1.\" $OpenBSD: tail.1,v 1.17 2009/02/08 17:15:10 jmc Exp $ 2.\" $NetBSD: tail.1,v 1.4 1994/11/23 07:42:13 jtc Exp $ 3.\" 4.\" Copyright (c) 1980, 1990, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" This code is derived from software contributed to Berkeley by 8.\" the Institute of Electrical and Electronics Engineers, Inc. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)tail.1 8.1 (Berkeley) 6/6/93 35.\" 36.Dd $Mdocdate: February 8 2009 $ 37.Dt TAIL 1 38.Os 39.Sh NAME 40.Nm tail 41.Nd display the last part of a file 42.Sh SYNOPSIS 43.Nm tail 44.Op Fl f | r 45.Oo 46.Fl b Ar number | 47.Fl c Ar number | 48.Fl n Ar number | 49.Fl Ns Ar number 50.Oc 51.Op Ar 52.Sh DESCRIPTION 53The 54.Nm 55utility displays the contents of 56.Ar file 57or, by default, its standard input, to the standard output. 58.Pp 59The display begins at a byte, line, or 512-byte block location in the 60input. 61Numbers having a leading plus 62.Pq Ql + 63sign are relative to the beginning of the input, for example, 64.Ic -c +2 65starts the display at the second 66byte of the input. 67Numbers having a leading minus 68.Pq Ql - 69sign or no explicit sign are 70relative to the end of the input, for example, 71.Ic -n 2 72displays the last two lines of the input. 73The default starting location is 74.Ic -n 10 , 75or the last 10 lines of the input. 76.Pp 77The options are as follows: 78.Bl -tag -width Ds 79.It Fl b Ar number 80The location is 81.Ar number 82512-byte blocks. 83.It Fl c Ar number 84The location is 85.Ar number 86bytes. 87.It Fl f 88Do not stop when end-of-file is reached; instead, wait for additional 89data to be appended to the input. 90If the file is replaced (i.e., the inode number changes), 91.Nm 92will reopen the file and continue. 93If the file is truncated, 94.Nm 95will reset its position to the beginning. 96This makes 97.Nm 98more useful for watching log files that may get rotated. 99The 100.Fl f 101option is ignored if the standard input is a pipe, but not if it is a FIFO. 102.It Fl n Ar number \*(Ba Fl Ns Ar number 103The location is 104.Ar number 105lines. 106.It Fl r 107The 108.Fl r 109option causes the input to be displayed in reverse order, by line. 110Additionally, this option changes the meaning of the 111.Fl b , 112.Fl c , 113and 114.Fl n 115options. 116When the 117.Fl r 118option is specified, these options specify the number of bytes, lines 119or 512-byte blocks to display, instead of the bytes, lines, or blocks 120from the beginning or end of the input from which to begin the display. 121The default for the 122.Fl r 123option is to display all of the input. 124.El 125.Pp 126If more than a single file is specified, each file is preceded by a 127header consisting of the string 128.Dq ==> XXX <== 129where 130.Dq XXX 131is the name of the file. 132.Pp 133.Ex -std tail 134.Sh EXAMPLES 135To display the last 500 lines of the file 136.Ar foo : 137.Pp 138.Dl $ tail -500 foo 139.Pp 140Keep 141.Pa /var/log/messages 142open, displaying to the standard output anything appended to the file: 143.Pp 144.Dl $ tail -f /var/log/messages 145.Sh SEE ALSO 146.Xr cat 1 , 147.Xr head 1 , 148.Xr sed 1 149.Sh STANDARDS 150The 151.Nm 152utility is compliant with the 153.St -p1003.1-2008 154specification. 155.Pp 156The flags 157.Op Fl br 158are extensions to that specification. 159.Pp 160The historic command line syntax of 161.Nm 162is supported by this implementation. 163The only difference between this implementation and historic versions 164of 165.Nm tail , 166once the command line syntax translation has been done, is that the 167.Fl b , 168.Fl c 169and 170.Fl n 171options modify the 172.Fl r 173option, i.e., 174.Ic -r -c 4 175displays the last 4 characters of the last line 176of the input, while the historic tail (using the historic syntax 177.Ic -4cr ) 178would ignore the 179.Fl c 180option and display the last 4 lines of the input. 181.Sh HISTORY 182A 183.Nm 184command appeared in 185.At v7 . 186