I am following the best answer on Finding all files containing a text string in linux to search string in my project. This is my command grep --include=*.rb -rnw . -e "pattern" Zsh tells me that zsh: no matches found: --include=*.rb It seems that grep doesn't support --include option. When I type grep --help, it returns usage: grep [-abcDEFGHhIiJLlmnOoPqRSsUVvwxZ] [-A num] [-B num] [-C[num]] [-e pattern] [-f file] [--binary-files=value] [--color=when] [--context[=num]] [--directories=action] [--label] [--line-buffered] [--null] [pattern] [file ...] no --include here. Is my grep version too old? Or is there something wrong with my command?