3 element {struct group} {char*} gr_name
4 element {struct group} gid_t gr_gid
5 element {struct group} {char**} gr_mem
11 function {struct group*} getgrgid (gid_t)
12 function {struct group*} getgrnam (const char*)
14 function int getgrgid_r (gid_t, struct group*, char *, size_t, struct group**)
15 function int getgrnam_r (const char *, struct group *, char *, size_t, struct group**)
16 function {struct group*} getgrent (void)
17 function void endgrent (void)
18 function void setgrent (void)