Bash tool to put an icon on taskbar?

Question

I am trying to create a tiny application on my Ubuntu machine. What I want to do is put to an icon on my taskbar beside the volume, and internet connectivity options. I understand that there is a notify-send command in bash that I can use, or even switch to Qt but that seems to be an overkill for the problem. Concretely, is there a way to create an icon on Ubuntu taskbar with bash, and change its color or text periodically?

Answer 1

For a very shell friendly way to quickly get tray apps working use yad (specifically yad --notification). It allows you to dynamically change icons, set click event handlers and build a custom context menu. For example:

yad --notification --command='echo hello world' --image=myicon.png

Will echo 'hello world' on click. Or:

yad --notification --command='echo hello world' --image=myicon.png --listen

Will read it's standard input waiting for commands to change icons, change visibility, open menu, trigger action and more.

Answer 2

More advanced example using yad.

Shows how to handle click in the same script and how to change the icon on the click. Also shows how to create a simple update loop and exit cleanly.

# stop on error (always good practice)
set -e 

# create a FIFO file, used to manage the I/O redirection from shell
PIPE=$(mktemp -u --tmpdir ${0##*/}.XXXXXXXX)
mkfifo $PIPE
export PIPE

# attach a file descriptor to the file
exec 3<> $PIPE

# add handler to manage process shutdown
function on_exit() {
    # send command to yad through pipe
    echo "quit" >&3
    rm -f $PIPE
}
trap on_exit EXIT

function update_icon() {
    exec 3<> $PIPE         # just in case
    echo "icon:/path/to/some/icon" >&3
}
export -f update_icon     

# add handler for tray icon left click
function on_click() {
    exec 3<> $PIPE         # required
    echo "clicked"
    echo "icon:/path/to/icon" >&3
    update_icon
}
export -f on_click

# add handler for right click menu Quit entry function 
on_quit() { 
    # signal to the script that it should end when this file is created
    echo "quit" > ./quit.txt 
    exec 3<> $PIPE # required 
    echo "quit" >&3 
} 
export -f on_quit 

# Use a file to indicate a quit command to the script
# Make sure it is gone before we start the program to avoid immediate exit
rm -f quit.txt 

# create the notification icon with right click menu and Quit option
yad --notification                  \
    --listen                        \
    --image="/path/to/icon"  \
    --text="demo tray icon"   \
    --menu="Quit!bash -c on_quit" \
    --no-middle \
    --command="bash -c on_click" <&3 &

# allow user to end the loop from icon right click Quit menu option
while [ ! -f "quit.txt" ]; do 
    #echo "Press [CTRL+C] to stop.."
    update_icon
    sleep 60
done
# clean up after quit
rm quit.txt

Based on:

• https://code.google.com/archive/p/yad/wikis/NotificationIcon.wiki
• https://sourceforge.net/p/yad-dialog/wiki/NotificationIcon/
• https://groups.google.com/g/yad-common/c/DT8q1vJ-yOQ

I'm not a bash expert, so fixes are welcome.

yad is available for many distros as a standard package. On Debian for example it can be installed by apt install yad.