In case pkgconfig is not available on the system, an alternate helper script is provided: libupsclient-config.

It will be installed in the same directory as NUT client programs (BINDIR), providing that you have enabled the --with-dev flag to the configure script.

The usage is about the same as pkg-config and similar tools.

To get CFLAGS, use:

$ libupsclient-config --cflags

To get LD_FLAGS, use:

$ libupsclient-config --libs

References: libupsclient-config(1) manual page,