Keyboard input/Keypress check

From Rosetta Code
Task
Keyboard input/Keypress check
You are encouraged to solve this task according to the task description, using any language you may know.


Determine if a key has been pressed and store this in a variable.

If no key has been pressed, the program should continue without waiting.

Ada[edit]

Ch : Character;
Available : Boolean;
 
Ada.Text_IO.Get_Immediate (Ch, Available);

If key was pressed, Available is set to True and Ch contains the value. If not, Available is set to False.

ARM Assembly[edit]

Works with: as version Raspberry Pi
 
 
/* Programme assembleur ARM Raspberry */
/* Assembleur ARM Raspberry : Vincent Leboulou */
/* Blog : http://assembleurarmpi.blogspot.fr/ */
/* modèle B 512MO */
 
/************************************/
/* Constantes */
/************************************/
.equ STDIN, 0 @ Linux input console
.equ STDOUT, 1 @ Linux output console
.equ EXIT, 1 @ Linux syscall
.equ READ, 3 @ Linux syscall
.equ WRITE, 4 @ Linux syscall
.equ IOCTL, 0x36 @ Linux syscall
.equ SIGACTION, 0x43 @ Linux syscall
.equ SYSPOLL, 0xA8 @ Linux syscall
 
.equ TCGETS, 0x5401
.equ TCSETS, 0x5402
.equ ICANON, 2
.equ ECHO, 10
.equ POLLIN, 1
 
.equ SIGINT, 2 @ Issued if the user sends an interrupt signal (Ctrl + C)
.equ SIGQUIT, 3 @ Issued if the user sends a quit signal (Ctrl + D)
.equ SIGTERM, 15 @ Software termination signal (sent by kill by default)
.equ SIGTTOU, 22 @
 
.equ TAILLEBUFFER, 10
 
 
/*******************************************/
/* Structures */
/********************************************/
/* structure termios see doc linux*/
.struct 0
term_c_iflag: @ input modes
.struct term_c_iflag + 4
term_c_oflag: @ output modes
.struct term_c_oflag + 4
term_c_cflag: @ control modes
.struct term_c_cflag + 4
term_c_lflag: @ local modes
.struct term_c_lflag + 4
term_c_cc: @ special characters
.struct term_c_cc + 20 @ see length if necessary
term_fin:
 
/* structure sigaction see doc linux */
.struct 0
sa_handler:
.struct sa_handler + 4
sa_mask:
.struct sa_mask + 4
sa_flags:
.struct sa_flags + 4
sa_sigaction:
.struct sa_sigaction + 4
sa_fin:
 
/* structure poll see doc linux */
.struct 0
poll_fd: @ File Descriptor
.struct poll_fd + 4
poll_events: @ events mask
.struct poll_events + 4
poll_revents: @ events returned
.struct poll_revents + 4
poll_fin:
 
/*********************************/
/* Initialized data */
/*********************************/
.data
szMessPgmOk: .asciz "End program OK.\n"
szMessErreur: .asciz "Error detected.\n"
sMessResult: .ascii "Value  : "
sMessValeur: .fill 11, 1, ' ' @ size => 11
szCarriageReturn: .asciz "\n"
/*************************************************/
szMessErr: .ascii "Error code hexa : "
sHexa: .space 9,' '
.ascii " decimal : "
sDeci: .space 15,' '
.asciz "\n"
szMessKey: .ascii "Value key ==>"
sHexaKey: .space 9,' '
.asciz "\n"
.align 4
 
/*********************************/
/* UnInitialized data */
/*********************************/
.bss
.align 4
iEnd: .skip 4 @ 0 loop 1 = end loop
iTouche: .skip 4 @ value key pressed
stOldtio: .skip term_fin @ old terminal state
stCurtio: .skip term_fin @ current terminal state
stSigAction: .skip sa_fin @ area signal structure
stSigAction1: .skip sa_fin
stPoll1: .skip poll_fin @ area poll structure
stPoll2: .skip poll_fin
 
/*********************************/
/* code section */
/*********************************/
.text
.global main
main: @ entry of program
 
