'==========================================================================
' PROGPATH.BAS
' Keith Funk (CIS 72240,2020) Feb. 17,1991
' Vancouver, BC, Canada
'
' Demonstrates the use of the FUNCTION GetProgPath to find the drive and
' directory where the EXE file for this program is located.
'
' NOTE: The program must be compiled into an EXE file to work. Also,
' the program will NOT work with DOS versions earlier than 3.x.
'==========================================================================

DECLARE FUNCTION GetProgPath$ ()

' ===>>> uncomment one of the next two lines. ALSO, see line 26 of the
' GetProgPath$ FUNCTION.

'' $INCLUDE: 'QBX.BI' Basic 7 PDS
'' $INCLUDE: 'QB.BI' QuickBasic

PRINT "The EXE for this program is in "; GetProgPath$

'some demo,eh.

END

'===========================================================================
' FUNCTION GetProgPath - Finds and returns the drive and directory path
' where the EXE file of the calling program is located. Very useful if the
' program wants to open a file in its own directory (like a config file).
' The path is in the form: C:\George\Burns\. Note that the path always ends
' with a backslash.
'
' To use this routine, the calling program must contain the following line
' at the BEGINNING of the program. ' $INCLUDE: 'QB.BI' to include the
' QuickBasic file QB.BI that contains the stuff needed to use the routine
' CALL INTERRUPT. The /L option must be used when starting QB to load the
' QB Quick Library.
'
' THIS ROUTINE ONLY WORKS WITH DOS 3.x.
'
' The routine DOES NOT WORK when the program is run from within the Quick-
' Basic environment. The program MUST be compiled to an .EXE file. See below
' how to run the program within the QB development environment.
'
' Keith Funk (CIS 72240,2020) Feb. 17, 1991
' Vancouver, BC, Canada
'===========================================================================
'
FUNCTION GetProgPath$

'NOTE NOTE NOTE:
'when testing the program within the QB environment, hardwire the program
'path like this. Comment out these lines BEFORE compiling to an EXE file.

GetProgPath$ = "E:\bang\"
EXIT FUNCTION


DIM InRegs AS RegType, OutRegs AS RegType 'CPU registers.

'use DOS to find out where the Program Segment Prefix (PSP) is.

InRegs.ax = &H6200
CALL Interrupt(&H21, InRegs, OutRegs) 'DOS call.
DEF SEG = OutRegs.bx 'establish segment for PEEKing.

'get the segment address of the DOS environment from the PSP.

LSB% = PEEK(&H2C): MSB% = PEEK(&H2D) 'least & most significant bytes.
EnvSeg& = 256 * MSB% + LSB% 'make into an address.
DEF SEG = EnvSeg& 'point to environment segment.

'read the Environment until two Chr$(0) in a row are found. This marks the
'end of the environment. Skip the next 2 bytes and then read and save the
'ASCIIZ string which contains the complete drive, path and name of the
'program. (Only available with DOS 3.0 and later).

Offset% = 0 'index into memory locations.

DO
Byte1% = PEEK(Offset%)
Offset% = Offset% + 1
IF Byte1% = 0 THEN Byte2% = PEEK(Offset%)
LOOP UNTIL Byte1% = 0 AND Byte2% = 0

Offset% = Offset% + 3 'skip the last Chr$(0) and next 2 bytes.

DO
Path$ = Path$ + CHR$(PEEK(Offset%))
Offset% = Offset% + 1
LOOP UNTIL PEEK(Offset%) = 0

DEF SEG 'point back to BASIC segment.

'last job. Strip the program name and just return the drive and path.
'NOTE: that the path ends with a backslash - C:\GEORGE\BURNS\

Ndx% = LEN(Path$)
DO
Ndx% = Ndx% - 1
LOOP UNTIL MID$(Path$, Ndx%, 1) = "\"

GetProgPath$ = LEFT$(Path$, Ndx%)

END FUNCTION