V4/man/man2/unlink.2

.th UNLINK II 8/5/73
.sh NAME
unlink \*- remove directory entry
.sh SYNOPSIS
(unlink = 10.)
.br
.bt B
sys  unlink; name
.s3
unlink(name)
.br
char *name;
.ft R
.sh DESCRIPTION
.it Name
points to a null-terminated string.
.it Unlink
removes the entry for the file pointed to by
.it name
from its directory.
If this entry was the last link to the file,
the contents of the file are freed and the file is destroyed.
If, however, the file was open in any process, the actual
destruction is delayed until it is closed, even though
the directory entry has disappeared.
.sh "SEE ALSO"
rm(I), rmdir(I), link(II)
.sh DIAGNOSTICS
The error bit
(c-bit) is set to indicate that the file does not
exist or that its directory cannot be written.
Write permission is not required on the file itself.
It is also illegal to unlink a directory
(except for the super-user).
From C, a \*-1 return indicates an error.