01 - Basic Unix

7/27/2019 01 - Basic Unix

1/43

CSc 352: Basic Unix

7/27/2019 01 - Basic Unix

2/43

Reading

Chapter 1: Upto Background

Jobs (page 17)

2

7/27/2019 01 - Basic Unix

3/43

What is Unix?

Unix is an operating syste sits bet!een the hard!are and the

user"app#ications

pro$ides high%#e$e# abstractions (e&g&' i#es) and

ser$ices (e&g&' u#tiprograing)

inux: a Unix%#ike operating syste: user%#e$e#

interace $ery sii#ar to Unix

code base is dierent ro origina# Unix code

*

7/27/2019 01 - Basic Unix

4/43

Layers of a Unix system

+

hard!are

she##

Unix operating syste kerne#

users app#ications

she##coan

dssyste

ca##s

7/27/2019 01 - Basic Unix

5/43

The file system

, fileis basica##y ase-uence o bytes

Co##ections o i#esare grouped intodirectories(o#ders)

, directory is itse# ai#e

i#e syste has ahierarchica# structure(i&e&' #ike a tree)o the root is reerred to

as ".

/

ddccbb

"

ee

7/27/2019 01 - Basic Unix

6/43

!"erything is a file#

0n Unix' e$erything #ooks #ike a i#e: docuents stored on disk

directories

inter%process counication

net!ork connections de$ices (printers' graphics cards' interacti$e terina#s'

/)

hey are accessed in a unior !ay:

consistent ,0 (e&g&' read' !rite' open' c#ose'/)

consistent naing schee (e&g&'"hoe"debray' "de$"cdro)

3

7/27/2019 01 - Basic Unix

7/43

Referring to files: $%sol&te'aths

,n absolute pathspeciies ho! to get toa i#e starting at thei#e syste root

#ist the directories onthe path ro the root(")' separated by "

7

ddccbb

"

ee

gg

7/27/2019 01 - Basic Unix

8/43

Referring to files: $%sol&te'aths

,n absolute pathspeciies ho! to get toa i#e starting at thei#e syste root

#ist the directories onthe path ro the root(")' separated by "

4

ddccbb

"

ee

gg

abso#ute path:

(dd(ee(gg

7/27/2019 01 - Basic Unix

9/43

Referring to )iles: Relati"e'aths

ypica##y !e ha$e anotion o a currentdirectory

, relative pathspeciiesho! to get to a i#estarting ro thecurrent directory 5**6 eans o$e up one

#e$e#

5*6 eans currentdirectory

#ist the directories on thepath separated by "

ddccbb

"

ee

gg

7/27/2019 01 - Basic Unix

10/43

Referring to files: Relati"e'aths



#e$e#



18

ddccbb

"

ee

gg9xap#e:ffre#ati$e to eeis: **(ff

7/27/2019 01 - Basic Unix

11/43

Referring to files: Relati"e'aths



#e$e#



11

ddccbb

"

ee

gg9xap#e:ccre#ati$e to eeis: **(**(cc

7/27/2019 01 - Basic Unix

12/43

+ome directories

9ach user has a hoe directory speciied !hen the account is created

gi$en in the i#e (etc(,ass-d

hen you #og in' your current directory isyour hoe directory can then start a shelland issue coands

;otationa# shorthand: one6s o!n hoe directory: .

soe other user/oe6s hoe directory: ./oe

12

, she## is

7/27/2019 01 - Basic Unix

13/43

0n,&t and o&t,&t

=ata are read ro and !ritten to i"ostreams

here are three predeined streas:stdin : standard input usua##y' keyboard input

stdo&t: standard output usua##y' the screen

stderr: standard error or error essages (usua##y'the screen)

>ther streas can be created using syste ca##s(e&g&' to read or !rite a speciic i#e)

1*

7/27/2019 01 - Basic Unix

14/43

'rocesses

rogras are executed $iaprocesses a process is the unit o execution

consists o: the code that is executed

the data this code anipu#ates

=ierent processes execute concurrent#y each process has its o!n address space' stdin'

stdout' etc&

their execution is anaged by the operatingsyste

Coon tasks are carried out using a set

o syste%pro$ided progras ca##edcommands1+

7/27/2019 01 - Basic Unix

15/43

Unix Commands

9ach coand perors ?$ariations o@ asing#e task options can be used to odiy !hat a coand does

dierent coands can be g#ued together to peror

ore cop#ex tasks Ayntax:

command options arguments

Examples:

1.

