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LINUX TUTORIAL

1

LINUX
TUTORIAL

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Table of Contents
1.

WHAT IS LINUX? .............................................................................................................................................................. 4
1.1.

History of UNIX .......................................................................................................................................................... 4

1.2.

History of LINUX ....................................................................................................................................................... 4

1.3.

Why LINUX/UNIX .................................................................................................................................................... 4

1.4.

Layers of LINUX/UNIX ........................................................................................................................................... 5

2.

GETTING STARTED ....................................................................................................................................................... 7

3.

LINUX COMMANDS ....................................................................................................................................................... 8
3.1.

Control Keys ................................................................................................................................................................ 8

3.2.

Getting Help ................................................................................................................................................................. 8

3.3.

LINUX Command Options ........................................................................................................................................ 9

3.4.

LINUX Commands ................................................................................................................................................... 10
3.4.1. Basic File Commands ........................................................................................................................................ 10
3.4.2. Display Commands ............................................................................................................................................ 16
3.4.3. File Permissions .................................................................................................................................................. 20
3.4.4. System Resource Commands ........................................................................................................................... 22
3.4.5 List of User Commands ..................................................................................................................................... 28
3.4.6 List of Disk Space Commands .......................................................................................................................... 31

4.

5.

FILE SYSTEM .................................................................................................................................................................. 32
4.1.

Directories in LINUX ............................................................................................................................................... 33

4.2.

Commands in File System ....................................................................................................................................... 34

4.3.

Commands for Showning File Details .................................................................................................................. 36

SHELL ................................................................................................................................................................................. 44
5.1.

Built-in Commands ................................................................................................................................................... 44

5.2.

Special Commands ................................................................................................................................................... 44
5.2.1Piping ....................................................................................................................................................................... 45
5.2.2 Command Seperator ............................................................................................................................................. 45
5.2.3Alias ......................................................................................................................................................................... 46

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3

SHELL SCRIPTING........................................................................................................................................................ 47
6.1.

Scripting ...................................................................................................................................................................... 47

6.2.

Utilities ........................................................................................................................................................................ 47
6.2.1. Sort ......................................................................................................................................................................... 47
6.2.2. Join ........................................................................................................................................................................ 47

6.3.

Shell Variables ......................................................................................................................................................... 48
6.3.1. Scalar Variables .................................................................................................................................................. 48
6.3.2 Array Variables ................................................................................................................................................... 48

7.

SHELL PROGRAMMING IN BOURNE SHELL ................................................................................................. 49
7.1.

Shell Scripting in Bourne ......................................................................................................................................... 49

7.2.

Shell Variables ........................................................................................................................................................... 49

7.3.

Arithmetic Expansion ............................................................................................................................................... 50

7.4.

Control Commands ................................................................................................................................................... 50

7.5.

Fille Descriptors ........................................................................................................................................................ 52

7.6.

Text Processing Commands .................................................................................................................................... 53

7.7.

File Archiving, Compression and Conversion .................................................................................................... 55

7.8.

Applications ........................................................................................................ Error! Bookmark not defined.5

7.9.

Editors .................................................................................................................. Error! Bookmark not defined.7
7.9.1 vi Editor ................................................................................................................................................................ 57
7.9.1.1. Cursor Movement .................................................................................................................................. 58
7.9.1.2. Inserting of Text .................................................................................................................................... 58
7.9.1.3. Deleting of Text ..................................................................................................................................... 58
7.9.1.4. File Manipulation .................................................................................................................................. 58
7.8.1.5. To see Multiple Files ............................................................................................................................. 59

8.

KEY BOARD SHORTCUTS ......................................................................................................................................... 60

9.

NETWORKING IN LINUX .......................................................................................................................................... 61
9.1.

Addresses .................................................................................................................................................................... 61

9.2.

Network Commands ................................................................................................................................................. 61

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1. What is Linux?
1.1 History of UNIX
v UNIX is an Operating System (OS).
v UNIX was developed about 40 years ago i.e., 1969 at AT&T Bell Labs by Ken Thompson
and Dennis Ritche.
v It is a Command Line Interpreter.
v It was developed for the Mini-Computers as a time sharing system.
v UNIX was the predecessor of LINUX.

