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

I want to get the secondary groups of a user name $name for linux. I try that :

  while (1) {
    last unless (($gname,$gpasswd,$gid,$members)=getgrent ());
    @list_members=split (/\s+/,$members);
    @list=grep (/$name/,@list_members);
    if ($list[0] eq $name) {
      push (@sec_gp,"$gname");
    }

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But I've got 2 problems :
- the groups are pushed twice in @sec_gp,
- I 'm not sure it's the better way to do it.
Thanks.

Replies are listed 'Best First'.
Re: To get the secondary groups for linux
by jlongino (Parson) on Jan 05, 2002 at 05:18 UTC
    This version eliminates the unless statement, but is basically the same as your example (you should use strict). I'm running this on a Solaris 8.0 system but I don't get any duplicates. 
    use strict;

my @sec_gp;
my $name = "xxxxx";
while (my ($gname,$gpasswd,$gid,$members)=getgrent) {
   my @list_members=split (/\s+/,$members);
   my @list=grep (/$name/,@list_members);
   if ($list[0] eq $name) {
      push (@sec_gp,"$gname");
   }
}
print "\@sec_gp: ";
print "$_\n" foreach @sec_gp;

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    Output: 
    @sec_gp: acad libsoftwrite helpdesk codes

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    --Jim Update: The above was hastily done. Better is the following (still room for improvement I'm sure): 

       push(@sec_gp, "$gname") if $list[0] eq $name;

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    for the original if statement.
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      I have understand why I have duplicatas : a NIS server is running. So, now I know that the function getgrent looks both /etc/passwd and the NIS database. It doesn't appear in the french man page of getgrent (Mandrake). PS : I've got to learn english before learning Perl !
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Re: To get the secondary groups for linux
by kschwab (Vicar) on Jan 05, 2002 at 08:37 UTC
    On the off chance that you are more interested in the current group membership of the current running process, there's POSIX::getgroups. 
    use POSIX qw(getgroups);
# get list of the current groups for this process
my @gidlist=getgroups();
# you'd  have to translate numeric gid's to 
# the names here

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    Update:

    Here's another shot at getting secondary groups, this one from the id command in the Perl Power Tools project: 

    while ( my($name,$pw,$gid,$members) = getgrent ) {
  push(@rgids,$gid) if ( grep($_ eq $user,split(/\s+/,$members)) );
}

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Re: To get the secondary groups for linux
by belg4mit (Prior) on Jan 05, 2002 at 13:28 UTC
    Yeah, I did this in a cron; in perl. My solution was (roughly, this is cut & paste with edit on the fly): 
    while( my @F = getgrent() ){ push @groups, [@F] }; endgrent();
@sec_gp = map($_->[2], grep($_->[3] =~ /\b$name\b/,@groups) ) );

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    --
    perl -pe "s/\b;([st])/'\1/mg"

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