[root@localhost student]# ./hello.world hello world [root@localhost student]#
Simbolet e vecanta
Simboli
Emertimi
Kuptimi
Shembull
#
Diezis
Perdoret per te sinjalizuar nje koment. Cdo tekst i rreshtit qe ndodhet pas # konsiderohet si koment
# This line is a comment.
"
Thonjeza dyshe
Thonjezat dyshe perdoren per te rrethuar tekstet. Nese ka variabla brenda nje teksti te rrethuar me thonjeza dyshe atehere zevendesohet vlera e atij varialbli
#double quoted string echo "this script is running with UID $UID with root privileges"
'
Thonjeza teke
Thonjezat teke perdoren per te rrethuar tekstet. ese ka variabla brenda nje teksti te rrethuar me thonjeza dyshe atehere NUK zevendesohet vlera e atij varialbli
#single quoted string echo 'this script is running with UID $UID with root privileges'
;
Pikepresje
Pikepresja sherben per te ndare komandat nga njera tjetra ( command separator). Na lejon te vendosim dy komanda ne te njejtin rresht.
echo hello; echo there
;;
Dy pikepresje
Terminator ne instruksionin case. I ngjashem me break ne C.
case "$variable" in abc) echo "\$variable = abc" ;; xyz) echo "\$variable = xyz" ;; esac
,
Presja
Lidh disa shprehje si ne gjuhen C.Vlera e te gjithe shprehjeve eshte e barabarte me shprehjen me ne te djathte.
Variablat
Variablat nuk eshte e nevojshme qe te deklarohen paraprakisht. Variablat kane tipe dinamike. Ato i marrin tipet mbi bazen e vleres qe kane.
Per te krijuar nje variabel mjafton qe ti japim vlere atij.
Nese duam ti referohemi vleres se tij do te perdorim si prefix shenjen e $.
Emri i variablit nuk paraprihet nga shenja $ ne momentin e krijimit te tij ose ne instruksione vleredhenie, ku i jepet vlere atij variabli.
Per shembull:
[root@localhost student]# cat hello.world #!/bin/bash mesazh="Pershendetje nga skripti" echo $mesazh
nese do ta therrasim skriptin:
[root@localhost student]# ./hello.world Pershendetje nga skripti [root@localhost student]#
Zevendesimi i variablave ( variable substitution )
Emri i variablit eshte nje shenjues ne bytine e pare te zones se memorjes ku ruhet vlera e variablit.
Kapja e vleres se variablit quhet zevendesim i variablit ose "variable substitution"
Emrat e variablave paraprihen nga shenja e dollarit $ , sa here qe ata referohen, me perjashtim te rastit te vleredhenies dhe te "export" me $((myvar+1 )) ne nje shprehje aritmetike.
[student@localhost ~]$ myvar=1
[student@localhost ~]$ echo $myvar
1
[student@localhost ~]$
Vleredhenia
Nje variabel mund te marre vlere :
nepermjet nje isntruksioni vleredhenie myvar=1
nepermjet funksionit read
nepermjet nje cikli psh for myvar in 1 2 3
Ne rastin e nje instruktioni vleredhenie nuk lejohet hapesira:
midis emrit te variablit dhe operatorit te vleredhenies =
operatorit te vleredhenies = dhe vleres se variablit
Kodi :
[student@localhost ~]$ myvar =1 bash: myvar: command not found
gjeneron gabim, po keshtu edhe kodi
[student@localhost ~]$ myvar= 1 bash: 1: command not found
gjeneron gabim, ndersa kodi eshte i sakte pasi nuk ka hapesire as perpara dhe as pas shenjes se barazimit.
Variablat i marrin tipet ne menyre dinamike ne varesi te vleres se tyre. Ne varesi te tipit te variablit trajtohen edhe veprimet aritmetike. Kujtojme qe + eshte veprimi aritmetik i mbledhjes por ne te njejten kohe eshte dhe operatori i konkatenimit te stringjeve. Vini re shembullin me poshte
Vendosja e references se nje variabli ( me $) midis thonjezave ka efekte te ndryshme midis thonjezave dyshe (qe quhet "weak quoting") dhe tonjezave teke ( qe quhet " strong quoting".
