I want to write scripts on Ubuntu that will notify the user through a tool analogous to Growl on OS X (specifically, the
growlnotify command-line tool). What's the equivalent tool on Linux called?
There is a Growl port for Linux. Found here: Growl-for-linux
if you are using KDE, it is real easy! just use the kdialog command that is built-in to KDE, as in the example below:
kdialog --passivepopup "Example text"
if you happen to be using plain ubuntu, then you need to install the libnotify-bin package by issuing the following command:
sudo apt-get install libnotify-bin
and then you can send messages with like this:
notify-send "Example text"
the kdialog is a bit more interesting because it does way more than just send notifications from the command-line. you can actually build an interactive gui for your bash programs with it!
anyway, i hope this helps.