KeyCode Viewer

Simple KeyCode Viewer for *nix terminals

This is a simple toy program to get information about the keycodes of the pressed keys, for educational and quick reference purposes.

Usage

Shows information of every pressed key:

$ ./kcv
 97 [0x61] 0_11_00001 ('a')
  3 [0x03] 0_00_00011 (control char, base 'C', '^C')

Invoke make to compile (hopefully it just works...) and call ./kcv to execute.

By default, to exit the program, q must be pressed (^C won't work as it is captured):

$ ./kcv
113 [0x71] 0_11_10001 ('q')
$

To use another exit key, use the first argument:

$ ./kcv a
113 [0x71] 0_11_10001 ('q')
 97 [0x61] 0_11_00001 ('a')
$

For every pressed key it shows:

• Decimal and hex values of the keycode.

• Binary separated in 3 bit fields in order:

  • 1 bit that is 1 only when the code does not belong to 7-bit ASCII.

  • 2 bits showing (in general) whether it is a control char (00), a symbol (01), an uppercase letter (10) or a lowercase letter (11).

  • Last 5 bits: base key code.

• Extra info.

Examples of usage

It is useful for stuff like:

• Not having to search the ASCII code for ^C:

    3 [0x03] 0_00_00011 (control char, base 'C', '^C')
  

• Finding the relation between A, Shift+A and Ctrl+A:

   97 [0x61] 0_11_00001 ('a')
   65 [0x41] 0_10_00001 ('A')
    1 [0x01] 0_00_00001 (control char, base 'A', '^A')
  

• Realising that Ctrl+A and Ctrl+Shift+A both produce the same results:

    1 [0x01] 0_00_00001 (control char, base 'A', '^A')
    1 [0x01] 0_00_00001 (control char, base 'A', '^A')
  

• Finding the difference between Enter (CR, \r) and Ctrl+J (LF, \n):

   13 [0x0d] 0_00_01101 (control char, base 'M', '^M')
   10 [0x0a] 0_00_01010 (control char, base 'J', '^J')
  

• Realising that some key presses are actually translated as two keycodes, example á:

  195 [0xc3] 1_10_00011 (other char, base 'C', '^C')
  161 [0xa1] 1_01_00001 (other char, base 'A', '^A')