Re: [Chicken-users] Return value of `system'

[Zbigniew]

I appreciate your insight, but please, please do not cripple (system)
any further by making the return value a boolean--it reduces its
utility immensely.  'process' is not always a good substitute [and has
the same signal/exit code conflation issue].  And 'osprocess' is just
far too heavy for what should be a simple call to system().

I can live with (system) returning either an exit code or a signal;
the value may be overloaded but it is still a good debugging aid.
Though I still feel a true system should just return the raw value, if
I did need the raw value I would just pull out and modify the code
from Chicken.

To answer Mario's question, the result returned from system() is
either the exit status or the signal number on any modern UNIX
machine; this is the same  as described in process-wait.  It also
returns 127 upon shell execution failure (I tested this) and 'errno'
upon waitpid or fork failure [again, cannot distinguish this from
signal or non-zero exit code].

This is well-defined and useful information, so I think that the
current return value behavior for UNIX should at least be documented.

On 3/14/07, Kon Lovett <address@hidden> wrote:
> For the library unit 'system' return value:
>
> 1) Store the return & exit status for the last call & provide
> accessors, as you suggested. Return the C 'system' call return value.
>
> 2) Multi-valued result, a'la 'process-wait'.
>
> 3) Return boolean value.
>
> I kinda prefer #3. If the user needs more, use a more complicated
> interface. The posix unit 'process' & 'process*' already have a shell-
> command mode.