Check if string contains another string?

Brief: This example will help you to check if one string contains another substring in a bash script.

You can use wildcard character * to find if a string contains a substring in a bash script. Here is a simple example

#!/bin/bash

str="This is the main string"

if [[ $str = *main* ]]; then
  echo "Yes"
fi

#!/bin/bash

str="This is the main string"

if [[ $str = *main* ]]; then

echo "Yes"

Output:

Yes

If you have multi-word substring, use double quote around the string:

#!/bin/bash

str="This is the main string"

if [[ $str = *"is the main"* ]]; then
  echo "Yes"
fi

#!/bin/bash

str="This is the main string"

if [[ $str = *"is the main"* ]]; then

echo "Yes"

Output:

Yes

Another Example

This is another example to read a file line by line and check if a string contains a specific substring and do some operation on it. For example, check all the users in /etc/passwd having shell /bin/bash.

#!/bin/bash

while read line; do

   if [[ $line = *"/bin/bash"* ]]; then
	   //do something here
   fi
done < /etc/passwd

#!/bin/bash

while read line; do

if [[ $line = *"/bin/bash"* ]]; then

//do something here

done < /etc/passwd

Bash

Another Example