| TAIL(1) | General Commands Manual | TAIL(1) | 
tail —
| tail | -qv[-f|-F|-r]
      [-bnumber |-cnumber |-nnumber]
      [file ...] | 
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:
-b
    number-c
    number-f-f option causes tail
      not to stop when end of file is reached, but rather to wait for additional
      data to be appended to the input. The -f option is
      ignored if there are no file arguments and the standard input is a pipe or
      a FIFO.-F-F option is the same as the
      -f option, except that every five seconds
      tail will check to see if the file named on the
      command line has been shortened or moved (it is considered moved if the
      inode or device number changes) and, if so, it will close the current
      file, open the filename given, print out the entire contents, and continue
      to wait for more data to be appended. This option is used to follow log
      files though rotation by
      newsyslog(8) or similar
      programs.-n
    number-q-r-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.-vIf more than a single file is specified, or the
    -v option is used, each file is preceded by a header
    consisting of the string “==> XXX <==” where
    “XXX” is the name of the file. The -q
    flag disables the printing of the header in all cases.
tail utility exits 0 on success,
  and >0 if an error occurs.
tail utility is expected to be a superset of the
  IEEE Std 1003.2-1992 (“POSIX.2”)
  specification. In particular, the -b,
  -r and -F options are
  extensions to that standard.
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.
tail command appeared in
  Version 7 AT&T UNIX.
-F option, tail
  will not detect a file truncation if, between the truncation and the next
  check of the file size, data written to the file make it larger than the last
  known file size.
| October 1, 2017 | NetBSD 10.0 |