BBC BASIC for Windows
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How do I read text from a file?
Post by anonymous2506 on Mar 21st, 2016, 11:41pm

Hello

I'm currently working on an encryption program that requires encrypted text to be read from a file, encrypted and then fully decrypted.

Having finished the encryption and decryption part, i am having trouble with actually obtaining the file - here is what i have done so far:

max%=100
DIM text$(max%)
index% = 0
file% = OPENINtitle$
IF file% = 0 ERROR 100, "Couldn't open "title$
REPEAT
READ file%, text$
IF ASC(text$) = 10 text$ = MID$(text$,2)
index% += 1
text$(index%) = text$
UNTIL EOF#file% OR index% = max%
CLOSE #file%
total% = index%

When i enter a valid file name in (hello.txt) it comes up with the 'couldn't open' error message.

Thank you for any help in advance.

Anonymous2506
Re: How do I read text from a file?
Post by michael on Mar 22nd, 2016, 12:20am

That's all I did was work with compression of data in files and extraction.

Here is my simplest example of data write and read.

This is really all a person needs to set up any data base or encryption.. The thing with encryption I could show you but I would be posting code that cant be here.

(when I translate it I will post an example, and that's pretty easy)

This is BBC Basic version... I'm only a week here so... I am trying to learn as I post..

Code:
 REM THE SIMPLEST FILE DATA MANAGEMENT EXAMPLE ON THIS FORUM !!
      REM OPEN A FILE FOR OUTPUT AND WRITE 4 DIFFRENT PIECES OF DATA (Even if it doesnt look like it)
      A=OPENOUT(@usr$+"JUNK.DAT")
      REM The next command line will write 3 strings and 1 number to the file*******
      REM VVVVV notice how A becomes an identifier or device handle FOR THE FILE YOU MAKE***
      PRINT#A,"REALLY?","THERE ARE",4,"DATA SECTIONS TO THIS DATA"
      CLOSE#A
      REM OPEN A FILE AND READ THE CONTENTS AND PRINT THEM ON THE SCREEN
      A=OPENIN(@usr$+"JUNK.DAT")
      REM VVVVV notice how A becomes an identifier or device handle FOR THE FILE YOU READ***
      INPUT#A,A$,B$,N,C$
      PRINT A$;" ";B$;" ";N;" ";C$
      REM ^^^^^^ The read must be the same as the written file for accuracy ^^^^^
      REM break down the elements of the data so they can see
      PRINT
      PRINT "1 ";A$
      PRINT "2 ";B$
      PRINT "3 (this is not a string) -";N
      PRINT "4 ";C$
      END
Re: How do I read text from a file?
Post by DDRM on Mar 22nd, 2016, 2:12pm

Hi Anon,

I suspect that the file you are trying to open is not in the folder where BB4W is looking! If the program is saved and run from there, it will look in the same folder.

If you use
file%=OPENIN""

(or OPENIN"*.txt")

Then a file selection window will open, allowing you to browse to your file.

I note that your code snippet includes

READ file%,text$

... but to read from a file you should use READ# (or INPUT#):

READ#file%,text$

Hope that helps,

D
Re: How do I read text from a file?
Post by KenDown on Apr 3rd, 2016, 04:14am

I wonder if you would find the following bit of code useful?

REM ----- Find the data directory -----
atdir$=@dir$
F%=OPENIN(atdir$+"NewNames2.txt"):CLOSE#F%
IFF%=0THEN
dirletter%=67
REPEAT
atdir$=CHR$dirletter%+":\U3A\"
F%=OPENIN(atdir$+"NewNames2.txt"):CLOSE#F%
IFF%=0dirletter%+=1
UNTILF%>0ORdirletter%=79
IFdirletter%=79PROCwarn("Data file not found"):WAIT 500:QUIT
ENDIF

This starts off by looking in the same directory as the program (@dir$) but if it doesn't find the required file it begins at C:\ and checks if the file is on the C:\ drive. If not it looks in D:\ and so on down to O:\ (CHR$79) You can alter the 79 if you want to proceed beyond O!

Notice that the file I am looking for in this program will always be in a directory called "U3A". You will need to alter that if your file is in some other directory.


If you are using strings in a text file, I find that the easiest way of handling them is like this:

REM To write a string
BPUT#filehandle%,string$+CHR$13

REM To read a string
string$=GET$#filehandle%:IFstring$=""string$=get$#filehandle%

By adding CHR$13 you make your file easily readable by you - each item is on a separate line. However GET$# reads the CHR$13 as a separate, blank line. A trifle annoying but worth it for the convenience of having a human-readable file.