null -
Create and manipulate null channels
package require Tcl
package require memchan
null
The command described here is only available in a not-yet released
version of the package. Use the CVS to get the sources.
-
null
-
creates a null channel which absorbs everything written into
it. Reading from it is not possible, or rather will always return zero
bytes. These channels are essentially Tcl-specific variants of the
null device for unixoid operating systems (/dev/null). Transfering the
generated channel between interpreters is possible but does not make
much sense.
Memory channels created by
null provide one additional option to
set or query.
- -delay ? milliseconds ?
-
A null channel is always writable and readable. This means
that all fileevent-handlers will fire continuously. To
avoid starvation of other event sources the events raised by this
channel type have a configurable delay. This option is set in
milliseconds and defaults to 5.
A null channel is always writable and never readable. This means that a
writable fileevent-handler will fire continuously and a readable
fileevent-handler never at all. The exception to the latter is
only the destruction of the channel which will cause the delivery of
an eof event to a readable handler.
memchan, fifo, fifo2, random, zero
null, in-memory channel, channel, i/o