Terminal control/Restricted width positional input/No wrapping
Create a routine to obtain data entry using a specific place on the terminal screen. Data entry fields should be restricted to a specific length, and it should not be possible for the cursor to move beyond the input length.
The routine should accept parameters for row number, column number and input length, and should obtain a string value entered by the user.
For the purpose of this task, obtain input from the user, showing data entry at row 3, column 5, with input width restricted to a maximum of 8 characters.
Note: In this task input wrapping is not allowed. (See Terminal control/Restricted width positional input/With wrapping) for input wrapping variant.
For a similar task using a graphical user interface, see Graphical User Interface/Restricted width positional input/No wrapping.
Common Lisp
ncurses
To interface ncurses from Lisp, the croatoan library is used. <lang lisp>;; Load the library from the quicklisp repository (ql:quickload "croatoan") (in-package :croatoan)
(defun field-input-no-wrapping (row column input-length)
(with-screen (scr :input-echoing nil :cursor-visible t :enable-colors t :enable-function-keys t :input-blocking t)
(let ((field (make-instance 'field :position (list row column) :width input-length :window scr)))
(setf (style field)
(list :background (list :simple-char #\.)))
(bind field #\newline 'accept)
(edit field)
(clear scr)
(refresh scr)
;; return the value of the field as a string
(value field))))
- call the routine
(field-input-no-wrapping 2 4 8)</lang>
Go
This uses _getch() rather than _getwch() as only ASCII is supported.
<lang go>package main
/*
- include <windows.h>
- include <conio.h>
- /
import "C" import (
"fmt" "os" "os/exec"
)
var conOut = C.GetStdHandle(C.STD_OUTPUT_HANDLE)
func setCursor(p C.COORD) {
C.SetConsoleCursorPosition(conOut, p)
}
func cls() {
cmd := exec.Command("cmd", "/c", "cls")
cmd.Stdout = os.Stdout
cmd.Run()
}
func getInput(row, col, width int) string {
if row < 0 || row > 20 || col < 0 || width < 1 || width > 78 || col > (79 - width) {
panic("Invalid parameter(s) to getInput. Terminating program")
}
coord := C.COORD{C.short(col), C.short(row)}
setCursor(coord)
var sb []byte
full := false
loop:
for {
ch := C._getch() // gets next character, no echo
switch c := byte(ch); c {
case 3, 13:
break loop // break on Ctrl-C or enter key
case 8:
if len(sb) > 0 { // mimic backspace
fmt.Print("\b \b")
sb = sb[:len(sb) - 1]
}
case 0, 224:
C._getch() // consume extra character
default:
if c >= 32 && c <= 126 && !full {
C._putch(ch) // echo ascii character, ignore others
sb = append(sb, c)
}
}
full = len(sb) == width // can't exceed width
}
return string(sb)
}
func main() {
cls() // clear the console
s := getInput(2, 4, 8) // Windows console row/col numbering starts at 0
coord := C.COORD{0, 22}
setCursor(coord)
fmt.Printf("You entered '%s'\n", s)
}</lang>
Julia
Requires an ANSI compatible terminal and a system C library implementing _getch() for unbuffered keyboard input. This is the same as /Terminal_control/Restricted_width_positional_input/No_wrapping#Julia but with no width argument in the input call. <lang julia>getch() = UInt8(ccall(:_getch, Cint, ())) cls() = print("\33[2J") reposition(row, col) = print("\u001b[$row;$(col)H") clearfromcursor() = print("\u001b[K")
function input_y_x_upto(row, col, cmax, width=cmax)
buf = ""
while (buflen = length(buf)) < cmax && !((c = getch()) in [0xff, 0x0d, 0x0a])
reposition(row, col)
clearfromcursor()
if c == '\b' && buflen > 0
buf = buf[1:end-1]
else
buf = buf * Char(c)
end
print(buf[(buflen > width ? buflen - width + 1 : 1):end])
end
return buf
end
cls() reposition(3, 5) s = input_y_x_upto(3, 5, 8) println("\n\n\nResult: You entered <<$s>>") </lang>
Kotlin
This assumes an 80 x 25 Windows console and uses the Win32 function _getwch() to get character input without (immediately) echoing it to the console. Only ASCII characters in the range 32 to 126 are then printed if the maximum width would not be exceeded.
Apart from these, only the backspace key (8), return key (13) and Ctrl-C (3) are handled, all other keys being ignored. Some keys (such as the function and arrow keys) return a two character sequence starting with either 0 or 224 and so, after the first character is trapped, the second character needs to be removed from the buffer.
