perl - 等待文件更新然后在 Perl 中读取文件的好方法是什么？

Question

我想知道是否有一种方法可以等待文件更新，然后在更新后从中读取。因此，如果我有 file.txt，我想等到有新内容写入其中，然后读取它/处理它/等等。目前我正在使用 Time::HiRes::sleep(.01) 进行轮询，但我想知道是否有更好的方法。谢谢。

Answer 1

是的，有更好的方法。在 Windows 上，您可以使用 FileSystemWatcher接口(interface)，在 Linux 上，使用 inotify 。

Windows

use Win32::FileSystem::Watcher;

my $watcher = Win32::FileSystem::Watcher->new( "c:\\" );

# or

my $watcher = Win32::FileSystem::Watcher->new(
    "c:\\",
    notify_filter  => FILE_NOTIFY_ALL,
    watch_sub_tree => 1,
);

$watcher->start();
print "Monitoring started.";

sleep(5);

# Get a list of changes since start().
my @entries = $watcher->get_results();

# Get a list of changes since the last get_results()
@entries = $watcher->get_results();

# ... repeat as needed ...

$watcher->stop(); # or undef $watcher

foreach my $entry (@entries) {
    print $entry->action_name . " " . $entry->file_name . "\n";
}

# Restart monitoring

# $watcher->start();
# ...
# $watcher->stop();

Linux

use Linux::Inotify2;
my $inotify = new Linux::Inotify2();

foreach (@ARGV)
{
  $inotify->watch($_, IN_ALL_EVENTS);
}

while (1)
{
  # By default this will block until something is read
  my @events = $inotify->read();
  if (scalar(@events)==0)
  {
    print "read error: $!";
    last;
  }

  foreach (@events)
  {
    printf "File: %s; Mask: %d\n", $_->fullname, $_->mask;
  }
}