tail

⇒ gibt die letzten (10) Zeilen einer Datei aus.


theoretische Verwendung:

tail DATEI                     ⇒ gibt die letzten 10 Zeilen einer Datei aus


Beispiel:

tail -f # DATEI                ⇒ gibt die letzten 10 Zeilen einer Datei aus und aktualisiert diese alle # sec.
     -n #                      ⇒ gibt die letzten # Zeilen aus


siehe auch head



man page:

TAIL(P)                    POSIX Programmer's Manual                   TAIL(P)



NAME
       tail - copy the last part of a file

SYNOPSIS
       tail [-f][ -c number| -n number][file]

DESCRIPTION
       The  tail  utility  shall  copy  its  input file to the standard output
       beginning at a designated place.

       Copying shall begin at the point in the file indicated by the -c number
       or  -n  number  options. The option-argument number shall be counted in
       units of lines or bytes, according to the options -n and -c. Both  line
       and byte counts start from 1.

       Tails  relative  to  the  end  of  the file may be saved in an internal
       buffer, and thus may be limited in length. Such a buffer, if any, shall
       be no smaller than {LINE_MAX}*10 bytes.

OPTIONS
       The  tail  utility  shall  conform  to  the  Base Definitions volume of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -c  number
              The application shall ensure that the number option-argument  is
              a  decimal  integer whose sign affects the location in the file,
              measured in bytes, to begin the copying:

                       Sign   Copying Starts
                       +      Relative to the beginning of the file.
                       -      Relative to the end of the file.
                       none   Relative to the end of the file.

       The origin for counting shall be 1; that is, -c +1 represents the first
       byte of the file, -c -1 the last.

       -f     If the input file is a regular file or if the file operand spec-
              ifies 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. If  no  file  operand  is
              specified  and  standard input is a pipe, the -f option shall be
              ignored. If the input file is not a FIFO, pipe, or regular file,
              it is unspecified whether or not the -f option shall be ignored.

       -n  number
              This option shall be equivalent to -c number, except the  start-
              ing  location  in the file shall be measured in lines instead of
              bytes. The origin for counting shall be 1; that is, -n +1 repre-
              sents the first line of the file, -n -1 the last.


       If neither -c nor -n is specified, -n 10 shall be assumed.

OPERANDS
       The following operand shall be supported:

       file   A  pathname of an input file. If no file operands are specified,
              the standard input shall be used.

STDIN
       The standard input shall be used only if no file  operands  are  speci-
       fied. See the INPUT FILES section.

INPUT FILES
       If  the  -c  option  is specified, the input file can contain arbitrary
       data; otherwise, the input file shall be a text file.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of tail:

       LANG   Provide  a  default value for the internationalization variables
              that are unset or null. (See  the  Base  Definitions  volume  of
              IEEE Std 1003.1-2001,  Section  8.2,  Internationalization Vari-
              ables for the precedence of internationalization variables  used
              to determine the values of locale categories.)

       LC_ALL If  set  to a non-empty string value, override the values of all
              the other internationalization variables.

       LC_CTYPE
              Determine the locale for  the  interpretation  of  sequences  of
              bytes  of  text  data as characters (for example, single-byte as
              opposed to multi-byte characters in arguments and input  files).

       LC_MESSAGES
              Determine  the  locale  that should be used to affect the format
              and contents of diagnostic messages written to standard error.

       NLSPATH
              Determine the location of message catalogs for the processing of
              LC_MESSAGES .

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       The  designated  portion of the input file shall be written to standard
       output.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The -c option should be used with caution when the input is a text file
       containing  multi-byte  characters; it may produce output that does not
       start on a character boundary.

       Although the input file to tail can be any type, the results might  not
       be  what would be expected on some character special device files or on
       file  types  not  described  by  the  System   Interfaces   volume   of
       IEEE Std 1003.1-2001.  Since  this  volume of IEEE Std 1003.1-2001 does
       not specify the block size used when doing input, tail  need  not  read
       all of the data from devices that only perform block transfers.

EXAMPLES
       The -f option can be used to monitor the growth of a file that is being
       written by some other process. For example, the command:
       
       
              tail -f fred

       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. As
       another example, the command:


              tail -f -c 15 fred

       prints the last 15 bytes of the file fred, followed by any  bytes  that
       are appended to fred between the time tail is initiated and killed.

RATIONALE
       This  version  of  tail was created to allow conformance to the Utility
       Syntax Guidelines. The historical -b option was omitted because of  the
       general  non-portability  of  block-sized  units of text. The -c option
       historically    meant    "characters",    but    this     volume     of
       IEEE Std 1003.1-2001 indicates that it means "bytes". This was selected
       to allow reasonable implementations when multi-byte characters are pos-
       sible; it was not named -b to avoid confusion with the historical -b.

       The  origin  of  counting  both  lines  and  bytes  is  1, matching all
       widespread historical implementations.

       The restriction on the internal buffer is a compromise between the his-
       torical  System V implementation of 4096 bytes and the BSD 32768 bytes.

       The -f option has been implemented as a loop that sleeps for  1  second
       and  copies  any  bytes  that are available. This is sufficient, but if
       more efficient methods of determining when new data are  available  are
       developed, implementations are encouraged to use them.

       Historical  documentation  indicates that tail ignores the -f option if
       the input file is a pipe (pipe and FIFO on systems that support FIFOs).
       On  BSD-based  systems,  this has been true; on System V-based systems,
       this was true when input was taken from standard input, but it did  not
       ignore  the  -f flag if a FIFO was named as the file operand. Since the
       -f option is not useful on pipes  and  all  historical  implementations
       ignore -f if no file operand is specified and standard input is a pipe,
       this volume of IEEE Std 1003.1-2001 requires  this  behavior.  However,
       since   the   -f   option   is   useful  on  a  FIFO,  this  volume  of
       IEEE Std 1003.1-2001 also requires that if standard input is a FIFO  or
       a  FIFO is named, the -f option shall not be ignored. Although histori-
       cal behavior does not ignore the -f option for other file  types,  this
       is  unspecified  so  that  implementations are allowed to ignore the -f
       option if it is known that the file cannot be extended.

       This was changed to the current form based on comments noting  that  -c
       was almost never used without specifying a number and that there was no
       need to specify -l if -n number was given.

FUTURE DIRECTIONS
       None.

SEE ALSO
       head


COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the  referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .


IEEE/The Open Group                  2003                              TAIL(P)

linux/tail.txt · Zuletzt geändert: 2015/07/06 22:32 (Externe Bearbeitung)