Is it possible to set standard output in Java both to a file and to the standard output?

Question

There is a Java command to redirect standard output to a file or back to the standart output:

PrintStream stdout = System.out;
System.setOut(new PrintStream(logFile));
// ...
System.setOut(stdout);

But I need to have both of them. Is it possible to set standard output in Java both to the file and to the standard output?

You can use a logger for doing this. Take a look at Apache log4j — Luca Negrini, Dec 06 '17 at 09:33
One might also opt to handle this at the shell level using `tee` or similar. For example, `java MyApp | tee logfile.txt`. See https://12factor.net/logs for further thoughts on logging to file vs stdout. — Oliver Charlesworth, Dec 06 '17 at 09:33
@GhostCat , my question already has an answer (see duplicate question's answer). I used that solution: TeeOutputStream from Apache Commons — Ivan Gerasimenko, Dec 08 '17 at 08:01
@GhostCat , I have used the solution: TeeOutputStream from Apache Commons (see duplicate question's answer) — Ivan Gerasimenko, Jul 19 '18 at 14:55

score 3 · Answer 1 · answered Dec 06 '17 at 09:31

I am not aware of a standard class doing that, but it is pretty simple:

first fetch the "ordinary" stdout PrintStream
write your own PrintStream implementation that writes to a file and to another Printstream
simply pass the original stdout to your new DoublePrintingPrintStream, and use setOut() to use that "double printing" stream

Alternatively, there are tools such as tee that can do that for you. So instead of bothering your Java code with that - simply have something outside read stdout, print to console and write to a file.

score -1 · Answer 2 · answered Dec 06 '17 at 09:35

-1

Use a Logger. If needed with a Layout just giving the input. Then you can, even in code add both a ConsoleAppender and a FileAppender.

Also better code style. And that "logFile" is telling.

answered Dec 06 '17 at 09:35

Joop Eggen

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Is it possible to set standard output in Java both to a file and to the standard output?

2 Answers2