linux basic commands for beginners and shell program with Vi editor

1. Presented by :-
U.SHANMUGARAJAN
M.SC COMPUTER SCIENCE
THIAGARAJAR COLLEGE

2. What is Linux?
Linux is the most used open source operating
system.
Everything on a Linux system can be done by
typing commands
History of Linux?
Linux was developed by Linux Torvalds.
On Octoer 5,1991, Linus announced the first
official version of Linux. Which was version 0.02.

3. What is command shell?
⇨Shell is a Program that takes commands from the
keyboard and gives them to the operating system
to perform.
⇨On most Linux systems a BASH(Bourne-Again
SHell) is the default shell.
⇨Ksh, tcsh and xsh are other shell programs
available on a Linux systems.
⇨Command prompt user’s types.
•$ - “logged in as a regular user”,
•# - “logged in as root”

4. LINUX BASIC
COMMANDS

5. A shell script is a text file contains Linux
commands.
We create shell program with any editors such as vi.
Shell scripts allow input/output operations and
manipulating variables.
The sh command used to execute shell program.
the following commands are also used in the
shell programming
1> read – read the variable from the terminal.
eg . read a
2> expr – expression.
eg . ‘expr $a + $b’
add two variables a and b. Note that expr statement
always start with ‘ and end with ‘.
we also use arithmetic operators ‘-’ , ’*’ , ’/’ , ’%’
Shell programming

6. 3> relational operators
-gt - greater than
-lt - less than
-ge - greater than or equal to
-le - less than or equal to
-eq - equal to
4> pipeline ( | )
pipeline used to combine many
commands into one.
eg . Cat $fn | tr “a-z” “A-Z”
It converts all lowercase to upper case and display.
5> cc
compiles c program.
Shell programming

7. TERMINAL

8. directory handling commands
1> mkdir – make directories
eg. $mkdir dir1
2> rmdir – remove empty directories
eg. $rmdir dir1
3> cd – changes directories
eg. $cd dir1 (change directory to dir1)
$cd (move to previous directory)
4> pwd – present working directory
eg. $pwd

9. Display file contents
1> cat – shows contents of the file
eg. $cat file1
we also use cat command for create, copy, append
the file
 cat>file1 – open new file named file1
Cat>>file1 – open file1 for append
Cat file1>file2 – The contents of file1 copied
to file2
use ctrl + d or ctrl + z for save the file.
2> tac – similar to cat but it displays
contents of the file in reverse order
eg. $tac file1

10. Display file contents
3> head – display first 10 lines of files.
syntax. $head –n filename
4> tail – display last 10 lines of files.
syntax. $tail –n filename

11. Display file contents
5> more
The more command is useful for displaying
files that take up more than one screen. More will allow
you to see the contents of the file page by page. Use
the space bar to see the next page, or q to quit.
syntax. $more [options] filename
options are
-num - sets the no of lines to be display
` -d - more prompt the user with
the message
‘[press space to continue, ’q’ to quit]’
-f - long lines are wrapped
-s - convert multiple blank line
into one line

12. Display file contents
6> less
less command similar to more, but it
provides some more options to view file.
space - ahead one full screen
ENTER - ahead one line
b - back one full screen
k - back one line
g - top of the file
G - bottom of the file
/text - search forward for text
n - repeat last search
q - quit

13. File handling commands
1> ls – List all files and folders
syntax :- ls [option]…[file]
•-a – List files include hidden files.
•-author – print the author of each file
•-B – will not list the backup file ending ~
•-l – List all files with complete details.
•-d – List directories
•-i – print index number of each file
•-s – print size of each file
•-t – sort by modification time.
•-1 – list one file per line.
We combine two or more option to display files.
Eg : ls –la – List all files with complete details include
hidden files.

14. File handling commands
2> file – It determines the file type.
3> touch – create empty files
eg 1. touch file3
4> rm – remove files or directories
syntax : rm [options] filename
-i - it confirm before delete the files
-f - (force) remove directory contain files.
(only root user use this).
eg . rm file1, rm -f some_dir

15. File handling commands
5> vi – open Visual text editor
eg. $vi file1.txt, $vi
6> sh – runs shell program
eg. $sh filename
7> cp – copy files and directories
syntax : cp source target
-r - the -r option forces recursive
copying of all files in all
subdirectories.
-i - prevents cp from overwriting
existing file
eg 1. cp sample.txt sample_copy.txt
eg 2. cp sample_copy.txt target_dir

16. File handling commands
8> mv – move or rename files or
directory
eg 1. mv source.txt target_dir
eg 2. mv old.txt new.txt
9> find – search for files in a directory
eg . find file1.txt, find –name file1.txt
10>chown – change owner of file

17. File handling commands
11>chmod – change permission of file
0 – No permission
1 – Execute
2 – write
3 – Write and Execute
4 – Read
5 – Read and Execute
6 – Read and Write
7 – All permission
syntax : chmod UGO
U – users
G – groups
O – others

