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UNIX Part - I
ObjectivesUnix History
Why Unix ?
Unix Features
Unix Structure
Unix Vs Windows
Unix File system
Unix Basic Commands
Permissions - chmod
Questions
By:- Kunal Chhajed
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UNIX History
In 1960s - Multics(Multiplexed Information and Computing
Service
In 1970s - the project was named Unics
In 1973, Unix was rewritten in the C programming language
AT&T made Unix available to universities and commercial firms
http://en.wikipedia.org/wiki/Multicshttp://en.wikipedia.org/wiki/C_%28programming_language%29http://en.wikipedia.org/wiki/C_%28programming_language%29http://en.wikipedia.org/wiki/Multics8/14/2019 UNIX DAY 1
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Why Use UNIX
Multi-user- Support more than one user session, simultaneously,
on the same system, at a time.
Multiprogramming - Support more than one program, in memory, ata time.
Multitasking - A single process can initiate multiple threads of
execution. Exploiting concurrency in a process.
Supports virtual memory, programs larger than the physical RAM of
the system, can be executed.
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Unix features continued ...
Supports hierarchical file system to hold user data
organized in the form of directories and files.
Identifies a user with a userid and groupid and allows
access permissions to resources to be specified usingthese ids.
Supports a large number of tools, libraries and utilities to
aid software development
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Unix Vs Windows
Unix is more flexible and can be installed on many different types of
machines.
- Unix is more stable and does not go down as often as Windows
does, therefore requires less administration and maintenance.
- Unix has greater built-in security and permissions features thanWindows.
- Unix possesses much greater processing power than Windows.
- Unix is the leader in serving the Web. About 90% of the Internet
relies on Unix operating systems running Apache, the world's most
widely used Web server.- Software upgrades from Microsoft often require the user to
purchase new or more hardware or prerequisite software. That is not
the case with Unix.
- The mostly free or inexpensive open-source operating systems
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Unix File system
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Typing UNIX Commands
ls get directory listing
ls l to view the permissions
ls F tells which are directory
ls a displays hidden files alsomkdir make directory
cd change directory
rm remove file
rmdir remove directory
more displays content of file
date - displays current date
cal - displays calendar
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Continued
echo string Echos arguments to the standardoutput
cp copy a file
mv move a file
wc [filename] count number bytes,words,lines inthe file
pwd prints the full path name of the current
directory
kill [PIDs] Terminate one or more process IDsdf shows space available on the system
du shows up space used by folders
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Continued
join file1 file2
cmp file1 file2
bc simple mathematical calculations
chsh change your login shellclear clear the terminal
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Continued
info [options] Documentation reader for
commands
Unix allows grouping of commands
e.g pwd;date;cal
passwd create or change the password withassociated user-name
touch [filename] create an empty file
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Permissions
chmod changes the permission of the file
Syntax:-
chmod [mode] filename
Permissions
u - User who owns the file.
g- Group that owns the file.
o - Other. r- Read the file.
w- Write or edit the file.
x- Execute or run the file as a program
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Continued
Numeric Permissions:
chmod can also to attributed by using Numeric Permissions:
400 read by owner
040 read by group
004 read by anybody (other)
200 write by owner
020 write by group
002 write by anybody
100 execute by owner
010 execute by group
001 execute by anybody
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Continued
for example, a common HTML file on a
Unix server to be only viewed over the Internet would
be:chmod 644 file.html
Files such as scripts that need to be executed need
more permissions. So common permission given toscripts.
chmod 755 file.cgi
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UNIX BookA Students Guide to UNIX, Harley Hahn,McGraw-Hill, 1993.
A Practical Guide to the UNIX System,Mark G. Sobell, Benjamin-Cummings,3rd Edition, 1995.
An Introduction to Berkeley UNIX,Paul Wang, Wadsworth, 1992.
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Thanks!!!
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