Q50228: How to Use CALL INTERRUPTX to Get Name of Current Directory

Article: Q50228
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S891018-85 B_BasicCom | mspl13_basic
Last Modified: 12-DEC-1989

This article gives an explanation and code example for how CALL
INTERRUPTX can be used to get the name of the current directory on a
specified drive using Microsoft QuickBASIC.

This information applies to Microsoft QuickBASIC Versions 4.00, 4.00b,
4.50, to Microsoft BASIC Compiler Versions 6.00 and 6.00b, and to
Microsoft BASIC PDS Version 7.00.

MS-DOS interrupt 21 hex function 47 hex returns an ASCIIZ string that
describes the name of the current directory and the path from the root
to the current directory. An ASCIIZ string is a series of ASCII
characters terminated by a null byte. A null byte or null character is
a 1-byte data item (a char in C) that has the value zero. It is the
first character on any ASCII chart.

The "current directory" is the subdirectory that you are currently
working in. The MS-DOS CHDIR (CD) command is used to change the
current directory.

Note: It is necessary to use the CALL INTERRUPTX statement to call
this DOS function. This is not possible with the CALL INTERRUPT
statement. CALL INTERRUPT does not allow a program to change the value
of the DS or ES registers. CALL INTERRUPTX allows both DS and ES to be
set.

Code Example
------------

REM $INCLUDE: 'qb.bi'
' For BASIC PDS 7.00 and QBX.EXE the include file is 'QBX.BI'

DIM InRegs AS RegTypeX
DIM OutRegs AS RegTypeX
DIM CurrentDirectory AS STRING * 64

CurrentDirectory = STRING$(64, CHR$(32))   '32 is ASCII for SPACE
InRegs.Ax = &H4700                       'Function Number     in AH
InRegs.Si = VARPTR(CurrentDirectory)     'Offset of Variable  in SI
InRegs.Ds = VARSEG(CurrentDirectory)     'Segment of Variable in DS
InRegs.Dx=0                              'Drive Number        in DX
                                         '(0=default, 1=A, etc.)
CALL INTERRUPTX(&H21, InRegs, OutRegs)
CLS
PRINT "Current Directory = " + RTRIM$(CurrentDirectory)
END

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.