Conditional Statement in Shell Script

As we are familier with conditional statements in C or other programming languages, we do understand that a set of instructions can be executed if some conditions are satisfied. Shell script also supports the conditional statements like if, if-else, nested if etc.

#!/bin/bash # Add two numbers if [ $# -ne 2 ] then echo "Usage - $0 x y" echo " Where x and y are two nos for which I will print sum" exit 1 fi echo "Sum of $1 and $2 is `expr $1 + $2`"

The following script is written to determine the biggest among the three numbers.

#!/bin/bash if [ $# -ne 3 ] then echo "$0: number1 number2 number3 are not given" >&2 exit 1 fi n1=$1 n2=$2 n3=$3 if [ $n1 -gt $n2 ] && [ $n1 -gt $n3 ] then echo "$n1 is Biggest number" elif [ $n2 -gt $n1 ] && [ $n2 -gt $n3 ] then echo "$n2 is Biggest number" elif [ $n3 -gt $n1 ] && [ $n3 -gt $n2 ] then echo "$n3 is Biggest number" elif [ $n1 -eq $n2 ] && [ $n2 -eq $n3 ] then echo "All the three numbers are equal" else echo "I can not figure out" fi

Greetings

#!/bin/bash h=`date +%H` if [ $h -lt 12 ]; then echo Good Morning elif [ $h -lt 18 ]; then echo Good Afternoon else echo Good Evening fi

Leap Year checking

echo -n "Enter year (YYYY): " read y a=`expr $y % 4` b=`expr $y % 100` c=`expr $y % 400` if [ $a -eq 0 ] && [ $b -ne 0 ] || [ $c -eq 0 ] then echo "$y is leap year" else echo "$y is not a leap year" fi

Happy Exploring!