Command 1,tions $rg&ments

p!dcd "hoe"debray

#s %a %#

#s %a# "usr"#oca#

Options can(usually) becombinedtogether:these areequivalent

7/27/2019 01 - Basic Unix

16/43

Unix Commands

9ach coand perors ?$ariations o@ asing#e task options can be used to odiy !hat a coand does

dierent coands can be g#ued together to peror

ore cop#ex tasks Ayntax:

command options arguments

Examples:

13

Command 1,tions $rg&ments

p!dcd "hoe"debray

#s %a %#

#s %a# "usr"#oca#

Not always required:

may have defaultvalues

deau#tstocurrentdirector

y

typica# deau#ts:input: stdinoutput: stdoutdirectory: current

7/27/2019 01 - Basic Unix

17/43

!xam,les of Unix commands 0

iguring out one6s current directory: ,-d

o$ing to another directory: cd targetdir

Examples:

17

cd ( o$e to the root o thei#e syste

cd .(a#so:

7/27/2019 01 - Basic Unix

18/43

!xam,les of Unix commands 00

Coand: ls lists the contents of adirectory

9xap#es:

14

ls #ist the i#es in the current directorywont show files whose names start

with .

ls (&sr(%in #ist the i#es in the directory "usr"bin

ls l gi$e a #ong orat #isting (pro$idesadditiona# ino about i#es)

ls a #ist a## i#es in the current directory'

inc#uding those that start !ith 5&6ls al (&sr(local gi$e a #ong orat #isting o a## the

i#es (inc#& those starting !ith 5&6) in"usr"#oca#

7/27/2019 01 - Basic Unix

19/43

Com%ining commands

he output o one coand can be ed toanother coand as input&

Ayntax: command1 D command

2

9xap#e:

1

pipe

ls #ists the i#es in a directory

more foo sho!s the i#e fooone screenu# at a tie

ls 4 more #ists the i#es in a directory one screenu#at a tie

+o- this -ors:ls!rites its output to its stdo&tmore6s input strea deau#ts to itsstdinthe pipe connects ls6s stdout to

more6s stdinthe piped coands run in

7/27/2019 01 - Basic Unix

20/43

)inding o&t a%o&t commands 0

iguring out !hich coand to use a,ro,os !eyword

man 6 !eywordsearches a set o database i#es containing short

descriptions o syste coands or key!ords Ee#pu#' but not a panacea:

depends on appropriate choice o key!ords ay re-uire tria# and error

ay return a #ot o resu#ts to sit through pipe through more

28

7/27/2019 01 - Basic Unix

21/43

)inding o&t a%o&t commands 00

iguring out ho! to use a coand man commanddisp#ays the on%#ine anua# pages

ro$ides inoration about coandoptions' arguents' return $a#ues' bugs'etc&

21

7/27/2019 01 - Basic Unix

22/43

!xam,le: man ls#

22

ites !ithin s-uarebrackets are optiona#

7/27/2019 01 - Basic Unix

23/43

!xam,le: man man#

2*

7/27/2019 01 - Basic Unix

24/43

!xam,le: man man#

2+

we can specifywhat !ind ofinformation wewant

7/27/2019 01 - Basic Unix

25/43

Some other &sef&l commands

-c ?file@ word count: counts characters' !ords' and #ines in theinput

gre, pattern ?file@ se#ect #ines in the input that atchpattern

head"n ?file@ sho! the irst n#ines o the input

tail "n ?file@ sho! the #ast n#ines o the input

c, file1file2 copy file

1to file

2

m" file1file

2

o$e file1to file

2

2.

