diff options
Diffstat (limited to 'lib/libc')
| -rw-r--r-- | lib/libc/sys/ioctl.2 | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/lib/libc/sys/ioctl.2 b/lib/libc/sys/ioctl.2 index 57d50c2..bab7b47 100644 --- a/lib/libc/sys/ioctl.2 +++ b/lib/libc/sys/ioctl.2 @@ -29,7 +29,7 @@ .\" .\" $FreeBSD$ .\" -.Dd July 14, 2007 +.Dd May 11, 2010 .Dt IOCTL 2 .Os .Sh NAME @@ -80,6 +80,30 @@ Macros and defines used in specifying an ioctl .Fa request are located in the file .In sys/ioctl.h . +.Sh GENERIC IOCTLS +Some generic ioctls are not implemented for all types of file +descriptors. +These include: +.Bl -tag -width "xxxxxx" +.It Dv FIONREAD int +Get the number of bytes that are immediately available for reading. +.It Dv FIONWRITE int +Get the number of bytes in the descriptor's send queue. +These bytes are data which has been written to the descriptor but +which are being held by the kernel for further processing. +The nature of the required processing depends on the underlying device. +For TCP sockets, these bytes have not yet been acknowledged by the +other side of the connection. +.It Dv FIONSPACE int +Get the free space in the descriptor's send queue. +This value is the size of the send queue minus the number of bytes +being held in the queue. +Note: while this value represents the number of bytes that may be +added to the queue, other resource limitations may cause a write +not larger than the send queue's space to be blocked. +One such limitation would be a lack of network buffers for a write +to a network connection. +.El .Sh RETURN VALUES If an error has occurred, a value of -1 is returned and .Va errno |
