My cronjob fails to run my Civimail queue. What am I missing here?
Your script is nicely designed for running the civi cron using "cv", quietly in the background. But you want to run it w/ noise so you can debug it.

To start, try running it manually without the last line and see if you get anything. The main script here is "cv" (run as a php script) and the other bits are making sure cv runs with the right arguments. If it's quitting silently, try something simpler, like seeing if you can actually run php and then if you can run cv via php with a simpler argument like "vars:show".

Documentation of cv is here: https://github.com/civicrm/cv