This is an application created by default by the core distribution. It is a simple shell interpreter, and is frequently used by developers writing tcl scripts.
A user of tclsh (or of wish, the interactive tcl shell with Tk automatically loaded), should be aware that there are a few differences between typing tcl statements to the shell in interactive mode and typing tcl commands into a file and then executing it.
interactive: unknown will automatically pass command to exec . command file: the coder must specify exec before any non-tcl commands
interactive: stdout appears to the screen when you type commands command file: the coder must specify puts to get the output from a command to display to the screen
Category Application, a part of the Tcl package.