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Tcl by John Ousterhout (and many others at Sun Microsystems and elsewhere) john.ousterhout@eng.sun.com @(#) README 1.22 96/01/20 16:20:21 1. Introduction --------------- This directory and its descendants contain the sources and documentation for Tcl, an embeddable scripting language. The information here corresponds to release 7.5. The most important new feature in this release is support for the PC and Mac platforms. In addition, there are major new facilities for dynamic loading, package and version management, multiple interpreters, safe execution of untrusted scripts, and a new I/O system that supports nonblocking I/O and sockets. This release also contains many bug fixes. Tcl 7.5 should be backwards compatible with Tcl 7.4 scripts (there are two small incompatibilities described below, but they are relatively insignificant and shouldn't affect most existing Tcl code and extensions). 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 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 and Macintoshes, and they may be available in the future for some flavors of UNIX. Look in the FTP directory from which you retrieved the base distribution to see if a suitable binary release is available. If so, it will be much easier to install than the source release. (b) Check for patches. Look in the FTP directory from which you retrieved the base distribution and see if there are files with names like tcl7.5p1.patch, tcl7.5p2patch, etc. These files may also have .gz or .Z extensions to indicate compression. If you find any patch files, apply them to the source directory in order from "p1" up. To apply an uncompressed patch file such as tcl7.5p1.patch, invoke a shell command like the following from the directory containing this file: patch -p < tcl7.5p1.patch If the patch file has a .gz extension, invoke a command like the following: gunzip -c tcl7.5p1.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 tcl7.5p1.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. Additional release information --------------------------------- There is now an official home for Tcl and Tk on the Web at the following URL: http://www.smli.com/research/tcl These Web pages include release updates, reports on bug fixes and porting issues, and pointers to many other Tcl/Tk Web pages at other sites. Check them out! 5. Summary of changes in Tcl 7.5 -------------------------------- The main change for Tcl 7.5 is that Tcl now runs on Macintosh and PC platforms as well as UNIX. The PC port runs under Windows 3.1 (with Win32s), Windows 95, and Windows NT. This required a lot of reorganization of the sources but it didn't require any changes to Tcl's externally visible interfaces. In addition to the ports, Tcl 7.5 also has many other new features. The following feature changes have occurred since Tcl 7.4: 1. Dynamic loading. There is a new "load" command for loading binary extensions into Tcl on the fly. This works now on most of the major UNIX platforms (except AIX) as well as PCs and Macintoshes. Support for other platforms should become available over time. Two new "info" commands, "info sharedlibextension" and "info nameofexecutable", were also added as part of the dynamic loading implementation. You can also create Tcl and Tk themselves as shared libraries with the --enable-shared switch to the configure script. 2. Packages and versions. There is a new "package" command for package and version management. See the manual entries for "package" and "pkg_mkIndex" for details on how to use it. There are also C APIs to the package mechanism. See PkgRequire.3. 3. Multiple interpreters and Safe-Tcl. There is a new "interp" command that allows you to create multiple interpreters within a single application and set up communication between them with "aliases". The mechanism also supports "safe" interpreters, which provide a generalized version of the security mechanisms in Borenstein and Rose's Safe-Tcl. There are still a few missing security features, such as resource control. You can use "load" to add extensions (including Tk) into slave interpreters. 4. The event loop from Tk has been moved to Tcl. Tcl now has commands "after", "fileevent", "update", and "vwait" (which replaces tkwait). The "tkerror" command has been renamed to "bgerror". "Tkerror" is still supported for backwards compatibility, but you should switch ASAP to using "bgerror" instead. Many C procedures that used to be in Tk have been moved to Tcl and renamed, such as Tcl_DoOneEvent, Tcl_DoWhenIdle, Tcl_CreateFileHandler, and Tcl_CreateTimerHandler. 