CODEWITHSUNDEEP
java
Thunderforge
Thunderforge

Reputation: 20575

How Can I Pipe the Java Console Output to File Without Java Web Start?

I am wanting to pipe the Java console output (generated by System.out.println and its ilk) to a file. I found an excellent solution here to enable Java tracing, but this isn't working for me (no log file shows up in any location on Mac OS X or Windows). From what I can tell, this is because I'm using a plain Java app without Java web start. So how can I do this with Java code that does not use Java web start? Ideally, I would like a solution that does not require modifying code.

Upvotes: 10

Views: 46931

Answers (4)

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 279960

You don't require Java web start to do any of this. Just set the System.out to a FileOutputStream.

System.setOut(new PrintStream(new FileOutputStream(fileName)));

where fileName is the full path to the file you want to pipe to.

public static void main(String[] args) throws Exception {
    System.setOut(new PrintStream(new FileOutputStream("home.txt")));
    System.out.println("hello");
}

This will write hello\n to a file named home.txt in the current working directory.

If you can't modify code, on Windows 7, use command redirection.

java YourMainClass > home.txt

If you need to run a jar, you can use the -jar option of the java application launcher.

java -jar /your/path.jar > /output/file/path.txt

Upvotes: 16

Zhefu Zhangzhu
Zhefu Zhangzhu

Reputation: 11

If you want to run the problem in the background, do this - 

nohup java -jar yourprogram.jar > log.txt 2>&1 &

Upvotes: 1

Stephen C
Stephen C

Reputation: 718798

Is there any way that I can do it without modifying code? I'd like to do it for an application that is already compiled.

If you want to do it without changing code, then your best option is this:

$ java com.example.MyMainClass > filename

Upvotes: 1

Katona
Katona

Reputation: 4901

If you launch it from command line, then you can use redirect stdout and stderr into file as follows:

java -jar application.jar >file.txt  2>&1

where you have to replace application.jar with the jar file of your application.

Upvotes: 24

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