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# tcl::transform::observe(n) 1.1 tcllib "Reflected/virtual channel support"

## Name

tcl::transform::observe - Observer transformation, stream copy

## Synopsis

- package require Tcl 8.6 9
- package require tcl::transform::core ?1.1?
- package require tcl::transform::observe ?1.1?

- ::tcl::transform::observe chan logw logr

## Description

The tcl::transform::observer package provides a command creating a channel transformation which passes the read and written bytes through unchanged (like tcl::transform::identity), but additionally copies the data it has seen for each direction into channels specified at construction time.

Related transformations in this module are tcl::transform::adler32, tcl::transform::counter, tcl::transform::crc32, and tcl::transform::identity.

The internal TclOO class implementing the transform handler is a sub-class of the tcl::transform::core framework.

## API

::tcl::transform::observe chan logw logr

  This command creates an observer transformation on top of the channel chan and returns its handle. The channel handles logr and logw are there the data is copied to.

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category virtchannel 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.

## Keywords

channel transformation, observer, reflected channel, stream copy, tip 230, transformation, virtual channel

## Category

Channels

## Copyright

Copyright © 2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>