The Linux Tcl and Tk HOWTO - The Linux Documentation Project
Contents
1. 6 1 Some of the most common complaints about Tcl Tcl is interpreted The data is primarily treated as strings programs written in Tcl are slow Tcl 8 x attempts to address this by doing some degree of compilation as well as permitting additional variable types Several characteristics are not intuitive Comments are commands rather than traditional comments numbers beginning with 0 are octal proper use of quoting mechanisms etc These aspects are covered in the various FAQs 6 Scripting Language pros and cons 11 The Linux Tcl and Tk HOWTO 6 2 Some of the most pros about Tcl It is a high level scripting language You need to write a lot less code to get your job done especially when compared to Motif or Win32 applications In general the number of Line Of Code LOC of a software project is one of the most important complexity index es Tcl is free You can get the sources for free over the Internet from Scriptics Download Page or from the FTP site for Tcl The software c ore site includes the source code version as well as binary versions for Windows and Macintosh platforms or you can get Tcl on a number of CD ROMs for a nominal cost Read about Tcl and Tk core free at www scriptics com about n ews qga html It runs on many platforms Versions exist for UNIX Linux of course Windows and Macintosh Except for a few platform differences your Tcl scripts will run the same way on all systems It is interpreted2. A EAE I A A TA ote E A E T 5 BGI A a EES casas sassy E E RT NEEE EIE ASEE PEE ceo as enna E I E ar EET IEN 5 PAE EEO a E T E E E E E E T 3 S EEN ENA A e A IEE E E PE E E EEE cai EEE A E A EEEE N E A E E E AE T E E E TE 5 e NE T A e AEEA EE EA E EEN Ts 5 yi AL a H a T E E 6 Dy AE CH INS PETEA E AA T E EE IE AE A E A E E EA EIE E E E AE A 7 SA Sport Plati oree O E E E T O T 4 Inegtalling and getting started With Tol ang OMe ccsicicsscesnescscnsavesvnniestanetenesxannncoreneonstonsnntanntiatexensteantes 7 41 Downloading the Core Distibhutigns oss cesurss a cea puasices eeansiccqans veo sxvyald ana riain iienaa sanin ainia hakaina 8 ANET i EE E A A A A E A P E A E E A L A E E A RTE E 8 do The INU EO ANN Eei E a 9 ITLI T A E atin E E E E IE RA E PE EE ae 9 HS W Mch Releases 10 GE ooren a aE a NE 9 4 6 Where to report problems bugs of enhancements c csicsesecassacccsseasesaceansesasnsorscdeoasedarnasansdeneenaanace 9 5 Justa he Dirogol Prior a MINS ia OE E E E EESTE 10 2 1 The eit propra i Tolen exuien trarnnnt car reat ENE EEEE EAEE EES NETE ORE eter een eee 10 G Scnping Language pros And CONS os nccnsacis ners yvceudscaas ssenste peaa seennenceinan teense taste oateycuaienecialls 11 6 1 Some of the most common complaimts about Tel c sssececscscnssasevesaviaateeccanreesaxcanesseaarbessadeonavioastiaanee 11 Tol e imene ecnin a RE fi Several choracteristics ate nok MYG pai cncavp mar ren svecandi ii EEEa E NEE OORTE eat 11 G2 Same of ihe Mosi pro
3. Internet introductory papers white papers tutorials slides postscript versions of published books in draft and many more For a complete reference please give a look at the excellent Tcl FAQs 8 5 Newsgroup comp lang tcl is an unmoderated Usenet newsgroup created for the discussion of the Tcl programming language and tool s that use some form of Tcl such as the Tk toolkit for the X window system Extended Tcl and expect 8 2 Manual and On line Tutorials 15 The Linux Tcl and Tk HOWTO For Tcl Tk related announcements always refer to comp lang tcl announce you will find release announcement patches new application and so on Again faq could be retrieved at Tcl FAQs 9 Tcl Tk License Terms The following terms apply to the all versions of the core Tcl Tk releases the Tcl Tk browser plug in version 2 0 and TclBlend and Jacl version 1 0 Please note that the TclPro tools are under a different license agreement This agreement is part of the standard Tcl Tk distribution as the file named license terms TCL TK LICENSE TERMS This software is copyrighted by the Regents of the University of California Sun Microsystems Inc Scriptics Corporation and other parties The followin g terms apply to all files associated with the software unless explicitly discla imed in individual files The authors hereby grant permission to use copy modify distribute and license this software and its documentation for any purpose prov
