An experienced person will show you how to develop a professional and standardized MySQL startup script

#!/bin/bash
# chkconfig: 2345 64 36 #Configure system auto-start# description: A very fast and reliable SQL database engine.
##############################################################
# File Name: mysqld
# Version: V1.0
# Author: oldboy
# Organization: www.oldboyedu.com
# Created Time : 2018-06-05 08:58:19
##############################################################
#Introduce the system function library. /etc/init.d/functions

#Basic path definition basedir='/application/mysql'
bindir='/application/mysql/bin'
lockdir='/var/lock/subsys'                    
lock_file_path="$lockdir/mysql"
mysqld_pid_file_path='$basedir/data/`uname -n`.pid'

#Success prompt function log_success_msg(){
  #action is a special prompt function, $@ is all parameters.
  action "SUCCESS! $@" /bin/true
}
#Failure prompt function log_failure_msg(){
  action "ERROR! $@" /bin/false
 }
 
#mysql start function start(){
  echo $"Starting MySQL"
  #Test whether mysqld_safe is executable if test -x $bindir/mysqld_safe
  then
    #Background execution starts mysql command $bindir/mysqld_safe &>/dev/null &
    #Get the return value retval=$?
    # Check if the return value is 0
    if [ $retval -eq 0 ]
    then
      #Call the success prompt function.
      log_success_msg "mysql Startup"
      if test -w "$lockdir" #Judge whether the lock directory is writable.
      then
        touch "$lock_file_path" #Create a lock file.
      fi
      return $retval #Giving a return value is a professional gesture.
    else
      log_failure_msg "MySQL Startup" #Prompt of failed function call.
      return $retval
    fi
  else
    log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)"
  fi
}
#Stop the MySQL function.
stop(){
  #Judge whether the mysql pid file size is 0.
  if test -s "$mysqld_pid_file_path"
  then
    #Read pidfile
    mysqld_pid=`cat "$mysqld_pid_file_path"`
    #Judge whether the process corresponding to mysql pid exists.
    if (kill -0 $mysqld_pid 2>/dev/null)
    then
      echo $"Shutting down MySQL"
      kill $mysqld_pid #Stop the MySQL command.
      retval=$?
      if [ $retval -eq 0 ]
      then
        log_success_msg "MySQL Stop" #Call the stop success function.
        if test -f "$lock_file_path"
        then
          rm -f "$lock_file_path" #Delete the lock file.
        fi
        return $retval
      else
        log_failure_msg "MySQL Stop."
        return $retval
      fi
    else
      log_failure_msg "MySQL server process mysqld_pid is not running!"
      rm "$mysqld_pid_file_path"
    fi 
  else
    log_failure_msg "MySQL server PID file is null or does not exist!"
  fi
}
#Receive the passed parameters and execute the corresponding function.
case "$1" in
  start)
    start
    retval=$?
    ;;
  stop)
    stop
    retval=$?
    ;;
  restart)
    stop
    sleep 2 #This is very important, take a rest.
    start
    retval=$?
    ;;
  *)
    echo $"Usage:$0 {start|stop|restart}"
    exit 2
esac
exit $retval #After executing the script, it is more professional to have a return value.