Displays all lines containing "ERROR" in the logs/app.log file. grep is case-sensitive by default.
-iCase-insensitive search-nDisplay line numbers-rSearch directories recursively-cCount matching lines-vShow lines that don't match-C NShow N lines before and after match-RSearch directories recursively, also following symbolic links-lShow only filenames of matches-wMatch whole words only-A NShow N lines after match-B NShow N lines before match