Perlで「確実に閉じる」コード | Codetter（こーどったー）

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#!/usr/bin/perl
use strict;
use warnings;
use Fcntl;
use IO::Handle;
my $fn    = "test.txt";
my $newfn = "tmp.$$";
my $data  = "test.$$";
open my $fh, '>', $newfn
    or die "failed to open file:$newfn:$!";
print $fh $data;
IO::Handle::flush($fh)
    or die "flush failed:$!";
IO::Handle::sync($fh)
    or die "fsync failed:$!";
close $fh;
if (-f $fn) {
    unlink "$fn~" if -f "$fn~";
    link $fn, "$fn~"
        or die "failed to link $fn to $fn~:$!";
}
rename $newfn, $fn
    or die "failed to rename $newfn to $fn:$!";
sync_dir('.');
sub sync_dir {
  my $dir = shift;
  sysopen my $d, $dir, O_RDONLY
    or die "failed to open directory:$dir:$!";
  open my $d2, '>&', fileno($d)
    or die "dup(2) failed:$!";
  IO::Handle::sync($d2)
    or die "fsync(2) failed:$!";
}
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