Bash: echo the arrow keys

rob_L · 08-12-2010, 07:37 AM

Is it possible to echo the arrow keys (up, down, left, right) in bash?
I know echo -e \033 echos escape but what about arrows?

Thank you.

tredegar · 08-12-2010, 11:07 AM

ANSI Escape sequences may be what you are looking for.

konsolebox · 08-12-2010, 11:21 AM

you might find these variables helpful

Code:

KEYS_ESC=$'\e'
KEYS_F1=$'\e'[[A
KEYS_F2=$'\e'[[B
KEYS_F3=$'\e'[[C
KEYS_F4=$'\e'[[D
KEYS_F5=$'\e'[[E
KEYS_F6=$'\e'[17~
KEYS_F7=$'\e'[18~
KEYS_F8=$'\e'[19~
KEYS_F9=$'\e'[20~
KEYS_F10=$'\e'[21~
KEYS_F11=$'\e'[22~
KEYS_F12=$'\e'[23~
KEYS_HOME=$'\e'[1~
KEYS_HOME2=$'\e'[H
KEYS_INSERT=$'\e'[2~
KEYS_DELETE=$'\e'[3~
KEYS_END=$'\e'[4~
KEYS_END2=$'\e'[F
KEYS_PAGEUP=$'\e'[5~
KEYS_PAGEDOWN=$'\e'[6~
KEYS_UP=$'\e'[A
KEYS_DOWN=$'\e'[B
KEYS_RIGHT=$'\e'[C
KEYS_LEFT=$'\e'[D
KEYS_NUMPADUNKNOWN=$'\e'[G

rob_L · 08-12-2010, 08:03 PM

Thanks all.

Konsolebox: how do I echo them? for example would echoing an arrow down be;
echo -en $'\e'[B

konsolebox · 08-12-2010, 08:19 PM

Those values do not represent a character. They merely are the generated sequence of characters when you press a special key on a terminal. For example if you cast read on a terminal like this:

Code:

read -t 1 REPLY

Once you press a key you'll notice that the output will be something like '<escape char>[B'.
If you echo the value of REPLY, the output will just be the same:

Code:

echo -n "$REPLY"

You'll find that it will just be similar to the echo you're after:

Code:

echo -n $'\e'\[B

If you really want to produce the up or down arrow character you should do this:

Code:

echo -n $'\030'  # up arrow key
echo -n $'\031'  # down arrow key

The characters that are shown might also depend on the terminal you have.

Reference: http://classicteck.com/maxdev/ascii.html