reading files in a directory with range operator.

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

Hi all,

I wrote this code in which I want to read some files in a folder. (Files are named in format YYYY_MM_DD,eg. 2010_01_24,). There are around "30 files" with naming from 2009_01_25.dat to 2010_01_24.dat. Now I wish to apply a filter on the date and read only those files which matches the range of dates. The code is given below.

use strict;
use warnings;

my $csvprint;
my $csv;
opendir DIR, "./dates/";

my @inputfiles = grep { $_ ne '.' && $_ ne '..' } readdir (DIR);

my @sorting = sort {$a cmp $b} @inputfiles;
#print @sorting,"\n\n\n";
foreach(@sorting)
{
    my $start = "2009_12_30";
    my $end = "2010_01_05";
    
    if ($_=~ /^$start/../^$end/)
    {
        open FILE, "< ./dates/$_";
        while (<FILE>)
        {
            chomp;
            
            my @content = split (/\,/,$_);
            my @datesplit = split(/\_/,$content[0]);
            $csvprint = "$datesplit[0],$datesplit[1],$content[1]\n";
            if ($csvprint ne 0)
            {
                $csv .= $csvprint;
            }
            else
            {
                
                print "blank\n";
            }
        }
    }
    else
    {
        print "nothing printed. \n";
        #print $_,"\n";
    }
    
    #print $csvprint,"\n\n";
}
#print $csv;
open CSV,"> 1.csv";
print CSV $csvprint;
[download]

My input files are of the format

File Name : 2009_12_24.dat

Content:
2009-12-24_Image,807
2009-12-24_image,119895419
2009-12-24_x-epoc,1138251
2009-12-24_multipart,185849
2009-12-24_application,45164332
2009-12-24_,5587
2009-12-24_audio,11638246
2009-12-24_video,97898353
2009-12-24_text,65788112

Now when I run this script I am getting this warning everytime.

Use of uninitialized value in concatenation (.) or string at files.pl 
+line 26, <
FILE> line 6.
Use of uninitialized value in concatenation (.) or string at files.pl 
+line 26, <
FILE> line 15.
Use of uninitialized value in concatenation (.) or string at files.pl 
+line 26, <
FILE> line 24.
Use of uninitialized value in concatenation (.) or string at files.pl 
+line 26, <
FILE> line 33.
Use of uninitialized value in concatenation (.) or string at files.pl 
+line 26, <
FILE> line 42.
Use of uninitialized value in concatenation (.) or string at files.pl 
+line 26, <
FILE> line 51.
Use of uninitialized value in concatenation (.) or string at files.pl 
+line 26, <
FILE> line 60.
[download]

and also I am able to get the results. I am not able to understand why this warning is being generated. Please help.

Comment on reading files in a directory with range operator. Select or Download Code

Replies are listed 'Best First'.
Re: reading files in a directory with range operator. by toolic (Bishop) on Jan 24, 2010 at 18:39 UTC
This is your line 6: `2009-12-24_,5587` [download] After your 1st split, `$content[0]` contains the string `2009-12-24_`, as desired. Then you split that string on the underscore character. The resulting array, `@datesplit`, now has only one element. The problem arises because you expected that array to contain (at least) two elements in your next line: `$csvprint = "$datesplit[0],$datesplit[1],$content[1]\n";` [download] If this line represents valid input data, then you must check how many elements are in your `@datesplit` array if you want to avoid this warning. Perhaps you want to do something like this: `if (@datesplit > 1) { $csvprint = "$datesplit[0],$datesplit[1],$content[1]\n"; } else { $csvprint = "$datesplit[0],$content[1]\n"; }` [download]	[reply] [d/l] [select]
Re: reading files in a directory with range operator. by Anonymous Monk on Jan 24, 2010 at 14:13 UTC
Simple, line 26 in your program `my @content = split (/\,/,$_); my @datesplit = split(/\_/,$content[0]); $csvprint = "$datesplit[0],$datesplit[1],$content[1]\n";` [download] fails for line 6 of FILE, which is `2009-12-24_,5587` [download]	[reply] [d/l] [select]