There's another possible solution if you want it to work regardless of
username, by finding the active user of the X display, using
ConsoleKit (the command ck-list-sessions
). Assuming the below script
is run as root, it will show a zenity message to the current active
user on your computer:
#!/bin/bash
ACTIVE=$(ck-list-sessions | awk -F' = ' '
function f(){if(A=="TRUE"){P=U"\t"D;gsub("'"'"'","",P);print P}}
$1=="\tunix-user"{U=$2}
$1=="\tx11-display"{D=$2}
$1=="\tactive"{A=$2}
END{f()} /^[^\t]/{f()}
')
USERID=${ACTIVE% *} # tab
USERNAME=$(getent passwd $USERID|cut -f1 -d':')
DISPLAY=${ACTIVE#* } # tab
DISPLAY="$DISPLAY" su $USERNAME -c "zenity --error --text='Something very bad has happened!'"
The little awk script is just for parsing ck-list-sessions and
outputting the username and display of the user that is active (could
also require that it's a local connection if you want to exclude ssh
-X users, if you want).
(I use this in a backup script that runs on plugging in a USB
drive.)