/* read terminal state */
mov r0,#STDIN @ input console
mov r1,#TCGETS
ldr r2,iAdrstOldtio
mov r7, #IOCTL @ call system Linux
svc #0
cmp r0,#0 @ error ?
beq 1f
ldr r1,iAdrszMessErreur @ error message
bl displayError
b 100f
1:
adr r0,sighandler @ adresse routine traitement signal
ldr r1,iAdrstSigAction @ adresse structure sigaction
str r0,[r1,#sa_handler] @ maj handler
mov r0,#SIGINT @ signal type
ldr r1,iAdrstSigAction
mov r2,#0 @ NULL
mov r7, #SIGACTION @ call system
svc #0
cmp r0,#0 @ error ?
bne 98f
mov r0,#SIGQUIT
ldr r1,iAdrstSigAction
mov r2,#0 @ NULL
mov r7, #SIGACTION @ call system
svc #0
cmp r0,#0 @ error ?
bne 98f
mov r0,#SIGTERM
ldr r1,iAdrstSigAction
mov r2,#0 @ NULL
mov r7, #SIGACTION @ appel systeme
svc #0
cmp r0,#0
bne 98f
@
adr r0,iAdrSIG_IGN @ address signal igonre function
ldr r1,iAdrstSigAction1
str r0,[r1,#sa_handler]
mov r0,#SIGTTOU @invalidate other process signal
ldr r1,iAdrstSigAction1
mov r2,#0 @ NULL
mov r7,#SIGACTION @ call system
svc #0
cmp r0,#0
bne 98f
@
/* read terminal current state */
mov r0,#STDIN
mov r1,#TCGETS
ldr r2,iAdrstCurtio @ address current termio
mov r7,#IOCTL @ call systeme
svc #0
cmp r0,#0 @ error ?
bne 98f
mov r2,#ICANON | ECHO @ no key pressed echo on display
mvn r2,r2 @ and one key
ldr r1,iAdrstCurtio
ldr r3,[r1,#term_c_lflag]
and r3,r2 @ add flags
str r3,[r1,#term_c_lflag] @ and store
mov r0,#STDIN @ maj terminal current state
mov r1,#TCSETS
ldr r2,iAdrstCurtio
mov r7, #IOCTL @ call system
svc #0
cmp r0,#0
bne 98f
@
2: @ loop waiting key
ldr r0,iAdriEnd @ if signal ctrl-c -> end
ldr r0,[r0]
cmp r0,#0
bne 3f
ldr r0,iAdrstPoll1 @ address structure poll
mov r1,#STDIN
str r1,[r0,#poll_fd] @ maj FD
mov r1,#POLLIN @ action code
str r1,[r0,#poll_events]
mov r1,#1 @ items number structure poll
mov r2,#0 @ timeout = 0
mov r7,#SYSPOLL @ call system POLL
svc #0
cmp r0,#0 @ key pressed ?
ble 2b @ no key pressed -> loop
@ read key
mov r0,#STDIN @ File Descriptor
ldr r1,iAdriTouche @ buffer address
mov r2,#TAILLEBUFFER @ buffer size
mov r7,#READ @ read key
svc #0
cmp r0,#0 @ error ?
ble 98f
ldr r2,iAdriTouche @ key address
ldr r0,[r2]
ldr r1,iAdrsHexaKey
bl conversion16 @ conversion hexa
ldr r0,iAdrszMessKey @ display key value in hexa
bl affichageMess
ldrb r0,[r2] @ key value
cmp r0,#113 @ saisie q ?
beq 3f
cmp r0,#81 @ saisie Q ?
beq 3f
mov r0,#0
str r0,[r2] @ raz key area
b 2b @ loop
 
3: @ end loop display Ok message
ldr r0,iAdrszMessPgmOk
bl affichageMess
b 99f
98: @ error display
ldr r1,iAdrszMessErreur @ error message
bl displayError
99: @ end then restaur begin state terminal
mov r0,#STDIN
mov r1,#TCSETS
ldr r2,iAdrstOldtio
mov r7,#IOCTL @ call system
svc #0
cmp r0,#0
beq 100f
ldr r1,iAdrszMessErreur @ error message
bl displayError
 