18. Text Processing commands
1> sort – sort lines of text files
syntax : sort [OPTION] [FILE]
eg. sort file1 - ascending order
sort –r file1 - descending order
sort -n file2 - numeric sort
2> tr – transalate characters in one set to
corresponding characters in another
set
eg. tr 'a-z' 'A-Z' < lowercase.txt
3> echo – display a line of text
eg. echo Linux, echo $HOME

19. Text Processing commands
4> grep – print lines matching a pattern
Syntax : grep [OPTION] PATTERN [FILE]
eg. grep –i apple sample.txt
i – ignore case
o – only matching
n – print line numbers of matches
v – print lines not containing pattern
5> wc – print the number of lines, words, and
characters in files
eg. wc –l file1.txt - count no of lines in file1
wc –w file1.txt - count no of words
wc –c file1.txt - count no of character

20. Date – prints system date and time
syntax . $date [options]
eg :- Tuesday, August 23 10:20:32 IST 2016
•+ %d – Day of the months (in digits)
•+ %m – Month of the year (in digits)
•+ %y – Year (last two digits)
•+ % D – Date as mm/dd/yy
•+ %H – Hour (00 to 23)
•+ %M – Minutes (00 to 59)
•+ %S – Seconds (00 to 59)
•+ %T – Time as HH:MM:SS
•+ %a – Weekday (sun to sat)
•+ %h – Month (jan to dec)
•+ %r – Time in the AM/PM notation
Date commands

21. 1> history – prints recently used commands
eg . $history
2> clear – clear the terminal.
eg . $Clear
3> exit – exit from the terminal.
eg . $exit
4> man – get help on entered commands.
eg . $man ls – get help on the ‘ls’ command.
5> who – show who is logged into the system
eg . $who
6> whoami – show current user logged in the
system
eg . $whoami
7> passwd – change password for current user
eg . $passwd
Other Useful commands

22. 8> sudo -i – login as root user
eg . $sudo -i
9> info – display information about the commands.
eg . $info
10> cal – displays the calendar.
eg . $cal
Other Useful commands

23. Vi editor

24. Editors are mainly used for creating, deleting and
editing the files.
All systems have two standard editors, they are Ed and
Vi.
Ed allows the user for one line editing only but vi editor
allows the user to edit text of one screen at a time.
What is vi editor

25. Two modes in vi editor
1)Insert mode
In this input mode, the keyboard behaves as a
normal typewriter with the exception.
2)Command mode
In command mode, all the keys on the keyboard
become editing commands (x keys works as delete key).
Modes in vi editor

26. Text is inserted. The ‘Esc’ key ends insert mode and return to
command mode.
We enter insert mode with
 ‘i’ - insert
 ’a’ - insert after
 ‘A’ - insert at End Of Line
 ‘o’ - new line after current line
 ‘O’ - new line above current line
Insert mode

27. letters or sequence of letters interactively command vi. commands
are case sensitive. the ‘Esc’ key can end a command.
Command mode
KEYS ACTIONS
h/j/k/l Move cursor left/down/up/right
Ctrl + d Scroll down one half of a screen
ctrl + u) Scroll up one half of a screen
H (Shift + h) Move cursor to top of the page
L (shift+ l) Move cursor to bottom of the page
w
5w
Move cursor a word at a time
Move cursor 5 words ahead
b
5b
Move cursor back a word at a time
Move cursor back 5 words

28. Command mode
KEYS ACTIONS
e
3e
Move cursor to end of word
Move cursor ahead to the end of 3rd word
0
:30
Move cursor to beginning of line
Move cursor to line thirty
$ Move cursor to end of line
G Move cursor to end of file
M Mark the line on which the cursor.
i , a, A, o, O Go to insert mode
D
dd
Delete contents of line after cursor
Delete line

29. Command mode
KEYS ACTIONS
x
X
Delete character at cursor
Delete character before cursor
Y or yy Copy current line into unnamed storage buffer
p
P
Paste unnamed storage buffer after current line
Paste unnamed storage buffer before current line
J Join current and following line into one line
Ctrl – a Increment number under the cursor
Ctrl – x Decrement number under the cursor
. Repeat last command action

30. Creating a file in VI editor
If we want to edit an existing file or to create a new file with
name student , we have to give the following command.
$vi student
We also create unnamed file as follows
$vi
if we want to create hidden file then we have to give the
following command
$vi .filename
save the file by entering command line mode and type :wq

31. we save the file in vi editor by going to command mode and press‘:’.
This goes to the another mode called command line mode or last line
mode.
we save the file with following ways.
:ZZ - save changes to current file and quit.
:wq - save(write) changes to current file
and quit
:w - save changes to current file without
quitting
:w filename - save changes to a new file of name
“filename without quitting.
Saving the file

32. Closing the file
once we created the file, we exit from the vi editor by using
following steps
•go to command line mode.
•use :wq for save file and quit
•use :qa for quit all files
•use :q! for quit file without saving..