How to check if the log directory is writable?

[PatriceDargenton]

Hello, in order to configure the log file path, you need to configure log4net, and then the log file is read-only. So how to check if the log file is accessible? If the log file is not accessible, logging will be disabled. And if the log file is accessible, the log file will be locked by log4net, so it is not possible to check if the file is accessible anymore. What is the right solution to this problem?

[FreeAndNil]

@PatriceDargenton I don't understand your problem exactly.
What are you trying to achieve?
Do you want to write with two applications in the same file?
Do you want to read the log file while the application is running?
Do you want to check whether the log file is currently locked by log4net?

[PatriceDargenton]

Logging with log4net is disabled in my app because users do not have write permissions for the log file configured in the log4net config.
So I need to inform users that logging is disabled (they should know, to ask somebody to fix the problem).
So I need to read this file configured in log4net, so I need to set up log4net : but if everything is ok, then the log file is locked by log4net, so how then can I check now if the file is write protected? I wish I could now close log4net before checking write access permissions to the file!

[FreeAndNil]

You want to know whether the user has the permission to create/append to the log file configured in the config file?

[PatriceDargenton]

Here it is:

<log4net>
  <root>
    <!-- ALL, DEBUG, INFO, WARN, ERROR, FATAL, OFF -->
    <level value="INFO" />
    <appender-ref ref="File" />
  </root>
   
  <appender name="File" type="log4net.Appender.RollingFileAppender">
    <file type="log4net.Util.PatternString" value="log\${USERNAME}-%date{yyyy-MM-dd}.log" />
    <appendToFile value="true" />
    <rollingStyle value="Size" />
    <countDirection value="1"/>
    <maxSizeRollBackups value="60" />
    <maximumFileSize value="1MB" />
    <staticLogFileName value="true" />
    <preserveLogFileNameExtension value="true"/>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date{HH:mm:ss.fff} %-5level %logger - %message%newline%exception" />
    </layout>
  </appender>
  <appender name="PerfFile" type="log4net.Appender.RollingFileAppender">
    <file type="log4net.Util.PatternString" value="log\perf\${USERNAME}-%date{yyyy-MM-dd}.log" />
    <appendToFile value="true" />
    <rollingStyle value="Size" />
    <countDirection value="1"/>
    <maxSizeRollBackups value="60" />
    <maximumFileSize value="1MB" />
    <staticLogFileName value="true" />
    <preserveLogFileNameExtension value="true"/>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date{HH:mm:ss.ffff} %-5level %logger - %message%newline" />
    </layout>
  </appender>
  <appender name="TraceAppender" type="log4net.Appender.TraceAppender">
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date{HH:mm:ss.ffff} %-5level %logger - %message%newline" />
    </layout>
  </appender>
<logger name="perf" additivity="false">
  <level value="OFF"/>
  <appender-ref ref="PerfFile" />
  <appender-ref ref="TraceAppender" />
</logger>
  <logger name="NHibernate" additivity="false">
    <level value="WARN" />
    <appender-ref ref="File" />
  </logger>
  <logger name="NHibernate.SQL" additivity="false">
    <level value="WARN" />
    <appender-ref ref="File" />
  </logger>
</log4net>

log\ is a directory on a shared network (provided by Linux I think) accessible to Windows users, in the same directory where the .exe file is located.
Bug logging does not work for almost all users (no write access to this directory).

[FreeAndNil]

What about this?

FileInfo file = new($"log\{Guid.NewGuid()}.txt");
try
{
  file.Create().Dispose();
  file.Delete();
  // success
catch (UnauthorizedAccessException)
{
  // failed
}

[PatriceDargenton]

Ok, that's a good idea, I'll test that, thanks.
But what would be nice would be to have a function to retrieve the log path before starting to write to the log file, or a Close() or Dispose() function.

[FreeAndNil]

This is possible, but you will need to create your own Appender class (derived from FileAppender) and override ActivateOptions().
Then change your config to use the new Appender class.
For your use case probably not the best option.

[PatriceDargenton]

Thank you!