4. You can execute your code directly without compiling and linking though Tcl compilers are available It is extensible It s easy to add your own commands to extend the Tcl language You can write your commands in C or Tcl It is embeddable in your applications The Tcl interpreter is merely a set of C functions that you can call from your code This means you can use Tcl as an application language much like a macro language for a spreadsheet application Tcl Tk is Year 2000 Y2K compliant Read what the creator of the Tcl and Tk core tells about this topic www scriptics com Y2K html 7 Most Famous Programs using Tcl Tk Apart from the two implementation described in the Introduction there are many applications writte n in Tcl Tk or a combination of Tcl and C A complete list where to look for these implementation is the part 4 of the frequently asked questions on Tcl Tk FAQs I suggest you to visit Scriptics Softwar e Central Another good starting point is www NeoSoft com tcl 6 2 Some of the most pros about Tcl 12 The Linux Tcl and Tk HOWTO One of the best Tcl applications running under Linux is called TkDesk a window manager and application launcher that works very well If you re a Tcl Tk Linux developer feel free to send me a URL and a description of the work that I can link to in here 8 References For many reasons people often like having a hard copy manual as a reference or like to be helped by oth
5. companies or commercial URL sites I really don t work for these guys 1 6 Credits Most of the information in this HOWTO comes from Dr Ousterhout s Scriptics and Larry W Virden comp lang tcl FAQs I would like to thank the PLUTO Italian Linux User Group and the whole volunteers of ILDP Italian Linux Document ation Project especially Eugenia Franzoni and Giovanni Bortolozzo for their feedbac k 1 4 Revision History 4 The Linux Tcl and Tk HOWTO 1 7 Distribution Policy This document is Copyright 1998 by Luca Rossetti This document is distributed in the hope that it will be useful to the reader of course it is considered to be without any warranty without even the implied warranty of merchantability or fitness for a particular purpose This HOWTO is free documentation you can redistribute it and or modify it under the terms of the LDP COPYRIGHT Please read the LDP Manifesto for more details 2 _Icl Tk History Tcl Tk originated with Dr John Ousterhout pronounced Oh stir howt while teaching at University of California Berkeley Califor nia He actually started implementing it when he got back to Berkeley in the spring of 1988 by summer of that year it was in use in some internal applications but there was no Tk Read about the history of Tcl Tk directly from its author s words at www scripti cs com scripting tclHistory html 2 1 Cronology e 1989 The first external releases of Tcl and beginning of Tk imp lementio
6. from the first edition it also covers sockets packag es namespaces a great section describing the changes in Tcl 7 4 7 5 7 6 and 8 0 and Tk as well Safe Tk and the Plugin Tcl and Tk Reference Manual Editors Donald Barnes Marc Ewing Erik Troan WWW book information www l sl com catalog bo oks tcltk The Visual TCL Handbook 1 e Author David Young WWW book information www amazon com exec obidos ISBN 013461674X u 7141 5908756 107481 A comprehensive guide to Visual TCL This book leads reader from basic graphical user interface development concepts to meaningful application develo pment The book focuses on the TCLX and VT extensions addressing many fundamental TCL topics VT is a Motif based graphical interface incompatible with Tk The entire TCL language is documented in a separate Commands section Comes with a CD ROM that includes SGI Solaris HP UX AIX and Unixware versions of Visual Tcl Running LINUX Author Matt Welsh and Lar Kaufman WWW book information www ora com ca talog runux2 noframes html Running Linux is a really well written basic book It has a chapter on programming using Tcl Tk and Perl C C Tcl Tk for Dummies For Dummies Author Timothy Webster with Alex Francis WWW book information www dummies com Another one of the series of the paperback programming books This one focuses on the Tcl plugin as a programming environment Interactive Web Applications With Tcl Tk Authors Mi
7. particular wants or needs One answer to What is Tcl can be found at www NeoSoft com tcl whatistcl html 3 2 What is Tk Tk pronounced tee kay is an extension to Tcl which provides the programmer with an interface to the X11 windowing system Note that Tk has been successf ully compiled under X11 R4 X11 R5 X11 R6 as well as Sun s NeWS X11 environments 3 2 What is Tk 6 The Linux Tcl and Tk HOWTO Many users will encounter Tcl Tk via the wish command Wish is a simple windowing shell which permits the user to write Tcl Tk applications in a proto typing environment At present Tcl Tk cannot handle Japanese Chinese Korean language fonts 3 3 Extensions Since Tcl is so easy to extend many try to share extensions including the popular itcl incr Tcl ObjectTcl TclX Tix and BLT These extensions of course require an extended Tcl interpreter Moreover many Tcl free applications require a particular Tcl extension to run One of the most popular extension is called Expect It allows you to place a friendly front end inside most command line based UNIX applications such as ftp telnet rlogin passwd fsck and so on A complete list of Tcl Tk extensions can be found at URL www scr iptics com resource software extensions 3 4 Supported Platforms This section contains information about Tcl 8 0 and Tk 8 0 the most recent version of Tcl Tk They were originally released on August 18 1997 and the most
