[CentOS] how to set/add environment variables and make file search priority on centos

Hi,

I'm using centos 6.8. In order to build gstreamer 1.8.2, I install some new packages, such as python 2.7 and yasm. And cerbero is the build system for gstreamer, and downloads some new packages from network and build them, such libtool, glib.

All new packages are downloaded, built and installed in my custom directory.

I want cerbero use the new packages in my custom directory. It mean that, linux will search my custom directory first, and will search others if target program or lib is not found.

How to make search priority for programs, static libs, shared libs, and pkgconfig files?

Thanks!

Regards

Andrew