exitCode property Null safety

A Future which completes with the exit code of the process when the process completes.

The handling of exit codes is platform specific.

On Linux and OS X a normal exit code will be a positive value in the range [0..255]. If the process was terminated due to a signal the exit code will be a negative value in the range [-255..-1], where the absolute value of the exit code is the signal number. For example, if a process crashes due to a segmentation violation the exit code will be -11, as the signal SIGSEGV has the number 11.

On Windows a process can report any 32-bit value as an exit code. When returning the exit code this exit code is turned into a signed value. Some special values are used to report termination due to some system event. E.g. if a process crashes due to an access violation the 32-bit exit code is 0xc0000005, which will be returned as the negative number -1073741819. To get the original 32-bit value use (0x100000000 + exitCode) & 0xffffffff.

There is no guarantee that stdout and stderr have finished reporting the buffered output of the process when the returned future completes. To be sure that all output is captured, wait for the done event on the streams.