Exceptions mapping sysexits.h.

They are likely to be caught by void run(), for example:

 "The ultimate exception handler."
 suppressWarnings("expressionTypeNothing")
 shared void run() {
     try {
         main();
     } catch (ConfigurationError e) {
         process.writeErrorLine(e.message);
         process.exit(e.exit_code);
     }
 }

Exceptions mapping sysexits.h are named with postfix Error, and extends Exception.

You can extends them to represent more concrete exceptions. For example, this module also provides NotImplementedException, which is defined as

 shared class NotImplementedException(String message)
         extends InternalSoftwareError(message) {}

You can implement your own exception with customize exit_code, which extends abstract class SystexitsException. For example:

 "When following redirects, hit the maximum amount."
 shared class TooManyRedirects(String message) extends SysexitsException(message) {
     "The exit code is borrowed from curl."
     shared actual Integer exit_code 47;
 }