Hi,
Do I need to worry about closing a read-only FileStream when I am done reading from it?
What happens if I don't?
How can I tell if I have lots of open files in my system? "FileStream allInstances inspect"?
Thanks, Tim
On Mar 24, 2007, at 8:34 , Tim Johnson wrote:
Hi,
Do I need to worry about closing a read-only FileStream when I am done reading from it?
Yes. Always. A common pattern is
f := ... open the file stream .... [ ... do something with f ... ] ensure: [f close]
This ensures f is closed even if there is an error in your processing code.
What happens if I don't?
Bad Things ;) I'm not exactly sure.
How can I tell if I have lots of open files in my system? "FileStream allInstances inspect"?
You would need to use #allSubInstances and check if they're open.
- Bert -
The underlying OS has only a certain number of file handles that it can maintain open at a time. On UNIX-like systems, there is also possibly a maximum number of files per process. If this limit is hit, then no additional files can be opened, and on any attempt to do so an error is returned.
-Kyle H
On 3/24/07, Bert Freudenberg bert@freudenbergs.de wrote:
On Mar 24, 2007, at 8:34 , Tim Johnson wrote:
Hi,
Do I need to worry about closing a read-only FileStream when I am done reading from it?
Yes. Always. A common pattern is
f := ... open the file stream .... [ ... do something with f ... ] ensure: [f close]This ensures f is closed even if there is an error in your processing code.
What happens if I don't?
Bad Things ;) I'm not exactly sure.
How can I tell if I have lots of open files in my system? "FileStream allInstances inspect"?
You would need to use #allSubInstances and check if they're open.
- Bert -
Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
On Mar 24, 2007, at 3:45 AM, Kyle Hamilton wrote:
The underlying OS has only a certain number of file handles that it can maintain open at a time. On UNIX-like systems, there is also possibly a maximum number of files per process. If this limit is hit, then no additional files can be opened, and on any attempt to do so an error is returned.
For some reason I was confused and thought that Squeak's garbage collector would somehow make me immune from this. Like when the file was no longer being used, it would be closed and purged. Now I know otherwise :)
Thanks, Tim
On Mar 24, 2007, at 17:41 , Tim Johnson wrote:
On Mar 24, 2007, at 3:45 AM, Kyle Hamilton wrote:
The underlying OS has only a certain number of file handles that it can maintain open at a time. On UNIX-like systems, there is also possibly a maximum number of files per process. If this limit is hit, then no additional files can be opened, and on any attempt to do so an error is returned.
For some reason I was confused and thought that Squeak's garbage collector would somehow make me immune from this. Like when the file was no longer being used, it would be closed and purged.
Actually it is indeed. We use finalization for this [*]. However, you cannot know _when_ an object actually will be finalized, so you may be eating up handles nontheless.
Now I know otherwise :)
It's good practice not to rely on finalization, but treat it as a safety net.
- Bert -
[*] See for example http://www.mail-archive.com/beginners@lists.squeakfoundation.org/ msg01719.html or http://www.google.com/search?q=squeak+finalization
I think that some sort of diagnostic code printed out whenever an object's finalization routine must change the internal state of the object such that the criteria for finalization can be met would be a good thing.
i.e., if a FileStream is holding a file open, the finalization code should check to see that the file is closed. If it is not, it should warn about changing that state during the finalization.
Any finalization-related diagnostics should be treated the same way that other languages call "leaks", and quashed, regardless.
-Kyle H
On 3/25/07, Bert Freudenberg bert@freudenbergs.de wrote:
On Mar 24, 2007, at 17:41 , Tim Johnson wrote:
On Mar 24, 2007, at 3:45 AM, Kyle Hamilton wrote:
The underlying OS has only a certain number of file handles that it can maintain open at a time. On UNIX-like systems, there is also possibly a maximum number of files per process. If this limit is hit, then no additional files can be opened, and on any attempt to do so an error is returned.
For some reason I was confused and thought that Squeak's garbage collector would somehow make me immune from this. Like when the file was no longer being used, it would be closed and purged.
Actually it is indeed. We use finalization for this [*]. However, you cannot know _when_ an object actually will be finalized, so you may be eating up handles nontheless.
Now I know otherwise :)
It's good practice not to rely on finalization, but treat it as a safety net.
- Bert -
[*] See for example http://www.mail-archive.com/beginners@lists.squeakfoundation.org/ msg01719.html or http://www.google.com/search?q=squeak+finalization _______________________________________________ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Thanks!
- Tim
On Mar 24, 2007, at 3:25 AM, Bert Freudenberg wrote:
On Mar 24, 2007, at 8:34 , Tim Johnson wrote:
Hi,
Do I need to worry about closing a read-only FileStream when I am done reading from it?
Yes. Always. A common pattern is
f := ... open the file stream .... [ ... do something with f ... ] ensure: [f close]
This ensures f is closed even if there is an error in your processing code.
What happens if I don't?
Bad Things ;) I'm not exactly sure.
How can I tell if I have lots of open files in my system? "FileStream allInstances inspect"?
You would need to use #allSubInstances and check if they're open.
beginners@lists.squeakfoundation.org
-
Bert Freudenberg -
Kyle Hamilton -
Tim Johnson