How do I remap F3 and F4 keys to ( )

You do not know how annoying is to press SHIFT + 9 and SHIFT + 0 every time you want to get the parenthesis "(" ")". Henceforth, in Ubuntu 12.01 is possible to remap F3 and F4, actually any key, so as to have a more enjoyable experience while coding.

1. Start terminal window and run xev. Now it's active and waits for you to press a key. Then press the key whose behavior you want to change:

$xev

KeyRelease event, serial 36, synthetic NO, window 0x5a00001,
    root 0xb5, subw 0x0, time 4740799, (-257,-664), root:(468,237),
    state 0x11, keycode 18 (keysym 0x28, parenleft), same_screen YES,
    XKeysymToKeycode returns keycode: 187
    XLookupString gives 1 bytes: (28) "("
    XFilterEvent returns: False

KeyPress event, serial 36, synthetic NO, window 0x5a00001,

    root 0xb5, subw 0x0, time 4741289, (-257,-664), root:(468,237),

    state 0x11, keycode 19 (keysym 0x29, parenright), same_screen YES,

    XKeysymToKeycode returns keycode: 188

    XLookupString gives 1 bytes: (29) ")"

    XmbLookupString gives 1 bytes: (29) ")"

    XFilterEvent returns: False

KeyRelease event, serial 36, synthetic NO, window 0x5a00001,

    root 0xb5, subw 0x0, time 4894370, (-353,-482), root:(372,419),

    state 0x10, keycode 69 (keysym 0xffc0, F3), same_screen YES,

    XLookupString gives 0 bytes: 

    XFilterEvent returns: False

KeyRelease event, serial 36, synthetic NO, window 0x5a00001,

    root 0xb5, subw 0x0, time 4895370, (-353,-482), root:(372,419),

    state 0x10, keycode 70 (keysym 0xffc1, F4), same_screen YES,

    XLookupString gives 0 bytes: 

    XFilterEvent returns: False

2. Now when you want to swap the two keys use xmodmap. 

$ xmodmap -e "keycode 69 = parenleft"

$ xmodmap -e "keycode 70 = parenright"

+++++TESTING+++++

Soonafter remaping the keys,

key night and key zero have been disable! :S

It will be necessary to read more detailed information to get 

an appropriate config.

Nonetheless, after rebooting the previous-mentioned commands are working and it does not need to remap the keys 9 and 0 again, i.e.

xmodmap -e "keycode 18 = 9"
xmodmap -e "keycode 19 = 0"

KeyRelease event, serial 36, synthetic NO, window 0x4a00001,
    root 0xb5, subw 0x0, time 212931, (-415,-323), root:(548,578),
    state 0x10, keycode 18 (keysym 0x39, 9), same_screen YES,
    XLookupString gives 1 bytes: (39) "9"
    XFilterEvent returns: False

KeyPress event, serial 36, synthetic NO, window 0x4a00001,
    root 0xb5, subw 0x0, time 213451, (-415,-323), root:(548,578),
    state 0x10, keycode 19 (keysym 0x30, 0), same_screen YES,
    XLookupString gives 1 bytes: (30) "0"
    XmbLookupString gives 1 bytes: (30) "0"
    XFilterEvent returns: False

+++++++++++

Note: These change are for the active x session only and will be lost after reboot. When you want to save the changes permanently you have to run the following commands after the ones above:

xmodmap -pke >~/.Xmodmap

(it creates a files called .Xmodmap in your home directory ~ )
Then you have to create a file called .xinitrc in your home directory where you put this commandline xmodmap .Xmodmap in.

http://askubuntu.com/questions/24916/how-do-i-remap-certain-keys