7/27/2019 01 - Basic Unix

26/43

!xam,le: 7eleting a file

iguring out !hich coand to use: a,ro,os delete produces any screenu#s o output that go by too

-uick#y

a,ro,os delete 4 more any screenu#s o output' but sho!n one screenu#

at a tie

ost o the coands sho!n aren6t re#e$ant

23

7/27/2019 01 - Basic Unix

27/43

!xam,le: 7eleting a file/(1)

0dea 1: i#ter out irre#e$antstu

man 6 delete 4gre, file

27

a #ot e!erresu#tsFnothingre#e$ant

7/27/2019 01 - Basic Unix

28/43

!xam,le: 7eleting a file8(2)

0dea 2: try a dierentkey!ord

man 6 remo"e 4gre, file

24

7/27/2019 01 - Basic Unix

29/43

!xam,le: 7eleting a file8(*)



2

these are the on#y

coands thatreer to reo$ingi#es

l l i fil

7/27/2019 01 - Basic Unix

30/43

!xam,le: 7eleting a file8(+)



*8

this is the on#y

user coandthat reers toreo$ing i#es

l l i fil

7/27/2019 01 - Basic Unix

31/43

!xam,le: 7eleting a file8(.)Conir that this is the appropriate coand:

man rm#

*1

strong#ysuggestaking thisyour deau#t

Setting defa&lts for yo&r

7/27/2019 01 - Basic Unix

32/43

Setting defa&lts for yo&rcommands

Create an a#ias or your coand syntax dierent or dierent she##s

bash: aliasaliasNameGcmdName#

e$g$: alias rm%&rm "i#

see man alias or detai#s

o ha$e this a#ias in orce !hene$er you#og in' add this #ine to the i#e

H"&bashrc "" assuing your #ogin she##is bash

o ind out your #ogin she##' run thecoand

echo I8 *2

7/27/2019 01 - Basic Unix

33/43

'attern matching: gre,

**


7/27/2019 01 - Basic Unix

34/43

'attern matching: gre,8(1)

*+

print the currentdirectory

sho! the contents o thisi#e

print out the #ines thatatch nation


7/27/2019 01 - Basic Unix

35/43

'attern matching: gre,8(2)

*.

print all lines in the input

that match the string er


7/27/2019 01 - Basic Unix

36/43

'attern matching: gre,8(*)

*3

print all lines in the input that

match the string er or re

print all lines in the input thatbegin with the string er or re

7/27/2019 01 - Basic Unix

37/43

'attern matching in the shell

e can a#so use patterns in she##coands' e&g&:

Example:

*7

9 atches any string

/;

atches any one o the characters !ithinbraces

ls %9c #ist i#es that begin !ith %and end!ith c

ls

axy

7/27/2019 01 - Basic Unix

38/43

0(1 Redirection

=eau#t input"output beha$ior orcoands: stdin: keyboardF stdo&t: screenF stderr:

screen

e can change this using 0"> redirection:

*4

cmd file redirect cmd6s stdin to read rofile

cmd Kfile

redirect cmd6s stdout to file

cmd KKfile

append cmd6s stdout to file

cmd LKfile

redirect cmd6s stdout and stderr tofile

cmd1D

cmd2

redirect cmd16s stdout to cmd26s

stdin

=etting more information

7/27/2019 01 - Basic Unix

39/43

=etting more informationa%o&t files

#s M# : pro$ides additiona# ino about i#es

*

= tti i f ti

7/27/2019 01 - Basic Unix

40/43

=etting more informationa%o&t files8 (1)

+8

file namelast-modified timesizegroupowner

no. of hard links

access permissions

file type

nora# i#e

d directory

l(ell)

sybo#ic #ink

7/27/2019 01 - Basic Unix

41/43

)ile access ,ermissions

+1

access permissions for owner (u)

access permissions for group (g)

access permissions for others (o) r read

- !rite

x execute(executab#e i#e)

enter (directory)

no perission

Changing file access

7/27/2019 01 - Basic Unix

42/43

Changing file access,ermissions

Coand:chmod whowhat file

1file

2 file

n

Example:

+2

N Or' !' xP

N Oa' u' g' oP

chmod &-foo

reo$e !rite perission or user on i#e oo

chmod g>rx

%ar

gi$e read and execute perission to group

or bar

chmod or-x9*doc

reo$e a## access perissions or otherusers (i&e&' not o!ner or group ebers)or Q&doc i#es

chmod a>r-

,9

gi$e read and !rite perission to e$eryone

or a## i#es starting !ith p

)oregro&nd and Bacgro&nd

7/27/2019 01 - Basic Unix

43/43

)oregro&nd and Bacgro&nd'rocesses

u#tip#e processes can run concurrent#y at any point' there is exact#y one process that

you can interact !ith through the keyboard(oreground process)

reaining processes execute in thebackground

, process can be started in thebackground:

process;ae

he execution o the current oregroundprocess can be paused $ia ctr#%R

Documents

01 - Basic Unix