set

Read and write variables.

Syntax

set varName ?newValue?

Parameters

• varName: Name of the variable, optionally namespace-qualified (e.g., ::foo::bar)
• newValue: Optional new value to assign

Description

The set command reads and writes variables:

• With one argument: returns the current value of the variable
• With two arguments: sets the variable to the new value and returns it
• Creates a new variable if one does not already exist

Supported Features

• Namespace-qualified variable names: Variables can be accessed using namespace qualifiers like ::foo::bar. The resolution follows standard TCL namespace rules.
• Frame-local variables: For unqualified names, frame-local (procedure-local) storage is used.
• Variable traces: Both read and write traces are fired appropriately.
• Variable creation: Setting a non-existent variable creates it automatically.

Error Handling

• Wrong number of arguments: wrong # args: should be "set varName ?newValue?"
• Reading non-existent variable: can't read "varName": no such variable

Limitations

• Array element syntax: TCL's standard set arr(index) value syntax for arrays is not supported. A variable name like arr(foo) is treated as a literal scalar variable name rather than accessing element foo of array arr.

Examples

Setting and getting a variable

Output

Using set to read a variable

Output

Namespace-qualified names

Output

Variable creation

Output

See Also

• unset - Delete variables
• append - Append to variable
• incr - Increment integer variable
• global - Access global variables
• variable - Declare namespace variables
• upvar - Create variable links