JAVA_HOME directory in Linux

问题:

Is there any linux command I could use to find out JAVA_HOME directory? I've tried print out the environment variables ("env") but I can't find the directory.

回答1:

echo $JAVA_HOME will print the value if it's set. However, if you didn't set it manually in your startup scripts, it probably isn't set.

If you try which java and it doesn't find anything, Java may not be installed on your machine, or at least isn't in your path. Depending on which Linux distribution you have and whether or not you have root access, you can go to http://www.java.com to download the version you need. Then, you can set JAVA_HOME to point to this directory. Remember, that this is just a convention and shouldn't be used to determine if java is installed or not.

回答2:

On Linux you can run $(dirname $(dirname $(readlink -f $(which javac))))

On Mac you can run $(dirname $(readlink $(which javac)))/java_home

I'm not sure about windows but I imagine where javac would get you pretty close

回答3:

I know this is late, but this command searches the /usr/ directory to find java for you

sudo find /usr/ -name *jdk

Results to

/usr/lib/jvm/java-6-openjdk
/usr/lib/jvm/java-1.6.0-openjdk

FYI, if you are on a Mac, currently JAVA_HOME is located at

/System/Library/Frameworks/JavaVM.framework/Home

回答4:

Just another solution, this one's cross platform (uses java), and points you to the location of the jre.

java -XshowSettings:properties -version 2>&1 > /dev/null | grep 'java.home'

Outputs all of java's current settings, and finds the one called java.home.

For windows, you can go with findstr instead of grep.

java -XshowSettings:properties -version 2>&1 | findstr "java.home"

回答5:

To show the value of an environment variable you use:

echo $VARIABLE

so in your case will be:

echo $JAVA_HOME

In case you don't have it setted, you can add in your .bashrc file:

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")

and it will dynamically change when you update your packages.

回答6:

If $JAVA_HOME is defined in your environment...

$ echo $JAVA_HOME
$ # I am not lucky...

You can guess it from the classes that are loaded.

$ java -showversion -verbose 2>&1 | head -1
[Opened /usr/lib/jvm/java-1.7.0-openjdk-1.7.0.75.x86_64/jre/lib/rt.jar]

This method ensures you find the correct jdk/jre used in case there are multiple installations.

Or using strace:

$ strace -e open java -showversion 2>&1 | grep -m1 /jre/
open("/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.75.x86_64/jre/bin/../lib/amd64/jli/tls/x86_64/libpthread.so.0", O_RDONLY) = -1 ENOENT (No such file or directory)

回答7:

On the Terminal, type:

echo "$JAVA_HOME"

If you are not getting anything, then your environment variable JAVA_HOME has not been set. You can try using "locate java" to try and discover where your installation of Java is located.

回答8:

Did you set your JAVA_HOME

• Korn and bash shells:export JAVA_HOME=jdk-install-dir
• Bourne shell:JAVA_HOME=jdk-install-dir;export JAVA_HOME
• C shell:setenv JAVA_HOME jdk-install-dir

回答9:

Here's an improvement, grabbing just the directory to stdout:

java -XshowSettings:properties -version 2>&1 \
   | sed '/^[[:space:]]*java\.home/!d;s/^[[:space:]]*java\.home[[:space:]]*=[[:space:]]*//'

回答10:

http://www.gnu.org/software/sed/manual/html_node/Print-bash-environment.html#Print-bash-environment

If you really want to get some info about your BASH put that script in your .bashrc and watch it fly by. You can scroll around and look it over.