Inkey

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Inkey

Returns the next key waiting, or an empty string at once if there is none.

Syntax

Declare Function Inkey ( ) As String

Description

Peeks into the keyboard buffer and returns a String representation of the first character, if any, found. The key is then removed from the buffer, and is not echoed to the screen. If the keyboard buffer is empty, an empty string ("``") is immediately returned without waiting for keys.

If the key is in the ASCII character set, a one-character String consisting of that character is returned.
If the key is an "extended" one (numeric pad, cursors, functions) a two-character String is returned, the first of which is the extended character (See dialect differences below), and the second is the raw scancode for the keyboard.

For FB's built-in functionality of getting keyboard input, see Keyboard Input (Basics).

The Shift, Ctrl, Alt, and AltGr keys can't be read independently by this function as they never enter the keyboard buffer (although, perhaps obviously, Shift-A will be reported by Inkey differently than Control-A et cetera; Alt-A is an extended key a la the above).

See also Input() or GetKey, or Sleep to wait for a key press if the keyboard buffer is empty.

Return Value

The first character found in the keyboard buffer, or an empty string ("``") if none found.

Remarks

Usage

result = Inkey[$]

Dialect Differences

• The extended character is Chr(255) in the -lang fb and -lang fblite dialects.

  • In the -lang qb dialect, the extended character depends on how the keyword is written. If the QB form Inkey$ is used, the extended character is Chr(0). If it is referenced as __Inkey, the extended char is Chr(255). In all other dialects, the extended char is always Chr(255).

  The string type suffix "$" is required in the -lang qb dialect.
  The string type suffix "$" is optional in the -lang fblite dialect.
  The string type suffix "$" is ignored in the -lang fb dialect, warn only with the -w suffix compile option (or -w pedantic compile option).

Differences from QB

• None in the -lang qb dialect. QBasic returned a Chr(0) as the first character for an extended key, but FreeBASIC returns Chr(255) as the first character in the -lang fb and -lang fblite dialects.

See also

• Sleep
• GetKey
• Input()
• MultiKey
• Keyboard scancodes

Examples

Print "press q to quit"

Do

    Sleep 1, 1

Loop Until Inkey = "q"

'' Compile with -lang fblite or qb

#lang "fblite"

#if __FB_LANG__ = "qb"

#define EXTCHAR Chr$(0)

#else

#define EXTCHAR Chr(255)

#endif

Dim k As String

Print "Press a key, or Escape to end"

Do

    k = Inkey$

    Select Case k

        Case "A" To "Z", "a" To "z": Print "Letter: " & k

        Case "1" To "9":             Print "Number: " & k

        Case Chr$(32): Print "Space"

        Case Chr$(27): Print "Escape"

        Case Chr$(9): Print "Tab"

        Case Chr$(8): Print "Backspace"

        Case Chr$(32) To Chr$(127)

            Print "Printable character: " & k

        Case EXTCHAR & "G": Print "Up Left / Home"

        Case EXTCHAR & "H": Print "Up"

        Case EXTCHAR & "I": Print "Up Right / PgUp"

        Case EXTCHAR & "K": Print "Left"

        Case EXTCHAR & "L": Print "Center"

        Case EXTCHAR & "M": Print "Right"

        Case EXTCHAR & "O": Print "Down Left / End"

        Case EXTCHAR & "P": Print "Down"

        Case EXTCHAR & "Q": Print "Down Right / PgDn"

        Case EXTCHAR & "R": Print "Insert"

        Case EXTCHAR & "S": Print "Delete"

        Case EXTCHAR & "k": Print "Close window / Alt-F4"

        Case EXTCHAR & Chr$(59) To EXTCHAR & Chr$(68)

            Print "Function key: F" & Asc(k, 2) - 58

        Case EXTCHAR & Chr$(133) To EXTCHAR & Chr$(134)

            Print "Function key: F" & Asc(k, 2) - 122

        Case Else

            If Len(k) = 2 Then

                Print Using "Extended character: chr$(###, ###)"; Asc(k, 1); Asc(k, 2)

            ElseIf Len(k) = 1 Then

                Print Using "Character chr$(###)"; Asc(k)

            End If

    End Select

    If k = Chr$(27) Then Exit Do

    Sleep 1, 1

Loop

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Category: User Input (Runtime Library)
Kind: function

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.