1.\" Copyright (c) 1980, 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the Institute of Electrical and Electronics Engineers, Inc. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)tail.1 8.1 (Berkeley) 6/6/93 32.\" $FreeBSD$ 33.\" 34.Dd April 10, 2018 35.Dt TAIL 1 36.Os 37.Sh NAME 38.Nm tail 39.Nd display the last part of a file 40.Sh SYNOPSIS 41.Nm 42.Op Fl F | f | r 43.Op Fl q 44.Oo 45.Fl b Ar number | Fl c Ar number | Fl n Ar number 46.Oc 47.Op Ar 48.Sh DESCRIPTION 49The 50.Nm 51utility displays the contents of 52.Ar file 53or, by default, its standard input, to the standard output. 54.Pp 55The display begins at a byte, line or 512-byte block location in the 56input. 57Numbers having a leading plus 58.Pq Ql + 59sign are relative to the beginning 60of the input, for example, 61.Dq Li "-c +2" 62starts the display at the second 63byte of the input. 64Numbers having a leading minus 65.Pq Ql - 66sign or no explicit sign are 67relative to the end of the input, for example, 68.Dq Li "-n 2" 69displays the last two lines of the input. 70The default starting location is 71.Dq Li "-n 10" , 72or the last 10 lines of the input. 73.Pp 74The options are as follows: 75.Bl -tag -width indent 76.It Fl b Ar number , Fl -blocks Ns = Ns Ar number 77The location is 78.Ar number 79512-byte blocks. 80.It Fl c Ar number , Fl -bytes Ns = Ns Ar number 81The location is 82.Ar number 83bytes. 84.It Fl f 85The 86.Fl f 87option causes 88.Nm 89to not stop when end of file is reached, but rather to wait for additional 90data to be appended to the input. 91The 92.Fl f 93option is ignored if the standard input is a pipe, but not if it is a FIFO. 94.It Fl F 95The 96.Fl F 97option implies the 98.Fl f 99option, but 100.Nm 101will also check to see if the file being followed has been renamed or rotated. 102The file is closed and reopened when 103.Nm 104detects that the filename being read from has a new inode number. 105.Pp 106If the file being followed does not (yet) exist or if it is removed, tail 107will keep looking and will display the file from the beginning if and when 108it is created. 109.Pp 110The 111.Fl F 112option is the same as the 113.Fl f 114option if reading from standard input rather than a file. 115.It Fl n Ar number , Fl -lines Ns = Ns Ar number 116The location is 117.Ar number 118lines. 119.It Fl q 120Suppresses printing of headers when multiple files are being examined. 121.It Fl r 122The 123.Fl r 124option causes the input to be displayed in reverse order, by line. 125Additionally, this option changes the meaning of the 126.Fl b , c 127and 128.Fl n 129options. 130When the 131.Fl r 132option is specified, these options specify the number of bytes, lines 133or 512-byte blocks to display, instead of the bytes, lines or blocks 134from the beginning or end of the input from which to begin the display. 135The default for the 136.Fl r 137option is to display all of the input. 138.El 139.Pp 140If more than a single file is specified, each file is preceded by a 141header consisting of the string 142.Dq Li "==> " Ns Ar XXX Ns Li " <==" 143where 144.Ar XXX 145is the name of the file unless 146.Fl q 147flag is specified. 148.Sh EXIT STATUS 149.Ex -std 150.Sh EXAMPLES 151To display the last 500 lines of the file 152.Ar foo : 153.Pp 154.Dl $ tail -n 500 foo 155.Pp 156Keep 157.Pa /var/log/messages 158open, displaying to the standard output anything appended to the file: 159.Pp 160.Dl $ tail -f /var/log/messages 161.Sh SEE ALSO 162.Xr cat 1 , 163.Xr head 1 , 164.Xr sed 1 165.Sh STANDARDS 166The 167.Nm 168utility is expected to be a superset of the 169.St -p1003.2-92 170specification. 171In particular, the 172.Fl F , 173.Fl b 174and 175.Fl r 176options are extensions to that standard. 177.Pp 178The historic command line syntax of 179.Nm 180is supported by this implementation. 181The only difference between this implementation and historic versions 182of 183.Nm , 184once the command line syntax translation has been done, is that the 185.Fl b , 186.Fl c 187and 188.Fl n 189options modify the 190.Fl r 191option, i.e., 192.Dq Li "-r -c 4" 193displays the last 4 characters of the last line 194of the input, while the historic tail (using the historic syntax 195.Dq Li -4cr ) 196would ignore the 197.Fl c 198option and display the last 4 lines of the input. 199.Sh HISTORY 200A 201.Nm 202command appeared in PWB UNIX. 203