TAIL(1) | General Commands Manual | TAIL(1) |
tail
— display the
last part of a file
tail |
[-f | -r ]
[-b number |
-c number |
-n number |
- number]
[file ...] |
The tail
utility displays the contents of
file or, by default, its standard input, to the
standard output.
The display begins at a byte, line, or 512-byte block location in
the input. Numbers having a leading plus
(‘+
’) sign are relative to the
beginning of the input, for example, -c +2
starts
the display at the second byte of the input. Numbers having a leading minus
(‘-
’) sign or no explicit sign are
relative to the end of the input, for example, -n 2
displays the last two lines of the input. The default starting location is
-n 10
, or the last 10 lines of the input.
The options are as follows:
-b
number-c
number-f
tail
will reopen the file and
continue. If the file is truncated, tail
will
reset its position to the beginning. This makes
tail
more useful for watching log files that may
get rotated. The -f
option is ignored if there are
no file arguments and the standard input is a pipe
or a FIFO.-n
number |
-
number-r
-r
option causes the input to be displayed in
reverse order, by line. Additionally, this option changes the meaning of
the -b
, -c
, and
-n
options. When the -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 -r
option is to display all of the
input.If more than one file is specified, tail
precedes the output of each file with the following, in order to distinguish
files:
==> file
<==
The tail
utility exits 0 on
success, and >0 if an error occurs.
To display the last 500 lines of the file foo:
$ tail -500 foo
Keep /var/log/messages open, displaying to the standard output anything appended to the file:
$ tail -f
/var/log/messages
The tail
utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
specification.
The flags [-br
] are extensions to that
specification.
The historic command line syntax of tail
is supported by this implementation. The only difference between this
implementation and historic versions of tail
, once
the command line syntax translation has been done, is that the
-b
, -c
and
-n
options modify the -r
option, i.e., -r -c 4
displays the last 4 characters
of the last line of the input, while the historic tail (using the historic
syntax -4cr
) would ignore the
-c
option and display the last 4 lines of the
input.
A tail
command appeared in
Version 7 AT&T UNIX.
October 25, 2015 | OpenBSD-6.1 |