capng_get_caps_process will get the capabilities and bounding set of the pid stored inside libcap-ng's state table. The default is the pid of the running process. This can be changed by using the capng_setpid function.
This returns 0 on success and -1 on failure.
If you are doing multi-threaded programming, calling this function will only get capabilities on the calling thread. If you want to get overall capabilities for a multi-threaded process, you can only do that before creating any threads. Afterwards, threads may be able to independantly set capabilities.