Re: [Bug-wget] wget in a 'dynamic' pipe

[Tim Rühsen]

On 9/11/18 5:34 AM, Dale R. Worley wrote:
> Paul Wagner <address@hidden> writes:
>> Now I tried
>>
>>    { i=1; while [[ $i != 100 ]]; do echo 
>> "http://domain.com/path/segment_$((i++)).mp4"; done } | wget -O foo.mp4 
>> -i -
>>
>> which works like a charm *as long as the 'generator process' is finite*, 
>> i.e. the loop is actually programmed as in the example.  The problem is 
>> that it would be much easier if I could let the loop run forever, let 
>> wget get whatever is there and then fail after the counter extends to a 
>> segment number not available anymore, which would in turn fail the whole 
>> pipe.
> 
> Good God, this finally motivates me to learn about Bash coprocesses.
> 
> I think the answer is something like this:
> 
>     coproc wget -O foo.mp4 -i -
> 
>     i=1
>     while true
>     do
>         rm -f foo.mp4
>         echo "http://domain.com/path/segment_$((i++)).mp4" >&$wget[1]
>         sleep 5
>         # The only way to test for non-existence of the URL is whether the
>         # output file exists.
>         [[ ! -e foo.mp4 ]] && break
>         # Do whatever you already do to wait for foo.mp4 to be completed and
>         # then use it.
>     done
> 
>     # Close wget's input.
>     exec $wget[1]<&-
>     # Wait for it to finish.
>     wait $wget_pid
> 
> Dale

Thanks for the pointer to coproc, never heard of it ;-) (That means I
never had a problem that needed coproc).

Anyways, copy&pasting the script results in a file '[1]' with bash 4.4.23.

Also, wget -i - waits with downloading until stdin has been closed. How
can you circumvent that ?

Regards, Tim

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