MATE"
    return 1
}

function detect_lxde()
{
    ps -e | grep -E '^.* lxsession$' > /dev/null
    if [ $? -ne 0 ];
    then
    return 0
    fi

    # We can detect LXDE version only thru package manager
    which apt-cache > /dev/null 2> /dev/null
    if [ $? -ne 0 ];
    then
    which yum > /dev/null 2> /dev/null
    if [ $? -ne 0 ];
    then
        VERSION='UNKNOWN'
    else
        # For Fedora
        VERSION=`yum list lxde-common | grep lxde-common | awk '{print $2}' | awk -F '-' '{print $1}'`
    fi
    else    
    # For Lubuntu and Knoppix
    VERSION=`apt-cache show lxde-common /| grep 'Version:' | awk '{print $2}' | awk -F '-' '{print $1}'`
    fi
    DESKTOP="LXDE"
    return 1
}

function detect_sugar()
{
    if [ "$DESKTOP_SESSION" == "sugar" ];
    then
    VERSION=`python -c "from jarabe import config; print config.version"`
    DESKTOP="SUGAR"
    else
    return 0
    fi
}


DESKTOP="UNKNOWN"
if detect_unity;
then
    if detect_kde;
    then
    if detect_gnome;
    then
        if detect_xfce;
        then
        if detect_cinnamon;
        then
            if detect_mate;
            then
            if detect_lxde;
            then
                detect_sugar
            fi
            fi
        fi
        fi
    fi
    fi
fi


if [ "$1" == '-v' ];
then
    echo $VERSION
else
    if [ "$1" == '-n' ];
    then
    echo $DESKTOP
    else
    echo $DESKTOP $VERSION
    fi
fi

Standards evolved a lot since question was made in 2014.

For 2021, my recommendation is: use only the official $XDG_CURRENT_DESKTOP.

Be careful that officially it is a colon-separated list (like $PATH), so don't assume it only contains a single value, even if it does in most DEs. For example, in Ubuntu's Unity it's set to Unity:Unity7:ubuntu.

If you prefer to handle a single value, use $XDG_SESSION_DESKTOP.

Official standards:

• XDG_CURRENT_DESKTOP, defined in the Desktop Entry Specification since its version 1.2

• XDG_SESSION_DESKTOP, best described in systemd's PAM

Other related environment variables should be considered legacy by now.

A bash function to properly check a given string against the current desktop environment:

# Encapsulates the mess that DE detection was, is, or will ever be...
# Without arguments, check if in a Desktop Environment at all
# Subshell is intentional so we don't have to save/restore IFS
# Case-insensitive comparison
is_desktop_environment() (
    local de=${1:-}
    local DEs=${XDG_CURRENT_DESKTOP:-}

    # Shortcut: If de is empty, check if empty DEs
    if [[ -z "$de" ]]; then if [[ "$DEs" ]]; then return; else return 1; fi; fi

    # Lowercase both
    de=${de,,}; DEs=${DEs,,}

    # Check de against each DEs component
    IFS=:; for DE in $DEs; do if [[ "$de" == "$DE" ]]; then return; fi; done

    # Not found
    return 1
)

Testing:

for de in "" Ubuntu Gnome KDE Unity; do
    if is_desktop_environment "$de"; then
        echo "Yes, this is ${de:-a DE}"
    else
        echo "No,  this is not ${de:-a DE}"
    fi
done

Yes, this is a DE
Yes, this is Ubuntu
No,  this is not Gnome
No,  this is not KDE
Yes, this is Unity

That probably depends on the situation. If you know which display manager is used then it may be that this one puts this information in a environment variable.

If that is not the case then I guess you have to check for every DE you want to be able to identify. All of them should introduce their own environment variables.

If the environmental variable XDG_CURRENT_DESKTOP is available, it should tell you.

# echo $XDG_CURRENT_DESKTOP
KDE

You could look for running Xorg processes. The parent of this should be your display manager. Its descendants should give an indication of what desktop environment is running. On my system, the display manager executes itself (with different parameters). This then spawns x-session-manager which is symlinked to xfce4-session. This may be enough, but all the children of this are related to my desktop environment. Finding them via the process tree should be the best way to exclude elements of other window systems started by various programs (or perhaps deliberately).

My first thought was that it would be be best to look for the window manager associated with your desktop environment, but often a different one can be configured to run (eg xmonad in Gnome) so this is not robust. The best one to look for is probably the one which manages the actual desktop, eg xfdesktop or whatever element of the desktop environment you actally need for your script to work :)

Example

Here is an example using procps-ng (-C and --ppid are not POSIX). It assumes the is only one instance of Xorg.

This is just an example that works for the xfce desktop. A full working example requires an investigation in to the processes that each desktop system uses, just as most of the other solutions require investigation into how environmental variables are set in various other desktop systems.

X=Xorg

search_descendants ()
{
  ps h -o comm --ppid $1 |
    grep -E '^(xfdesktop|another_desktop_process)$' &&
    return 0

  for pid in $(ps h -o pid --ppid $1)
  do
    search_descendants $pid && return 0
  done

  return 1
}

dm_pid=$(ps h -o ppid -C "$X")

case "$(search_descendants $dm_pid)" in
  xfdesktop)
    desktop=xfce
    ;;
  another_desktop_process)
    desktop=another_desktop
    ;;
  *)
    desktop=unknown
    ;;
esac

echo $desktop

From all the experimenting reported in the numerous comments, I think its my duty as the OP to come up with a consensus answer. (Rest assured, I would be happy to review this answer should contrasting data become available.)

For now, it seems best to take our lead from $XDG_CURRENT_DESKTOP when this variable is defined. If not, $XDG_DATA_DIRS may provide the desired information, more so than the first letter of ${DESKTOP_SESSION:0:1}.

This works on both Ubuntu 18.10 (cosmic) [lxqt type] and Mint 19 (tara) [cinnamon type]:

$  set | grep XDG_CURRENT_DESKTOP | tr '[:upper:]' '[:lower:]' | cut -d'=' -f2

Capture the result into a variable, and execute further necessary code via capable analytic logic (case stmt, if/then) which includes any/all recognized types from there; and/or function gracefully when unrecognized types are in use.