zhrc:~/linux_tutorials$
[host] [current dir]  [prompt] 

• What is “Shell”
  • After logging in, Linux/Unix starts another program called ‘shell’
  • Shell interprets commands the user types and manages their execution
    • The shell communicates with the internal part of the operating system called the kernel
    • The most popular shells are: tcsh, csh, korn, and bash
    • The differences are most times subtle
    • For this tutorial, we are using bash

pwd  [locate current path]
cd   [change to specific directory]
ls   [list files in current directory]
	-l [long list]
	-t [sort by modification time]
	-S [sort by size]
	-h [list file sizes in human readable format]
	-r [reverse the order]
*    [wildcard in unix/linux]
mkdir[make directory]
rmdir[remove directory]
cat  [dumps entire file to standard output]
less [displays file allowing forward/backward]
head [displays the top part of a file]
tail [displays last part of a file]
cp   [copying a file[
mv   [move or rename a file]
rm   [remove a file]

• File permissions

  • Each file in Unix/Linux has associated permission level
  • This allows the user to prevent others from reading/writing/executing their files or directories

  r   [read only permission]
  w   [write permission]
  x   [execute permission]
  
  -rw-rw-r-- 1 071yoon 169 Dec 20 23:12 hello.c
  
  chmod 755 hello.c
  

• Process

ps   [view processes running]
kill [terminate process]

• Input/Output Redirection (’piping’)

program_a | program_b [program_a's output becomes program_b's output]
program_a > file.txt  [program_a's output is written to file.txt]
program_a < input.txt [program-a gets its input from input.txt]

grep                  [search files in a directory for spectific string]

VIM

• Vi Editor when things go wrong

  • A common error is to accidentally leave the caps lock on when issuing commands. The vi editor is case sensitive and will not necessarily do what you want it to do if the caps lock is on.
  • Another common error is to be in the incorrect mode when typing. Sometimes we begin entering data when we are not in insert mode. Nothing will happen until we type in one of the insert mode characters (e.g. i, o, O, A, etc)

• Vi Modes

  • edit – command line mode
    • Default mode
    • Most powerful feature of vi
    • Allows for efficient navigation and editing of existing text
  • insert
    • Used to enter text into a file (exited via ESC)’
    • Multiple ways to enter this mode
    • Not efficient for navigation or editing

• Edit Mode

  • The default edit mode also has two sub modes
    • In line - where the cursor moves within the text
    • Ex commands - where the cursor moves to the bottom of the screen. ex commands are preceded with a colon (:), a forward slash (/), or a question mark (?)
  • General format for commands is ncm
    • n is an optional multiplier value
    • c is the command
    • m is an optional scale modifier
    • ex) 3dw – delete 3 special character delimited words

  Edit Mode

• Splitting and Joining LInes

  • If you wish to split a line between words, position yourself on a space between the words to be split, then use the replace (r) followed by the return key. This will replace the space with a carriage return forming a new line
  • If you wish to join or combine two lines go to the upper of the two lines to be joined, then key in the uppercase “J” for join.

  Navigation Commands

  Search Commands

  Copy/Paste Commands