BASH redirect & grep -v help needed

[dave selby]

2009/2/18 Smoot Carl-Mitchell <smoot at tic.com>:
> On Wed, 2009-02-18 at 21:34 +0000, dave selby wrote:
>> >> So any idea why xxx.out contains zsip instead of the above ?
>> >
>> > No idea.  What happens without the stderr redirection?
>>
>> motion -c /home/dave/kmotion2/core/motion_conf/motion.conf 2>&1 | grep
>> -v 'saved to'
>>
>> works a treat. 'motion' starts, outputs and keeps running and I have
>> to ctrl-c to stop it.
>>
>> motion -c /home/dave/kmotion2/core/motion_conf/motion.conf 2>&1 | grep
>> -v 'saved to' >> xxx.out
>>
>> outputs nothing, but zip in xxx.out
>>
>> I am wondering if the output to the BASH shell is 'instant' but the
>> output to >> is only processed on 'motion' ending
>> in some way ?
>
> Are you saying "motion -c" has continuous output?

It appears to have.

 If that is the case
> then you are seeing I/O buffering side effects.  Try adding
> --line-buffered to the grep command.  That will flush the output buffer
> after each line.

OK I did not realize grep could do this. Many thanks, Sorry for the
delay, work related

Cheers

Dave



> Smoot Carl-Mitchell
> Computer Systems and
> Network Consultant
> smoot at tic.com
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