What are syntax rules of the "jar -x" command for extracting entries from a JAR file? I am confused on how to specify different options, like v and f.

The "jar -x" command allows you to extract entries from an existing JAR file to the current folder. It has the follow syntax:

jar -x[vf] [jar-file] [pattern]

"v" option flag returns verbose information on standard output for each entry extracted. If "v" is not specified, nothing shows up on the standard output.

"f" option flag specifies the JAR file. If "f" is specified, "jar-file" must be provided. If "f" is not specified, the JAR file is read from the standard input.

If "pattern" specified, only those entries that match the pattern will be extracted If not specified, all entries in the JAR will be extracted.

Here are some example of valid "jar -x" commands

   jar -xf activation.jar
      Extract all entries in the JAR
      
   jar -xf activation.jar com/sun/activation/viewers/Image
      Extract all entries that matches the given pattern 

   jar -xvf activation.jar
      Extract all entries with information on the standard output

   type activation.jar | jar -xv
      Read the JAR file from the standard input

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