J.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY
Linux Programming Notes
UNIT-I
LINUX UTILITIES AND SHELL PROGRAMMING
I. Introduction to Linux:
Linux is a Unix-like computer operating system assembled under the model of free and open
source software development and distribution. The defining component of Linux is the Linux
kernel, an operating system kernel first released 5 October 1991 by Linus Torvalds.
Linux was originally developed as a free operating system for Intel x86-based personal
computers. It has since been ported to more computer hardware platforms than any other
operating system. It is a leading operating system on servers and other big iron systems such as
mainframe computers and supercomputers more than 90% of today's 500 fastest
supercomputers run some variant of Linux, including the 10 fastest. Linux also runs on
embedded systems (devices where the operating system is typically built into the firmware and
highly tailored to the system) such as mobile phones, tablet computers, network routers,
televisions and video game consoles; the Android system in wide use on mobile devices is
built on the Linux kernel.
Basic Features
Following are some of the important features of Linux Operating System.
Portable - Portability means softwares can works on different types of hardwares in
same way. Linux kernel and application programs supports their installation on any kind
of hardware platform.
Open Source - Linux source code is freely available and it is community based
development project. Multiple teams works in collaboration to enhance the capability
of Linux operating system and it is continuously evolving.
Multi-User - Linux is a multiuser system means multiple users can access
system resources like memory/ ram/ application programs at same time.
Multiprogramming - Linux is a multiprogramming system means multiple
applications can run at same time.
Hierarchical File System - Linux provides a standard file structure in which system
, J.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY
Linux Programming Notes
files/ user files are arranged.
Shell - Linux provides a special interpreter program which can be used to execute
commands of the operating system. It can be used to do various types of operations, call
application programs etc.
Security - Linux provides user security using authentication features like password
protection/ controlled access to specific files/ encryption of data.
Linux Advantages
1.Low cost: You don’t need to spend time and money to obtain licenses since Linux andmuch
of its software come with the GNU General Public License. You can start to workimmediately
without worrying that your software may stop working anytime because thefree trial version
expires. Additionally, there are large repositories from which you canfreely download high
quality software for almost any task you can think of.
2.Stability: Linux doesn’t need to be rebooted periodically to maintain performance levels.
Itdoesn’t freeze up or slow down over time due to memory leaks and such. Continuous up-
times of hundreds of days (up to a year or more) are not uncommon.
3.Performance: Linux provides persistent high performance on workstations and
onnetworks. It can handle unusually large numbers of users simultaneously, and can make
oldcomputers sufficiently responsive to be useful again.
4.Network friendliness: Linux was developed by a group of programmers over the
Internet and has therefore strong support for network functionality; client and server
systems can be easily set up on any computer running Linux. It can perform tasks such as
network backups faster and more reliably than alternative systems.
5.Flexibility: Linux can be used for high performance server applications, desktop
applications, and embedded systems. You can save disk space by only installing the
components needed for a particular use. You can restrict the use of specific computers by
installing for example only selected office applications instead of the whole suite.
6.Compatibility: It runs all common Unix software packages and can process all common file
formats.
7.Choice: The large number of Linux distributions gives you a choice. Each distribution is
developed and supported by a different organization. You can pick the one you like best; the
, J.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY
Linux Programming Notes
core functionalities are the same; most software runs on most distributions.
8.Fast and easy installation: Most Linux distributions come with user-friendly installation
and setup programs. Popular Linux distributions come with tools that make installation of
additional software very user friendly as well.
9.Full use of hard disk: Linux continues work well even when the hard disk is almost full.
10.Multitasking: Linux is designed to do many things at the same time; e.g., a large printing
job in the background won’t slow down your other work.
11.Security: Linux is one of the most secure operating systems. “Walls” and flexible file
access permission systems prevent access by unwanted visitors or viruses. Linux users have
to option to select and safely download software, free of charge, from online repositories
containing thousands of high quality packages. No purchase transactions requiring credit card
numbers or other sensitive personal information are necessary.
