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"Unit-I - Linux Utilities"
Introduction to Linux
Linux is a Unix-like computer operating systemassembled under the model of free and open
source software development and distribution. The defining component of Linux is the Linux
kernel, an operating system kernelfirst released !ctober "##" by Linus Torvalds.
Linux was originally developed as a free operating system for Intel x$%-based personal
computers. It has since been ported to more computer hardware platforms than any other
operating system. It is a leading operating system on serversand otherbig ironsystems such as
mainframe computersand supercomputersmore than #&' of today(s && fastest supercomputers
run some variant of Linux, including the "& fastest. Linux also runs on embedded systems
)devices where the operating system is typically built into the firmwareand highly tailored to the
system* such as mobile phones, tablet computers, network routers, televisions and video game
consoles+ the ndroidsystem in wide use on mobile devices is built on the Linux kernel.
distribution oriented toward desktop use will typically include the indow /ystemand an
accompanying desktop environmentsuch as 01!23or 453 6lasma. /ome such distributions
may include a less resource intensive desktop such as L53or fcefor use on older or lesspowerful computers. distribution intended to run as a server may omit all graphical
environments from the standard install and instead include other software such as the pache
7TT6 /erver and an //7 server such as !pen//7.8ecause Linux is freely redistributable,
anyone may create a distribution for any intended use. pplications commonly used with desktop
Linux systems include the 2o9illa :irefoxweb browser, the Libre!fficeoffice application suite,
and the 0I26image editor.
/ince the main supporting user spacesystem tools and libraries originated in the 01U 6ro;ect,
initiated in "#$< by =ichard /tallman, the :ree /oftware :oundation prefers the name
GNU/Linux.
7istory
http://en.wikipedia.org/wiki/Unix-likehttp://en.wikipedia.org/wiki/Operating_systemhttp://en.wikipedia.org/wiki/Free_and_open_source_softwarehttp://en.wikipedia.org/wiki/Free_and_open_source_softwarehttp://en.wikipedia.org/wiki/Free_and_open_source_softwarehttp://en.wikipedia.org/wiki/Linux_kernelhttp://en.wikipedia.org/wiki/Linux_kernelhttp://en.wikipedia.org/wiki/Operating_system_kernelhttp://en.wikipedia.org/wiki/Linus_Torvaldshttp://en.wikipedia.org/wiki/Linus_Torvaldshttp://en.wikipedia.org/wiki/Intel_x86http://en.wikipedia.org/wiki/Portinghttp://en.wikipedia.org/wiki/Server_(computing)http://en.wikipedia.org/wiki/Big_ironhttp://en.wikipedia.org/wiki/Big_ironhttp://en.wikipedia.org/wiki/Mainframe_computerhttp://en.wikipedia.org/wiki/Mainframe_computerhttp://en.wikipedia.org/wiki/Supercomputerhttp://en.wikipedia.org/wiki/TOP500http://en.wikipedia.org/wiki/Embedded_systemhttp://en.wikipedia.org/wiki/Firmwarehttp://en.wikipedia.org/wiki/Tablet_computerhttp://en.wikipedia.org/wiki/Router_(computing)http://en.wikipedia.org/wiki/Video_game_consolehttp://en.wikipedia.org/wiki/Video_game_consolehttp://en.wikipedia.org/wiki/Android_(operating_system)http://en.wikipedia.org/wiki/Android_(operating_system)http://en.wikipedia.org/wiki/X_Window_Systemhttp://en.wikipedia.org/wiki/Desktop_environmenthttp://en.wikipedia.org/wiki/GNOMEhttp://en.wikipedia.org/wiki/GNOMEhttp://en.wikipedia.org/wiki/KDE_Plasma_Workspaceshttp://en.wikipedia.org/wiki/LXDEhttp://en.wikipedia.org/wiki/Xfcehttp://en.wikipedia.org/wiki/Apache_HTTP_Serverhttp://en.wikipedia.org/wiki/Apache_HTTP_Serverhttp://en.wikipedia.org/wiki/SSH_serverhttp://en.wikipedia.org/wiki/OpenSSHhttp://en.wikipedia.org/wiki/OpenSSHhttp://en.wikipedia.org/wiki/Mozilla_Firefoxhttp://en.wikipedia.org/wiki/LibreOfficehttp://en.wikipedia.org/wiki/LibreOfficehttp://en.wikipedia.org/wiki/GIMPhttp://en.wikipedia.org/wiki/User_spacehttp://en.wikipedia.org/wiki/User_spacehttp://en.wikipedia.org/wiki/GNU_Projecthttp://en.wikipedia.org/wiki/Richard_Stallmanhttp://en.wikipedia.org/wiki/Free_Software_Foundationhttp://en.wikipedia.org/wiki/Free_Software_Foundationhttp://en.wikipedia.org/wiki/GNU/Linux_naming_controversyhttp://en.wikipedia.org/wiki/Operating_systemhttp://en.wikipedia.org/wiki/Free_and_open_source_softwarehttp://en.wikipedia.org/wiki/Free_and_open_source_softwarehttp://en.wikipedia.org/wiki/Linux_kernelhttp://en.wikipedia.org/wiki/Linux_kernelhttp://en.wikipedia.org/wiki/Operating_system_kernelhttp://en.wikipedia.org/wiki/Linus_Torvaldshttp://en.wikipedia.org/wiki/Intel_x86http://en.wikipedia.org/wiki/Portinghttp://en.wikipedia.org/wiki/Server_(computing)http://en.wikipedia.org/wiki/Big_ironhttp://en.wikipedia.org/wiki/Mainframe_computerhttp://en.wikipedia.org/wiki/Supercomputerhttp://en.wikipedia.org/wiki/TOP500http://en.wikipedia.org/wiki/Embedded_systemhttp://en.wikipedia.org/wiki/Firmwarehttp://en.wikipedia.org/wiki/Tablet_computerhttp://en.wikipedia.org/wiki/Router_(computing)http://en.wikipedia.org/wiki/Video_game_consolehttp://en.wikipedia.org/wiki/Video_game_consolehttp://en.wikipedia.org/wiki/Android_(operating_system)http://en.wikipedia.org/wiki/X_Window_Systemhttp://en.wikipedia.org/wiki/Desktop_environmenthttp://en.wikipedia.org/wiki/GNOMEhttp://en.wikipedia.org/wiki/KDE_Plasma_Workspaceshttp://en.wikipedia.org/wiki/LXDEhttp://en.wikipedia.org/wiki/Xfcehttp://en.wikipedia.org/wiki/Apache_HTTP_Serverhttp://en.wikipedia.org/wiki/Apache_HTTP_Serverhttp://en.wikipedia.org/wiki/SSH_serverhttp://en.wikipedia.org/wiki/OpenSSHhttp://en.wikipedia.org/wiki/Mozilla_Firefoxhttp://en.wikipedia.org/wiki/LibreOfficehttp://en.wikipedia.org/wiki/GIMPhttp://en.wikipedia.org/wiki/User_spacehttp://en.wikipedia.org/wiki/GNU_Projecthttp://en.wikipedia.org/wiki/Richard_Stallmanhttp://en.wikipedia.org/wiki/Free_Software_Foundationhttp://en.wikipedia.org/wiki/GNU/Linux_naming_controversyhttp://en.wikipedia.org/wiki/Unix-like -
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Unix
The Unix operating system was conceived and implemented in "#%# at T>T(s 8ell
Laboratories in the United /tates by 4en Thompson,5ennis =itchie,5ouglas 2cIlroy, and ?oe
!ssanna. It was first released in "#@" and was initially entirely written in assembly language, a
common practice at the time. Later, in a key pioneering approach in "#@
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2ost Linux distributions support do9ens of programming languages. The original development
tools used for building both Linux applications and operating system programs are found within
the 01U toolchain, which includes the 01U Aompiler Aollection)0AA* and the 01U build
system. mongst others, 0AA provides compilers for da, A, ACC, ?ava, and :ortran. :irst
released in D&&
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7. $oice:The large number of Linux distributions gives you a choice. 3ach distribution is
developed and supported by a different organi9ation. Gou can pick the one you like best+ the
core functionalities are the same+ most software runs on most distributions.
8. !ast and easy installation:2ost Linux distributions come with user-friendly installation
and setup programs. 6opular Linux distributions come with tools that make installation of
additional software very user friendly as well.9. !ull use of $ard dis:Linux continues work well even when the hard disk is almost full.
10. %ultitasing:Linux is designed to do many things at the same time+ e.g., a large printing
;ob in the background wonHt slow down your other work.
11. Security:Linux is one of the most secure operating systems. JallsK and flexible file
access permission systems prevent access by unwanted visitors or viruses. Linux users have
to option to select and safely download software, free of charge, from online repositories
containing thousands of high uality packages. 1o purchase transactions reuiring credit
card numbers or other sensitive personal information are necessary.
12. en Source:If you develop software that reuires knowledge or modification of the
operating system code, LinuxHs source code is at your fingertips. 2ost Linux applicationsare !pen /ource as well.
'$e difference between Linux and UNI( o#erating systems)
U1I is copyrighted name only big companies are allowed to use the U1I copyright and
name, so I82 I and /un /olaris and 76-U all are U1I operating systems. The !pen
0roup holdsthe U1I trademark in trust for the industry, and manages the U1I trademark
licensing program.
2ost U1I systems are commercial in nature.
Linux is a UNI( lone
8ut if you consider 6ortable !perating /ystem Interface )6!/I* standards then Linux can be
considered as U1I. To uote from !fficial Linux kernel =3523 file
Linux is a Unix clone written from scratch by Linus Torvalds with assistance from a loosely-knit
team of hackers across the 1et. It aims towards 6!/I compliance.
7owever, M!pen 0roupM do not approve of the construction MUnix-likeM, and consider it misuse
of their U1I trademark.
Linux Is *ust a +ernel
http://www.unix.org/http://www.unix.org/http://www.unix.org/http://www.unix.org/ -
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Linux is ;ust a kernel. ll Linux distributions includes 0UI system C 01U utilities )such as cp,
mv, ls,date, bash etc* C installation > management tools C 01U cBcCC Aompilers C 3ditors )vi*
C and various applications )such as !pen!ffice, :irefox*. 7owever, most U1I operating
systems are considered as a complete operating system as everything come from a single source
or vendor.
s I said earlier Linux is ;ust a kernel and Linux distribution makes it complete usable operating
systems by adding various applications. 2ost U1I operating systems comes with -N
programs such as editor, compilers etc. :or example 76-U or /olaris comes with -N
programs.
