Emacs key Commands - Conveyor-Belt Sushi
25 March 2007
Guide to Emacs Key-bindings
The normal Emacs convention is that Control is represented by the large C. The small c is the 'c key', i.e. the third letter of the alphabet. So C-y means to press Control and the 'y key' at the same time.
M means Meta, which is a key on 1970s Unix keyboards, called Alt on the mass- produced IBM PC-compatible keyboards that we have today. As an alternative to 'Alt', you can use escape and then take a little breath before pressing the next key; this is handy to know in a couple of situations:
- Some graphical terminals use Alt for their own shortcuts, i.e. shortcuts controlling the box rather than passing the key commands to the application inside. You can use ESC in this situation or (better) edit the preferences of the terminal.
- When connected to a remote terminal, especially if it is running a more traditional Unix, sometimes Alt commands cannot reach the remote server.
Emacs Terminology
Emacs has its roots in another age, its terminology is based on the reality of bits and bytes, disks and processors, and so on. Rather than most modern programmes that, post Apple Lisa, are based on metaphorical concepts of a paper based office. You are either a person that finds it really romantic, or you find it really annoying. It also means that the key commands do not follow the later X-Windows/MS Office style. You can set the key commands to this style, but very few people do. Most people learn the Emacs way. You can then often use these same bindings with lots of other programs, especially command-line applications.
'Cut' and 'Paste' have not been invented yet, we have kill and yank instead. There is no clipboard, there are superior concepts called the 'mark' and the 'kill ring'.
The Mark
One way to understand it is that instead of one point that you have in the graphical world, imagine that you have two points. You have one that you drop somewhere - the mark, and a cursor that you move around as normal. Another way to think of it is what happens when you select text in a graphical program. You hold shift (or click the mouse) and then move the cursor away, highlighting the text in the process; the initial point that that you click on is the 'mark'. So you place the mark with C-Space. Now as you move the cursor away, imagine that the text is being highlighted.
When you cut text (with C-w), everything between where your cursor is now and the mark goes into the kill-ring, this is a type of list. It is like a stack, but when you get to the bottom, it goes back to the start. Therefore unlike the X-Windows clipboard, which has one item, the kill ring can have lots of different items, all that can be retrieved, or 'yanked', from the ring. To yank the first item off the kill ring, you use C-y. To non-destructively copy an item into the kill ring, you use M-w (analogous to 'Copy' in X-Windows).
Conveyor-belt sushi
So at posh Japanese restaurants, you sit down for lunch and there is a conveyor-belt, it goes round and all different types of fish pass by. Now this is a really posh sushi bar frequented by ecological types, and there is a small handle in front of you that moves the belt around. Somewhere is a chef is killing fish, while someone else wraps them up nicely and puts them on the conveyor belt. You turn the handle until you can grab whatever you want off it. Then you pretend you can use chop sticks so you do not embarrass yourself in front of the posh people who brought you here.
So you kill text (using C-w or M-w) and add it to the Conveyor-belt (the kill ring), C-y puts your hand out ready to grab the next thing, while M-y rotates the Conveyor belt.
Now the analogy starts to fall apart a little, I know, but imagine that the dishes are stacked up on the conveyor-belt, so when the Makizushi rolls come around, you can take one dish, or two or three. Yanking something from the kill ring does not stop you getting the same piece of text again.
Once you have got that sorted, you can do more complex tricks, C-u 8 M-y would rotate the conveyor belt 8 dishes. Taking it one-step further, C-u 5 C-y would automatically yank the fifth item from the kill ring, equivalent to leaning over your friends and grabbing a dish.
There are more complex ways to manipulate the kill ring (i.e. the person wrapping the fish) but lets move on to more pressing matters first.
1 Zeth says...
Hello World
Posted at 2:45 p.m. on September 13, 2007
2 Zeth says...
Hello World.
Posted at 3:10 p.m. on September 14, 2007
3 Zeth says...
Hello World again!
Posted at 3:13 p.m. on September 14, 2007
4 Zeth says...
Arrrrrrhhmmm
Posted at 3:20 p.m. on September 14, 2007