Case Insensitive Grep Search

To perform a grep search that ignores case, or is case insensitive, use the -i option (or --ignore-case). The grep command is case sensitive by default.

grep -i bob file.txt

The above command will use the grep executable to search the file file.txt for the string bob. It will return each line of the file that contains the word string bob no matter if it is spelled with upper case or lower case letters.

Here we are going to use the longer, but more descriptive grep command line argument --ignore-case to accomplish the same task as above:

grep --ignore-case bob file.txt

As you can see both options will solve our task equally well to perform a case insensitive grep search.