Kodi me poshte ilustron dallimin midis weak dhe strong quoting:
Sintaksa e pergjithshme e instruksionit if then else eshte:
Shenim pikepresja eshte vendosur pasi shprehja e ndare me hapesire nga kllapat eshte vendosur ne nje rresht me then
if [ shprehje ] ; then
instruktione
else
instruksione
fi
ose pa vendosur pikepresje por ne kete rast duhet te kalojme then ne rreshtin pasardhes
if [ shprehje ] then
instruktione
else
instruksione
fi
Ushtrim
Ekzekutoni tre skriptet e meposhtme dhe sqaroni ne cdo rast ne se ka gabim cili eshte gabimi:
Shenime
Skripti 1
#!/bin/bash if [ $UID = 0 ] then # double quoted string echo "this script is running with UID $UID with root privileges"
#single quoted string echo 'this script is running with UID $UID with root privileges'
echo $USER else echo "this script is not running with root provileges" echo $USER fi
Skripti 2
#!/bin/bash
if [ $UID = 0 ]; then # double quoted string echo "this script is running with UID $UID with root privileges"
#single quoted string echo 'this script is running with UID $UID with root privileges'
echo $USER else echo "this script is not running with root provileges" echo $USER fi
Skripti 3
#!/bin/bash
if [ $UID = 0 ] then # double quoted string echo "this script is running with UID $UID with root privileges"
#single quoted string echo 'this script is running with UID $UID with root privileges'
echo $USER else echo "this script is not running with root provileges" echo $USER fi
Cikli for
Cikli for ka nje implementim te ndryshem nga gjuha C. Cikli for sherben per te iteruar ne nje liste me vlera per shembull:
#!/bin/bash mesazh="Pershendetje nga skripti" echo $mesazh for i in $(ls); do echo $i done
Skripti do te afishonte permbajtjen e dosjes korrente
[root@localhost student]# ./hello.world Pershendetje nga skripti Desktop Documents Downloads hello.bsh hello.world Music Pictures Public slaes Templates Videos [root@localhost student]#
Lista e vlerave ne te cilen merr vlere variabli mund te jete fikse , mund te jete interval ose rezultati i nje komande si ne rastin e pare ( lista perbehej nga vlerat qe kthene komanda ls)
Shembujt me poshte ilustrojne perdorimin e ciklit for per te iteruar ne nje sekuence numrash
Cikli while merr si argument nje kusht llogjik dhe iteron per sa kohe kushti eshte i vertete
Shembulli me poshte ilustron kete perdorim:
#!/bin/bash COUNTER=0 while [ $COUNTER -lt 10 ]; do echo The counter is $COUNTER let COUNTER=$COUNTER+1 done
Cikli until
Cikli until eshte i kunderti i ciklit while. Ehe until merr si argument nje kusht llogjik por iteron per sa kohe kushti nuk eshte i vertete.
#!/bin/bash COUNTER=6 until [ $COUNTER -lt 1 ]; do echo The counter is $COUNTER let COUNTER=$COUNTER-1 done
Shembulli me lart do te afishonte numrat nga 6 tek 1
[root@localhost student]# ./hello.world The counter is 6 The counter is 5 The counter is 4 The counter is 3 The counter is 2 The counter is 1 [root@localhost student]#
Operatoret e krahasimit
Per te shmagur gabimet qe mund te shkaktohen nga perdorim i simboleve te krahasimit <,> qe jane gjithashtu edhe operatoret e ridrejtimit ekzistojne operatoret te tjere krahasimi qe mund te perdoren per te formuar shprehjet llogjike.
