[Coco] error trapping

[Willard Goosey]

On Tue, Dec 01, 2009 at 01:58:31AM -0800, Wayne Campbell wrote:

> I need to know how to trap an error generated by the makdir command
> when it's being executed with a SHELL statement in a Basic09
> subroutine. 

SHELL "makdir foo >> /nil" should work, as long as nil and VRN are in
the kernel.  (All REAL operating systems have a null device! :-)

Otherwise, you can do some magic to check to see if the dir exists
first...

Here is my attempt at that magic, based on the C system call access()
But it has not been extensively tested.  (In particular I'm not sure
name will get the full size if passed
"/dd/extra/long/path/thats/longer/than/basic09/default/string/length"
)  On the other hand, it's not a fatal error if the file can't be
opened.


PROCEDURE access
PARAM name:STRING; perm:BYTE; result:BOOLEAN
(* access checks to see if file <name> can be opened with
(* permissions <perm> and returns the result in <result>
(*requires syscall
(*Willard Goosey

TYPE registers=cc,a,b,dp:BYTE; x,y,u:INTEGER
DIM path:BYTE
DIM regs:registers
DIM callcode:BYTE
DIM newname:STRING[100]

(*make sure filename ends in <cr>
newname:=name+CHR$($0D)

(*clear random garbage from regs struct
regs.cc:=0
regs.b:=0

(* PRINT "before syscall"; regs.cc

(* open #path,name:perm
(* can't actually do that :-(
(* open refuses to let its perms be in a variable.

callcode:=$84
regs.a:=perm
regs.x:=ADDR(newname)
RUN syscall(callcode,regs)
path:=regs.a

IF regs.b=0 THEN 
   result:=TRUE

   (* CLOSE #path
   (* have to do this the hard way too
   callcode:=$8F
   regs.a:=path
   RUN syscall(callcode,regs)
ELSE 
   result:=FALSE
   (*PRINT "regs.cc was"; regs.cc
   (*PRINT "regs.b was "; regs.b
ENDIF 
END 


Willard
-- 
Willard Goosey  goosey at sdc.org
Socorro, New Mexico, USA
I search my heart and find Cimmeria, land of Darkness and the Night.
  -- R.E. Howard