Shell Commands
1. echo - to print the result
2. read - to get the input from the user
3. $s - access the value of s
4. -ge - greater than or equal
-le - less than or equal
-gt - greater than
-lt - less than
-eq - not equal
5. # - command line
6. + - addition
- - subtraction
\* - multiplication
/ - division
7. a=`expr $a + $b` - perform any arithmetic operation
8. case $a in - switch statement
1) ...... ;;
2) ...... ;;
3) ...... ;;
4) ...... ;;
esac
9. for((i=1;i<=5;i++))
do
.....
done
10. while [ ]
do
.....
done
11. if [ ]
then
.....
elif [ ]
then
.....
else
.....
fi
12. –a - logical AND
-o - logical OR
! - NOT
13. save the file without any extension
sh filename for compilation
./a.out to view the output
Example Programs
1. Program for arithmetic operation
echo enter the value a
read a
echo enter the value b
read b
c=`expr $a \* $b`
echo $c
2. Program for simple calculator
echo a=
read a
echo b=
read b
echo 1.add
echo 2.subtract
echo 3.multiply
echo 4.divide
echo enter the choice
read ch
case $ch in
1) c=`expr $a + $b`
echo result is c;;
2) c=`expr $a - $b`
echo result is $c;;
3) c=`expr $a * $b`
echo result is $c;;
4) c=`expr $a / $b`
echo result is $c;;
esac
3. Program for if..else statement
echo a=
read a
echo b=
read b
echo c=
read c
if [ $a -ge $b -a $a -ge $c ]
then
echo a is big
elif [ $b -ge $a -a $b -ge $c ]
then
echo b is big
else
echo c is big
fi
4. Program using for loop
echo "enter the value of n"
read n
for ((i=1 ; i<=$n ; i++))
do
echo $i
done
5. Program for while statement
echo enter the value of n
read n
s=0
while [ $n -gt 0 ]
do
s=`expr $s + $n`
n=`expr $n - 1`
done
echo the result is $s