[asdf-devel] asdf:run-shell-command - fix, delete or don't touch?

[Faré]

On Thu, Oct 6, 2011 at 23:14, Daniel Herring <dherring at tentpost.com> wrote:
> There are so many problems with "portable shell programming" that I don't
> think (b) [fix run-shell-command] can be done in general.
> [...]
> IMO, the right approach is to have a core CL library that gives direct
> access to the exec() family of functions on unix and the closest equivalent
> on other OSes (createprocess on MSWin).  Argument quoting for string
>
Well, this is *exactly* what asdf:run-shell-command or
xcvb-driver:run-program/process-output-stream is all about:
it's a wrapper around whatever functionality is provided
by the implementation, that basically allows you
to spawn a process in a portable way
(and, in XCVB, also to process the output of said command).

If a shell is ever involved, it's only because many implementations
do not provide any better access to subprocesses than system(3).

asdf:run-shell-command adopts a "least common denominator" approach,
where nothing can be portably run that has any kind of character in it
that any implementation may interpret specially, including any of
" $\\;^!`\"'(){}|<>?*&~". If you don't care for portability, you might
use the richer interface of whichever implementation you're using.

> (MSWin is a basket case in that each process implements its own
> command-line parsing however it pleases.  So auto-quote becomes a generic
> function dispatching on the target process...)
xcvb-driver:run-program/process-output-stream allows you to either
give a list of strings as a command, that gets quoted the "standard" way
or a string, where you control what quoting you use.

> Long story short, I wouldn't invest more in ASDF's command.  I would try to
> promote an execv-style wrapper as a de facto standard, possibly with an
> optional attempt at quoting for MSWin.
That's what xcvb-driver:run-program/process-output-stream does.
For a more powerful tool than this portable wrapper,
one could use iolib's portable reimplementation of run-program,
but it doesn't look like anyone's willing to implementing it for Windows,
and it comes with a lot of baggage (libfixposix, cffi, etc.)

> Once that is chosen (and probably
> polished a bit more), port the handful of systems using run-shell-command
> to this other library, and then step (c) [delete asdf:run-shell-command]
> is the logical conclusion. After step
> (c), ASDF could ship with a copy of this shell library, much as most distros
> include ASDF...
>
Yup.

—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org