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%center, fore "yellow", font "rouge", size 20
shell
%font "standard"
%size 4, fore "white"


bash, awk, ...

Ing. Ján ONDREJ (SAL)
%size 3
ondrejj@salstar.sk
http://www.salstar.sk/

http://www.salstar.sk/doc/shell
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Čo je shell?

	interpreter príkazov
	číta príkazy zo štandardného vstupu

%pause
Čo je štandardný vstup/výstup?
	štandardný vstup - obyčajne klávesnica
	štandardný výstup - obyčanje terminál (obrazovka)

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%page

Jednoduchý príkaz


%font "fixed"
%size 5
bash# date
%filter "date"
%endfilter
bash# _

%pause
%font "standard"
%size 7
Parametre príkazového riadku:
%font "fixed"
%size 5

bash# ls /
bin   dev  home  root  tmp   var
boot  etc  lib   proc  sbin  usr
bash# _
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%page

Expanzia príkazov


Zadáme príkaz:
%font "fixed"
%size 5

bash# ls /*

%font "standard"
%size 7
Vykoná sa:
%font "fixed"
%size 5

ls /bin /dev /home /root ...

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%page

Rúry


	previazanie štandardného výstupu prvého príkazu so \
	štandardným vstupom druhého príkazu

%font "fixed"
%size 5
  cat /etc/passwd | less

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%page

Presmerovanie


	presmerovanie výstupu
		príkaz > súbor

	presmerovanie výstupu s pridaním
		príkaz >> súbor

	presmerovanie vstupu
		príkaz < súbor

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%page

Kombinácia rúry a presmerovania


%font "fixed"
%size 5
%prefix " "
cat /etc/passwd | grep "Peter" > /tmp/petrovia

%pause
grep "Peter" /etc/passwd > /tmp/petrovia

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%page

Premenné

	Nastavenie premennej:
		A=5
	Použitie premennej:
		$A
	Špeciálne premenné:
%size 5
		$0, $1, $2, ... - jednotlivé parametre skriptu
		$@, $* - všetky parametre $1 ...
%pause
%size 5
%font "fixed"

%bar "gray70"
bash# echo $HOME
/root
bash# _

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%page

Podmienené vykonávanie


	vykonanie v prípade úspechu	
		príkaz1 && príkaz2

	vykonanie v prípade neúspechu
		príkaz1 || príkaz2

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%page

Písanie programov (skriptov)

	Súbor: "skript"
%bar "gray70"
%size 5
%font "fixed"
 #!/bin/sh

%pause
 echo "Názov skriptu: $0"
%pause

%bar "gray70"
bash# chmod +x skript
bash# ./skript
Názov skriptu: ./skript
bash# _

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%page

Podmienka

%font "fixed"
%size 5
if príkaz_podmienky; then príkaz;
  [ elif príkaz; then príkaz; ] ...
  [ else príkaz; ]
fi

%pause
%font "standard"
%size 7
Príkaz 'test':
%font "fixed"
%size 5
	test podmienka
	[ podmienka ]

%pause
%font "standard"
%size 7
Podmienka:
%font "fixed"
%size 5
	reťazec = reťazec
	číslo { -lt | -le | -eq | -ge | -gt | -ne } číslo

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%page

Príklad podmienky

%font "fixed"
%size 5
 #!/bin/sh

 if [ "$1" = "-x" ]; then
   echo JEDNA
 else
   echo DVA
 fi
%pause

%bar "gray70"
%mark
bash# ./l -x
JEDNA
bash# _
%pause
%again
%prefix "                     "
bash# ./l
DVA
bash# _

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%page

Cyklus:

%font "fixed"
%size 5
%prefix " "
for meno in zoznam; do príkaz; done

%font "standard"
%size 7
		premenná $meno bude obsahovať slová zo zoznamu
		zoznam môže obsahovat '*'

%font "fixed"
%size 5
while príkaz_podmienky; do príkaz; done

%font "standard"
%size 7
		príkaz podmienky ako pre 'if'

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%page

Príklad cyklu

%font "fixed"
%size 5
 #!/bin/sh

 for i in 1 2 3 4 5; do
   echo $i
 done
%pause

%bar "gray70"
bash# ./cyklus
1
2
3
4
5
bash# _

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%page

Príkaz grep

	vyhľadávanie reťazcov v textových súboroch

Zápis:

	grep  regulárny_výraz  súbory...

%pause
%bar "gray70"
%font "fixed"
%size 5
bash# grep "^root:" /etc/passwd
%filter "grep ^root: /etc/passwd"
%endfilter
bash# _

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%page

Regulárne výrazy


%prefix " "
%font "fixed"
%size 5
.       akýkoľvek znak
*       0-n opakovaní predch. znaku
?       0-1 opakovaní predch. znaku
+       1-n opakovaní predch. znaku
^       začiatok riadku
$       koniec riadku
[...]   zoznam znakov
[^...]  zoznam znakov, ktoré neobsahuje

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%page

Dalšie príkazy:

	expr - vyhodnotenie výrazu
%font "fixed"
%size 5
		expr 2 + $i
%pause
%font "standard"
%size 7
	cut - výber niektorého z parametrov
%font "fixed"
%size 5
		cut -d: -f1
%pause
%font "standard"
%size 7
	tr - zámena a mazanie znakov
%font "fixed"
%size 5
		tr A-Z a-z
%pause
%font "standard"
%size 7
	head, tail - výber niekoľkých riadkov zo začiatku/konca
%font "fixed"
%size 5
		head -3 /etc/issue
%pause
%font "standard"
%size 7
	wc - spočítanie riadkov, znakov, ...
%font "fixed"
%size 5
		wc -l /etc/passwd

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%page

awk

	syntax podobná jazyku C
	jednoduché spracovanie vstupu
	ľahko formátovateľný výstup

%pause
Zápis:
%font "fixed"
%size 5
   awk /vzor/ { príkazy }
	porovná všetky vzory pre každý riadok vstupu
	vykoná príkazy, pri ktorých vyhovuje vzor

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%page

Príklad skriptu s awk:


%font "fixed"
%size 5
 #!/bin/sh

 ...
 cat $@ | awk -F: '
   /^1:/ { print $2 }
   /^2:/ { print $3 }'
 ...

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%page

Príkaz printf

printf(formát, parametre, ...)
	vypísanie textu

Parametre:
	formát
		%d - desiatkové číslo
		%s - reťazec
	hodnoty, ...

%pause
%bar "gray70"
%font "fixed"
%size 5
printf("Vysledok: %d", vysledok)

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%page

Cyklus for

for(inicializácia;podmienka;inkrementácia) príkaz;

%pause
%bar "gray70"
%font "fixed"
%size 5
for(i=0;i<10;i++) printf("%d ",i)

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%page

Podmienka

if (podmienka) { príkazy } else { príkazy }

%pause
%bar "gray70"
%font "fixed"
%size 5
if (a==1) { print "A je jedna" }
else { print "A nieje jedna" }

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%page
%size 7

Ďalšie možnosti


%font "rouge", size 50
%prefix ""
%center   
XXX
%size 7

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%page

Otázky?


%font "rouge", size 70
%prefix ""
%center
?
%size 7

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%page

Ďakujem za pozornosť.


%font "rouge", size 50
%prefix ""
%center   
:-)