8. recent patch releases 8 0 3 were made on September 3 1998 When you download Tcl and Tk you get two programs wish and tclsh supporting script libraries and on line reference documentation These programs are gene ral purpose platforms for writing applications with Tcl Wish includes the graphic al user interface toolkit Tk The packages are ready to use after installation Tcl 8 0 and Tk 8 0 run on most releases of the following operating systems e Windows 95 e Windows NT e Solaris and SunOS e Linux e HP UX e SGI e IRIX e Digital Unix e AIX e SCO Unix e Most other Unix like operating systems Macintosh 68K and Power Mac e Pre compiled releases are available for different Linux distribution 4 Installing and getting started with Tcl and Tk Most modern distribution include Tcl and Tk Rpm and deb packages with precompiled binaries are avalaible for Red Hat SuSE and Debian distributions that ll make installation easier 3 3 Extensions 7 The Linux Tcl and Tk HOWTO A modern distribution standard installation will include Tcl Tk as it is needed by many configuration tools running mainly under X Tcl and Tk are distributed freely in source form via the Internet There are no restrictions on their use and no licenses or royalties are needed see the license terms section for complete information Many more Tcl Tk scripts and extensions are also available freely 4 1 Downloading the Core Distributions The
9. Tcl Tk core consists of the Tcl and Tk libraries plus the wish and tclsh applications associated documentation script libraries and demonstrat ive applications The primary FTP site for this information is ftp scriptics com pub tcl The primary HTTP site is www scriptics com software download html 4 2 Installation Unless already available for your Distribution in proprietary packages you ll want to download the source release You ll need both Tcl and Tk source s This procedure refers to the second case Choose between compressed tar and gzipped tar format Compressed Tar Files Tcl sources tcl8 0 3 tar Z compressed tar file about 2 4 Mbytes Tk sources tk8 0 3 tar Z compressed tar file about 3 3 Mbytes Gzipped Tar Files Tcl sources tcl8 0 3 tar gz gzipped tar file about 1 5 Mbytes Tk sources tk8 0 3 tar gz gzip ed tar file about 2 1 Mbytes When you retrieve one of these files you will get a compressed tar file with a name like tcl8 0 3 tar gz or tcl8 0 3 tar Z The files are identical except for the technique used to compress them gz files are generally smalle r than Z files To unpack the distribution invoke shell commands like the following depending on which version of the release you retrieved gunzip c tcl8 0 3 tar gz or tar xf zcat tcl8 0 3 tar Z 4 1 Downloading the Core Distributions 8 The Linux Tcl and Tk HOWTO or tar xf unzip tcl80 3 zip Each of these commands wil
10. The Linux Tcl and Tk HOWTO The Linux Tcl and Tk HOWTO Table of Contents The Linux Tel and Tk HOWTO posicsccsssasscsacassorsttnsivvandacisannaissaenssaaneeaneaasniaaninracenies 1 Luca Rossett lukaros OUN tbs scaveniessenatssicasnyessaesressaceorsaaveinesscntersieceny eedeavquea OE EE E E ETES 1 DENT BEALL A A EA E ORA EN E EA AAN E E EENET E EE ATAA 1 ERTA U D a EEA a E E NEEE EEA E A AE see ERRORS EEE A 1 ee AT erie sl eepereneee eee mee ree ne tiers mene Sele Sere eR erReT ye Sehter Sean Tipe Tein Retin meter Scheme Tener terete ee 1 4 Installing and getting started with Teland Ve scocceesssccansteseseues enron R OES 1 SUSE ay ie One OF ELOLE T AAS A A A EE O OLE 2 6 Cra Unie Language pros and CONS ropena in A ER EAE AEA EN EATA 2 L Most Famous Prost aris uaine TONTE scscsis tcsspintccaciatctarietclaetaaicaiondea i tieuaaneccemaloanimnertaals 2 SFe eR CES a E S 2 AE ieee WSN eE npr sates eh eden oon wie web ok chen an Das lake Rema Ra TAE 2 RU EEEE ELEA E PARAE csc EA PETET RE EE EET PETA A E E E ETE SACE a EEEE E 2 1 l Purpose ol thie docume anr EE eee ae 3 1 2 What you should kiow betore PEAR ING sce sccctisccctsvecsdacuscecntte sors susvevecneuvensaniye deteassedapiesacupiereednseteadioes 3 LO Ney Versione of iis docum ira A Gao as 3 la BRT PAIGE iy pace ap pte vasa gupincen gets dank wes A pay Gas aud Good E A AA sneipauatas 4 Ps Pee ace on Cer S00 1 EE LA A A AA A E E EE T A EA L A TE E 4 LO e Ora N EE 4 TF TF ia Ok ADT i AAA E E I
