How can I dynamically build a Java classpath in Perl?

Question

For Example in shell script:

_CLASSPATH =.
for jar in lib/*.jar
do
    _CLASSPATH=${_CLASSPATH}:${jar}
done

How can I dynamically build a Java classpath in Perl?

Answer 1

Not Perl code (no code = no bugs :) but doesn't

export CLASSPATH=.:lib/*

work? In my bash script that starts Java app I set this and app can "see" all .jars I want, but you can set it "globally":

mn@test:~# export CLASSPATH=.:/usr/local/jars/*
mn@test:~# echo $CLASSPATH
.:/usr/local/jars/*
mn@test:~# ls /usr/local/jars/*.jar
/usr/local/jars/activation.jar ...

mn@test:/home# cat show_cp.java
public class show_cp
{
    public static void main(String[] args)
        {
        System.out.println(System.getProperty("java.class.path", "."));
        }
}

mn@test:/home# java show_cp
.:/usr/local/jars/postgresql-8.4-701.jdbc4.jar:/usr/local/jars/RmiJdbc.jar:/usr/local/...

---

EDIT:

You can use wildcards in CLASSPATH as described in Setting the class path

---

And Perl code to join file names:

my @files = glob "/jars/*.jar";
my $cp = join(":", @files);
print($cp)

Answer 2

As always with Perl, there's more than one way to do it, but one compact way is this:

$_CLASSPATH = join(":", ".", glob("lib/*.jar"));

If you want to set an environment variable you may need to make that:

$ENV{_CLASSPATH} = join(":", ".", glob("lib/*.jar"));

Answer 3

my $_CLASSPATH = join(":", ".", glob("lib/*.jar"));
$ENV{CLASSPATH} = $_CLASSPATH;

NOTE: If you're in a web server environment, especially one that has shared Perl interpreter like mod_perl, always localize your $ENV{} assignments to avoid unpleasantness: local $ENV{CLASSPATH}=$_CLASSPATH;

Answer 4

You can try:

$CP = '.';
foreach(<lib/*.jar>) {
  $CP .= ":$_";
}
$ENV{'_CLASSPATH'} = $CP;