Emacs: how to change from insert mode to overwrite mode

 How do I make Emacs “typeover” or “overwrite” instead of inserting?  i.e. change from insert mode to overwrite mode, like Esc + r in vim

Answer:
M-x overwrite-mode (a minor mode). This toggles overwrite-mode on and off, so exiting from overwrite-mode is as easy as another M-x overwrite-mode.

On some systems, Insert toggles overwrite-mode on and off.

Absolute Beginner's Guide to Emacs 4

How to copy and paste a whole file in emacs?


Suppose you are in the middle of a file.

(1) navigate to the first character of the file :  Use  Meta + <  (i.e., Meta key + shift +  ,  )
(2) Enter "Ctrl + Space " to activate the select mode
(3) navigate to the last character of the file :  Use  Meta + >  (i.e., Meta key + shift +  .  )
 (4) Enter "Meta +  w" to copy
 (5) Enter "Ctrl + y" to paste.

Note what is Meta key ?
 On Mac is Mac key, On other keyboard is the Alt key, some old keyboard may use ESC key

More efficient emacs combination keys.

To move the cursor around more quickly, you should avoid using keys like "pageup" "pagedown", "home" "end", because it will cause your hand to leave the standard typing position. Instead you should use the equivalent keys for them:
Like the following left keys all have an equivalent combo on the right, which are faster:
C-up ---> m - {
C-down --> M -}
C-left --> M - b
C-right --> M - f
home --> C - a
end --> C - e
pageup --> M - v
pagedown --> C - v

Absolute Beginner's Guide to Emacs 3

Opening, saving, and closing buffers

To open a file and load it into a buffer, use C-x C-f, which will open a prompt in the mini-buffer that says “Find file: ~/path/to/current/directory/”. Just as with switching buffers, you can press the tab key to list the files in the directory you have specified if you need to.

Find file: ~/learn/shell/

You can then type in the name (and/or change the path) of the file you want:

Find file: ~/learn/shell/zip.sh

Press enter, and a new buffer will be created with the file you specified:

File Edit Options Buffers Tools Sh-Script Help
#!/bin/bash

# Zip all the arguments with for loop
for i in $@; do
  zip archive "$i"
done


-UU-:----F1  zip.sh         All L1     (Shell-script[bash]) -------------------------------------------
Indentation setup for shell type bash

If you make changes to the buffer and you want to save it back to the file on disk, use C-x C-s:
Wrote /home/jtony/learn/shell/zip.sh

Absolute Beginner's Guide to Emacs 2

The three most important keyboard shortcuts to know are C-h C-h (help), C-g (quit), and M-x (run command). The help command will put you in a position to figure out how to do something if you’re stuck, and the quit command will cancel an operation (for example, if you are entering a command at the mini-buffer, C-g will quit the mini-buffer and move the point back to the buffer you were in previously – see the next section for more details on buffers and the mini-buffer). The run command will let you run any command in Emacs; you probably won’t need to use it much right away, but it’s good to know if you run into a scenario where you do need to run a command.

You can’t see the other buffers until you tell Emacs to view them through a window. To do this, use the C-x b key combination. This will move the point to the mini-buffer and display a message that looks like “Switch to buffer (default *scratch*)”:

(Remember that if you want to cancel the current operation, i.e. you decide you don’t want to switch buffers after all, you can use C-g to quit the mini-buffer).

There are a few relevant key commands for manipulating windows:

• C-x 0 : close the active window
• C-x 1 : close all windows except the active window
• C-x 2 : split the active window vertically into two horizontal windows
• C-x 3 : split the active window horizontally into two vertical windows
• C-x o : change active window to next window

Note that closing a window does NOT mean that the buffer it is displaying is closed.

Absolute Beginner's Guide to Emacs 1

Although in standard terminology the running instance of Emacs would be called a window, in Emacs terminology it is called a frame. Within Emacs itself, there is a window in which we see the welcome “GNU Emacs” buffer (more on windows and buffers in a bit).
The blinking black cursor (over the W in “Welcome”) is called the point. Not only is it like a cursor in your standard text editor (where the text is inserted when you type), but it is the location where you will sometimes need to run functions as well (e.g., “change the word that the point is currently in to be uppercase”). We’ll come back to this later.
The grey bar at the bottom of the screen is the status bar and displays various information about the point and the active buffer (there is one status bar per window). The white space below that is called the mini-buffer and will occasionally display status messages (e.g., after saving a file), and is also the place where you enter Emacs commands.

Referred link:
http://www.jesshamrick.com/2012/09/10/absolute-beginners-guide-to-emacs/

Emacs 9: Official tutorial 8

Completion is a way to avoid unnecessary typing.  For instance, if you
want to switch to the *Messages* buffer, you can type C-x b *M<Tab>
and Emacs will fill in the rest of the buffer name as far as it can
determine from what you have already typed.  Completion also works for
command names and file names.  Completion is described in the Emacs
manual in the node called "Completion".

The end of the tutorial.

Emacs 8 Offical Tutorial Part 7

Here are some other useful C-h options:

   C-h f        Describe a function.  You type in the name of the
                function.

Line 1038

vim regular expression substituation

e.g. replace .LBB5_7, .LBB2_3 with .LBB
:%s#.LBB\(.\+\)#.LBB#gc

How to show git statistics for a local change?

jtony@genoa:~/src/llvm$ git diff --stat
 lib/Target/PowerPC/PPCExpandISEL.cpp | 202 ++++++++++++++++++++++++++++++++++++++++++------------------------------------------------
 1 file changed, 95 insertions(+), 107 deletions(-)
jtony@genoa:~/src/llvm$ git diff --numstat