Re: [PATCH] document FIONREAD on pipe

["Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hello Patrick

On 09/24/2016 12:17 AM, Patrick McLean wrote:
> The FIONREAD ioctl can be used on a pipe to get the current amount of
> data in the pipe. This ioctl is currently only documented in tty_ioctl
> (4). This adds a blurb to the pipe(7) man page about this ioctl.

Thanks for the patch. In the end, I wrote something more extensive.
See below.

Cheers,

Michael

diff --git a/man7/pipe.7 b/man7/pipe.7
index 9977acc..b6a3007 100644
--- a/man7/pipe.7
+++ b/man7/pipe.7
@@ -143,6 +143,21 @@ operations.
 See
 .BR fcntl (2)
 for more information.
+
+The following
+.BR ioctl (2)
+operation, which can be applied to a file descriptor
+that refers to either end of a pipe,
+places a count of the number of unread bytes in the pipe in the
+.I int
+buffer pointed to by the final argument of the call:
+
+    ioctl(fd, FIONREAD, &nbytes);
+
+The
+.B FIONREAD
+operation is not specified in any standard,
+but is provided on many implementations.

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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