Document that truncate() can also be used to extend the size of a file.

From FreeBSD; ok deraadt@

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/libc/sys/truncate.2 b/lib/libc/sys/truncate.2
index 5c7128553d0..e07a0a353f1 100644
--- a/lib/libc/sys/truncate.2
+++ b/lib/libc/sys/truncate.2
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: truncate.2,v 1.7 2000/04/15 11:46:04 aaron Exp $
+.\"	$OpenBSD: truncate.2,v 1.8 2000/07/21 21:52:14 naddy Exp $
 .\"	$NetBSD: truncate.2,v 1.7 1995/02/27 12:39:00 cgd Exp $
 .\"
 .\" Copyright (c) 1983, 1991, 1993
@@ -40,7 +40,7 @@
 .Sh NAME
 .Nm truncate ,
 .Nm ftruncate
-.Nd truncate a file to a specified length
+.Nd truncate or extend a file to a specified length
 .Sh SYNOPSIS
 .Fd #include <unistd.h>
 .Ft int
@@ -53,11 +53,14 @@ causes the file named by
 .Fa path
 or referenced by
 .Fa fd
-to be truncated to at most
+to be truncated or extended to
 .Fa length
-bytes in size.  If the file previously
+bytes in size.  If the file
 was larger than this size, the extra data
 is lost.
+If the file was smaller than this size,
+it will be extended as if by writing bytes
+with the value zero.
 With
 .Fn ftruncate ,
 the file must be open for writing.
@@ -123,6 +126,10 @@ is not open for writing.
 .Sh BUGS
 These calls should be generalized to allow ranges
 of bytes in a file to be discarded.
+.Pp
+Use of
+.Fn truncate
+to extend a file is not portable.
 .Sh HISTORY
 The
 .Fn truncate