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

[Dale R. Worley]

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