1.2 History of LINUX
v LINUX was created by Linus Torvalds in 1991.
v LINUX is a open source.
v LINUX is a variant of UNIX.

1.3 Why LINUX/UNIX?
v LINUX is free.
• Can view and edit the source code of OS
v It is fully customizable.
v Most Important Feature is Stability
• 30Years to get the bugs
• Important in shared environments and critical applications
v LINUX has better security structure.
v High Portability
• Easy to port new H/W Platform
• Written in C which is highly portable

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1.4. Layers of LINUX/UNIX
v LINUX/UNIX has three most important parts.
They are Kernel, Shell and File System

Fig 1.1 Layers of Linux

1.4.1 Kernel:
v Kernel is the heart of the operating system.
v It is the low level core of the System that is the interface between
applications and H/W.
v Functions
• Manage Memory, I/O devices, allocates the time between user and
process, inter process communication, sets process priority

1.4.2 Shell:
v The shell is a program that sits on the as an interface between users and kernel
v It is a command interpreter and also has programming capability of its own.
v Shell Types
• Bourne Shell (sh) (First shell by Stephen Bourne)
• C Shell(sh)
• Korn Shell (ksh)
• Bourne Again Shell(bash)

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1.4.3 File System:
v Linux treats everything as a file including hardware devices. Arranged as a

directory hierarchy.
v The top level directory is known as “root (/)”.

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2. Getting Started
v Use username and password for login.
v Login is user unique name.
v Linux is case sensitive.
v Password can be changed by the user at any time.

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3. LINUX Commands
v Commands tell the operating system to perform set of operations.
v The syntax form of the commands are
Command options arguments

3.1Control Keys:
v Control Keys performs special function.
v The control keys used in LINUX are
^S à Pause Display
^Qà Restart Display
^Cà Cancel Operation
^Uà Cancel Line
^Dà Signal end of file
^Và Treat following control character as normal character

3.2Getting Help:
v In LINUX/UNIX whenever you need help with a command type “man” followed by
the command name.
v The Syntax is
man [options] command
v Common options are
-M à Keyword path to man pages.
-k à Keyword list command for all keyword matches.
v We can use help command also.
command - -help

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Fig. 3.1man command

3.3LINUX Command Options
The common command options used in LINUX are
-a à lists all the files and directories, even hidden ones which are preceded by (“.”)
-l à lists the size, creation date and permissions about all the files and directories in
the current directory
-d à lists the directory
-c à don’t create file if it already present
-f à force
-k à block Size
-R à recursive
-t à type
-V à version.

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3.4 LINUX Commands:
3.4.1Basic File Commands:
Command: ls
v To lists the files in the current directory use “ls”.
v ls has many options:
-l à long list (Displays lots of info)
-t à lists by modification date
-S à lists by size
-h à lists file sizes in human readable format
-r à Reverse the order
-a à Lists all hidden files
-F à Lists files of Directory
v Type “man ls” in the terminal for more options
v Options can be combined as: “ls –ltr”
v ll (double l) can be used to list all files in long format

Fig. 3.2 ls command

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Command: cd
v cd dir_name
Moves to directory called dir_name
v cd ~
Moves to your home directory
v cd ..
Moves one level hierarchy down from the current directory
v cd .. /../
Moves two level hierarchy down from the current directory
v cd Moves to your previous directory

Fig. 3.3 cd command

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Command: mkdir
v To create a new directory use “mkdir”.
v Syntax: $ mkdir directoryname
v $mkdir –p dir1/dir2/dir3.
It will create the directory tree.dir3 will created under dir2 and dir2 is created
under dir1.
v $ mkdir dir5
$ cd !$ .
It will point the location of dir5.
v $ mkdir dir5; cd dir5.
It will create dir5 first and then point the location of dir5.Concatenation of
above two commands.(‘;’ called command separator, explained later)

