tail(1) [freebsd man page]
TAIL(1) BSD General Commands Manual TAIL(1) NAME
tail -- display the last part of a file SYNOPSIS
tail [-F | -f | -r] [-q] [-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 start- ing 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 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 begin- ning if and when it is created. The -F option is the same as the -f option if reading from standard input rather than a file. -n number The location is number lines. -q Suppresses printing of headers when multiple files are being examined. -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. EXIT STATUS
The tail utility exits 0 on success, and >0 if an error occurs. EXAMPLES
To display the last 500 lines of the file foo: $ tail -n 500 foo Keep /var/log/messages open, displaying to the standard output anything appended to the file: $ tail -f /var/log/messages 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 -F, -b and -r 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 PWB UNIX. BSD
March 16, 2013 BSD
Check Out this Related Man Page
tail(1) 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] 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. 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 counting is 1. That is, -n+1 represents the first line of the file, -n-1 the last. The following operand is supported: file A path name of an input file. If no file operands are specified, the standard input is used. See largefile(5) for the description of the behavior of tail when encountering files greater than or equal to 2 Gbyte ( 2**31 bytes). 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 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. The following exit values are returned: 0 Successful completion. >0 An error occurred. 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 | +-----------------------------+-----------------------------+ cat(1), head(1), more(1), pg(1), dd(1M), attributes(5), environ(5), largefile(5), standards(5) 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. 13 Jul 2005 tail(1)