Automate brew update && brew upgrade via crontab

[spinuz09]

Output of brew config

HOMEBREW_VERSION: 5.1.1
ORIGIN: https://github.com/Homebrew/brew
HEAD: 894a3d23ac0c8aaf561b9874b528b9cb2e839201
Last commit: 3 days ago
Branch: stable
Core tap JSON: 25 Mar 21:03 UTC
Core cask tap JSON: 25 Mar 21:03 UTC
HOMEBREW_PREFIX: /usr/local
HOMEBREW_CASK_OPTS: []
HOMEBREW_DOWNLOAD_CONCURRENCY: 8
HOMEBREW_FORBID_PACKAGES_FROM_PATHS: set
HOMEBREW_MAKE_JOBS: 4
Homebrew Ruby: 4.0.1 => /usr/local/Homebrew/Library/Homebrew/vendor/portable-ruby/4.0.1/bin/ruby
CPU: quad-core 64-bit kabylake
Clang: 16.0.0 build 1600
Git: 2.53.0 => /usr/local/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 14.8.4-x86_64
CLT: 16.2.0.0.1.1733547573
Xcode: N/A

Output of brew doctor

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Some installed formulae are deprecated or disabled.
You should find replacements for the following formulae:
  icu4c@77

Warning: You have unlinked kegs in your Cellar.
Leaving kegs unlinked can lead to build-trouble and cause formulae that depend on
those kegs to fail to run properly once built. Run `brew link` on these:
  docker
  python@3.14

Warning: Homebrew's "sbin" was not found in your PATH but you have installed
formulae that put executables in /usr/local/sbin.
Consider setting your PATH for example like so:
  echo 'export PATH="/usr/local/sbin:$PATH"' >> ~/.zshrc

Warning: Broken symlinks were found. Remove them with `brew cleanup`:
  /usr/local/bin/compose-bridge

Description of issue

I am trying to automate brew update && brew upgrade && brew cleanup via crontab, to have it run on a daily basis in the morning.

I have the following cron-brew-update.sh script as follows:

#!/bin/bash
# script to update the system

# absolute paths*
HOMEBREW_BIN=/usr/local/bin/brew

# update commands.
$HOMEBREW_BIN update && $HOMEBREW_BIN upgrade && $HOMEBREW_BIN cleanup;

and crontab has the following:

30 9 * * * /Users/[username]/[path]/cron-brew-update.sh > /dev/null

However, brew does not actually update, I just get a system mail everyday at 9:30 as follows (that's the example for today; older ones would also appear but I deleted them yesterday):

Mail version 8.1 6/6/93.  Type ? for help.
"/var/mail/[username]": 1 message 1 new
>N  1 [username]@d  Thu Mar 26 09:30  18/850   "Cron <[username]@desktop> /Users/[username]/[path]/cron-brew-update.sh > /dev/null"

I also tried having the brew update and other commands directly in cron, but it just gives me the same result.

My goal is to have brew update/upgrade/cleanup on a daily basis and only have a notification if something went wrong (activity can be logged, but no spam notification).

What am I doing wrong?

PS: I searched for similar discussions and did find threads, but only for quite old discussions and could not find a working solution.

[SMillerDev]

Seems like https://github.com/DomT4/homebrew-autoupdate is what you're looking for. It's linked from: https://docs.brew.sh/Interesting-Taps-and-Forks

[spinuz09]

Thanks @SMillerDev. I was hoping to figure out what actually was not working (for the sake of understanding), but it is good to have a solution too :)

[SMillerDev]

I don't think the Homebrew forums will have a lot of info on debugging cron on macOS, launchd is a more common system on macOS. My debugging steps would be as follows:

1. You should read the email you got to see what the issue is
2. Try with >> instead of > because the current one might be trying to create a new /dev/null.

[spinuz09]

Oh I see, I assume this was a Homebrew issue. Anyway, thanks for the pointers, I will check that out.