tail(1)
tail --
deliver the last part of a file
Synopsis
tail [-f] [-c number | -n number] [file]
tail [+/-number] [c | l | b] [f | r] [file]
Description
tail
copies the named file to the standard output beginning at a designated
place.
If no file is named, the standard input is used.
tail processes supplementary code set characters
according to the locale specified in the LC_CTYPE
environment variable (see LANG on
environ(5)),
except that
multibyte characters may be split, and so not be displayed correctly,
when the -b or -c options are specified.
Options
-c number-
If number has no sign, or has a negative sign (-),
tail will start copying at the absolute value of number
bytes from the end of the file. If number has a + in front
of it, copying starts at number bytes from the start of the file.
The origin for the value of number is 1. Therefore, -c +1
represents the first byte of the file, and -c -1 the last byte of
the file.
-n number-
This option is the same as the -c option, except the unit is
lines rather than bytes. Therefore, -n will start copying at
number lines from the start or end of the file, rather than
number bytes. The origin for the value of number is 1.
Therefore, -n +1 represents the first line of the file, and
-n -1 the last line of the file.
If neither -c nor -n is specified, the option
-n 10 will be assumed.
-f-
With the -f (follow) option, if the input is not a pipe,
the program will not terminate after the line of the input file has
been copied, but will enter an endless loop, wherein it sleeps for a
second and then attempts to read and copy further records from the
input file.
Thus it may be used to monitor the growth of a file that
is being written by some other process.
+/-[number][c|l|b][f|r]-
If
+number,
copying begins at distance number
from the beginning of the input.
If
-number,
copying begins at distance number
from the end of the input.
If
number
is null, the value 10 is assumed.
number
is counted in units of lines, blocks, or bytes,
according to the appended option
l,
b,
or
c.
When no units are specified, counting is by lines.
If number is not null, then:
-
+numberc
is equivalent to
-c +number
-
+numberl
is equivalent to
-n +number
-
-numberc
is equivalent to
-c number or
-c -number
-
-numberl
is equivalent to
-n number or
-n -number
The f option in this synopsis is identical to the normal -f
option.
The
r
option copies lines from the specified starting
point in the file in reverse order.
number is the count of lines from the end of the file, regardless
of the sign.
The default for
r
is to print the entire file in reverse order.
The
r
and
f
options are mutually exclusive.
Examples
The command:
tail -f fred
will print the last ten lines of the file
fred,
followed by any lines that are appended to
fred
between the time
tail
is initiated and killed.
As another example, the command:
tail -f -c 15 fred
will print the last 15 bytes of the file
fred,
followed by any lines that are appended to
fred
between the time
tail
is initiated and killed.
Files
/usr/lib/locale/locale/LC_MESSAGES/uxcore.abi-
language-specific message file (see LANG on
environ(5)).
References
cat(1),
dd(1M),
head(1),
more(1),
pg(1),
tail(1)
Notices
The tail command uses a buffer to seek back from the end of a file
and this limits the amount of data returned when using commands such as:
cat file | tail -n 1000 > /tmp/file
tail -n 1000 file
In addition, the number of lines returned by tail varies
depending on the length of the lines in the file; the total amount of data
returned is limited to the buffer size used (LINE_MAX*10 bytes, or
about 20Kbytes).
The tail command does not work reliably
with character special files.
The second synopsis form
(+/-[number][c|l|b][f|r])
may be removed in future releases, and so should be avoided.
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004