License and cost
Linux is :ree )as in beer OfreedomP*. Gou can download it from the Internet or redistribute it
under 01U licenses. Gou will see the best community support for Linux. 2ost U1I like
operating systems are not free )but this is changing fast, for example !pen/olaris U1I*.
7owever, some Linux distributions such as =edhat B 1ovell provides additional Linux support,
consultancy, bug fixing, and training for additional fees.
User-!riendly
Linux is considered as most user friendly U1I like operating systems. It makes it easy to install
sound card, flash players, and other desktop goodies. 7owever, pple !/ is most popular
U1I operating system for desktop usage.
Security !irewall Software
Linux comes with open source netfilterBiptables based firewall tool to protect your server and
desktop from the crackers and hackers. U1I operating systems comes with its own firewall
product )for example /olaris U1I comes with ipfilter based firewall* or you need to purchase a
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U1I comes with various file systems such as ;fs, gpfs )I*, ;fs, gpfs )76-U*, ;fs,
gpfs )/olaris*.
System Administration 'ools
". U1I comes with its own tools such as /2 on 76-U.
D. /use Linux comes with Gast
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few popular names
". 76-U
D. I82 I
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Gou can look at this from both sides of the fence. /ome say giving the public access to the code
opens the operating system )and the software that runs on top of it* to malicious developers who
will take advantage of any weakness they find. !thers say that having full access to the code
helps bring about faster improvements and bug fixes to keep those malicious developers from
being able to bring the system down. I have, on occasion, dipped into the code of one Linux
application or another, and when all was said and done, was happy with the results. Aould I have
done that with a closed-source indows applicationS 1o.
03: Licensing freedom vs2 licensing restrictions
long with access comes the difference between the licenses. IHm sure that every IT professional
could go on and on about licensing of 6A software. 8ut letHs ;ust look at the key aspect of the
licenses )without getting into legalese*. ith a Linux 06L-licensed operating system, you are
free to modify that software and use and even republish or sell it )so long as you make the code
available*. lso, with the 06L, you can download a single copy of a Linux distribution )or
application* and install it on as many machines as you like. ith the 2icrosoft license, you cando none of the above. Gou are bound to the number of licenses you purchase, so if you purchase
"& licenses, you can legally install that operating system )or application* on only "& machines.
04: &nline #eer su##ort vs2 #aid $el#-des su##ort
This is one issue where most companies turn their backs on Linux. 8ut itHs really not necessary.
ith Linux, you have the support of a huge community via forums, online search, and plenty of
dedicated eb sites. nd of course, if you feel the need, you can purchase support contracts from
some of the bigger Linux companies )=ed 7at and 1ovell for instance*.
7owever, when you use the peer support inherent in Linux, you do fall prey to time. Gou could
have an issue with something, send out e-mail to a mailing list or post on a forum, and within "&
minutes be flooded with suggestions. !r these suggestions could take hours of days to come in. It
seems all up to chance sometimes. /till, generally speaking, most problems with Linux have
been encountered and documented. /o chances are good youHll find your solution fairly uickly.
!n the other side of the coin is support for indows. Ges, you can go the same route with
2icrosoft and depend upon your peers for solutions. There are ;ust as many help
sitesBlistsBforums for indows as there are for Linux. nd you can purchase support from
2icrosoft itself. 2ost corporate higher-ups easily fall victim to the safety net that having a
support contract brings. 8ut most higher-ups havenHt had to depend up on said support contract.
!f the various people I know who have used either a Linux paid support contract or a 2icrosoft
paid support contract, I canHt say one was more pleased than the other. This of course begs the
uestion Jhy do so many say that 2icrosoft support is superior to Linux paid supportSK
05: !ull vs2 #artial $ardware su##ort
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!ne issue that is slowly becoming nonexistent is hardware support. Gears ago, if you wanted to
install Linux on a machine you had to make sure you hand-picked each piece of hardware or
your installation would not work "&& percent. I can remember, back in "##@-ish, trying to figure
out why I couldnHt get Aaldera Linux or =ed 7at Linux to see my modem. fter much looking
around, I found I was the proud owner of a inmodem. /o I had to go out and purchase a U/
=obotics external modem because that was the one modem I knewwould work. This is not so
much the case now. Gou can grab a 6A )or laptop* and most likely get one or more Linux
distributions to install and work nearly "&& percent. 8ut there are still some exceptions. :or
instance, hibernateBsuspend remains a problem with many laptops, although it has come a long
way.
ith indows, you know that most every piece of hardware will work with the operating
system. !f course, there are times )and I have experienced this over and over* when you will
wind up spending much of the day searching for the correct drivers for that piece of hardware
you no longer have the install disk for. 8ut you can go out and buy that "&-cent 3thernet card and
know itHll work on your machine )so long as you have, or can find, the drivers*. Gou also can restassured that when you purchase that insanely powerful graphics card, you will probably be able
to take full advantage of its power.
