If else condition in shell script with $? and grep command

In shell script condition check is very easy and simple using if else statements. Here is a example which we would like to discuss with our readers.

Scenario: We have a variable that contains long string value, user wants to find matching value from given string and perform check whether that text/character has matched from string value or or not.

#Program in Bash Shell

Line 1: CHECK_SOURCE="[main] INFO com.adobe.jcr.checknode.existence - Node does not exist"

line 2: echo $CHECK_SOURCE | grep -w -o -i 'Node exists'

Line 3: if [ $? == 0 ]; then

Line 4:        echo " matched"

Line 5: else 

Line 6: echo "not matched" 

Line 7: fi 

Explanation:

In line 1 we have declared a variable CHECK_SOURCE which have some value.

In line 2 we are finding text "Node exists" in value of variable CHECK_SOURCE using grep command.

In line 3 using if statement we are checking number of matches from last executed statement. $? sign will return number of matches. If text passed in grep command will find some matching text in variable then $? will number of matching otherwise it will return zero.