/etc/init.d/functions ulimit line question

[grendel42]

On my Red Hat Enterprise Linux 5/6 (4 has it too but without the corelimit variable) servers there is a line (in /etc/init.d/functions) that looks like this:
corelimit="ulimit -S -c ${DAEMON_COREFILE_LIMIT:-0}"

Now DAEMON_COREFILE_LIMIT is defined in /etc/sysconfig/init (but not defined by default).
So DAEMON_COREFILE_LIMIT is normally not defined.

So my question is what is the :-0 syntax? I'm not familiar with that, but I suppose it has something to do with if that variable isn't defined then set it to 0. This may just be more of a generic scripting question, but I wasn't sure if other distros even had this line so I stuck with the RHEL forum.
Can you provide a link that describes this specific syntax? I wouldn't even know what to google.

Thanks!

[grendel42]

Think I answered my own question:
www dot techtalkz dot com/gentoo-linux/262060-what-does-colon-minus-operator-do-runscript-shell.html