06: ommand line vs2 no command line
1o matter how far the Linux operating system has come and how ama9ing the desktop
environment becomes, the command line will always be an invaluable tool for administration
purposes. 1othing will ever replace my favorite text-based editor, ssh, and any given command-
line tool. I canHt imagine administering a Linux machine without the command line. 8ut for the
end user not so much. Gou could use a Linux machine for years and never touch the command
line. /ame with indows. Gou can still use the command line with indows, but not nearly to
the extent as with Linux. nd 2icrosoft tends to obfuscate the command prompt from users.
ithout going to =un and entering cmd )or command, or whichever it is these days*, the user
wonHt even know the command-line tool exists. nd if a user does get the indows command
line up and running, how useful is it reallyS
07: entrali8ed vs2 noncentrali8ed a##lication installation
The heading for this point might have thrown you for a loop. 8ut letHs think about this for a
second. ith Linux you have )with nearly every distribution* a centrali9ed location where you
can search for, add, or remove software. IHm talking about package management systems, such as/ynaptic. ith /ynaptic, you can open up one tool, search for an application )or group of
applications*, and install that application without having to do any eb searching )or
purchasing*.
indows has nothing like this. ith indows, you must know where to find the software you
want to install, download the software )or put the A5 into your machine*, and run setup.exe or
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install.exe with a simple double-click. :or many years, it was thought that installing applications
on indows was far easier than on Linux. nd for many years, that thought was right on target.
1ot so much now. Installation under Linux is simple, painless, and centrali9ed.
09: !lexibility vs2 rigidity
I always compare Linux )especially the desktop* and indows to a room where the floor and
ceiling are either movable or not. ith Linux, you have a room where the floor and ceiling can
be raised or lowered, at will, as high or low as you want to make them. ith indows, that floor
and ceiling are immovable. Gou canHt go further than 2icrosoft has deemed it necessary to go.
Take, for instance, the desktop. Unless you are willing to pay for and install a third-party
application that can alter the desktop appearance, with indows you are stuck with what
2icrosoft has declared is the ideal desktop for you. ith Linux, you can pretty much make your
desktop look and feel exactly how you wantBneed. Gou can have as much or as little on your
desktop as you want. :rom simple flat :luxbox to a full-blown
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drive to access the contents of a A5 is completely foreign to new users. There is a reason this is
the way it is. 8ecause Linux has always been a multiuser platform, it was thought that forcing a
user to mount a media to use it would keep the userHs files from being overwritten by another
user. Think about it !n a multiuser system, if everyone had instant access to a disk that had been
inserted, what would stop them from deleting or overwriting a file you had ;ust added to the
mediaS Things have now evolved to the point where Linux subsystems are set up so that you can
use a removable device in the same way you use them in indows. 8ut itHs not the norm. nd
besides, who doesnHt want to manually edit the/etc/fstabfleS
01
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- /how all.
-b !mits line numbers for blank space in the output.
-e character will be printed at the end of each line prior to a new line.
-3 5isplays a )dollar sign* at the end of each line.
-n Line numbers for all the output lines.
-s If the output has multiple empty lines it replaces it with one empty line.
-T 5isplays the tab characters in the output.
-v1on-printing characters )with the exception of tabs, new-lines and form-
feeds* are printed visibly.
.(A%PL.:
". To Areate a new file
cat V file".txt
This command creates a new file file".txt. fter typing into the file press controlCd )Wd*
simultaneously to end the file.
D. To ppend data into the file
cat VV file".txt
To append data into the same file use append operator VV to write into the file, else the
file will be overwritten )i.e., all of its contents will be erased*.
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such situation you can print those files in a new file or display the file using less
command.
cat file".txt fileD.txt X less
. To concatenate several files and to transfer the output to another file.
cat file".txt fileD.txt V file
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D. To delete a directory tree
rm -ir tmp
This rm command recursively removes the contents of all subdirectories of the tmpdirectory, prompting you regarding the removal of each file, and then removes the tmp
directory itself.
:
cd command is used to change the directory.
S?N'A(:
The /yntax is
cd Odirectory X Y X .B X ..B X - P
&P'I&NS:
-L Use the physical directory structure.
-6 :orces symbolic links.
.(A%PL.:
". cd linux-command
This command will take you to the sub-directory)linux-command* from its parent
directory.
D. cd 22
This will change to the parent-directory from the current working directoryBsub-directory.
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: cp command copy files from one location to another. If the destination is an existing file, then
the file is overwritten+ if the destination is an existing directory, the file is copied into the
directory )the directory is not overwritten*.
S?N'A(:
The /yntax is
cp O!6TI!1/P... /!U=A3 53/T
cp O!6TI!1/P... /!U=A3... 5I=3AT!=G
cp O!6TI!1/P... --target-directoryZ5I=3AT!=G /!U=A3...
&P'I&NS:
-a same as -dp=.
--backupOZA!1T=!LP make a backup of each existing destination file
-b like --backup but does not accept an argument.
-fif an existing destination file cannot be opened, remove it and try
again.
-p same as --preserveZmode,ownership,timestamps.
--
preserveOZTT=[LI/TP
preserve the specified attributes )default
mode,ownership,timestamps* and security contexts, if possible
additional attributes links, all.
--no-
preserveZTT=[LI/Tdon(t preserve the specified attribute.
--parents append source path to 5I=3AT!=G..(A%PL.:
". Aopy two files
cp file" fileD
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The above cp command copies the content of file".php to fileD.php.
