TAIL(1) User Commands TAIL(1)


NAME


tail - deliver the last part of a file

SYNOPSIS


/usr/bin/tail [+-s number [lbcr]] [file]


/usr/bin/tail [-lbcr] [file]


/usr/bin/tail [+- number [lbcfF]] [file]


/usr/bin/tail [-lbcfF] [file]


/usr/xpg4/bin/tail [-f | -r] [-c number | -n number] [file]


/usr/xpg4/bin/tail [+- number [l | b | c] [f]] [file]


/usr/xpg4/bin/tail [+- number [l] [f | r]] [file]


DESCRIPTION


The tail utility copies the named file to the standard output beginning
at a designated place. If no file is named, the standard input is used.


Copying begins at a point in the file indicated by the -cnumber,
-nnumber, or +-number options (if +number is specified, begins at
distance number from the beginning; if -number is specified, from the end
of the input; if number is NULL, the value 10 is assumed). number is
counted in units of lines or byte according to the -c or -n options, or
lines, blocks, or bytes, according to the appended option l, b, or c.
When no units are specified, counting is by lines.

OPTIONS


The following options are supported for both /usr/bin/tail and
/usr/xpg4/bin/tail. The -r and -f options are mutually exclusive. If both
are specified on the command line, the -f option is ignored.

-b
Units of blocks.


-c
Units of bytes.


-f
Follow. If the input-file is not a pipe, tail does not terminate
after the last line of the input-file has been copied, but enters
an endless loop, wherein it watches the file for modifications and
attempts to read and copy further records from the input-file.
Thus it can be used to monitor the growth of a file that is being
written by some other process. If the watched file is truncated
tail will begin reading records from the start of the file.


-F
Follow named file. Operates as with -f, except that if the file is
moved (e.g. if a watched log file is rotated) tail will close the
original file and begin reading records from the start of the file
with the specified name if and when that file is recreated.


-l
Units of lines.


-r
Reverse. Copies lines from the specified starting point in the
file in reverse order. The default for r is to print the entire
file in reverse order.


/usr/xpg4/bin/tail
The following options are supported for /usr/xpg4/bin/tail only:

-c number
The number option-argument must be a decimal integer whose
sign affects the location in the file, measured in bytes,
to begin the copying:

+
Copying starts relative to the beginning of the
file.


-
Copying starts relative to the end of the file.


none
Copying starts relative to the end of the file.

The origin for counting is 1; that is, -c+1 represents the
first byte of the file, -c-1 the last.


-n number
Equivalent to -cnumber, except the starting location in the
file is measured in lines instead of bytes. The origin for
counting is 1. That is, -n+1 represents the first line of
the file, -n-1 the last.


OPERANDS


The following operand is supported:

file
A path name of an input file. If no file operands are specified,
the standard input is used.


USAGE


See largefile(5) for the description of the behavior of tail when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

EXAMPLES


Example 1: Using the tail Command




The following command prints 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.


example% tail -f fred


The next command prints 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:


example% tail -15cf fred


ENVIRONMENT VARIABLES


See environ(5) for descriptions of the following environment variables
that affect the execution of tail: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
and NLSPATH.

EXIT STATUS


The following exit values are returned:

0
Successful completion.


>0
An error occurred.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:

/usr/bin/tail


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|CSI | Enabled |
+---------------+-----------------+

/usr/xpg4/bin/tail


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|CSI | Enabled |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

SEE ALSO


cat(1), head(1), more(1), pg(1), dd(1M), attributes(5), environ(5),
largefile(5), standards(5)

NOTES


Piped tails relative to the end of the file are stored in a buffer, and
thus are limited in length. Various kinds of anomalous behavior can
happen with character special files.


July 13, 2005 TAIL(1)