Use of uninitialized value for file name

[Win]

Monk TIME,


The following section of code is giving me grief:

opendir(DIR_A, "$version_location_programs") or die $!;

while(my $job =readdir(DIR_A)){
  print "I am here\n";
  print "$job";sleep 10;  
  if ($job =~ /20_October_2004.{3,}/) {
    push (@files_20_October_2004, "$directory_location"."$job");     
  }
}

It says Use of uninitialized value for $job.

[moklevat]

When readdir runs out of entries in the directory it returns an undefined value in scalar context.

Update:...but that won't explain why you get an initialization error.

For example

#!/usr/bin/perl

use warnings;
use strict;

opendir(DIR_A, './testdir') or die $!;

while (my $job = readdir(DIR_A)) {
 print "$job\n";
 if ($job =~ /something/) {
         print "Something was seen\n";
 }
}

prints

.
..

when testdir is empty, and prints

.
..
something.pl
Something was seen

when testdir contains the file something.pl.

[Win]

is

while(my $job =readdir(DIR_A)){
  print "I am here\n";
  print "$job";sleep 10;  
  if ($job =~ /20_October_2004.{3,}/) {
    push (@files_20_October_2004, $directory_location.$job);     
  }
}

the same as

while(<DIR_A>)){

  my $job = $_;
  print "I am here\n";
  print "$job";sleep 10;  
  if ($job =~ /20_October_2004.{3,}/) {
    push (@files_20_October_2004, $directory_location.$job);     
  }
}

?

[moklevat]

Have you tried this yourself?

#!/usr/bin/perl

use warnings;
use strict;

opendir(DIR_A, './testdir') or die $!;

while(<DIR_A>){
  my $job = $_;
  print "$job\n";
}

Gives this error:

readline() on unopened filehandle DIR_A at ./readdir.pl line 8.
        (Are you trying to call readline() on dirhandle DIR_A?)

[duff]

It says Use of uninitialized value for $job.

Are you sure? What is the exact error message? How do you know it's not complaining about $directory_location?

BTW, there's no need to quote your variables when concatenating them. A simple $directory_location.$job will suffice.

[Win]

Use of uninitialized value in string at C:/Perl_activate/Run_this.pl l
+ine 83

[duff]

And I'm guessing that line 83 is the one where you push onto the array? Check all of the variables on that line.

Or, if line 83 is one of the lines after the while loop, then what moklevat said comes into play.

[davidrw]

ok.. so what's on line 83? Is it maybe $directory_location that's undef instead? Add some debugging print/warn/Data::Dumper statements to see what's not what you expect.

[wfsp]

When I'm stumped I often try reducing the script to the bare bones to get something working and gradually add things back in.

Something like:

#!/usr/bin/perl

use warnings;
use strict;

my $dir = 'c:/Perl';

opendir DIR_A, $dir
  or die $!;
  
while(my $job = readdir(DIR_A)){
  print "$job\n";
}

__DATA__
---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" _new.pl
.
..
bin
Desktop.ini
eg
html
lib
myperl
site
Tidy

> Terminated with exit code 0.

When you come up against the error you'll have a better chance of narrowing down the source of your grief.

Hope that helps.

[Win]

Thanks, I followed your advice and then realised that I was doing multiple whiles and forgetting to close file handles. Basic error I'm afraid.

[blazar]

Had you been using lexical handles as it must have certainly been suggested to you (at least I *think* I did and I'm *confident* others did too), and properly scoped blocks, which should be natural in any case, then you wouldn't have needed explicit closes and you would have avoided this annoying error.