100: @ standard end of the program
mov r0, #0 @ return code
mov r7, #EXIT @ request to exit program
svc #0 @ perform the system call
 
iAdrsMessValeur: .int sMessValeur
iAdrszMessErreur: .int szMessErreur
iAdrszCarriageReturn: .int szCarriageReturn
iAdrstOldtio: .int stOldtio
iAdrstCurtio: .int stCurtio
iAdrstSigAction: .int stSigAction
iAdrstSigAction1: .int stSigAction1
iAdrszMessPgmOk: .int szMessPgmOk
iAdrsMessResult: .int sMessResult
iAdrSIG_IGN: .int 1
iAdriEnd: .int iEnd
iAdrstPoll1: .int stPoll1
iAdriTouche: .int iTouche
iAdrszMessKey: .int szMessKey
iAdrsHexaKey: .int sHexaKey
/******************************************************************/
/* traitement du signal */
/******************************************************************/
/* r0 contains */
sighandler:
push {r0,r1}
ldr r0,iAdriEnd
mov r1,#1 @ maj zone end
str r1,[r0]
pop {r0,r1}
bx lr
/***************************************************/
/* display error message */
/***************************************************/
/* r0 contains error code r1 : message address */
displayError:
push {r0-r2,lr} @ save registers
mov r2,r0 @ save error code
mov r0,r1
bl affichageMess
mov r0,r2 @ error code
ldr r1,iAdrsHexa
bl conversion16 @ conversion hexa
mov r0,r2 @ error code
ldr r1,iAdrsDeci @ result address
bl conversion10 @ conversion decimale
ldr r0,iAdrszMessErr @ display error message
bl affichageMess
100:
pop {r0-r2,lr} @ restaur registers
bx lr @ return
iAdrszMessErr: .int szMessErr
iAdrsHexa: .int sHexa
iAdrsDeci: .int sDeci
/******************************************************************/
/* display text with size calculation */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
push {r0,r1,r2,r7,lr} @ save registres
mov r2,#0 @ counter length
1: @ loop length calculation
ldrb r1,[r0,r2] @ read octet start position + index
cmp r1,#0 @ if 0 its over
addne r2,r2,#1 @ else add 1 in the length
bne 1b @ and loop
@ so here r2 contains the length of the message
mov r1,r0 @ address message in r1
mov r0,#STDOUT @ code to write to the standard output Linux
mov r7, #WRITE @ code call system "write"
svc #0 @ call systeme
pop {r0,r1,r2,r7,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* Converting a register to a decimal unsigned */
/******************************************************************/
/* r0 contains value and r1 address area */
/* r0 return size of result (no zero final in area) */
/* area size => 11 bytes */
.equ LGZONECAL, 10
conversion10:
push {r1-r4,lr} @ save registers
mov r3,r1
mov r2,#LGZONECAL
 
1: @ start loop
bl divisionpar10U @ unsigned r0 <- dividende. quotient ->r0 reste -> r1
add r1,#48 @ digit
strb r1,[r3,r2] @ store digit on area
cmp r0,#0 @ stop if quotient = 0
subne r2,#1 @ else previous position
bne 1b @ and loop
@ and move digit from left of area
mov r4,#0
2:
ldrb r1,[r3,r2]
strb r1,[r3,r4]
add r2,#1
add r4,#1
cmp r2,#LGZONECAL
ble 2b
@ and move spaces in end on area
mov r0,r4 @ result length
mov r1,#' ' @ space
3:
strb r1,[r3,r4] @ store space in area
add r4,#1 @ next position
cmp r4,#LGZONECAL
ble 3b @ loop if r4 <= area size
 
