Shell Programming and Scripting

#!/usr/bin/env perl

use warnings;
use strict;

use constant PASSWD => 'htpasswd';
use constant GROUPS => 'htgroups';
use constant NEW    => '.new';

sub usage {
    die "Usage: $0 EXPDATE, where EXPDATE is in YYYY-MM-DD format"
}

usage if @ARGV != 1 or $ARGV[0] !~ /\d{4}-\d{2}-\d{2}/;

my $expdate = shift;
my %users;

# don't output expired users from PASSWD to PASSWD.NEW
# and remember them in %users

open my $fpasswd, '<', PASSWD or die $!;
open my $fpasswd_new, '>', PASSWD . NEW or die $!;

while (<$fpasswd>) {
    if (/^(\w+):.*\[exp:([\d-]+)\]/) {
        if ($2 lt $expdate) {
            $users{$1}++;
        } else {
            print $fpasswd_new $_;
        }
    } else {
        print $fpasswd_new $_;
    }
}

close $fpasswd;
close $fpasswd_new;

# remove users from %users from records of GROUPS file
# and don't output the records to GROUPS.NEW where no more users

# records in GROUPS should be separated by blank lines

open my $fgroups, '<', GROUPS or die $!;
open my $fgroups_new, '>', GROUPS . NEW or die $!;

local $/;
$/="";

# not very robust but this may be enough
while (<$fgroups>) {
    for my $user (keys %users) {
        s/$user//;
    }
    s/ +/ /g;   # here may appear extra spaces so squash them
    s/ +$//gm;

    print $fgroups_new $_ if !/^[^#]\w+:\s*$/m;
}

close $fgroups;
close $fgroups_new;