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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.

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