IO::Async::File(3)

NAME
"IO::Async::File" - watch a file for changes

SYNOPSIS
   use IO::Async::File;

   use IO::Async::Loop;
   my $loop = IO::Async::Loop->new;

   my $file = IO::Async::File->new(
      filename => "config.ini",
      on_mtime_changed => sub {
         my ( $self ) = @_;
         print STDERR "Config file has changed\n";
         reload_config( $self->handle );
      }
   );

   $loop->add( $file );

   $loop->run;

DESCRIPTION
This subclass of IO::Async::Notifier watches an open filehandle or named filesystem entity for changes in its stat() fields. It invokes various events when the values of these fields change. It is most often used to watch a file for size changes; for this task see also IO::Async::FileStream.

While called "File", it is not required that the watched filehandle be a regular file. It is possible to watch anything that stat(2) may be called on, such as directories or other filesystem entities.

Since version 0.805 a named file does not necessarily need to exist. If it is not present, all its stat() fields are treated as undefined; events will be invoked when it becomes present or is removed, in addition to any changes.

EVENTS
The following events are invoked, either using subclass methods or CODE references in parameters.

  on_dev_changed $new_dev, $old_dev

  on_ino_changed $new_ino, $old_ino

  ...

  on_ctime_changed $new_ctime, $old_ctime
Invoked when each of the individual stat() fields have changed. All the stat() fields are supported apart from "blocks" and "blksize". Each is passed the new and old values of the field. Either field may be "undef" if the file did not or currently does not exist.

  on_devino_changed $new_stat, $old_stat
Invoked when either of the "dev" or "ino" fields have changed. It is passed two File::stat instances containing the complete old and new stat() fields. This can be used to observe when a named file is renamed; it will not be observed to happen on opened filehandles.

  on_stat_changed $new_stat, $old_stat
Invoked when any of the stat() fields have changed. It is passed two File::stat instances containing the old and new stat() fields. Either value may be "undef" if the file did not or currently does not exist.

PARAMETERS
The following named parameters may be passed to "new" or "configure".

  handle => IO
The opened filehandle to watch for stat() changes if "filename" is not supplied.

  filename => STRING
Optional. If supplied, watches the named file rather than the filehandle given in "handle". The file will be opened for reading and then watched for renames. If the file is renamed, the new filename is opened and tracked similarly after closing the previous file.

  interval => NUM
Optional. The interval in seconds to poll the filehandle using stat(2) looking for size changes. A default of 2 seconds will be applied if not defined.

METHODS

  handle
   $handle = $file->handle;

Returns the filehandle currently associated with the instance; either the one passed to the "handle" parameter, or opened from the "filename" parameter.

AUTHOR
Paul Evans <leonerd@leonerd.org.uk>