Getting groups you belong to in perl

Corinna Vinschen corinna-cygwin@cygwin.com
Fri Mar 14 16:50:00 GMT 2014


On Mar 14 17:04, Andrey Repin wrote:
> Greetings, PANEL Vincent (CIS/SIN)!
> 
> >>> Don't know if this list is more appropriate than the Perl one but my
> >>> question is actually about porting a Perl script to Cygwin. I need to
> >>> check if the current user running the script belongs to a pre-defined group.
> 
> >>> Under *nix, I get the list of users belonging to the group and see if
> >>> the current user is in this list.
> 
> >>How exactly you are doing this? (I hope you're not reading it from
> >>/etc/group, because that file may not exist at all, or contain exactly
> >>zero relevant
> >>information.)
> 
> > I'm using standard perl commands (getgrnam, getlogin, etc... :
> > http://perldoc.perl.org/5.14.2/functions/getgrnam.html) which are probably
> > using standard C libraries in the background (I hope). The doc explicitly
> > says "The $members value returned by getgr*() is a space-separated list of
> > the login names of the members of the group" but it's always empty under
> > Cygwin. 
> 
> The functionality you're looking for may(or may not) be available soon(tm).
> Corinna doing some rework of the core user/group handling as we speak.

No, sorry.  You don't know it yet, but you really don't want that.  The
cost to generate full gr_mem info from the Windows user DBs in terms of
performance is prohibitive.  And it's really not required information
because there are other ways to fetch this info only if it's really
required:

- For the current user, use getgroups(2):

    http://linux.die.net/man/2/getgroups

- For another account use getgrouplist(3):

    http://linux.die.net/man/3/getgrouplist

> Check the "Testers needed: New passwd/group handling in Cygwin" thread(s).
> Do note that in the light of upcoming 1.29 release, snapshots do not contain
> the code in question. You'd need to rebuild DLL from CVS to get them.

Or just use the older 2014-03-05 snapshot for the time being.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat
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