11. chael Doyle Hattie Schroeder WWW book information www eolas com tcl This is a learning by example book for people who know a bit of programming but are not experts It covers developing applets as well as stand alone appli cations and simple server applications The book comes with the Spynergy toolkit whic h adds a variety of pure Tcl Tk procedures for distributed processing URL retri Tcl and Tk Reference Manual 14 The Linux Tcl and Tk HOWTO eval HTML rendering database management and platform independent file managment Ed a Tcl editor and testing environment an image conversion tool a demo of Tk features a client server version of a rolodex application a pure Tcl web server a client server push application a tcl web browser 8 2 Manual and On line Tutorials e John Ousterhout has written an engineering style guide that describes the coding documentation and testing conventions that will be used at Sun in the coding of the C code in the Tcl core and has made it available to other Tcl and Tk developers It is located at ftp script ics com pub tcl doc engManual tar Z e A second style guide covering the writing of Tcl scripts can be found at ftp scr iptics com pub tcl docs styleGuide tar gz Other versions of it can be found at sunscript su n com techcorner styleGuide ps e A brief introduction to TCL TK by David Martland e Another tutorial untitled User interfaces with Tcl T kwas written by Fintan Culwin e Although
12. ction is responsible for handling all the arguments AS a very standard example the following is the Hello World program in Tcl Tk This is a comment button b text Hello World command exit pack b 5 Just a little bit of Programming 10 The Linux Tcl and Tk HOWTO In this case you have to type the commands interactively to tclsh or wish You can also place command into script files and invoke these just like shell scripts To do this for the previous example rewrite the Hello World program as follows usr local bin wish f button b text Hello World command exit pack b Put the text inside a file called Hello and make sure that wish is installed in usr local bin otherwise you will have to change opportunely the path Make the file Hello executable issuing the command chmod 775 Hello and run it inside X You will see a button labelled Hello World inside a window clicking it will close exit the window 6 Scripting Language pros and cons To understand the importance and the future of Tcl Tk I strongly suggest to point your web browser at the URL www scriptics com people john ousterhout by John K Ousterhout You will read about the importance and the comparison between scripting in langua ges such as Tcl and system programming in languages such as C and Java To read a document about comparisons see the comparison discussion Here s a summary of the most important pros and cons about Tcl Tk
13. d several other new features Tk 8 0 is the first release to provide native look and feel on Macintoshes and PCs Tk 8 0 also supports application embedding and has a new portable font mechanism Both Tcl 8 0 and Tk 8 0 provide additional features in the Safe Tcl security model 4 6 Where to report problems bugs or enhancements Use _comp lang tcl for public communicati ons The alternative would be to send problems suggestions new ideas etc directly to the author Email to John Ousterhout will reach the author of Tcl and Tk When reporting problems or bugs be sure to mention all the details needed for a correct diagnosis Basically you will have to describe what hardware operating system and version of Tcl Tk you are using if you have 4 3 The Contributed Archive 9 The Linux Tcl and Tk HOWTO made any modification or add on and provide if possible either a small piece of code or a URL to some code which demonstrates the problem If you have software from which you think the community might benefit either a program function extension or simple example or you have a document magazine or journal article thesis project or even commercial advertisement be sure to let the appropriate guys know There are FAQ maintainers for each of these areas as well as a comp lang tcl announce newsgroup you can use It is always worthwhile to submit your contributions directly to the ftp site so more folk in the future can benefit
14. er folks online Here you can find a selection of reference books tutorials www sites and newsgroup 8 1 Books Many books concerning Tcl Tk were written and are to be published I won t even try to list them all another howto woudn t be enough for that You can find much more information plus additional notes at e www tcltk com consortium resources books html e www amazon com exec obidos subst categories computer programming tcl_tk article 002 8989352 45 1641 e Page tcl_books html at URL starbase neosoft tcl books Here I will try to summarize with some notes the book I know concerning the subject they re all at a basic medium level Again people who know the subject have enough information about where to find advanced level books Tcl and the Tk Toolkit Author John K Ousterhout WWW book information cseng aw com bookdetail qry ISBN 0 2D201 2D63337 2DX amp ptype 0 Book s examples ftp script ics com pub tcl doc book examples Z Book suppliment www scriptics com doc tk 4 0 ps The book primarily covers Tcl 7 3 and Tk 3 6 Practical Programming in Tcl and Tk Il ed Author Brent Welch WWW book information www beedub com book Book s table of contents www beedub com book Book promotion info at section_50000 html of the URL www borders com sections 8 References 13 The Linux Tcl and Tk HOWTO This updated edition describes Tcl Tk 8 0 as it was during the beta period Along with the material