Fig. 3.4 mkdir command

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Command: cat
v $ cat filename
It will display the contents of the file filename.
v $cat >flie1
Success is not a destination.
[Ctrl+d]
$
• The above command creates the file called file1 and you can enter the text
there only. After finishing your work press Ctrl+d (Press Enter after the
last line of your character to denote the end of the file).
• If file1 already exists then it over writes the contents of the file1.
• ”>” is called Redirection Operator.
v $cat >>flie1
It’s a progressive journey.
[Ctrl+d]
$ cat flie1
$ Success is not a destination. It’s a progressive journey.
• The above command is used to append more text to already existing file.
v $cat flie1 file2 >file3
• The above command is used to write contents of the file1 and file 2 into
file3

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Command: cp
v Syntax $ cp [options] Source Destination
Copies Source into Destination
v $ cp file1 file2
Copies file1 into file2
v $ cp -prf /home/kacper/ /hdd/backup/
Copies all files, directories, and subdirectories inside kacper into backup
v Options:
-i
à interactive
prompts before overwriting
-f

à force
if an existing destination file cannot be opened, remove it and try again

-p

à preserve
preserve mode, ownership, and timestamps

-R, -r à recursive
copy directories recursively
-u

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à update
copy only when the SOURCE file is newer than the destination file or
when the destination file is missing

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Command: mv
v
v
v
v
v

To move a file to different location use “mv”.
$ mv [options] Source Destination
mv can also be used to rename a file.
$ mv filename1 filename2 (Rename file)
$mv /home/kacper/top.v /hdd/kacper/backup/
Moves the top.v into backup directory
v $mv -i /home/kacper/top.v /hdd/kacper/backup/
Asks before over writing the file

Command: rm
v
v
v
v

To remove a file use “rm”.
Syntax: $ rm filename
rm –i * prompts you before deleting a file. The “i” stands for interactive.
rm –rf * recursively removes all files and subdirectories in your current directory,
without prompting to delete files.
v Be very careful, deletions are permanent in UNIX/LINUX.

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Command: rmdir
v To remove a empty directory use “rmdir”.
v Syntax :$ rmdir directoryname

Command: pwd
v To find your current path use “pwd”.
v Syntax: $ pwd
Displays the present working directory

3.4.2Display Commands:
Command: less
v
v
v
v

“less” displays a file, allowing forward/backward movement within it.
Use “/” to search for a string in the file.
Press “q” to quit.
Syntax:$ less [options]filename
Options
-c
à clears the screen before displaying.
+n
à starts printing from nth line

Fig. 3.5 less command

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Command: head
v
v
v
v

“head” displays the top part of a file.
By default it shows the first 10 lines.
-n allows you to change the number of lines to be shown.
Syntax:$ head [options]filename

v Example: “head –n50 file.txt” displays the first 50 lines of the file.txt
$head -18 filename
Displays the first 18 lines of the file called filename.

Fig. 3.6 head command

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Command: tail
v Displays last 10(by default) lines of a file.
v Same as head command.
v Syntax:$ tail filename
Displays the last 10 lines from the ending
$tail -12 filename
Displays the last 12 lines from the ending

Fig. 3.7tail command

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Command: more
v Read files and displays the text one screen at a time.
v Syntax:
$ more [options] filename
Options :
-c à clears the screen before displaying.
-n à displays the first n lines of the file. We can also see next lines by
pressing [Enter]
+n à displays the lines from nth line.

Fig. 3.8 more command

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3.4.3 File Permissions:
v Each file in UNIX/LINUX has an associated permission level.
v This allows the user to prevent others from reading/writing/executing their files or
directories.
v Use “ls –l filename ” to find permission level of that file.
v The permission levels are





“r” means “read only” permission.
“w” means “write” permission.
“x” means “execute” permission.
In case of directory, “x” grants permission to list directory contents.

Command: chmod
v If you own a file, you can change its permissions with “chmod”.
v Syntax:
$ chmod [user/group/others/all]+[permission] filename

Command: chgrp
v Change the group of the file.

