LINUX OPERATING SYSTEM
What is Linux
Linux is a free operating system
that was created by Linux Tarvolds when he was a student at the
Features of Linux Operating system
The common features included in
every version of Linux are:
Multiusers: Not only can you have many user accounts available on a
linux system, but you can also have multiple users logged in and working on the
system at the same time.
Multitasking: You can have many programs running at the same time
in Linux. Besides meaning that you can have lots of programs going at once,
Many of these system processes make it possible for Linux to work as a server.
System portability: The Linux
operating system can port itself to another installation without any major
changes. This ability to adopt itself to different computers has made Linux
very popular. Linux runs on more brands of computers than other operating system.
Communications: Linux supports two major types of communications:
i)
Communications between different terminals connected to
the same computer.
ii)
Communication between users of one computer at a
specific location to the users of another type and size of a computer located
else where.
System Security: The users
data is highly secure in the Linux Operating System. There are several levels
of Security in Linux.
Graphical User Interface(X Window System): The powerful framework for working with
graphical applications in Linux is referred to as the X window system. X
handles the functions of operating X –based GUI applications and displaying
them on and X server process.
ADVANTAGES OF LINUX
Full Multitasking: Multiple
tasks can be accomplished and multiple devices can be accessed at the same
time.
Virtual Memory: Linux can
use a porting of your hand drive as virtual memory, which increases the
efficiency of your system by keeping active processes in RAM and placing less
frequent used or inactive portions of memory on disk. Virtual memory also
utilities all your systems memory and doesn’t allow memory segmentation.
The X Window System: The X
window system is a graphics system for UNIX machines. This powerful interface
supports many applications and is the standard interface for the industry.
Built – in –networking support: Linux uses standard TCP / IP protocols ,
including Network file system (NFS) and Network information services (NIS)
formerly known as YP) You can access internet by connecting your system with an
Ethernet card or over a modem to another system.
Hardware Support: You can
configure in support for almost every type of hardware that can be connected to
a computer. There is support for floppy disk drives CD Rom , removable disks
etc.
Networking Connectivity: To connect you linux system to a network ,
Linux offers support for a variety of LAN. The most popular available protocols
in Linux are TCP/ IP, IPX .
Network Servers: Providing networking services to the client
computers on your LAN or to the entire internet is what Linux does best. A
variety of software package are available that
enables you to use Linux as a print server, file server, FTP server,
Mail server, web server, news server, or wok group server.
Application Support: Because of compatibility with POSIX( Portable
operating system interface for UNIX) and several different application
programming interface a wide range of
freeware and share ware software is available for Linux.
Low cost: Linux is available
free on the internet.
GNU Software Support: Linux
can run a wide range of free software available through the GNU project. This
software includes every thing from application development ( GNU C and GNU C++)
to system administration.
THE BASIC COMMANDS OF LINUX OPERATING SYSTEM
1.
Date: This
command tells the Linux system to print the system date and time.
This command can
also be used with suitable format specifies as arguments. Each format is
preceded by a ,+, symbol, followed by the ,%, operator and a single character
describing the format. You can print only the month, using the format (+%)
Date +% M
4 or the month
name
Date +% h
Or
you can combine them in one command.
Date +% h%m
There are other
format specifies, d specifies the day of the month, y indicates the last two
digits of the year, H, M and S stands for hour, minutes and second,
respectively. Other specifies include T for the time in HH : MM: SS format, a
for the day of the week ( Sun and sat) and r for the time in AM/ PM rotation.
Date + %D (
only date )mm/ dd / yy
Date + %T only
time HH: MM: SS
Date +% Y full
year
Date +%y only
year , last two digits of the year
Date +%H Hour
Date +%S Sec
Date +%M Minute
Date +%A Full
weak day name
Date +% a 3
Character week day
Date +%h Abbr
Month
Date +% W Day of the week
2.
Time: this
can be used to get the information about the system time.
3.
who: this
command can be used to get information about all users who are currently logged
onto the system.
4.
echo: this
is a simple command used to display on the screen whatever is typed after the
command echo on the command line. The echo command squeezes out extra blanks
between commands.
5.
Clear: This
command will clear the screen and leave no trace of the command you just typed.
6.
cat: cat is
used to display the contents of a file.
7.
Cat> :
this command is used to create a file in Linux. After writing some contents
press Ctrl+ d to save the file.
8.
pwd: this
command pwd( Print working directory) tells you what you are in.
9.
mkdir: this command
is used to create a directory in Linux.
10. rmdir: An empty directory can be
removed by using rmdir command.
11. Cd: this command is used to change th
directory
12. LS: this command is used to obtain a
list of all files in the current directory.
An informative
listing of files in obtained when it is used with –l option
LS commands can
be used with various other options.
Option Description
-X à Displays multicolumn output
-F à marks executable
with * Directories with
-r à
Sorts files
in reverse order
-l à sorts files in
reverse order.
-d à Forces listing of
a directory
-a à shows all files
including and those beginning with
dot.
-t à Sorts files by modification time.
-R à Recursive listing
of all files in sub- directories.
-U à Sorts files by
access time
-I à Shows i-node
number of a file.
-C à Shorts by time of
change of the i- node.
-S à Displays number of blocks used by a
file.
-1 à one file per line.
13. Cp: This command is used to copy a
file on a group of files to the prog directories.
- rm: this
command is used to delete a file.
- mv: this
command simply renames a file
- man: this
command is used to display the material pages for a command.
- touch:
this command create an empty file in the current directory with the name
file.
- cal: this
command produces a calender of the current month as standard output. The
month and year must be specified in full numeric format.
- vi <file
name> : this command simply edit a file.
- exit: this
command used to stop the execution of a shell script.
- paste: the
paste command joins lines from two files and displays the output.
- PS-1 (environmental
variable): this command displays the system prompt.
- quit :
this command close the Linux application.
- head and tail
: the head command is used to display the initial part of text file. The tail
command displays the last part of the text file.
- WC: the wc
command is used to count the number of lines, words or characters in a
file.
- sort: this
command is used to sort the file in ascending order.
- sort-r :
this command is used to sort the file in descending order.
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