What is a good way to wait until a file updated and then read from it in Perl?

Question

I was wondering if there's a way to wait for a file to be updated, and then read from it once it's updated. So if I have file.txt, I want to wait until something new is written to it, and then read it/process it/etc. Currently I am polling using Time::HiRes::sleep(.01), but I'm wondering if there's a better way. Thanks.

Answer 1

File::Tail will poll the file, but has a few advantages over your approach:

• The poll time is recomputed dynamically based on the number of lines written since the last poll
• If the file remains unchanged, polling will slow to avoid using up CPU
• File::Tail will detect if the file has been truncated, moved and/or recreated, and silently re-open the file for you
• It can tie a regular file handle which you can use like normal without any special API or syntax.

Example from the perldoc:

use File::Tail;
my $ref=tie *FH,"File::Tail",(name=>$name);
while (<FH>) {
    print "$_";
}