Perl: Get key value - perl

Question

I'm trying to get key values from hash inside my module:
Module.pm
...
my $logins_dump = "tmp/logins-output.txt";
system("cat /var/log/secure | grep -n -e 'Accepted password for' > $logins_dump");
open (my $fh, "<", $logins_dump) or die "Could not open file '$logins_dump': $!";
sub UserLogins {
my %user_logins;
while (my $array = <$fh>) {
if ($array =~ /Accepted\s+password\s+for\s+(\S+)/) {
$user_logins{$1}++;
}
}
return \%user_logins;
}
sub CheckUserLogins {
my $LoginCounter;
my $UsersToCheck = shift #_;
if (exists %{UserLogins()}{$UsersToCheck}){
$LoginCounter = %{UserLogins{$UsersToCheck}}; #How many logins?
}
else {
$LoginCounter = "0";
}
return \$LoginCounter;
}
Script.pl
$UserLoginCounter = Module::CheckUserLogins($UsersToPass);
I pass usernames to script and check if username is in hash, if it is, I need to return number of logins, which I'm trying to do with $LoginCounter. For some reason scripts returns only 0 or undef.

Answer 1

Well, for starters - you've got CheckUserLogins not CheckLoginAttempts.
Assuming that's just a typo - UserLogins returns a hash reference - a single scalar value. You're getting 0 if the exists check fails presumably.
If it does exist though, you're doing this:
$LoginCounter = %{UserLogins{$UsersToCheck}};
Which isn't valid. Do you have strict and warnings turned on? Because you're trying to assign a hash to a scalar, which isn't going to do what you want.
You probably mean:
$LoginCounter = ${UserLogins()} -> {$UsersToCheck};
Which dereferences the reference from UserLogins and then looks up a key.
I might however, approach your problem a little differently - it'll only work once when you do what you're doing, because each time you call UserLogins it creates a new hash, but you don't rewind $fh.
So I'd suggest:
use strict;
use warnings;
{
my %userlogins;
sub inituserlogins {
open( my $fh, "<", '/var/log/secure' )
or die "Could not open file: $!";
while ( my $array = <$fh> ) {
if ( $array =~ /Accepted\s+password\s+for\s+(\S+)/ ) {
$userlogins{$1}++;
}
}
close($fh);
}
sub CheckUserLogins {
my ($UsersToCheck) = #_;
inituserlogins() unless %userlogins;
return $userlogins{$UsersToCheck} ? $userlogins{$UsersToCheck} : 0;
}
}

Answer 2

You mustn't use capital letters in lexical identifiers as Perl reserves them for global identifiers like package names
One of the main problems is that you're using
exists %{UserLogins()}{$UsersToCheck}
which should be
exists UserLogins()->{$UsersToCheck}
or
exists ${UserLogins()}{$UsersToCheck}
Do you have use strict and use warnings in place as you should have?
Another problem is that you will read all the way through the file every time you call UserLogins. That means the second and later calls to CheckUserLogins (which calls UserLogins) will find nothing, as the end of the file has been reached
You should call your suibroutine user_logins and call it just once, storing the result as a scalar variable. This program shows how
use strict;
use warnings;
use v5.14; # For state variables
sub user_logins {
open my $fh, '<', '/var/log/secure' or die $!;
my %user_logins;
while ( <$fh> ) {
if ( /Accepted\s+password\s+for\s+(\S+)/ ) {
++$user_logins{$1};
}
}
\%user_logins;
}
sub check_user_logins {
my ($users_to_check) = #_;
state $user_logins = user_logins();
$user_logins->{$users_to_check} // 0;
}