integer comparison
-eq
is equal to
if [ "$a" -eq "$b" ]
-ne
is not equal to
if [ "$a" -ne "$b" ]
-gt
is greater than
if [ "$a" -gt "$b" ]
-ge
is greater than or equal to
if [ "$a" -ge "$b" ]
-lt
is less than
if [ "$a" -lt "$b" ]
-le
is less than or equal to
if [ "$a" -le "$b" ]
<
is less than (within double parentheses)
(("$a" < "$b"))
<=
is less than or equal to (within double parentheses)
(("$a" <= "$b"))
>
is greater than (within double parentheses)
(("$a" > "$b"))
>=
is greater than or equal to (within double parentheses)
(("$a" >= "$b"))
Operatoret mbi stringjet
=
is equal to
if [ "$a" = "$b" ]
Shenim kujdes hapesirat
!=
is not equal to
if [ "$a" != "$b"
Shenim
Ky operator se bashku me == qe eshte sinonim i = mund te realizojne patern matching ( kerkime me karaktere te vecanta psh z*) nese vendosen midis dy kllapave katrore
-Z
stringu eshte null, me gjatesi 0 karaktere
if [ -z "$1" ]; then echo usage: $0 directory exit
Funksionet
Krijimi i funksioneve dhe therritja e tyre
(shembulli)
#!/bin/bash
function sayhello() { msg=$1 echo $msg }
COUNTER=6 until [ $COUNTER -lt 1 ]; do sayhello " The counter is $COUNTER" let COUNTER=$COUNTER-1 done
Nderfaqa me perdoruesin
Komanda select
Qendron brenda komandes derisa te therritet exit
#!/bin/bash menu="Hello Quit" select opt in $menu; do if [ "$opt" = "Quit" ]; then echo done exit elif [ "$opt" = "Hello" ]; then echo Hello World else clear echo bad option echo "1) Hello" echo "2) Quit" fi done
Kapja e argumentave ne therritje te skriptit
#!/bin/bash if [ -z "$1" ]; then echo usage: $0 directory exit else arg=$1 echo "you entered" $arg fi
Leximi i input te perdoruesit me funksionin read
#!/bin/bash
echo " Shkruani emrin tuaj" read emri echo " shkruani mbiemrin tuaj" read mbiemri echo "Mire se erdhet $emri $mbiemri"
Veprimet aritmetike
Nje shprehje aritmetike fillon me shenjen e dollarit dhe vendos ne kllapa te rrumbullaketa te dyfishta:
#!/bin/bash
echo " Shkruani numrin e pare" read nr1 echo " shkruani numrin e dyte " read nr2 sh=$(($nr1+$nr2)) echo "shuma e $nr1 me $nr2 eshte= $sh"
Date & Time
Variabli date kthen kohen e momentit Duke perdorur nje maske mund te formatohet data sipas formatit te deshiruar.
Shpesh per te gjeneruar emra unke skedarish si ne rastin e backup i bashkengjitete koha e backup skedarit si nje prapashtese.
Sintaktsa per te formatiar daten eshte
date +format
shikoni shembullin me poshte:
[root@localhost student]# date +%m-%d-%Y%k:%M:%S 04-01-2014 4:29:48
Tabela me poshte liston flaget e mundshme te formatimit te dates:
%FORMAT String
Description
%%
a literal %
%a
locale's abbreviated weekday name (e.g., Sun)
%A
locale's full weekday name (e.g., Sunday)
%b
locale's abbreviated month name (e.g., Jan)
%B
locale's full month name (e.g., January)
%c
locale's date and time (e.g., Thu Mar 3 23:05:25 2005)
%C
century; like %Y, except omit last two digits (e.g., 21)
%d
day of month (e.g, 01)
%D
date; same as %m/%d/%y
%e
day of month, space padded; same as %_d
%F
full date; same as %Y-%m-%d
%g
last two digits of year of ISO week number (see %G)
%G
year of ISO week number (see %V); normally useful only with %V
%h
same as %b
%H
hour (00..23)
%I
hour (01..12)
%j
day of year (001..366)
%k
hour ( 0..23)
%l
hour ( 1..12)
%m
month (01..12)
%M
minute (00..59)
%n
a newline
%N
nanoseconds (000000000..999999999)
%p
locale's equivalent of either AM or PM; blank if not known
%P
like %p, but lower case
%r
locale's 12-hour clock time (e.g., 11:11:04 PM)
%R
24-hour hour and minute; same as %H:%M
%s
seconds since 1970-01-01 00:00:00 UTC
%S
second (00..60)
%t
a tab
%T
time; same as %H:%M:%S
%u
day of week (1..7); 1 is Monday
%U
week number of year, with Sunday as first day of week (00..53)
%V
