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null(n) null(n)
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NAME
null - Create and manipulate null channels
SYNOPSIS
package require Tcl
package require memchan
null
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DESCRIPTION
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 possi-ble, possible,
ble, 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 gener-ated generated
ated channel between interpreters is possible but does not make much sense.
OPTIONS
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 chan-nel channel
nel 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 han-dler. handler.
dler.
SEE ALSO
fifo, fifo2, memchan, random, zero
KEYWORDS
channel, i/o, in-memory channel, null
COPYRIGHT
Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>
Memory channels 2.2 null(n)
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