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

is used, only alphanumeric characters are compared and the case of alphabetic characters is ignored.

-d Dictionary character set and order, i.e. only alphanumeric characters are compared. (On by default if no file specified).
-f Ignore the case of alphabetic characters. (On by default if no file specified).
-a Use the alternate dictionary
-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 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 dictionary
the alternate dictionary


grep(1), sort(1)


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.


The look command is part of the util-linux-ng package and is available from

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