SCCS: @(#) README 1.49 97/08/14 08:47:31
This directory and its descendants contain the sources and documentation
for Tcl, an embeddable scripting language. The information here
corresponds to release 8.0. Tcl 8.0 is a major new release that replaces
the core of the interpreter with an on-the-fly bytecode compiler to
improve execution speed. It also includes several other new features
such as namespaces and binary I/O, plus many bug fixes. The compiler
introduces a few incompatibilities that may affect existing Tcl scripts;
the incompatibilities are relatively obscure but may require
modifications to some old scripts before they can run with this version.
The compiler introduces many new C-level APIs, but the old APIs are
still supported. See below for more details.
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
There is also an official home for Tcl and Tk on the Web:
These Web pages include information about the latest releases, products
related to Tcl and Tk, 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 SunScript
(http://sunscript.sun.com) under "Tech Corner". 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
tcl8.0p1.tar.Z is a complete release for patch level 1 of Tcl
version 8.0. 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 tcl8.0p1.patch, tcl8.0p2.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:
tcl8.0p1.patch must be applied to an unpatched Tcl 8.0 release
to produce a Tcl 8.0p1 release; tcl8.0p2.patch can then be
applied to Tcl8.0p1 to produce Tcl 8.0p2, and so on. To apply an
uncompressed patch file such as tcl8.0p1.patch, invoke a shell
command like the following from the directory containing this
patch -p < tcl8.0p1.patch
If the patch file has a .gz extension, invoke a command like the
gunzip -c tcl8.0p1.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 tcl8.0p1.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 8.0
Here are the most significant changes in Tcl 8.0. In addition to these
changes, there are several smaller changes and bug fixes. See the file
"changes" for a complete list of all changes.
1. Bytecode compiler. The core of the Tcl interpreter has been
replaced with an on-the-fly compiler that translates Tcl scripts to
byte codes; a new interpreter then executes the byte codes. In
earlier versions of Tcl, strings were used as a universal
representation; in Tcl 8.0 strings are replaced with Tcl_Obj
structures ("objects") that can hold both a string value and an
internal form such as a binary integer or compiled bytecodes. The
new objects make it possible to store information in efficient
internal forms and avoid the constant translations to and from
strings that occurred with the old interpreter. We have not yet
converted all of Tcl to take full advantage of the compiler and
objects and have not converted any of Tk yet, but even so you
should see speedups of 2-3x on many programs and you may see
speedups as much as 10-20x in some cases (such as code that
manipulates long lists). Future releases should achieve even
greater speedups. The compiler introduces only a few minor changes
at the level of Tcl scripts, but it introduces many new C APIs for
managing objects. See, for example, the manual entries doc/*Obj*.3.
2. Namespaces. There is a new namespace mechanism based on the
namespace implementation by Michael McLennan of Lucent Technologies.
This includes new "namespace" and "variable" commands. There are
many new C APIs associated with namespaces, but they will not be
exported until Tcl 8.1. Note: the syntax of the namespace command
has been changed slightly since the b1 release. See the changes
file for details.
3. Binary I/O. The new object system in Tcl 8.0 supports binary
strings (internally, strings are counted in addition to being null
terminated). There is a new "binary" command for inserting and
extracting data to/from binary strings. Commands such as "puts",
"gets", and "read" commands now operate correctly on binary data.
There is a new variable tcl_platform(byteOrder) to identify the
native byte order for the current host.
4. Random numbers. The "expr" command now contains a random number
generator, which can be accessed via the "rand()" and "srand()" math
5. Safe-Tcl enhancements. There is a new "hidden command"
mechanism, implemented with the Tcl commands "interp hide", "interp
expose", "interp invokehidden", and "interp hidden" and the C APIs
Tcl_HideCommand and Tcl_ExposeCommand. There is now support for
safe packages and extension loading, including new library
procedures such as safe::interpCreate (see the manual entry safe.n
6. There is a new package "registry" available under Windows for
accessing the Windows registry.
7. There is a new command "file attributes" for getting and setting
things like permissions and owner. There is also a new command
"file nativename" for getting back the platform-specific name for a
8. There is a new "fcopy" command to copy data between channels.
This replaces and improves upon the not-so-secret unsupported old
9. There is a new package "http" for doing GET, POST, and HEAD
requests via the HTTP/1.0 protocol. See the manual entry http.n
10. There are new library procedures for finding word breaks in
strings. See the manual entry library.n for details.
11. There are new C APIs Tcl_Finalize (for cleaning up before
unloading the Tcl DLL) and Tcl_Ungets for pushing bytes back into a
channel's input buffer.
12. Tcl now supports serial I/O devices on Windows and Unix, with a
new fconfigure -mode option. The Windows driver does not yet
support event-driven I/O.
13. The lsort command has new options -dictionary and -index. The
-index option allows for very rapid sorting based on an element
of a list.
14. The event notifier has been completely rewritten (again). It
should now allow Tcl to use an external event loop (like Motif's)
when it is embedded in other applications. No script-level
interfaces have changed, but many of the C APIs have.
Tcl 8.0 introduces the following incompatibilities that may affect Tcl
scripts that worked under Tcl 7.6 and earlier releases:
1. Variable and command names may not include the character sequence
"::" anymore: this sequence is now used as a namespace separator.
2. The semantics of some Tcl commands have been changed slightly to
maximize performance under the compiler. These incompatibilities
are documented on the Web so that we can keep the list up-to-date.
See the URL http://www.sunlabs.com/research/tcl/compiler.html.
3. 2-digit years are now parsed differently by the "clock" command
to handle year 2000 issues better (years 00-38 are treated as
2000-2038 instead of 1900-1938).
4. The old Macintosh commands "cp", "mkdir", "mv", "rm", and "rmdir"
are no longer supported; all of these features are now available on
all platforms via the "file" command.
5. The variable tcl_precision is now shared between interpreters
and defaults to 12 digits instead of 6; safe interpreters cannot
modify tcl_precision. The new object system in Tcl 8.0 causes
floating-to-string conversions (and the associated rounding) to
occur much less often than in Tcl 7.6, which can sometimes cause
6. The C APIs associated with the notifier have changed substantially.
7. The procedures Tcl_CreateModalTimeout and Tcl_DeleteModalTimeout
have been removed.
8. Tcl_CreateFileHandler and Tcl_DeleteFileHandler now take Unix
fd's and are only supported on the Unix platform
9. The C APIs for creating channel drivers have changed as part of
the new notifier implementation. The Tcl_File interfaces have been
removed. Tcl_GetChannelFile has been replaced with
Tcl_GetChannelHandle. Tcl_MakeFileChannel now takes a platform-
specific file handle. Tcl_DriverGetOptionProc procedures now take
an additional interp argument.
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
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. Mailing lists
A couple of Mailing List have been set up to discuss Macintosh or
Windows related Tcl issues. In order to use these Mailing Lists you
must have access to the internet. If you have access to the WWW the
home pages for these mailing lists are located at the following URLs:
The home pages contain information about the lists and an HTML archive
of all the past messages on the list. To subscribe send a message to:
In the body of the message (the subject will be ignored) put:
subscribe mactcl Joe Blow
Replacing Joe Blow with your real name, of course. (Use wintcl
instead of mactcl if your interested in the Windows list.) If you
would just like to receive more information about the list without
subscribing put the line:
in the body instead (or wintcl).
8. 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
(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
(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 (email@example.com), Computerized Processes Unlimited
(firstname.lastname@example.org), and Data Kinetics (email@example.com).
9. 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
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.