196 lines
5.3 KiB
Groff
196 lines
5.3 KiB
Groff
.\" Copyright (c) 1980, 1990, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to Berkeley by
|
|
.\" the Institute of Electrical and Electronics Engineers, Inc.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)tail.1 8.1 (Berkeley) 6/6/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd June 5, 2009
|
|
.Dt TAIL 1
|
|
.Os
|
|
.Sh NAME
|
|
.Nm tail
|
|
.Nd display the last part of a file
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl F | f | r
|
|
.Op Fl q
|
|
.Oo
|
|
.Fl b Ar number | Fl c Ar number | Fl n Ar number
|
|
.Oc
|
|
.Op Ar
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
utility displays the contents of
|
|
.Ar file
|
|
or, by default, its standard input, to the standard output.
|
|
.Pp
|
|
The display begins at a byte, line or 512-byte block location in the
|
|
input.
|
|
Numbers having a leading plus
|
|
.Pq Ql +
|
|
sign are relative to the beginning
|
|
of the input, for example,
|
|
.Dq Li "-c +2"
|
|
starts the display at the second
|
|
byte of the input.
|
|
Numbers having a leading minus
|
|
.Pq Ql -
|
|
sign or no explicit sign are
|
|
relative to the end of the input, for example,
|
|
.Dq Li "-n 2"
|
|
displays the last two lines of the input.
|
|
The default starting location is
|
|
.Dq Li "-n 10" ,
|
|
or the last 10 lines of the input.
|
|
.Pp
|
|
The options are as follows:
|
|
.Bl -tag -width indent
|
|
.It Fl b Ar number
|
|
The location is
|
|
.Ar number
|
|
512-byte blocks.
|
|
.It Fl c Ar number
|
|
The location is
|
|
.Ar number
|
|
bytes.
|
|
.It Fl f
|
|
The
|
|
.Fl f
|
|
option causes
|
|
.Nm
|
|
to not stop when end of file is reached, but rather to wait for additional
|
|
data to be appended to the input.
|
|
The
|
|
.Fl f
|
|
option is ignored if the standard input is a pipe, but not if it is a FIFO.
|
|
.It Fl F
|
|
The
|
|
.Fl F
|
|
option implies the
|
|
.Fl f
|
|
option, but
|
|
.Nm
|
|
will also check to see if the file being followed has been renamed or rotated.
|
|
The file is closed and reopened when
|
|
.Nm
|
|
detects that the filename being read from has a new inode number.
|
|
.Pp
|
|
If the file being followed does not (yet) exist or if it is removed, tail
|
|
will keep looking and will display the file from the beginning if and when
|
|
it is created.
|
|
.Pp
|
|
The
|
|
.Fl F
|
|
option is the same as the
|
|
.Fl f
|
|
option if reading from standard input rather than a file.
|
|
.It Fl n Ar number
|
|
The location is
|
|
.Ar number
|
|
lines.
|
|
.It Fl q
|
|
Suppresses printing of headers when multiple files are being examined.
|
|
.It Fl r
|
|
The
|
|
.Fl r
|
|
option causes the input to be displayed in reverse order, by line.
|
|
Additionally, this option changes the meaning of the
|
|
.Fl b , c
|
|
and
|
|
.Fl n
|
|
options.
|
|
When the
|
|
.Fl r
|
|
option is specified, these options specify the number of bytes, lines
|
|
or 512-byte blocks to display, instead of the bytes, lines or blocks
|
|
from the beginning or end of the input from which to begin the display.
|
|
The default for the
|
|
.Fl r
|
|
option is to display all of the input.
|
|
.El
|
|
.Pp
|
|
If more than a single file is specified, each file is preceded by a
|
|
header consisting of the string
|
|
.Dq Li "==> " Ns Ar XXX Ns Li " <=="
|
|
where
|
|
.Ar XXX
|
|
is the name of the file unless
|
|
.Fl q
|
|
flag is specified.
|
|
.Sh EXIT STATUS
|
|
.Ex -std
|
|
.Sh SEE ALSO
|
|
.Xr cat 1 ,
|
|
.Xr head 1 ,
|
|
.Xr sed 1
|
|
.Sh STANDARDS
|
|
The
|
|
.Nm
|
|
utility is expected to be a superset of the
|
|
.St -p1003.2-92
|
|
specification.
|
|
In particular, the
|
|
.Fl F ,
|
|
.Fl b
|
|
and
|
|
.Fl r
|
|
options are extensions to that standard.
|
|
.Pp
|
|
The historic command line syntax of
|
|
.Nm
|
|
is supported by this implementation.
|
|
The only difference between this implementation and historic versions
|
|
of
|
|
.Nm ,
|
|
once the command line syntax translation has been done, is that the
|
|
.Fl b ,
|
|
.Fl c
|
|
and
|
|
.Fl n
|
|
options modify the
|
|
.Fl r
|
|
option, i.e.,
|
|
.Dq Li "-r -c 4"
|
|
displays the last 4 characters of the last line
|
|
of the input, while the historic tail (using the historic syntax
|
|
.Dq Li -4cr )
|
|
would ignore the
|
|
.Fl c
|
|
option and display the last 4 lines of the input.
|
|
.Sh HISTORY
|
|
A
|
|
.Nm
|
|
command appeared in PWB UNIX.
|