On Oct 30, 2008, at 9:48 AM, Shad L. Lords wrote:

> Arno Lehmann wrote:
>> 30.10.2008 04:47, Dan Langille wrote:
>>> SZÉKELYI Szabolcs wrote:
>>>> I understand the concept, but I have problems with timing. I did  
>>>> a small
>>>> research on how FIFOs work. Consider the following script:
>>>>
>>>> ==
>>>> #!/bin/bash
>>>>
>>>> exec > /dev/null
>>>>
>>>> mkfifo /tmp/tmpfifo
>>>>
>>>> (
>>>>  for n in `seq 20`; do
>>>>    echo $n >/tmp/tmpfifo
>>>>    sleep 1
>>>>  done
>>>> ) &
>>>> ==
>>>>
>>>> Let's use this script to generate the data to be backed up, so it  
>>>> is run
>>>> from RunBeforeJob. Creates a FIFO, writes the numbers from 1 to  
>>>> 20 into
>>>> it, with a 1 second delay between them.
>>
>> You need to be aware that your loop does the following:
>> 1. open the FIFO for writing
>> 2. write into it
>> 3. close the FIFO
>> 4. sleep
>> 5. loop
>>
>> The important thing is that the FIFO is opened and closed for each  
>> write.
>>
>> If, on the other hand, you opened the FIFO in the surrounding code,
>> redirected your output to it (for testing, do it similarly as you do
>> with 'exec > /dev/null') and closed the FIFO once the loop is done
>> you'll see your cat reads all the numbers in one go.
>>
>> That's the difference.
>
> This was going to be my point as well.  Take your example and change  
> it
> to this and everything behaves as you expect:
>
> #!/bin/bash
>
> exec > /dev/null
>
> mkfifo /tmp/tmpfifo
>
> (
>   for n in `seq 20`; do
>     echo $n
>     sleep 1
>   done
> ) >/tmp/tmpfifo &


Nice. Thank  you

I hope the original poster replies back with test results from a  
Bacula job.

-- 
Dan Langille
http://langille.org/





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