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Map Caps Lock to Escape, or any key to any key
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README.md

Uncap

Map Caps Lock key to Escape key, or any to any key, on Windows systems.

Download MIT License

Apart from documenting how Uncap works on Windows, this README contains detailed documentation about how to remap keys on Linux and Mac as well.

Contents

Features

The following list briefly describes some of the features of Uncap.

  1. Map Caps Lock key to Escape key on a new Windows system with almost no effort. Just download and double-click. This is the primary reason why Uncap was written. This tool was written for users of vi editor who like to map their Caps Lock key to Escape key for convenience.
  2. Map any key to any key, multiple keys to other keys, or disable keys using command line arguments. No additional file or script is required.
  3. Enable, disable or modify key mappings without having to reboot the Windows system.
  4. Disable key mappings easily by stopping Uncap.
  5. It is a single-file executable. It is very lightweight. The executable is only about 100 KB in size. It occupies less than 1 MB of memory and negligible CPU while running.

There are several other methods and tools available on Windows to map one key to another. But none of them seem to have all five features enumerated above. For example, editing Scancode Map registry value requires the Windows system to be rebooted after every change. On the other hand AutoHotKey requires an additional script file to be written. Therefore, Uncap was written to support all five features described above.

Get Started

Uncap is a single-file executable: uncap.exe.

The simplest way to run it is to download it and double-click it. No output window is displayed. It runs in background. Once it is running, whenever Caps Lock key is pressed, it is translated to the Escape key by Uncap.

Custom Mapping

It is possible to override the default mapping of Caps Lock key to Escape key by specifying a custom mapping, however to do so, Uncap must be run with arguments either from Command Prompt or from Windows Run dialog box. The following steps show how uncap.exe may be used to map Caps Lock key to Left Control key.

  1. Copy uncap.exe to a directory specified in the Windows PATH variable. C:\Windows is a very convenient location to copy this file to.

  2. Launch Windows Run dialog box by pressing Windows Logo Key + R.

  3. Enter the following command.

    uncap 0x14:0xa2
    
  4. Press OK button. This would launch Uncap. No output window would be displayed. Uncap would run in background. Whenever Caps Lock key is pressed now, Uncap would translate it to Left Control key.

  5. To terminate Uncap, run the following command.

    uncap -k
    

In the above steps, Caps Lock key is mapped to Left Control key by specifying 0x14:0xa2 as an argument to Uncap. The virtual-key code of Caps Lock is 0x14 and the virtual-key code of Control key is 0xa2. Therefore, the argument 0x14:0xa2 maps Caps Lock key to Control key.

The list of virtual-key codes for every key can be found at https://msdn.microsoft.com/library/windows/desktop/dd375731.aspx.

Usage

When Uncap is run without any arguments, it maps Caps Lock key to Escape key. It may be run with arguments to map Caps Lock key to any key, any key to any key, or disable any key.

Each argument is a colon separated pair of virtual-key codes from https://msdn.microsoft.com/library/windows/desktop/dd375731.aspx.

The virtual-key code may be specified either as hexadecimal integer as mentioned in the above URL or its equivalent decimal notation. These details are illustrated in the list of examples below.

  1. Map Caps Lock key to Escape key.

    uncap
    
  2. Swap Caps Lock key with Escape key.

    uncap 0x1b:0x14
    

    Caps Lock key is already mapped to Escape key by default. The above command maps Escape key to Caps Lock key, thus effectively swapping both keys.

  3. The hexadecimal integer is case-insensitive, so the following command is equivalent to the previous command.

    uncap 0x1B:0x14
    
  4. The virtual-key codes may be specified in decimal notation, so the following command is equivalent to the previous command.

    uncap 27:20
    
  5. Map Caps Lock key to Left Control key.

    uncap 0x14:0xa2
    
  6. Swap Caps Lock key and Left Control key.

    uncap 0x14:0xa2 0xa2:0x14
    

    This example shows that it is possible to specify more than one argument to map multiple keys to other keys.

  7. Here is another example that maps multiple keys to other keys. The following command maps Caps Lock key to Left Control key, Left Control key to Escape key and Escape key to Caps Lock key.

    uncap 0x14:0xa2 0xa2:0x1b 0x1b:0x14
    
  8. If a key is mapped to itself, then no mapping occurs for it. This may be used to override default behaviour of mapping Caps Lock key to Escape key and leave it unmapped while mapping another key to some key. Here is an example that unmaps Caps Lock key and maps F1 key to escape key.

    uncap 0x14:0x14 0x70:0x1b
    

    When a key is mapped to another key, and that key is pressed, Uncap translates it to the key it is mapped to by synthesizing a new keystroke and injecting it into the system. But when a key is mapped to itself, and that key is pressed, it is ignored, thus no translation or synthesis of a new keystroke occurs.

