LINK(2) System Calls Manual LINK(2)
link - link to a file
char *name1, *name2;
A link to name1 is created; the link has the name name2. Either name
may be an arbitrary path name.
Zero is returned when a link is made; -1 is returned when name1 cannot
be found; when name2 already exists; when the directory of name2 cannot
be written; when an attempt is made to link to a directory by a user
other than the super-user; when an attempt is made to link to a file on
another file system; when a file has too many links.
(link = 9.)
sys link; name1; name2