How can I access the higher function keys (F16 in particular) on a MacBook Pro?

Question

I'm toying around with DOSBox in debugger mode and it seems that in order to break into the debug mode while running I need to run Alt-Pause which on the Mac is Alt+F16 (see DOSBoxWiki: Special Keys). However, there is no F16 key on a MacBook Pro; if you hold Fn, you only get F1-F12.

Is there some way to either remap a function key or to have access to the higher function keys? Even using the Accessibility keyboard, it doesn't seem to have obvious access to these keys.

Answer 1

To remap a key, you can use the hidutil command. In this example, I am remapping F16 to the ⌥ Option on the right side (probably not used much, if at all).

hidutil property --set '{"UserKeyMapping": \
[{\"HIDKeyboardModifierMappingSrc":0x7000000E6, \
"HIDKeyboardModifierMappingDst":0x70000006A}]}}

^{The backslashes (\) allow for a multi-line command to facilitate better readability. The command can be copied/pasted as-is or the backslashes and new-lines removed to make it a true one-liner.}

When you're writing the command, keep this in mind:

• Src = the key you want to press
• Dst = what you want it to do

I have supplied a portion of the Hex values for the extended function keys as defined in Apple Technical Note TN240 that describes how to use hidutil.

Key	Hex Code	Key	Hex Code
Keyboard F13	0x68	Keyboard F19	0x6E
Keyboard F14	0x69	Keyboard F20	0x6F
Keyboard F15	0x6A	Keyboard F21	0x70
Keyboard F16	0x6B	Keyboard F22	0x71
Keyboard F17	0x6C	Keyboard F23	0x72
Keyboard F18	0x6D	Keyboard F24	0x73

Improving with a script...

To make this complex command easier to work with, I have created a simple Bash script (below) that will allow you to specify the source and destination keys as variables.

I used a function, mdCMDStr, to "make the command string" so you can easily replicate additional commands with minimal effort. Simply, reassign the SOURCE and DEST variables and call the mkCMDStr and hidutil commands as many times as necessary.

#! /bin/bash



function mkCMDStr () {
# Creates the command string

    SETKEY_CMD={\"UserKeyMapping\":[{\"HIDKeyboardModifierMappingSrc\":${1},\"HIDKeyboardModifierMappingDst\":${2}}]}

}

SOURCE=0x7000000E6      #Keyboard Right Option/Alt              
DEST=0x70000006A        #Keyboard F16

mkCMDStr $SOURCE $DEST
hidutil property --set "${SETKEY_CMD}"

exit

Download the Script

This will not persist through reboots. You can make this "permanent" by putting this script in Login Items or creating a LaunchAgent.