  9. If a key is mapped to 0, then the key is disabled. Here is an example that disables Caps Lock key completely.

    uncap 0x14:0
    
  10. Uncap runs without displaying a console by default. To terminate another instance of Uncap that may be running, use the -k or --kill option.

    uncap -k
    

    The above command kills all other instances of Uncap that are running with or without a console.

  11. To run Uncap with a console, use the -c or --console option.

    uncap -c
    

    When Uncap is running in a console like this, it may be terminated by pressing Ctrl + C.

  12. To run Uncap in debug mode, use the -d or --debug option.

    uncap -d
    

    The debug output contains one line of output with details about every press of a key or release of a key.

  13. To log the keystroke details to a file, use the -f or --file option.

    uncap -f C:\keys.txt
    

    With this option alone, Uncap runs in background and logs the keystroke details to the specified file. This option may be combined with -c or -d to run Uncap in a console or print debug output on the console, respectively.

  14. See the complete usage details along with options supported.

    uncap -h
    

Known Issue with Microsoft Edge on Windows 10

When Uncap is downloaded using the Microsoft Edge web browser on Windows 10, it sometimes fails to map keys.

The following measures have found to be unsuccessful in resolving the issue:

  • Right clicking uncap.exe, then selecting Properties, then selecting Unblock, and then clicking OK does not resolve the issue.

  • Right clicking uncap.exe, then selecting Properties, then going to Security tab, then clicking Edit, and then removing the following two accounts does not resolve the issue:

    Unknown Account(S-1-15-2-3624051433-2125758914-1423191267-1740899205-1073925389-3782572162-737981194)
    Unknown Account(S-1-15-3-3624051433-2125758914-1423191267-1740899205-1073925389-3782572162-737981194)
    

    These accounts are added automatically to files downloaded with Microsoft Edge.

The following workarounds have been found to resolve the issue successfully:

  • Copy uncap.exe to a new file in the same directory. The new file when run remaps keys successfully. Finally, delete the downloaded uncap.exe, then rename the new file to uncap.exe, and use it normally.

  • Copy uncap.exe to some other directory. The new copied file when run remaps keys successfully.

This issue was observed with Microsoft Edge Microsoft Edge 44.17763.1.0 on Windows 10 Pro.

Alternatives

There are other tools and methods available to map one key to another on Windows, Linux and Mac. This section describes a few such tools and methods.

Windows: Scancode Map registry value

One way to map a key to another key in Windows without using any additional software is by editing the registry to add a value called "Scancode Map" in "HKLM\SYSTEM\CurrentControlSet\Control\Keyboard Layout" registry key.

For example, to map Caps Lock key to Escape key, create a registration entries file, i.e. a file with reg as its extension, say uncap.reg, with the following content.

REGEDIT4
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
"Scancode Map"=hex:00,00,00,00,00,00,00,00,02,00,00,00,01,00,3a,00,00,00,00,00

Then save the file. Then double-click this file to add it to Windows registry. Then reboot the Windows system. After rebooting, whenever Caps Lock key is pressed, it would function like Escape key.

The same registry value may be added by running the following command in Command Prompt.

reg add "HKLM\SYSTEM\CurrentControlSet\Control\Keyboard Layout" /v "Scancode Map" /t REG_BINARY /d 00000000000000000200000001003a0000000000

The hexadecimal code in the registry value is the scan code map. The format of the scan code map is described in detail at https://msdn.microsoft.com/library/windows/hardware/jj128267.aspx#scan_code_mapper_for_keyboards.

The following command may be used to view this registry value.

reg query "HKLM\SYSTEM\CurrentControlSet\Control\Keyboard Layout" /v "Scancode Map"

The following command may be used to remove this registry value.

reg delete "HKLM\SYSTEM\CurrentControlSet\Control\Keyboard Layout" /v "Scancode Map"

While this method has an advantage that it requires no additional software, a disadvantage of this method is that it requires the system to be rebooted after every change in the registry.

There is a tool called SharpKeys that comes with graphical user interface to manage this registry value. However a reboot is still required after every change made with SharpKeys.

Windows: AutoHotKey

There is a fairly sophisticated scripting language for Windows called AutoHotKey that can be used to map one key to another, among many other things.

It is quite simple to map one key to another using AutoHotKey. For example, after installing AutoHotKey, to map Caps Lock key to Escape key, create an AutoHotKey script, i.e. a file with ahk as its extension, say uncap.ahk, with the following content.

CapsLock::Esc

Then save the file. Then double-click this file to run AutoHotKey with this script. Once this is done, whenever Caps Lock key is pressed, it is translated to Escape key. An AutoHotKey icon appears in the notification area (system tray). To stop it, right click on the icon and select 'Exit'.

