To search for the text “deluxe” in all text files in current directory, ignoring case, and recursing sub-directories, type:
grep -i -w -n -H -R -l deluxe *.txt

• The “-i” attribute means ignore case.
• The “-w” attribute means match only whole words.
• The “-n” attribute means display the line number.
• The “-H” attribute means display the filename for each match.
• The “-R” attribute means recurse sub-directories.
• The “-l” attribute means display only the names of files containing matches.