chuong_11-lt shell tren linux

8/2/2019 Chuong_11-LT Shell Tren Linux

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LP TRNH SHELLTRN LINUX

CHNG 11


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Ni dung

1. Tng quan.2. Trnh bin dch GNU.

3. Gii thiu v shell scripting.4. Nhng tnh nng ca shell.5. Cu hnh mi trng ng nhp.

6. iu khin Shell.7. C php ngn ng shell.8. Cc v d minh ha.


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1. Tng quan

Shell l chng trnh lun cthc thi khi ngidng ngnhp vo hthng.

Shell Linux htrmttplnh m c thkthp

chng li thnh mt script hay thnh mtchngtrnh c thsdngnhiuln.

Thiu st chnh ca ngn ngscript l nhnglnhny phi thng dchlimiln script thc thi.

Linux cung cp nhiu tin ch l nhng trnhthng dch cho ngn ngC, C++, debugger, cngctchc project v cng cqun l code.


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3. Gii thiu v shell scripting.

Shell l mt cu ni giao tip gia ngidng v hiu hnh Linux.

Shell c snnhBourne Again Shell (bash),Public Domain Korn Shell (pdksh) v tcshshell.

Mi user s c copy mt shell lmvicvi kernel.


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Gii thiu v shell scripting (tt).

Shell nh l mt thng dch lnh :Login vo my tnh -> hinthdu shell ->user gi mt lnh -> shell c lnh ->shell tm kimtp tin tngng trong cythmc, shell ti tin ch vo bnh ->shell thc thi tin ch -> trlidunhc.

Nu tp tin khng tm thy, shell a ramt thng bo li v hinthlidunhc.


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Gii thiu v shell scripting (tt).

Chng ta c th thay i shell mc nhsang mt shell khc vi s tr gip calnhchsh.

[root@localhost /etc]#chshChanging shell for root

Password:******

New shell [/bin/bash]:/bin/shShell changed

Shell scripts : Cc tp tin chanhiu lnhv c ththc thi cgi l shell scripts.


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4. Nhng tnh nng ca shell.

X l tng tc (Interative processing). Chy nn (Background). Chuyn hng (Redirection). ng dn (Pipe). Tp tin lnh (Shell scripts). Bin (Shell variables).

Dng li cc lnh thc hin (Command history). Cu trc lnh nh ngn ng lp trnh. T ng hon tt tn tp tin hoc lnh. B danh cho lnh (Command alias).


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Khi ngnhp vo hthng,ngi dng slm vic trong mi trng do Linux nhnghasn. Tuy nhin, chng ta c ththayi cc thitlp ny theo ring ca mnh.Mi trng lm vicgm hai thnh phn : Mi trng terminal.

Mi trng shell.Lu : Mun xc lpnhngbin mi trng, chng ta thay i trongtp tin .bash_profile(nuchy shell bash), trong tp tin .logon(nuchy shell C) v trong tp tin .profile(nuchy shell Bourne).

5. Cu hnh mi trng ng nhp.


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iukhin Shell tdng lnh : Chng ta s dng nhiu lnh trn mt dng

cch nhau bngduchmphy (;).

iukhin Shell ttp tin lnh : Cch 1: #/bin/sh filenameVd : #/bin/sh hello

Cch 2: Cpquynthc thi (excute) cho tp tin.#chmod +x filename

#/path/filename

6. iu khin Shell.


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7. C php ngn ng shell.

Bin mi trng. Nhng bin xy dng sn.

Nhng bin do user nh ngha. Cch to bin : Nhng bin khng cn phi

khai bo.

= Cch truy cp nhng gi tr ca bin.

Variable1=$(variable2)


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C php ngn ng shell (tt)

Nhp gi tr cho mt bin.#read variable

Bin cc b v ton cc. Bin mi trng.

HOME : Cha th mc ngi dng. PATH : Danh sch th mc tm kim. PS1 : Du nhc hin th lnh.

Nhng bin c xy dng sn. $# : Tng s tham s. $0 : Tn tp tin lnh. $* : Danh sch tham s y .


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Cu trc r nhnh if:if

thencommand1

[else

command2]fi


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Cu trc la chn case :case in

value1)command1 ;;

valueN)

commandN ;;esac


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Lnh kim tra :[expression]

Kim tra tp tin :r file : ng nu file tn ti v c th c.w file : ng nu file tn ti v c th ghi.x file : ng nu file tn ti v c th thc thi.

f file : ng nu file tn ti.d file : ng nu file l mt th mc .e file : ng nu file tn ti trn a.


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So snh hai s:

n m

eq : gi tr ca n v m bng nhau.ne : gi tr ca n v m khng bng nhau.gt : gi tr ca n ln hn m.lt : gi tr ca n nh hn m.

ge : gi tr ca n ln hn hay bng m.le : gi tr n nh hn hay bng m.


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So snh hai chui :

p q

= : kim tra rng hai chui bng nhau.!= : kim tra hai chui khng bng nhau.

p1

z : ng nu chui p1 c chiu di l 0.n : ng nu chui p1 c chiu di khc 0.


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So snh ton t logic :! : ph nh mt mnh logic.

a : AND.

o : OR.


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Lnh expr: Trong biu thc, cc ton t vton hng phi cch nhau bi khong trng| hoc = bng nhau& v > ln hn< nh hn >= ln hn hay bng


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Mt vi cu trc lp : For While Until

Vng lp for :for variable in const1 const2 do

commands

done


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Vng lp while :while expression

do

command

done

Vng lp until :

until expressiondo

commands

done


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Cch thc thi shell script :#bash wonderful

#!/bin/bash#chmod u+x wonderful

#wonderful


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8. Cc v d minh ha.

V d 1: Kim tra user nhp vo c trong h thng khng? Nu c,kim tra user c ang login vo h thng khng? In thng bo.on chng trnh :tmp=$( grep $1:x /etc/passwd | wcl )if [ $tmp eq 0 ]

thenecho User $1 khng tn ti trong h thng

else

echo User $1 tn ti trong h thnggrep $1:x /etc/passwd

kt=$( who | grep $1 | wcl )

if [ $ktne 0 ]then

echo User $1 ang logon vo h thngelse

echo User $1 khng logon vo h thngfi

fi


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V d 2 : Kim tra xem hm nay c phi l thby khng? Nuphi, user nhp vo s thng boHm nay l ngy nghv thot.on chng trnh :kiemtra()

{

if [ $1 = Sat ]then

echo Hm nay l ngy nghsleep 60

exit

else

echo Hom nay l ngy $1fi

}

tmp = $( date | cutc 3 )kiemtra $tmp

Cc v d minh ha (tt).


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Vd 3 : Thchin cc php ton +, -, \*, / ca 2 s.on chng trnh :tong=` expr $1 + $2 `

echo Tong ca 2 s $1 v $2 l : $tong

hieu=` expr $1 - $2 `

echo Hiu ca 2 s $1 v $2 l : $hieutich=` expr $1 \* $2 `

echo Tch ca 2 s $1 v $2 l : $tich

th=` expr $1 / $2 `echo Thng ca 2 s $1 v $2 l : $th

Cc v d minh ha (tt).

chuong_11-lt shell tren linux

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