“introduction to unix/linux” inx s17, day 2,...
TRANSCRIPT
“Introduction to Unix/Linux” INX_S17, Day 2, 2017-04-05
shell(s),prompt,setenv,echo,quoting,filesystem,paths,pwd,cd,ls
LearningOutcome(s):NavigateandusetheUnix/Linuxfilesystem,includingunderstandingdirectorystructure
MatthewPeterson,OSUCGRB,[email protected];containscopyrightedmaterials.
Commandprompt
http://teaching.cgrb.oregonstate.edu/CGRB/oneil/primer/partI_3_the_command_line_and_filesystem.html
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echo
• “displayalineoftext”• Example:
echo hello!
https://commons.wikimedia.org/wiki/File:Animal_echolocation.svg2
EnvironmentVariables• Bitsofinformation(preferences)storedyourshell• Canbeusedbyyouorbyotherprograms• Variablesstartwitha$ sign
echo $USER
echo $0
• Listofallthecurrentenvironmentvariablessetforyourshell?
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“Kernel,”“Shell,”“Applications”
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Hardware
Kernel
System Call Interface
Unix Commands and LibrariesShell
Shell:
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1977sh
1978csh
1983tcsh
~1989bashdashzsh
Shell:bash“itisadefaultshellonthemajorLinuxdistributionsandOSX.”https://en.wikipedia.org/wiki/Bash_(Unix_shell)
MacOSX switchedfromtcsh beingitsdefaultshelltobash inapproximately2003.
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Shell:bash
bashecho $0
exit
echo $0
Howfarcanyougodowntherabbithole?...
https://commons.wikimedia.org/wiki/File:Russian_Dolls.jpg Photo:LachlanFearnley7
SettingEnvironmentVariablessetenv <var name> <value>
setenv greeting hellosetenv greeting hello class
setenv greeting 'hello class'setenv greeting "hello $USER"
Whathappensforeach?echo $greeting
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Quotes
•Usedto“groupup”words,suchthattheyareasingle‘parameter’(value)•Canbeusedto“escape”specialcharacters,e.g.,spaces''•Examplenot usingquotesforaspace:
echo $greeting9
Quotes:single' anddouble"• Singlequotes''donot expandthecontentsofvariablesinsidethem• Doublequotes"" do expandthecontentsofvariablesinsidethem
setenv greeting
echo $greeting
setenv greeting
echo $greeting10
setenv inbash is: export
bashexport greeting="hello $USER"echo $greeting
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Lifetimeofavariable?
•Variablessetinashell“last”untilyoulogout•Whenyoulogbackinnexttime,
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WindowsandMacFilesystems
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LinuxFilesystem
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http://teaching.cgrb.oregonstate.edu/CGRB/oneil/primer/partI_3_the_command_line_and_filesystem.html
AbsolutePath(toafile)
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LinuxFilesystem (upsidedown?)
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http://faithandtech.nccumc.net/a-techies-advent-devotional/
AbsolutePathto“music”?
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/
mnt
zipmusic
http://faithandtech.nccumc.net/a-techies-advent-devotional/
LinuxFilesystem
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media bin
/
echo $HOME
https://commons.wikimedia.org/wiki/File:Home_Icon.svg
PrintWorkingDirectory
echo $PWD
pwd
Acronyms:•PWD=•CWD=
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cd ChangeDirectory
• Tomovearoundthefilesystem(“tree”)wecanusethecommand:cd• Thisallowsustomove“up”,“down”,andjumpallaroundthefilesystem
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GoingbacktoyourHomeDirectoryThereareseveralwaystogetbacktoyourhomedirectory:
#Ifyouknowtheabsolutepath,typeitin:cd
cdcdcd
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https://commons.wikimedia.org/wiki/File:Home_Icon.svg
Feelinglost?
There’snoplacelike$HOME
22https://commons.wikimedia.org/wiki/File:Ruby_slippers.JPGAttribution (CC BY-SA 3.0): https://en.wikipedia.org/wiki/User:RadioFan
ls Listingfilesanddirectories• ListfilesanddirectoriesinyourPWD/CWD(“whereIamlocatedrightnowinthefilesystem tree”)•Runningls aftercd isagoodwaytofamiliarizeyourselfwiththefilesystem• Intheshelldirectoriesaredenotedby:•BLUE highlightingofthename•
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ls Listing“hidden”(“dot”files)ls –a
•Configurationfilesoftenstartwitha:.• There’snoreasonyouneedtoseethemonadailybasiswhenworking (buttheyarethere).
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ls -l Longformatls –l
•Wewillgointodetailwhatalloftheseindividualfieldsmean(andhowtomanipulatethem)inalaterclass.•Bydefaultitshowsfilesizesinbytes•Onebyteisapproximately 1“character”,e.g.,xor 5or @
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ls -h“humanreadable”ls –l -h
• The-hoptionisusedwith–l• Showsfilesizesnotedby:• K (kilobytes)•M (megabytes)• G (gigabytes)• T (terabytes)
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ls “consolidation”ofargumentsls –l –h -a
Canbewrittenalsoas:
ls –lha
Note:Notallcommands/programssupportthe“merging”ofmultipleoptions.
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Command/VariableReview•echo $0•env / setenv $USER•tcsh / bash $HOME•pwd $PWD•cd•ls
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Exercises/Practice•Movingaround(cd)• Listingfiles/directories(ls)•Checkingwhereyouare(pwd)• Settingsome(temporary)environmentvariables(setenv)•Displayingthem(echo)
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