Question

I am searching for a .class file inside a bunch of jars.

jar tf abc.jar 

works for one file. I tried

find -name "*.jar" | xargs jar tf

prints nothing. The only solution I can think of, is unzip all, then search. Is there a better way? I’m on LUnix.

Edit:
When scanning many jars, it is useful to print the jar file name along with the class. This method works well:

find . | grep jar$ | while read fname; do jar tf $fname | grep SchemaBuilder && echo $fname; done

Sample output produced:

  1572 Wed Jul 25 10:20:18 EDT 2007 org/apache/ws/commons/schema/SchemaBuilder$1.class
  1718 Wed Jul 25 10:20:18 EDT 2007 org/apache/ws/commons/schema/SchemaBuilder$2.class
 42607 Wed Jul 25 10:20:18 EDT 2007 org/apache/ws/commons/schema/SchemaBuilder.class
./XmlSchema-1.3.2.jar
  1572 Wed Jul 25 10:20:18 EDT 2007 org/apache/ws/commons/schema/SchemaBuilder$1.class
  1718 Wed Jul 25 10:20:18 EDT 2007 org/apache/ws/commons/schema/SchemaBuilder$2.class
 42607 Wed Jul 25 10:20:18 EDT 2007 org/apache/ws/commons/schema/SchemaBuilder.class
./XmlSchema.jar

Answer 1

You need to pass -n 1 to xargs to force it to run a separate jar command for each filename that it gets from find:

find -name "*.jar" | xargs -n 1 jar tf

Otherwise xargs‘s command line looks like jar tf file1.jar file2.jar..., which has a different meaning to what is intended.

A useful debugging technique is to stick echo before the command to be run by xargs:

find -name "*.jar" | xargs echo jar tf

This would print out the full jar command instead of executing it, so that you can see what’s wrong with it.