The Linux Tcl and Tk HOWTO
Contents
1. it s just a starting point for Linux users 1 Introduction 3 The Linux Tcl and Tk HOWTO 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 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 simple programming concepts using very common unix commands and or utilities having access to the Internet using ftp 1 3 New versions of this document 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 av2. 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 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 It runs on many platforms 14 The Linux Tcl and Tk HOWTO to in here NextPreviousContentsNextPreviousContents 8 References For many reasons people often like having a hard copy manual as a reference or like to be helped by other 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 conm exec obidos subst categories computer programming tcl tk article 002 8989352 451641 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
3. Debian distributions that ll make installation easier 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 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
4. 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 classified 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 Next PreviousContents 8 4 Other documents amp Frequently Asked Questions 19
5. 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 8 References 15 The Linux Tcl and Tk HOWTO 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 This updated edition describes Tcl Tk 8 0 as it was during the beta period Along with the material 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 ISBNz013461674X 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 V
6. 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 Tcl provides a standard syntax once users know Tcl they will be able to issue commands easily to any Tcl based application 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 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 togeth
7. 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 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 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 Next Previous ContentsNextPreviousContents 1 4 Revision History 5 The Linux Tcl and Tk HOWTO 2 Tcl 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 1
8. web server a client server push application a tcl web browser 8 2 Manual and On line Tutorials 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 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 A brief introduction to TCL TK by David Martland Another tutorial untitled User interfaces with Tcl T kwas written by Fintan Culwin e Although 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 Point your web browser at Tcl Tk Information a site with many links to TcITk resources on the web Tcl Tk for Dummies For Dummies 17 The Linux Tcl and Tk HOWTO Information Extensions Tools Traini
9. 988 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 lemention 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 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 August 1997 a Tcl Consortium was formed You can read more abou t it including how to join who currently serves on the board of directors and so on by visi ting Tcl Consortium 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 April 23 1998 the Association for Computing Machinery ACM awarded the 1997 Software System Award to John Ousterhout a
10. AN Fe 1 oau E ESSE ERST 6 E OOE s t 6 AJ ONDES VOD EE Leu oodd md Ee CUM PU RE REN a TT eee 6 BU a We ES T T EE ERR T 6 EB OMEN TU cT 7 CERA Ee TOTIS 8 do DOO PISCTOEDB cans murals E UGERRRUG ER ERREUR aan aa URN ERGMOD RORY Ree E EA Ud RU a NEMORE 8 4 Installing and petting started with Tel nd TE oscense ieni Elo td pb ee e dieti et dias 9 4 1 Downloading the Core Distributions s poioce rrr IPS A Pr rr R dd Eee QE BH Po a na i i i MO EH TA Eb ru ar 9 S NPMESIDHUPIISMI vad pose esas TEE NE 9 S Ino Gira es STE US uoc ose Coo Ee CUM be DUBIE NR E RAE E BE GR Ub bte CUR E OR 10 CCS TUS ll NTC DT NR DEUM c TE 10 43 t bolegses OH SS e ian pio E o d D AE d fen pU icem bm ida tes mp TEA 10 4 6 Where to r port problems bugs arenlialic emet eoe repro eter oio po EXER FER ER NEP 11 2 Justa Dr ES EO SEVERE cc ost ce zone i tme fida Pee trea tet Po dis Un et Ux ee eR ut t had 1 2 1 The one minute progran TEL auk coner td ri sxe coepsnaynepanas seenpeceavaasy ce ba EMO ans tes hid Fee TRE 12 G pe Tata ni Language DEOS SD CONS sirieni aer iee RERO SOS PER E PIRE UM SEE UH ra PE TR FE CL PR ii 13 6 1 Some of the most common complaimis about Tel eerte tle etr Fert rv ex ied 13 Tol yo Ma DESEE oisi rape Cop ou abd RR LE URP ean ee igen E 13 Several characteristics are NOt IDCUItIVe uiiie ees serrer ner ret eee E ERE RUE ERAKRKREREREREKERE ERE FERE MEE NN ESETE 13 5 2 S006 01 the most pros SDOUL TOIT ia
11. T 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 Practical Programming in Tcl and Tk II ed 16 The Linux Tcl and Tk HOWTO 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 Michael 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 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
12. The Linux Tcl and Tk HOWTO The Linux Tcl and Tk HOWTO Table of Contents The Limur Toland Tk HOWTO P 1 Lica Rossett DUESEOSQUUTE A scs cona addant sad banshee bre oa erac vied ER Ko D EET ENTREE ER D FRE OR RE t iR 1 Ua EEN sca oti cay ecco Vee Rr TET PE TREES 1 FARE o d HH m E 1 CON CM NEA eT D uU LE UE 1 d Installing and sott started with Teland TE ou og p Feci Ri tale Use eee 2 S Justa itie ot Probrarmimmid usos saad er bis gang dadeeng a A pei ee PR IIR RA SR PER Vel HERDS 2 cert Laois DIOS and BON apc airo de Paseo Ut pb iva dup aio d E ad E pr tM i dipss 2 ZNlost Famous Programs using UCU oicccsssecsesssasececieserans ror narr asair Sar E LOOTE RE ENE 2 OR Ds E er EE AE N ua mt wg pant E on ced Caden EW male emt Ad eT peered or RANA OEE P 2 SIENTE Ricbuse Torie cna DEAN KEEU MUERE ERN ER ee RIT Fee ase ee 2 PRMD Ae fot Rcs Cei c M bein cna GRE eee 3 l l Purpose of this QOQGUUBEDE scorre Fer or gere ave ped MERE rr POPE EE xp bx HR cS PN VER MES enr N 3 1 2 What Ol should note Delois CODO oe a dir UE Cobb RR EEEN AEREE ROOM Or Ub etie RATES 4 1 3 New versions Of this document a eror rrt re PER EE HEFTE NCLPRRS Kr sain Kel habe ni E Kg DUC Rl sunk ses iN Esai EEs iar 4 MES ICIJDOIO UII A D OO E areas 5 L3 Feedback and oiher etili TTE P 5 DELS AANA NE AE asin viet wan EEE A NOE EI AA AE E A sels 5 BEBE EP A E L E RETE TETTE E E NA OE T OEE AON S 5 F
