This chapter is from the book
This chapter is from the book
This chapter is from the book
Editing Files with vim
Managing Linux often means working with files. Most things that are configured on Linux are configured through files. To complete administrative tasks, you often need to change the contents of a configuration file with a text editor.
Over the years, many text editors have been created for Linux. One editor really matters, though, and that is vi. Even if some other text editors are easier to use, vi is the only text editor that is always available. That is why as a Linux administrator you need to know how to work with vi. One common alternative is vim, or “vi improved”; it is a complete rewrite of vi with a lot of enhancements that make working with vi easier, such as syntax highlighting for many configuration files, which makes it easy to recognize typing errors that you have made. Everything that you learn in this section about vim works on vi as well.
An important concept when working with vim is that it uses different modes. Two of them are particularly important: command mode and input mode. These modes often cause confusion because in command mode you can just enter a command and you cannot edit the contents of a text file. To change the contents of a text file, you need to get to input mode.
The challenge when working with vim is the vast number of commands that are available. Some people have even produced vim cheat sheets, listing all available commands. Do not use them. Instead, focus on the minimal number of commands that are really important. Table 2-4 summarizes the most essential vim commands. Use these (and only these) and you’ll do fine on the RHCSA exam.
Table 2-4 vim Essential Commands
vim Command |
Explanation |
|---|---|
Esc |
Switches from input mode to command mode. Press this key before typing any command. |
i, a |
Switches from command mode to input mode at (i) or after (a) the current cursor position. |
o |
Opens a new line below the current cursor position and goes to input mode. |
:wq |
Writes the current file and quits. |
:q! |
Quits the file without applying any changes. The ! forces the command to do its work. Add the ! only if you really know what you are doing. |
:w filename |
Writes the current file with a new filename. |
dd |
Deletes the current line and places the contents of the deleted line into memory. |
yy |
Copies the current line. |
p |
Pastes the contents that have been cut or copied into memory. |
v |
Enters visual mode, which allows you to select a block of text using the arrow keys. Use d to cut the selection or y to copy it. |
u |
Undoes the last command. Repeat as often as necessary. |
Ctrl-r |
Redoes the last undo. (Cannot be repeated more than once.) |
gg |
Goes to the first line in the document. |
G |
Goes to the last line in the document. |
/text |
Searches for text from the current cursor position forward. |
?text |
Searches for text from the current cursor position backward. |
^ |
Goes to the first position in the current line. |
$ |
Goes to the last position in the current line. |
!ls |
Adds the output of ls (or any other command) in the current file. |
:%s/old/new/g |
Replaces all occurrences of old with new. |
Now you know the most essential commands for working with vim. Exercise 2-5 gives you the opportunity to test them.