TAIL(1) General Commands Manual TAIL(1)NAME
tail - deliver the last part of a file
tail _number[___][__] [ file ]
Tail 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 distance +number from the beginning, or -number from the end of the input. Number is counted in units of lines, blocks
or characters, according to the appended option l, b or c. When no units are specified, counting is by lines.
Specifying r causes tail to print lines from the end of the file in reverse order. The default for r is to print the entire file this way.
Specifying f causes tail to not quit at end of file, but rather wait and try to read repeatedly in hopes that the file will grow.
SEE ALSO dd(1)BUGS
Tails relative to the end of the file are treasured up in a buffer, and thus are limited in length.
Various kinds of anomalous behavior may happen with character special files.
4th Berkeley Distribution March 6, 1986 TAIL(1)
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TAIL(1) BSD General Commands Manual TAIL(1)NAME
tail -- display the last part of a file
tail [-f | -F | -r] [-b number | -c number | -n 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 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 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.
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 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.
The tail utility exits 0 on success, and >0 if an error occurs.
SEE ALSO cat(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 -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.
A tail command appeared in Version 7 AT&T UNIX.
When using the -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.
BSD June 6, 1993 BSD