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

[Kon Lovett]

On Mar 14, 2007, at 11:48 AM, Alex Queiroz wrote:

> Hallo,
>
> On 14 Mar 2007 15:38:46 -0300, Mario Domenech Goulart
> <address@hidden> wrote:
> > Is the return value one of the functionalities which depend on the
> > capabilities of the host shell?  Or the documentation should mention
> > that the return value of `system' corresponds to the exit status of
> > the process which was executed?
>
>     ANSI C does not guarantee that. You can't really say much about
> the return value of system.

I think ISO C90 says system should return -1 on error.

Anyway, Chicken 'system' procedure will return the errno value if the  
C 'system' call returns -1. Otherwise it depends:

*nix	WIFEXITED(n) ? WEXITSTATUS(n) : (WIFSIGNALED(n) ? WTERMSIG(n) :  
WSTOPSIG(n))
	Not sure how the C 'system' call return value of 127 (for shell  
failed to exec)
        is represented in the return value.

! *nix	C 'system' call return value. On Windows this is the value  
returned by the 	shell.

IMHO this means the return value is almost useless w/o some hoops;  
i.e. if 'errno' == the return value the return value is error value,  
but differentiating an exit-status from a signal-code is probably  
impossible.

Best Wishes,
Kon

> --
> -alex
> http://www.ventonegro.org/
>
>
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