D. To backup the copied file
cp -b file".php fileD.php
8ackup of file".php will be created with (Y( symbol as fileD.phpY.
:
ls command lists the files and directories under current working directory.
S?N'A(:
The /yntax is
ls O!6TI!1/P... O:IL3P
&P'I&NS:
-lLists all the files, directories and their mode, 1umber of links, owner of the
file, file si9e, 2odified date and time and filename.
-t Lists in order of last modification time.
-a Lists all entries including hidden files.
-d Lists directory files instead of contents.
-p 6uts slash at the end of each directories.-u List in order of last access time.
-i 5isplay inode information.
-ltr List files order by date.
-l/r List files order by file si9e.
.(A%PL.:
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". 5isplay root directory contents
ls B
lists the contents of root directory.
D. 5isplay hidden files and directories
ls -a
lists all entries including hidden files and directories.
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&P'I&NS:
-fLink files without uestioning the user, even if the mode of target forbids
writing. This is the default if the standard input is not a terminal.
-n 5oes not overwrite existing files.
-s Used to create soft links.
.(A%PL.:
". ln -s file".txt fileD.txt
Areates a symbolic link to (file".txt( with the name of (fileD.txt(. 7ere inode for (file".txt(
and (fileD.txt( will be different.
D. ln -s nimi nimi"
Areates a symbolic link to (nimi( with the name of (nimi"(.
c$own &%%AN>:
chown command is used to change the owner B user of the file or directory. This is an admin
command, root user only can change the owner of a file or directory.
S?N'A(:
The /yntax is
chown OoptionsP newowner filenameBdirectoryname
&P'I&NS:
-=
Ahange the permission on files that are in the subdirectories of the directory
that you are currently in.
-c Ahange the permission for each file.
-f6revents chown from displaying error messages when it is unable to change
the ownership of a file.
.(A%PL.:
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". chown hiox test.txt
The owner of the (test.txt( file is root, Ahange to new user hiox.
D. chown -= hiox test
The owner of the (test( directory is root, ith -= option the files and subdirectories user
also gets changed.
:
chmod command allows you to alter B Ahange access rights to files and directories.
!ile Permission is given for users@grou# and ot$ers as@
ead rite .xecute
User
Brou#
&t$ers
Permission 000
Symbolic %ode ___ ___ __
S?N'A(:
The /yntax is
chmod OoptionsP O2!53P :ile1ame
!ile Permission
F :ile 6ermission
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& none
" execute only
D write only
< write and execute
Q read only
read and execute
% read and write
@ set all permissions
&P'I&NS:
-c 5isplays names of only those files whose permissions are being changed
-f /uppress most error messages-= Ahange files and directories recursively
-v !utput version information and exit.
.(A%PL.:
". To view your files with what permission they are
ls -alt
This command is used to view your files with what permission they are.
D. To make a file readable and writable by the group and others.
chmod &%% file".txt
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&P'I&NS:
-m /et the access mode for the new directories.
-p Areate intervening parent directories if they don(t exist.
-v 6rint help message for each directory created.
.(A%PL.:
". Areate directory
mkdir test
The above command is used to create the directory (test(.
D. Areate directory and set permissions
mkdir -m %%% test
The above command is used to create the directory (test( and set the read and write
permission.
rmdir &%%AN>:
rmdir command is used to deleteBremove a directory and its subdirectories.
S?N'A(:
The /yntax is
rmdir Ooptions..P 5irectory
&P'I&NS:
-pllow users to remove the directory dirname and its parent directories which
become empty.
.(A%PL.:
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". To deleteBremove a directory
rmdir tmp
rmdir command will removeBdelete the directory tmp if the directory is empty.
D. To delete a directory tree
rm -ir tmp
This command recursively removes the contents of all subdirectories of the tmp directory,
prompting you regarding the removal of each file, and then removes the tmp directory
itself.
mv &%%AN>:
mv command which is short for move. It is used to moveBrename file from one directory to
another. mv command is different from cp command as it completely removes the file from the
source and moves to the directory specified, where cp command ;ust copies the content from one
file to another.
S?N'A(: The /yntax is
mv O-fP O-iP oldname newname
&P'I&NS:
-fThis will not prompt before overwriting )euivalent to --replyZyes*. mv -f will
move the file)s* without prompting even if it is writing over an existing target.
-i 6rompts before overwriting another file..(A%PL.:
". To =ename B 2ove a file
mv file".txt fileD.txt
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This command renames file".txt as fileD.txt
D. To move a directory
mv hscripts tmp
In the above line mv command moves all the files, directories and sub-directories from
hscripts folderBdirectory to tmp directory if the tmp directory already exists. If there is no
tmp directory it rename(s the hscripts directory as tmp directory.
:
diff command is used to find differences between two files.
S?N'A(:
The /yntax is
diff Ooptions..P from-file to-file
&P'I&NS:
-a Treat all files as text and compare them line-by-line.
-b Ignore changes in amount of white space.
-c Use the context output format.
-e 2ake output that is a valid ed script.
-7Use heuristics to speed handling of large files that have numerous scattered
small changes.
-i Ignore changes in case+ consider upper- and lower-case letters euivalent.
-n6rints in =A/-format, like -f except that each command specifies the number
of lines affected.
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-!utput =A/-format diffs+ like -f except that each command specifies the
number of lines affected.
