Shell Programming and Scripting

#!/bin/bash
echo $(date)  ": executing switch hdmi... $1 with pid: $$" >> /home/pi/temp_rc

time_delay=5

# create temp file with the same name but extension .pid to store process ID of this running script
FILE=$0.pid

# if file doesnt exist then create it and store current pid. this should happen only for the first time of script executing
if [ ! -e $FILE ]; then
   echo "creating new temp file $FILE and storing current pid: $$" >> /home/pi/temp_rc
   echo $$ > $FILE
fi

# kill previous process to restart timer
if [ "$1" = "restart_timer" ]; then
   echo "restarting timer. killing pid $(cat $FILE) from file: $FILE" >> /home/pi/temp_rc
   sudo kill -9 $(cat  $FILE)
   exit 0
fi

# store pid of current process
echo "storing current pid: $$" >> /home/pi/temp_rc
echo $$ > $FILE


# switch hdmi ports
switch_hdmi(){
   echo "switch to hdmi port $1" >> /home/pi/temp_rc
}


if [ "$1" = "rc1_stop" ]; then
   echo $(date) ': switch hdmi to rc1 stop' >> /home/pi/temp_rc
   switch_hdmi 1
   time_delay=0 # stop timer

elif [ "$1" = "rc1_restart" ]; then
   echo $(date) ': switch hdmi to rc1 restart' >> /home/pi/temp_rc
   switch_hdmi 1

fi

until [ $time_delay -eq 0 ]; do
  sleep 1
  echo "timer coutdown: $time_delay" >> /home/pi/temp_rc
  time_delay=$((time_delay-1))

  # execute if time expired
  if [ $time_delay -le 0 ]; then
     echo "timer expired" >> /home/pi/temp_rc
     switch_hdmi 3
     exit
  fi
done
exit 0

sudo sh /home/pi/switch_hdmi.sh restart_timer; sudo sh /home/pi/switch_hdmi.sh rc1_restart &

#!/bin/bash
# https://www.unix.com/shell-programming-and-scripting/247133-exit-while-loop-execute-script-2.html
# Fun rewrite by sea
#
#	Variables
#
	TASK="$1"			# Set argument as TASK
	ME=${0##*/}			# basename
	LOG=$HOME/$ME.log		# Logfile, to see what it does. (used to be tmp_rc)
	TMR=$HOME/$ME.timervalue	# Contains the current value of the timer
	PORT=$HOME/$ME.port		# What is its default port?
	PID=$$				# PID of this execution of script
	TIMER_DELAY=5			# Default/Start value
	time_delay=$TIMER_DELAY		# Work-value
#
#	Functions
#
	doLog() { # "MESSAGE STRING"
	# Prints current date time username,
	# followed by the supplied "message string"
		echo "$(date +'%F %T') $USER -- $1" >> $LOG
	}
	switch_hdmi(){ # NUM
	# switch hdmi ports
	# 
		doLog "switch to hdmi port $1"
		echo $1 > $PORT		# This was probably your (missing) point		?
	}
#
#	Environment checks
#
	[ -e $LOG ] || ( touch $LOG ; doLog "Created logfile of $ME" )
	[ -e $TMR ] || ( touch $TMR ; echo $TIMER_DELAY > $TMR)
#
#	Argument handling
#
	doLog "executing switch hdmi... $1 with pid: $PID"
	case "$TASK" in
	restart_timer)	doLog "restarting timer. killing pid $PID"
			sudo kill -9 $PID		# kill previous (now its current anyway) process to restart timer?
			exit 0				# Is this still required/working	?
			;;
	rc1_stop)	doLog "Switch hdmi to rc1 stop"
			switch_hdmi 1
			echo 0 > $TMR 			# stop timer
			;;
	rc1_restart)	doLog "Switch hdmi to rc1 restart"
			switch_hdmi 1
			echo $TIMER_DELAY > $TMR 	# reset timer
			;;
	*)		doLog "Call with faulty args... What to do?"
			echo "Faulty arg supplied..."
			exit 1
	esac
#
#	Action / Timer
#
	until [ $time_delay -eq 0 ] ; do
		sleep 1 				# Actualy wait a second
		time_delay=$(cat $TMR)			# Read timer value from file, if there was a change
		doLog "timer coutdown: $time_delay"	# Prints re-read timer value to log
		time_delay=$((time_delay-1))		# Update timer value
		echo $time_delay > $TMR			# Update timer file
		if [ $time_delay -le 0 ]
		then	# Time is up
			doLog "timer expired"
			switch_hdmi 3
			exit $?
		fi
	done
	exit 0