update software

[Waqas Toor]

hi ,
I am writing a script that will first check for the update and then
install the latest version by downloading it and building it from
source.
now my question is this, is there any way that in BASH i get to know
about the latest version
i.e. software is p3scan and the latest version is 2.3
now how to know about that through bash ??? help me out

Regards
Waqas