Difference between `brew services start mysql` and `mysql.server start`

Question

I installed MySQL using homebrew brew install mysql, and I noticed that MySQL can be managed with two different methods:

brew services start mysql

Answer 1

According to the help message of brew services, when you run

brew services start mysql

it installs and starts the service formula at login (or at boot if you run the command with sudo). It means you will have now a plist file in ~/Library/LaunchAgents (or in /Library/LaunchDaemons if you run the command with sudo). For mysql, the plist file is the following:

<?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>KeepAlive</key>
  <true/>
  <key>Label</key>
  <string>homebrew.mxcl.mysql</string>
  <key>ProgramArguments</key>
  <array>
    <string>/usr/local/opt/mysql/bin/mysqld_safe</string>
    <string>--bind-address=127.0.0.1</string>
    <string>--datadir=/usr/local/var/mysql</string>
  </array>
  <key>RunAtLoad</key>
  <true/>
  <key>WorkingDirectory</key>
  <string>/usr/local/var/mysql</string>
</dict>
</plist> 

it means that by default mysqld_safe is called with the --bind-address=127.0.0.1 and --datadir=/usr/local/var/mysql command line options.

when you run

mysql.server start

you directly execute the mysql script located in /usr/local/bin/mysql.server.

The main difference is that with the brew services version, you run mysqld_safe which, according to its man page:

adds some safety features such as restarting the server when an error occurs and logging runtime information to an error log file.