15. ided that existing copyright notices are retained in all copies and that this notice is included verbatim in any distributions No written agreement license or royalty fee is required for any of the authorized uses Modifications to this software may be copyrighted by their authors and need not follow the licensing terms described here provided that the new terms are clearly indicated on the first page of each file where they apply IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE ITS DOCUMENTATION OR ANY DERIVATIVES THEREOF EVEN IF THE AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT THIS SOFTWARE IS PROVIDED ON AN AS IS BASIS AND THE AUTHORS AND DISTRIBUTORS HAVE NO OBLIGATION TO PROVIDE MAINTENANCE SUPPORT UPDATES ENHANCEMENTS OR MODIFICATIONS GOVERNMENT USE If you are acquiring this software on behalf of the U S government the Government shall have only Restricted Rights in the software and related documentation as defined in the Federal Acquisition Regulations FARs in Clause 52 227 19 c 2 If you are acquiring the software on behal f of the Department of Defense the software shall be classif
16. ied as Commercial Computer Software and the Government shall have only Restricted Rights as defined in Clause 252 227 7013 c 1 of DFARs Notwithstanding the foregoing the authors grant the U S Government and others acting in its behalf permissi on to use and distribute the software in accordance with the terms specified in this license 9 Tcl Tk License Terms 16
17. l create a directory named tcl8 0 3 which includes the sources for all platforms documentation and the script library for Tcl 8 0 To compile and install the distribution follow the instructions in the README file in the distribution directory Be sure to compile Tcl before Tk since Tk depends on information in Tcl 4 3 The Contributed Archive There are many other freely available packages for Tcl and Tk including both scripts written in Tcl and extensions written in C or C These packages include database applications and network access a graphical user interface builder the expect program additional Tk widgets and dozens of other things The primary site for the Tcl Tk archive is ftp neosoft com pub tcl 4 4 Mirror Sites Several other sites around the world mirror the whole or part of the material from the core site and the contributed archive you may find more useful to retrieve information from a mirror site that is close to you Ftp file O_mirror at ftp scriptics com pub tcl for a list of the mirror sites in your country 4 5 Which Releases to Use Always refer to newer recommended version in section Tcl Tk Core of the Scriptics Soft ware Central page At the time of this writing recommended releases are the latest Tcl 8 0 3 and Tk 8 0 3 which were released in September 1998 Tcl 8 0 contains a new bytecode compiler that can speed up execution by a factor of 2 10x It also provides namespaces binary I O an
18. lt with one of the C or C based toolkits Tk implements the Motif look and feel A great number of interesting X applications are implemented entirely in Tk with no new application specific commands at all 1 Intr ion e 1 1 Purpose of this document e 1 2 What you should know before readin e 1 3 New versions of this document e 1 4 Revision Histor e 1 5 Feedback and other stuff e 1 6 Credits e 1 7 Distribution Polic 2 Tcl Tk History e 2 1 Cronology 3 What is Tcl Tk e 3 1 What is Tcl e 3 2 What is Tk e 3 3 Extensions e 3 4 Supported Platforms 4 Installing an in r with Tcl and Tk e 4 1 Downloading the Core Distributions e 4 2 Installation e 4 3 The Contributed Archive e 4 4 Mirror Sites e 4 5 Which Releases to Use e 4 6 Where to report problems bugs or enhancements The Linux Tcl and Tk HOWTO 1 The Linux Tcl and Tk HOWTO 5 Just a little bit of Programming e 5 1 The one minute program in Tcl 6 Scripting Language pros and cons e 6 1 Some of the most common complaints about Tcl e 6 2 Some of the most pros about Tcl 7 Most Famous Programs using Tcl Tk 8 References e 8 1 Books e 8 2 Manual and On line Tutorials e 8 3 World Wide Web sites e 8 4 Other documents amp Frequently Asked Questions e 8 5 Newsgrou 9 Tcl Tk License Terms 1 Introduction This is the Linux Tcl and Tk HOWTO It is intended as a Linux reference covering everything you should know concerning installation c
