Tcl

SCCS: @(#) README 1.39 97/01/29 13:27:40

1. Introduction
---------------

This directory and its descendants contain the sources and documentation
for Tcl, an embeddable scripting language.  The information here
corresponds to release 7.6p2, patch level 2 for Tcl 7.6.  This is
actually the first official patch release for Tcl 7.6: patch level 1 was
only released for the Macintosh. Tcl 7.6 is a relatively minor release
with bug fixes and a few new features, mostly to improve portability.
Tcl 7.6 should be backwards compatible with Tcl 7.5 scripts, but there
are two incompatible changes, one in the C APIs for custom channel
drivers and the other affecting start-up file names under Windows.  See
below for more details.

2. Documentation
----------------

The best way to get started with Tcl is to read one of the introductory
books on Tcl:

    Tcl and the Tk Toolkit, by John Ousterhout,
    Addison-Wesley, 1994, ISBN 0-201-63337-X

    Practical Programming in Tcl and Tk, by Brent Welch,
    Prentice-Hall, 1995, ISBN 0-13-182007-9

    Exploring Expect, by Don Libes,
    O'Reilly and Associates, 1995, ISBN 1-56592-090-2

The "doc" subdirectory in this release contains a complete set of reference
manual entries for Tcl.  Files with extension ".1" are for programs (for
example, tclsh.1); files with extension ".3" are for C library procedures;
and files with extension ".n" describe Tcl commands.  The file "doc/Tcl.n"
gives a quick summary of the Tcl language syntax.  To print any of the man
pages, cd to the "doc" directory and invoke your favorite variant of
troff using the normal -man macros, for example

		ditroff -man Tcl.n

to print Tcl.n.  If Tcl has been installed correctly and your "man"
program supports it, you should be able to access the Tcl manual entries
using the normal "man" mechanisms, such as

		man Tcl

There is also an official home for Tcl and Tk on the Web:
	http://www.sunlabs.com/research/tcl
These Web pages include release updates, reports on bug fixes and porting
issues, HTML versions of the manual pages, and pointers to many other
Tcl/Tk Web pages at other sites.  Check them out!

3. Compiling and installing Tcl
-------------------------------

This release contains everything you should need to compile and run
Tcl under UNIX, Macintoshes, and PCs (either Windows NT, Windows 95,
or Win 3.1 with Win32s).

Before trying to compile Tcl you should do the following things:

    (a) Check for a binary release.  Pre-compiled binary releases are
        available now for PCs, Macintoshes, and several flavors of UNIX.
	Binary releases are much easier to install than source releases.
	To find out whether a binary release is available for your platform,
	check the home page for the Sun Tcl/Tk project
	(http://www.sunlabs.com/research/tcl) and also check in the FTP
	directory from which you retrieved the base distribution.  Some
	of the binary releases are available freely, while others are for
	sale.

    (b) Make sure you have the most recent patch release.  Look in the
	FTP directory from which you retrieved this distribution to see
	if it has been updated with patches.  Patch releases fix bugs
	without changing any features, so you should normally use the
	latest patch release for the version of Tcl that you want. 
	Patch releases are available in two forms.  A file like
	tcl7.6p2.tar.Z is a complete release for patch level 2 of Tcl
	version 7.6.  If there is a file with a higher patch level than
	this release, just fetch the file with the highest patch level
	and use it.

	Patches are also available in the form of patch files that just
	contain the changes from one patch level to another.  These
	files will have names like tcl7.6p2.patch, tcl7.6p3.patch, etc. 
	They may also have .gz or .Z extensions to indicate compression.
	 To use one of these files, you apply it to an existing release
	with the "patch" program.  Patches must be applied in order,
	except that there is no patch level 1 for Tcl 7.6:
	tcl7.6p2.patch must be applied to an unpatched Tcl 7.6 release
	to produce a Tcl 7.6p2 release;  tcl7.6p3.patch can then be
	applied to Tcl7.6p2 to produce Tcl 7.6p3, and so on. To apply an
	uncompressed patch file such as tcl7.6p2.patch, invoke a shell
	command like the following from the directory containing this
	file:
	    patch -p < tcl7.6p2.patch
	If the patch file has a .gz extension, invoke a command like the
	following:
	    gunzip -c tcl7.6p2.patch.gz | patch -p
	If the patch file has a .Z extension, it was compressed with
	compress.  To apply it, invoke a command like the following:
	    zcat tcl7.6p2.patch.Z | patch -p
	If you're applying a patch to a release that has already been
	compiled, then before applying the patch you should cd to the
	"unix" subdirectory and type "make distclean" to restore the
	directory to a pristine state.

Once you've done this, change to the "unix" subdirectory if you're
compiling under UNIX, "win" if you're compiling under Windows, or
"mac" if you're compiling on a Macintosh.  Then follow the instructions
in the README file in that directory for compiling Tcl, installing it,
and running the test suite.

4. Summary of changes in Tcl 7.6
--------------------------------

Here are the most significant changes in Tcl 7.6.  In addition to these
changes, there are numerous small bug fixes.  See the file "changes" for
a complete list of all changes.

    1. New file manipulation commands.  There are new options to the
    "file" command for copying files ("file copy"), deleting files and
    directories ("file delete"), creating directories ("file mkdir"),
    and renaming files ("file rename").

