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(7) 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(7) 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(7) 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), attributes(7), environ(7),
largefile(7), standards(7), dd(8)

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)