How to determine and use the actual java path in a Linux shell script

Question

In a bash shell script on Ubuntu/Mint, I need to create some symlinks in the /jre/lib/ext/ directory under the java installation directory.

For example, if openjdk6 is the default java, /usr/bin/java points to:

/usr/lib/jvm/java-6-openjdk/jre/bin/java

I can find this in my script with:

MYJAVAPATH=readlink -f `which java`

The path I would need in my shell script would be based on part of that path, plus the path fragment above:

/usr/lib/jvm/java-6-openjdk/jre/lib/ext/

Can anyone tell me to to derive the path immediately above in a bash shell script? Thanks.

Could you just cd to that directory, back up to /jre/, then go into lib/ext ? Once there, then ln -s and get your symlinks in place? — Jack
– Jack, Commented Jan 30, 2012 at 0:08

Adam Zalcman · Accepted Answer · 2012-01-30 00:34:01Z

4

You can simply append the relative part ../lib/ext/

MYJAVAPATH="$(readlink -f $(which java))"
LIB_EXT="$(dirname ${MYJAVAPATH})/../lib/ext"

and then use ${LIB_EXT}.

answered Jan 30, 2012 at 0:16

Adam Zalcman

27.3k4 gold badges75 silver badges95 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

That is a complete answer. Thanks. And other than doing this: cd $LIB_EXT; LIB_EXT=$(pwd), how can I get rid of the /../ path element?

also, I don't want to have to install any additional programs (such as realpath).

Michael Ridley · Accepted Answer · 2012-01-30 00:16:30Z

1

You could use dirname such as

javalink=`which java`
javapath=`readlink $javalink`
javadir=`dirname $javapath`

answered Jan 30, 2012 at 0:16

Michael Ridley

10.6k3 gold badges25 silver badges16 bronze badges