19. n e 1991 First release of Tk e 1994 Dr Ousterhout was hired by Sun Microsystems Inc he was a Distinguished Engineer and led the Tcl project e April May 1997 the Sun research group responsible for Tcl devel opment were spun off into a Sun business group called SunScript However things chan ged again soon afterwards You can read more about that evolution selecting SunSc ript_story at URL Su nScript Story e August 1997 a Tcl Consortium was formed e February 1998 Dr Ousterhout left Sun to create Scriptics a company dedicated to scripting tools applications and services According to www scriptics com about news ga html core Tcl and Tk remain free with the team at Sun continuing work right now on Tcl Tk 8 1 After the next release the intention is that work on the core will migrate from Sun to Scriptics with the Sun team will focus more on Tcl extensions and applications e April 23 1998 the Association for Computing Machinery ACM awarded the 1997 Software System Award to John Ousterhout and Scriptics www acm org awards This award is given to an institution or individual recognized for developing a software system that has had a lasting influence reflected in contributions to concept s in commercial acceptance or both 3 What is Tcl Tk 3 1 What is Tcl Tcl is the acronym for Tool Command Language it is pronounced tickle Tcl is actually divided into two things a language and a library 1 7 Distrib
20. nttool front end is mainly a Tcl Tk script For those who don t know Red Hat let me tell you how you can easily configure your printers just filling some textboxes and filling in some checkboxes The program itself takes care of setting up printing services through the creation of spooling directory writes etc printcap file and the printer s filter reloads Ipd and tests your filter with ascii or postscript pages It allows you manipulate ghostscript options i e choose up to 8 pages per outpu t page and setting margins has an help on line and many more features What is the difference compared to other service printing implementation Everything is achieved by using Tcl Tk as a glue between consolidated application and operating with normal Linux configuration files in a visual and interactive window under X Window No new application specific commands were written at all 1 1 Purpose of this document Currently the purpose of the document is limited to giving initial references to Linux users in future versions I will try to incorporate a small Programm ing Tutorial Let me state that again this is not and doesn t want to substitute an omnicomprehensive user manual or reference for Tcl and Tk development and programming it s just a starting point for Linux users The author s concept of reference manual coincides with the definition of man pages and many people learn Tcl Tk from these basic source of informati
21. on These files are a part of the source code distribution and are installed on your Linux box You will be able to access the Tcl Tk manual pages through the man command Many structured and complete programming tutorials have been written in order to let the new user begin hacking with Tcl Tk tons of other material are available in the Internet Interpreting Tcl Tk philosophy I won t try to reinvent the wheel I will manage to glue the huge amount of material already available I suggest you to have a look at the other documents listed in the References section in order to find where to retri eve specific information about Tcl and Tk 1 2 What you should know before reading In order to understand the abc of Tcl Tk you shouldn t be a programming guru command sintax is very simple Basically you have to be familiar with e simple programming concepts e using very common unix commands and or utilities e having access to the Internet e using ftp 1 3 New versions of this document 1 1 Purpose of this document 3 The Linux Tcl and Tk HOWTO Newer versions of this document will be uploaded to ftp site ftp sunsite unc edu pub Linux HOWTO and will be available on all other mirrors Hypertext and other versions of this and other Linux HOWTOs are available mainly at sunsite unc edu LDP Ipd ht ml and _www linux howto com and on many other Mirror World Wide Web sites I will try to incorporate in my Web Page the most recen
