Named pipes

Cowdery, Bob [UK] Bob.Cowdery at
Sun Jan 1 10:00:56 UTC 2006

> Load OSProcess from Squeak Map.
> Make a named pipe called 'FIFO'.
> In Squeak, open the named pipe as a file stream:
>   namedPipe := FileStream fileNamed: 'FIFO'.
> Set nonblocking:
>   OSProcess accessor setNonBlocking: namedPipe fileID.
> Read from the pipe without blocking (answers an empty string):
>   namedPipe next: 10000
> As you have noticed, a blocking read will hang your Squeak VM if no
> data is available. But note that on Linux you can break things loose
> by going to /proc/<squeakPID>/fd/ and writing to whatever file
> descriptor is waiting for the data. This is handy if you have locked
> up Squeak and don't want to lose your work.
> If you set the file descriptor non-blocking with #setNonBlocking:, it
> will not hang up the VM. A read will give you the available data
> (possible an empty string if no data is ready).

> See also AioPlugin on Squeak Map for buffered event-driven input from
> a non-blocking file stream.

Thanks very much Dave. I figured most of it. The bit that got me was the
IOHandle that setNonBlocking wanted was a fileID. I am actually reading
audio sampled data in binary mode and get a nil when the pipe is empty.


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