My favorite Tcl story is a little side note about how Tcl could have been the language of the web[1]
the founding of Netscape occurred at the same time I was deciding where to go in industry when I left Berkeley in 1994. Jim Clarke and Marc Andreessen approached me about the possibility of my joining Netscape as a founder, but I eventually decided against it (they hadn't yet decided to do Web stuff when I talked with them). This is one of the biggest "what if" moments of my career. If I had gone to Netscape, I think there's a good chance that Tcl would have become the browser language instead of JavaScript and the world would be a different place! However, in retrospect I'm not sure that Tcl would actually be a better language for the Web than JavaScript, so maybe the right thing happened.
Too humble Dr. Ousterhout! It would have been a far better language.
I was leading a Tcl project around then, and, though there were some very neat things about the unusual Tcl evaluation model, I wasn't a fan of using it for nontrival work. For example, it wasn't a natural fit for working with graph structures like I had to, and like you might want for browser DOM.
(That said, Tcl would've been much better than JS, and I suspect that Ousterhout would've figured out some smart things to make it good for the browser.)
Maybe 5 years later, I was meeting with Tim-Berners Lee, and I kinda pitched Scheme to him, without planning to, but he was very interested when he asked what I'd been working on.
But then he went and did a conference keynote, in which he promoted Python as the language for ordinary people doing Web stuff. And I think he referenced one of the things I'd written in support of Scheme... as an anti-requirement for his populist vision for the Web. :)
(I wish I could've been involved in that, because I could've made a case for a populist spin on Scheme at the time.)
TCL has an extremely loose runtime model, not to mention everything in the language is basically a string and all that entails.
I’ve been using JavaScript since the early 2000s, just before ES5 dropped.
Like all languages it has its curveballs but it really isn’t all that bad. It simply has oddities due to the quirky nature of the niche it was designed to fill (namely, to be a scripting language that was forgiving to web designers)
Honestly? I think the biggest cause of JavaScript hate is that a huge percentage of developers have very little choice but to use it.
The web ate almost everything else for a host of reasons, and JavaScript is still the only language that the web natively supports. You can compile to JS or use WASM with occasional callouts to JS, but you can't get away from it entirely.
Most other languages have a greater sense of choice surrounding them. For backend work you can pick pretty much anything, and mobile is still a small enough chunk of the ecosystem that if you really hate Swift you can just find a job that isn't iOS dev. It's not so easy to get out of web dev without dramatically shrinking your job pool.
All I can say is that’s the cost of doing business with the browser being the main platform.
If devs want to interact with it less then focus on moving more to the server. You can still serve HTML and CSS and get a long way without ever touching JS.
It’s no different than other domains where one or two particular languages largely dominate. Like I don’t hear developers decrying the existence of C/C++ every chance they get
I think the hate is entirely unjustified. It’s fine to have preferences but so often it goes beyond that.
I think Tcl as it was back then especially would have been a terrible DOM manipulation choice. I love the language but the hacks frameworks like openacs used to use to imitate basic stuff like a list of database records are among the ugliest upvar/up level hacks I've seen.
But that being said it's an incredibly adaptable language and I have zero doubt it could have been adapted to make DOM manipulation ergonomic.
Funny that Tcl was mentioned today. I've recently been hacking on jimtcl[1] (a small footprint implementation of Tcl) to make objects multi-threaded safe, as that's the core language that folk.computer[2] uses (the main authors are making the interpreter and reactive DB parallelizable rn, so I've been tinkering with how to reduce copying).
Surprised no mentions of sqlite yet :) I've always associated Tcl with sqlite because of how much it is used in their test suite and how you can have a tcl interpreter as a virtual table. Very interesting and seemingly often overlooked little language.
> Some content has been removed in the second edition of the book because of limits on the number of pages
Lol, wut? The literal only working "buy it now" link is to a PDF. Page limits my ass. Or maybe "Paperback: 660 pages" was dangerously close to the Devil himself springing forth from the pages and turning all your codebase into VBScript
but I'm not seeing an easy binary download --- used to be that the availability of a pre-compiled version, nicely packaged which would install easily on one's platform of choice made it wonderfully accessible to new users.
I was going to say releases are published to Sorceforge[0] but indeed those look to be all src too. That said: I’d be surprised to find a distro that doesn’t have Tcl available in whatever package manager(s) they support.
I have known about Tcl since the 1990s. I remember Stallman advising not use it. Maybe he did not like the license?
