Example: If you have a directory with 10 000 text files in it and you need to find a certain word in a certain file but you aren’t sure what the name of the file is. You can use the method described below to find the file with selected text within it.
In the command line type the following command: grep -rni “Hello World” *.txt and press enter to execute the command. What this command does it searches within all the txt (text) files to find the sentence “Hello World” and list the results.
-r : (–recursive) Read all files under each directory recursively.
-n : (–line-number) Prefix each line of output with the 1-based line number within its input file.
-i : (–ignore-case) Ignore case distinctions in both the PATTERN and the input files.