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:
The location is number 512-byte blocks.
The location is number bytes.
-f Do not stop when end-of-file is reached; instead, wait for
additional data to be appended to the input. If the file is
replaced (i.e., the inode number changes), 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
The location is number lines.
-r The -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
cat(1), head(1), sed(1)
The tail utility is compliant with the IEEE Std 1003.1-2008 ("POSIX.1")
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.
OpenBSD 6.4 October 25, 2015 OpenBSD 6.4
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