FILE HANDLING

 BBS: Inland Empire Archive
Date: 02-11-93 (18:29)             Number: 352
From: JOHN GALLAS                  Refer#: NONE
  To: OWEN GIBBINS                  Recvd: NO  
Subj: FILE HANDLING                  Conf: (2) Quik_Bas

OG>Are there any functions in QuickBASIC similar to the EXIST and NOT EXIST
OG>functions in batch files?

Yes!  Try the following...

'=========================================================================
'DIR.BAS by Dave Cleary
'
'One of the most useful additions to BASIC 7 PDS is the DIR$ function.
'This function allows you to read a directory of filenames. It also
'allows you to check the existence of a file by doing the following:
'
'  IF LEN(DIR$("COMMAND.COM")) THEN
'     PRINT "File Found"
'  ELSE
'     PRINT "File not found"
'  END IF
'
'Now QuickBASIC 4.X users can have this useful function for their
'programs.
'
'Calling DIR$ with a FileSpec$ returns the the name of the FIRST
'matching file name. Subsequent calls with a null FileSpec$ return the
'NEXT matching file name. If a null string is returned, then no more
'matching files were found. FileSpec$ can contain both a drive and a
'path plus DOS wildcards. Special care should be taken when using
'this on floppy drives because there is no check to see if the drive
'is ready.
'========================================================================
     DEFINT A-Z

     DECLARE FUNCTION DIR$ (FileSpec$)

     '$INCLUDE: 'QB.BI'

     '-----  Some constants that DIR$ uses
     CONST DOS = &H21
     CONST SetDTA = &H1A00, FindFirst = &H4E00, FindNext = &H4F00

     '
--
     'This shows how to call DIR$ to find all matching files

     'CLS
     'FileSpec$ = "C:\QB\SOURCE\*.BAS"
     'Found$ = DIR$(FileSpec$)
     'DO WHILE LEN(Found$)
     '   PRINT Found$
     '   Found$ = DIR$("")
     'LOOP

     '
--

 FUNCTION DIR$ (FileSpec$) STATIC

        DIM DTA AS STRING * 44, Regs AS RegTypeX
        Null$ = CHR$(0)

     '-----  Set up our own DTA so we don't destroy COMMAND$
        Regs.AX = SetDTA                    'Set DTA function
        Regs.DX = VARPTR(DTA)               'DS:DX points to our DTA
        Regs.DS = -1                        'Use current value for DS
        InterruptX DOS, Regs, Regs          'Do the interrupt

     '-----  Check to see if this is First or Next
        IF LEN(FileSpec$) THEN              'FileSpec$ isn't null, so
                                            'FindFirst
           FileSpecZ$ = FileSpec$ + Null$   'Make FileSpec$ into an ASCIIZ
                                            'string
           Regs.AX = FindFirst              'Perform a FindFirst
           Regs.CX = 0                      'Only look for normal files
           Regs.DX = SADD(FileSpecZ$)       'DS:DX points to ASCIIZ file
           Regs.DS = -1                     'Use current DS
        ELSE                                'We have a null FileSpec$,
           Regs.AX = FindNext               'so FindNext
        END IF

        InterruptX DOS, Regs, Regs          'Do the interrupt

     '-----  Return file name or null
        IF Regs.Flags AND 1 THEN            'No files found
           DIR$ = ""                        'Return null string
        ELSE
           Null = INSTR(31, DTA, Null$)     'Get the filename found
           DIR$ = MID$(DTA, 31, Null - 30)  'It's an ASCIIZ string starting
        END IF                              'at offset 30 of the DTA

 END FUNCTION

 * OLX 2.1 TD * He's not dead, Jim, he's metaphysically challenged.

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