13.4 pkg-req

If your port needs to determine if it should install or not, you can create a pkg-req ``requirements'' script. It will be invoked automatically at installation/de-installation time to determine whether or not installation/de-installation should proceed.

The script will be run at installation time by pkg_add(1) as pkg-req ${PKGNAME} INSTALL. At de-installation time it will be run by pkg_delete(1) as pkg-req ${PKGNAME} DEINSTALL.