<! -- -*- tcl -*- doctools --> <html><head><title>null - Memory channels </title></head> <! -- Generated from file 'null.man' by tcllib/doctools with format 'html' --> <! -- Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net> --> <! -- CVS: $Id$ null.n --> <h1> null(n) 2.2 "Memory channels"</h1> <a name="name"><h2>NAME</h2> <p> null - Create and manipulate null channels <a name="synopsis"><h2>SYNOPSIS</h2> package require <b>Tcl</b><br> package require <b>memchan</b><br> <br><table border=1 width=100% cellspacing=0 cellpadding=0><tr bgcolor=lightyellow><td bgcolor=lightyellow><table 0 width=100% cellspacing=0 cellpadding=0><tr valign=top ><td ><b class='cmd'>null</b> </td></tr> </table></td></tr></table> <a name="description"><h2>DESCRIPTION</h2> <p> The command described here is only available in a not-yet released version of the package. Use the CVS to get the sources. <dl> <dt><b class='cmd'>null</b> <dd> 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. </dl> <a name="options"><h2>OPTIONS</h2> Memory channels created by <b class='cmd'>null</b> provide one additional option to set or query. <dl> <dt><i class='arg'>-delay ?milliseconds?</i><dd> A <b class='cmd'>null</b> channel is always writable and readable. This means that all <b class='cmd'>fileevent</b>-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. </dl> <p> A null channel is always writable and never readable. This means that a writable <b class='cmd'>fileevent</b>-handler will fire continuously and a readable <b class='cmd'>fileevent</b>-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. <a name="seealso"><h2>SEE ALSO</h2> memchan, fifo, fifo2, random, zero <a name="keywords"><h2>KEYWORDS</h2> null, in-memory channel, channel, i/o <a name="copyright"><h2>COPYRIGHT</h2> Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net><br> </body></html>