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chmod: add notations +40, 00440, etc.
* NEWS: Document this. * doc/perm.texi (Operator Numeric Modes): New section. (Numeric Modes, Directory Setuid and Setgid): Document new behavior. * src/chmod.c (usage): Document new behavior. (main): Support new options -0, -1, etc. * tests/chmod/setgid: Test these new features.
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Paul Eggert
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15
NEWS
15
NEWS
@ -4,6 +4,21 @@ GNU coreutils NEWS -*- outline -*-
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** New features
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As a GNU extension, 'chmod', 'mkdir', and 'install' now accept operators
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'-', '+', '=' followed by octal modes; for example, 'chmod +40 FOO' enables
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and 'chmod -40 FOO' disables FOO's group-read permissions. Operator
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numeric modes can be combined with symbolic modes by separating them with
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commas; for example, =0,u+r clears all permissions except for enabling
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user-read permissions. Unlike ordinary numeric modes, operator numeric
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modes do not preserve directory setuid and setgid bits; for example,
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'chmod =0 FOO' clears all of FOO's permissions, including setuid and setgid.
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Also, ordinary numeric modes with five or more digits no longer preserve
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setuid and setgid bits, so that 'chmod 00755 FOO' now clears FOO's setuid
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and setgid bits. This allows scripts to be portable to other systems which
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lack the GNU extension mentioned previously, and where ordinary numeric
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modes do not preserve directory setuid and setgid bits.
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dd now accepts the count_bytes, skip_bytes iflags and the seek_bytes
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oflag, to more easily allow processing portions of a file.
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@ -17,6 +17,7 @@ symbolic form or as an octal number.
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* Mode Structure:: Structure of file mode bits.
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* Symbolic Modes:: Mnemonic representation of file mode bits.
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* Numeric Modes:: File mode bits as octal numbers.
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* Operator Numeric Modes:: ANDing, ORing, and setting modes octally.
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* Directory Setuid and Setgid:: Set-user-ID and set-group-ID on directories.
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@end menu
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@ -495,13 +496,16 @@ alternative to giving a symbolic mode, you can give an octal (base 8)
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number that represents the mode.
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This number is always interpreted in octal; you do not have to add a
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leading @samp{0}, as you do in C. Mode @samp{0055} is the same as
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mode @samp{55}.
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mode @samp{55}. (However, modes of five digits or more, such as
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@samp{00055}, are sometimes special. @xref{Directory Setuid and Setgid}.)
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A numeric mode is usually shorter than the corresponding symbolic
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mode, but it is limited in that normally it cannot take into account the
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previous file mode bits; it can only set them absolutely.
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(As discussed in the next section, the set-user-ID and set-group-ID
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bits of directories are an exception to this general limitation.)
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The set-user-ID and set-group-ID bits of directories are an exception
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to this general limitation; @xref{Directory Setuid and Setgid}.
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Also, operator numeric modes can take previous file mode bits into
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account; @xref{Operator Numeric Modes}.
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The permissions granted to the user,
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to other users in the file's group,
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@ -541,6 +545,26 @@ For example, numeric mode @samp{4755} corresponds to symbolic mode
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@samp{ug=rw,o=r}. Numeric mode @samp{0} corresponds to symbolic mode
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@samp{a=}.
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@node Operator Numeric Modes
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@section Operator Numeric Modes
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An operator numeric mode is a numeric mode that is prefixed by a
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@samp{-}, @samp{+}, or @samp{=} operator, which has the same
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interpretation as in symbolic modes. For example, @samp{+440} enables
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read permission for the file's owner and group, @samp{-1} disables
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execute permission for other users, and @samp{=600} clears all
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permissions except for enabling read-write permissions for the file's
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owner. Operator numeric modes can be combined with symbolic modes by
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separating them with a comma; for example, @samp{=0,u+r} clears all
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permissions except for enabling read permission for the file's owner.
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The commands @samp{chmod =755 @var{dir}} and @samp{chmod 755
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@var{dir}} differ in that the former clears the directory @var{dir}'s
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setuid and setgid bits, whereas the latter preserves them.
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@xref{Directory Setuid and Setgid}.
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Operator numeric modes are a @acronym{GNU} extension.
