CODEWITHSUNDEEP
bash
Alichino
Alichino

Reputation: 1736

BASH: read input only once and do not continue reading until key is released

I have this short script:

until [[ $ACTION == "t"  ]]; do

read -sn1 ACTION

case $ACTION in

 e|E) printf "£\n";;

done

When I press "e", a pound sign is printed. When I press and hold "e", I get a continuous stream of "£", one under another.

Is there a way to do this: press and hold "e" resulting in only one "£" printed, until the "e" is released and pressed again?

And here is the catch: without the TIMEOUT "-t" switch in read

Please help :)

============= EDIT one day later ==============

The problem I want to solve is this: I can move a symbol on the screen using a combination of tput commands. When the TIMEOUT is set in the read command, two things can happen: either the TIMEOUT is big enough, and holding down a key does not move the symbol continuously - but then quick tapping on the key corrupts the screen; or if the TIMEOUT is small, quick tapping does not corrupt the screen, but holding down the key produces ALARM CLOCK interrupt. So, I don't want Bash to wait for input. I want it to read a pressed arrow key once, and that's it - user needs to release the key and press again to continue moving.

I have been using this function below, but it's producing all these problems:

ReadKey() {

# Wait for first char

if read -sN1 ACTION; then

  # Read rest of chars

  while read -sN1 -t 0.05 ; do

    ACTION+="${REPLY}"

  done

fi

}

and then

while Readkey; do

 case $ACTION in

 [case options follow]

Upvotes: 3

Views: 470

Answers (3)

Alichino
Alichino

Reputation: 1736

I have come to the conclusion that this is a Windows problem. I have run my game on Ubuntu and it works like a dream.

Upvotes: 1

Victor Henriquez
Victor Henriquez

Reputation: 1449

Maybe you can achieve your goal using stty, something like this should work for your scenario:

stty -echo -icanon time 1 min 0 ;

ACTION=''
until [[ $ACTION == "t"  ]]; do
  read ACTION
case $ACTION in
 e|E) printf "£\n";;
esac

done

stty sane;

I'm not sure if this will corrupt your screen when "quick tapping" is used, but if that is the case, provide details about such corruption and I'll try to help you.

Upvotes: 0

that other guy
that other guy

Reputation: 123510

You can use the DECARM extension on supported terminals to disable auto-repeat:

printf '\e[?8l'

To re-enable auto-repeat, use printf '\e[?8h'

Upvotes: 0

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