How do I find the current system timezone?

Question

On Linux, I need to find the currently configured timezone as an Olson location. I want my (C or C++) code to be portable to as many Linux systems as possible.

For e

Answer 1

FWIW, RHEL/Fedora/CentOS have /etc/sysconfig/clock:

ZONE="Europe/Brussels"
UTC=true
ARC=false