title: Gsutil - How can I check if a file exists in a GCS bucket (a sub-directory) using Gsutil
body: <p>I have a GCS bucket containing some files in the path</p>
  
  <p>gs://main-bucket/sub-directory-bucket/object1.gz</p>
  
  <p>I would like to programmatically check if the sub-directory bucket contains one specific file. I would like to do this using gsutil. </p>
  
  <p>How could this be done?</p>