How do I find out which version of Java I am using Perl?

Question

How do I find out which version of Java I am using Perl programming and using that execute some jar file based on that?

When you are using Perl, you are not using Java. Also, it's possible to have multiple versions of Java installed, but how you determine which is the default is system-dependent. — BlueRaja - Danny Pflughoeft, May 10 '10 at 15:30
It sounds like he wants to execute a jar file "based on" which Java version he is using.. so I'm thinking he has a few jar files for compatibility with different java versions. I don't know any Perl so I can't help though, but hopefully this will make it clearer to someone who does. — Paul, May 10 '10 at 15:37

Bill the Lizard · Answer 1 · 2010-05-10T15:45:06.953

5

You can capture the Java version from a Perl script using backticks.

$version = `java -version`;

Also see: How can I capture STDERR from an external command? for more alternatives than you can shake a stick at.

edited May 10 '10 at 15:45

answered May 10 '10 at 15:35

Bill the Lizard

the `>&1` is to redirect STDERR, but I tried it both ways. In either senario I get **$version = ""** – Eric Fossum May 31 '11 at 17:13

score 2 · Accepted Answer · answered May 10 '10 at 15:31

2

in a perl script,

@args = ("java", "-version");
system(@args) == 0
    or die "system @args failed: $?"

or rather simply,

system("java -version");

answered May 10 '10 at 15:31

phoenix24

1

Won't this just print the version out to the console without capturing it? I'm quite rusty at Perl, but I think if he wants to use the result he'll need to capture it with backticks. – Bill the Lizard May 10 '10 at 15:46
1

@Bill: you are correct. I'm not sure why the OP accepted this answer without testing it first. – Ether May 10 '10 at 16:41
@Bill I'm doing the same test and running `$capture = \`java -version>&1\``, but it won't capture anything and I get 0 for $? any help is appreciated – Eric Fossum May 29 '11 at 01:08
@Eric: What does the `>&1` at the end do? Can you try it without that and see what you get? (See my answer below.) – Bill the Lizard May 29 '11 at 02:28

score 0 · Answer 3 · answered Dec 15 '10 at 21:44

0

use IO::Handle;

open OUTPUT, '>', "output.txt" or die $!;
STDERR->fdopen( \*OUTPUT, 'w' ) or die $!;

print `java -version`;

answered Dec 15 '10 at 21:44

Eddie

1

For some reason, Java's -version goes to STDERR on Windows. – Eddie Dec 15 '10 at 21:45

score -1 · Answer 4 · answered May 10 '10 at 15:29

-1

"java -version" will show you the version you are using.

"perl -v" will show you the version of Perl you are using.

answered May 10 '10 at 15:29

decompiled

If this is how you do it _using perl_, how would you do it without perl? – Evan Carroll May 10 '10 at 15:52

score -1 · Answer 5 · answered May 10 '10 at 15:42

-1

Use the System command...

system("java -version");

If you are going to export a new Java

system('export PATH=/usr/java1.6/bin:$PATH');

answered May 10 '10 at 15:42

Thalaivar

`export` run from a `system()` call will not remain in effect after it ends. – Hasturkun May 10 '10 at 16:01

5 Answers5