Command: chown
v Change the owner of the file.
Example 1:
chmod 7
7
7
filename
user group others
è Gives user, group and others r, w, x permissions

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Example 2: chmod 750 filename
è Gives the user read, write and execute.
è Gives group members read and execute.
è Gives others no permissions.
è Using numeric representations for permissions:
r = 4; w = 2; x = 1; total = 7

Fig. 3.9 File Permissions

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3.4.4 System Resource Commands:
Command: date
v Reports the current date and time.
v Syntax:$ date

Fig. 3.10 date command

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Command: chsh
v Change the user’s login shell.
v Syntax: chsh (passwd –e/ -s)
v

Fig. 3.11chsh command

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Command: passwd
v Set or change your password.
v Syntax:$ passwd [options]

Fig. 3.12passwd command

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Command: ps
v To view the processes that you are running.
v Syntax: ps [options]
v Example
$ ps –u username
Displays the process of the specified user
$ps –aux
Displays all processes including user and system process
$ps –aux |grep “user1”
Displays all the process of user1

Fig. 3.13ps command

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Command: top
v To view the CPU usage of all processes.
v Syntax:$ top

Fig. 3.14 top command

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Command: kill
v A user can only start/kill the process that have the user id.
v kill is used for terminating the process.
v Syntax: $ kill [-signal] [process id]
$kill -9 process id
It gives the guarantee that the process would be killed. It is stronger signal
called SIGKILL
$ kill 0
Terminates all current process except your shell

Fig. 3.15 kill command

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3.4.5 List of user commands:
Command: who
v Lists all users currently on system.
v Syntax: $ who

Fig. 3.16 who command

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Command: who am i
v Reports the details about the command user.
v Syntax:$ who am i

Fig.3.17 who am i command

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Command: whoami
v Reports the username of the command user.
v Syntax:$ whoami

Fig. 3.18 whoami command

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3.4.6 List of disk Space commands
v $ du [options] [directory or file]
Gives the amount of disk space in use
v $du –sh file/dir
Gives the size of the file/dir
v $df -h or df –kh
Gives the Available space mounted on file System
v $free
Gives the free space

Fig 3.19 disk space commands

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4 File System
v Linux files are organized by a hierarchy of labels, commonly known as hierarchy
structure.
v There are three types of files.
v They are
Ø Regular Files:
§ This contains a sequence of bytes that generally corresponds to code or
data.
Ø Directory Files:
§ Directory file contains an entry for every file and subdirectory that it is
placed.
Ø Device Files:
§ These files correspond to the printers or other devices connected to the
system.

Fig. 4.1File System

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4.1 Directories in LINUX:
v

Directory: /bin
/bin contains the binaries which are needed to run LINUX.

v

Directory: /boot
/boot has all the files required for booting LINUX on system.

v

Directory: /dev
/dev has the devices for all the files.

v

Directory: /etc
/etc contains the configuration files of the various software.
Normally no one touch this directory.

v

Directory: /home
/home is like My Documents in Windows.
This contains the username as the sub directory.

v

Directory: /lib
/lib contains the libraries required fo r the system files.

v

Directory: /lost+found
/lost+found contains the files which are damaged or which are not linked to
any directory
These damages are due to the incorrect shutdown.

v

Directory: /mnt
This is the directory in which we mount the devices and other file systems.

v

Directory: /opt
Here the optional softwares are installed.

v

Directory: /root
The directory for the user root

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4.2 Commands in File System:
Command: fgrep
v fgrep is used to search for exact strings in text files.
v The fgrep contains various options.
v They are
è -i for ignore case.
è -v for displaying the lines that don’t match.
è -n for displaying the line number with the line where the match
was found.
v Syntax:$ fgrep [options] textfiles

Command: find
v The find command is used to find the files in the hard drive.
v By using the find command we can find the files by date and also we can
specify the range of times.
v Example: $ find /user/bin –type f –atime +100 –print
v We can also use find to show the postscript files in our directory.
v Example: $ find *.pl
v Syntax :$ find directory [options] [actions]

