--- name: "null" section: "3tcl" platform: "linux" package: "tcl-memchan" version: "2.3+dfsg-2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/null" --- # null(3tcl) Create and manipulate null channels ``` ``` ## 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). Transferring 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 fifo, fifo2, memchan, random, zero ## KEYWORDS channel, i/o, in-memory channel, null ## COPYRIGHT ``` Copyright (c) 1996-2003 Andreas Kupries ```