Linux Command Line

[Lab mission]

(Chapter1) - What Is The Shell?

1.date

display the current time and date

2.cal

display current month calendar

3.df

display current amount of free space on your disk

4.free

display free memory

(Chapter2) - Navigation

1.pwd (현재작업폴더)

print name of current working directory

2.cd (폴더이동)

change directory

3.ls (폴더의 내용물 리스트)

listing the contents of a directory

ls -a : list all file
ls -l : display result in long format

(Chapter3) - Exploring The System

1.file

print a brief description of the file’s contents

2.less

view the contents of the file. To exit less

(Chapter4) - Manipulating Files And Directories

1.cp (복사)

copy files and directories

cp -a : copy the files and directories and all of their attributes, including 	
	    ownerships and permissions.
cp -r : Recursively copy directories and their contents.

2.mv (이동)

move/rename files and directories

3.mkdir (폴더만들기)

create directories

4.rm (삭제)

remove files and directories

rm -i : Before deleting an existing file, prompt the user for confirmation.
rm -r : Recursively delete directories. This means that if a directory being   
        deleted has subdirectories, delete them too. To delete a directory, this 
        option must be specified.
rm -f : Ignore nonexistent files and do not prompt. This overrides the interactive 
        option.

5.ln (링크만들기)

create hard and symbolic links

To create a hard link : ln file link
To create a symbolic link where "item" is file or directory : ln -s item link

hard link

symbolic link

(Chapter5) - Working With Commands

1.type

Indicate how a command name is interpreted

type command

2.which

Display which executable program will be executed

3.help

Get help for shell builtins

4.man

Display a command’s manual page

5.info

Display a command’s info entry

7.whatis

Display a very brief description of a command

8.alias

Create an alias for a command

alias test='cd java_src; ls; pwd'

(Chapter6) - Redirection

1. cat

Concatenate files

*Pipelines

command1 | command2 : the standard output of one command can be piped into the  
                      standard input of another.

2. sort

Sort lines of text

3. grep

Print lines matching a pattern

grep pattern [file....]

4. wc

Print newline, word, and byte counts for each file

5. head

Output the first part of a file

6. tail

Output the last part of a file

(Chapter7) - Seeing The World As The Shell Sees it

1. echo

Display a line of text

Arithmetic Expansion

echo $((2 + 2))
4
$((expression))

<Operator Description>
+ Addition - Subtraction 
* Multiplication 
/ Division 
(but remember, since expansion only supports integer arithmetic, results are integers).
% Modulo, which simply means, “ remainder.”
** Exponentiation

(Chapter8) - Advanced Keyboard Tricks

1.clear

Clear the screen

(Chapter9) - Permissions

1. id

Display user identity

2. chmod

Change a file’s mode

3. sudo

Execute a command as another user (superuser privileges가 필요할 때 super user로 접근)!

4. passwd

Change a user’s password

#(Chapter10) - Processes

1. ps

Report a snapshot of current processes

2. top

Display tasks

3. jobs

List active jobs

4. kill

Send a signal to a process

kill [-signal] PID...

5. shutdown

Shutdown or reboot the system

sudo reboot 
sudo shutdown -h now

6. pstree

Outputs a process list arranged in a tree-like pattern showing the parent/child relationships between processes.