how to update homebrew with Cron on Mac os

Question

I've been discvering some long lasting linux techs to help automate my daily work. I found cron to be very powerful if I can use it to check the updates of some packages I have on my system.

For example, I want to update my Homebrew everyday at 11pm. What I did is, with sudo crontab -u user -e, I opened up crontab in Vim. And I put following commands into it, to make updates for homebrew and send me an email.

Here's the code:

MAILTO=myemail@foo.com
* 23 * * * brew update

and I save it to wait for magic happens. Instead of excuting this command, in the email I recieved, it says /bin/sh: brew : command not found

But when I type /bin/sh in terminal to open sh and type in brew update it will update the Homebrew。

What did I do wrong with my crontab configuration?

Any help will be appreciated!

Answer 1

A cronjob is a good option, but I didn't want it to happen automatically. I found a script that will notify you if a new version of a formula installed on your Mac is available.

I extended the script to not show pinned formulae in the notifier.

I decided to use a launchd-agent for the cronjb, because this also runs if Mac is started later. Cron-jobs just run if your mac is already on at that time.

For a comparison of cronjob vs launchd, I recommend reading this.

Here's my configuration which runs every day at 10am and 3pm. The script, called by the agent, is located at /usr/local/bin/homebrew-update-notifier.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>EnableGlobbing</key>
    <false/>
    <key>Label</key>
    <string>homebrew.simonsimcity.update-notifier</string>
    <key>ProgramArguments</key>
    <array>
        <string>/bin/bash</string>
        <string>/usr/local/bin/homebrew-update-notifier</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>StandardErrorPath</key>
    <string>/tmp/homebrew.simonsimcity.update-notifier.err</string>
    <key>StandardOutPath</key>
    <string>/tmp/homebrew.simonsimcity.update-notifier.out</string>
    <key>StartCalendarInterval</key>
    <array>
        <dict>
            <key>Hour</key>
            <integer>10</integer>
            <key>Minute</key>
            <integer>0</integer>
        </dict>
        <dict>
            <key>Hour</key>
            <integer>15</integer>
            <key>Minute</key>
            <integer>0</integer>
        </dict>
    </array>
</dict>
</plist>

You will now be notified if a new update is available. Call brew upgrade if you feel outdated, or include it in the script.

Answer 2

Cron doesn't have your PATH defined, make sure you always call commands with the full path, which is probably /usr/local/bin/brew update

This is considered good practice to keep unwanted/unexpected commands from running. If someone put a malicious script called 'brew' somewhere else in your path, but before /usr/local/bin, it would get called instead.

Answer 3

There's probably something wrong with your bash configuration. Make sure you set the PATH so that it contains the directory that brew is in. You may have it set in your ~/.profile but make sure it's also set in your ~/.bashrc. Alternatively, you could set it in your crontab in the same way you set MAILTO

Answer 4

Personally the way I handle this is:

• Download CronniX (it's discontinued but still works, e.g. brew cask install cronnix)

• Setup the job within the UI via /usr/local/bin/brew update to run every hour.

Let it tick over in the background!