22. onfiguration and an introduction to development under Tcl and Tk History and some pros and cons about Tcl and Tk under Linux are analized and references are given to many other sources of information on a variety of topics related to this simple but powerful scripting language If you ever rebuilt your Linux kernel inside X using the command make xconfig you surely managed to face the strenght of this simple but powerful scripting language After executing the first step of kernel rebuilding a script called kconfig tk is executed via wish the Tcl intepreter The Linux Kernel Configuration wind ow appears Instead of answering a series of questions this X based configuratio n utility allows you to use checkboxes to select which kernel options you want to enable The system stores your last configuration options so that every time you run it you need only to add or remove some checks and you don t need to reent er the whole set of option Moreover you can fill the whole or part of the list of kernel option the order you want After this simplified step you can rebuil d your kernel in the traditional way 5 Just a little bit of Programming 2 The Linux Tcl and Tk HOWTO There s actually another famous case Have you ever used printtool Printer Config Tool C Copyright 1994 by Red Hat Software author Michael Callahan If you installed a Red Hat distribution you happily managed to use it to set up printing services Well pri
23. s abont Tol sinice inaa ea EE EAR EE N RE 12 i ie a hiph tevel Scr isin Vanes nia a EE 12 TE TEA aE EN E AE AEAT EE AA A A A E A A EA AA EAA TEE E EE 12 Te Ais th NVR TAS a cs A A AE A E manne ened Ie nen eA aR 12 JADE e ey shires sts esr ah pee esa ig eden ca Adee A Lee TEA aR 12 TE We USI Bs A A A SEA A ENE E E A A EA de A E 12 Te is embeddable in your applications casceru eia AERA Ea 12 PE A tee yea i Ye Gi A A paneer aan nd GaN gaia Naan 12 The Linux Tcl and Tk HOWTO Table of Contents Interactive Web Applications With FOU Ue nsee aapi kii eiii kr 8 2 Mamial and On line PROT IANS errenneren eano E EE EE EE A TO E EOE EEEREN Sa Woild Wide Web BINS ideene retni nnt ERKE E RES KAE ANAA EE wae pha saad EE AE KARESATA ERENER EKAT EEAS EREE AEE The Linux Tcl and Tk HOWTO Luca Rossetti lukaros tin it v0 2 07 November 1998 This document describes the Linux approach to Tcl a scripting langua ge It is an easy to learn interpreted language that uses a typeless approach to achieve a higher level of programming and a rapid application development The Tk toolkit is a programming environment for creating graphical user interf aces GUI under X Window System Their capabilities include the possibility to extend and embed in other application rapid development and ease of use Toge ther Tcl and Tk provide many benefits both to application developer and user Tk ba sed interfaces tend to be much more customizable and dynamic than those bui
24. t html and sgml version of the document Most Linux CD ROM distributions include the HOWTOs often in a subdir of usr doc directory and you can also buy printed copies from several vendors Sometimes the HOWTOs available from CD ROM vendors ftp sites and in hardcopy format are out of date If the date on this HOWTO is more than six months in the past then a newer copy is probably available on the Internet If you make a translation of this document into another language drop me a line and I ll include a reference to it here 1 4 Revision History e Version 0 1 28 October 1998 first version e Version 0 2 07 November 1998 deep restyling and lifting 1 5 Feedback and other stuff I rely on you the reader to make this HOWTO useful If you have any suggestio ns corrections or comments please send them to me Luca Rossetti and I will try to put them in the next revision If any of the links mentioned in this document becomes unavailable or changes please notify me immediately so that I can update and or remove the link Iam willing to answer general questions about Tcl Tk and Linux as best as I can Before doing so please read all of the information in this HOWTO and send me detailed information about the problem If you publish this document on a CD ROM or in hardcopy form a complimentary copy would be really appreciated E mail me and I will send you back my postal address In many section I mention publishing
25. tandard syntax once users know Tcl they will be able to issue commands easily to any Tcl based application e Tcl succeeds to provides programmability All a Tcl application needs to do is to implement a few application specific low level commands Tcl provides many utility commands and a general programming interface for building up comp lex command procedures By using Tcl applications need not reimplement these feat ures e Extensions to Tcl such as the Tk toolkit provide mechanisms for communi cating between applications by sending Tcl commands back and forth The common Tcl language framework makes it easier for applications to communicate with one another It is important to note that Tcl was designed thinking that the programmer should actually use two or more languages when designing large software system s One for manipulating complex internal data structures or where performance is important and another such as Tcl for writing very small scripts that glue together the other pieces providing hooks for the user to extend For the Tcl script writer ease of learning ease of programming and ease of gluing are more important than performance or facilities for complex data structures and algorithms Tcl was designed to make it easy to drop into a lower language when you come across tasks that make more sense at a lower level In this way the basi c core functionality can remain small and one need only bring along pieces that one
