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Moving from nlog to serilog, I would like my .NET framework desktop application to reuse a statically-named log file each time I run it, but to clear out the contents of the file with each new process. Is it possible to configure serilog this way?

This is a similar question, but it's not quite the same. In the linked question, the user uses a new log file each time with a unique filename. In my case, I want to use the same log file name each time.

Boinst
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1 Answers1

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This is not something Serilog can do for you as of this writing.

Serilog.Sinks.File is hard-coded to open the file with FileMode.Append thus if the file already exists, it will always append contents at the end of the file.

FileLifecycleHooks allows you to intercept when the file is being opened, and that would give you an opportunity to remove the contents of the file (by calling SetLength(0) on the stream), but unfortunately the stream implementation that Serilog.Sinks.File uses (WriteCountingStream) does not support SetLength.

Your best bet is to just truncate or delete the log file yourself at the start of the app, and let Serilog create a new one.

e.g.

// Ensure that the log file is empty 
using (var fs = File.OpenWrite("mylog.log")) { fs.SetLength(0); }

// ... Configure Serilog pipeline
C. Augusto Proiete
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  • I went with the suggestion from @c-augusto-proiete (thanks a bunch) my code looks something like this a few lines before calling `new LoggerConfiguration()`: ... `var f = new FileInfo("mylog.log");` `if (f.Exists)` `using (var s = f.Open(FileMode.Truncate))` `s.Close();` – Boinst Nov 05 '20 at 23:50
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    That works fine. You can omit the `Close` as you're calling `Dispose` already via `using`. An slightly shorter alternative would be to always create an empty file without checking if it exists e.g. `using (var fs = File.OpenWrite(@"C:\Temp\mylog.log")) { fs.SetLength(0); }` – C. Augusto Proiete Nov 06 '20 at 00:01