Expert: Alex Barry - 3/12/2009

Question
QUESTION: Hi Alex, i hope you can give me some idea regarding my problem. Can I pass a parameter coming from the outside of the program? For example I have a program named 'PROGRAM.BAS', can I pass a parameter on this by executing PROGRAM Jojo 1234? Wherein the Jojo and 1234 value will be accepted inside the PROGRAM.BAS and manipulated.

ANSWER: Hi, Jojo,

What you'll want is to use the COMMAND$() built-in array.  I'm not sure if this will work without compiling the program, though.
To call the script, you'd do something like:
qb.exe yourBasicCode.bas arg1 arg2 3

You'll have to play around with the command to get it working right.

You may want to make a command like this:

FUNCTION HasCommandLine( lookFor AS STRING, index AS INTEGER )
 DIM i AS INTEGER
 HasCommandLine = -1
 IF index < 0 THEN
   FOR i = LBOUND( COMMAND$ ) TO UBOUND( COMMAND$ )
     IF LCASE$( COMMAND$( i ) ) = LCASE$( lookFor ) THEN
       HasCommandLine = i
       EXIT FUNCTION
     END IF
   NEXT i
 ELSE
   IF LCASE$( COMMAND$( index ) ) = LCASE$( lookFor ) THEN
     HasCommandLine = index
     EXIT FUNCTION
   END IF
 END IF

END FUNCTION

I hope that helps you out,
-Alex

---------- FOLLOW-UP ----------

QUESTION: Thanks for the help on my first problem Alex. I hope you wouldn't mind if I ask a follow question. For example, I have a file SAMPLE.DAT, what command will I used to check if this file really exist before I use it? In CLIPPER or FOXPRO there is a File() function which check first the presence of the file by returning TRUE or FALSE. Is there an equivalent basic command for this? Thank you and more power.

Answer
Hi, Again,

QBasic doesn't have a built in function to see if a file exists.  There are a few "hacks" to look for a file, though.

FUNCTION FileExists( path AS STRING ) AS INTEGER
 FileExists = NOT 1
 SHELL "DIR /B " + path + " > tmp.txt"
 DIM f AS INTEGER
 f = FREEFILE
 OPEN "tmp.txt" FOR INPUT AS #f
   IF LOF( f ) THEN FileExists = 1
 CLOSE #f
 KILL "tmp.txt"
END FUNCTION

IF FileExists( "c:\randomfile.dat" ) THEN ...
IF NOT FileExists( "SAMPLE.DAT" ) THEN ...

That should work, if not, let me know, and I'll see what can be done,
-Alex