G'day scripter87,

You haven't really provided sufficient information. "it works" and "it dont" and spectacularly useless error reports. You haven't shown how you're testing this: i.e. what you're using for input. You haven't shown your data: there could be line ending and embedded whitespace issues. A better question gets better answers: take a look at the guidelines in "How do I post a question effectively?" to see how you can achieve this.

There's issues with the code as posted. It will print "not valid" for every record in names.txt until it either finds a match or reaches EOF. I see Eily pointed out an issue with $names: you said this was a typo; if you copy and paste your actual code, this won't happen. Do you really want to open/read/close the entire file for every "my $input = <STDIN>;"? Do you allow more than one attempt?

Here's a potentially better way to do what you want:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

my $name_file = 'names.txt';

open my $name_file_fh, '<', $name_file;
chomp(my @names = <$name_file_fh>);
close $name_file_fh;

print 'Enter login name: ';
chomp(my $input = <STDIN>);

print "Invalid!\n" unless grep { $_ eq $input } @names;
[download]

Note that you can wrap the 'Enter login name: ' part in a loop to allow multiple attempts without having to reread the file. Not shown in your posted code, so I haven't tried to make guesses here, but you'll need to code some sort of successful login actions.

Update: Prompted by Eily's mention of a hash and exists, which I saw after posting, this would be an improvement on what I originally provided:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

my $name_file = 'names.txt';

open my $name_file_fh, '<', $name_file;
my %name = map { chomp; $_ => 1 } <$name_file_fh>;
close $name_file_fh;

print 'Enter login name: ';
chomp(my $input = <STDIN>);

print "Invalid!\n" unless exists $name{$input};
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Unless the script is long running the hash solution is still sub optimal. Read the name, then look through the file, will on average read half the file for a valid name. The hash solution must always read the entire file. A better way to store the file could improve things even more, but perhaps we get silly...

Cheers,
R.

Pereant, qui ante nos nostra dixerunt!

I noted there was insufficient information. I asked whether multiple attempts were allowed. I presented a clearly stated potential solution.

Allowing multiple attempts is the norm. I raised the absence of code to achieve this (i.e. while loop) along with a lack of any handling of a successful login attempt.

Both the array and hash solutions read the entire file; obviously, this is not something specific to the hash solution. The point I made was that this was only done once regardless of the number of attempts.

-- Ken

While running under strict (use strict; on the first line): Global symbol "$names" requires explicit package name at - line 8.. The scalar you declared is $name, with no s at the end.

Just so you know, you can write the second loop as:

for my $el (@names)
{
    print "not valid" if $input ne $el;
}
[download]

sorry that was a typo. Can you see any particular reason that the file reads if there is only text on the first line of the file?

if input_name is in list:
  print "valid"
else:
  print "not valid"

This could be implemented with the following code:
if (grep(/^$input$/, @names) {
  print "Valid\n";
} else {
  print "Not valid\n";
}
[download]

thanks for the feedback. The basic thing I am trying to grasp is.. how to read files from a file for login purposes, so if I enter a name that is not in the file it obviously shouldnt work but as I said at the moment if I have just one line in the file it works ok but if more than one it doesnt.

Although there are several solutions for your task, consider the following:

use warnings;
use strict;

my $names = 'names.txt';
my ( $found, $name );

print 'Enter a name: ';
chomp( my $input = <STDIN> );

open my $fh, '<', $names or die "Cannot open $names: $!\n";

while ( $name = <$fh> ) {
    chomp $name;

    if ( $input eq $name ) {
        $found++;
        last;
    }
}

close $fh;

if ($found) {
    print qq{The name "$input" was found.\n};
}
else {
    print qq{The name "$input" was not found.\n};
}
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Note that:

• The name to search for is requested first.
• chomp is used to remove the trailing input record separator (usually \n), from both the entered name and the names from the file.
• The names' file is read once; no hash or array is necessary to 'hold' the names (Why process the list twice?). A flag's set and the while loop is immediately exited if the name is found.
• Appropriate responses are given depending upon the value of $found.

Hope this helps!

You should have tried the solution ramlight gave you, it does look like what you were looking for. Maybe grep { $_ eq $input } @names instead of grep(/^$input$/, @names) would avoid some trouble with the metacharacters in $input though. And if you don't understang what it does, try and read grep's documentation :).

Another way to do it would be using a hash, because you have exists to check if a name exists (obviously) in it.

my @nameList = qw/Anna Beatrix Claude Damian/;
my %names = map { $_ => 1 }, @nameList; # associate the value 1 to eac
+h name in @namelist. Actually the value could be anything in this cas
+e
print "Anna exists" if exists $names{"Anna"};
print "Paul doesn't exist" unless exists $names{"Paul"};
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And as taint already stated, chomp your strings :)

Thinking out loud;

chomp ...
foreach line as line ...

Well, something like that.

--Chris

#!/usr/bin/perl -Tw
use Perl::Always or die;
my $perl_version = (5.12.5);
print $perl_version;