From 3d53e7fe1c31aa440cc9708c7c51db6b78c07653 Mon Sep 17 00:00:00 2001
From: =?utf8?q?P=C3=A1draig=20Brady?= <P@draigBrady.com>
Date: Thu, 12 Apr 2012 12:47:30 +0100
Subject: [PATCH 1/1] cp: change --attributes-only to not truncate existing files
* src/copy.c (copy_reg): Don't truncate an existing file,
to support copying attributes between existing files.
The original use case only considered creating new files,
and it would be a very unusual use case to be relying
on the truncating behavior.
* doc/coreutils.texi (cp invocation): Mention the non
truncating behavior.
* tests/cp/attr-existing: A new test to ensure O_TRUNC skipped.
* tests/Makefile.am: Reference the new test.
---
doc/coreutils.texi | 6 +++---
src/copy.c | 4 +++-
tests/Makefile.am | 1 +
tests/cp/attr-existing | 29 +++++++++++++++++++++++++++++
4 files changed, 36 insertions(+), 4 deletions(-)
create mode 100755 tests/cp/attr-existing
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 510abb9..1fbf051 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7649,9 +7649,9 @@ Equivalent to @option{-dR --preserve=all} with the reduced diagnostics.
@itemx --attributes-only
@opindex --attributes-only
-Preserve the specified attributes of the original files in the copy,
-but do not copy any data. See the @option{--preserve} option for
-controlling which attributes to copy.
+Copy only the specified attributes of the source file to the destination.
+If the destination already exists, do not alter its contents.
+See the @option{--preserve} option for controlling which attributes to copy.
@item -b
@itemx @w{@kbd{--backup}[=@var{method}]}
diff --git a/src/copy.c b/src/copy.c
index f63a726..414fbe0 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -826,7 +826,9 @@ copy_reg (char const *src_name, char const *dst_name,
by the specs for both cp and mv. */
if (! *new_dst)
{
- dest_desc = open (dst_name, O_WRONLY | O_TRUNC | O_BINARY);
+ int open_flags =
+ O_WRONLY | O_BINARY | (x->data_copy_required ? O_TRUNC : 0);
+ dest_desc = open (dst_name, open_flags);
dest_errno = errno;
/* When using cp --preserve=context to copy to an existing destination,
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 011051a..4d73a92 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -320,6 +320,7 @@ TESTS = \
chown/separator \
cp/abuse \
cp/acl \
+ cp/attr-existing \
cp/backup-1 \
cp/backup-dir \
cp/backup-is-src \
diff --git a/tests/cp/attr-existing b/tests/cp/attr-existing
new file mode 100755
index 0000000..9cf0ffc
--- /dev/null
+++ b/tests/cp/attr-existing
@@ -0,0 +1,29 @@
+#!/bin/sh
+# Make sure cp --attributes-only doesn't truncate existing data
+
+# Copyright 2012 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+print_ver_ cp
+
+printf '1' > file1
+printf '2' > file2
+printf '2' > file2.exp
+
+cp --attributes-only file1 file2 || fail=1
+cmp file2 file2.exp || fail=1
+
+Exit $fail
--
1.7.2.5