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"chmod -w file" now complains if file is still writable afterwards
From: |
Paul Eggert |
Subject: |
"chmod -w file" now complains if file is still writable afterwards |
Date: |
Wed, 04 May 2005 10:30:24 -0700 |
User-agent: |
Gnus/5.1006 (Gnus v5.10.6) Emacs/21.4 (gnu/linux) |
For quite some time I've been annoyed that "chmod -w file" can leave
the file writeable afterwards, if your umask is restrictive. You're
supposed to use "chmod a-w file" if you really want the file to be
unwriteable.
This is a common trap for novices to fall into, and I think it'd be
better if chmod diagnosed the mistake, in addition to performing the
requested action. I just checked POSIX, and it allows "chmod" to
diagnose errors like "chmod -w file" so I installed the following
patch.
Another option would be for "chmod -w file" to silently adjust itself
to behave like "chmod a-w file"; POSIX allows that too. If you think
that's better I could install a patch along those lines instead.
2005-05-04 Paul Eggert <address@hidden>
* NEWS: chmod -w now complains if it differs from chmod a-w.
* src/chmod.c: Include quotearg.h.
(diagnose_surprises): New var.
(process_file): Diagnose surprises. Simplify the logic a bit,
while we're at it.
(main): Prepare to diagnose surprises. Remove useless code for
'-' option.
* tests/chmod/Makefile.am (TESTS): Add umask-x.
* tests/chmod/umask-x: New file.
Index: NEWS
===================================================================
RCS file: /fetish/cu/NEWS,v
retrieving revision 1.284
diff -p -u -r1.284 NEWS
--- NEWS 2 May 2005 18:40:20 -0000 1.284
+++ NEWS 4 May 2005 17:18:47 -0000
@@ -124,6 +124,9 @@ GNU coreutils NEWS
** New features
+ chmod -w now complains if its behavior differs from what chmod a-w
+ would do, and similarly for chmod -r, chmod -x, etc.
+
join now supports a NUL field separator, e.g., "join -t '\0'".
join now detects and reports incompatible options, e.g., "join -t x -t y",
Index: doc/coreutils.texi
===================================================================
RCS file: /fetish/cu/doc/coreutils.texi,v
retrieving revision 1.254
diff -p -u -r1.254 coreutils.texi
--- doc/coreutils.texi 2 May 2005 18:41:12 -0000 1.254
+++ doc/coreutils.texi 4 May 2005 17:18:48 -0000
@@ -8451,9 +8451,11 @@ recursive directory traversals.
If used, @var{mode} specifies the new permissions.
For details, see the section on @ref{File permissions}.
-In the extremely rare cases where @var{mode} has leading @samp{-}, a
-portable script should use @option{--} first, e.g., @samp{chmod -- -w
-file}. Typically, though, @samp{chmod a-w file} is preferable.
+If you really want @var{mode} to have a leading @samp{-}, you should
+use @option{--} first, e.g., @samp{chmod -- -w file}. Typically,
+though, @samp{chmod a-w file} is preferable, and @command{chmod -w
+file} (without the @option{--}) complains if it behaves differently
+from what @samp{chmod a-w file} would do.
The program accepts the following options. Also see @ref{Common options}.
Index: src/chmod.c
===================================================================
RCS file: /fetish/cu/src/chmod.c,v
retrieving revision 1.109
diff -p -u -r1.109 chmod.c
--- src/chmod.c 28 Apr 2005 16:29:59 -0000 1.109
+++ src/chmod.c 4 May 2005 17:18:48 -0000
@@ -29,6 +29,7 @@
#include "filemode.h"
#include "modechange.h"
#include "quote.h"
+#include "quotearg.h"
#include "root-dev-ino.h"
#include "xfts.h"
@@ -72,6 +73,11 @@ static bool recurse;
/* If true, force silence (no error messages). */
static bool force_silent;
+/* If true, diagnose surprises from naive misuses like "chmod -r file".
