path: root/doc/hooks/cernlib.section.md

# CERNLIB {#cernlib-hook}

This hook sets the `CERN`, `CERN_LEVEL`, and `CERN_ROOT` environment variables. They are part of [CERNLIB's build system](https://cernlib.web.cern.ch/install/install.html) and are needed for some programs to compile correctly.