Make read(2) return EISDIR on directories.

Years ago Theo made read(2) return 0 on directories, instead of dumping
the directory content.  Another behavior is allowed as an extension by
POSIX, returning an EISDIR error, as used on a few other systems.  This
behavior is deemed more useful as it helps spotting errors.  This
implies that it might break some setups.

Ports bulk builds by ajacoutot@ and naddy@, ok millert@ bluhm@ naddy@
deraadt@

1 files changed, 6 insertions, 4 deletions

diff --git a/lib/libc/sys/read.2 b/lib/libc/sys/read.2
index 48e227354ee..07269801fe7 100644
--- a/lib/libc/sys/read.2
+++ b/lib/libc/sys/read.2
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: read.2,v 1.35 2015/02/05 02:33:09 schwarze Exp $
+.\"	$OpenBSD: read.2,v 1.36 2016/09/30 10:53:11 jca Exp $
 .\"	$NetBSD: read.2,v 1.6 1995/02/27 12:35:47 cgd Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
@@ -30,7 +30,7 @@
 .\"
 .\"     @(#)read.2	8.4 (Berkeley) 2/26/94
 .\"
-.Dd $Mdocdate: February 5 2015 $
+.Dd $Mdocdate: September 30 2016 $
 .Dt READ 2
 .Os
 .Sh NAME
@@ -152,13 +152,15 @@ is not a valid file or socket descriptor open for reading.
 Part of
 .Fa buf
 points outside the process's allocated address space.
-.It Bq Er EIO
-An I/O error occurred while reading from the file system.
 .It Bq Er EINTR
 A read from a slow device
 (i.e. one that might block for an arbitrary amount of time)
 was interrupted by the delivery of a signal
 before any data arrived.
+.It Bq Er EIO
+An I/O error occurred while reading from the file system.
+.It Bq Er EISDIR
+The underlying file is a directory.
 .El
 .Pp
 In addition,