[Openmcl-devel] Using OpenMCL as a shell scripting interpreter

[Gary Byers]

On Mon, 29 Mar 2004, Gary Byers wrote:

>
> If you change the first line to refer to the executable and save that
> in a text file called "showversion", as in:
>
> #!/usr/local/src/ccl/dppccl -V
>
> the executable will be invoked as
>
> argv[0] = "dppccl" (not "/usr/local/src/ccl/dppccl")
> argv[1] = "-V"
> argv[2] = "showversion"
>
> dppccl expects (naively) to have been invoked with its own full pathname,
> and uses that to find the default image name.
>
> To get that to work, I think that we'd have to
>
> (a)  use some other technique to find the executable's own pathname
>     and derive the default image name from it.
>
> (b) change the command-line parsing so that the script name has some
>     meaning.  (Currently, a random file name - not preceded by "--load"
>     or "--eval"  or something - isn't interpreted sensibly.)
>
> You could almost get (b) to work by doing something like
>
> #!/usr/local/src/ccl/dppccl --load
>
> though of course loading such a file would complain that the reader
> macro #! is undefined.  (I suppose that you could make #! behave as
> ; does.)
>
> As far as (a) goes: I know how to do this under Linux; on Darwin, I
> can't think of a way to do this without doing what "ps" does, which
> many involve the use of things that Apple considers "unstable".  I may
> be forgetting something obvious; does anyone know of a "stable" way to
> obtain the full pathname of the current process's executable under
> Darwin ?
>

The function _NSGetExecutablePath was introduced in Jaguar; it returns
the pathname of the current executable file (which may not be the same
thing as argv[0]).  In Linux, /proc/exe/self is a symbolic link to the
current executable.