Trap Ctrl+C no script

Aqui está como você pode capturar o CTRL+Cno script. Você não chama a ctrl_cfunção, pois ela será chamada quando você pressionar CTRL+ Cno teclado. Eu adicionei um exit 0para que ele saia do script depois que ele intercepte CTRL+Ce pare de fazer o loop pelo arquivo for .. loop.

cat ctrl_test.bsh 
#!/bin/bash

#Setup trap command, assign what to call and what is the trigger (SIGINT)
trap ctrl_c INT

#Function of what trap command calls    
function ctrl_c() {
    printf "\n** Trapped CTRL-C after $i seconds.\n"
    exit 0
}

#Rest of script to print counting numbers to screen will not break with CTRL+C due to trap
for ((i=1;i>0;i++))
do
    printf "\r$i"
    sleep 1
done

Exemplo:

terrance@terrance-ubuntu:~$ ./ctrl_test.bsh 
13^C
** Trapped CTRL-C after 13 seconds.
terrance@terrance-ubuntu:~$ 

No seu caso de script, você poderia fazer algo assim:

#TimerInTerminal.sh

#Trap Ctrl+C and re-enable suspend and hibernation modes
trap ctrl_c INT
function ctrl_c() {
    sudo systemctl unmask sleep.target suspend.target hibernate.target hybrid-sleep.target
    exit 0
}

# To prevent your Linux system from suspending or going into hibernation, you need to disable the following systemd targets:
# sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target

# To re-enable the suspend and hibernation modes, run the command:
# sudo systemctl unmask sleep.target suspend.target hibernate.target hybrid-sleep.target

soundfile="/usr/share/sounds/My_Sounds/Electronic_Chime.wav"
# Stop computer from sleeping while timer is running

# prevent your Linux system from suspending or going into hibernation
sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target

# This allows supend ?
#trap "echo marlin | sudo -S systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target" INT EXIT

if [ $# -eq 1 ]
then
    DURATION="$1"
else
    read -r -p "Timer for how many minutes?( for fractional, use decimal notation , 0.5==30s, 1.25==75s etc) : "  DURATION
    read -r -p "Enter text to display at the end of the timer : " n1
fi

DURATION=$(echo "$DURATION * 60 / 1" | bc) # lets us deal with fractional inputs

START=$(date +%s)   # only do this once (anchor's the time)

countdown () {
    NOW=$(date +%s)              # Get time now in seconds
    DIF=$((NOW - START))         # Compute diff in seconds
    ELAPSE=$((DURATION - DIF))   # Compute elapsed time in seconds
    MINS=$((ELAPSE / 60))        # Convert to minutes... (dumps remainder from division)
    SECS=$((ELAPSE - (MINS*60))) # ... and seconds
    #banner "$MINS:$SECS"
    echo "$MINS:$SECS"
    sleep "$1"
}

while true 
do
    clear
    
    countdown 0 # calc time remaining
    
    if [ $MINS -le 0 ]
    then
        # Blink screen

        while [ $SECS -gt 0 ]
        do
            
            clear # Flash on
            #setterm -term linux -back red -fore white 
            countdown 0.5

            clear # Flash off
            #setterm -term linux -default
            countdown 0.5

        done # End for loop
        
        setterm -term linux -default
        clear
        
        break   # time has expired lets get out of here
    
    else
        countdown 1 
    fi
done

echo $n1
amixer -D pulse sset Master 30% > /dev/null 2>&1
# Play a sound
cvlc --play-and-exit "$soundfile" > /dev/null 2>&1

# To re-enable the suspend and hibernation modes, run the command:
 echo marlin | sudo -S systemctl unmask sleep.target suspend.target hibernate.target hybrid-sleep.target