Unix Commands with Example

List all files and directory
$ ls

List all files and directory with their detail like permission, owner and created date
$ ls
$ ls -l

List all files and directory with more option (when list is more than 1 page)
$ ls -l | more

Remove directory
$ rmdir dirname

Remove a file
$ rm filename

Remove a file without "confirmation"
$ rm -f filename

Remove a directory
$ rmdir filename

Copy source to destination
$ cp sourceFile destinationFile

Move a file from one location to another
$ mv source destination

Online manual (help) about command
$ man ls

Find a text in file and return that line
$ grep searchText fileName

Change the File/Directory Permission
$ chmod 644 fileOrDir

List the preprocessor
$ ps

Find text in List of processor
$ ps | grep STIME

Kill the process
$ kill 45555

Zip a file
$ gzip filename

Unzip a file
$ ungzip filename.zip

List who is logged on your machine
$ who

List who is on the computer in the lab
$ finger

List of History you have done recently
$ history

Print the current Date
$ date

print the calendar for September 2000
$ cal 09 2013


See how much free disk space
$ df

Set the Alias for command
$ alias newc="ls -l";

Print system usage and top resource hogs
$ top

Logout from the putty/console
$ logout
$ exit

Progressively dump a file to the screen: ENTER = one line down SPACEBAR = page down  q=quit$ more filename

Show the firest few lines of a file
$ head filename
$ head -n  filename

Show the last few lines of a file
$ tail filename
$ tail -n  filename

Search the text and store the output in file
$ grep string filename > newfile
$ grep string filename >> existfile

Finds all the files named aaa.txt in the current directory or any subdirectory tree.
$ find . -name aaa.txt

Open a file in edit mode
$ vi filename

Open file in vi editor and go to line no 101 instant
$ vi +101 filename

Show the line number in front of each line in vi editor
:set number

Go to particular line number in vi editor
:14
:100
:5

Search text "searchme" in the vi editor
:/searchme
to search next press "n" and for previous "shift+n"

Come out from vi editor
"shift+:" and press "q" and then press "enter key"

Edit modes (These keys enter editing modes and type in the text of your document.)
i  Insert before current cursor position
I  Insert at beginning of current line
a  Insert (append) after current cursor position
A  Append to end of line
o  Open and put text in a new line below current line
O  Open and put text in a new line above current line
r  Replace 1 character
R  Replace mode
<ESC> Terminate insertion or overwrite mode


Deletion of text
x   Delete single character
dd  Delete current line and put in buffer
ndd Delete n lines (n is a number) and put them in buffer
J   Attaches the next line to the end of the current line (deletes carriage return).

Cut and paste
yy Yank current line into buffer
nyy Yank n lines into buffer
p  Put the contents of the buffer after the current line
P  Put the contents of the buffer before the current line

Cursor positioning  (symbol (^ )before a letter means that the <Ctrl> key should be held down while the letter key is pressed)
^d  Page down
^u  Page up
^f   move forward one screen
^b  move backward one screen
^g  Display current line number
:n   Position cursor at line n
:$  Position cursor at end of file


Give on which server you are on
$ uname
Linux

Give your hostname
$ uname -n;
$ hostname

Kill your task
$ kill 1202255

Command displays active processes
$ ps


Display today's CPU activity
$ sar

Change the File's timing (created, access and modification time);
$ touch file.txt
If file is not exist, If will create the file

set  the access and modify timestamp
$ touch -t 06151330 f1.c;

Get file stats
$ stat file.txt

Change the owner of file/folder

$ chown vivek demo.txt

Owner of demo.text is set to vivek

Change the owner & Group of file/folder

$ chown vivek:arun demo.txt

Owner of demo.text is set to vivek
Group of demo.text is set to arun

Change the group of file/folder

$chown :ftp demo.txt

Group of demo.text is set to ftp

Change the owner of folder

$chown root /folder

Owner of /folder set to root

Change the owner of folder and its subfolder

$chown -R root /folder

Owner of /folder and its sub folder, set to root

List of user

$ w
$ who

Number of files in folder

ls -l | wc -l

Number of files in folder including dot and hidden files

ls -lA | wc -l

List the files sort by date

ls -ltr