update a software
 

Hi,everyone,
I want to write a software that can help me to update other softwares automaticlly, anyone could give me some advice to do so? May be some advice about what knowledge I need to know, thank you!

These things already exist, many distros already have package managers that can be set to auto-update. Are you trying to write a unified tool or one for a particular distro? Which language do you plan to write it in?

I guess you could code it in C/C++ if you're really determined to do so. Keeping a repository database should give you some headaches, not to mention updating it and so.
You might find the following information useful:
http://en.wikipedia.org/wiki/Package_manager