.net detecting file in use

[ASB]

I have 2 processes writing some info to the same file. It's a small file the contents of which get replaced.

I'm trying to figure out a reliable way of detecting the file is in use so I Can abort or retry or whatever.

I create a FileStream using Mode=Create, Access=Write, Share=None

The problem is that this will throw an IOException if the file is in use. But I can't tell that this is the problem. It could be any other FileException. The only way I could tell is to look at the exception message.

Any suggestions? Surely there must be a simple way. Haven't turned anything by googling so maybe not.

[eek]

I have 2 processes writing some info to the same file. It's a small file the contents of which get replaced.

I'm trying to figure out a reliable way of detecting the file is in use so I Can abort or retry or whatever.

I create a FileStream using Mode=Create, Access=Write, Share=None

The problem is that this will throw an IOException if the file is in use. But I can't tell that this is the problem. It could be any other FileException. The only way I could tell is to look at the exception message.

Any suggestions? Surely there must be a simple way. Haven't turned anything by googling so maybe not.

Use a separate lock file. If lock file exists don't try to open the file. If lock file doesn't exist open file and then create lock file. When file is closed remove the lock file.

The next stop would be to check if the lock file has existed for a significant amount of time. If it has kill the other process and restart that program.

Granted its a rather unix way of managing files but if it works steal it.

[russell]

I have 2 processes writing some info to the same file. It's a small file the contents of which get replaced.

I'm trying to figure out a reliable way of detecting the file is in use so I Can abort or retry or whatever.

I create a FileStream using Mode=Create, Access=Write, Share=None

The problem is that this will throw an IOException if the file is in use. But I can't tell that this is the problem. It could be any other FileException. The only way I could tell is to look at the exception message.

Any suggestions? Surely there must be a simple way. Haven't turned anything by googling so maybe not.

I assume you don't want to write code that looks at the message because it is a string and isn't all type safe etc?

[russell]

Use a separate lock file. If lock file exists don't try to open the file. If lock file doesn't exist open file and then create lock file. When file is closed remove the lock file.

The next stop would be to check if the lock file has existed for a significant amount of time. If it has kill the other process and restart that program.

Granted its a rather unix way of managing files but if it works steal it.

What if another app is using the file, and that app doesn't implement your idea of creating lock files?

[NickFitz]

I assume you don't want to write code that looks at the message because it is a string and isn't all type safe etc? You could do exception.Message.Contains("in use") or something similar?

Should work a treat, except in Germany, or France, or Japan, or...

[fullyautomatix]

c# - Is there a way to check if a file is in use? - Stack Overflow

I think some kind of retry attempts logic mechanism is the only way to do it.

[fullyautomatix]

Well I was just giving an example, not going to do his job for him.

No you were offering a completely idiotic solution and Nick has rightly criticised it.

[eek]

No you were offering a completely idiotic solution and Nick has rightly criticised it.

+1 fullautomatix's stackoverflow link is the right approach if you simply want to check if a file .

If you have full control the unix lock file approach provides you with more information which may be useful if processes hit a snag.

[russell]

No you were offering a completely idiotic solution and Nick has rightly criticised it.

Yes it was a bit stupid. I have removed it now.

[AtW]

I have 2 processes writing some info to the same file.

Any suggestions? Surely there must be a simple way. Haven't turned anything by googling so maybe not.

1) Don't
2) Use DB