extcheck [-verbose] jarfile
extcheck checks to see if the extension contained in the specified jarfile (or a newer version of that extension) has already been installed on the system. It does this by reading the Specification-Title and Specification-Version manifest attributes from the specified jarfile and from all of the JAR files found in the system extensions directory.
extcheck is designed for use in automated installation scripts. Without the -verbose option, it does not print the results of its check. Instead, it sets its exit code to 0 if the specified extension does not conflict with any installed extensions and can be safely installed. It sets its exit code to a nonzero value if an extension with the same name is already installed and has a specification version number equal to or greater than the version of the specified file.