There are alot of ways to do this. Here is one way. This example just grabs a chunk off of the end.(truncating is left to you). 
#!/usr/bin/perl -w
# linux only,  
# usage tailz  filename   
use strict;

my $filename = shift or die "Usage: $0 file \n";
my $byte;

# Open the file in read mode 
open FILE, "<$filename" or die "Couldn't open $filename: $!";

# Rewind from the end of the file until count eol's 
seek FILE,0, 2;  #go to EOF 
seek FILE,-2048,2; #get last 2k bytes 

$/=undef;
my $tail = <FILE>;
print "$tail\n";
exit;

[download]
or here is a variation for lines 
#!/usr/bin/perl -w
# example for files with max line lengths < 400, but it's adjustable 
# usage tailz  filename  numberoflines 
use strict;

die "Usage: $0 file numlines\n" unless @ARGV == 2;
my ($filename, $numlines) = @ARGV;

my $chunk = 400 * $numlines; #assume a <= 400 char line(generous) 

# Open the file in read mode 
open FILE, "<$filename" or die "Couldn't open $filename: $!";
my $filesize = -s FILE;
if($chunk >= $filesize){$chunk = $filesize}
seek FILE,-$chunk,2; #get last chunk of bytes 

my @tail = <FILE>;
if($numlines >= $#tail +1){$numlines = $#tail +1}
splice @tail, 0, @tail - $numlines;

print "@tail\n";
exit;

[download]
I'm not really a human, but I play one on earth. flash japh

In reply to Re: truncate a file from top by zentara
in thread truncate a file from top by SiLiK

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