Separate Stderr and stdout stream at CLI using log4j configuration - ant

Question

I have an ANT based application and I have used slf4j logger to log at the exception, info, fatal etc. It is working fine. I am using log4j configuration for logging details. I used slf4j-log4j12-1.5.2.jar for this. Below is the configuration for logs.
log4j.rootLogger=info, file, stdout, stderr
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=cmd.log
log4j.appender.file.MaxFileSize=1024KB
log4j.appender.file.MaxBackupIndex=4
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{dd MMM yyyy HH:mm:ss,SSS} %-5p (%13F:%L) %3x - %m%n
log4j.appender.errorFile=org.apache.log4j.RollingFileAppender
log4j.appender.errorFile.File=error_stream.log
log4j.appender.errorFile.MaxFileSize=1024KB
log4j.appender.errorFile.MaxBackupIndex=4
log4j.appender.errorFile.layout=org.apache.log4j.PatternLayout
log4j.appender.errorFile.layout.ConversionPattern=%d{dd MMM yyyy HH:mm:ss,SSS} %-5p (%13F:%L) %3x - %m%n
log4j.appender.errorFile.Threshold=ERROR
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{dd MMM yyyy HH:mm:ss} %5p - %m%n
log4j.appender.stderr=org.apache.log4j.ConsoleAppender
log4j.appender.stderr.Threshold=WARN
log4j.appender.stderr.Target=System.err
log4j.appender.stderr.layout=org.apache.log4j.PatternLayout
log4j.appender.stderr.layout.ConversionPattern=%d{dd MMM yyyy HH:mm:ss} %5p - %m%n
I am calling my application through ant script as ant -f build.xml 1>out.txt 2>err.txt
Now it should stream all errors to err.txt. But its going into out.txt
Note : it is able to create error_stream.log and have errors. But not in err.txt
Do I am using wrong configuration properties?

Answer 1

Are you trying to define logging for your application launched by ANT? Or are you trying to define logging for ANT (the process encapsulating your application)?
If it's the latter, then ANT supports loggers and listeners, for an example:
Real time ant build analyzer

Answer 2

There is an issue with ant Task class. It handleErrorOutput as "warning" and further warning is stream into output stream.
You can modify the ant.jar with below changes. It will work.
Task_before_changes.java
protected void handleErrorOutput(String output) {
log(output, Project.MSG_WARN);
}
Task_after_changes.java
protected void handleErrorOutput(String output) {
log(output, Project.MSG_ERR);
}