1.\" Copyright (c) 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd December 29, 2020 29.Dt LOOK 1 30.Os 31.Sh NAME 32.Nm look 33.Nd display lines beginning with a given string 34.Sh SYNOPSIS 35.Nm 36.Op Fl df 37.Op Fl t Ar termchar 38.Ar string 39.Op Ar 40.Sh DESCRIPTION 41The 42.Nm 43utility displays any lines in 44.Ar file 45which contain 46.Ar string 47as a prefix. 48As 49.Nm 50performs a binary search, the lines in 51.Ar file 52must be sorted. 53.Pp 54If 55.Ar file 56is not specified, the file 57.Pa /usr/share/dict/words 58is used, only alphanumeric characters are compared and the case of 59alphabetic characters is ignored. 60.Pp 61The following options are available: 62.Bl -tag -width indent 63.It Fl d , -alphanum 64Dictionary character set and order, i.e., only alphanumeric characters 65are compared. 66.It Fl f , -ignore-case 67Ignore the case of alphabetic characters. 68.It Fl t , -terminate Ar termchar 69Specify a string termination character, i.e., only the characters 70in 71.Ar string 72up to and including the first occurrence of 73.Ar termchar 74are compared. 75.El 76.Sh ENVIRONMENT 77The 78.Ev LANG , LC_ALL 79and 80.Ev LC_CTYPE 81environment variables affect the execution of the 82.Nm 83utility. 84Their effect is described in 85.Xr environ 7 . 86.Sh FILES 87.Bl -tag -width /usr/share/dict/words -compact 88.It Pa /usr/share/dict/words 89the dictionary 90.El 91.Sh EXIT STATUS 92The 93.Nm 94utility exits 0 if one or more lines were found and displayed, 951 if no lines were found, and >1 if an error occurred. 96.Sh EXAMPLES 97Look for lines starting with 98.Ql xylen 99in the file 100.Pa /usr/share/dict/words : 101.Bd -literal -offset indent 102$ look xylen 103xylene 104xylenol 105xylenyl 106.Ed 107.Pp 108Same as above, but do not consider any characters in 109.Ar string 110beyond the first 111.Ql e . 112Note that 113.Fl f 114is implicit since we are searching the default file 115.Pa /usr/share/dict/words : 116.Bd -literal -offset indent 117$ look -t e xylen 118Xyleborus 119xylem 120xylene 121xylenol 122xylenyl 123xyletic 124.Ed 125.Sh COMPATIBILITY 126The original manual page stated that tabs and blank characters participated 127in comparisons when the 128.Fl d 129option was specified. 130This was incorrect and the current man page matches the historic 131implementation. 132.Pp 133The 134.Fl a 135and 136.Fl -alternative 137flags are ignored for compatibility. 138.Sh SEE ALSO 139.Xr grep 1 , 140.Xr sort 1 141.Sh HISTORY 142A 143.Nm 144utility appeared in 145.At v7 . 146.Sh BUGS 147Lines are not compared according to the current locale's collating 148order. 149Input files must be sorted with 150.Ev LC_COLLATE 151set to 152.Ql C . 153