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History

Originally developed as a reusable command and configuration language for CAD tools
Designed to be linked into programs easily
Born on 1988
Originally Written by John Ousterhout

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Simple to Learn

Good editor support, Vim and Emacs
Commands look like: Noun Verb Stuff
Helpful error messages
Magic is frowned upon
Great for a part-time programmer
Stable over time
Great community and resources online, start at http://wiki.tcl.tk
12 rules to understand syntax

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12 Rules of Tcl, man n Tcl

Commands
Evaluation
Words
Double Quotes
Argument Expansion
Braces

Command Substitution
Variable Substitution
Backslash Substitution
Comments
Order Substitution
Substitution of word boundries

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Hello World

What explanation would be complete with out hello world:

puts "hello world"

line terminator is '\n' , ';' is optional
puts appends '\n' by default, can be suppressed

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Interactive tclsh

commands not recognized by tcl will be passed through to the shell, can call man etc.

gandalf% tclsh8.5

% pwd

/home/marc

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Error Messages

It is quicker to generally invoke an error then to look it up
Its like Cisco IOS where it walks you through the command syntax

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Error as docs demo

Start with "the GRAND puBA stuff"
End with "The grand puba stuff"
Remember Noun Verb stuff , stuff may be optional
Using string command for example

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String example

% string ?

unknown or ambiguous subcommand "?": must be bytelength, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart

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String example pt 2

% string totitle

wrong # args: should be "string totitle string ?first? ?last?"

% string totitle "the GRAND puBA stuff"

The grand puba stuff

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Stable over time

Old TCL code generally works
TEA or "TCL Extension Architecture" means that old C code will generally work or work with minor tweaks
Stability is valued by the community
long term community, there has been a tcl conference for the past 18 years
integrated unit testing framework that tests the language and all tests ship with the code.

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Extensions

TCLLIB
TkCon
SNIT, pure tcl object system
expect
metakit, embeded nonsql db
sqlite
postgres
mysql

Tnm/scotty, snmp
tls
BLT

If you look you will probably find what you want

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Cisco

Tcl is embeded in your Cisco devices if they run IOS. There is a book on the subject "TcL Scripting for Cisco IOS", http://www.ciscopress.com/bookstore/product.asp?isbn=1587059452

Cisco CNR also uses tcl

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TclKit/StartKit

tclkit and startkits are used to create deploy-able binaries from tcl scripts.
they can embed compiled object code
works on unix, linux, macos and windows
the startkit can dynamically detect which os you are on and load the correct compiled code, with a few lines of code

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Start kit micro howto

make a dummy file, bobo.tcl and have it print "hello world"
run ./tclkit sdx.kit qwrap bobo.tcl , you now have a start kit
run ./tclkit bobo.kit , see "hello world" print its alive
run ./tclkit sdx.kit unwrap bobo.kit , you now have a properly laid out virtual file system
Hack and make app
run ./tclkit sdx.kit wrap bobo.kit
run your app

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start kit demo

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Where the pain is

Still no UDP in base, their are extensions though
no parse step, very dynamic language so it defies static analysis.
event loop can block
white space sensitive in a different way then most scripting languages.
you can override any command, this includes for loops and the like.

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Resources

http://wiki.tcl.tk
comp.lang.tcl
http://www.tcl.tk
IRC details here: http://wiki.tcl.tk/1178

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goodies in tcllib that I like

Highlight/sections:

programming tools

mathematics

data structures

text processing

networking

cgi programming

Specifics:

ldap/ldapx

smtp/mime

report/csv/struct::matrix

tcllib_ip

textutils

cmdline

pki

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