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Tcl

automation embedded scripting testing and glue around native tools

English

Definition first

What Tcl means

Tcl is a programming language for writing exact instructions, often used for automation embedded scripting testing and glue around native tools. Start with one mental model: input goes through steps and becomes output.

Minimum run factsFile script.tclRun tclsh script.tclHabit Print each substituted value and keep quoting rules visible
Program

An ordered set of instructions. It reads input, follows rules, and produces output.

Value and variable

A value is data. A variable is the name you use to hold and reuse that data.

Function

A named piece of work. It takes input, does one job, and can return a result.

Runtime

Tcl shell is the place that actually runs code from script.tcl.

First readable code

Program output

entry point output syntax puts
puts 42
Output 42

Language lineage

Tcl family tree

See where Tcl comes from, which languages feel close, and what to learn next.

roots
shellLispC
currentTclCommand language family
familyCommand language family
best used for

embedded commands, automation, and older tool scripting

Zero base path

1Read one rule2Predict output3Type from memory4Run checklist5Repeat with one change

Question bank

Search before practice

Pick a stage or search across the open programming bank. Jump straight to the matching drill.

18 matching questions
Q 1ChoiceStage 1 definitions

Tcl practice 1

Tcl question 1. Choose the statement that matches printing a value.

Q 2ChoiceStage 1 definitions

Tcl practice 2

Tcl question 2. Choose the statement that matches naming a value.

Q 3ChoiceStage 1 definitions

Tcl practice 3

Tcl question 3. Choose the statement that matches reusable function.

Q 4ChoiceStage 1 definitions

Tcl practice 4

Tcl question 4. Choose the statement that matches basic collection.

Q 5ChoiceStage 1 definitions

Tcl practice 5

Tcl question 5. Choose the statement that matches printing a value.

Q 6ChoiceStage 1 definitions

Tcl practice 6

Tcl question 6. Choose the statement that matches naming a value.

Q 7ChoiceStage 1 definitions

Tcl practice 7

Tcl question 7. Choose the statement that matches reusable function.

Q 8ChoiceStage 1 definitions

Tcl practice 8

Tcl question 8. Choose the statement that matches basic collection.

Q 9ChoiceStage 1 definitions

Tcl practice 9

Tcl question 9. Choose the statement that matches printing a value.

Q 10ChoiceStage 1 definitions

Tcl practice 10

Tcl question 10. Choose the statement that matches naming a value.

Q 11ChoiceStage 1 definitions

Tcl practice 11

Tcl question 11. Choose the statement that matches reusable function.

Q 12ChoiceStage 1 definitions

Tcl practice 12

Tcl question 12. Choose the statement that matches basic collection.

Q 13ChoiceStage 1 definitions

Tcl practice 13

Tcl question 13. Choose the statement that matches printing a value.

Q 14ChoiceStage 1 definitions

Tcl practice 14

Tcl question 14. Choose the statement that matches naming a value.

Q 15ChoiceStage 1 definitions

Tcl practice 15

Tcl question 15. Choose the statement that matches reusable function.

Q 16ChoiceStage 1 definitions

Tcl practice 16

Tcl question 16. Choose the statement that matches basic collection.

Q 17ChoiceStage 1 definitions

Tcl practice 17

Tcl question 17. Choose the statement that matches printing a value.

Q 18ChoiceStage 1 definitions

Tcl practice 18

Tcl question 18. Choose the statement that matches naming a value.

Multiple choice

Tcl practice 1

Q 1Choicenew

Tcl question 1. Choose the statement that matches printing a value.

puts 42

Reference

Patterns for script.tcl

Tcl shelltclsh script.tcl
Recall from memoryRead a small point then write it back without looking
Trace the codeWrite variable values line by line before you run the answer
Type it yourselfCopy less type more and fix one small error at a time

entry point output syntax puts

Program output

puts 42
  • Run the smallest file first
  • Print one known value
  • Check the output before adding more code

variables assignment types set

Values and names

set total 42
puts $total
  • Give values readable names
  • Keep one idea per line while learning
  • Trace the value before changing it

function collection List

Functions and collections

proc add {a b} {
  return [expr {$a + $b}]
}

set scores {40 2}
puts [llength $scores]
  • Keep functions small
  • Return useful values
  • Use the common collection before reaching for frameworks