100:
pop {r1-r4,lr} @ restaur registres
bx lr @return
 
/***************************************************/
/* division par 10 unsigned */
/***************************************************/
/* r0 dividende */
/* r0 quotient */
/* r1 remainder */
divisionpar10U:
push {r2,r3,r4, lr}
mov r4,r0 @ save value
//mov r3,#0xCCCD @ r3 <- magic_number lower raspberry 3
//movt r3,#0xCCCC @ r3 <- magic_number higter raspberry 3
ldr r3,iMagicNumber @ r3 <- magic_number raspberry 1 2
umull r1, r2, r3, r0 @ r1<- Lower32Bits(r1*r0) r2<- Upper32Bits(r1*r0)
mov r0, r2, LSR #3 @ r2 <- r2 >> shift 3
add r2,r0,r0, lsl #2 @ r2 <- r0 * 5
sub r1,r4,r2, lsl #1 @ r1 <- r4 - (r2 * 2) = r4 - (r0 * 10)
pop {r2,r3,r4,lr}
bx lr @ leave function
iMagicNumber: .int 0xCCCCCCCD
/******************************************************************/
/* Converting a register to hexadecimal */
/******************************************************************/
/* r0 contains value and r1 address area */
conversion16:
push {r1-r4,lr} @ save registers
mov r2,#28 @ start bit position
mov r4,#0xF0000000 @ mask
mov r3,r0 @ save entry value
1: @ start loop
and r0,r3,r4 @value register and mask
lsr r0,r2 @ move right
cmp r0,#10 @ compare value
addlt r0,#48 @ <10 ->digit
addge r0,#55 @ >10 ->letter A-F
strb r0,[r1],#1 @ store digit on area and + 1 in area address
lsr r4,#4 @ shift mask 4 positions
subs r2,#4 @ counter bits - 4 <= zero  ?
bge 1b @ no -> loop
 
100:
pop {r1-r4,lr} @ restaur registers
bx lr @return
 
 

AutoHotkey[edit]

Waits for the user to type a string (not supported on Windows 9x: it does nothing).

; Input [, OutputVar, Options, EndKeys, MatchList]
Input, KeyPressed, L1 T2 ; Length = 1, Timeout = 2 seconds


Checks if a keyboard key or mouse/joystick button is down or up. Also retrieves joystick status.

; GetKeyState, OutputVar, KeyName [, Mode]
GetKeyState, State, RButton ; Right mouse button.


Function version of GetKeyState.

; KeyIsDown := GetKeyState("KeyName" [, "Mode"])
State := GetKeyState("RButton", "P") ; Right mouse button. P = Physical state.

Axe[edit]

Note that while the syntax for getting the most recent keypress is identical to TI-83 BASIC, the keycodes themselves are different.

getKey→K

BASIC[edit]

BaCon[edit]

 
PRINT "Press <escape> to exit now..."
key = GETKEY
IF key = 27 THEN
END
END IF

Applesoft BASIC[edit]

K = PEEK(-16384) : IF K > 127 THEN POKE -16368,0 : K$ = CHR$(K)

IS-BASIC[edit]

100 LET K$=INKEY$

or

100 GET K$

ZX Spectrum Basic[edit]

Works with: Locomotive Basic
10 REM k$ will be empty, if no key has been pressed
20 LET k$ = INKEY$

BBC BASIC[edit]

      key$ = INKEY$(0)

If there was no keypress an empty string is returned. Alternatively a numeric key-code may be obtained; if there was no keypress -1 is returned:

      key% = INKEY(0)

C[edit]

For POSIX systems. Ctrl-C to stop:
#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <fcntl.h>
 
void set_mode(int want_key)
{
static struct termios old, new;
if (!want_key) {
tcsetattr(STDIN_FILENO, TCSANOW, &old);
return;
}
 
tcgetattr(STDIN_FILENO, &old);
new = old;
new.c_lflag &= ~(ICANON | ECHO);
tcsetattr(STDIN_FILENO, TCSANOW, &new);
}
 
int get_key()
{
int c = 0;
struct timeval tv;
fd_set fs;
tv.tv_usec = tv.tv_sec = 0;
 
