tail(1) [netbsd man page]
TAIL(1) BSD General Commands Manual TAIL(1) NAME
tail -- display the last part of a file SYNOPSIS
tail [-f | -F | -r] [-b number | -c number | -n number] [file ...] DESCRIPTION
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: -b number The location is number 512-byte blocks. -c number 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. -n 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 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. HISTORY
A tail command appeared in Version 7 AT&T UNIX. BUGS
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
Check Out this Related Man Page
tail(1) User Commands tail(1) NAME
tail - deliver the last part of a file SYNOPSIS
/usr/bin/tail [+-s number [lbcr]] [file] /usr/bin/tail [-lbcr] [file] /usr/bin/tail [+- number [lbcf]] [file] /usr/bin/tail [-lbcf] [file] /usr/xpg4/bin/tail [-f | -r] [-c number | -n number] [file] /usr/xpg4/bin/tail [+- number [l | b | c] [f]] [file] /usr/xpg4/bin/tail [+- number [l] [f | r]] [file] DESCRIPTION
The tail utility 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 a point in the file indicated by the -cnumber, -nnumber, or +-number options (if +number is specified, begins at distance number from the beginning; if -number is specified, from the end of the input; if number is NULL, the value 10 is assumed). number is counted in units of lines or byte according to the -c or -n options, or lines, blocks, or bytes, according to the appended option l, b, or c. When no units are specified, counting is by lines. OPTIONS
The following options are supported for both /usr/bin/tail and /usr/xpg4/bin/tail. The -r and -f options are mutually exclusive. If both are specified on the command line, the -f option is ignored. -b Units of blocks. -c Units of bytes. -f Follow. If the input-file is not a pipe, the program does not terminate after the line of the input-file has been copied, but enters an endless loop, wherein it sleeps for a second and then attempts to read and copy further records from the input-file. Thus it can be used to monitor the growth of a file that is being written by some other process. -l Units of lines. -r Reverse. Copies lines from the specified starting point in the file in reverse order. The default for r is to print the entire file in reverse order. /usr/xpg4/bin/tail The following options are supported for /usr/xpg4/bin/tail only: -c number The number option-argument must be a decimal integer whose sign affects the location in the file, measured in bytes, to begin the copying: + Copying starts relative to the beginning of the file. - Copying starts relative to the end of the file. none Copying starts relative to the end of the file. The origin for counting is 1; that is, -c+1 represents the first byte of the file, -c-1 the last. -n number Equivalent to -cnumber, except the starting location in the file is measured in lines instead of bytes. The origin for count- ing is 1. That is, -n+1 represents the first line of the file, -n-1 the last. OPERANDS
The following operand is supported: file A path name of an input file. If no file operands are specified, the standard input is used. USAGE
See largefile(5) for the description of the behavior of tail when encountering files greater than or equal to 2 Gbyte ( 2^31 bytes). EXAMPLES
Example 1 Using the tail Command The following command prints the last ten lines of the file fred, followed by any lines that are appended to fred between the time tail is initiated and killed. example% tail -f fred The next command prints the last 15 bytes of the file fred, followed by any lines that are appended to fred between the time tail is initi- ated and killed: example% tail -15cf fred ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of tail: LANG, LC_ALL, LC_CTYPE, LC_MES- SAGES, and NLSPATH. EXIT STATUS
The following exit values are returned: 0 Successful completion. >0 An error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: /usr/bin/tail +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |CSI |Enabled | +-----------------------------+-----------------------------+ /usr/xpg4/bin/tail +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWxcu4 | +-----------------------------+-----------------------------+ |CSI |Enabled | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
cat(1), head(1), more(1), pg(1), dd(1M), attributes(5), environ(5), largefile(5), standards(5) NOTES
Piped tails relative to the end of the file are stored in a buffer, and thus are limited in length. Various kinds of anomalous behavior can happen with character special files. SunOS 5.11 13 Jul 2005 tail(1)