man 3 exit

exit(n)                      Tcl Built-In Commands                     exit(n)

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NAME
       exit - End the application

SYNOPSIS
       exit ?returnCode?
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DESCRIPTION
       Terminate  the  process, returning returnCode to the system as the exit
       status.  If returnCode isn't specified then it defaults to 0.

KEYWORDS
       exit, process

Tcl                                                                    exit(n)