12.Open Source: If you develop software that requires knowledge or modification of the
operating system code, Linux’s source code is at your fingertips. Most Linux applications
are Open Source as well.
Difference between UNIX and LINUX
Features LINUX UNIX
Cost Linux can be freely distributed, Different flavors of Unix have
downloaded freely, distributed different cost structures according
through magazines, Books etc. to vendors
There are priced versions for
Linux also, but they are
normally cheaper than
Windows.
Development Linux is developed by Open Unix systems are divided into
and Source development i.e. through various other flavors, mostly
Distribution sharing and collaboration of developed by AT&T as well as
code and features through various commercial vendors and
forums etc and it is distributed non-profit organizations.
, J.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY
Linux Programming Notes
by various vendors.
Manufacturer Linux kernel is developed by Three bigest distributions are
the community. Linus Torvalds Solaris (Oracle), AIX (IBM) & HP-
oversees things. UX Hewlett Packard. And Apple
Makes OSX, an unix based os..
User Everyone. From home users to Unix operating systems were
developers and computer developed mainly for mainframes,
enthusiasts alike. servers and workstations except
OSX, Which is designed for
everyone. The Unix environment
and the client-server program
model were essential elements in
the development of the Internet
Usage Linux can be installed on a wide The UNIX operating system is used
variety of computer hardware, in internet servers, workstations &
ranging from mobile phones, PCs. Backbone of the majority of
tablet computers and video finance infastructure and many
game consoles, to mainframes 24x365 high availability solutions.
and supercomputers.
File system Ext2, Ext3, Ext4, Jfs, ReiserFS, jfs, gpfs, hfs, hfs+, ufs, xfs, zfs
support Xfs, Btrfs, FAT, FAT32, NTFS format
Text mode BASH (Bourne Again SHell) is Originally the Bourne Shell. Now
interface the Linux default shell. It can it's compatible with many others
support multiple command including BASH, Korn & C.
interpreters.
What is it? Linux is an example of Open Unix is an operating system that is
Source software development very popular in universities,
and Free Operating System companies, big enterprises etc.
(OS).
10
Linux Programming Notes
UNIT-I
LINUX UTILITIES AND SHELL PROGRAMMING
I. Introduction to Linux:
Linux is a Unix-like computer operating system assembled under the model of free and open
source software development and distribution. The defining component of Linux is the Linux
kernel, an operating system kernel first released 5 October 1991 by Linus Torvalds.
Linux was originally developed as a free operating system for Intel x86-based personal
computers. It has since been ported to more computer hardware platforms than any other
operating system. It is a leading operating system on servers and other big iron systems such as
mainframe computers and supercomputers more than 90% of today's 500 fastest
supercomputers run some variant of Linux, including the 10 fastest. Linux also runs on
embedded systems (devices where the operating system is typically built into the firmware and
highly tailored to the system) such as mobile phones, tablet computers, network routers,
televisions and video game consoles; the Android system in wide use on mobile devices is
built on the Linux kernel.
Basic Features
Following are some of the important features of Linux Operating System.
Portable - Portability means softwares can works on different types of hardwares in
same way. Linux kernel and application programs supports their installation on any kind
of hardware platform.
Open Source - Linux source code is freely available and it is community based
development project. Multiple teams works in collaboration to enhance the capability
of Linux operating system and it is continuously evolving.
Multi-User - Linux is a multiuser system means multiple users can access
system resources like memory/ ram/ application programs at same time.
Multiprogramming - Linux is a multiprogramming system means multiple
applications can run at same time.
Hierarchical File System - Linux provides a standard file structure in which system
, J.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY
Linux Programming Notes
files/ user files are arranged.
Shell - Linux provides a special interpreter program which can be used to execute
commands of the operating system. It can be used to do various types of operations, call
application programs etc.
Security - Linux provides user security using authentication features like password
protection/ controlled access to specific files/ encryption of data.
Linux Advantages
1.Low cost: You don’t need to spend time and money to obtain licenses since Linux andmuch
of its software come with the GNU General Public License. You can start to workimmediately
without worrying that your software may stop working anytime because thefree trial version
expires. Additionally, there are large repositories from which you canfreely download high
quality software for almost any task you can think of.
