exitCode property
ExitCode is the PROGRAM's own status — 0 succeeded, anything else is what it returned, and a Command runs under sh -c so its shell's conventions apply. A command that never reached an exit does not arrive here at all: a timeout or a stop cancels the channel, and that is an error on the call rather than a code of ours invented to fill this field.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
int? exitCode;