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.\" @(#)look.1 8.1 (Berkeley) 6/14/93 29.\" 30.Dd December 29, 2020 31.Dt LOOK 1 32.Os 33.Sh NAME 34.Nm look 35.Nd display lines beginning with a given string 36.Sh SYNOPSIS 37.Nm 38.Op Fl df 39.Op Fl t Ar termchar 40.Ar string 41.Op Ar 42.Sh DESCRIPTION 43The 44.Nm 45utility displays any lines in 46.Ar file 47which contain 48.Ar string 49as a prefix. 50As 51.Nm 52performs a binary search, the lines in 53.Ar file 54must be sorted. 55.Pp 56If 57.Ar file 58is not specified, the file 59.Pa /usr/share/dict/words 60is used, only alphanumeric characters are compared and the case of 61alphabetic characters is ignored. 62.Pp 63The following options are available: 64.Bl -tag -width indent 65.It Fl d , -alphanum 66Dictionary character set and order, i.e., only alphanumeric characters 67are compared. 68.It Fl f , -ignore-case 69Ignore the case of alphabetic characters. 70.It Fl t , -terminate Ar termchar 71Specify a string termination character, i.e., only the characters 72in 73.Ar string 74up to and including the first occurrence of 75.Ar termchar 76are compared. 77.El 78.Sh ENVIRONMENT 79The 80.Ev LANG , LC_ALL 81and 82.Ev LC_CTYPE 83environment variables affect the execution of the 84.Nm 85utility. 86Their effect is described in 87.Xr environ 7 . 88.Sh FILES 89.Bl -tag -width /usr/share/dict/words -compact 90.It Pa /usr/share/dict/words 91the dictionary 92.El 93.Sh EXIT STATUS 94The 95.Nm 96utility exits 0 if one or more lines were found and displayed, 971 if no lines were found, and >1 if an error occurred. 98.Sh EXAMPLES 99Look for lines starting with 100.Ql xylene 101in the file 102.Pa /usr/share/dict/words : 103.Bd -literal -offset indent 104$ look xylen 105xylene 106xylenol 107xylenyl 108.Ed 109.Pp 110Same as above, but do not consider any characters in 111.Ar string 112beyond the first 113.Ql e . 114Note that 115.Fl f 116is implicit since we are searching the default file 117.Pa /usr/share/dict/words : 118.Bd -literal -offset indent 119$ look -t e xylen 120Xyleborus 121xylem 122xylene 123xylenol 124xylenyl 125xyletic 126.Ed 127.Sh COMPATIBILITY 128The original manual page stated that tabs and blank characters participated 129in comparisons when the 130.Fl d 131option was specified. 132This was incorrect and the current man page matches the historic 133implementation. 134.Pp 135The 136.Fl a 137and 138.Fl -alternative 139flags are ignored for compatibility. 140.Sh SEE ALSO 141.Xr grep 1 , 142.Xr sort 1 143.Sh HISTORY 144A 145.Nm 146utility appeared in 147.At v7 . 148.Sh BUGS 149Lines are not compared according to the current locale's collating 150order. 151Input files must be sorted with 152.Ev LC_COLLATE 153set to 154.Ql C . 155