unix

1. vi

• move within line: 0(begin), $(end), w(next), b(previous)
• move within file: 1G(begin), G(end), nG(line) 
• move between screen: ctrl+f(forward), ctrl+b(back), ctrl+d(forward half), ctrl+u(back half)

• u(undo) 

• edit: i(insert), x(delete), o(insert line before), O(insert line after), d0(delete from 0), d$(delete to $), dd(delete line), ndd(delete n line), yy(copy line), nyy(copy n line), p(paste),

• search: /(search forward), ?(search backward), n(next forward), N(next backward)
•  replace: :%s/text1/text2/g

• line number: ^g(show current line number and total line number), :set number, :set nonumber, :1,10y(copy line 1-10)

2. ls

• ls -altr  //a=all, l=long_format, t=sort_by_time, r=reverse_order

3. less

• F (become tail -f)
• ctrl+g (show statistics)
• v (edit)
• h (help)
• -N (display line number)
• G (go to end of file)
• g (go to start of file)

4. grep

• grep -n pattern file

5. cron

6. get information of linux machine

• primary ip address: /sbin/ifconfig -a
• OS version: uname -a
• ps -ef | grep proc_name
• hostname ip conversion: nslookup [address] [hostname]

7. ssh tunnelling
       ~/.ssh/config

       host wstasapp016
       LocalForward 50404 10.200.10.222:1521

       to test: ssh -p 50404 localhost

8. keep console busy

• prstat
• while sleep 300; do echo -ne "\a"; done &

9. sudo and su

• sudo     //ask for root permission
• su         //switch to another user
• sudo su - user  //open a login shell as user

10. shell argument

• "$@" is an array-like construct of all positional parameters, {$1, $2, $3 ...}
• "$#" is the number of positional parameters
• "$0" is the name of the shell or shell script
• -z string true if the string is null
• -n is the opposite of -z
• foo=${variable:-default}  # If variable not set or null, use default.

11. ping -c 3                               //ping with 3 packet

reference
1. setup ssh tunnel using putty
2. ssh tunnelling using config file
3. dollar sign shell variable
4. linux test command