How to read the last line of a large file in Perl under Windows (Summary)

There are many ways to read the last line of a file in Perl, such as

(1) Read the file into the array and take the last element

open (FILE, "file.txt") or die "$!";
my @ arr = <FILE> ;;
close FILE;
my $ last = $ arr [$ # arr];

# $ last is the content of the last line.
(2) Read in line by line, output when the last line

open (FILE, "file.txt") or die "$!";
while (<FILE>;)
{
    open (TMP, "> tmp.txt") or die "$!";
    print TMP $ _;
    close TMP;
}
close FILE;
or

open (FILE, "file.txt");
$ a = <FILE> ;; push (@ a, $ a);
while (<FILE>)
{
     push (@a, $ _);
    [email protected];
}
close FILE;
print @a;
(3) This has not been tried, you can try if you are interested

http://search.cpan.org/~mjd/Tie-File-0.96/lib/Tie/File.pm
DESCRIPTION ^

Tie :: File represents a regular text file as a Perl array. Each element in the array corresponds to a record in the file. The first line of the file is element 0 of the array; the second line is element 1, and so on .

The file is not loaded into memory, so this will work even for gigantic files.

Changes to the array are reflected in the file immediately.

Lazy people and beginners may now stop reading the manual.

(4) The above methods all need to traverse the entire file, which is inefficient. The following method is the most efficient, especially when the file is large, the method is:

Open the file, move the pointer to the end, read one byte at a time until it reaches \ N

#! / usr / bin / perl -w

use strict;

my $ file = shift or die;
my $ content = "";

open (F, $ file) or die $ !;
seek (F, 0, 2); # set handler at the end of $ file
until ($ content = ~ m / \ n (. *) \ n? $ /)
{
        my $ string;
        if (seek (F, -1024, 1)) # backward 1024 bytes
        {
                my $ n = read (F, $ string, 1024) or die $ !;
                $ content = $ string. $ content;
                last if ($ n <1024);
                seek (F, -1024, 1);
        }
        else {
                my $ len = tell F;
                seek (F, 0, 0) || die "see error at $ file";
                read (F, $ string, $ len) or die $ !;
                $ content = $ string. $ content;
                last;
        }
}
close (F);

if ($ content = ~ m / \ n \ n $ /)
{
        print "\ n";
} elsif ($ content = ~ m / \ n? (. *) \ n? $ /) {
        print "$ 1 \ n";
} else {
        print $ content, "\ n";
}
The content in the article comes from: Question http://bbs.chinaunix.net/thread-599099-1-1.html