Non-blocking write to file in Perl?

Question

Perl

There is perl code running on Windows that writes data to a file.

use warnings;
use feature 'say';

open(FH, '>', 'file.txt');
$i = 10;
while ($i > 0) {
  say FH $i;
  say $i;
  sleep 1;
  $i--;
}
close(FH)

While writing, another program tries to open the file for reading and fails with the error "IO error 32 - The process cannot access the file because it is being used by another process."
Replacing openwith sysopenwith adding an attribute O_NONBLOCKdoes not work.

use Fcntl qw(O_WRONLY O_CREAT O_APPEND O_NONBLOCK);

sysopen(FH, 'file.txt', O_WRONLY | O_CREAT | O_APPEND | O_NONBLOCK);

Mistake:

Your vendor has not defined Fcntl macro O_NONBLOCK

Using sysopenwithout O_NONBLOCKdoes nothing.
Windows 7, Strawberry Perl 5.16.3

Answer 1

Wrote a program that reads this file. She reads this file without problems.

use 5.12.0;use warnings;
use Fcntl qw(:flock);
open(FH, '<', 'file.txt') or die;
flock(FH, LOCK_EX|LOCK_NB) or die "Cannot lock - $! $^E\n";
while (<FH>) {
  print
}

In order for buffering to not work when writing, I added to your program
FH->autoflush(1);