This little function (below) calls upon a little known DOS call (&H60).
When passed a filespec, it expands the spec to a complete drive - path
- filename. If the spec has any illegal characters in it, DOS sends
back an error code of 2 (normally this means "file not found"). That
could be useful.
However, if the spec names a non-existant file or path, this function
won't flag it. If the spec uses a reserved DOS name, it sometimes
confuses this function, also. That's not so useful. Play with it. If
you can think of a good use for it, use it.
   -----------------------------------------------------------------
$LIB ALL OFF
DECLARE FUNCTION ValidSpec% (InSpec$, ErrCode%)
DO
  LINE INPUT "Enter a file spec: " ; Spec$
  IF LEN(Spec$) = 0 THEN EXIT LOOP
  Valid% = ValidSpec%(Spec$, ErrCode%)
  PRINT "Spec$ after call to DOS:  "; Spec$
  PRINT
  IF ErrCode% THEN PRINT "Error reported: "; ErrCode%
  IF Valid% THEN
     PRINT "Valid spec!"
  ELSE
     PRINT "NOT valid spec..."
  END IF
  PRINT
LOOP
END
'=============================================
 FUNCTION ValidSpec% (Spec$, ErrCode%)  PUBLIC
'=============================================
' When passed a file spec, this function determines if it contains
' all valid characters. If valid, it returns -1 and an errcode of zero.
' If invalid it returns a zero and the error code returned by DOS.
' This function expands specs that contain wildcard characters (?*),
' and filespecs that begin with a ".\" or "..\".
  DIM ErrorCode AS LOCAL INTEGER
  DIM Success AS LOCAL INTEGER
  ErrorCode = 0     'assume success
  Success = -1
  DIM InStringSeg AS LOCAL WORD
  DIM InStringOff AS LOCAL WORD
  DIM OutStringSeg AS LOCAL WORD
  DIM OutStringOff AS LOCAL WORD
  DIM OutString AS LOCAL STRING * 70
  IF LEN(Spec$) THEN
     InSpec$ = Spec$ + CHR$(0)         ' make an ASCIIZ from input spec
     InStringSeg = STRSEG(InSpec$)
     InStringOff = STRPTR(InSpec$)
     OutStringSeg = VARSEG(OutString)
     OutStringOff = VARPTR(OutString)
     ASM  Push DS
     ASM  Push SI
     ASM  Push DI
     ASM  Mov AX, &H6000
     ASM  Mov ES, OutStringSeg
     ASM  Mov DI, OutStringOff
     ASM  Mov SI, InStringOff
     ASM  Mov DS, InStringSeg
     ASM  Int &H21
     ASM  Jc  WasError
     ASM  Xor AX, AX
WasError:
     ASM  Mov ErrorCode, AX
     ASM  Pop DI
     ASM  Pop SI
     ASM  Pop DS
     IF ErrorCode THEN
       Success = 0        ' error code = invalid file name(?)
     ELSE                 ' retrieve expanded file spec into OutSpec$
       Spec$ = MID$(OutString, 1, INSTR(OutString, CHR$(0)) - 1)
     END IF
  ELSE
    ErrorCode = 2         ' treat null spec as "file not found
    Success = 0           ' not a valid spec
  END IF
  ErrCode% = ErrorCode
  ValidSpec% = Success
END FUNCTION
 * SLMR 2.1a * MAXLIB For PB v1.1 - Access arrays and files in EMS/XMS!
--- WILDMAIL!/WC v4.12 
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