Man pages are the Gold Standard for C language documentation on Unix and Linux OS. Note that depending on which OS you're talking about some details may vary, so it's best to get your info from the manual for your OS (Linux).
Obviously the quickest way to get that info is from your local Linux command line via the "
man" command. You can get help on "man" using the command "
man man", as that brings up the manual on
man itself. Online, a good reference is die.net:
https://linux.die.net/man/
The
man help facility is considered archaic as it's not the best viewer for long complex functions or function libraries, so there's also the hyperlink-navigable
info command.