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term::receive::bind(3tcl) Terminal control term::receive::bind(3tcl)


term::receive::bind - Keyboard dispatch from terminals


package require Tcl 8.4

package require term::receive::bind ?0.1?

term::receive::bind object ?map?

object map str cmd

object default cmd

object listen ?chan?

object unlisten ?chan?

object reset

object next char

object process str

object eof


This package provides a class for the creation of simple dispatchers from character sequences to actions. Internally each dispatcher is in essence a deterministic finite automaton with tree structure.


The package exports a single command, the class command, enabling the creation of dispatcher instances. Its API is:

This command creates a new dispatcher object with the name object, initializes it, and returns the fully qualified name of the object command as its result.

The argument is a dictionary mapping from strings, i.e. character sequences to the command prefices to invoke when the sequence is found in the input stream.


The objects created by the class command provide the methods listed below:

This method adds an additional mapping from the string str to the action cmd. The mapping will take effect immediately should the processor be in a prefix of str, or at the next reset operation. The action is a command prefix and will be invoked with one argument appended to it, the character sequence causing the invokation. It is executed in the global namespace.
This method defines a default action cmd which will be invoked whenever an unknown character sequence is encountered. The command prefix is handled in the same as the regular action defined via method map.
This methods sets up a filevent listener for the channel with handle chan and invokes the dispatcher object whenever characters have been received, or EOF was reached.

If not specified chan defaults to stdin.

This methods removes the filevent listener for the channel with handle chan.

If not specified chan defaults to stdin.

This method resets the character processor to the beginning of the tree.
This method causes the character processor to process the character c. This may simply advance the internal state, or invoke an associated action for a recognized sequence.
This method causes the character processor to process the character sequence str, advancing the internal state and invoking action as necessary. This is a callback for listen.
This method causes the character processor to handle EOF on the input. This is currently no-op. This is a callback for listen.


The simplicity of the DFA means that it is not possible to recognize a character sequence with has a another recognized character sequence as its prefix.

In other words, the set of recognized strings has to form a prefix code.


This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category term of the Tcllib Trackers []. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.


character input, control, dispatcher, listener, receiver, terminal


Terminal control


Copyright (c) 2006 Andreas Kupries <>
0.1 tcllib