windows下Perl如何讀取大檔案的最後一行(總結)

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Perl中讀取檔案最後一行的方法很多，比如

（1）將檔案讀入數組，取最後一個元素

open (FILE,"file.txt") or die "$!";my @arr=<FILE>;;close FILE;my $last=$arr[$#arr];#$last裡就是最後一行的內容了。

（2）一行一行讀入，到最後一行時輸出

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

或者

open (FILE,"file.txt") ; $a=<FILE>;;push(@a,$a); while (<FILE> ){     push(@a,$_);     [email protected]; } close FILE; print @a;

（3）這個並未嘗試過，有興趣可以試試

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）以上的方法都需要遍曆整個檔案，效率較低。下面這個方法是最高效的，特別是檔案很大時，方法是：　　

　　開啟檔案,把指標移動到最後面,一個一個位元組往前讀,直到讀到\N為止

#!/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";}

文中內容來自：提問http://bbs.chinaunix.net/thread-599099-1-1.html