This method has an advantage that it does not require the system to be rebooted. However, AutoHotKey is a scripting language that can be used to do a number of other things such as defining hotkeys (shortcut keys), hotstrings (auto-replace), macros (scripted actions), etc. This may feel akin to killing a fly with a sledgehammer if one just wants to map a key to another key.

Linux: setxkbmap

On Linux, the setxkbmap command may be used to map one key to another key in the X Window System. For example, the following command maps Caps Lock key to Escape key.

setxkbmap -option caps:escape

The list of options along with a short description for each can be found at /usr/share/X11/xkb/rules in a .lst file with the same name as the current XKB rule. The current XKB rule as well as the current mapping options can be found in the output of this command.

setxkbmap -query

For example, if 'evdev' is displayed as the current rules, then see /usr/share/X11/xkb/rules/evdev.lst for the list of available options along with a short description for each option.

In the output of the above command, the line that begins with 'rules:' in the output of the above command shows the current XKB rules. The key mapping option is displayed in the line that begins with 'option:' in the output of the above command. If there is no such line, then no key mapping option is set.

The following command removes any key mapping option.

setxkbmap -option

Linux: xmodmap

On Linux, there is another command called xmodmap that may be used to map one key to another in the X Window System. However this command is now considered obsolescent. It is also a little clumsy to use, especially while removing a key mapping. The setxkbmap command described in the previous section is the preferred way of mapping keys in the X Window System. However, this section describes how to use xmodmap to map one key to another because this method is still in use although its use is gradually fading away. As an example, this section describes how to map Caps Lock key to Escape key.

Before performing the key mapping, one needs to find the key code of Caps Lock key in the X Window System. This is useful while reverting the key mapping. Here is the command to get the key code for Caps Lock key.

xmodmap -pke | grep Caps_Lock

For PC keyboards, the key code is usually 66.

The following command maps Caps Lock key to Escape key.

xmodmap -e "remove Lock = Caps_Lock" -e "keysym Caps_Lock = Escape"

Here is another command that also maps Caps Lock key to Escape key if the key code for Caps Lock is 66. This command makes use of keycode instead of keysym.

xmodmap -e "remove Lock = Caps_Lock" -e "keycode 66 = Escape"

The following two commands display the current details.

xmodmap -pm -pke

The following command undoes the mapping.

xmodmap -e "keycode 66 = Caps_Lock" -e "add Lock = Caps_Lock"

Note that keycode is used in the above command. If keysym Escape = Caps_Lock is used instead in the above command, then along with reverting the Caps Lock key to function like Caps Lock, it would also change the behaviour of the Escape key to function like Caps Lock. Using keycode 66 = Caps_Lock ensures that only the behaviour of Caps Lock key only is restored.

Linux: loadkeys

On Linux, the loadKeys command may be used to map one key to another in console. This section describes how to map Caps Lock key to Escape key. All commands in this section must be run as root or superuser.

Before performing the key mapping, one needs to find the key code of Caps Lock key in the console. This is also going to be useful while reverting the key mapping.

Here is a quick way to find the key code of Caps Lock key in console.

dumpkeys | grep -E "CtrlL_Lock|Caps_Lock"

In this section, we assume that the key code for Caps Lock key is 58 and it is mapped to Caps_Lock key, which is indeed true on most systems. On Debian based systems, the key code 58 may be mapped to CtrlL_Lock to work around Debian bug 514464 and kernel bug 7746.

The following command maps Caps Lock key to Escape key.

(dumpkeys | grep keymaps; echo keycode 58 = Escape) | loadkeys

The following command undoes the mapping.

(dumpkeys | grep keymaps; echo keycode 58 = Caps_Lock) | loadkeys

Mac: System Preferences

Since macOS Sierra Version 10.12.1, it is easy to map Caps Lock to Escape via System Preferences. Perform the following steps to do so.

  1. Go to the Apple menu > System Preferences > Keyboard.
  2. Click Modifier Keys.
  3. Set Caps Lock Key to Escape.
  4. Click OK.

Mac: Seil

In OS X, the mapping options available via System Preferences are very limited. For example, it does not allow Caps Lock to be mapped to Escape. Therefore in general, it becomes necessary to install additional software to map keys in OS X.

A popular tool for mapping one key to another on OS X is Seil. Here is an article by my beautiful girlfriend and wife that describes how to map Caps Lock to Escape on OS X using Seil: http://sunainapai.in/blog/map-caps-lock-to-escape-on-mac-os-x/.

Resources

Here is a list of useful links about this project.

License

This is free and open source software. You can use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of it, under the terms of the MIT License. See LICENSE.md for details.

This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND, express or implied. See LICENSE.md for details.

Support

To report bugs, suggest improvements, or ask questions, please visit https://github.com/susam/uncap/issues.

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