display the last part of a
tail utility displays the contents of
file or, by default, its standard input, to the
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,
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.
- 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
tailwill reopen the file and continue. If the file is truncated,
tailwill reset its position to the beginning. This makes
tailmore useful for watching log files that may get rotated. The
-foption is ignored if there are no file arguments and the standard input is a pipe or a FIFO.
- The location is number lines.
-roption causes the input to be displayed in reverse order, by line. Additionally, this option changes the meaning of the
-noptions. When the
-roption 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
-roption is to display all of the input.
If more than one file is specified,
precedes the output of each file with the following, in order to distinguish
==> file <==
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)
tail utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
The flags [
-br] are extensions to that
The historic command line syntax of
is supported by this implementation. The only difference between this
implementation and historic versions of
the command line syntax translation has been done, is that the
-n options modify the
-r -c 4 displays the last 4 characters
of the last line of the input, while the historic tail (using the historic
-4cr) would ignore the
-c option and display the last 4 lines of the
tail command first appeared outside of
Bell Labs in PWB/UNIX 1.0.