-r hen comparing directories, recursively compare any subdirectories found.
-s =eport when two files are the same.
-w Ignore white space when comparing lines.-y Use the side by side output format.
.(A%PL.:
Lets create two files file".txt and fileD.txt and let it have the following data.
5ata in file".txt 5ata in fileD.txt
7I! T3/T
hscripts.comwith friend ship
hiox india
7I! T3/T
7/A=I6T/.com
with friend ship
". Aompare files ignoring white space
diff -w file".txt fileD.txt
This command will compare the file file".txt with fileD.txt ignoring whiteBblank space
and it will produce the following output.
DcD
\ hscripts.com
---
V 7/A=I6T/.com
Qd:
more command is used to display text in the terminal screen. It allows only backward
movement.
S?N'A(:
The /yntax is
more OoptionsP filename
&P'I&NS:
-c Alear screen before displaying.
-e 3xit immediately after writing the last line of the last file in the argument list.
-n /pecify how many lines are printed in the screen for a given file.
Cn /tarts up the file from the given number.
.(A%PL.:
". more -c index.php
Alears the screen before printing the file .
D. more -< index.php
6rints first three lines of the given file. 6ress.nterto display the file line by line.
$ead &%%AN>:
head command is used to display the first ten lines of a file, and also specifies how many lines
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to display.
S?N'A(:
The /yntax is
head OoptionsP filename
&P'I&NS:
-n To specify how many lines you want to display.
-n numberThe number option-argument must be a decimal integer whose sign affects
the location in the file, measured in lines.
-c numberThe number option-argument must be a decimal integer whose sign affects
the location in the file, measured in bytes.
.(A%PL.:
". head index.php
This command prints the first "& lines of (index.php(.
D. head - index.php
The head command displays the first lines of (index.php(.
:
tail command is used to display the last or bottom part of the file. 8y default it displays last
"& lines of a file.
S?N'A(:
The /yntax is
tail OoptionsP filename
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&P'I&NS:
-l To specify the units of lines.
-b To specify the units of blocks.
-n To specify how many lines you want to display.
-c numberThe number option-argument must be a decimal integer whose sign affects the
location in the file, measured in bytes.
-n numberThe number option-argument must be a decimal integer whose sign affects the
location in the file, measured in lines.
.(A%PL.:
". tail index.php
It displays the last "& lines of (index.php(.
D. tail -D index.php
It displays the last D lines of (index.php(.
:
cut command is used to cut out selected fields of each line of a file. The cut command uses
delimiters to determine where to split fields.
S?N'A(:
The /yntax is
cut OoptionsP
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&P'I&NS:
-c /pecifies character positions.
-b /pecifies byte positions.
-d flags /pecifies the delimiters and fields.
.(A%PL.:
". cut -c"-< text.txt
&ut#ut:
Thi
Aut the first three letters from the above line.
D. cut -d, -f",D text.txt
&ut#ut:
This is, an example program
The above command is used to split the fields using delimiter and cut the first two fields.
#aste &%%AN>:
paste command is used to paste the content from one file to another file. It is also used to set
column format for each line.
S?N'A(:
The /yntax is
paste OoptionsP
&P'I&NS:
-s 6aste one file at a time instead of in parallel.
-d =euse characters from LI/T instead of T8s .
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.(A%PL.:
". paste test.txtVtest".txt
6aste the content from (test.txt( file to (test".txt( file.
D. ls X paste - - - -
List all files and directories in four columns for each line.
sort &%%AN>:
sort command is used to sort the lines in a text file.
S?N'A(:
The /yntax is
sort OoptionsP filename
&P'I&NS:
-r /orts in reverse order.
-u If line is duplicated display only once.-o filename /ends sorted output to a file.
.(A%PL.:
". sort test.txt
/orts the (test.txt(file and prints result in the screen.
D. sort -r test.txt
/orts the (test.txt( file in reverse order and prints result in the screen.
bout uni
=eport or filter out repeated lines in a file.
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/yntax
uni# [-c | -" | -u ] [ -f fiel"s ] [ -s car ] [-n] [$m] [input!file [ output!file ] ]
-c 6recede each output line with a count of the number of times the line occurred in
the input.
-d /uppress the writing of lines that are not repeated in the input.
-u /uppress the writing of lines that are repeated in the input.
-f fields Ignore the first fields fields on each input line when doing comparisons, where
fields is a positive decimal integer. field is the maximal string matched by the
basic regular expression
OOblankPPROWOblankPPR
If fields specifies more fields than appear on an input line, a null string will be
used for comparison.
-s char Ignore the first chars characters when doing comparisons, where chars is a
positive decimal integer. If specified in con;unction with the -f option, the first
chars characters after the first fields fields will be ignored. If chars specifies more
characters than remain on an input line, a null string will be used for comparison.-n 3uivalent to -f fields with fields set to n.
Cm 3uivalent to -s chars with chars set to m.
input[file path name of the input file. If input[file is not specified, or if the input[file is -,
the
standard input will be used.
output[file path name of the output file. If output[file is not specified, the standard output
will be used. The results are unspecified if the file named by output[file is the
file named by input[file.
3xamples
uniG myfile12txt H myfile32txt- =emoves duplicate lines in the first file".txt and outputs the
results to the second file.
