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From: Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: standards and 'setgid' function
Date: 4 Jan 2002 12:47:53 GMT
Organization: Aachen University of Technology (RWTH)
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HARY <Hary AT address DOT is DOT invalid> wrote:
> Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de> wrote:
>> They're both right.  setgid is specified by POSIX, but Linux only
>> follows the exact details of that specification if you explicitly ask
>> for that (see the text of their man page).

> "setgid is implemented like the POSIX version with the _POSIX_SAVED_IDS
> feature." 

> I just don't know what _POSIX_SAVED_IDS means. Could you explain it?

Only by looking it up myself... The "feature" is actually a macro: if
it's #define'd, the feature is active.  On Linux, it's activated
automatically, because <unistd.h>, the central POSIX include file, has
an #include <bits/posix_opt.h> in it, and that file in turn has:

#define _POSIX_SAVED_IDS        1

AFAICS, this whole mechanism is needed only because the libc used on
Linux systems, glibc, is also used on other platforms.  But the
documentation is common to all of them, so it doesn't know the
behaviour details of the platform you're running it on.
-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.