SYNOPSIS section for library functions

The most important idioms are, mentioning the frequency in the OpenBSD base tree in parentheses:
filename (1360)
Before listing any function prototype, cite the header file or header files that need to be included to use the function.
function return type (3330)
Start each function prototype with one Ft macro line. Provide the function return type as arguments. No quoting is required, not even if the type consists of multiple words or contains pointer symbols (‘*’).
function_name (400)
After the Ft line, provide the function name in an Fo macro line.
argument_type argument_name” (1000)
After the Fo line, provide one Fa macro for each function argument. Since function arguments usually consist of a type and a name and there is a space between the type and the name, each function argument usually requires quoting.
After all arguments, close each Fo block by an explicit Fc block end macro.
#define macro definition (65)
Use the Fd macro to present preprocessor macro definitions.
variable_type variable_name (45)
Use the Vt macro for declarations of global variables.

A minimal example showing just the macros that are almost always needed:
.In sys/stat.h 
.Ft int 
.Fo chmod 
.Fa "const char *path" 
.Fa "mode_t mode" 

Style guide: the SYNOPSIS section for library functions
September 24, 2015