ISO week number, with Monday as first day of week (01..53)
%w
day of week (0..6); 0 is Sunday
%W
week number of year, with Monday as first day of week (00..53)
%x
locale's date representation (e.g., 12/31/99)
%X
locale's time representation (e.g., 23:13:48)
%y
last two digits of year (00..99)
%Y
year
%z
+hhmm numeric timezone (e.g., -0400)
%:z
+hh:mm numeric timezone (e.g., -04:00)
%::z
+hh:mm:ss numeric time zone (e.g., -04:00:00)
%:::z
numeric time zone with : to necessary precision (e.g., -04, +05:30)
%Z
alphabetic time zone abbreviation (e.g., EDT)
Shkrimi ne skedare me emra te bazuar ne kohen e ekzekutimit
1- Leximi i skedarit emri i te cilit eshte argument i skriptit
Ndertoni nje skript qe merr si argument nje skedar dhe afishon permbajtjen e tij. Nese skripti nuk e merr skedarin si argumetn duhet te njoftoje perdoruesin per menyren si duhet ta therrase skriptin
Zgjidhje
skript1.sh
if [ -z "$1" ] then echo usage: $0 file to read exit fi
while read line do echo $line done < "$1"
2- Komunikimi me perdoruesin ne skript
Ndertoni nje skript qe i kerkon perdoruesit te fuse dy numra. Skripti do te gjeje dhe afishoje shumen e ketyre dy numrave
end=$(date +%s) e2=$(date +%m-%d-%Y%k:%M:%S) echo "****************************************" echo "Skripti e perfundo ekzekutimin ne $e2" koha=$(($end-$start)) echo "Skripti u ekzekutua per $koha sekonda"
4- Leximi i skedarit
Ndertoni nje skript qe merr si argument nje skedar dhe afishon permbajtjen e tij. Nese skripti nuk e merr skedarin si argument atehere duet te pyese perdoruesin per emrin e skedarit. Pasi te lexoje emrin e ksedarit nga perdoruesi duhet te afishoje ate rresht per rresht. Skripti duhet te ndertoje nje funksion i cili lexon skedarin dhe e afishon rresht per rresht dhe ta therrase ate funksion. Funksioni do ta marre emrin e skedarit si argument.
zgjidhje
clear
if [ -z "$1" ] then echo Give the name of the file to read read fname else fname="$1" fi readfile $fname
function readfile() { while read line do echo $line done < "$1" }
Nese do ta therrisnim skriptin me lart do te merrnim nje mesazh gabimi si me poshte:
Give the name of the file to read test ./filerw3: line 14: readfile: command not found [student@localhost ~]$
Cila eshte arsyeja?
Pse versioni i meposhtem i skriptit nuk jep gabim?
function readfile() { while read line do echo $line done < "$1" }
clear
if [ -z "$1" ] then echo Give the name of the file to read read fname else fname="$1" fi readfile $fname
5- Numerimi i rreshtave te skedarit
Modifikoni skriptin e pikes 4 ne menyre te tille qe te gjeje dhe te afishoje numrin e rreshtave qe ka funksioni
zgjidhje
function readfile() { while read line do echo $line done < "$1" }
function count() { counter=0 while read line do let counter=$counter+1 echo $counter $line done < "$1" return $counter }
clear
if [ -z "$1" ] then echo Give the name of the file to read read fname else fname="$1" fi readfile $fname count $fname ret=$? echo $ret
5- Shuma e numrave qe gjenen ne rreshtat e nje skedarit
Modifikoni skriptin e pikes 4 ne menyre te tille qe duke supozuar qe skedari qe merr si argument permban nje liste me numra ( nje numer ne nje rresht) gjen dhe afishon shumen e atyre numrave
function readfile() { while read line do echo $line done < "$1" }
function count() { counter=0 while read line do let counter=$counter+1 echo $counter $line done < "$1" return $counter }
function sum() { s=0 while read line do s=$(($s+$line)) echo $s $line done < "$1" return $s }
clear
if [ -z "$1" ] then echo Give the name of the file to read read fname else fname="$1" fi readfile $fname count $fname ret=$?
# vlera qe kthen funksioni menjehere me lart
echo File $fname has $ret rows sum $fname ret=$? echo sum of numbers in $fname is $ret
