CentOS - Sep 2007 - Runing a script under cron. Append stdout and stderr to a log file, propagate stderr back to cron for email reporting

Dear List,

I want to run a rsync-ing script in cron, generating a very verbose
-vv rsync log in a log file. The log file should combine both stderr
and stdin, which is easy:

     backup.sh >>/var/log/backup.log 2>&1

However, I would like to propagate only stderr to cron - in case there
has been an error, cron will mail me the assembled stderr output.

I tried the following:

$ (./backup.sh > /var/log/backup.log) 2>&1 | tee -a
/var/log/backup.log

which propagates the stderr to cron, but lines written to
/var/log/backup.log are out of sequence - for example if the contents
of backup.sh are:

#!/bin/bash

echo "out 1" >&1
echo "out 2" >&1
echo "out 3" >&1
echo "out 4" >&1
echo "err 5" >&2
echo "out 6" >&1
echo "out 7" >&1
echo "out 8" >&1

I get in /var/log/backup.log:

out 1
out 2
out 3
out 4
out 6
out 7
out 8
err 5

I would like the lines in their initial sequence.

Do you know a shell trick or a tool that I can use to achive desired goal?

Best regards,
alex

On Sat, 2007-09-22 at 17:11 +0300, Alexander Georgiev
wrote:
> I would like the lines in their initial sequence.
> 
> Do you know a shell trick or a tool that I can use to achive desired goal?
Can't be done. stdout and stderr aren't synchronized.

-- 
Ignacio Vazquez-Abrams <ivazqueznet at gmail.com>

PLEASE don't CC me; I'm already subscribed
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