It would also be possible to allow for printable Unicode characters (>= 160) to be entered by adding an extra clause to the 'when' statement. However, for this to work properly, you will need to be using a suitable code page (65001, say) and a suitable font (Lucida Console, say). <lang scala>// Kotlin Native v0.5
import kotlinx.cinterop.* import platform.windows.* import platform.posix.*
val ascii = 32..126 val conOut = GetStdHandle(STD_OUTPUT_HANDLE)!!
fun setCursor(p: COORD) = SetConsoleCursorPosition(conOut, p.readValue())
fun getInput(row: Short, col: Short, width: Int): String {
require(row in 0..20 && col in 0..(79 - width) && width in 1..78) { "Invalid parameter(s)" }
memScoped {
val coord = alloc<COORD>().apply { X = col; Y = row }
setCursor(coord)
}
val sb = StringBuilder(width)
var full = false
loop@ while (true) {
val ch = _getwch() // gets next character, no echo
when (ch.toInt()) {
3, 13 -> break@loop // break on Ctrl-C or enter key
8 -> if (sb.length > 0) { print("\b \b"); sb.length-- } // mimic backspace
0, 224 -> _getwch() // consume extra character
in ascii -> if (!full) { _putwch(ch); sb.append(ch.toChar()) } // echo ascii character
else -> {} // igore other characters
}
full = sb.length == width // can't exceed width
}
return sb.toString()
}
fun main(args: Array<String>) {
system("cls") // clear the console
val s = getInput(2, 4, 8) // Windows console row/col numbering starts at 0
memScoped {
val coord = alloc<COORD>().apply { X = 0 ; Y = 22 }
setCursor(coord)
}
println("You entered '$s'")
}</lang>
Phix
<lang Phix>function getInput(integer row, col, width)
position(row,col)
string s = ""
while 1 do
integer ch = wait_key()
if ch='\r' then exit end if
if ch='\b' then
if length(s)>0 then
puts(1,"\b \b")
s = s[1..$-1]
end if
elsif ch>=' ' and ch<='~' then
if length(s)<=width then
puts(1,ch)
s &= ch
end if
end if
end while
return s
end function
clear_screen() -- clear the console string s = getInput(3, 5, 8) position(23,1) printf(1,"You entered '%s'\n",{s})</lang>
Raku
(formerly Perl 6)
Should work with any termios compatible terminal.
All printable character keys work, as does backspace and enter. Ctrl-c to exit. All other keys / key-combos are ignored.
<lang perl6>use Term::termios;
constant $saved = Term::termios.new(fd => 1).getattr; constant $termios = Term::termios.new(fd => 1).getattr;
- raw mode interferes with carriage returns, so
- set flags needed to emulate it manually
$termios.unset_iflags(<BRKINT ICRNL ISTRIP IXON>); $termios.unset_lflags(<ECHO ICANON IEXTEN ISIG>); $termios.setattr(:DRAIN);
END {
$saved.setattr(:NOW); # reset terminal to original settings print "\e[?25h \e[H\e[J"; # clear and reset screen
}
my $row = 3; my $column = 5; my $field = ; my $spacer = ' ' x 8; my $pointer = 0;
my ($rows,$cols) = qx/stty size/.words; # get screen size
my @screen = "\e[41m{' ' x $cols}\e[0m" xx $rows;
update($spacer);
loop {
my $key = $*IN.read(4).decode;
given $key {
when ' '..'~' {
if $pointer < 8 {
$field ~= $_;
$spacer = ' ' x 8 - $field.chars;
$pointer +=1;
update($field~$spacer)
}
}
when "\c[127]" { # backspace
if $pointer > 0 {
$field.=substr(0,*-1);
$spacer = ' ' x 8 - $field.chars;
$pointer -= 1;
update($field~$spacer)
}
}
when "\c[13]" {
update(' ');
print "\e[10;6H\e[1;33;41mYou entered: $field\e[0m\e[$row;{$column}H";
$field = ;
$pointer = 0;
}
when "\c[0003]" { exit } # Ctrl-c
default { }
}
}
sub update ($str) {
($rows,$cols) = qx/stty size/.words;
@screen = "\e[41m{' ' x $cols}\e[0m" xx $rows;
print "\e[H\e[J{@screen.join: "\n"}\e[$row;{$column}H$str\e[$row;{$column + $pointer}H";
}</lang>