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Question concerning ruby file access

Stefan Salewski

10/30/2008 12:15:00 AM

Question concerning ruby file access from a novice:

I have seen following code fragment from

http://www.rubycentral.com/pickaxe/t...

File.open("testfile", "r") do |aFile|
# ... process the file
end

Advantage of this notation is that file is automatically closed when do
loop terminates -- maybe by an exception with Process.exit.

But how do I test in this notation that the file with name "testfile"
really exits (and opening was successful). In an multi-tasking
environment another process may delete the file just before this
statement is executed.

Or in other words: I want to print a text like "File with filename
"testfile" does not exist" when opening failed.

Best regards

Stefan Salewski
3 Answers

Sebastian Hungerecker

10/30/2008 12:25:00 AM

0

Stefan Salewski wrote:
> But how do I test in this notation that the file with name "testfile"
> really exits (and opening was successful). In an multi-tasking
> environment another process may delete the file just before this
> statement is executed.

If you want to completely avoid race conditions, you don't check - you just do
and then recover from eventual errors (i.e. you rescue the exception).

HTH,
Sebastian
--
Jabber: sepp2k@jabber.org
ICQ: 205544826

Ken Bloom

10/30/2008 1:20:00 AM

0

On Thu, 30 Oct 2008 00:14:57 +0000, Stefan Salewski wrote:

> Question concerning ruby file access from a novice:
>
> I have seen following code fragment from
>
> http://www.rubycentral.com/pickaxe/t...
>
> File.open("testfile", "r") do |aFile| # ... process the file
> end
>
> Advantage of this notation is that file is automatically closed when do
> loop terminates -- maybe by an exception with Process.exit.
>
> But how do I test in this notation that the file with name "testfile"
> really exits (and opening was successful). In an multi-tasking
> environment another process may delete the file just before this
> statement is executed.
>
> Or in other words: I want to print a text like "File with filename
> "testfile" does not exist" when opening failed.
>
> Best regards
>
> Stefan Salewski

begin
File.open("testfile") do |aFile|
...
end
rescue IOError => e
#handle error
end



--
Chanoch (Ken) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu...

Peña, Botp

10/30/2008 1:34:00 AM

0

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