look – find lines in a sorted list

look [ –dfnixtc ] [ string ] [ file ]

Look consults a sorted file and prints all lines that begin with string. It uses binary search.

The following options are recognized. Options dfnt affect comparisons as in sort(1).
i    Interactive. There is no string argument; instead look takes lines from the standard input as strings to be looked up.
x    Exact. Print only lines of the file whose key matches string exactly.
d    `Directory' order: only letters, digits, tabs and blanks participate in comparisons.
f    Fold. Upper case letters compare equal to lower case.
n    Numeric comparison with initial string of digits, optional minus sign, and optional decimal point.
t[c]Character c terminates the sort key in the file. By default, tab terminates the key. If c is missing the entire line comprises the key.

If no file is specified, /lib/words is assumed, with collating sequence df.



sort(1), grep(1)

The exit status is ``not found'' if no match is found, and ``no dictionary'' if file or the default dictionary cannot be opened.