For different programming purposes, we need to compare the value of two strings. Built-in functions are used in many programming language to test the equality of two strings. You can check the equality and inequality of two strings in bash by using if statement. “==” is used to check equality and “!=” is used to check inequality of the strings. You can partially compare the values of two strings also in bash. How you can compare the string values in bash is shown using various examples in this tutorial.
Example-1: String Comparison using “==” operators
There is no built-in comparison function to check equality of two string values in bash like other standard programming language. In the following script, two string variables, strval1 and strval2 are declared. The equity of these two string variables are tested using the first if statement of the script. The value of strval1 is compared with a string value to check the equality in the second if statement.
strval1="Ubuntu"
strval2="Windows"
#Check equality two string variables
if [ $strval1 == $strval2 ]; then
echo "Strings are equal"
else
echo "Strings are not equal"
fi
#Check equality of a variable with a string value
if [ $strval1 == "Ubuntu" ]; then
echo "Linux operating system"
else
echo "Windows operating system"
fi
Output:
First comparison is not equal and second comparison is equal.
Example-2: String Comparison using “!=” operator
The inequality of two string variables are checked in the following example. Here two values are not equal. So, if condition will be true and “Windows operating system” will print.
strval1="Ubuntu"
strval2="Windows"
#Check inequality of a variable with a string value
if [ $strval2 != "Ubuntu" ]; then
echo "Windows operating system"
else
echo "Linux operating system"
fi
Output:
Example-3: Partial String Comparison
You can compare partial value by using wild card character in bash script. In the following script, “*” is used as wild card character for partial matching. The string variable, strval contains the word “Internet”. So, the first if of the script will return true and print “Partially Match”. Bash is case sensitive. For this, the second if of the script will return false for using “internet” as partial string which is not equal by letter wise comparison.
strval="Microsoft Internet Explorer"
if [[ $strval == *Internet* ]];
then
echo "Partially Match"
else
echo "No Match"
fi
if [[ $strval == *internet* ]];
then
echo "Partially Match"
else
echo "No Match"
fi
Output:
Example-4: Compare string with user input value
Sometimes, we need to compare the string value taken by the user with specific string value for programming purpose. In the following example, a string data will be taken from user as input and compared the inequality of the data with a fixed value. If the condition is true then it will print “No Record Found”, otherwise it will print “Record Found”.
echo "Enter Your Name"
read input
if [ $input != "Fahmida" ];
then
echo "No Record Found"
else
echo "Record Found"
fi
Output:
Video of this lesson is here:
String comparison task in bash will be easier for you after completing the above examples with clear understanding.
