LOOK(1) BSD General Commands Manual LOOK(1)
look — display lines beginning with a given string
look [-bdf] [-t termchar] string [file …]
The look utility displays any lines in file which contain string as a
If file is not specified, the file /usr/share/dict/words is used, only
alphanumeric characters are compared and the case of alphabetic charac‐
ters is ignored.
The following options are available:
-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 for
more information on sorting files.
-d Dictionary character set and order, i.e., only alphanumeric char‐
acters 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
The LANG, LC_ALL and LC_CTYPE environment variables affect the execution
of the look utility. Their effect is described in environ(7).
/usr/share/dict/words the dictionary
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.
The original manual page stated that tabs and blank characters partici‐
pated in comparisons when the -d option was specified. This was incor‐
rect 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.
A look utility appeared in Version 7 AT&T UNIX.
Lines are not compared according to the current locale’s collating order.
Input files must be sorted with LC_COLLATE set to ‘C’.
BSD July 17, 2004 BSD