To display the default last 10 lines for a file…
tail error_log.txt
To display a specified no of lines for a file…
tail -15 error_log.txt
‘Premature end of scrip headers’ error message refers to the script being stopped for whatever reason before it actually return any output to the browser.
The first time to check is to ensure the below codes are output first
print "Content-type: text/html\n\n";
And then to debug the error, simply add the below line(preferably after the above code).
use CGI::Carp qw(fatalsToBrowser);
Recently came across a problem whereby the quartz scheduler could not recreate a new log4j FileAppender log when the job is call again.
Googled a bit and found out a couple of solutions such as using a custom log4j classes, which create a seperate thread when being called in quartz scheduler.
I find that it is too complex and had try several ways to recreate the log file inside Quartz.
And finally came up with this one line of code.
Before I begin, let’s take a look at my log4j config.
This log4j config will create a simple console system out logger and also a FileAppender logger.
For my case, I want to re-create a new log file whenever this job is run.
log4j.rootLogger=INFO, stdout log4j.additivity.stdout=false log4j.additivity.joblog=false log4j.appender.ROOT.layout.ConversionPattern=[%d] %t %c %-5p - %m%n #console log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%d %p - %m%n #per job execution log log4j.logger.com.yourcompany=INFO, joblog log4j.appender.joblog=org.apache.log4j.FileAppender log4j.appender.joblog.layout=org.apache.log4j.PatternLayout log4j.appender.joblog.File=../jobtemp.log log4j.appender.joblog.Append=false log4j.appender.joblog.layout.ConversionPattern=%d %p - %m%n
and here’s the schedule job
public class ScheduleJob implements StatefulJob {
private static Logger logger = Logger.getLogger(ScheduleJob.class);
public void startJob() throws SchedulerException{
Scheduler scheduler =
StdSchedulerFactory.getDefaultScheduler();
scheduler.start();
}
public void execute(JobExecutionContext context)
throws JobExecutionException {
//reset log4j config for FileAppender
PropertyConfigurator.configure("../conf/log4j.properties");
RunJobImmediately newJob = new RunJobImmediately();
newJob.performJob();
}
public static void main(String args[]){
try{
ScheduleJob scheduleJob = new ScheduleJob();
scheduleJob.startJob();
}catch(Exception e){
logger.error(e);
}
}
}
and finally the one line of code to recreate the log file.
Apparently, this line will somehow ‘reload’ the log4j utitlies, which thus recreate the FileAppender logger to re-create the log file.
PropertyConfigurator.configure("../conf/log4j.properties");
Feel free to let me know if there is any performance issues or it is not working at your side.
Taken @ phuket
I noticed that some of the computer which I remote desktop to, could not be shutdown or restart. Instead of the normal shutdown or logoff, you will see a log off and disconnect button.
I googled out and the easiest way to restart/shutdown such computer via remote desktop is to bring out the user menu and shutdown/restart from there.
To do it, you simply press Ctrl + Alt + End key. Cheers.
Here’s the code snippets to display the number of running threads in your java program.
It’s good to use it to track your resources.
int activeCount = Thread.activeCount();
System.out.println("total active = " + activeCount);
Thread[] threads = new Thread[activeCount];
Thread.enumerate(threads);
System.out.println("before");
for (int j=0; j<threads.length; j++) {
System.out.println(threads[j].toString());
}
//run your classes
Benny benny = new Benny();
activeCount = Thread.activeCount();
System.out.println("total active = " + activeCount);
threads = new Thread[activeCount];
System.out.println("after");
Thread.enumerate(threads);
for (int i=0; i<threads.length; i++) {
System.out.println(threads[i].toString());
}