Ubuntu Question posted in
The official Ubuntu documentation can be found here.

Ubuntu – How to output the Java runtime version in one line to the shell?

Let’s say I want to get the content of java.runtime.version to the Linux shell.

I don’t want to call java -version and or doing any kind of grepping / sedding as we used this approach already in the past and it proved to be flaky.

➜  java -version
openjdk version "21" 2023-09-19 LTS
OpenJDK Runtime Environment Temurin-21+35 (build 21+35-LTS)
OpenJDK 64-Bit Server VM Temurin-21+35 (build 21+35-LTS, mixed mode)

This e.g. example contains too much output which changes from release to release and also from vendor to vendor.

What I tried already was using jshell:

But the output still contains all the command feedback which I cannot disable (At least I don’t know:

➜  printf $'System.out.println(java.lang.System.getProperty("java.runtime.version"));n/exitn' | jshell -s
-> System.out.println(java.lang.System.getProperty("java.runtime.version"))21+35-LTS
-> %

What I want in this example, is only the 21+35-LTS part in a reliable and future proof way.

I am open to use tools available in an Ubuntu slim base image or in the recent Java jdk.

EDIT: I am not opposed to grep/sed in general as long as the solution is half-way future proof and works with different Java vendors.

Tags:

3

Answers


  1. 0

    You can view all system properties with -XshowSettings, so something like this should work:

      java -XshowSettings:properties 2>&1 | grep java.runtime.version
    Login or Signup to reply.
  2. 0

    I don’t think it’s possible directly without some grepping/sedding of the output, but you can achieve it via an intermediate file, like this:

    echo 'Files.writeString(Path.of("java_version"), Runtime.version().toString())' 
  | jshell &>/dev/null 
  && cat java_version 
  && rm java_version
    • jshell &>/dev/null will make sure jshell doesn’t produce any output;
    • Runtime.version() is possibly a more straightforward alternative to System.getProperty("java.runtime.version").
    Login or Signup to reply.
  3. 0

    You could try using --list-modules. The way in which a module version is output seems to be more static (<module-name>@<version>). Ask for the version of a module that implements the Java Language SE Specification and you get the version of the runtime (eg. java.base).

    java --list-modules --limit-modules java.base

    outputs:

    [email protected]

    Add a cut

    java --list-modules --limit-modules java.base | cut -d@ -f2

    and you get:

    21.0.5

    NB. this version will not include any build information or vendor additions to the version. eg. On my system java.runtime.version is 21.0.5+11-Ubuntu-1ubuntu122.04

    This requires java 9 or above, and output format does not appear to have changed since java 9.

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search