How to tar a file while it's chaging

[Olaf Reitmaier Veracierta <olafrv@gmail.com>]

Hi,

In a backup shell script I tar a file but sometimes it's chaging because is a log file (plain/text).

While taring a get this error (warning) message:
/bin/tar: /var/log/postgresql/postgresql-8.1-main.log: file changed as we read it

The command return with a non-zero value (an error) but I can't found tar return codes in man.

¿There is a way to tar a file but ignore if the file is modified or may be a way to trunk the file?

Thanks.-

-- 
   "You don't know where your shadow will fall",
        Somebody.-
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