Practical Programming in Tcl & Tk, Third Edition

The global Command

Global scope is the toplevel scope. This scope is outside of any procedure. Variables defined at the global scope must be made accessible to the commands inside a procedure by using the global command. The syntax for global is:

						global varName1 varName2 ...

The global command goes inside a procedure.

The global command adds a global variable to the current scope. A common mistake is to have a single global command and expect that to apply to all procedures. However, a global command in the global scope has no effect. Instead, you must put a global command in all procedures that access the global variable. The variable can ...