-b

Use a binary search on the given word list. If you are ignoring case with -f or ignoring non-alphanumeric characters with -d,the file must be sorted in the same way. Please note that these options are the default if no filename is given. See sort(1)for more information on sorting files.

-d

Dictionary character set and order, i.e., only alphanumeric characters are compared.

-f

Ignore the case of alphabetic characters.

-t

Specify a string termination character, i.e., only the characters in string up to and including the first occurrence oftermchar are compared.ENVIRONMENTThe LANG, LC_ALL and LC_CTYPE environment variables affect the execution of the look utility. Their effect is described in environ(7).FILES/usr/share/dict/words the dictionaryEXIT STATUSThe look utility exits 0 if one or more lines were found and displayed, 1 if no lines were found, and >1 if an error occurred.COMPATIBILITYThe original manual page stated that tabs and blank characters participated in comparisons when the -d option was specified. This wasincorrect and the current man page matches the historic implementation.look uses a linear search by default instead of a binary search, which is what most other implementations use by default.The -a and --alternative flags are ignored for compatibility.