I created a new .NET Core web project using Visual Studio and integrated Serilog. It reads settings from the appsettings.json (via .UseSerilog((ctx, config) => { config.ReadFrom.Configuration(ctx.Configuration); })).
In the appsettings.json, the path to write the log is specified at Serilog/WriteTo/Args/pathFormat. If I set that value to log.txt, it will attempt to write the file to `c:\program files\iisexpress\log.txt'.
How can I get it to write to the content root of my web app?
Ideally, you don't want to write log files to the content root of your web app, since these could end up being accessible over the web, which would be a serious security consideration.
The log file path configuration can include environment variables, so something like %TMP%\log.txt, or a path based on %LOCALAPPDATA% etc. is a good option (as long as the web site's worker process has permission to write to the location).
You can write to a path that's relative to your web app by changing the current directory before setting up the logger:
Environment.CurrentDirectory = AppContext.BaseDirectory;
Or, you can combine these approaches and set your own environment variable to do it:
Environment.SetEnvironmentVariable("BASEDIR", AppContext.BaseDirectory);
Thus the following config:
"%BASEDIR%\logs\log.txt"