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n00b
Asked: 2014-03-25 06:01:53 +0800 CST

What is the command to search for 64-bit installed Java, JRE or OpenJDK?

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I have a question about the following command:

apt-cache search java | awk '{print($1)}' | grep -E -e '^(ia32-)?(sun|oracle)-java' -e '^openjdk-' -e '^icedtea' -e '^(default|gcj)-j(re|dk)' -e '^gcj-(.*)-j(re|dk)' -e 'java-common'

Owing to my limited IT knowledge, am I right to say that the (ia32-) in the above command refers to 32-bit software? If it is, then I assume that the above command is for 32-bit installed OS.

However I installed a 64-bit OS.

What is the correct parameter for 64-bit software? Is it (amd64-) or (ia-64) or (x86_64-)?

Any expert help is much appreciated.

command-line

1 Answers

  1. Best Answer

    First of all, apt-cache search does not search for installed packages, it looks for available ones, both installed and not installed. Also, the various search patterns you see are not mutually exclusive, so lines matching any of them will be printed. Finally, the ? after ^(ia32-) means ia32- is optional, the expression will match lines that have it and lines that don't. So, your command will indeed work for 64 and 32 bit systems.

    The equivalent command to look for installed packages only would be:

    dpkg -l *java* | awk '{print($2)}' | 
    grep -E -e '^(ia32-)?(sun|oracle)-java' -e '^openjdk-' -e '^icedtea' \
      -e '^(default|gcj)-j(re|dk)' -e '^gcj-(.*)-j(re|dk)' -e 'java-common'

    But don't use that. In Debian derived systems such as Ubuntu, there is a special tool for this, update-java-alternatives which, when run with the -l option will list installed Java environments:

     update-java-alternatives -l

    On my system, for example, this prints:

    java-1.6.0-openjdk-amd64 1061 /usr/lib/jvm/java-1.6.0-openjdk-amd64
java-1.7.0-openjdk-amd64 1071 /usr/lib/jvm/java-1.7.0-openjdk-amd64
jdk-7-oracle-x64 317 /usr/lib/jvm/jdk-7-oracle-x64
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