.nf
.B #include <fcntl.h>
.P
-.BI "int fcntl(int " fd ", int " op ", ... /* " arg " */ );"
+.BI "int fcntl(int " fd ", int " op ", ...);"
.fi
.SH DESCRIPTION
.BR fcntl ()
The operation is determined by
.IR op .
.P
-.BR fcntl ()
-can take an optional third argument.
-Whether or not this argument is required is determined by
-.IR op .
-The required argument type is indicated in parentheses after each
-.I op
-name (in most cases, the required type is
-.IR int ,
-and we identify the argument using the name
-.IR arg ),
-or
-.I void
-is specified if the argument is not required.
-.P
Certain of the operations below are supported only since a particular
Linux kernel version.
The preferred method of checking whether the host kernel supports