Compose Key

The Compose Key allows you to input special characters by pressing two or more subsequent keys. For example, pressing Compose then / + = will print a ≠ (not equal to) sign.

Choose a key in the list:

$ grep "compose:" /usr/share/X11/xkb/rules/base.lst

Then add the following line in your .xinitrc (change <key> to the key you want):

$ setxkbmap -option compose:<key>

Some useful combinations not directly accessible on my keyboard:

<Multi_key> <minus> <minus> <period>    : "–"   U2013 # EN DASH
<Multi_key> <minus> <minus> <minus>     : "—"   U2014 # EM DASH
<Multi_key> <period> <equal>            : "•"   enfilledcircbullet # BULLET
<Multi_key> <slash> <o>                 : "ø"   oslash # LATIN SMALL LETTER O WITH STROKE
<Multi_key> <o> <a>                     : "å"   aring # LATIN SMALL LETTER A WITH RING ABOVE
<Multi_key> <slash> <equal>  	        : "≠"   U2260 # NOT EQUAL TO
<Multi_key> <less> <equal> 	            : "≤"   U2264 # LESS-THAN OR EQUAL TO
<Multi_key> <greater> <equal> 	        : "≥"   U2265 # GREATER-THAN OR EQUAL TO
<Multi_key> <d> <i>		                : "⌀"   U2300 # DIAMETER SIGN
<Multi_key> <8> <8>                     : "∞"   U221e # 8 8 INFINITY

To configure the combinations:

$ cp /usr/share/X11/locale/en_US.UTF-8/Compose ~/.XCompose