Man page 1 : look

look - display lines beginning with a given string

[-bdf] [-t termchar ] string .Op Ar

The utility displays any lines in file which contain string as a prefix.

If file is not specified, the file .Pa /usr/share/dict/words is used, only alphanumeric characters are compared and the case of alphabetic characters is ignored.

The following options are available:

-tag -width indent
-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 of termchar are compared.

The LANG , LC_ALL and LC_CTYPE environment variables affect the execution of the utility. Their effect is described in environ(7) .

-tag -width /usr/share/dict/words -compact
Pa /usr/share/dict/words the dictionary

The utility exits 0 if one or more lines were found and displayed, 1 if no lines were found, and >1 if an error occurred.

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.

uses a linear search by default instead of a binary search, which is what most other implementations use by default.

grep(1) , sort(1)

A utility appeared in .At v7 .

Lines are not compared according to the current locale's collating order. Input files must be sorted with LC_COLLATE set to .Ql C .