Display any line in the file that begins with the specified string
look command is used to display any line starting with the specified string in the file.
look(option)(parameter)
-a: Use another dictionary file web2, which is also located in the /usr/dict directory;
-d: Only compare English letters and numbers, and ignore the rest;
-f: Ignore character case differences;
-t<suffix string>: Set the suffix string.