null.3tcl

Langue: en

Version: 2.2 (debian - 07/07/09)

Section: 3 (Bibliothèques de fonctions)

Sommaire

NAME

null - Create and manipulate null channels

SYNOPSIS

package require Tcl

package require memchan

null

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 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.

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 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.

SEE ALSO

memchan, fifo, fifo2, random, zero

KEYWORDS

null, in-memory channel, channel, i/o 
 Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>