2.Stability: Linux doesn’t need to be rebooted periodically to maintain performance levels.
Itdoesn’t freeze up or slow down over time due to memory leaks and such. Continuous up-
times of hundreds of days (up to a year or more) are not uncommon.
3.Performance: Linux provides persistent high performance on workstations and
onnetworks. It can handle unusually large numbers of users simultaneously, and can make
oldcomputers sufficiently responsive to be useful again.
4.Network friendliness: Linux was developed by a group of programmers over the
Internet and has therefore strong support for network functionality; client and server
systems can be easily set up on any computer running Linux. It can perform tasks such as
network backups faster and more reliably than alternative systems.
5.Flexibility: Linux can be used for high performance server applications, desktop
applications, and embedded systems. You can save disk space by only installing the
components needed for a particular use. You can restrict the use of specific computers by
installing for example only selected office applications instead of the whole suite.
6.Compatibility: It runs all common Unix software packages and can process all common file
formats.
7.Choice: The large number of Linux distributions gives you a choice. Each distribution is
developed and supported by a different organization. You can pick the one you like best; the
, J.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY
Linux Programming Notes
core functionalities are the same; most software runs on most distributions.
8.Fast and easy installation: Most Linux distributions come with user-friendly installation
and setup programs. Popular Linux distributions come with tools that make installation of
additional software very user friendly as well.
9.Full use of hard disk: Linux continues work well even when the hard disk is almost full.
10.Multitasking: Linux is designed to do many things at the same time; e.g., a large printing
job in the background won’t slow down your other work.
11.Security: Linux is one of the most secure operating systems. “Walls” and flexible file
access permission systems prevent access by unwanted visitors or viruses. Linux users have
to option to select and safely download software, free of charge, from online repositories
containing thousands of high quality packages. No purchase transactions requiring credit card
numbers or other sensitive personal information are necessary.
12.Open Source: If you develop software that requires knowledge or modification of the
operating system code, Linux’s source code is at your fingertips. Most Linux applications
are Open Source as well.
Difference between UNIX and LINUX
Features LINUX UNIX
Cost Linux can be freely distributed, Different flavors of Unix have
downloaded freely, distributed different cost structures according
through magazines, Books etc. to vendors
There are priced versions for
Linux also, but they are
normally cheaper than
Windows.
Development Linux is developed by Open Unix systems are divided into
and Source development i.e. through various other flavors, mostly
Distribution sharing and collaboration of developed by AT&T as well as
code and features through various commercial vendors and
forums etc and it is distributed non-profit organizations.
, J.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY
Linux Programming Notes
by various vendors.
Manufacturer Linux kernel is developed by Three bigest distributions are
the community. Linus Torvalds Solaris (Oracle), AIX (IBM) & HP-
oversees things. UX Hewlett Packard. And Apple
Makes OSX, an unix based os..
User Everyone. From home users to Unix operating systems were
developers and computer developed mainly for mainframes,
enthusiasts alike. servers and workstations except
OSX, Which is designed for
everyone. The Unix environment
and the client-server program
model were essential elements in
the development of the Internet
Usage Linux can be installed on a wide The UNIX operating system is used
variety of computer hardware, in internet servers, workstations &
ranging from mobile phones, PCs. Backbone of the majority of
tablet computers and video finance infastructure and many
game consoles, to mainframes 24x365 high availability solutions.
and supercomputers.
File system Ext2, Ext3, Ext4, Jfs, ReiserFS, jfs, gpfs, hfs, hfs+, ufs, xfs, zfs
support Xfs, Btrfs, FAT, FAT32, NTFS format
Text mode BASH (Bourne Again SHell) is Originally the Bourne Shell. Now
interface the Linux default shell. It can it's compatible with many others
support multiple command including BASH, Korn & C.
interpreters.
What is it? Linux is an example of Open Unix is an operating system that is
Source software development very popular in universities,
and Free Operating System companies, big enterprises etc.
(OS).
10
