look (1) - Linux Man Pages

look: display lines beginning with a given string


look - display lines beginning with a given string


[-bdf ] [-t termchar ] string [file ... ]


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

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.

The following options are available:

-b, -binary
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 , -alphanum
Dictionary character set and order, i.e., only alphanumeric characters are compared.
-f , -ignore-case
Ignore the case of alphabetic characters.
-t , -terminate termchar
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).


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.

The -a and --alternative flags are ignored for compatibility.


A utility appeared in AT&T System v7 .


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


grep(1), sort(1)