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bout tr
Translate characters.
/yntax
tr [-c] [-"] [-s] [string%] [string&]
-c Aomplement the set of characters specified by string".
-d 5elete all occurrences of input characters that are specified by string".
-s =eplace instances of repeated characters with a single character.
string" :irst string or character to be changed.
stringD /econd string or character to change the string".
3xamples
ec$o "1345679 ;359" tr 1345679; com#uter$- this example takes an echo response of
("D
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-a
/lowly ad;ust the time by sss.fff seconds )fff represents fractions of a second*.
This ad;ustment can be positive or negative.!nly system adminB super user
can ad;ust the time.
-s date
-string
/ets the time and date to the value specfied in the datestring. The datestr may
contain the month names, time9ones, (am(, (pm(, etc.
-u 5isplay )or set* the date in 0reenwich 2ean Time )02T-universal time*.
!ormat:
'a bbreviated weekday)Tue*.
' :ull weekday)Tuesday*.
'b bbreviated month name)?an*.
'8 :ull month name)?anuary*.
'c Aountry-specific date and time format..
'5 5ate in the format 'mB'dB'y.
'; ?ulian day of year )&&"-
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The above command will remove space and print as
5ate is &@BD
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.(A%PL.:
". who -u7
&ut#ut:
123 LI13 TI23 I5L3 6I5 A!2231T
hiox ttyp< ?ul "& ""&$ . Q@$
This sample output was produced at "" a.m. The M.M indiacates activity within the last
minute.
D. who am i
who am i command prints the user name.
ec$o &%%AN>:
echo command prints the given input string to standard output.
S?N'A(:
The /yntax isecho Ooptions..P OstringP
&P'I&NS:
-n do not output the trailing newline
-e enable interpretation of the backslash-escaped characters listed below
-3 disable interpretation of those seuences in /T=I10s
ithout -3, the following seuences are recogni9ed and interpolated
]111the character whose /AII code is 111
)octal*
]a alert )83L*
]] backslash
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]b backspace
]c suppress trailing newline
]f form feed
]n new line
]r carriage return
]t hori9ontal tab
]v vertical tab
.(A%PL.:
". echo command
echo Mhscripts 7iox IndiaM
The above command will print as hscripts 7iox India
D. To use backspace
echo -e Mhscripts ]b7iox ]bIndiaM
The above command will remove space and print as hscripts7ioxIndia
:
passwd command is used to change your password.
S?N'A(:
The /yntax is
passwd OoptionsP
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&P'I&NS:
-a /how password attributes for all entries.
-l Locks password entry for name.
-d 5eletes password for name. The login name will not be prompted for
password.
-f:orce the user to change password at the next login by expiring the password
for name.
.(A%PL.:
". passwd
3ntering ;ust passwd would allow you to change the password. fter entering passwd youwill receive the following three prompts
Aurrent 6assword
1ew 6assword
Aonfirm 1ew 6assword
3ach of these prompts must be entered correctly for the password to be successfully
changed.
#wd &%%AN>:
pwd - 6rint orking 5irectory. pwd command prints the full filename of the current working
directory.
S?N'A(:
The /yntax is
pwd OoptionsP
&P'I&NS:
-6 The pathname printed will not contain symbolic links.
-L The pathname printed may contain symbolic links.
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.(A%PL.:
". 5isplays the current working directory.
pwd
If you are working in home directory then, pwd command displays the current working
directory as Bhome.
cal &%%AN>:
cal command is used to display the calendar.
S?N'A(:
The /yntax is
cal OoptionsP OmonthP OyearP
&P'I&NS:
-" 5isplays single month as output.
-< 5isplays prevBcurrentBnext month output.
-s 5isplays sunday as the first day of the week.
-m 5isplays 2onday as the first day of the week.
-; 5isplays ?ulian dates )days one-based, numbered from ?anuary "*.
-y 5isplays a calendar for the current year.
.(A%PL.:
". cal
&ut#ut:
/eptember D&&$
/u 2o Tu e Th :r /a
" D < Q %
@ $ # "& "" "D "
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"Q " "% "@ "$ "# D&
D" DD D< DQ D D% D@
D$ D#
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-h hostname X
terminal
Used by in.telnetd to pass information about the remote host and terminal type.
-r hostname Used by in.rlogind to pass information about
the remote host.
3xamples
login com#uter$o#e2com- ould attempt to login to the computerhope domain.
uname command
6rint name of current system.
/yntax
uname O-aP O-iP O-mP O-nP O-pP O-rP O-sP O-vP O-P O-/ systemnameP
-a 6rint basic information currently available from the system.
-i 6rint the name of the hardware implementation )platform*.
-m 6rint the machine hardware name )class*. Use of this option is discouraged+ use
uname -p instead.-n 6rint the nodename )the nodename is the name by which the system is known to
a communications network*.
-p 6rint the current host(s I/ or processor type.
-r 6rint the operating system release level.
-s 6rint the name of the operating system. This is the default.
-v 6rint the operating system version.
- 6rint expanded system information, one information
element per line, as expected by /A! Unix. The
displayed information includes
system name, node, release, version, machine, and number of A6Us.
