LOOK(1) General Commands Manual LOOK(1)
look – display lines beginning with a given string
look [-df] [-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
If file is not specified, the file /usr/share/dict/words is used, only
alphanumeric characters are compared and the case of alphabetic characters
The following options are available:
-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
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 participated
in comparisons when the -d option was specified. This was incorrect and
the current man page matches the historic implementation.
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’.
macOS 12.1 July 17, 2004 macOS 12.1