FD_ZERO(&fs);
FD_SET(STDIN_FILENO, &fs);
select(STDIN_FILENO + 1, &fs, 0, 0, &tv);
 
if (FD_ISSET(STDIN_FILENO, &fs)) {
c = getchar();
set_mode(0);
}
return c;
}
 
int main()
{
int c;
while(1) {
set_mode(1);
while (!(c = get_key())) usleep(10000);
printf("key %d\n", c);
}
}

C#[edit]

string chr = string.Empty;
if(Console.KeyAvailable)
chr = Console.ReadKey().Key.ToString();

Clojure[edit]

Library: jline

Note: If you run it with Leiningen, use the special trampoline run to prevent issues:

$ lein trampoline run
 
(ns keypress.core
(:import jline.Terminal)
(:gen-class))
 
(def keypress (future (.readCharacter (Terminal/getTerminal) System/in)))
 
(defn prompt []
(println "Awaiting char...\n")
(Thread/sleep 2000)
(if-not (realized? keypress)
(recur)
(println "key: " (char @keypress))))
 
(defn -main [& args]
(prompt)
(shutdown-agents))
 

D[edit]

extern (C) {
void _STI_conio();
void _STD_conio();
int kbhit();
int getch();
}
 
void main() {
_STI_conio();
 
char c;
if (kbhit())
c = cast(char)getch();
 
_STD_conio();
}

Delphi[edit]

This is valid for a GUI application!

unit Unit1;
 
interface
 
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;
 
type
TForm1 = class(TForm)
procedure FormKeyPress(Sender: TObject; var Key: Char);
private
SavedPressedKey: Char;
end;
 
var
Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.FormKeyPress(Sender: TObject; var Key: Char);
begin
SavedPressedKey := Key;
end;
 
end.

Elena[edit]

Translation of: C#

ELENA 4.x :

import extensions;
 
public program()
{
auto chr := emptyString;
if (console.KeyAvailable)
{
chr := console.readChar()
}
}

ERRE[edit]

 
!$KEY
.........
GET(K$)
.........
 

Note: If no key was pressed K$ is empty string "".

Euphoria[edit]

integer key
key = get_key() -- if key was not pressed get_key() returns -1


F#[edit]

Translation of: C#
open System;
 
let chr = if Console.KeyAvailable then Console.ReadKey().Key.ToString() else String.Empty

Forth[edit]

variable last-key
: check key? if key last-key ! then ;

FreeBASIC[edit]

' FB 1.05.0 Win64
 
Dim k As String
Do
k = Inkey
Loop Until k <> ""
 
If Len(k) = 1 Then
Print "The key pressed was "; k; " (ascii "; Asc(k); ")"
Else
Print "An extended key was pressed"
End If
 
Sleep

Sample input/output

Output:
The key pressed was A (ascii 65)

Gambas[edit]

Public Sub Form_KeyPress()
 
'Requires a TextBox or similar on the Form to work
Print Key.Text;
 
End

Output:

Hello world!

Go[edit]

Library: Curses
package main
 
import (
"log"
"time"
 
gc "code.google.com/p/goncurses"
)
 
func main() {
s, err := gc.Init()
if err != nil {
log.Fatal("init:", err)
}
defer gc.End()
gc.Cursor(0)
s.Move(20, 0)
s.Print("Key check in ")
for i := 3; i >= 1; i-- {
s.MovePrint(20, 13, i)
s.Refresh()
time.Sleep(500 * time.Millisecond)
}
s.Println()
gc.Echo(false)
 
// task requirement next two lines
s.Timeout(0)
k := s.GetChar()
 
if k == 0 {
s.Println("No key pressed")
} else {
s.Println("You pressed", gc.KeyString(k))
}
s.Refresh()
s.Timeout(-1)
gc.FlushInput()
gc.Cursor(1)
s.GetChar()
}

Haskell[edit]

import Control.Concurrent
import Control.Monad
import Data.Maybe
import System.IO
 
main = do
c <- newEmptyMVar
hSetBuffering stdin NoBuffering
forkIO $ do
a <- getChar
putMVar c a
putStrLn $ "\nChar '" ++ [a] ++
"' read and stored in MVar"
wait c
where wait c = do
a <- tryTakeMVar c
if isJust a then return ()
else putStrLn "Awaiting char.." >>
threadDelay 500000 >> wait c
 

