# Question concerning ruby file access

**URL:** <https://www.ruby-forum.com/t/question-concerning-ruby-file-access/152088>\
**Category:** Ruby\
**Created:** [October 30, 2008, 1:15am UTC](https://www.ruby-forum.com/t/question-concerning-ruby-file-access/152088 "2008-10-30T01:15:32Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![stefans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9d8465/32.png) [@stefans](https://www.ruby-forum.com/u/stefans)\
**Post date:** [October 30, 2008, 1:15am UTC](https://www.ruby-forum.com/t/question-concerning-ruby-file-access/152088/1 "2008-10-30T01:15:32Z")

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Question concerning ruby file access from a novice:

I have seen following code fragment from

[http://www.rubycentral.com/pickaxe/tut\_io.html](http://www.rubycentral.com/pickaxe/tut_io.html)

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 S.

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**Author:** ![stefans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9d8465/32.png) [@stefans](https://www.ruby-forum.com/u/stefans)\
**Post date:** [October 30, 2008, 1:26am UTC](https://www.ruby-forum.com/t/question-concerning-ruby-file-access/152088/2 "2008-10-30T01:26:03Z")

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Stefan S. 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

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**Author:** ![stefans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9d8465/32.png) [@stefans](https://www.ruby-forum.com/u/stefans)\
**Post date:** [October 30, 2008, 2:35am UTC](https://www.ruby-forum.com/t/question-concerning-ruby-file-access/152088/3 "2008-10-30T02:35:38Z")

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From: Stefan S. [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]

# Or in other words: I want to print a text like "File

# with filename “testfile” does not exist" when opening failed.

i usually think it like db’s logical unit of work or transaction. i just  
wrap it w ruby’s begin/end and a rescue check as mentioned by sebastian.

something like eg

> begin

- File.open(“test.rbx”) do |f|
- end

> rescue =\>e  
> p e.message  
> end  
> “No such file or directory - test.rbx”  
> =\> nil

note, you can have more rescues and finetune them. you can also make  
your own exceptions… just continue reading on the pickaxe…

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**Author:** ![stefans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9d8465/32.png) [@stefans](https://www.ruby-forum.com/u/stefans)\
**Post date:** [October 30, 2008, 2:40am UTC](https://www.ruby-forum.com/t/question-concerning-ruby-file-access/152088/4 "2008-10-30T02:40:54Z")

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

> loop terminates – maybe by an exception with Process.exit.
> 
> Stefan S.

begin  
File.open(“testfile”) do |aFile|  
…  
end  
rescue IOError =\> e  
#handle error  
end