Re: Blocking read() from a USB->Serial adapter.

Grant Edwards <grante@xxxxxxxx> wrote:
On 2006-11-25, Floyd L. Davidson <floyd@xxxxxxxxxx> wrote:
Grant Edwards <grante@xxxxxxxx> wrote:
On 2006-11-25, Charles Sullivan <cwsulliv@xxxxxxxxxxxx> wrote:

If that's the case, then that answers my questions. I thought
blocking meant blocking until the specified number of
characters is read, or until the read is interrupted.

Or until the driver decides to return for whatever reason it
chooses. On success, you're guaranteed a minimum of one byte.

Maybe. (Maybe not too!)

There's the case where the file is at EOF. Is there another
case where read() will return success with 0 bytes?

Any time there is no data available. With a file that will
indeed set the EOF flag, but with a serial port (or a pipe, or a
console) there is no such concept.

If the timer is enabled, and times out, read() will return 0.
Another possibility is if the number of bytes request was 0,
read() will return 0.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.

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