Fig. 4.2find command

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Command: locate
v
v
v
v

The locate command is much faster than the find command.
Finding a file using locate is faster when compared to the find command.
The files are printed with the path if we use this command.
Syntax:$ locate [search string]

Fig. 4.3 locate command

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4.3 Commands for showing file details:
Command: wc
v $ wc[options] filename .
Gives the number of lines, words and characters in a file called filename
v wc –l filename
Gives the number of lines
v wc –w filename
Gives the number of words
v wc –c filename
Gives the number of characters

Fig. 4.4 wc command

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Command: sort
v It prints the lines of the file in sorted order.
v Syntax:
$ sort filename

Fig. 4.5 sort command

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Command: uniq
v Used to print the file by removing duplicate adjacent lines.
v Syntax: uniq filename
v Ex: $ uniq text
v uniq –u filename
--unique
Prints the only unique lines
v uniq –d filename
--repeated
Prints the only duplicate lines
v uniq –c filename
--count
Prints the number of times each line occurred
v sort file | unique
Removes the duplicate entries when you are trying to merge two files. First it
will sort the file and then passed to uniq (| is called pipe, explained later section)

Fig 4.6 uniq command

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Command: touch
v Used to create empty file.
v Syntax :$touch file2
It will create the file called file2 of size zero bytes, if file2 doesn’t exist.
v Used to change the time stamps.(i.e. dates and times of the recent modification or
access)
v For example to change the last access time of file6 to 10:10 a.m. May 2, 2009, it can
be done in the following way.
$ touch –d ‘2 May 2009 10:10’ file6.
It will change the time stamp of the file6.It can be verified by the following way.
$ ls –l file6
-rw-r--r-- 1 root root 120 May 2 2009 file6
$ touch –t 08021130 file7
It can change the date and time. The expression 08021130 denotes the
Month, day, hour and minute. In general the expression type is MMDDhhmm.

Fig 4.6 touch command

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Command: tee
v Sends the output in two directions at a time
v Syntax: tee [options ] filename .
v Ex : $ls –l |tee file2
It will list all the files in the current directory and as well stores in the file called
file2.

$ls –l |tee –a file2
It will append the list to file2.

Fig 4.7 tee command

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Command: cmp
v This cmp command tests whether two files are identical and reports position of first
character.
v It shows 0 if they are identical, otherwise it shows 1.
v Syntax:
$ cmp filename1 filename2

Fig. 4.8 cmp command

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Command: find
v This command is used to find the location of a file.
v Syntax: find path selection criteria
v Ex: $find . –name “top.v”
It will look for top.v in the current directory.
$find . –type d
Finds all directories.
$find /home/kacper -type d
Finds all directories and subdirectories inside the kacper
$find /home/kacper -type d -name “.*”
Finds all hidden directories
$find . –type f
Finds all normal files
$find . –type f –name”.*”
Finds all hidden files

Fig. 4.9 find command

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Command: diff
v $ diff filename1 filename2
It compare two files for differences .
v $vimdiff filename1 filename2 or sdiff filename1 filename2
It will display the two files side by side

Fig. 4.10vimdiff command

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5. SHELL
v
v
v
v
v
v
v
v
v
v

The shell is a unique and multi- faceted program.
The shell is a command interpreter and a programming language in built.
There are various types of shells.
The commonly used shells are Bourne Shell (sh), C Shell (csh or tcsh) and Korn Shell
(ksh).
The first shell is Bourne Shell (sh).
These shells have their own built in functions which allow for the creation of the shell
scripts.
Through the shell, user interacts with the kernel.
The prompt for the Bourne shell is $ or # for the root user and the prompt for the C
shell is %.
We can start shell and exit by using the CTRL+D.
All shells use different syntax and provide different services.

