TAIL(1) BSD General Commands Manual TAIL(1)NAMEtail — display the last part of a file
SYNOPSIStail [-F | -f | -r] [-q] [-b number | -c number | -n number] [file ...]
The tail utility displays the contents of file or, by default, its stan‐
dard 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 loca‐
tion 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 The -f option causes tail to not 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 the standard input is a
pipe, but not if it is a FIFO.
-F The -F option implies the -f option, but tail will also check to
see if the file being followed has been renamed or rotated. The
file is closed and reopened when tail detects that the filename
being read from has a new inode number.
If the file being followed does not (yet) exist or if it is
removed, tail will keep looking and will display the file from
the beginning if and when it is created.
The -F option is the same as the -f option if reading from stan‐
dard input rather than a file.
The location is number lines.
-q Suppresses printing of headers when multiple files are being
-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 a single file is specified, each file is preceded by a
header consisting of the string “==> XXX <==” where XXX is the name of
the file unless -q flag is specified.
The tail utility exits 0 on success, and >0 if an error occurs.
SEE ALSOcat(1), head(1), sed(1)STANDARDS
The tail utility is expected to be a superset of the IEEE Std 1003.2-1992
(“POSIX.2”) specification. In particular, the -F, -b and -r options are
extensions to that standard.
The historic command line syntax of tail is supported by this implementa‐
tion. The only difference between this implementation and historic ver‐
sions 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” dis‐
plays the last 4 characters of the last line of the input, while the his‐
toric 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 PWB UNIX.
BSD June 05, 2009 BSD