Michael Stone <[EMAIL PROTECTED]> wrote: > On Tue, Apr 22, 2008 at 07:59:07PM +0400, sergio wrote: >>% mkdir test >>% ls -ld test >>drwxr-xr-x 2 sergio sergio 48 Апр 22 19:44 test/ >>% chmod +s test >>% ls -ld test >>drwsr-sr-x 2 sergio sergio 48 Апр 22 19:44 test/ >>% chmod 0755 test >>% ls -ld test >>drwsr-sr-x 2 sergio sergio 48 Апр 22 19:44 test/ >>% chmod -s test >>% ls -ld test >>drwxr-xr-x 2 sergio sergio 48 Апр 22 19:44 test/ > > Well, it's documented that way (man page says): > chmod preserves a directory’s set-user-ID and set-group-ID bits unless > you explicitly specify otherwise. You can set or clear the bits with > symbolic modes like u+s and g-s, and you can set (but not clear) the > bits with a numeric mode. > > This was a change in 6.0 (from NEWS): > chmod, install, and mkdir now preserve a directory's set-user-ID and > set-group-ID bits unless you explicitly request otherwise. E.g., > `chmod 755 DIR' and `chmod u=rwx,go=rx DIR' now preserve DIR's > set-user-ID and set-group-ID bits instead of clearing them, and > similarly for `mkdir -m 755 DIR' and `mkdir -m u=rwx,go=rx DIR'. To > clear the bits, mention them explicitly in a symbolic mode, e.g., > `mkdir -m u=rwx,go=rx,-s DIR'. To set them, mention them explicitly > in either a symbolic or a numeric mode, e.g., `mkdir -m 2755 DIR', > `mkdir -m u=rwx,go=rx,g+s' DIR. This change is for convenience on > systems where these bits inherit from parents. Unfortunately other > operating systems are not consistent here, and portable scripts > cannot assume the bits are set, cleared, or preserved, even when the > bits are explicitly mentioned. For example, OpenBSD 3.9 `mkdir -m > 777 D' preserves D's setgid bit but `chmod 777 D' clears it. > Conversely, Solaris 10 `mkdir -m 777 D', `mkdir -m g-s D', and > `chmod 0777 D' all preserve D's setgid bit, and you must use > something like `chmod g-s D' to clear it. > > I'm not sure how this isn't a POSIX violation, though: > For an octal integer mode operand, the file mode bits shall be set > absolutely. > > For each bit set in the octal number, the corresponding file permission bit
file permission bits does not include set-group-ID and set-user-ID bits. > shown in the following table shall be set; all other file permission bits > shall > be cleared. For regular files, for each bit set in the octal number > corresponding to the set-user-ID-on-execution or the > set-group-ID-on-execution, > bits shown in the following table shall be set; if these bits are not set in > the octal number, they are cleared. For other file types, it is > implementation-defined whether or not requests to set or clear the For non-regular files (directories in the examples above), chmod's behavior is implementation-defined. > set-user-ID-on-execution or set-group-ID-on-execution bits are honored.
