NAME

    IO::File::AtomicChange - change content of a file atomically

SYNOPSIS

    truncate and write to temporary file. When you call $fh->close, replace
    target file with temporary file preserved permission and owner (if
    possible).

        use IO::File::AtomicChange;
        
        my $fh = IO::File::AtomicChange->new("foo.conf", "w");
        $fh->print("# create new file\n");
        $fh->print("foo\n");
        $fh->print("bar\n");
        $fh->close; # MUST CALL close EXPLICITLY

    If you specify "backup_dir", save original file into backup directory
    (like "/var/backup/foo.conf_YYYY-MM-DD_HHMMSS_PID") before replace.

        my $fh = IO::File::AtomicChange->new("foo.conf", "a",
                                             { backup_dir => "/var/backup/" });
        $fh->print("# append\n");
        $fh->print("baz\n");
        $fh->print("qux\n");
        $fh->close; # MUST CALL close EXPLICITLY

DESCRIPTION

    IO::File::AtomicChange is intended for people who need to update files
    reliably and atomically.

    For example, in the case of generating a configuration file, you should
    be careful about aborting generator program or be loaded by other
    program in halfway writing.

    IO::File::AtomicChange free you from such a painful situation and
    boring code.

INTERNAL

        * open
          1. fix filename of temporary file by mktemp.
          2. if target file already exists, copy target file to temporary file preserving permission and owner.
          3. open temporary file and return its file handle.
        
        * write
          1. write date into temporary file.
        
        * close
          1. close temporary file.
          2. if target file exists and specified "backup_dir" option, copy target file into backup directory preserving permission and owner, mtime.
          3. rename temporary file to target file.

CAVEATS

    You must call "$fh->close" explicitly when commit changes.

    Currently, "close $fh" or "undef $fh" don't affect target file. So if
    you exit without calling "$fh->close", CHANGES ARE DISCARDED.

AUTHOR

    HIROSE Masaaki <hirose31 _at_ gmail.com>

THANKS TO

    kazuho gave me many shrewd advice.

REPOSITORY

    https://github.com/hirose31/IO-File-AtomicChange

      git clone git://github.com/hirose31/IO-File-AtomicChange.git

    patches and collaborators are welcome.

SEE ALSO

    IO::File, IO::AtomicFile, File::AtomicWrite

COPYRIGHT & LICENSE

    Copyright HIROSE Masaaki 2009-

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

    # for Emacsen # Local Variables: # mode: cperl # cperl-indent-level: 4
    # cperl-close-paren-offset: -4 # cperl-indent-parens-as-block: t #
    indent-tabs-mode: nil # coding: utf-8 # End:

    # vi: set ts=4 sw=4 sts=0 et ft=perl fenc=utf-8 ff=unix :