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@node Directory Setuid and Setgid
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@section Directories and the Set-User-ID and Set-Group-ID Bits
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@ -559,8 +583,10 @@ bits of directories. If commands like @command{chmod} and
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mechanisms would be less convenient and it would be harder to share
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files. Therefore, a command like @command{chmod} does not affect the
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set-user-ID or set-group-ID bits of a directory unless the user
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specifically mentions them in a symbolic mode, or sets them in
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a numeric mode. For example, on systems that support
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specifically mentions them in a symbolic mode, or uses an operator
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numeric mode such as @samp{=755}, or sets them in a numeric mode, or
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clears them in a numeric mode that has five or more octal digits.
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For example, on systems that support
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set-group-ID inheritance:
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@example
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@ -582,22 +608,32 @@ explicitly in the symbolic or numeric modes, e.g.:
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@example
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# These commands try to set the set-user-ID
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# and set-group-ID bits of the subdirectories.
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mkdir G H
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mkdir G
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chmod 6755 G
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chmod u=rwx,go=rx,a+s H
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mkdir -m 6755 I
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chmod +6000 G
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chmod u=rwx,go=rx,a+s G
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mkdir -m 6755 H
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mkdir -m +6000 I
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mkdir -m u=rwx,go=rx,a+s J
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@end example
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If you want to try to clear these bits, you must mention them
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explicitly in a symbolic mode, e.g.:
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explicitly in a symbolic mode, or use an operator numeric mode, or
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specify a numeric mode with five or more octal digits, e.g.:
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@example
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# This command tries to clear the set-user-ID
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# These commands try to clear the set-user-ID
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# and set-group-ID bits of the directory D.
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chmod a-s D
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chmod -6000 D
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chmod =755 D
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chmod 00755 D
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@end example
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This behavior is a @acronym{GNU} extension. Portable scripts should
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not rely on requests to set or clear these bits on directories, as
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@acronym{POSIX} allows implementations to ignore these requests.
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The @acronym{GNU} behavior with numeric modes of four or fewer digits
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is intended for scripts portable to systems that preserve these bits;
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the behavior with numeric modes of five or more digits is for scripts
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portable to systems that do not preserve the bits.
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@ -398,7 +398,7 @@ With --reference, change the mode of each FILE to that of RFILE.\n\
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fputs (VERSION_OPTION_DESCRIPTION, stdout);
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fputs (_("\
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\n\
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Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+'.\n\
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Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.\n\
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"), stdout);
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emit_ancillary_info ();
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}
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@ -430,7 +430,8 @@ main (int argc, char **argv)
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recurse = force_silent = diagnose_surprises = false;
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while ((c = getopt_long (argc, argv,
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"Rcfvr::w::x::X::s::t::u::g::o::a::,::+::=::",
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("Rcfvr::w::x::X::s::t::u::g::o::a::,::+::=::"
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"0::1::2::3::4::5::6::7::"),
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long_options, NULL))
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!= -1)
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{
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@ -449,6 +450,8 @@ main (int argc, char **argv)
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case ',':
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case '+':
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case '=':
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case '0': case '1': case '2': case '3':
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case '4': case '5': case '6': case '7':
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/* Support nonportable uses like "chmod -w", but diagnose
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surprises due to umask confusion. Even though "--", "--r",
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etc., are valid modes, there is no "case '-'" here since
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@ -1,6 +1,7 @@
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#!/bin/sh
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# Make sure GNU chmod works the same way as those of Solaris, HPUX, AIX
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# wrt directories with the setgid bit set.
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# on directories with the setgid bit set. Also, check that the GNU octal
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# notations work.
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# Copyright (C) 2001-2012 Free Software Foundation, Inc.
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@ -21,7 +22,7 @@
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print_ver_ chmod
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umask 0
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mkdir d || framework_failure_
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mkdir -m 755 d || framework_failure_
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chmod g+s d 2> /dev/null && env -- test -g d ||
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{
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@ -40,9 +41,24 @@ chmod g+s d 2> /dev/null && env -- test -g d ||
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env -- test -g d ||
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skip_ 'cannot create setgid directories'
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for mode in \
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+ - g-s 00755 000755 =755 -2000 -7022 755 0755 \
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+2000 -5022 =7777,-5022
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do
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chmod $mode d || fail=1
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chmod 755 d
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case $mode in
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g-s | 00*755 | =755 | -2000 | -7022)
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expected_mode=drwxr-xr-x ;;
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*) expected_mode=drwxr-sr-x ;;
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esac
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ls_output=`ls -ld d`
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case $ls_output in
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$expected_mode*) ;;
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*) fail=1 ;;
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esac
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case `ls -ld d` in drwxr-sr-x*);; *) fail=1;; esac
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chmod =2755 d || fail=1
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done
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Exit $fail
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