Serilog - how to customize date in rolling file name?

Question

In Serilog, you can easily enable rolling log files:

Log.Logger = new LoggerConfiguration()
    .WriteTo.File("log-.txt", rollingInterval: RollingInterval.Day)
    .CreateLogger();

This will create a new log file every day in the following format:

• log-20200214.txt
• log-20200215.txt
• log-20200216.txt

My question: is it possible to customize where the date is placed in the file name, and to customize how the date is formatted?

e.g. I want the file names to look like this:

• 2020-02-14-log.txt
• 2020-02-15-log.txt
• 2020-02-16-log.txt

I was hoping replacing "log-.txt" with "{Date:yyyy-MM-dd}-log.txt" would work, but it doesn't.

Nygaard

use $"{Date:yyyy-MM-dd}-log.txt", then it should work if you have a datefield, if not use instead of Date DateTime.Now – Fionnula

@Fionnula this solution doesn't work for me – Yang

i am too expecting the same. but, unfortunately no inbuilt methodology to format it. – Hostetler

Answer 1

This is not currently supported by the Serilog.Sinks.File sink. If you really want this feature, you can try to send a pull-request, or fork the repository and use your own custom implementation.

Links you might be interested in:

• Support {Date} for log path
• Serilog {Date} format when using RollingFile
• Ability to use DateTime format strings in Rolling File Sinks file names
• Support for path by date

Quaff

still not supported, except for the automatically added timestamp when time-based rolling is used? – Yang

Yes, that’s correct – Quaff

They already have a placeholder '{Timestamp:yyyy-MM-dd HH:mm:ss}' for the outputTemplate, why not applying this logic to the filename. Still not supported today unfortunately. – Rockafellow

Answer 2

Since this is currently not supported, I've made it with Map:

var log = new LoggerConfiguration()
            .WriteTo.Map(
            le => new DateTime(le.Timestamp.Year, le.Timestamp.Month, le.Timestamp.Day),
            (date, wt) => wt.File($"{date:yyyy-MM-dd}-log.txt"))
            .CreateLogger();

Checked the creation of a log file when the day changes via log.Write(new EventLog())

Stump