8usType, /erial, and Users )set to MunknownM in /olaris*
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!32F and !riginF )set to & and ", respectively*
-/
systemname
The nodename may be changed by specifying a system name argument. The
system name argument is restricted to /G/[12L1 characters. /G/[12L1 is
an implementation specific value defined in \sysButsname.hV. !nly the super-
user is allowed
this capability.
3xamples
uname -arv
List the basic system information, !/ release, and !/ version as shown below.
/un!/ hope .@ 0eneric["&%Q"-&$ sunQm sparc /U1,/6=Astation-"&
uname -#
5isplay the Linux platform.
S.>:
hat is sedS
non-interactive stream editor
Interprets sed instructions and performs actions
Use sed to
utomatically perform edits on file)s*
/implify doing the same edits on multiple files
rite conversion programs
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sed command syntax
sed !peration
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7ow 5oes sed orkS
sed reads line of input
line of input is copied into a temporary buffer called pattern space
editing commands are applied
subseuent commands are applied to line in the pattern space, not the
original input line
once finished, line is sent to output
)unless ^n option was used*
line is removed from pattern space
sed reads next line of input, until end of file
1ote input file is unchanged
sed instruction format
address determines which lines in the input file are to be processed by the command)s*
if no address is specified, then the command is applied to each input line
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address types
/ingle-Line address
/et-of-Lines address
=ange address
1ested address
/ingle-Line ddress
/pecifies only one line in the input file
special dollar sign )* denotes last line of input file
3xamples
show only line M#O in#ut-file
6rint lines between 830I1 and 315, inclusive
,.BIN
Line 1 of in#ut
Line 3 of in#ut
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Line4 of in#ut
.N>
Line 5 of in#ut
Line 6 of in#ut
1ested ddress
1ested address contained within another address
3xample
print blank lines between line D& and
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Line 1umber
line number command )Z* writes the current line number before each matchedBoutput line
3xamples
sed -e JM'wo-t$irds-timeMFJ tuition2data
sed -e JMQ
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/yntax
addressV iK
text
ppend Aommand a
adds one or more lines directly to the output after the address
/imilar to the insert command )i*, append cannot be used with a range address.
ppended JtextK does not appear in sedHs pattern space.
/yntax
addressV aK
text
Ahange Aommand c
replaces an entire matched line with new text
accepts four address types
single-line, set-of-line, range, and nested addresses.
/yntax
address1@address3VV cK
text
5elete Aommand d
deletes the entire pattern space
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commands following the delete command are ignored since the deleted text is no
longer in the pattern space
/yntax
address1@address3VV d
/ubstitute Aommand )s*
/yntax
addr1V@addr3V sMsearc$Mre#laceMflagsV
replaces text selected by search string with replacement string
search string can be regular expression
flags
global )g*, i.e. replace all occurrences
specific substitution count )integer*, default "
=egular 3xpressions use with sed
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/ubstitution 8ack =eferences
3xample =eplacement /tring >
cat datafile
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$arles %ain 42< 2; 4 45
S$aron Bray 624 2;9 6 34
Patricia =emenway 52< 29 5 19
', Savage 525 25 6 3 actions
#attern Raction
if pattern is missing, action is applied to all lines
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if action is missing, the matched line is printed
must have either pattern or action
3xample
aw JMforMJ testfile
prints all lines containing string JforK in testfile
8asic Terminology input file
field is a unit of data in a line
3ach field is separated from the other fields by the field separator
default field separator is whitespace
record is the collection of fields in a line
data file is made up of records
3xample Input :ile
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8uffers
awk supports two types of buffers
record and field
field buffer
one for each fields in the current record.
names ", D,
record buffer
& holds the entire record
/ome /ystem Eariables
:/ :ield separator )defaultZwhitespace*
=/ =ecord separator )defaultZ]n*
1: 1umber of fields in current record
1= 1umber of the current record
!:/ !utput field separator )defaultZspace*
!=/ !utput record separator )defaultZ]n*
:IL3123 Aurrent filename
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3xample =ecords and :ields
cat em#s
'om *ones 5535 6M13M77 654465
%ary Adams 6457 11M5M74 3976
Sally $ang 1765 9M33M65 76
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3 %ary Adams 3976
4 Sally $ang 76
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comment lines start with F
awk /cripts
830I1 pre-processing
performs processing that must be completed before the file processing starts )i.e.,
before awk starts reading records from the input file*
useful for initiali9ation tasks such as to initiali9e variables and to create report
headings
8!5G 6rocessing
contains main processing logic to be applied to input records
like a loop that processes input data one record at a time
if a file contains "&& records, the body will be executed "&& times, one for
each record
315 post-processing
contains logic to be executed after all input data have been processed
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match
entire input record
regular expression enclosed by `BHs
explicit pattern-matching expressions
Y )match*, _Y )not match*
expression operators
arithmetic
relational
logical
3xample match input record
cat em#loyees3
'om *ones:5535:6M13M77:654465
%ary Adams:6457:11M5M74:3976
Sally $ang:1765:9M33M65:76
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cat datafile
nort$west N $arles %ain 42< 2; 4 45
western . S$aron Bray 624 2;9 6 34
sout$west S Lewis >alsass 329 2 3 1
sout$ern S& Suan $in 621 2;6 5 16
sout$east S. Patricia =emenway 52< 29 5 19
eastern .A ', Savage 525 25 6 3
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