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Practical Programming in Tcl & Tk, Third Edition by Brent B. Welch

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Interactive Conveniences

The unknown command provides a few other conveniences. These are used only when you are typing commands directly. They are disabled once execution enters a procedure or if the Tcl shell is not being used interactively. The convenience features are automatic execution of programs, command history, and command abbreviation. These options are tried, in order, if a command implementation cannot be loaded from a script library.

Auto Execute

The unknown procedure implements a second feature: automatic execution of external programs. This makes a Tcl shell behave more like other UNIX shells that are used to execute programs. The search for external programs is done using the standard PATH environment variable that is used by ...

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