How can I close this file (and only this one)?

[Tourist Trap]

I have a file opened and created with Open() that I can not close. It's more for the challenge than a real life issue but it's a relatively funny issue.

Code: Select all

........  'any code (can't be changed)
........
open "xfile" for output as #(freefile())   'code can't be changed before this line of code

'close #(freefile())  ----> crash

Do someone see a way to close it in a quick way, avoiding crash? --- edit: without changing this dumb open method.

[MrSwiss]

Code: Select all

'close #(freefile())  ----> crash
close    ' closes all open Files (no comment, crash etc.)

The problem is:
you are assigning #2 (while attempting to "close"), to a File opened as #1 ...

[jevans4949]

Code: Select all

Dim xfileno As Integer
xfileno = FreeFile
Open "xfile.txt" For Output As #xfileno
Print #xfileno, "Hello, World"
Close #xfileno

[Tourist Trap]

Code: Select all

Dim xfileno As Integer
xfileno = FreeFile
Open "xfile.txt" For Output As #xfileno
Print #xfileno, "Hello, World"
Close #xfileno

Hi jevans4949, hi Mr.Swiss,

you failed here since the challenge is precisely to close the file when it has been opened without obvious record of the file handle. It can perfectly occure if you have a thing like #include "someverylongandtediousfile.bas". So the question is how to do then.

Ok, maybe usage of Close() alone can do the job but it's rather radical because it closes every files. Is there another way to close only this given file, or say the last opened file??

[MrSwiss]

A hack:

Code: Select all

open "xfile" for output as #(freefile())
dim as long ff = FreeFile
close( #(ff-1) )

No more "later changing Rules", please!

[Tourist Trap]

A hack:

Code: Select all

open "xfile" for output as #(freefile())
dim as long ff = FreeFile
close( #(ff-1) )

No more "later changing Rules", please!

There is no changing rules. I probably should have been more precise about the fact that I wished the most general solution as possible, something that would work even from inside a program as complex as possible.
I know that freeFile() returns the more little unused value, but I could also have used a random number. It's just that with freeFile() it's more funny since this function is theorically designed to avoid any problem. But what is already a little difficult is that the freeFile() result must be saved in a variable outside the Open statement.

So maybe there is no solution, but who knows?

[MrSwiss]

It appears to me, that you're trying to be difficult, because it can also be done without a Variable.

Code: Select all

close( (FreeFile()-1) )

This closes the "last" opened File.

[Tourist Trap]

It appears to me, that you're trying to be difficult, because it can also be done without a Variable.

Code: Select all

close( (FreeFile()-1) )

This closes the "last" opened File.

This works indeed!
At least I would just do this differently:

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open "x" for output as #(freefile())
dim as long lastUsedFF => FreeFile() - 1
'....
close #lastUsedFF 

Doing so there is no fear to loose track of the file number if some new freefile is called before the file is closed.

Now this below is more complicated.

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open "x" for output as #(cInt(256*rnd()))
'close #?

[MrSwiss]

Doing so there is no fear to loose track of the file number if some new freefile is called before the file is closed.

This is exactly what I've been trying to "get across" the whole Day long!

[Tourist Trap]

This is exactly what I've been trying to "get across" the whole Day long!

I didn't say that "in general". If we are inside a function, then the local variable will possibly get lost at exiting while the handle is persistent. That's a remark I've made in the topic about the files functions, opened in documentation section. I still don't know the complete rule for file handle numbers (when are they destroyed exactly), but they seem clearly to have a longer lifetime than local variables.

[fxm]

This is much more complicated, because the same file can be open simultaneously multiple times in input and once in output:

Code: Select all

Open "test.txt" for output As #1
  Print #1, "FreeBASIC"
  Print #1, "1.06.0"
Close #1

Open "test.txt" for input As #1
  Dim As String s1
  Line Input #1, s1
  Open "test.txt" for input As #2
    Dim As String s2
    Line Input #2, s2
    Print s2
    Line Input #2, s2
    Print s2
    Print
    Open "test.txt" for output As #3
    Print #3, s1 & " " & s2
    Close #3
  Close #2  
Close #1

Open "test.txt" for input As #1
  Dim As String s
  Line Input #1, s
  Print s
Close #1

Sleep

[integer]

I have a file opened and created with Open() that I can not close. It's more for the challenge than a real life issue but it's a relatively funny issue.

Code: Select all

........  'any code (can't be changed)
........
open "xfile" for output as #(freefile())   'code can't be changed before this line of code

'close #(freefile())  ----> crash

Do someone see a way to close it in a quick way, avoiding crash? --- edit: without changing this dumb open method.

immediately following the open statement, get the file handle.

Code: Select all

...
open "xfile" for output as #(freefile())   'code can't be changed before this line of code
dim as integer dom = freefile -1
...
close #dom

[Tourist Trap]

immediately following the open statement, get the file handle.

Code: Select all

...
open "xfile" for output as #(freefile())   'code can't be changed before this line of code
dim as integer dom = freefile -1
...
close #dom

Yep. I would have prefered something like dom=handle("x") but remains probably very tricky.

[Tourist Trap]

immediately following the open statement, get the file handle.

Code: Select all

...
open "xfile" for output as #(freefile())   'code can't be changed before this line of code
dim as integer dom = freefile -1
...
close #dom

Yep. I would have prefered something like dom=handle("x") but remains probably very tricky.

This is much more complicated, because the same file can be open simultaneously multiple times in input and once in output

You are right, and I find that file management in FB is rather complicated in general.

[noop]

Perhaps I misunderstood what was written above but the following seems dangerous:

Code: Select all

open ... as #freeFile()
dim as long ff = freeFile()-1
close #ff

As far as I'm aware, internally, there is an array of file handles. freeFile simply returns the smallest index into the array with an empty cell. So you could open 10 files in a row and get the file numbers 1 to 10.
Then close #5 and query freeFile. It should return 5. After that freeFile should return 11. Thus the code above wouldn't work.