Yesterday, over 30 years later I was forced to write my first code. Noticed that a Cisco switch had an incredibly bad ssh implemtation, so to automate some commands I needed expect scripting. Expect is based on Tcl.
"a language for extensions should... be a real programming
language, designed for writing and maintaining substantial programs...
The first Emacs used a string-processing language, TECO, which was
inadequate. We made it serve, but it kept getting in our way. It
made maintenance harder, and it made extensions harder to write...
Tcl was not designed to be a serious programming language. It was
designed to be a "scripting language", on the assumption that a
"scripting language" need not try to be a real programming language.
So Tcl doesn't have the capabilities of one. It lacks arrays; it
lacks structures from which you can make linked lists. It fakes
having numbers, which works, but has to be slow. Tcl is ok for
writing small programs, but when you push it beyond that, it becomes
insufficient.
Tcl has a peculiar syntax that appeals to hackers because of its
simplicity. But Tcl syntax seems strange to most users."
If I recall correctly, I think he was just more of a lisp fan and promoted something like Guile or E-Lisp. It may have been license as well. I'm not very sure about it though.
I think he was worried about Sun Microsystems involvement[0] w Tcl when John Ousterhout went there[1], too. But mostly seems like a collection of unsolicited strawmen[2]. Also probably love-of-lisp.
I own the first edition of this book and it's really good. I've written a few tcl scripts with it, but nothing major. Python just has the better ecosystem now for my needs. I might use tcl if I needed something really small though.
It is still actively developed and used, yeah. People tend to mention the fpga scene most, tcl is the predominant language there, but I use it mostly with or along side audio/visual software.
I would be interested to know if anyone ever built anything non-trivial that didn't turn into a complete mess due to TCL's general type-flimsyness and "everything is a string" philosophy.
The GUI of Pure Data (https://en.m.wikipedia.org/wiki/Pure_Data) is written in Tcl/Tk. In the 90s this was a popular and sensible choice, but not so much in 2025 :) I still have hopes that one day we'll manage to replace it with something better.
(There are alternative implementations of Pd, such as PurrData or PlugData, that use different UI frameworks.)
> I would be interested to know if anyone ever built anything non-trivial that didn't turn into a complete mess due to TCL's general type-flimsyness and "everything is a string" philosophy.
Both MacPorts CLI client[0] and ports tree[0] have used it successfully for many years.
Regarding:
"everything is a string" philosophy
That can be said for the vast majority of Unix-like OS user-space programs.
TCL/tk is used for the vast majority of integrated circuit verification tools. This is used by all the large manufacturers, even competitors use each others tools.
Absolutely huge codebases, there's git blames that go back to the 80s.
Someone did a nice job of porting your revision control data. It would be fascinating to know what the previous systems were - probably svn or cvs, maybe both in chronological order, but before that?
For FPGA IDEs, a lot of the background is just tcl scripts so you can easily write your own build scripts. You could theoretically put them into your CI pipeline but I don't know if anyone actually does this.
I know in the late 90s, early 2000s they were Vignette shop, back when it was a Tcl application. Can only imagine their relief getting to carry over their tcl knowledge while no longer having to suffer with Vignette. I don't think I've ever heard anyone that actually liked Vignette.
There is no big difference between TCL and other languages like Python in this respect. Yes, TCL stores everything as a string, but it also assigns a type when the data is used. If you need a defined type, you can use structures; there are even classes/objects available as packages.
Yep! It's called shimmering. The way it works is it has a string and internal representation. When the internal representation is modified it invalidates the string version. If the string version is needed later it'll regenerate the string representation. That way it can always be used as a string, but internally it is pretty efficient when it stays as the same type.
You’re misunderstanding. Dynamic languages inherently have a single type that is checked _at runtime_. Store it in a string, store it in a struct. It doesn’t matter.
And in Tcl the runtime type is computed at time of use. An optimized Tcl could cache an integer with a string that represents an int to avoid that cost.
Nevertheless, a runtime type tag is an optimization. That doesn’t make Bob’s statement any less true.
TCL stands for "tool command language." In terms of non trivial tools that have been built with it there have been several. AOLServer, MacPorts, tons of CAD and engineering software. There's a whole wikipedia category just for this:
Aside from that there was Tk which was used to create many UIs in an era where scripted UIs were otherwise painful to create and maintain. A prominent example here is 'xconfig' from the linux kernel.
