belg4mit has asked for the wisdom of the Perl Monks concerning the following question:

Is there a nice (read terse and few/no blocks) means of retrieving the GIDs of all the groups a member is in?

(getpwuid($<))[3]

Only returns the first. Ideally it should be useable as:

$) = expression

Thanks!

Replies are listed 'Best First'.
Re: Fetching groups a user is in
by Kanji (Parson) on Oct 11, 2001 at 19:52 UTC
[reply]
      Seems like there ought to be something simpler though... 

      $) = &{sub{
    my(@F,@G);
    while( @F = getgrent() ){
    push(@G, $F[2]) if $F[3] =~ /\b$ENV{USER}\b/; }
    return join(' ', @G); } };

      [download]
[reply]
[d/l]
      Well yeah, but I was hoping I wouldn't have to muck with getgrent... but I suppose if I did an anonymous sub... 

      $) = sub {
  #iterate over getgrent, save gid of group that $) belongs to.

  return join(' ', @F);
}

      [download]

      Seems so unclean though

[reply]
[d/l]
        Nope wait, doesn't like <CODE>= sub { ..}</CODE, damn!
[reply]
Re: Fetching groups a user is in
by jlongino (Parson) on Oct 11, 2001 at 21:07 UTC
    The easiest thing to do is use the xnix (provided you are using an xnix box) command groups: 
    my @groups = `groups $username`;
print join "\n", @groups;

    [download]
    This normally doesn't require any special priviledges.

    Update: Then determine the GIDs of course.

    "Make everything as simple as possible, but not simpler." -- Albert Einstein

[reply]
[d/l]
Re: Fetching groups a user is in
by apotheon (Deacon) on Dec 21, 2006 at 22:05 UTC

    Obviously, I'm a little late to this party, but I stumbled across this while checking to see whether I'd have to (re)invent a wheel to answer a question on the Perl Beginners mailing list. This is the solution I ultimately came up with:

    #!/usr/local/bin/perl -l
use strict;
use warnings;

my $user = $ARGV[0];
my @gr_list;
my @pw_info;

while (@pw_info = getpwent) {
  if ($pw_info[0] eq $user) {
    my @gr_info;
    while (@gr_info = getgrent) {
      push(@gr_list, $gr_info[2]) if ($gr_info[3] =~ /\b$user\b/);
    }
    push(@gr_list, $pw_info[3]);
  }
}

print foreach @gr_list;

    [download]

    It's not stunningly terse or clean-looking, at least in my estimation, but it works and doesn't involve calling out to external system utilities.

    print substr("Just another Perl hacker", 0, -2);
    		 - apotheon
    CopyWrite Chad Perrin

[reply]
[d/l]
      I saved the code as gpu.pl and ran it for some users: 
      $ gpu.pl root
0
2
3
4
5
20
31
0

$ gpu.pl rvtol

$ id -Gn rvtol
user

      [download]
      With root, group 0 is reported twice. With rvtol, group user (30) isn't reported.

      -- 
      Regards, Ruud
[reply]
[d/l]

        Interesting. Any idea why?

        print substr("Just another Perl hacker", 0, -2);
        		 - apotheon
        CopyWrite Chad Perrin

[reply]

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