26. thanks to your experience To make announcements to the comp lang tcl announce newsgroup send email with the details to tcl announce Also feel free to just point folk at your own ftp site or WWW site if you have one which can be used 5 Just a little bit of Programming Since Tcl is an interpreted language to run a Tcl program also called a script you normally pass the script file to the Tcl interpreter wish for example wish hello tcl You can also use wish in interactive mode and type in commands at the command line There s another standard Tcl interpreter tclsh which only understands the Tcl language Tclsh does not have any of the Tk user interface commands so you cannot create graphical programs in tclsh Some Tcl freeware applications extend the Tcl language by adding new commands written as C functions If such is the case you need to compile the applicati on instead of just passing its Tcl code to the wish interpreter This application program from a Tcl perspective is really a new version of the wish interpret er which the new C commands linked in Of course the application program may be a lot more than merely a Tcl interpreter Note you can also use Tcl s auto loading capability on systems that support it 5 1 The one minute program in Tcl Tcl has a simple structure Each line starts out with a command such as button and a number of arguments Each command is implemented as if it was a C function This fun
27. ution Policy 5 The Linux Tcl and Tk HOWTO Tcl is a simple textual programming language intended for issuing commands to interactive programs such as text editors debuggers and shells It has a simple syntax and it is also programmable Tcl users can write command procedures to provide more powerful commands than those given in the built in set Second Tcl is a library package embeddable in applications The Tcl library consists of a parser for the Tcl language routines to implement the Tcl built in commands and procedures which allow each application to extend Tcl with addit ional commands specific to that application The application program generates Tcl commands and passes them to the Tcl parser for execution Commands may be generated by reading characters from an input source or by associating command strings with elements of the application s user interfa ce such as menu entries buttons and other widgets When the Tcl library receive s commands it parses them into component fields and executes built in commands directly For commands implemented by the application Tcl calls back to the application to execute the commands In many cases commands will make recursive invocation s of the Tcl interpreter by passing in additional strings to execute in fact procedures and conditional looping commands all work in this way An applicat ion program can obtain many advantages by using Tcl for its command language e Tcl provides a s
28. you should have your Tcl Tk manual pages on your system here s another place where to look for TCL Manual Pa ges from TCL7 4 Tk Manual Pages from TK4 0 e The Tcl Tk Cookbook offe rs a lot of getting started information 8 3 World Wide Web sites There are a great number of WWW resources which provide additional information about many aspects of Tcl and its extensions e Refer to Tcl FAQs pa rt2 for a great number of pointers to Tcl Tk documentation and web sites e Point your web browser at Tcl Tk Information a site with many links to TcITk resources on the web Information Extensions Tools Training and Events e Point your Web browser at The Official Contributed Sources A rchive for the Tool Command Language Tcl and the Tk Toolkit hosted by NeoSoft Inc e For a discussion dealing with the pros and cons of the major scripting languages article in SunWorld by Cameron Laird e A web page that contains a variety of comparisons between Tcl Tk and othe r similar systems Most of them are taken from comp lang tcl the author would be happy to add any other important article that you folks want to send to him Comparison by Wayne Christopher e E J Friedman Hill s Tcl Tk Course this document is available only in PowerPoint source form and in low quality HTML form in HTML format all the figures and some of the text is missing 8 4 Other documents amp Frequently Asked Questions A lot of material is available on the
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