Learn about Emacs
Here I will cover some basic manipulation with text files using emacs. It should be enough to get started working with emacs.
Terms in Emacs
- Region: the highlighted area
- Kill: same as "cut"
- Yank: same as "paste"
Emacs Key Notation
|C-||(press and hold) the Control key|
|M-||the Meta key (the Alt key, on most keyboards)|
|S-||the Shift key (ie. S-TAB means Shift Tab)|
|DEL||the Backspace key (not the Delete key).|
|RET||the Return or Enter key|
|SPC||the Space bar key|
|ESC||the Escape key|
|TAB||the TAB key|
|ARR||the arrow keys|
- C-g keyboard-quit; cancels anything Emacs is executing. If you press any key sequence wrongly, C-g to cancel that incorrectly pressed key sequence and start again.
- C-x C-c close emacs
- C-x b Open a promt to enter a buffer name
- C-h f Describe a function (i.e., C-h f electric-indent-mode, C-h f fboundp)
- C-x ARR quickly switch between buffers
- You need to set mark before you can use region operation. To know more about The Mark and Region
- To move or copy a region of text in emacs, you must first "mark" it, then kill or copy the marked text, move the cu rsor to the desired location, and restore the killed or copied text. A region of text is defined by marking one end of it, then moving the cursor to the other end.
- C-@ Set the mark here
- C-SPC Set the mark where point is
- C-x-h Select the whole text
- C-w kill the region
- M-d kill forward to the end of the next word (kill-word)
- C-y yank the region
- M-w copy the region
- C-k kill the whole line (note you need to put the cursor at the very beginning of the line)
To copy text, kill it, yank it back immediately (so it's as if you haven't killed it, except it's now in the kill ring ), move elsewhere and yank it back again.
- C-x C-s save file
- C-x C-v RET reload a file (alternative way is M-x revert-buffer)
- C-/ (C-x u) undo
- C-r invoke backward search (type search word thereafter. Use C-r to repeatedly travel through the matches backward)
- C-s similar to C-r but search forward
- C-x r t insert words to multiple lines highlighted (the same thing you typed will be entered on all the lines you've selected)
- M-x clipboard-yank paste the clipboard text to emacs (useful when using emacs GUI)
- M-x clipboard-kill-region paste emacs text to clipboard
- ESC-< go to the beginning of the file
- ESC-a go to beginning of the sentence
- ESC-e go to end of the sentence
- C-a go to beginning of the line
- C-e go to the end of the line
- M-x goto-line go to the line specified
- C-e RET simulate o in vi
- C-a RET simulate O in vi
- C-Up go to the cursor location before a chunk of test pasted
- C-v page down
- M-v page up
Searching and Replacing
ESC-% (query-replace) - ask before replacing each OLD STRING with NEW STRING.
- Type y to replace this one and go to the next one
- Type n to skip to next without replacing
- Type ! to replace this one and remaining replacements without asking
- See more options in GNU manual
Esc-x replace-string replace all occurrences of OLD STRING with NEW STRING.
ESC-x list-matching-lines lists all the lines matching your pattern in a separate buffer, along with their numbers. Use "ESC-x goto-line" to go to the occurrence you're interested in.
Manage Split Windows
- C-x 2 split-window-below
- C-x 3 split-window-right
- C-x 1 delete-other-windows (unsplit all)
- C-x 0 delete-window (remove current pane)
- C-x o other-window (cycles among the opening buffers)
File Management (dired mode)
- M-x dired start view directory
- ^ go to parent dir
- g refresh dir listing
- q Quit dired mode (buffer still exists)
- RET Open the file or directory (this will open with another buffer). If you want to stick with one buffer, use a.
- o Open file in another window (move cursor to that window as well)
- C-o Open file in another window but stay on dired buffer
- + create new dir
- C-x C-f Create a new file (yes, the command is the same as opening a new file in non-dired mode)
- M-x whitespace-mode allows you to explicitly see white-space, tab, newline. Especially useful when work with python.
- M-x sort-lines allows you to sort the marked region alphabetically. Especially useful when work with lots of Java import or C #include
- C-x l count number of the lines for the file; give the current line number; list how many lines left.
When running Emacs in a terminal, you can press C-z, type the shell command and then resume Emacs with fg
How can I get Emacs to reload all my definitions that I have updated in .emacs without restarting Emacs?
You can use the command load-file (M-x load-file, then press return twice to accept the default filename, which is the current file being edited).
You can also just move the point to the end of any sexp and press C-x C-e to execute just that sexp. Usually it' s not necessary to reload the whole file if you're just changing a line or two.
M-x eval-buffer immediately evaluates all code in the buffer, its the quickest method, if your .emacs is idempotent.
You can usually just re-evaluate the changed region. Mark the region of ~/.emacs that you've changed, and then use M-x eval-region RET. This is often safer than re-evaluating the entire file since it's easy to write a .emacs file that doesn't work quite right after being loaded twice.
Shift multiple lines with TAB
Select multiply lines, then type C-u 8 C-x Tab, it will indent the region by 8 spaces. C-u -4 C-x Tab will un-indent by 4 spaces.
Switch between windows when one windows open with term
If you open two windows, and one window open a term (ie. M-x term), now you want to switch back to another window. You may find out "C-x o" may no longer work. In this case, you may want to use C-c o to switch to next window from term
Comment out multiple region
Comment out multiple lines. Highlight the region and then M-x comment-region. To undo the comment, M-x uncomment-region
Error during download request: Not Found
Happened when you try to install a package (M-x package-install). M-x package-refresh-contents to rescue.
Editing multiple lines at the same time
suppose I have the following chunk of code that I want to edit:
printf "%s=%s\n" "Database" "bool_db" printf "%s=%s\n" "Username" "admin" printf "%s=%s\n" "Password" "password" printf "%s=%s\n" "ReadOnly" "false" printf "%s=%s\n" "ShowSystemTables" "false" printf "%s=%s\n" "LegacySQLTables" "false" printf "%s=%s\n" "LoginTimeout" "0"
and I want to remove all printf "%s=%s\n" in each line. I can do the following:
- Mark the beginning of the region and invoke M-x rectangle-mark-mode (or C-x SPC) and select all the printf "%s=%s\n"
- Delete them by M-x kill-region (or C-x r k)
Instead of delete, you can use C-x r t string RET to replace rectangle contents with string con each line.
Turn on the line number on the left hand side
I find this is particularly useful when I work with gdb in emacs. It can be done with M-x linum-mode.
This is my personal emacs configuration.