    2. The implementation of "exec" has been improved greatly for Windows
    95 and Windows NT.

    3. The package loader has been modified to look for packages not only
    in the auto_path directories but also in their immediate descendants.
    This makes it much easier to install and uninstall packages.  There
    is now a new variable, tcl_pkgPath, which contains directories in
    which packages are normally installed, and these directories are
    automatically included in auto_path.

    4. There is a new memory allocator for the Macintosh version, which
    should be more efficient than the old one.

Tcl 7.6 contains two incompatible changes:
    1. The C interfaces to channel drivers have been revised to eliminate
    the use of Tcl_File handles in the interfaces.  Instead, there are
    new interface procedures channelReadyProc, watchChannelProc, and
    getFileProc.  This change does not affect Tcl scripts; it will only
    affect you if you have written a custom channel driver.

    2. Under Windows, tclsh now looks for the start-up file "tclshrc.tcl"
    instead of "tclsh.rc".  This is more consistent with wish and uses
    the right extension.

5. Tcl newsgroup
-----------------

There is a network news group "comp.lang.tcl" intended for the exchange
of information about Tcl, Tk, and related applications.  Feel free to use
the newsgroup both for general information questions and for bug reports.
We read the newsgroup and will attempt to fix bugs and problems reported
to it.

When using comp.lang.tcl, please be sure that your e-mail return address
is correctly set in your postings.  This allows people to respond directly
to you, rather than the entire newsgroup, for answers that are not of
general interest.  A bad e-mail return address may prevent you from
getting answers to your questions.  You may have to reconfigure your news
reading software to ensure that it is supplying valid e-mail addresses.

6. Tcl contributed archive
--------------------------

Many people have created exciting packages and applications based on Tcl
and/or Tk and made them freely available to the Tcl community.  An archive
of these contributions is kept on the machine ftp.neosoft.com.  You
can access the archive using anonymous FTP;  the Tcl contributed archive is
in the directory "/pub/tcl".  The archive also contains several FAQ
("frequently asked questions") documents that provide solutions to problems
that are commonly encountered by TCL newcomers.

7. Support and bug fixes
------------------------

We're very interested in receiving bug reports and suggestions for
improvements.  We prefer that you send this information to the
comp.lang.tcl newsgroup rather than to any of us at Sun.  We'll see
anything on comp.lang.tcl, and in addition someone else who reads 
comp.lang.tcl may be able to offer a solution.  The normal turn-around
time for bugs is 3-6 weeks.  Enhancements may take longer and may not
happen at all unless there is widespread support for them (we're
trying to slow the rate at which Tcl turns into a kitchen sink).  It's
very difficult to make incompatible changes to Tcl at this point, due
to the size of the installed base.

When reporting bugs, please provide a short tclsh script that we can
use to reproduce the bug.  Make sure that the script runs with a
bare-bones tclsh and doesn't depend on any extensions or other
programs, particularly those that exist only at your site.  Also,
please include three additional pieces of information with the
script:
    (a) how do we use the script to make the problem happen (e.g.
	what things do we click on, in what order)?
    (b) what happens when you do these things (presumably this is
        undesirable)?
    (c) what did you expect to happen instead?

The Tcl community is too large for us to provide much individual
support for users.  If you need help we suggest that you post questions
to comp.lang.tcl.  We read the newsgroup and will attempt to answer
esoteric questions for which no-one else is likely to know the answer.
In addition, Tcl support and training are available commercially from
NeoSoft (info@neosoft.com), Computerized Processes Unlimited
(gwl@cpu.com), and Data Kinetics (education@dkl.com).

8. Tcl version numbers
----------------------

Each Tcl release is identified by two numbers separated by a dot, e.g.
6.7 or 7.0.  If a new release contains changes that are likely to break
existing C code or Tcl scripts then the major release number increments
and the minor number resets to zero: 6.0, 7.0, etc.  If a new release
contains only bug fixes and compatible changes, then the minor number
increments without changing the major number, e.g. 7.1, 7.2, etc.  If
you have C code or Tcl scripts that work with release X.Y, then they
should also work with any release X.Z as long as Z > Y.

Alpha and beta releases have an additional suffix of the form a2 or b1.
For example, Tcl 7.0b1 is the first beta release of Tcl version 7.0,
Tcl 7.0b2 is the second beta release, and so on.  A beta release is an
initial version of a new release, used to fix bugs and bad features before
declaring the release stable.  An alpha release is like a beta release,
except it's likely to need even more work before it's "ready for prime
time".  New releases are normally preceded by one or more alpha and beta
releases.  We hope that lots of people will try out the alpha and beta
releases and report problems.  We'll make new alpha/beta releases to fix
the problems, until eventually there is a beta release that appears to
be stable.  Once this occurs we'll make the final release.

We can't promise to maintain compatibility among alpha and beta releases.
For example, release 7.1b2 may not be backward compatible with 7.1b1, even
though the final 7.1 release will be backward compatible with 7.0.  This
allows us to change new features as we find problems during beta testing.
We'll try to minimize incompatibilities between beta releases, but if
a major problem turns up then we'll fix it even if it introduces an
incompatibility.  Once the official release is made then there won't
be any more incompatibilities until the next release with a new major
version number.

Patch releases have a suffix such as p1 or p2.  These releases contain
bug fixes only.  A patch release (e.g Tcl 7.6p2) should be completely
compatible with the base release from which it is derived (e.g. Tcl
7.6), and you should normally use the highest available patch release.
