4 editing files and emacs

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4 Editing files and Emacs Editing files The Emacs editor

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4 Editing files and Emacs. Editing files The Emacs editor. Editors. Editors are used to create files of text and to modify their contents You need an editor for sending email, writing programs and many other tasks - PowerPoint PPT Presentation

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Page 1: 4 Editing files and Emacs

4 Editing files and Emacs

Editing filesThe Emacs editor

Page 2: 4 Editing files and Emacs

EditorsEditors are used to create files of text

and to modify their contentsYou need an editor for sending email,

writing programs and many other tasksThere are many different editors - vi, ed

and emacs are common UNIX examplesThere are different styles of editor - e.g.

line editors and text editorsThey are not the same as word

processors which are concerned with printed documents (fonts, sizes, etc.)

Page 3: 4 Editing files and Emacs

The Emacs Editor

A powerful editor, available on most UNIX systems

It’s a text editorComplex and extensible - we will

only explore a fraction - see tutorial and on-line help facilities for more

Page 4: 4 Editing files and Emacs

Emacs conventions

Frequent use of the control and meta keys control key usually marked control or ctrl the meta key is usually marked alt

The notation C-x means hold down the control key and simultaneously press the x key (was ^X in previous lectures)

M-y means hold down the meta (alt) key and simultaneously press the y key

If the alt-y combination is taken by the host operating system (for example Windows), you can press the escape (esc) key, release it, and then press the y key

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Mini-buffer

Status line

Edit window

Page 6: 4 Editing files and Emacs

Starting and quittingFrom the UNIX prompt type emacs or

emacs filenameThe emacs screen is divided into three

parts edit window - large part where the contents

of the file are displayed status line - name of file, how far through

you are and whether it needs saving minibuffer - where commands are entered

C-x C-c to quit (of course). You may be prompted to save files

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Moving around the fileYour current position in the file is

shown by the cursorMost basic movement is one

character or line at a time use the arrow keys or

C-b backward (left) one characterC-f forward (right) one characterC-p previous line (up one

character)C-n next line (down one character)

Scrolling happens as necessary

Page 8: 4 Editing files and Emacs

Can also move in steps of a word, sentence, paragraphs and screen

M-f forwards one wordM-b backwards one wordC-a start of current lineC-e end of current lineM-a start of current sentenceM-e end of current sentenceC-v scroll down one screenM-v scroll up one screenM-< move to start of fileM-> move to end of file

C-l refreshes the screen and centers the cursor.

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Inserting and deleting text

To insert text, position the cursor and type

Type RETURN to enter a new line, otherwise the line will wrap around

DEL deletes the character before the cursor and C-d the character after the cursor. Hold down for repeated operation

M-del and M-d deletes whole words

Page 10: 4 Editing files and Emacs

C-k deletes from cursor to end of line. A further C-k deletes the new line character

Mark and then delete a whole area: C-SPACE at start and move cursor to end. Make sure you have “Active Region Highlighting”

ticked to see the marked region in color! C-w to delete the marked out region M-w copies the area without deleting it.

Commands that remove more than one character at a time save the text. It can be yanked back with C-y Another C-y to yank back another copy M-y to yank back next previously deleted text

Can use C-w and C-y to move text around

Page 11: 4 Editing files and Emacs

File handling

Need to be able to load and save files

C-x C-f finds and loads a filePrompts for the pathname in the

minibufferType the name and press RETURNUse TAB for filename completionFile is either loaded or created

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Changes made on screen are not immediately made to the file, they are made to a copy called the buffer

Have to explicitly write them back by saving, C-x s (all files) C-x C-s (current file) (answer y and n to prompts)

Can have more than one file open at a time. C-x C-f also switches between buffers if we give the name of an open buffer.

C-x b swaps to the previous buffer Save frequently - work will be lost if emacs or

the system crashes Previous version may be backed up in filename~

Page 13: 4 Editing files and Emacs

Undoing mistakes

C-x u, C-_, and C-/ undo the previous command

Repeating the undo command takes you further back through the editing history

Page 14: 4 Editing files and Emacs

SearchingNeed to search for text in a large fileIncremental search

type C-s to search forward. Type C-r to search backwards Or enter command M-x isearch-forward

or M-x isearch-backwards in the minibuffer (use TAB for command completion)

you can delete the last character in the search string

C-g to quit at any time (this works for any command!)

Page 15: 4 Editing files and Emacs

Replacing strings

Change all occurrences of one string of text with another type M-x and enter query-replace Or type M-% enter search and target strings type y or n at each prompt. ! to replace all use replace-string to avoid the prompting

M-x then spell-buffer for the spell checker

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Windows

Can divide the edit window into smaller sub-windows, each with a different document

C-x 2 split horizontallyC-x 3 split verticallyC-x 1 make current window the

full windowC-x o move cursor to the next

window

Page 17: 4 Editing files and Emacs

Modes

Modes configure emacs for different kinds of editing, controlling wrap-around and indenting M-x then mode name fundamental-mode text-mode (gives automatic text wrapping) c++-mode

May guess mode from the filename suffix

Use TAB for autocompletion

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Help and the tutorial

C-h for top level help menuC-h C-h to find out what each

menu option meansC-h t for the on-line tutorialA cheatsheet with most of the key

combinations in this lecture is in the module folder

Page 19: 4 Editing files and Emacs

Coursework 1

Deadline: 10th April 4PM.Covers the first three lectures (and

the revision lecture)It mentions one simple command

we haven’t seen. You’ll have to find out how it works.

Page 20: 4 Editing files and Emacs

Next Lecture

UNIX processes How to list them How to prioritise them How to schedule them Parent and Child processes

Signals What are they for? Types of signal