Pipe error codes off by a factor of 256

[Martin Pool]

Mitch Chapman wrote:
> 
> I assume you're talking about the value you get when you
> close the pipe.  The semantics for that value are the same as for the
> wait(2) system call.  The exit code for a process which exits
> of its own free will is stored in the top 8 bits of the 16-bit
> return code.
> 
> In other words, see the man page for wait(2).

And it can be useful to look at the low byte: IIRC it tells you whether
the program exited on a signal, which is often useful information.  For
example you might opt to terminate yourself immediately if the user
interrupted the program you called.

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