Like any good environment a little bit of practice with it can see you overcome it's apparent shortcomings and see you producing reliable and useful software in far less time that you might have in a more traditional way.
Programming is about trade offs. It's not a checklist of "good ideas."
My big project at work uses pytk only because it was already included with the anaconda distribution. It works fine, it's not pretty but it's just an internal engineering tool.
My favorite Tcl story is a little side note about how Tcl could have been the language of the web[1]
Too humble Dr. Ousterhout! It would have been a far better language.1 - https://pldb.io/blog/JohnOusterhout.html
I was leading a Tcl project around then, and, though there were some very neat things about the unusual Tcl evaluation model, I wasn't a fan of using it for nontrival work. For example, it wasn't a natural fit for working with graph structures like I had to, and like you might want for browser DOM.
(That said, Tcl would've been much better than JS, and I suspect that Ousterhout would've figured out some smart things to make it good for the browser.)
Maybe 5 years later, I was meeting with Tim-Berners Lee, and I kinda pitched Scheme to him, without planning to, but he was very interested when he asked what I'd been working on.
But then he went and did a conference keynote, in which he promoted Python as the language for ordinary people doing Web stuff. And I think he referenced one of the things I'd written in support of Scheme... as an anti-requirement for his populist vision for the Web. :)
(I wish I could've been involved in that, because I could've made a case for a populist spin on Scheme at the time.)
Why does JavaScript get some much hate?
TCL has an extremely loose runtime model, not to mention everything in the language is basically a string and all that entails.
I’ve been using JavaScript since the early 2000s, just before ES5 dropped.
Like all languages it has its curveballs but it really isn’t all that bad. It simply has oddities due to the quirky nature of the niche it was designed to fill (namely, to be a scripting language that was forgiving to web designers)
"Brooklyn Nine-Nine" said it: https://www.youtube.com/watch?v=H1-GDlzODzc&t=27s
Honestly? I think the biggest cause of JavaScript hate is that a huge percentage of developers have very little choice but to use it.
The web ate almost everything else for a host of reasons, and JavaScript is still the only language that the web natively supports. You can compile to JS or use WASM with occasional callouts to JS, but you can't get away from it entirely.
Most other languages have a greater sense of choice surrounding them. For backend work you can pick pretty much anything, and mobile is still a small enough chunk of the ecosystem that if you really hate Swift you can just find a job that isn't iOS dev. It's not so easy to get out of web dev without dramatically shrinking your job pool.
All I can say is that’s the cost of doing business with the browser being the main platform.
If devs want to interact with it less then focus on moving more to the server. You can still serve HTML and CSS and get a long way without ever touching JS.
It’s no different than other domains where one or two particular languages largely dominate. Like I don’t hear developers decrying the existence of C/C++ every chance they get
I think the hate is entirely unjustified. It’s fine to have preferences but so often it goes beyond that.
I think Tcl as it was back then especially would have been a terrible DOM manipulation choice. I love the language but the hacks frameworks like openacs used to use to imitate basic stuff like a list of database records are among the ugliest upvar/up level hacks I've seen.
But that being said it's an incredibly adaptable language and I have zero doubt it could have been adapted to make DOM manipulation ergonomic.
If I remember correctly early HTML specs actually used Tcl as an example for script tag content.
It was definitely possible that Tcl could have ended up the web sripting language.
In that world, Netscape might have also acquired Naviserver instead of AOL. Wasn't the plan at Netscape to make money on their server software?
Funny that Tcl was mentioned today. I've recently been hacking on jimtcl[1] (a small footprint implementation of Tcl) to make objects multi-threaded safe, as that's the core language that folk.computer[2] uses (the main authors are making the interpreter and reactive DB parallelizable rn, so I've been tinkering with how to reduce copying).
[1] https://github.com/msteveb/jimtcl [2] https://folk.computer/
Surprised no mentions of sqlite yet :) I've always associated Tcl with sqlite because of how much it is used in their test suite and how you can have a tcl interpreter as a virtual table. Very interesting and seemingly often overlooked little language.
> Some content has been removed in the second edition of the book because of limits on the number of pages
Lol, wut? The literal only working "buy it now" link is to a PDF. Page limits my ass. Or maybe "Paperback: 660 pages" was dangerously close to the Devil himself springing forth from the pages and turning all your codebase into VBScript
There is a source release at:
https://www.tcl-lang.com/software/tcltk/9.0.html
but I'm not seeing an easy binary download --- used to be that the availability of a pre-compiled version, nicely packaged which would install easily on one's platform of choice made it wonderfully accessible to new users.
