File::Unsaved - Check whether file has unsaved modification in an editor


This document describes version 0.06 of File::Unsaved (from Perl distribution File-Unsaved), released on 2017-07-11.


 use File::Unsaved qw(check_unsaved_file);
 die "Can't modify foo.txt because it is being opened and modified in an editor"
     if check_unsaved_file(path => "foo.txt");





 check_unsaved_file(%args) -> bool|hash

Check whether file has unsaved modification in an editor.

This function tries, using some heuristics, to find out if a file is being opened and has unsaved modification in an editor. Currently the supported editors are: Emacs, joe, vim.

The heuristics are as folow:

  • Emacs, joe, mc: check whether .#<name> symlink exists. Emacs targets the symlink to <user>@<host>.<PID>:<timestamp> while joe and mc to <user>@<host>.<PID>. Caveat: Unix only.

  • vim: check whether .<name>.swp file exists, not older than file, and its 0x03ef-th byte has the value of U (which vim uses to mark the file as unsaved). Caveat: vim can be instructed to put swap file somewhere else or not create swap file at all, so in those cases unsaved data will not be detected.

This function is not exported by default, but exportable.

Arguments ('*' denotes required arguments):

  • check_pid => bool (default: 1)

    Whether to check that PID is actually an editor.

    A temporary file might be stale, so checking the existence of temporary file is not enough. If the temporary file provides pointer to a PID, and this setting is set to true, will actually check that the PID exists.

  • check_proc_name => bool (default: 1)

    Whether to check that process name is actually the corresponding editor.

    Is activated only check_pid is also 1 and if Proc::Find (and thus Proc::ProcessTable) is available.

    Might produce a false negative if you happen to rename the editor or use a differently-named fork/derivative of said editor, although this should be rare.

  • path* => str

Return value: (bool|hash)

Return false if no unsaved data is detected, or else a hash structure. Hash will contain these keys: editor (kind of editor, possible values: emacs, joe/mc, joe, mc, vim) and might contain these keys: pid (PID of editor), user, host, timestamp.


Please visit the project's homepage at


Source repository is at


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.



perlancar <>


This software is copyright (c) 2017, 2015, 2014 by

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.