1. SHATRIX
Scripting
A  Creating and Running Scripts
 Basic Script Architecture
G  echo
E  Variables
N read

 Conditional statements
D  Loops
A  Examples

2. Creating and Running Scripts
 Scripts are normal text files with x permission
 touch script­name
 chmod 777 script­name
 chmod u+x script­name
 To run a script:
 full path
 ./script­name
 sh script­name
 bash script­name

3. Basic Script Architecure
 #!(shell-path) #!/bin/bash
 variables definition echo ”Welcome”
read var1
 read variables from user echo $var1
 loops
 conditional statements
 print output to terminal
 pipe & redirection to other files

4. echo
 echo displays a line of text
 echo ”string”
 echo $variable­name
 echo ”string $var­name”
 echo ”string $var­name another­string”
 echo $(command)
echo ”Welcome Linux users”

5. Variables
 Define a variable
 variable­name=VALUE
 Print a variable to screen
 echo $variable­name
 System variables:
 Normal: has to be changed with each user
 HOME PWD SHELL
 Environmental: changes with the login shell only
 login shell with (su ­)
 PATH
 env

6. read
 read take a value from the user to a variable
 read variable­name
 read ­p ”string” variable­name
read ­p ”Enter your name” name
echo ”Your name is $name”

7. Conditional Statements
 if statement #!/bin/bash
if [ condition ] x=5
if [ $x = 5 ]
then
then
things to do echo ”right”
elif [ another­cond. ] else
echo ”wrong”
then fi
things to do
else
things to do
fi

8. Conditional Statements
 case statement
#!/bin/bash
case $variable­name in x=5
value_1) case $x in
things to do;; 4)
echo ”x=4”;;
value_2) 5)
things to do;; echo ”x=5”
echo ”ok”;;
*)
*)
default action;; echo ”I don't know”;;
esac esac

9. Loops
 for loop
for VARIABLE in ARRAY
do
things on each value
done
#!/bin/bash
for i in 1 2 3 4 5
do
echo ”current value is $i”
done

10. Loops
 while loop
while [ condition ]
do
#!/bin/bash
things to do
VAR=0
done while [ $VAR ­lt 3 ]; do
echo $VAR
VAR=$[$VAR+1]
 equal (=) done
 not equal (!=)
 Less than (­lt)
 Greater than (­gt)

11. Examples (User Login)
#!/bin/bash
user_name="shatrix"
password="13"
read ­p "User Name: " login_name
stty ­echo
read ­p "Password: " login_pass
stty echo
echo ""
if [ $login_name = $user_name ]; then
if [ $login_pass = $password ]; then
echo "Now you are logged in....."
else
echo "Error, wrong password, try again"
fi
else
echo "Error, user name doesn't exist"
fi

12. Examples (Calculator)
#!/bin/bash
read ­p "Enter First Number: " f_num
read ­p "Enter Second Number: " s_num
read ­p "Enter Operation: " op
case $op in
+)
echo "$f_num + $s_num = $[$f_num+$s_num]";;
­)
echo "$f_num ­ $s_num = $[$f_num­$s_num]";;
x)
echo "$f_num x $s_num = $[$f_num*$s_num]";;
/)
echo "$f_num / $s_num = $[$f_num/$s_num]";;
esac

13. Examples (Modified Calculator)
#!/bin/bash
read ­p "Enter First Number: " f_num
read ­p "Enter Second Number: " s_num
read ­p "Enter Operation: " op
case $op in
+)
echo "$f_num + $s_num = $[$f_num+$s_num]";;
­)
echo "$f_num ­ $s_num = $[$f_num­$s_num]";;
x)
echo "$f_num x $s_num = $[$f_num*$s_num]";;
/)
if [ $s_num != 0 ]; then
echo "$f_num / $s_num = $[$f_num/$s_num]"
else
echo "Error, division by zero"
fi;;
*)
echo "Wrong operation, please try again !!!"
esac

14. Examples (PhoneBook)