exit - Man Page

exit ?returnCode?

Terminate the process, returning returnCode to the system as the exit status. If returnCode is not specified then it defaults to 0.

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 exists 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
}

exec(n)

abort, exit, process