Delphi: Check whether file is in use

delphi file handle
Arthur picture Arthur · Feb 2, 2009 · Viewed 14.7k times · Source

I want to write to/delete a file but sometimes I get a crash if the file is in use by another program. How do I check to see whether the file is opened by another process or I can open it for writing?

Answer

Binary Worrier picture Binary Worrier · Feb 2, 2009

The problem is, that between the time you check to see if you could get exclusive access and opening the file, something else gets exclusive access to the file, and you get the exception anyway.

The only fool proof way to see if you can get an exclusive lock on a file is to try and get an exclusive lock on the file, if you get it you have it.

If not, you catch the exception, and either

  • Go do something else
  • Wait a while and try again

It's one of life’s situations where it's better to ask for forgiveness than permission :)

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