5.1 Built-in Commands:
cd
echo
eval
case
exec
exit
export
for
if
set
test
trap
unmask
unset
wait
while

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Change the working directory.
Writing the standard output in string.
Evaluating the given data.
Case conditional loop.
Executing the given command.
Exiting the current shell.
Share the specified environment variable with other shells.
For conditional loop.
If conditional loop.
Set variables for the shell.
Evaluate the expression as true or false.
Trap for a typed signal and execute commands.
Set a default file permission mask for new files.
Unset shell variables.
Wait for a specified process to terminate.
While conditional loop.

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5.2 Special Commands:
Command: mount and unmount windows
v Syntax to mount windows in LINUX:
$ mount /dev/hda1/home/username/directoryname
v Syntax to unmount windows in LINUX:
$ unmount /dev/hda1/home/username/directoryname

Command: mount and unmount pen drive (USB)
v Syntax to mount pen drive (USB) in LINUX:
$ mount /dev/sda1/home/username/dire ctoryname
v Syntax to unmount pen drive (USB) in LINUX:
$ unmount /dev/sda1/home/username/directoryname

5.2.1 Piping:
v
v
v
v

Programs can output other programs. This process is called piping.
Pipe (‘|’) used to connect commands to create a pipeline
Output of program1 can be used as input of program2 using pipes.
Syntax:
$ ls |wc –l
It will display number of files in the current directory. Here, the output of ls is
passed directly to input of wc, and ls is said to be piped to wc.
$cat file | head | tail -6

It will display last six lines of first of first ten lines. Like this we can connect
number of commands

5.2.2 Command Separator:
v Semi colon (‘;’) used to execute commands one after another.
v Syntax: $ comand1 ; comand2
v Ex: $ls –l ; cat file
It will lists all files first and then displays the contents of file called file.

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5.2.3Aliases:
v Aliases are used to define shorthand for complex commands.
v The alias can be set and it be removed by using the unalias command.
v Syntax:
$ alias name command
$ unalias name command
v Example: $ alias cls clear
$ unalias cls clear

Fig. 5.1Alias

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6. Shell Scripting
6.1Scripting:
v Shell scripting provides the solution to a task as a combination of the UNIX utilities.
v Here pipes and file handling are used to connect subtasks.
v Scripting uses advanced utilities such as sort, cut, paste, join, grep, sed, awk, etc.
6.2 Utilities:

6.2.1Sort:
v Sort records in file and the order default is ascending dictionary order.
v The available options for sort are
-t
-k
-n
-r

Field separator
Field to sort by
Use numeric order
Reverse direction

6.2.2 Join :
v Join combines two files based on value of common field.
v It’s similar to join operation in relation algebra.
v The available options are

-1
-2
-t

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Field to join on first file
Field to join on second file
Field separator

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6.3 Shell Variables:
v
v
v
v

Variables are wo rds/strings that take the value.
The shell allows the user to create, assign and delete variables.
The programmers use the variables according to scripts they write.
There are two types of variables, they are
è Scalar variables.
è Array variables.

6.3.1 Scalar variables:
v A scalar variable can hold only one value at a time.
v Here the variables are declared as
name = value;
v Scalar variables are also called as name value pairs.
v Because a variables name and its value can be thought as a pair.

6.3.2 Array variables :
v Array provides a method of grouping a set of variables.
v Here we can create a single array variable and store the other variables.
v Syntax:
$ name[index] = value;
v Example:
$ fruit [0] = apple;
$ fruit [1] = orange;

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7. Shell Programming in Bourne Shell
v Here the Commands run from a file in a subshell.
v We can write programs interactively by starting another new shell at the command
line.

7.1 Shell Scripting in Bourne:
v In Bourne shell the first line is always #! /bin/sh.
v Here by using the chmod we can set the file permissions for the file.
v Example:
#! /bin/sh
echo “Enter the phrase \c”
read param
echo param = $param
Output:
$ ./filename.sh
Hello There
param = Hello There

7.2 Shell variables:
v Variables are referenced by $name .
v Example:
#! /bin/sh
var1 = Kacper
var2 = Technology
echo $var1 $var2
Output:
$./filename.sh
Kacper Technology

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