Re: Using Shell

 BBS: Inland Empire Archive
Date: 04-19-92 (11:37)             Number: 86
From: MIKE AVERY                   Refer#: NONE
  To: DAVID POSKIE                  Recvd: NO  
Subj: Re: Using Shell                Conf: (2) Quik_Bas

 DP> How about using:
 DP>  SHELL "if exist FILENAME.EXT echo y>temp.$"
 DP> That should work in all versions, past, present, and future. Yeah,
 DP> I just agreed that an ASM FileExist is the way to go. But old
 DP> ideas die hard. ;)

Under DOS, the redirection will ALWAYS be executed.  Sometimes the file
will be a zero length file, sometimes it will have a "Y" in it, but it
will always be created.  This may not be what you want.

In an issue of BASIC-PRO I have around here, but can't find, our own Dave
Cleary suggested the following....

DEFINT A-Z
DECLARE FUNCTION DIR$ (FileSpec$)
' $INCLUDE: 'QB.BI'                   'used by call interrupt

' Some constants that Dir$ users

CONST DOS = &H21
CONST SetDTA = &H1A00
CONST FindFirst = &H4E00, FindNext = &H4F00

IF LEN(DIR$("c:\usr\qb45\source\dir$.bas")) THEN
   PRINT "File Found!!"
ELSE
   PRINT "File Not Found!!"
END IF
PRINT DIR$("c:\usr\qb45\source\dir$.bas")
STOP

FUNCTION DIR$ (FileSpec$) STATIC
DIM DTA AS STRING * 44, Regs AS RegType
Null$ = CHR$(0)

'-- Set up a local Disk Transfer Area (DTA)

Regs.AX = SetDTA                   'Set DTA function
Regs.DX = VARPTR(DTA)              'DX points to locat DTA
INTERRUPT DOS, Regs, Regs          'Call the interrupt

'-- See if this is FindFirst or FindNext request
IF LEN(FileSpec$) THEN             'find first
   FileSpecZ$ = FileSpec$ + Null$  'make ASCIIZ for DOS
   Regs.AX = FindFirst             'Find First file
   Regs.CX = 0                     'match normal files
   Regs.DX = SADD(FileSpecZ$)      'DX points to spec
ELSE                               'it's a null string
   Regs.AX = FindNext              'so find next name
END IF

INTERRUPT DOS, Regs, Regs          'Call the interrupt

'-- return file name or null
IF Regs.flags AND 1 THEN           'No files found
   DIR$ = ""                       'so return null string
ELSE
   Null = INSTR(31, DTA, Null$)   'get the file name
   DIR$ = MID$(DTA, 31, Null - 30) 'strip the trailing chr$(0)
END IF

END FUNCTION

It looks pretty nice, and gives you access to file information without
shelling.  As to the "Never shell" argument, I'll stand aside and watch
the fireworks, as it is an area of interest where I have not formed
opinion at this time....

Thanks for the code Dave,
Mike

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