Editing a File

TODO: {{#todo:Polish (11.21.13-16:58->KY)|Klint Youngmeyer|oe 4,oe 5,ky,inprogress}}

EMAC OE provides simple text editing capabilities for making changes to configuration files and scripts. Major editing tasks should be performed on a desktop system first, copying the desired files back to the target board. There are two text editors available on standard EMAC OE builds: vi and nano. vi is a very common text editor available on almost every Unix-like OS. nano is a more conventional text editor that can be easier to use for those not familiar with vi.

Using Vi

The key to using vi is understanding the two modes of operation: command mode and insert mode. Command mode is used for navigating the text, search and replace, pasting, saving, and running other commands. Insert mode is used for simply inserting text into the document. The editor will start in command mode. To switch from command mode to insert mode, type "i". To switch from insert mode to command mode, press ESC. Any keys pressed after switching to command mode will be interpreted as vi commands. Some of the most important commands are those for saving and exiting, such as :wq to save and exit. See Table 5 below for a description of some common vi commands.

Table 5: Common Vi Commands
Command	Description
:wq	Save changes and exit
:q!	Discard changes and exit
:q	Exit only if no unsaved changes
x	Delete character
dd	Delete current line
yy	Yank (copy) current line
p	Put (paste) after position
:%s/string/replace/g	Replace all occurrences of "string" with "replace"

To open a file using vi simply type the command vi followed by the file name. For example, to edit the network interfaces configuration, you would run the command:

root@emac-oe:~# vi /etc/network/interfaces

Using Nano

Using nano can be easier to get used to for someone who is not accustomed to using vi. After opening a file with nano, the available commands for working with the file will be displayed at the bottom of the screen as shown below:

^G Get Help     ^O WriteOut     ^R Read File    ^Y Prev Page    ^K Cut Text     ^C Cur Pos
^X Exit         ^J Justify      ^W Where Is     ^V Next Page    ^U UnCut Text   ^T To Spell 

For example, to save the file, enter Ctrl+O. To exit, type Ctrl+X. The nano editor is always in insertion mode so any keys typed that are not part of a control sequence will be placed in the file as text. You do not need to press any escape code to switch between entering text and commands as is required with vi. To edit a file with nano, pass the name of the file as an argument to the nano command. For example:

root@emac-oe:~# nano /etc/network/interfaces