Is that not a focus of the project these days?
I was going to say releases are published to Sorceforge[0] but indeed those look to be all src too. That said: I’d be surprised to find a distro that doesn’t have Tcl available in whatever package manager(s) they support.
[0] https://sourceforge.net/projects/tcl/
Looks like binary downloads are on another page and not necessarily made by tcl-lang
https://www.tcl-lang.com/software/tcltk/bindist.html
From that page:
- Android 8.6.10 https://androwish.org/download/index.html
- Activestate seems to require account creation: https://www.activestate.com/pricing/
- Windows, nightly build of 9.0.2 from 15 February: https://gitlab.com/teclabat/tcltk/-/packages/34837768
- Windows 8.6.7 https://www.irontcl.com/index.html
This looks like the link I was looking for: Windows 9.0.1: https://www.tcl3d.org/bawt/download.html#tclpure which links to: https://www.tcl3d.org/bawt/download/Tcl-BI/SetupTcl-BI-9.0.1...
I have known about Tcl since the 1990s. I remember Stallman advising not use it. Maybe he did not like the license?
Yesterday, over 30 years later I was forced to write my first code. Noticed that a Cisco switch had an incredibly bad ssh implemtation, so to automate some commands I needed expect scripting. Expect is based on Tcl.
Per http://vanderburg.org/old_pages/Tcl/war/0000.html
Stallman's argument at the time was:
"a language for extensions should... be a real programming language, designed for writing and maintaining substantial programs...
The first Emacs used a string-processing language, TECO, which was inadequate. We made it serve, but it kept getting in our way. It made maintenance harder, and it made extensions harder to write...
Tcl was not designed to be a serious programming language. It was designed to be a "scripting language", on the assumption that a "scripting language" need not try to be a real programming language. So Tcl doesn't have the capabilities of one. It lacks arrays; it lacks structures from which you can make linked lists. It fakes having numbers, which works, but has to be slow. Tcl is ok for writing small programs, but when you push it beyond that, it becomes insufficient.
Tcl has a peculiar syntax that appeals to hackers because of its simplicity. But Tcl syntax seems strange to most users."
Most IOS implementations (classic, XE, XR) also have tclsh, a tcl REPL (that can also interact with the file systems to load and write scripts).
If I recall correctly, I think he was just more of a lisp fan and promoted something like Guile or E-Lisp. It may have been license as well. I'm not very sure about it though.
I think he was worried about Sun Microsystems involvement[0] w Tcl when John Ousterhout went there[1], too. But mostly seems like a collection of unsolicited strawmen[2]. Also probably love-of-lisp.
[0] That any proximity to commerce is evil?
[1] https://en.wikipedia.org/wiki/John_Ousterhout
[2] https://vanderburg.org/old_pages/Tcl/war/
I own the first edition of this book and it's really good. I've written a few tcl scripts with it, but nothing major. Python just has the better ecosystem now for my needs. I might use tcl if I needed something really small though.
A TCL interpreter is packaged with Python in the tkinter library:
import tkinter
tcl=tkinter.Tcl()
tcl.eval('puts "Hello, world!"')
Is Tcl still a thing? At my first job I extended with a set of data-processing commands.
It is still actively developed and used, yeah. People tend to mention the fpga scene most, tcl is the predominant language there, but I use it mostly with or along side audio/visual software.
I had this book, it's well written.
> this immensely flexible and versatile language
I would be interested to know if anyone ever built anything non-trivial that didn't turn into a complete mess due to TCL's general type-flimsyness and "everything is a string" philosophy.
Cisco iOS[0], F5 iRules[1], Tealeaf network monitoring/processing[2][3], Fidessa[4][5], …
[0] https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ios_tcl/co...
[1] https://community.f5.com/kb/technicalarticles/irules-concept...
[2] https://www.acoustic.com/tealeaf
[3] https://help.goacoustic.com/hc/en-us/articles/360043279654-C...
[4] https://www.cmegroup.com/solutions/market-tech-and-data-serv...
[5] http://www.services.fidessa.com/brochures/_training/VF043.pd...
The GUI of Pure Data (https://en.m.wikipedia.org/wiki/Pure_Data) is written in Tcl/Tk. In the 90s this was a popular and sensible choice, but not so much in 2025 :) I still have hopes that one day we'll manage to replace it with something better.
