sample code to add support for --login-path parameter as an alternative to --user and --password parameters, and to add some logic to check for conflicting parameter(s):
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Usage: ./check_mysql_slavestatus.sh (-o file|(-H dbhost [-P port]|-S socket) (-u dbuser -p dbpass|-l loginpath)) [-s connection] [-w integer] [-c integer] [-m integer]

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help="\ncheck_mysql_slavestatus.sh (c) 2008-2019 GNU GPLv2 licence
Usage: $0 (-o file|(-H dbhost [-P port]|-S socket) (-u username -p password|-l loginpath)) [-s connection] [-w integer] [-c integer] [-m]\n
Options:\n-o Path to option file containing connection settings (e.g. /home/nagios/.my.cnf). Note: If this option is used, -H, -u, -p, -l parameters will become optional\n-H Hostname or IP of slave server\n-P MySQL Port of slave server (optional, defaults to 3306)\n-u Username of DB-user\n-p Password of DB-user\n-l Login Path (used instead of Username and Password)\n-S database socket\n-s Connection name (optional, with multi-source replication)\n-w Replication delay in seconds for Warning status (optional)\n-c Replication delay in seconds for Critical status (optional)\n-m Threshold in seconds since when replication did not move (compares the slaves log position)\n
Attention: The DB-user you type in must have CLIENT REPLICATION rights on the DB-server. Example:\n\tGRANT REPLICATION CLIENT on . TO 'nagios'@'%' IDENTIFIED BY 'secret';"
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while getopts "H:P:u:p:S:s:w:c:o:m:l:h" Input;
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l) loginpath_p="y";loginpath="--login-path=${OPTARG}";;
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Check whether all required arguments were passed in (either option file or full connection settings)

if [[ -z "${optfile}" && -z "${host}" && -z "${socket}" && -z "${loginpath}" ]]; then
echo -e "Missing required parameter(s)"; exit ${STATE_UNKNOWN}
elif [[ -z "${optfile}" && ((-z "${host}" && -z "${socket}") || (-z "${loginpath}" && (-z "${user}" || -z "${password}"))) ]]; then
echo -e "Missing required parameter(s)"; exit ${STATE_UNKNOWN}
elif [[ -z "${optfile}" && (-n "${host}" && -n "${socket}") ]]; then
echo -e "Conflicting parameter(s)"; exit ${STATE_UNKNOWN}
elif [[ -z "${optfile}" && (-n "${loginpath}" && -n "${user}") ]]; then
echo -e "Conflicting parameter(s)"; exit ${STATE_UNKNOWN}
elif [[ -z "${optfile}" && (-n "${loginpath}" && -n "${password}") ]]; then
echo -e "Conflicting parameter(s)"; exit ${STATE_UNKNOWN}
fi
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Connect to the DB server and store output in vars

if [[ -n $loginpath ]]; then
if [[ -n $socket ]]; then
ConnectionResult=$(mysql ${loginpath} ${optfile} ${socket} -e "show slave ${connection} status\G" 2>&1)
else
ConnectionResult=$(mysql ${loginpath} ${optfile} ${host} ${port} -e "show slave ${connection} status\G" 2>&1)
fi
else
if [[ -n $socket ]]; then
ConnectionResult=$(mysql ${optfile} ${socket} ${user} -e "show slave ${connection} status\G" 2>&1)
else
ConnectionResult=$(mysql ${optfile} ${host} ${port} ${user} -e "show slave ${connection} status\G" 2>&1)
fi
fi
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from check_mysql_slavestatus.