public static String execCommand(String... cmd) throws IOException {
        return execCommand(cmd, -1);
    }
Static method to execute a shell command.
Covers most of the simple cases without requiring the user to implement
the <code>Shell</code> interface.
@param cmd shell command to execute.
@return the output of the executed command.
clients/src/main/java/org/apache/kafka/common/utils/Shell.java