tail(1) [osx 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. The -F option is ignored 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. 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
June 29, 2006 BSD
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tail(1) General Commands Manual tail(1) NAME
tail - deliver the last part of a file SYNOPSIS
number] [file] number] [file] number] [file] Obsolescent: [file] DESCRIPTION
copies the named file to the standard output beginning at a designated place. If no file is named, standard input is used. Command Forms can be used in three forms as indicated above: Copy file starting at number blocks from end or beginning of file. Copy file starting at number bytes from end or beginning of file. Copy file starting at number lines from end or beginning of file. with no options specified is equivalent to Options and Command-Line Arguments recognizes the following options and command-line arguments: Follow option. If the input file is a regular file or if file specifies a FIFO, do not terminate after the last line of the input file has been copied, but read and copy further bytes from the input file when they become available enters an end- less loop wherein it sleeps for one second then attempts to read and copy further records from the input file). This is useful when monitoring text being written to a file by another process. If no file argument is specified and the input is a pipe (FIFO), the option is ignored. number Decimal integer indicating quantity of output to be copied, measured in units specified by accompanying option. If number is preceded by a character, copy operation starts number units from beginning of file. If number is preceded by a character or the option name, copy operation starts number units from end of file. If number is not preceded by a or option, is assumed. If both the option and number are not specified, is assumed. Copy file beginning number 512-byte blocks from end or beginning of file. If number is not specified, is assumed. See number descrip- tion above. Copy file beginning number bytes from end or beginning of file. If number is not specified, is assumed. See number description above. Copy file beginning number lines from end or beginning of file. If number is not specified, is assumed. See number description above. file Name of file to be copied. If not specified, the standard input is used. If the option is specified, the input file can contain arbitrary data. Otherwise, the input file should be a text file. Obsolescent Form In the obsolescent form, option letters can be concatenated after the number argument to select blocks, bytes, or lines. If this syntax is used, must be the first argument given. If number is not specified, -10 is assumed. This version is provided for backward compatibility only. The forms discussed previously are recommended for portability. EXTERNAL INFLUENCES
Environment Variables determines the locale for the interpretation of sequences of bytes of text data as characters (e.g., single- versus multibyte characters in arguments and input files). determines the language in which messages are displayed. If or is not specified in the environment or is set to the empty string, the value of is used as a default for each unspecified or empty variable. If is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead of If any internationalization variable contains an invalid setting, behaves as if all internationalization variables are set to "C". See environ(5). International Code Set Support Single- and multi-byte character code sets are supported. However, the and options can break multi-byte characters and should be used with caution in a multi-byte locale environment. EXAMPLES
Print the last three lines in file to the standard output, and leave in ``follow'' mode: Print the last 15 bytes of file followed by any lines that are appended to after is initiated until it is killed: Three ways to print an entire file: WARNINGS
Various kinds of anomalous behavior may occur with character special files. For piped output, is limited in its output and depends on process limits. SEE ALSO
dd(1), head(1). STANDARDS CONFORMANCE
tail(1)