13. ailable 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 recent 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 2 What you should know before reading 4 The Linux Tcl and Tk HOWTO 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 I am 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
14. 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 function 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 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 Wor
15. ce you will find release announcement patches new application and so on Again faq could be retrieved at TcI FA Os NextPreviousContents Next PreviousContents 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 TcIPro 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 8 4 Other documents amp Frequently Asked Questions 18 The Linux Tcl and Tk HOWTO 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 provided 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
16. efits both to application developer and user Tk ba sed interfaces tend to be much more customizable and dynamic than those built 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 Introduction e 1 1 Purpose of this document e 1 2 What you should know before readin e 1 3 New versions of this document 1 4 Revision Histor e 1 5 Feedback and other stuff 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 The Linux Tcl and Tk HOWTO 1 The Linux Tcl and Tk HOWTO 4 Installing and getting started with Tcl and Tk 4 1 Downloading the Core Distributions e 4 2 Installation e 4 3 The Contributed Archive 4 4 Mirror Sites e 4 5 Which Releases to Use 4 6 Where to report problems bugs or enhancements 5 Just a little bit of Programming e 5 1 The one minute program in Tcl 6 Scripting Language pros and cons 6 1 Some of the most common complaints about Tcl 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 8 4 Other documents amp Frequently Asked Questions e 8 5 Newsgrou 9 Tcl Tk License Terms Next Previo
17. er 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 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 Many users will encounter Tcl Tk via the wish command Wish is a simple windowing shell which permits 3 2 What is Tk 7 The Linux Tcl and Tk HOWTO 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 mo
18. 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 4 Installing and getting started with Tcl and Tk 9 The Linux Tcl and Tk HOWTO 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 zat tOL840 3 tar 4 Or tar xf unzip tc180 3 zip Each of these commands will 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
19. i o aa diserti eb x aa Pese diei e Rd pr MEE tdeo EE 13 Hisa bish level scriptig ongutiif amp inem ette Re PEPR serin or TONE RETE AE 13 KESELR NN TU 13 ILE THU RESO SEPARATE TOTO dacs pio ana eT Np TTE 14 ICE TS ELE oS SUE oo 14 HE federe I T T T T Ue 14 t3s eimbeddabls th volur asp UOS e cae one RR p UR EE E RR Ob b Ree Ge 14 The Linux Tcl and Tk HOWTO Table of Contents T Most Famous Programs tsi VOU UK ccisiecsscsioscecascstcarssiedeasenesaansaciveciace O E E ENNE NE Be PRM BN cok sc ssn oro CITROEN Be UGB e P ve M M Interactive Web Applications With TOWING oe sinc ues orm trt o Rr X RR pr DEREN REP en XR PEEL URS SiE 8 2 Manual and On line Tutorials sssssceccccssscssssssseecoecceecussvsssvescosccsssacscnsvsssessssseesussvsssvsesosscass Ge UENIUNT UR NE CE 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 ben
20. ld inside a window clicking it will close exit the window NextPreviousContentsNextPreviousContents 5 1 The one minute program in Tcl 12 The Linux Tcl and Tk HOWTO 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 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 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 complexit
21. nd 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 NextPreviousContentsNextPreviousContents 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 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 2 Tcl Tk History 6 The Linux Tcl and Tk HOWTO 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
22. ng and Events Have a look at Tcl Consortium a non profit organization which promotes Tcl Tk and supports the development community 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 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 EJ 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 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 For Tcl Tk related announcements always refer to comp lang tcl announ
23. rinttool 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 printtool 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
24. roblem 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 benefitthanks 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 NextPreviousContentsNextPreviousContents 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 4 6 Where to report problems bugs or enhancements 11 The Linux Tcl and Tk HOWTO Some Tcl freeware applications extend the Tcl language by adding new commands written
25. st 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 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 Digital Unix e AIX e SCO Unix Most other Unix like operating systems Macintosh 68K and Power Mac Pre compiled releases are available for different Linux distribution NextPreviousContentsNextPreviousContents 3 3 Extensions The Linux Tcl and Tk HOWTO 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
26. to you Ftp file 0 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 and several other new features 4 3 The Contributed Archive 10 The Linux Tcl and Tk HOWTO 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 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 p
27. us Contents Next Previous Contents 4 Installing and getting started with Tcl and Tk The Linux Tcl and Tk HOWTO 1 Introduction This is the Linux Tcl and Tk HOWTO It is intended as a Linux reference covering everything you should know concerning installation configuration 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 There s actually another famous case Have you ever used p
28. y 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 ga html 6 Scripting Language pros and cons 13 The Linux Tcl and Tk HOWTO 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 interpreted 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 NextPreviousContentsNextPreviousContents 7 Most Famous Programs using Tcl Tk Apart from the two implementation described in the Introduction there are many applications writte n in
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