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# HISTORY:
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!NUMBER - execute command <number>
!! - repeat last command
!xyz - repeat last command starting with xyz
!xyz:p -print last command starting with xyz
!$ - repeat the last argument of the last command(ex vim !$)
!* - repeat all arguments of the last command (echo !*)

^error^correction - replace first occurance of a with b in the last command and execute it
[root@master salt]# echo one tvo three
one tvo three
[root@master salt]# ^tvo^two
echo one two three
one two three

GET  EXACT ARGUMENT
!:1 - get first argument
!:1-2 - get first and second argument
!:2-$ - get second to last arguments

:s substitute first occurance of the string
EX. !!:s/confih/config
:gs substitute all occurance of the string
EX. mroe /etc/hosts;more /etc/hostname
!:gs/mroe/more
CTRL+SHIFT+A - comment out current line

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# MOVES:
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^w erase word
^u erase from here to beginning of the line (I use this ALL the time.)
^k erase from here to beginning of the line (I use this ALL the time.)
^a move the cursor to the beginning of the line
^e move the curor to the end of the line

alt+[b,f] - move cursor back(forward) one word
alt+t - swap two words

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# Word Modifiers
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:h - Remove a trailing file name component, leaving only the head.
:t - Remove all leading file name components, leaving the tail.
:r - Remove a trailing suffix of the form .xxx, leaving the basename.
:e - Remove all but the trailing suffix.

EX: 
cat /var/log/messages
cd !$:h  - 
!-5:t

GET  EXACT ARGUMENT
!:1 - get first argument
!:1-2 - get first and second argument
!:2-$ - get second to last arguments

:s substitute first occurance of the string
EX. !!:s/confih/config
:gs substitute all occurance of the string
EX. mroe /etc/hosts;more /etc/hostname
!:gs/mroe/more
CTRL+SHIFT+A - comment out current line

CTRL+X,CTRL+E - open current command in $EDITOR

# COUNT output as a file
<()
diff <(grep somestring file1) <(grep somestring file2)


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# REGEXP
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To test RegExp in console, you can use following trick - let grep read from stdin, and use option -o to show only matching.
For example, to test RegExp which matches only lines with 8 or 9 at the end, execute:

grep -oE '.*(8|9)$'

Grep connects to stdin, and you can type any line you'd line. If line matches RegExp, you will receive a highlighted matched part