5. Tcl has a whole new I/O system. All of the Tcl commands like "open" and "puts" should continue to operate as before, but there is a totally new implementation that doesn't use the C stdio library: - The new I/O system is more portable, and it can be extended with new kinds of I/O channels; see CrtChannel.3 for details. - Nonblocking I/O is supported on all platforms and there is a new command "fconfigure" to enable it and other channel options; see fconfigure.n for details. There is also a new "fblocked" command. - The I/O system automatically translates between different end-of-line representations (such as CR on Macs and CRLF on PC's) to the newline form used in UNIX and in all Tcl scripts; the "fconfigure" command can be used to control this feature. - There is a set of C APIs for manipulating Tcl_Channel's, which are analogous to UNIX FILE's. The C procedures have roughly the same functionality as the stdio procedures. See OpenFileChnl.3, CrtCloseHdlr.3, and CrtChnlHdlr.3 for details. - There is a new structure Tcl_File which provides platform- independent access to file handles such as UNIX fd's. See GetFile.3 for details. - There are new procedures Tcl_GetErrno and Tcl_SetErrno for accessing the "errno" variable in a safe and portable fashion. See SetErrno.3. 6. File name manipulation has been improved to support different styles of names for different platforms, plus a universal "network file name" that should work everywhere. The "glob" command now works on all platforms. See the manual entries file.n and filename.n for details. 7. There is a new "socket" command for network communication via TCP sockets. It works for both the client and server sides. There is also C-level support for sockets; see OpenTcp.3. 8. There is a new "clock" command, which contains the functionality of the TclX clock-handling commands. 9. The "foreach" command has been generalized significantly to support multiple lists and multiple variables iterating over each list. 10. There is a new "notifier" mechanism, which was added as part of the ports. This allows the basic mechanisms for reporting events to be implemented in different ways on different platforms. It may also be useful for other purposes, such as merging the Tk and Xt event loops so that Tk and Xt widgets can coexist in a single application. See the manual entry Notifier.3 for more information. 11. There is an "AssocData" mechanism that allows extensions to store their own data in an interpreter and get called back when the interpreter is deleted. This is visible at C level via the procedures Tcl_SetAssocData and Tcl_GetAssocData. 12. When manual pages are installed, additional links are created for each of the procedures described in the manual page, so that it's easier to invoke the "man" command. 13. There is a new variable "tcl_platform" with platform information. This is an associative array with elements like "os" and "machine" that contain various pieces of information about the platform. 14. There is a new procedure Tcl_CreateExitHandler that you can use to make sure a C procedure is called before the Tcl application exits. 15. There is a new procedure Tcl_UpdateLinkedVar to force the Tcl-level variable to be updated after you've changed the corresponding C-level variable. 16. The procedures Tk_Preserve, Tk_Release, and Tk_EventuallyFree have been moved from Tk to Tcl and given names like Tcl_Preserve. Three incompatibilities were introduced by the changes. All of these are at C-level, and only the first one should have much impact. Existing scripts for Tcl 7.4 should run unchanged under Tcl 7.5. 1. The procedures Tcl_EnterFile and Tcl_GetOpenFile no longer exist; they are not compatible with the new I/O system, but there are other ways to get the same effect. 1. Tcl doesn't export any global C variables anymore, because this doesn't work with Windows DLLs. The C variables tcl_AsyncReady and tcl_FileCloseProc have been replaced with procedures Tcl_AsyncReady() and Tcl_SetFileCloseProc(). The C variable tcl_RcFileName has been replaced with a Tcl variable tcl_rcFileName. 2. Files are no longer shared between interpreters by default: if a file is opened in one interpreter, it cannot normally be used in other interpreters. However, the new procedure Tcl_ShareHandle allows files to be shared between interpreters if requested explicitly. For a complete list of all changes in this release, see the file "changes" in this directory. 6. 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. 7. Tcl contributed archive -------------------------- Many people have created exciting packages and applications based on Tcl and made them freely available to the Tcl community. An archive of these contributions is kept on the machine ftp.aud.alcatel.com. You can access the archive using anonymous FTP; the Tcl contributed archive is in the directory "/tcl". The archive also contains several FAQ ("frequently asked questions") documents that provide solutions to problems commonly encountered by TCL newcomers. 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 omp.lang.tcl may be able to offer a solution. The normal turn-around time for bugs is 2-4 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). 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 version number.