How to check if a string contains a substring in Bash script programming

In this tutorial, the Bash script is designed to determine whether a string contains a specific substring.

There are multiple ways to perform this check, each outlined below for clarity.

Using the Comparison Operator to Check for Substring exists or not

Define a string variable containing the text.
Use if statements to compare the string with the desired substring using the equality operator (==) and a wildcard (*).
Finally, print the string if the substring is found.

mainstring='Welcome to w3schools'
if [[ $mainstring == *"w3schools"* ]]; then
  echo "w3schools exists in the main string"
fi

The =~ operator facilitates substring search within a given string, used within an if block.

Example code:

mainstring='Welcome to w3schools'
if [[ $mainstring =~ "w3schools" ]]; then
  echo "w3schools exists in the main string"
fi

The grep command is employed to search for a specified string, piped to the main string for comparison.

mainstring='Welcome to w3schools'

if echo "$mainstring" | grep -q "w3schools"; then
  echo "w3schools exists in the main string"
fi

These methods offer different approaches to checking if a string contains a particular substring, providing flexibility for different use cases.