tail(1) tail(1)
NAME [Toc] [Back]
tail - deliver the last part of a file
SYNOPSIS [Toc] [Back]
tail [-f] [-b number] [file]
tail [-f] [-c number] [file]
tail [-f] [-n number] [file]
Obsolescent:
tail [+-[number][l|b|c] [-f] [file]
DESCRIPTION [Toc] [Back]
tail copies the named file to the standard output beginning at a
designated place. If no file is named, standard input is used.
Command Forms [Toc] [Back]
tail can be used in three forms as indicated above:
tail -b number... Copy file starting at number blocks from
end or beginning of file.
tail -c number... Copy file starting at number bytes from end
or beginning of file.
tail -n number...
tail number... Copy file starting at number lines from end
or beginning of file.
tail with no options specified is equivalent to tail -n 10....
Options and Command-Line Arguments [Toc] [Back]
tail recognizes the following options and command-line arguments:
-f Follow option. If the input file is a regular
file or if file specifies a FIFO, do not terminate
after the last line of the input file has been
copied, but read and copy further bytes from the
input file when they become available (tail enters
an endless loop wherein it sleeps for one second
then attempts to read and copy further records
from the input file). This is useful when
monitoring text being written to a file by another
process. If no file argument is specified and the
input is a pipe (FIFO), the -f option is ignored.
number Decimal integer indicating quantity of output to
be copied, measured in units specified by
accompanying option. If number is preceded by a +
character, copy operation starts number units from
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beginning of file. If number is preceded by a -
character or the option name, copy operation
starts number units from end of file. If number
is not preceded by a b, c, or n option, -n is
assumed. If both the option and number are not
specified, -n 10 is assumed.
-b number Copy file beginning number 512-byte blocks from
end or beginning of file. If number is not
specified, -b 10 is assumed. See number
description above.
-c number Copy file beginning number bytes from end or
beginning of file. If number is not specified, -c
10 is assumed. See number description above.
-n number Copy file beginning number lines from end or
beginning of file. If number is not specified, -n
10 is assumed. See number description above.
file Name of file to be copied. If not specified, the
standard input is used.
If the -c option is specified, the input file can contain arbitrary
data. Otherwise, the input file should be a text file.
Obsolescent Form [Toc] [Back]
In the obsolescent form, option letters can be concatenated after the
number argument to select blocks, bytes, or lines. If this syntax is
used, +-number must be the first argument given. If number is not
specified, -10 is assumed. This version is provided for backward
compatibility only. The forms discussed previously are recommended
for portability.
EXTERNAL INFLUENCES [Toc] [Back]
Environment Variables
LC_CTYPE determines the locale for the interpretation of sequences of
bytes of text data as characters (e.g., single- versus multibyte
characters in arguments and input files).
LC_MESSAGES determines the language in which messages are displayed.
If LC_CTYPE or LC_MESSAGES is not specified in the environment or is
set to the empty string, the value of LANG is used as a default for
each unspecified or empty variable. If LANG is not specified or is
set to the empty string, a default of "C" (see lang(5)) is used
instead of LANG.
If any internationalization variable contains an invalid setting, tail
behaves as if all internationalization variables are set to "C". See
environ(5).
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International Code Set Support [Toc] [Back]
Single- and multi-byte character code sets are supported. However,
the b and c options can break multi-byte characters and should be used
with caution in a multi-byte locale environment.
EXAMPLES [Toc] [Back]
Print the last three lines in file file1 to the standard output, and
leave tail in ``follow'' mode:
tail -fn 3 file1
tail -3 -f file1
Print the last 15 bytes of file logfile followed by any lines that are
appended to logfile after tail is initiated until it is killed:
tail -fc15 logfile
tail -f -c 15 logfile
Three ways to print an entire file:
tail -b +1 file
tail -c +1 file
tail -n +1 file
WARNINGS [Toc] [Back]
Various kinds of anomalous behavior may occur with character special
files. For piped output, tail is limited in its output and depends on
process limits.
SEE ALSO [Toc] [Back]
dd(1), head(1).
STANDARDS CONFORMANCE [Toc] [Back]
tail: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2
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