Can't import libnftables.h on Raspberry Pi OS

I'm trying to use libnftables in C on Raspberry Pi OS. The built-in man page, libnftables(3), says to use #include <nftables/libnftables.h>. However, this header file doesn't seem to exist.

When compiling with GCC, I get the following:

libnftables_test.c:2:10: fatal error: nftables/libnftables.h: No such file or directory
    2 | #include <nftables/libnftables.h>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

Using find . -name "*libnftables*" -print from the root directory, I can see the library is installed, but still no header file.

./usr/lib/arm-linux-gnueabihf/libnftables.so.1
./usr/lib/arm-linux-gnueabihf/libnftables.so.1.0.0
./usr/share/man/man5/libnftables-json.5.gz
./usr/share/man/man3/libnftables.3.gz
./usr/share/doc/libnftables1
./var/lib/dpkg/info/libnftables1:armhf.list
./var/lib/dpkg/info/libnftables1:armhf.md5sums
./var/lib/dpkg/info/libnftables1:armhf.triggers
./var/lib/dpkg/info/libnftables1:armhf.shlibs

Using sudo apt install libnftables1 did not help.
For completeness, I tried these steps on an x86_64 Ubuntu machine (22.04), with similar results.

How can I install/find the header file described in the man page?

Solution

You need to install the the -dev version - i.e.

sudo apt install libnftables-dev

On Ubuntu, this includes:

$ dpkg-query -L libnftables-dev
/.
/usr
/usr/include
/usr/include/nftables
/usr/include/nftables/libnftables.h
/usr/lib
/usr/lib/x86_64-linux-gnu
/usr/lib/x86_64-linux-gnu/pkgconfig
/usr/lib/x86_64-linux-gnu/pkgconfig/libnftables.pc
/usr/share
/usr/share/doc
/usr/share/doc/libnftables-dev
/usr/share/doc/libnftables-dev/copyright
/usr/share/doc/libnftables-dev/examples
/usr/share/doc/libnftables-dev/examples/nft-buffer.c
/usr/share/doc/libnftables-dev/examples/nft-json-file.c
/usr/lib/x86_64-linux-gnu/libnftables.so
/usr/share/doc/libnftables-dev/changelog.Debian.gz

which has the include file you're missing.