What is written in one file write to another

Question

I have one file, and I need everything that is written in some time frame to that file to be written to a second file.

What is the best way to do so? Open some thread that will read the file and do so ?

Any ideas ?

Answer 1

Sounds like a job for File::Copy

Answer 2

Sounds like a job for tail -f or the poor man's tail -f emulation.

Answer 3

The tee utility might be what you're looking for:

#! /usr/bin/perl

use warnings;
use strict;

my @files = qw/ file1 file2 /;

open my $fh, "| tee @files >/dev/null"
  or die "$0: start tee failed: $!";

print $fh "$_\n" for map int rand 10, 1 .. 5;

close $fh or warn "$0: close tee: $!";

Sample run:

$ ./write-both

$ cat file1
0
7
5
8
2

$ cat file2
0
7
5
8
2