running sub process

[Marco B. <em...@be...>]

brief introduction to the new function POSIX:EXEC (bad name but that's
ok for now) - spawns sub process (fork/execve). takes 5 arguments:

  - name of file to run, a string.
  - list of arguments to pass, a list of strings.
  - whether to wait for sub process to terminate or not
  - file descritors to stream mapping. a list specifying which file
    descrptor (a number) to attach to which stream. the stream can be
    an already opened stream, or a list containg :DIRECTION,
    :BUFFERED, :ELEMENT-TYPE and :EXTERNAL-FORMAT keyword args with
    same semantics as OPEN.
  - enviroment to pass to sub process, a hash table with variable
    names as keys and values as strings. (once this works i'll add
    ability to specify enviroment as an alist, a plist, or an array of
    char arrays).

returns multiple values, the first is the sub process's return value
(or NIL if we didn't wait for it to terminate). the remaing values are
the streams specifed for the file desriptors. would it better to
return a single list containing these things instead?

it does not spawn a shell (unlike MAKE-PIPE-INPUT-STREAM and
MAKE-PIPE-OUTPUT-STREAM) , this because i don't see any advantages to
it and spawning /bin/bash (or /bin/tcsh) just so that the shell can
then fork and execve seems like a waste (if i've missed something tell
me).

currently it allows a lot of control over the subproc at the expense
of not being very user freindly, ie: the first argument is not
automatically set to the file's name, $PATH is not searched in the
case of non absolute file names. i plan on building a convenient
program calling/chaing macro on top of this function.

any thoughts/comments on the road i've taken so far?

however, i've got a problem (surprised? :)): currently the only
streams you can pass it (to attach to file descriptors) are streams
attached to files because only thoses streams have an associated
Handle. I want to be able to attach any stream, for example, attach a
string-output stream to standard out. my current idea is to just
read/write from/to the stream to/from the sub process, but i think
this has some major dead lock problems. any ideas?

i'm not offering a patch yet because a) i'd like to test some things a
bit more and b) finish some things which aren't working (like this
stream problem and setting up the sub proc's enviroment).

-- 
-Marco
Ring the bells that still can ring.
Forget your perfect offering.
There is a crack in everything.
That's how the light gets in.
     -Leonard Cohen