Re: How does the while works in case of Filehandle when reading a gigantic file in Perl

I believe this to be a duplicated question on stackoverflow, in which case I believe this to be the code inside the {do something..} found on stackoverflow...Hopefully having the actual code within your loop posted here may help you get an answer to your problem, hope this helps...

$line=0;
%values;
open my $fh1, '<', "file.xml" or die $!;
while (<$fh1>)
{
$line++;
if ($_=~ s/foo//gi)
{
    chomp $_;
    $values{'id'} = $_;
}
elsif ($_=~ s/foo//gi)
{
    chomp $_;
    $values{'type'} = $_;
}
elsif ($_=~ s/foo//gi)
{
    chomp $_;
    $values{'pattern'} = $_;
}
if (keys(%values) == 3)
{
    open FILE, ">>temp.txt" or die $!;
    print FILE "$values{'id'}\t$values{'type'}\t$values{'pattern'}\n";
    close FILE;
    %values = ();
}
if($line == ($line1+1000000))
{
    $line1=$line;
    $read_time = time();
    $processing_time = $read_time - $start_time - $processing_time;
    print "xml file parsed till line $line, time taken $processing_tim
+e sec\n";
}
}
[download]

Comment on Re: How does the while works in case of Filehandle when reading a gigantic file in Perl Download Code

Replies are listed 'Best First'.
Re^2: How does the while works in case of Filehandle when reading a gigantic file in Perl by CountZero (Bishop) on Jan 30, 2015 at 19:56 UTC
You are opening and closing your output file for every line you read. Opening a file is timewise an "expensive" operation. As the file is opened for appending new lines to it, opening the file will take longer and longer, since the OS has to find the end of file to add the new line to it. Solution: open the output file in the beginning of your script and close it at the end. You should see an immediate speed improvement. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply]
Re^3: How does the while works in case of Filehandle when reading a gigantic file in Perl by raj4489 (Acolyte) on Feb 06, 2015 at 12:36 UTC
I have checked the timings for all the steps individually, and no step in the while loop takes anymore time (it remains constant). But only when getting in the while, the time keeps on increasing for every new line.	[reply]
Re^4: How does the while works in case of Filehandle when reading a gigantic file in Perl by CountZero (Bishop) on Feb 06, 2015 at 19:45 UTC
Did you try the solution I suggested? CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply]
Re^2: How does the while works in case of Filehandle when reading a gigantic file in Perl by AnomalousMonk (Archbishop) on Jan 30, 2015 at 16:03 UTC
perloHolic(): Can you post a link to the SO question so we can follow along? (This is really the responsibility of raj4489, but he or she is new to this site and may be unfamiliar with the ins-and-outs of PM and/or SO.) Give a man a fish: `<%-(-(-(-<`	[reply] [d/l]
Re^3: How does the while works in case of Filehandle when reading a gigantic file in Perl by perloHolic() (Beadle) on Jan 30, 2015 at 16:32 UTC
Sure, no problem. http://stackoverflow.com/questions/28234374/how-does-the-while-works-in-case-of-filehandle-when-reading-a-gigantic-file-in-p my apologies if there is a proper way to format this link, i'm not exactly an expert at this posting practice yet either	[reply]
Re^4: How does the while works in case of Filehandle when reading a gigantic file in Perl by AnomalousMonk (Archbishop) on Jan 30, 2015 at 17:27 UTC
... posting practice ... See What shortcuts can I use for linking to other information?, `[http://...]` and `[href://...]`, I think, in particular. Give a man a fish: `<%-(-(-(-<`	[reply] [d/l] [select]
Re^2: How does the while works in case of Filehandle when reading a gigantic file in Perl by raj4489 (Acolyte) on Feb 06, 2015 at 12:34 UTC
Thanks for posting my code	[reply]


Do you know where your variables are?
	PerlMonks