(There are alternative implementations of Pd, such as PurrData or PlugData, that use different UI frameworks.)
git-gui and gitk are also written in Tcl/Tk.
> In the 90s this was a popular and sensible choice, but not so much in 2025 :)
Infuriatingly, Tcl/Tk (and other things which use Tk) is still light years easier for doing basic GUI programming than anything that exists in 2025.
How the hell can decades have elapsed and Tcl/Tk, Hypercard and VB6 are still vastly better for GUI development than anything we currently have?
Flightaware, at one point, had a lot of Tcl code
https://www.flightaware.com/about/code/
>> this immensely flexible and versatile language
> I would be interested to know if anyone ever built anything non-trivial that didn't turn into a complete mess due to TCL's general type-flimsyness and "everything is a string" philosophy.
Both MacPorts CLI client[0] and ports tree[0] have used it successfully for many years.
Regarding:
That can be said for the vast majority of Unix-like OS user-space programs.0 - https://github.com/macports/macports-base
1 - https://github.com/macports/macports-ports
Wavesurfer was a great program written Tcl/Tk, with an audio processing library called "snack" in C with Tcl wrappers.
https://en.wikipedia.org/wiki/WaveSurfer
TCL/tk is used for the vast majority of integrated circuit verification tools. This is used by all the large manufacturers, even competitors use each others tools.
Absolutely huge codebases, there's git blames that go back to the 80s.
Someone did a nice job of porting your revision control data. It would be fascinating to know what the previous systems were - probably svn or cvs, maybe both in chronological order, but before that?
For FPGA IDEs, a lot of the background is just tcl scripts so you can easily write your own build scripts. You could theoretically put them into your CI pipeline but I don't know if anyone actually does this.
Sqlite started as a tcl extension. That isn't exactly your question, but I thought it was closely related.
And, AIUI, the monstrous test suite of SQLite is all in Tcl (which totally jives given your fact; they're obviously fans)
A lot of old GUIs are built on Tcl/Tk, lots of people use matplotlib which I think uses it by default.
For many years every web page at CNN and all web email at AOL was hosted by AOLserver and coded in TCL. It was not a mess.
I know in the late 90s, early 2000s they were Vignette shop, back when it was a Tcl application. Can only imagine their relief getting to carry over their tcl knowledge while no longer having to suffer with Vignette. I don't think I've ever heard anyone that actually liked Vignette.
There is no big difference between TCL and other languages like Python in this respect. Yes, TCL stores everything as a string, but it also assigns a type when the data is used. If you need a defined type, you can use structures; there are even classes/objects available as packages.
Does it still do this? I thought they changed this many years ago?
Yep! It's called shimmering. The way it works is it has a string and internal representation. When the internal representation is modified it invalidates the string version. If the string version is needed later it'll regenerate the string representation. That way it can always be used as a string, but internally it is pretty efficient when it stays as the same type.
That is absolutely not how Python works. Python values are typed.
> "a dynamically typed language is a statically typed language with only one static type."
Yes but we are not talking about static types...
You’re misunderstanding. Dynamic languages inherently have a single type that is checked _at runtime_. Store it in a string, store it in a struct. It doesn’t matter.
What you said above is correct but is not related to what was being discussed before.
The runtime values have tags that denote their runtime type. They are not of a single type. You are talking about static types.
And in Tcl the runtime type is computed at time of use. An optimized Tcl could cache an integer with a string that represents an int to avoid that cost.
Nevertheless, a runtime type tag is an optimization. That doesn’t make Bob’s statement any less true.
TCL stands for "tool command language." In terms of non trivial tools that have been built with it there have been several. AOLServer, MacPorts, tons of CAD and engineering software. There's a whole wikipedia category just for this:
https://en.wikipedia.org/wiki/Category:Free_software_program...
Aside from that there was Tk which was used to create many UIs in an era where scripted UIs were otherwise painful to create and maintain. A prominent example here is 'xconfig' from the linux kernel.
Like any good environment a little bit of practice with it can see you overcome it's apparent shortcomings and see you producing reliable and useful software in far less time that you might have in a more traditional way.
Programming is about trade offs. It's not a checklist of "good ideas."
It's Tcl now not TCL. No longer an acronym. It hasn't been TCL for years.
My big project at work uses pytk only because it was already included with the anaconda distribution. It works fine, it's not pretty but it's just an internal engineering tool.
what is your definition of non trivial?