Output:

Awaiting char..
Awaiting char..
Awaiting char..
d
Char 'd' read and stored in MVar

Icon and Unicon[edit]

procedure main()
delay(1000) # give user a chance to input
if kbhit() then # test for input
write("You entered ",x := getch()) # read w/o echo
else # use getche for echo
write("No input waiting")
end

Java[edit]

Works with: java version 8
import java.awt.event.*;
import javax.swing.*;
 
public class Test extends JFrame {
 
Test() {
addKeyListener(new KeyAdapter() {
@Override
public void keyPressed(KeyEvent e) {
int keyCode = e.getKeyCode();
System.out.println(keyCode);
}
});
}
 
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
Test f = new Test();
f.setFocusable(true);
f.setVisible(true);
});
}
}

Julia[edit]

using Gtk
 
function keypresswindow()
tcount = 0
txt = "Press a Key"
win = GtkWindow("Keypress Test", 500, 30) |> (GtkFrame() |> ((vbox = GtkBox(:v)) |> (lab = GtkLabel(txt))))
function keycall(w, event)
ch = Char(event.keyval)
tcount += 1
set_gtk_property!(lab, :label, "You have typed $tcount chars including $ch this time")
end
signal_connect(keycall, win, "key-press-event")
 
cond = Condition()
endit(w) = notify(cond)
signal_connect(endit, win, :destroy)
showall(win)
wait(cond)
end
 
keypresswindow()
 


Kotlin[edit]

Translated from the Java entry but then modified so as to quit the program when the Enter key is pressed:

// version 1.1
 
import java.awt.event.KeyAdapter
import java.awt.event.KeyEvent
import javax.swing.JFrame
import javax.swing.SwingUtilities
 
class Test : JFrame() {
init {
println("Press any key to see its code or 'enter' to quit\n")
addKeyListener(object : KeyAdapter() {
override fun keyPressed(e: KeyEvent) {
if (e.keyCode == KeyEvent.VK_ENTER) {
isVisible = false
dispose()
System.exit(0)
}
else
println(e.keyCode)
}
})
}
}
 
fun main(args: Array<String>) {
SwingUtilities.invokeLater {
val f = Test()
f.isFocusable = true
f.isVisible = true
}
}

Lingo[edit]

-- in some movie script
 
-- event handler
on keyDown
pressedKey = _key.key
put "A key was pressed:" && pressedKey
end

LiveCode[edit]

LiveCode is message based and all stacks, cards and gui controls can have their own keyup/down message handler. You would ordinarily add the relevant event handler to do something when a key is pressed. There is a function however that can be executed that returns a list of keycodes for the keys currently pressed, called keysDown.

Example

repeat 100 times
-- exit loop if "." or the escapeKey is pressed
if 46 is in the keysDown or 65307 is in the keysdown then
answer "exiting"
exit repeat
else
-- do stuff
wait 200 millisec
end if
end repeat

Example of event message handling (at stack, card or control level)

on keyDown k
-- do stuff, keycode is held in k
if k is not 46 then pass keyDown // will be trapped if "." is pressed, others will be passed on through the message path
end keyDown

You can substitute keyUp, rawKeyUp, rawKeyDown for keyUp in above. The non-raw handlers do not readily cope with special key presses, and they have their own handlers such as escapeKey, enterKey, altkey, commandKey... look up "key" in the LC dictionary to find more.

