How does Perl read the last line of a large file in windows (Summary)

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

(1) read the file into the array and obtain 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 one row and output in the last row

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,$_);     shift@a; } close FILE; print @a;

(3) This has not been tried. If you are interested, try it.

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 less efficient. The following method is the most efficient, especially when the file is large:

Open the file, move the pointer to the end, and read one byte forward until \ N is read.

#!/usr/bin/perl -wuse strict;my $file = shift or die;my $content = "";open (F, $file) or die $!;seek (F, 0, 2);                                 # set handler at the end of $fileuntil ($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";}

Question http://bbs.chinaunix.net/thread-599099-1-1.html