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Active Forums => Programs => Topic started by: TempodiBasic on December 02, 2021, 09:10:29 pm

Title: File managing in Qbasic mode
Post by: TempodiBasic on December 02, 2021, 09:10:29 pm

Hi
here an example about how to manage if file exists or not in Qbasic way...
have a fun...

Code: QB64: [Select]

1. 'this code shows a feature/bug of Qbasic inherited by QB64
2. ' to duplicate experience please run this code into QB64 or Qbasic in DOSBOX
3.  
4. ' part 1 creates a file with a strange name so that it is difficult
5. ' to have it as real file in your pc
6. On Error GoTo ThisFile
7. filename$ = "1a2b3c4d.$$$"
8. Killing = 0
9. 'testing if file exists
10. Open filename$ For Input As #1
11. Print "File exists and opened "; filename$
12. On Error GoTo 0
13. TakeFile$ = Input$(LOF(1), # 1)
14. Close #1
15. Print TakeFile$
16. If Killing = -1 Then Kill filename$: Print "Deleted file "; filename$
17. End
18.  
19. ThisFile:
20. ' the file doesn't exist so it creates that and puts some data into file
21. Txt$ = "hello world"
22. Open filename$ For Binary As #1
23. Put #1, , Txt$
24. Close #1
25. Print "file created "; filename$
26. ' it says if the file must be delete at the end of code
27. Killing = -1
28. ' return on the linecode of error
29. Resume

in QB64 you need only of _Fileexists https://www.qb64.org/wiki/FILEEXISTS (https://www.qb64.org/wiki/FILEEXISTS)

Title: Re: File managing in Qbasic mode
Post by: SMcNeill on December 03, 2021, 12:44:51 am

OPEN file$ FOR BINARY AS #1
IF LOF(1) = 0 THEN NoExist = -1
CLOSE

IF NoExist THEN
    PRINT "File did not exist."
    KILL file$
END IF


The above also works well, generally speaking, as it's rather difficult to find 0-byte files on a drive, unless you just opened them yourself for some purpose (such as writing to them).  If YOU didn't make that 0-byte file, then should you really think of it as "existing"?  Isn't it the hard drive's equivalent of a blank string?

X$ = "" -- there's no X$.
LOF(1) = 0 -- there's no real file.

In the end, they're both just blank placeholders.

Title: Re: File managing in Qbasic mode
Post by: TempodiBasic on December 03, 2021, 06:54:05 pm

Hi Steve
I like that practical approach to the problem: zero file aren't files it is a good Occam razor.
But this truth is truth until

-you are not searching files to be cancelled like the temp files of OS (do you remember the cut of unuseful files from Windows' folder done in Win 95 and Win ME? The more was 0 files)

-do you use all modes to create a file into QBasic  except the print INPUT mode .
Very glad for seeing  your opinion!

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