Easy way to find JAVA_HOME

[Christian Heimes <li...@cheimes.de>]

Hello,

I found a much easier to detect the path to JAVA_HOME on Unix-like
platforms where the java command is in the search path. "java -verbose"
prints out the paths of all loaded JAR files.

Christian

---
import subprocess
import re
import os

PATH_RE = re.compile("Loaded\ .*\ from\ (.*)/jre/lib/rt.jar")

def find_java():
    """Find java home by running java -verbose

    In verbose mode, java prints lines like

        [Loaded java.lang.Object from
/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/rt.jar]

    to stdout.
    """
    try:
        proc = subprocess.Popen(["java", "-verbose"],
                                stdout=subprocess.PIPE)
    except OSError:
        return None
    out, err = proc.communicate()
    for line in out.split("\n"):
        mo = PATH_RE.search(line)
        if mo is None:
            continue
        javahome = mo.group(1)
        if os.path.isdir(javahome):
            return javahome

if __name__ == "__main__":
    print find_java()
---

Re: Easy way to find JAVA_HOME

[Andi Vajda <va...@apache.org>]

Please, send your question to the list, instead of me directly. I remember seeing your message originally and thinking to myself "what a hack, parsing this message, there's got to be a more deterministic way". Having seen quite a few ways to lay out Java on Linux, I also had zero confidence that this would cover all cases anyway. Is the definition of JAVA_HOME that it is the parent dir of 'jre' ? If so, where is that stated. ?
Thus my silence, hoping someone on the list would chime in with a counter-example.

Andi..

On Jun 20, 2012, at 4:03, Christian Heimes <ch...@cheimes.de> wrote:

> Hi Andi,
> 
> I posted the suggestion over a month ago and didn't hear back from you.
> Do you like my idea?
> 
> Christian
> 
> -------- Original-Nachricht --------
> Betreff: Easy way to find JAVA_HOME
> Datum: Tue, 08 May 2012 21:44:53 +0200
> Von: Christian Heimes <li...@cheimes.de>
> Antwort an: pylucene-dev@lucene.apache.org
> An: pylucene-dev@lucene.apache.org
> 
> Hello,
> 
> I found a much easier to detect the path to JAVA_HOME on Unix-like
> platforms where the java command is in the search path. "java -verbose"
> prints out the paths of all loaded JAR files.
> 
> Christian
> 
> ---
> import subprocess
> import re
> import os
> 
> PATH_RE = re.compile("Loaded\ .*\ from\ (.*)/jre/lib/rt.jar")
> 
> def find_java():
>    """Find java home by running java -verbose
> 
>    In verbose mode, java prints lines like
> 
>        [Loaded java.lang.Object from
> /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/rt.jar]
> 
>    to stdout.
>    """
>    try:
>        proc = subprocess.Popen(["java", "-verbose"],
>                                stdout=subprocess.PIPE)
>    except OSError:
>        return None
>    out, err = proc.communicate()
>    for line in out.split("\n"):
>        mo = PATH_RE.search(line)
>        if mo is None:
>            continue
>        javahome = mo.group(1)
>        if os.path.isdir(javahome):
>            return javahome
> 
> if __name__ == "__main__":
>    print find_java()
> ---