title: What does the 9 mean, in -r option: zip -r9 ${OLDPWD}/package .?
body: <p>Context:
  AWS documentation on how to create zip files for python code with dependencies, see: <a href="https://docs.aws.amazon.com/lambda/latest/dg/lambda-python-how-to-create-deployment-package.html" rel="noreferrer">https://docs.aws.amazon.com/lambda/latest/dg/lambda-python-how-to-create-deployment-package.html</a></p>
  
  <p>I understand -r is recursion flag, but I'm unclear what the "9" in -r9 achieves?</p>
  
  <pre><code>~/my-function$ cd package
  ~/my-function/package$ zip -r9 ${OLDPWD}/function.zip .
    adding: PIL/ (stored 0%)
    adding: PIL/.libs/ (stored 0%)
    adding: PIL/.libs/libfreetype-7ce95de6.so.6.16.1 (deflated 65%)
    adding: PIL/.libs/libjpeg-3fe7dfc0.so.9.3.0 (deflated 72%)
    adding: PIL/.libs/liblcms2-a6801db4.so.2.0.8 (deflated 67%)
  ...
  </code></pre>