OpenEuphoria

Re: File handling

• Posted by Irv <irv at ELLIJAY.COM> Jun 07, 1998
• 691 views

At 08:05 AM 6/7/98 -0400, you wrote:

>At 06:44 AM 6/7/98 -0500, Terry Constant wrote:
>
>>Its been so long since I worked with Command.com, I can't remember if
>>there is a way to get exit code info on internal commands. If not there
>>would only be one atom.
>>
>There must be a way. Batch files can branch based on errorlevel.
>Also there is interrupt 4Dh that reads the errorlevel returned
>on a program exit (I think. Anybody want to wade thru the dos-ref
>and find out for sure?)
>
>>In any case, the return sequence would have information about success or
>>failure that could be analyzed.
>>
>Someone made a suggestion to Rob that system() be made a function,
>rather than a procedure, for exactly that purpose. I hope he
>sees fit to change it.
>
I tried the interrupt routine below, but it doesn't work.
Why? My guess is because the errorlevel code is destroyed
by the first call to errorlevel.
Perhaps system() is using (therefore destroying) it before
returning?  Only Rob can tell us.
On the other hand, maybe something is wrong with my interrupt
routine. I don't know much about writing these.

include machine.e
sequence reg_list -- list of register values

function ErrorLevel()
reg_list = repeat(0, 10)
reg_list[REG_AX] = #4D00  -- function: get ERRORLEVEL

reg_list = dos_interrupt(#21, reg_list) -- Call DOS interrupt #21
return reg_list
end function

? ErrorLevel()
system("del test.xxx",2)
? ErrorLevel()  -- prints same as above, regardless of whether
                -- the system call fails or succeeds.

Irv
ref:Programmer's Technical Reference for MSDOS and the IBM PC
    Chap.4

Function  4Dh   Get Return Code of a Subprocess              (WAIT)
                Get return from functions 31h and 4Dh  (ERRORLEVEL)
entry   AH      4Dh
return  AH      circumstance which caused termination
                00h     normal termination
                01h     control-break or control-C
                02h     critical device error
                03h     terminate and stay resident (function 31h)
        AL      exit code of subprogram (functions 31h or 4Ch)
note 1) The exit code is only returned once (the first time).
     2) This call is explicitly supported in the OS/2 1.x DOS
        Compatibility Box.
     3) Many programmers have wondered where DOS stores this
        information, so they might access it multiple times or set it
        directly.  This is a version-dependent area that changes with
        every release of DOS.