look - display lines beginning with a given string
look [-dfa] [-t termchar] string [file]
The look utility displays any lines in file which contain string as a prefix. As look performs a binary search, the lines in file must be sorted (where sort(1) got the same options -d and/or -f that look is invoked with).
If file is not specified, the file /usr/share/dict/words is used, only alphanumeric characters are compared and the case of alphabetic characters is ignored.
Options:
The 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.
/usr/share/dict/words the dictionary
The original manual page stated that tabs and blank characters participated in comparisons when the -d option was specified. This was incorrect and the current man page matches the historic implementation.
Look appeared in Version 7 AT&T Unix.