---
name: "scope"
section: "3itcl"
platform: "linux"
package: "itcl3-doc"
version: "3.4.4-3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/scope"
---

# scope(3itcl)

capture the namespace context for a variable

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```

## NAME

scope - capture the namespace context for a variable

## SYNOPSIS

**itcl::scope** *name*

```

```

## DESCRIPTION

Creates a scoped value for the specified *name*, which must be a variable name.  If the *name* is an instance variable, then the scope command returns a string of the following form:

```
@itcl object varName
```

This is recognized in any context as an instance variable belonging to *object*.  So with itcl3.0 and beyond, it is possible to use instance variables in conjunction with widgets.  For example, if you have an object with a private variable `x`, and you can use `x` in conjunction with the `-textvariable` option of an entry widget.  Before itcl3.0, only common variables could be used in this manner.

If the *name* is not an instance variable, then it must be a common variable or a global variable.  In that case, the scope command returns the fully qualified name of the variable, e.g., `::foo::bar::x`.

If the *name* is not recognized as a variable, the scope command returns an error.

Ordinary variable names refer to variables in the global namespace. A scoped value captures a variable name together with its namespace context in a way that allows it to be referenced properly later. It is needed, for example, to wrap up variable names when a Tk widget is used within a namespace:

```
namespace foo {
    private variable mode 1
    radiobutton .rb1 -text "Mode #1"         -variable [scope mode] -value 1
    pack .rb1
    radiobutton .rb2 -text "Mode #2"         -variable [scope mode] -value 2
    pack .rb2
}
```

Radiobuttons `.rb1` and `.rb2` interact via the variable "mode" contained in the namespace "foo".  The **scope** command guarantees this by returning the fully qualified variable name `::foo::mode`.

You should never use the `@itcl` syntax directly.  For example, it is a bad idea to write code like this:

```
set {@itcl ::fred x} 3
puts "value = ${@itcl ::fred x}"
```

Instead, you should always use the scope command to generate the variable name dynamically.  Then, you can pass that name to a widget or to any other bit of code in your program.

## KEYWORDS

code, namespace, variable