CODEWITHSUNDEEP
perlactiveperl
Arav
Arav

Reputation: 5247

Regarding perl tie::File Module

I have two queries about the tie::file module

  1. I have used the tie::file module to do a search on a 55 MB file and set an memory of 20 MB in tie::file. When i tried to grep on the tied array for a search string it's taking a lot of time. Is there any work around for it?

  2. Can tie::file used for reading a binary file. The tied array is delimited by "\n". How do i use a tie::file to read an binary file? Could you pls paste me some sample code.

/home/a814899> perl -e 'print "x\n"x27 for 1..1024*1024;' >a

/home/a814899> echo "hello world" >> a

Using Unix grep

/home/a814899> time grep "hello " a
hello world

real    0m8.280s
user    0m8.129s
sys     0m0.139s

Using the regex

/home/a814899> (time perl -e 'while (<>) { if (/hello/) { print "hello world"} }' a)
hello world
real    0m51.316s
user    0m51.087s
sys     0m0.189s


Using Perl Grep

#!/usr/bin/perl
print "executing\n";
my $outputFileDir="/home/a814899";
my $sFileName="a";
open my $fh, "<", $outputFileDir . "/" . $sFileName or do {
       print "Could not open the file";
    };
print "success  in open" . "\n";
my @out=grep {/hello world/} <$fh> ;
print "@out" ;
close($fh)

Upvotes: 0

Views: 403

Answers (1)

ikegami
ikegami

Reputation: 386311

  1. Yes.

    This is how you probably did it using Tie::File:

    $ (
    time perl -MTie::File -e'
       tie @a, "Tie::File", $ARGV[0];
       for (@a) { if (/y/) { } }
    ' a
) 2>&1 | grep real
real    2m44.333s

    This is the "workaround":

    $ (
    time perl -e'
        while (<>) { if (/y/) { } }
    ' a
) 2>&1 | grep real
real    0m0.644s

    The data file was created using

    $ perl -E'say "x"x54 for 1..1024*1024;' >a

  2. Tie::File doesn't read files; Tie::File provides a means of mapping lines of a file to array elements. Since "binary" files have no lines, accessing one using Tie::File wouldn't make any sense.

Upvotes: 2

Related Questions