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how match/expose the value in an empty variable having length of 1
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Jack
*nix forums Guru Wannabe


Joined: 27 Feb 2005
Posts: 161

PostPosted: Sat Jul 15, 2006 6:49 am    Post subject: how match/expose the value in an empty variable having length of 1 Reply with quote
Hi folks,

Ok I am stumped... I am reading a fileline in as follows:

12535957@140@2006-07-08 09:34:45.000@@@2005-11-24@

and splitting on the "@"...
open(SOURCE1,$filename1)
@columnarray = split(/\@/, $_);

Whats really wierd is $columnarray[4] has a length of 1, when clearly
above its NULL !!
I want to be able to recognize this as null, but you cant even match
regex it... I tried

if ($columnarray[4] =~ m/.*?[[:print:]]/) { print " NON PRINTABLE
"."\n"; }
$columnarray[4] =~ s/^\s+//;
$columnarray[4] =~ s/\s+$//;
$length = length @columnarray[4]."\n";
and a number of other things that dont work.. how do I identify "WHAT"
is making up the length =1 ?

Also, what is the detection match test for NULL ?

Thank you all much,
Jack
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Jack
*nix forums Guru Wannabe


Joined: 27 Feb 2005
Posts: 161

PostPosted: Sat Jul 15, 2006 7:43 am    Post subject: Re: how match/expose the value in an empty variable having length of 1 Reply with quote
Jack wrote:
Quote:
Hi folks,

Ok I am stumped... I am reading a fileline in as follows:

12535957@140@2006-07-08 09:34:45.000@@@2005-11-24@

and splitting on the "@"...
open(SOURCE1,$filename1)
@columnarray = split(/\@/, $_);

Whats really wierd is $columnarray[4] has a length of 1, when clearly
above its NULL !!
I want to be able to recognize this as null, but you cant even match
regex it... I tried

if ($columnarray[4] =~ m/.*?[[:print:]]/) { print " NON PRINTABLE
"."\n"; }
$columnarray[4] =~ s/^\s+//;
$columnarray[4] =~ s/\s+$//;
$length = length @columnarray[4]."\n";
and a number of other things that dont work.. how do I identify "WHAT"
is making up the length =1 ?

Also, what is the detection match test for NULL ?

Thank you all much,
Jack

NEVERMIND.. sorry.. I figured it out.. no need to post.
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Tad McClellan
*nix forums Guru


Joined: 09 Mar 2005
Posts: 1647

PostPosted: Sat Jul 15, 2006 12:44 pm    Post subject: Re: how match/expose the value in an empty variable having length of 1 Reply with quote
Jack <jack_posemsky@yahoo.com> wrote:

Quote:
$length = length @columnarray[4]."\n";
^^

^^ this is one character long

And you should always enable warnings when developing Perl code.


Quote:
how do I identify "WHAT"
is making up the length =1 ?


By looking closely at the string above that is the argument for length().


Quote:
Also, what is the detection match test for NULL ?


Perl does not have anything known as NULL. I expect you mean
an "empty string".

print "empty string\n" unless length $columnarray[4];

or

print "empty string\n" if $columnarray[4] =~ /^\z/;


--
Tad McClellan SGML consulting
tadmc@augustmail.com Perl programming
Fort Worth, Texas
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J. Gleixner
*nix forums Guru Wannabe


Joined: 10 Mar 2005
Posts: 195

PostPosted: Mon Jul 17, 2006 10:21 pm    Post subject: Re: how match/expose the value in an empty variable having length of 1 Reply with quote
Jack wrote:
Quote:
Hi folks,

Ok I am stumped... I am reading a fileline in as follows:

12535957@140@2006-07-08 09:34:45.000@@@2005-11-24@

and splitting on the "@"...
open(SOURCE1,$filename1)
@columnarray = split(/\@/, $_);

Post real code as an example. If your code is actually the above, then
it has a lot of problems.

Quote:

Whats really wierd is $columnarray[4] has a length of 1, when clearly
above its NULL !!

How do you know its length is 1?

Quote:
I want to be able to recognize this as null, but you cant even match
regex it... I tried

if ($columnarray[4] =~ m/.*?[[:print:]]/) { print " NON PRINTABLE
"."\n"; }
$columnarray[4] =~ s/^\s+//;
$columnarray[4] =~ s/\s+$//;
$length = length @columnarray[4]."\n";

Adding these to your code would have caught the error..

use strict;
use warnings;

my $length = length $columnarray[4]

Quote:
and a number of other things that dont work.. how do I identify "WHAT"
is making up the length =1 ?

Also, what is the detection match test for NULL ?

Maybe this will help you:

perldoc -f defined

A short script as an example:

#!/usr/bin/perl
use strict;
use warnings;
my $str='12535957@140@2006-07-08 09:34:45.000@@@2005-11-24@';
my @columnarray = split(/\@/, $str);
print "length=", length( $columnarray[4] ), "\n";
print "columnarray[4] is an undefined value" unless defined $columnarray[4];
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Google
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