How to append hostname to log file in log4j.xml

Following configuration will do the trick

<appender name="file" class="org.apache.log4j.RollingFileAppender">
        <param name="append" value="false" />
        <param name="maxFileSize" value="10MB" />
        <param name="maxBackupIndex" value="10" />
        <param name="file" value="C:\\Users\\kavurira\\Desktop\\log4j-${HostName}.log" />
        <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" 
            value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m${HostName}%n" />
        </layout>
    </appender>

Just set "HostName" as system property, before initialization of Log4j.

System.setProperty("HostName", InetAddress.getLocalHost().getHostName());

Do this first from your java code then configure log4j into application,

NOTE : handle or catch required Exception while below code execute.

// step-1 : set hostName into System's property, which will use by log4j
System.setProperty("hostName", InetAddress.getLocalHost().getHostName()); 
//step - 2 : set currentDate into System's property, which will use by log4j
System.setProperty("currentDate", new SimpleDateFormat("dd-MMM-yyyy").format(new Date()));
//step - 3 : now configure/load log4j into Application , if it's not still loaded earlier then.
org.apache.log4j.Logger LOG = Logger.getLogger(YourJavaClassName.class); // ALERT : before this step above 2-step must needs to be execute, otherwise file-name won't appear as you required.

//LOG.debug("anything whatever programmer what to log");

UPDATED :

If your application is web-application, then need to configure property which we want here aftertomcat-server start and before any application run,

for that create one class ApplicationConfiguration which has ServletContextListener interface implemented which helps here to run first before any application runs.

do likewise,

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class ApplicationConfiguration implements ServletContextListener{

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {

        try {
            // step-1 : set hostName into System's property, which will use by log4j
            System.setProperty("hostName", InetAddress.getLocalHost().getHostName());
            //step - 2 : set currentDate into System's property, which will use by log4j
            System.setProperty("currentDate", new SimpleDateFormat("dd-MMM-yyyy").format(new Date()));
        } catch (UnknownHostException e) {
            System.out.println("Error Message : " + e.getMessage());
            //e.printStackTrace();
        } 


    }


}

......

Set your log4j.xml file likewise,

<appender name="applog" class="org.apache.log4j.DailyRollingFileAppender">
        <param name="File" value="${path}/app_${hostName}.${currentDate}.log" />
        <param name="MaxFileSize" value="1MB" />
        <param name="DatePattern" value=".dd-MM-yyyy" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="[%d{dd-MM-yyyy HH:mm:ss}] [%-5p] %m%n"/>
        </layout>
</appender>

please, update web.xml file accordingly,

<web-app ...>
   <listener>
    <listener-class>
             com.pck1.ApplicationConfiguration
        </listener-class>
   </listener>
</web-app>

This configuration need to apply into web.xml because application when start, by this configuration it will follow it like Context-listener.

---

UPDATE 2 :

<logger name="packageName.AAA" additivity="false" >
    <level value="INFO" />
    <appender-ref ref="applog"/>
 </logger>

Following the log4j2 documentation you can do environment variable lookups, so in Unix-like systems this should work:

<Property name="MYHOST">${env:HOSTNAME}</Property>
<Appenders>
  <File name="File1" fileName="${MYHOST}_file.log">
  ...
  </File>
</Appenders>

Beware that $HOSTNAME is not always available by default and you might need to export it explicitly in the shell, see this post.

I found that just ${hostName} by default would work for latest log4j

Something like this:

    <File name="file" fileName="${baseDir}/${hostName}-file.log" append="true">

This is documented under here: https://logging.apache.org/log4j/2.x/manual/configuration.html#AutomaticConfiguration

In the Default Properites Section:

The default map is pre-populated with a value for "hostName" that is the current system's host name or IP address