A.15 Chapter 16, System Database Access

1. Here's one way to do that:

   $: = " "; while (@pw = 
   
   getpwent) {     ($user, $gid, $gcos) = 
   
   @pw[0,3,6];     ($real) = split /,/, $gcos;     $real{$user} = $real;     $members{$gid} .= " $user";     ($last) = (split /\s+/, $real)[-1];     $last{$user} = "\L$last"; }  while (@gr = getgrent) {     ($gname,$gid,$members) = @gr[0,2,3];     $members{$gid} .= " $members";     $gname{$gid} = $gname; }  for $gid (
   
   sort by_gname keys %gname) {     %all = ();     for (split(/\s+/, $members{$gid})) {         $all{$_}++ if 
   
   length $_;     }     @members = ();     
   
   foreach (sort by_last keys %all) {         
   
   push(@members, "$real{$_} ($_)");     }     $memberlist = 
   
   join(", ", @members);     
   
   write; }  sub by_gname { $gname{$a} 
   
   cmp $gname{$b}; } sub by_last { ($last{$a} cmp $last{$b}) 
   
   || ($a cmp $b); }  format STDOUT = @<<<<<<<< @<<<<<<<< ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< $gname{$gid}, "($gid)", $memberlist ~~                  ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< $memberlist .

   Yes, this one needs some explaining.