look(1)

look1

Display lines beginning with a given string

Usage

look [-df] [-t termchar] string [file]

Overview

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.

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 options are as follows:

-d

Dictionary character set and order, i.e., only alphanumeric characters are compared.

-f

Ignore the case of alphabetic characters.

-t termchar

Specify a string termination character, i.e., only the characters in string up to and including the first occurrence of termchar are compared.

Files

/usr/share/dict/words

the dictionary

Exit status

The look utility exits 0 if one or more lines were found and displayed, 1 if no lines were found, or 1 if an error occurred.

Releases

61 releases since OpenBSD 2.1; the text changed 6 times.

  1. 2.1–2.3
  2. 2.4–2.5
  3. 2.6
  4. 2.7–3.3
  5. 3.4–4.1
  6. 4.2–4.8
  7. 4.9–8.0

Standards

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.

History

The look command appeared in Version 7 AT&T UNIX.

From man 8.0-current-20261101 in OpenBSD 8.0-current (2026-11-01). Parsed by carta from the page's mdoc source.