+ POSIX allows diagnostics here, as portable code is supposed to use
+ "chmod -- -r file". */
+static bool diagnose_surprises;
+
/* Level of verbosity. */
static enum Verbosity verbosity = V_off;
@@ -176,10 +182,10 @@ process_file (FTS *fts, FTSENT *ent)
char const *file_full_name = ent->fts_path;
char const *file = ent->fts_accpath;
const struct stat *file_stats = ent->fts_statp;
+ mode_t old_mode IF_LINT (= 0);
mode_t new_mode IF_LINT (= 0);
bool ok = true;
- bool do_chmod;
- bool symlink_changed = true;
+ bool chmod_succeeded = false;
switch (ent->fts_info)
{
@@ -206,48 +212,65 @@ process_file (FTS *fts, FTSENT *ent)
break;
}
- do_chmod = ok;
-
- if (do_chmod && ROOT_DEV_INO_CHECK (root_dev_ino, file_stats))
+ if (ok && ROOT_DEV_INO_CHECK (root_dev_ino, file_stats))
{
ROOT_DEV_INO_WARN (file_full_name);
ok = false;
- do_chmod = false;
}
- if (do_chmod)
+ if (ok)
{
- new_mode = mode_adjust (file_stats->st_mode, change, umask_value);
+ old_mode = file_stats->st_mode;
+ new_mode = mode_adjust (old_mode, change, umask_value);
- if (S_ISLNK (file_stats->st_mode))
- symlink_changed = false;
- else
+ if (! S_ISLNK (old_mode))
{
- ok = (chmod (file, new_mode) == 0);
-
- if (! (ok | force_silent))
- error (0, errno, _("changing permissions of %s"),
- quote (file_full_name));
+ if (chmod (file, new_mode) == 0)
+ chmod_succeeded = true;
+ else
+ {
+ if (! force_silent)
+ error (0, errno, _("changing permissions of %s"),
+ quote (file_full_name));
+ ok = false;
+ }
}
}
if (verbosity != V_off)
{
- bool changed =
- (ok && symlink_changed
- && mode_changed (file, file_stats->st_mode, new_mode));
+ bool changed = (chmod_succeeded
+ && mode_changed (file, old_mode, new_mode));
if (changed || verbosity == V_high)
{
enum Change_status ch_status =
(!ok ? CH_FAILED
- : !symlink_changed ? CH_NOT_APPLIED
+ : !chmod_succeeded ? CH_NOT_APPLIED
: !changed ? CH_NO_CHANGE_REQUESTED
: CH_SUCCEEDED);
describe_change (file_full_name, new_mode, ch_status);
}
}
+ if (chmod_succeeded & diagnose_surprises)
+ {
+ mode_t naively_expected_mode = mode_adjust (old_mode, change, 0);
+ if (new_mode & ~naively_expected_mode)
+ {
+ char new_perms[11];
+ char naively_expected_perms[11];
+ mode_string (new_mode, new_perms);
+ mode_string (naively_expected_mode, naively_expected_perms);
+ new_perms[10] = naively_expected_perms[10] = '\0';
+ error (0, 0,
+ _("%s: new permissions are %s, not %s"),
+ quotearg_colon (file_full_name),
+ new_perms + 1, naively_expected_perms + 1);
+ ok = false;
+ }
+ }
+
if ( ! recurse)
fts_set (fts, ent, FTS_SKIP);
@@ -354,10 +377,10 @@ main (int argc, char **argv)
atexit (close_stdout);
- recurse = force_silent = false;
+ recurse = force_silent = diagnose_surprises = false;
while ((c = getopt_long (argc, argv,
- "Rcfvr::w::x::X::s::t::u::g::o::a::,::+::-::=::",
+ "Rcfvr::w::x::X::s::t::u::g::o::a::,::+::=::",
long_options, NULL))
!= -1)
{
@@ -375,8 +398,11 @@ main (int argc, char **argv)
case 'a':
case ',':
case '+':
- case '-':
case '=':
+ /* Support nonportable uses like "chmod -w", but diagnose
+ surprises due to umask confusion. Even though "--", "--r",
+ etc., are valid modes, there is no "case '-'" here since
+ getopt_long reserves leading "--" for long options. */
{
/* Allocate a mode string (e.g., "-rwx") by concatenating
the argument containing this option. If a previous mode
@@ -395,6 +421,8 @@ main (int argc, char **argv)
mode[mode_len] = ',';
strcpy (mode + mode_comma_len, arg);
mode_len = new_mode_len;
+
+ diagnose_surprises = true;
}
break;
case NO_PRESERVE_ROOT:
Index: tests/chmod/Makefile.am
===================================================================
RCS file: /fetish/cu/tests/chmod/Makefile.am,v
retrieving revision 1.8
diff -p -u -r1.8 Makefile.am
--- tests/chmod/Makefile.am 24 Sep 2004 23:34:41 -0000 1.8
+++ tests/chmod/Makefile.am 4 May 2005 17:18:48 -0000
@@ -1,7 +1,7 @@
## Process this file with automake to produce Makefile.in -*-Makefile-*-.
AUTOMAKE_OPTIONS = 1.4 gnits
-TESTS = no-x equals equal-x c-option setgid usage
+TESTS = no-x equals equal-x c-option setgid umask-x usage
EXTRA_DIST = $(TESTS)
TESTS_ENVIRONMENT = \
PATH="`pwd`/../../src$(PATH_SEPARATOR)$$PATH"
--- /dev/null 2003-03-18 13:55:57 -0800
+++ tests/chmod/umask-x 2005-05-04 10:12:38 -0700
@@ -0,0 +1,36 @@
+#!/bin/sh
+# Test that chmod -x file reports an error if the result is executable.
+
+if test "$VERBOSE" = yes; then
+ set -x
+ chmod --version
+fi
+
+. $srcdir/../lang-default
+
+pwd=`pwd`
+tmp=minus.$$
+trap 'status=$?; cd $pwd; rm -rf $tmp && exit $status' 0
+trap '(exit $?); exit' 1 2 13 15
+
+framework_failure=0
+mkdir $tmp || framework_failure=1
+cd $tmp || framework_failure=1
+
+if test $framework_failure = 1; then
+ echo "$0: failure in testing framework" 1>&2
+ (exit 1); exit 1
+fi
+
+fail=0
+
+touch file
+chmod 755 file
+(umask 77 && chmod -x file) 2>/dev/null && fail=1
+
+if test $framework_failure = 1; then
+ echo "$0: failure in testing framework" 1>&2
+ fail=1
+fi
+
+(exit $fail); exit $fail
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