Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi, this script does exactly what i want it to which is select the 14th and 15th column from a table and print it. but when it runs the horrible error message is " error! use of uninitialised value in concatenation (.) or string near FILEHANDLE>. i can't spot the error, but i think it might be around the print statements! can anyone help?? heres the code. 

#! /usr/local/bin/perl -w

use strict;

open (FILEHANDLE, $ARGV[0]) or die "unable to open file";
open (OUTFILE, ">$$.output");

my $line;
my @array;

while (<FILEHANDLE>)
{
$line = $_;
chomp ($line);

@array = ();
@array = split (/\s+/, $line);

print STDOUT "$array[13]\t$array[14]\n";
print OUTFILE "$array[13]\t$array[14]\n";
}

close FILEHANDLE;
close OUTFILE;

exit;

[download]
thanks :-)

Edit kudra, 2002-05-07 Changed title

  • Comment on Getting rid of uninitialized value warning (was: can't spot the error)
  • Download Code

Replies are listed 'Best First'.
Re: can't spot the error
by demerphq (Chancellor) on May 07, 2002 at 16:05 UTC
    Well its almost certainly that there is an undef in one of the values you are printing. Adding 
    $array[13]="" unless defined $array[13];
$array[14]="" unless defined $array[14];

    [download]
    Should sort you out.

    BTW, a more idomatic way to write your loop would be 

    while (<FILEHANDLE>) {
  chomp;
  my @array=split/\s+/;
  $array[13]="" unless defined $array[13];
  $array[14]="" unless defined $array[14];
  print "$array[13]\t$array[14]\n";
  print OUTFILE "$array[13]\t$array[14]\n";
}

    [download]

    Yves / DeMerphq
    ---
    Writing a good benchmark isnt as easy as it might look.

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      An even more idiomatic way might be: 
      while (<FILEHANDLE>) {
  chomp;
  my @array = split;
  next unless @array >= 15;
  ...
}

      [download]

      conv

[reply]
[d/l]
        While I agree that your snippet is more idiomatic, it isnt the same thing as what the OP provided. 
        $_=" a b c d e    f g h";
@list=split/\s+/;
print "split /\\s+/ : ";
foreach my $i (0..$#list) {
    printf "%2d '%s', ",$i,$list[$i];
}
print "\n";
@list=split;
print "split       : ";

foreach my $i (0..$#list) {
    printf "%2d '%s', ",$i,$list[$i];
}
print "\n";
__END__
split /\s+/ :  0 '',  1 'a',  2 'b',  3 'c',  4 'd',  5 'e',  6 'f',  
+7 'g',  8 'h', 
split       :  0 'a',  1 'b',  2 'c',  3 'd',  4 'e',  5 'f',  6 'g', 
+ 7 'h',

        [download]
        And while I'm being pedantic :-) why do @array >= 15 when @array>14 does the same thing?

        *grin*

        Yves / DeMerphq
        ---
        Writing a good benchmark isnt as easy as it might look.

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Re: can't spot the error
by hotshot (Prior) on May 07, 2002 at 16:04 UTC
    I think you shoud check your array before printing entries 13 and 14, I suspect they're indeed un initialized.
    Try doing:
    
#! /usr/local/bin/perl -w

use strict;

open (FILEHANDLE, $ARGV[0]) or die "unable to open file";
open (OUTFILE, ">$$.output");

my @array;

while (<FILEHANDLE>)
{
chomp;

@array = ();
@array = split(/\s+/);

if (defined($array[13]) && defined($array[14])) {
  print STDOUT "$array[13]\t$array[14]\n";
  print OUTFILE "$array[13]\t$array[14]\n";
}

    [download]


    Thanks.

    Hotshot
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Re: can't spot the error
by erikharrison (Deacon) on May 07, 2002 at 16:12 UTC

    Apparantly at some point $array[14] or $array[15] is empty. You get a slew of errors as this is repeated through the loop. Initialize each member of the array instead of setting it to empty - this will hitperformance but should clear your problem.

    On another note, please indent your code within the while block. :-)

    Cheers,
    Erik
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