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. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)tail.1 8.1 (Berkeley) 6/6/93 36.\" $FreeBSD$ 37.\" 38.Dd June 5, 2009 39.Dt TAIL 1 40.Os 41.Sh NAME 42.Nm tail 43.Nd display the last part of a file 44.Sh SYNOPSIS 45.Nm 46.Op Fl F | f | r 47.Op Fl q 48.Oo 49.Fl b Ar number | Fl c Ar number | Fl n 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 64of the input, for example, 65.Dq Li "-c +2" 66starts the display at the second 67byte of the input. 68Numbers having a leading minus 69.Pq Ql - 70sign or no explicit sign are 71relative to the end of the input, for example, 72.Dq Li "-n 2" 73displays the last two lines of the input. 74The default starting location is 75.Dq Li "-n 10" , 76or the last 10 lines of the input. 77.Pp 78The options are as follows: 79.Bl -tag -width indent 80.It Fl b Ar number 81The location is 82.Ar number 83512-byte blocks. 84.It Fl c Ar number 85The location is 86.Ar number 87bytes. 88.It Fl f 89The 90.Fl f 91option causes 92.Nm 93to not stop when end of file is reached, but rather to wait for additional 94data to be appended to the input. 95The 96.Fl f 97option is ignored if the standard input is a pipe, but not if it is a FIFO. 98.It Fl F 99The 100.Fl F 101option implies the 102.Fl f 103option, but 104.Nm 105will also check to see if the file being followed has been renamed or rotated. 106The file is closed and reopened when 107.Nm 108detects that the filename being read from has a new inode number. 109.Pp 110If the file being followed does not (yet) exist or if it is removed, tail 111will keep looking and will display the file from the beginning if and when 112it is created. 113.Pp 114The 115.Fl F 116option is the same as the 117.Fl f 118option if reading from standard input rather than a file. 119.It Fl n Ar number 120The location is 121.Ar number 122lines. 123.It Fl q 124Suppresses printing of headers when multiple files are being examined. 125.It Fl r 126The 127.Fl r 128option causes the input to be displayed in reverse order, by line. 129Additionally, this option changes the meaning of the 130.Fl b , c 131and 132.Fl n 133options. 134When the 135.Fl r 136option is specified, these options specify the number of bytes, lines 137or 512-byte blocks to display, instead of the bytes, lines or blocks 138from the beginning or end of the input from which to begin the display. 139The default for the 140.Fl r 141option is to display all of the input. 142.El 143.Pp 144If more than a single file is specified, each file is preceded by a 145header consisting of the string 146.Dq Li "==> " Ns Ar XXX Ns Li " <==" 147where 148.Ar XXX 149is the name of the file unless 150.Fl q 151flag is specified. 152.Sh EXIT STATUS 153.Ex -std 154.Sh SEE ALSO 155.Xr cat 1 , 156.Xr head 1 , 157.Xr sed 1 158.Sh STANDARDS 159The 160.Nm 161utility is expected to be a superset of the 162.St -p1003.2-92 163specification. 164In particular, the 165.Fl F , 166.Fl b 167and 168.Fl r 169options are extensions to that standard. 170.Pp 171The historic command line syntax of 172.Nm 173is supported by this implementation. 174The only difference between this implementation and historic versions 175of 176.Nm , 177once the command line syntax translation has been done, is that the 178.Fl b , 179.Fl c 180and 181.Fl n 182options modify the 183.Fl r 184option, i.e., 185.Dq Li "-r -c 4" 186displays the last 4 characters of the last line 187of the input, while the historic tail (using the historic syntax 188.Dq Li -4cr ) 189would ignore the 190.Fl c 191option and display the last 4 lines of the input. 192.Sh HISTORY 193A 194.Nm 195command appeared in PWB UNIX. 196