How to detect the desktop environment in a bash script?

The main problem with checking the DESKTOP_SESSION is that it is set by the display manager rather than the desktop session and is subject to inconsistencies. For lightdm on Debian, the values come from the names of files under /usr/share/xsessions/. DESKTOP_SESSION reflects the desktop environment if a specific selection is made at log in, however the lightdm-xsession is always used the default session.

GDMSESSION is another option, but seems to have a similar predicament (it is the same value as DESKTOP_SESSION for me).

XDG_CURRENT_DESKTOP looks like a good choice, however it is currently not in the XDG standard and thus not always implemented. See here for a discussion of this. This answer shows its values for different distros/desktops, I can also confirm it is currently not available for me on XFCE.

The reasonable fallback for XDG_CURRENT_DESKTOP not existing would be to try XDG_DATA_DIRS. Provided the data files for the desktop environment are installed in a directory bearing its name, this approach should work. This will hopefully be the case for all distros/desktops!

The following (with GNU grep) tests for XFCE, KDE and Gnome:

echo "$XDG_DATA_DIRS" | grep -Eo 'xfce|kde|gnome'

POSIX compatible:

echo "$XDG_DATA_DIRS" | sed 's/.*\(xfce\|kde\|gnome\).*/\1/'

To combine with checking XDG_CURRENT_DESKTOP:

if [ "$XDG_CURRENT_DESKTOP" = "" ]
then
  desktop=$(echo "$XDG_DATA_DIRS" | sed 's/.*\(xfce\|kde\|gnome\).*/\1/')
else
  desktop=$XDG_CURRENT_DESKTOP
fi

desktop=${desktop,,}  # convert to lower case
echo "$desktop"

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