# Extension in c, close file when script ends, rb\_io\_fptr\_fina

**URL:** <https://www.ruby-forum.com/t/extension-in-c-close-file-when-script-ends-rb-io-fptr-fina/88107>\
**Category:** Ruby\
**Created:** [March 8, 2007, 8:56am UTC](https://www.ruby-forum.com/t/extension-in-c-close-file-when-script-ends-rb-io-fptr-fina/88107 "2007-03-08T08:56:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![aflatter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/bcef8e/32.png) [@aflatter](https://www.ruby-forum.com/u/aflatter)\
**Post date:** [March 8, 2007, 8:56am UTC](https://www.ruby-forum.com/t/extension-in-c-close-file-when-script-ends-rb-io-fptr-fina/88107/1 "2007-03-08T08:56:12Z")

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hi,  
I wrote an extension that uses a file to handle an external device. The  
initialize method opens the file and it then is permanently open. I don’  
t  
want to open and close it every time I write to it.

I wondered how to finalize the object or to close the file when my  
script  
ends. Currently the file keeps open and I have an open unused device.

I stumbled over the function ‘rb\_io\_fptr\_finalize’, but I didn’ t find a  
real reference which tells me if that’ s what I searched for or not.

Can someone help me or give me further infos?

thanks,  
Alex.

---

<div class="post-metadata">

**Author:** ![aflatter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/bcef8e/32.png) [@aflatter](https://www.ruby-forum.com/u/aflatter)\
**Post date:** [March 8, 2007, 10:20am UTC](https://www.ruby-forum.com/t/extension-in-c-close-file-when-script-ends-rb-io-fptr-fina/88107/2 "2007-03-08T10:20:22Z")

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On Thu, Mar 08, 2007 at 04:55:11PM +0900, Alexander F. wrote:

> I wrote an extension that uses a file to handle an external device. The  
> initialize method opens the file and it then is permanently open. I don’ t  
> want to open and close it every time I write to it.
> 
> I wondered how to finalize the object or to close the file when my script  
> ends. Currently the file keeps open and I have an open unused device.

I’d recommend you copy the way that Ruby’s File class does it.

(1) Provide a ‘close’ method on your object, for the user to be able to  
explicitly close it when needed.

(2) Provide a block-based method, which does an open / yield / close  
sequence

```
File.open("/etc/passwd") do |f|
  puts f.read
end
# file is now closed at this point

```

(preferred implementation is to use begin … ensure … end, so that the  
close is called even if an exception occurs when the yield is called)

(3) Let the files close themselves when the program exits.

> I stumbled over the function ‘rb\_io\_fptr\_finalize’, but I didn’ t find a  
> real reference which tells me if that’ s what I searched for or not.

As I understand it, finalisers are called when the object is  
garbage-collected. However there’s not guarantee that an object will be  
garbage-collected at any time before the program exits (and not even  
then,  
if the user calls ‘exit!’)

However, if it’s just a file, the operating system will close the file  
when  
the program exits anyway.

B.