[edit]

if key? [make "keyhit readchar]

M2000 Interpreter[edit]

Without delay[edit]

 
k$=inkey$
 

Using delay[edit]

 
K$=""
If Inkey(2000)<>-1 then k$=Key$
Print k$
 

Check specific key[edit]

 
k$=""
If keypress(32) then k$=" "
 

Oforth[edit]

import: console
 
: checkKey
| key |
System.Console receiveTimeout(2000000) ->key // Wait a key pressed for 2 seconds
key ifNotNull: [ System.Out "Key pressed : " << key << cr ]
"Done" println ;

Other options :

System.Console receive ->key                 // Wait until a key is pressed ( = receiveTimeout(null) )
System.Console receiveChar ->aChar // Wait until a character is pressed. All other keys are ignored
System.Console receiveTimeout(0) ->key // Check if a key is pressed and return immediatly

Perl[edit]

#!/usr/bin/perl
use strict;
use warnings;
use Term::ReadKey;
ReadMode 4;
my $key;
until(defined($key = ReadKey(-1))){
# anything
sleep 1;
}
print "got key '$key'\n";
ReadMode('restore');

In many cases one does not want to wait for each step end. In this case you can use two parallel processes:

#!/usr/bin/perl
use strict;
use warnings;
use Carp;
use POSIX;
use Term::ReadKey;
$| = 1; # don't buffer; stdout is hot now
 
#avoid creation of zombies
sub _cleanup_and_die{
ReadMode('restore');
print "process $$ dying\n";
die;
}
sub _cleanup_and_exit{
ReadMode('restore');
print "process $$ exiting\n";
exit 1;
}
$SIG{'__DIE__'} = \&_cleanup_and_die;
$SIG{'INT'} = \&_cleanup_and_exit;
$SIG{'KILL'} = \&_cleanup_and_exit;
$SIG{'TERM'} = \&_cleanup_and_exit;
$SIG{__WARN__} = \&_warn;
 
# fork into two processes:
# child process is doing anything
# parent process just listens to keyboard input
my $pid = fork();
if(not defined $pid){
print "error: resources not available.\n";
die "$!";
}elsif($pid == 0){ # child
for(0..9){
print "doing something\n";
sleep 1;
}
exit 0;
}else{ # parent
ReadMode('cbreak');
# wait until child has exited/died
while(waitpid($pid, POSIX::WNOHANG) == 0){
my $seq = ReadKey(-1);
if(defined $seq){
print "got key '$seq'\n";
}
sleep 1; # if ommitted, the cpu-load will reach up to 100%
}
ReadMode('restore');
}

This code prints "doing something" 10 times and then ends. Parallelly another process prints every key you type in.

Perl 6[edit]

Works with: Rakudo version 2018.10
use Term::ReadKey;
 
react {
whenever key-pressed(:!echo) {
given .fc {
when 'q' { done }
default { .uniname.say }
}
}
}

Phix[edit]

integer key = get_key() -- if key was not pressed get_key() returns -1

PicoLisp[edit]

(setq *LastKey (key))

PowerShell[edit]

The following uses the special $Host variable which points to an instance of the PowerShell host application. Since the host's capabilities may vary this may not work in all PowerShell hosts. In particular, this works in the console host, but not in the PowerShell ISE.

if ($Host.UI.RawUI.KeyAvailable) {
$key = $Host.UI.RawUI.ReadKey()
}

Python[edit]

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import absolute_import, division, unicode_literals, print_function
 
import tty, termios
import sys
if sys.version_info.major < 3:
import thread as _thread
else:
import _thread
import time
 
 
try:
from msvcrt import getch # try to import Windows version
except ImportError:
def getch(): # define non-Windows version
fd = sys.stdin.fileno()
old_settings = termios.tcgetattr(fd)
try:
tty.setraw(sys.stdin.fileno())
ch = sys.stdin.read(1)
finally:
termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
return ch
 
def keypress():
global char
char = getch()
 
def main():
global char
char = None
_thread.start_new_thread(keypress, ())
 
while True:
if char is not None:
try:
print("Key pressed is " + char.decode('utf-8'))
except UnicodeDecodeError:
print("character can not be decoded, sorry!")
char = None
_thread.start_new_thread(keypress, ())
if char == 'q' or char == '\x1b': # x1b is ESC
exit()
char = None
print("Program is running")
time.sleep(1)
 
if __name__ == "__main__":
main()
 

PureBasic[edit]

Returns a character string if a key is pressed during the call of Inkey(). It doesn't interrupt (halt) the program flow.

