Managing Oracle database single instance listener from SystemD (properly)

get_listener_pid.sh

#!/bin/bash

# This scripts parses the output from "lsnrctl show pid" and prints it either to screen to file
# Intended for "small" deployments where listener is started from RDBMS_HOME via systemd (not GI!)
# In unit file refferred as /home/oracle/bin/get_listener_pid.sh
# 2020 Ilmar Kerm

if [ -z "$ORACLE_HOME" ]; then
    echo "ORACLE_HOME environment variable is missing"
    exit 1
fi
if [ -z "$TNS_ADMIN" ]; then
    echo "TNS_ADMIN environment variable is missing"
    exit 1
fi

$ORACLE_HOME/bin/lsnrctl show pid > /tmp/lsnrctl_show_pid.out

# If lsnrctl returned an error
# Remove pidfile and display an error
if [ $? -ne 0 ]; then
    [[ -n "$1" && -f "$1" ]] && rm "$1"
    echo "*** lsnrctl show pid returned an error"
    cat /tmp/lsnrctl_show_pid.out
    exit 1
fi

# Get the actual pid from output
listenerpid=$(grep PID= /tmp/lsnrctl_show_pid.out | awk -F"[()]" '{print $2}')

# Write pid to file or standard output
if [ -n "$1" ]; then
    echo "$listenerpid" > "$1"
else
    echo "$listenerpid"
fi

oracle-listener.service

# Place under /etc/systemd/system/oracle-listener.service
[Unit]
Description=The Oracle Database Listener
After=syslog.target network.target

[Service]
LimitNPROC=131072
LimitNOFILE=131072
LimitMEMLOCK=5525094
Type=forking
User=oracle
Group=oinstall
Restart=on-abnormal
RestartSec=5
Environment=ORACLE_HOME=/u01/app/oracle/product/19-clean-19081
Environment=LD_LIBRARY_PATH=/u01/app/oracle/product/19-clean-19081/lib
Environment=ORACLE_BASE=/u01/app/oracle
Environment=TNS_ADMIN=/u01/app/oracle/network
WorkingDirectory=/tmp
ExecStart=/bin/bash -c '/u01/app/oracle/product/19-clean-19081/bin/lsnrctl start && /home/oracle/bin/get_listener_pid.sh /u01/app/oracle/network/listener.pid'
ExecStop=/bin/bash -c '/u01/app/oracle/product/19-clean-19081/bin/lsnrctl stop && rm /u01/app/oracle/network/listener.pid'
PIDFile=/u01/app/oracle/network/listener.pid

[Install]
WantedBy=multi-user.target