In Linux export PATH doesn't work but the giving classpath to javac works. Why?

[srikanthradix]

In Linux,

Why doesn't export PATH=path_to_lib doesn't work and -classpath works?

lib has all the jar files.

I exported the path to the lib folder.
export PATH=$PATH:/opt/lib

I also did export CLASSPATH=$CLASSPATH:$PATH

Then did a javac,

javac clazz.java

It is giving compilation problems.

Whereas, when we did javac --classpath /opt/lib/something.jar clazz works fine. Why is that?

[Norm]

What do the linux experts think about this problem?

[kjkrum]

Setting your CLASSPATH to the directory containing your jars isn't enough. java/javac won't automatically look inside all the jars in that directory.

Before I started using Eclipse, I had something like this in my .bashrc (or .bash_profile, I can't remember):

CLASSPATH="."
for fname in /home/kevin/lib/java/*.jar; do "CLASSPATH=$CLASSPATH:$fname"; done
export CLASSPATH

[kjkrum]

Also, out of curiosity, I found this: unix - Setting multiple jars in java classpath - Stack Overflow

Apparently Sun added wildcards to classpaths in Java 1.6. (Who knew?)

[srikanthradix]

javac -classpath /home/lib/*.jar clazz.java seems to be working. But, I can't believe that PATH doesn't work.
What is PATH then? I remember adding PATH to Windows environmental variables before running javac which worked before.

[kjkrum]

PATH is a list of locations your shell searches for a command or program. It's unrelated to Java's classpath.

Edit: Like if javac is located at /usr/bin/javac, and /usr/bin is in your PATH, then you can just type "javac" and the shell will find it. Classpaths are conceptually similar, but otherwise unrelated. They tell the JVM where to look for classes in the same way PATH tells the shell where to look for programs.