If special keys (non-ASCII) have to be handled, RawKey() should be called after Inkey().

k$ = Inkey()

Racket[edit]

Using stty to get the terminal into raw mode.

 
#lang racket
(define-syntax-rule (with-raw body ...)
(let ([saved #f])
(define (stty x) (system (~a "stty " x)) (void))
(dynamic-wind (λ() (set! saved (with-output-to-string (λ() (stty "-g"))))
(stty "raw -echo opost"))
(λ() body ...)
(λ() (stty saved)))))
 
(with-raw
(printf "Press a key, or not\n")
(sleep 2)
(if (char-ready?)
(printf "You pressed ~a\n" (read-char))
(printf "You didn't press a key\n")))
 

REXX[edit]

The REXX language doesn't have any keyboard tools, but some REXX interpreters have added the functionality via different methods.

This version   only   works with:

  • PC/REXX
  • Personal REXX
/*REXX program demonstrates if any key has been presssed.               */
 



somechar=inkey('nowait')


Ring[edit]

 
if getchar() see "A key was pressed" + nl
else see "No key was pressed" + nl ok
 

Ruby[edit]

 
begin
check = STDIN.read_nonblock(1)
rescue IO::WaitReadable
check = false
end
 
puts check if check
 

Test in unix shell:

 
% ruby keypress_check.rb
% echo -n y | ruby keypress_check.rb
y
 


Scala[edit]

import java.awt.event.{KeyAdapter, KeyEvent}
 
import javax.swing.{JFrame, SwingUtilities}
 
class KeypressCheck() extends JFrame {
 
addKeyListener(new KeyAdapter() {
override def keyPressed(e: KeyEvent): Unit = {
val keyCode = e.getKeyCode
if (keyCode == KeyEvent.VK_ENTER) {
dispose()
System.exit(0)
}
else
println(keyCode)
}
})
}
 
object KeypressCheck extends App {
println("Press any key to see its code or 'enter' to quit\n")
SwingUtilities.invokeLater(() => {
def foo() = {
val f = new KeypressCheck
f.setFocusable(true)
f.setVisible(true)
f.setSize(200, 200)
f.setEnabled(true)
}
 
foo()
})
}

Seed7[edit]

The library keybd.s7i defines the file KEYBOARD and the function keypressed, which can be used to determine if a key has been pressed.

if keypressed(KEYBOARD) then
writeln("A key was pressed");
else
writeln("No key was pressed");
end if;

Tcl[edit]

There are two ways to handle listening for a key from the terminal. The first is to put the channel connected to the terminal into non-blocking mode and do a read on it:

fconfigure stdin -blocking 0
set ch [read stdin 1]
fconfigure stdin -blocking 1
 
if {$ch eq ""} {
# Nothing was read
} else {
# Got the character $ch
}

The second method is to set up an event listener to perform callbacks when there is at least one character available:

fileevent stdin readable GetChar
proc GetChar {} {
set ch [read stdin 1]
if {[eof stdin]} {
exit
}
# Do something with $ch here
}
 
vwait forever; # run the event loop if necessary

Note that in both cases, if you want to get characters as users actually type them then you have to put the terminal in raw mode. That's formally independent of the actual reading of a character.

TI-83 BASIC[edit]

TI-83 BASIC has a built in getKey function.

 
:getKey→G
 

This returns the key code of the key pressed which is the row number followed by the column number. The left up and down arrow keys are grouped with row 2 as 24, 25, and 26, and the down arrow key is grouped with row 3 as 34.

Wee Basic[edit]

This returns the key code of the key pressed.

let keycode=0
print 1 "Press any key and its key code will appear."
while keycode=0
let keycode=key()
wend
print 1 keycode
end

XPL0[edit]

include c:\cxpl\codes;  \intrinsic 'code' declarations
int K, N;
[N:= 0;
repeat K:= KeyHit; \counts up until a key is pressed
IntOut(0, N); ChOut(0, ^ );
N:= N+1;
until K;
]