See the Tk::Entry documentation. In particular, the -validate, -validatecommand and -invalidcommand options (in WIDGET-SPECIFIC OPTIONS) and the entire VALIDATION section.

Also see the "Validated entries and password fields." examples in the Widget Demo.

— Ken

In reply to Re: Stopping bad input (harder than sanitizing) by kcott
in thread Stopping bad input (harder than sanitizing) by Anonymous Monk

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