osx man page for 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 is not specified then it defaults to 0.

EXAMPLE
       Since non-zero exit codes are usually interpreted as error cases by the calling process, the exit command is an important part of signaling
       that something fatal has gone wrong. This code fragment is useful in scripts to act as a general problem trap:
	      proc main {} {
		  # ... put the real main code in here ...
	      }

	      if {[catch {main} msg options]} {
		  puts stderr "unexpected script error: $msg"
		  if {[info exist env(DEBUG)]} {
		      puts stderr "---- BEGIN TRACE ----"
		      puts stderr [dict get $options -errorinfo]
		      puts stderr "---- END TRACE ----"
		  }

		  # Reserve code 1 for "expected" error exits...
		  exit 2
	      }

SEE ALSO
       exec(n)

KEYWORDS
       exit, process

Tcl																	   exit(n)