
[//000000001]: # (tcl::transform::observe \- Reflected/virtual channel support)
[//000000002]: # (Generated from file 'observe\.man' by tcllib/doctools with format 'markdown')
[//000000003]: # (Copyright &copy; 2009 Andreas Kupries <andreas\_kupries@users\.sourceforge\.net>)
[//000000004]: # (tcl::transform::observe\(n\) 1\.1 tcllib "Reflected/virtual channel support")

<hr> [ <a href="../../../../toc.md">Main Table Of Contents</a> &#124; <a
href="../../../toc.md">Table Of Contents</a> &#124; <a
href="../../../../index.md">Keyword Index</a> &#124; <a
href="../../../../toc0.md">Categories</a> &#124; <a
href="../../../../toc1.md">Modules</a> &#124; <a
href="../../../../toc2.md">Applications</a> ] <hr>

# NAME

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

# <a name='toc'></a>Table Of Contents

  - [Table Of Contents](#toc)

  - [Synopsis](#synopsis)

  - [Description](#section1)

  - [API](#section2)

  - [Bugs, Ideas, Feedback](#section3)

  - [Keywords](#keywords)

  - [Category](#category)

  - [Copyright](#copyright)

# <a name='synopsis'></a>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*](#1)  

# <a name='description'></a>DESCRIPTION

The __tcl::transform::observer__ package provides a command creating a
channel transformation which passes the read and written bytes through unchanged
\(like __[tcl::transform::identity](identity\.md)__\), 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](adler32\.md)__,
__[tcl::transform::counter](vt\_counter\.md)__,
__[tcl::transform::crc32](vt\_crc32\.md)__, and
__[tcl::transform::identity](identity\.md)__\.

The internal __[TclOO](\.\./\.\./\.\./\.\./index\.md\#tcloo)__ class implementing
the transform handler is a sub\-class of the
__[tcl::transform::core](\.\./virtchannel\_core/transformcore\.md)__
framework\.

# <a name='section2'></a>API

  - <a name='1'></a>__::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\.

# <a name='section3'></a>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](http://core\.tcl\.tk/tcllib/reportlist)\. 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\.

# <a name='keywords'></a>KEYWORDS

[channel transformation](\.\./\.\./\.\./\.\./index\.md\#channel\_transformation),
[observer](\.\./\.\./\.\./\.\./index\.md\#observer), [reflected
channel](\.\./\.\./\.\./\.\./index\.md\#reflected\_channel), [stream
copy](\.\./\.\./\.\./\.\./index\.md\#stream\_copy), [tip
230](\.\./\.\./\.\./\.\./index\.md\#tip\_230),
[transformation](\.\./\.\./\.\./\.\./index\.md\#transformation), [virtual
channel](\.\./\.\./\.\./\.\./index\.md\#virtual\_channel)

# <a name='category'></a>CATEGORY

Channels

# <a name='copyright'></a>COPYRIGHT

Copyright &copy; 2009 Andreas Kupries <andreas\_kupries@users\.sourceforge\.net>
