How detect that a file is locked by another app?

Iltis

Hello driven,

Thank you for your answer, but I think it's not what I need.
In my case, in the real code (not my example here), the export is in a .dxf file. To test the quality/errors of the export, the .dxf file is open in a CAD software. Then, if I try in SU to overwrite the file with my plugin (after some modification in the SU model for example), and if the file is already opened in the CAD software, the file is locked by the CAD software. If I make this with a .txt file opened in Notepad++, there is no problem, because Notepad is not locking the file (and will detect the change!).
I want to track the error and say to the user to close the file in the CAD software or to rename the file.

(I'm french, sorry for my writting mistakes.)
Renaud.

TIG

out_name = UI.savepanel('Location', '' , "#{File.basename(model.path, ".*")}.txt")
begin
  if out_name && ! out_name.empty?
    if File.extname(out_name).downcase != ".txt"
      ### if the user erase the extension, we readd it!
      out_name += ".txt"
    end
    file = File.new(out_name, 'w')
    file.puts(%Q["blabla"])
    file.close()
  else
    puts "Canceled"
  end
rescue Exception => error
  puts error
  ### or do something else like
  UI.messagebox("#{error}\nFailed to export file #{file}")
end

Iltis

OK, will try it. Thank you!

TIG

Just noticed a typo!
I corrected the earlier code snippet...

if out_name &**&** ! out_name.empty?

One other thing to note is that some types of file are locked by the app that opens them - like a dxf.
But a txt file is opened by Notepad++.exe it is not locked, so its contents can be overwritten, you will then be asked when bringing that txt file's window foremost in Notepad++ if you want to reload it...

So try using the dxf file...
Or for a simple test write a .CSV file [remembering to force it to .csv, rather than .txt] AND have it already opened in Excel - which will lock it...

Jim

Did you try something like File.writable?("file")?

Class: File (Ruby 2.0.0)

Class : File - Ruby 2.0.0

(ruby-doc.org)

Iltis

TIG, your solution is working fine. Thank you very much.

@jim said:

Did you try something like File.writable?("file")?

Yes Jim, not working.

BR,
Renaud.

Jim

In that case I would write it like this. You might rescue StandardError also, but rescuing Exception is too broad. You generally want to rescue exceptions starting with the most-specific and work up to the least-specific.

[1] https://www.google.com/search?q=ruby+rescue+exception%26amp;ie=utf-8%26amp;oe=utf-8


def locked?(filename)
   locked = false
   begin
      file = File.open(filename, "w")
   rescue Errno;;EACCES => error
      locked = true
   ensure
      file.close if file
   end
   return locked
end

if $0 == __FILE__
   p locked?("test.txt")
end

thomthom

@jim said:

In that case I would write it like this. You might rescue StandardError also, but rescuing Exception is too broad. You generally want to rescue exceptions starting with the most-specific and work up to the least-specific.

+1

thomthom

Also, prefer opening files using block syntax so it always closes - saves you explicit rescue to close.

Jim

@unknownuser said:

Also, prefer opening files using block syntax so it always closes - saves you explicit rescue to close.

...which actually simplifies everything.


def write_to_file(filename)
   File.open(filename, "a") { |file|
      file.puts("Hello #{Time.now}")
   }
rescue Errno;;EACCES
   puts "Could not write to file."
end

Iltis

Thank you very much for these complementary solutions.

Renaud.