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HEAD(1P)			    POSIX Programmer's Manual				 HEAD(1P)

PROLOG
       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME
       head -- copy the first part of files

SYNOPSIS
       head [-n number] [file...]

DESCRIPTION
       The  head utility shall copy its input files to the standard output, ending the output for
       each file at a designated point.

       Copying shall end at the point in each input file indicated by the -n number  option.  The
       option-argument number shall be counted in units of lines.

OPTIONS
       The  head  utility  shall  conform to the Base Definitions volume of POSIX.1-2008, Section
       12.2, Utility Syntax Guidelines.

       The following option shall be supported:

       -n number The first number lines of each input file shall be copied  to	standard  output.
		 The application shall ensure that the number option-argument is a positive deci-
		 mal integer.

       When a file contains less than number lines, it shall be copied to standard output in  its
       entirety. This shall not be an error.

       If no options are specified, head shall act as if -n 10 had been specified.

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 if no file operands are specified, and shall be used if a
       file operand is '-' and the implementation treats the '-' as meaning standard input.  Oth-
       erwise, the standard input shall not be used.  See the INPUT FILES section.

INPUT FILES
       Input files shall be text files, but the line  length  is  not  restricted  to  {LINE_MAX}
       bytes.

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

       LANG	 Provide a default value for the internationalization variables that are unset or
		 null. (See the Base Definitions volume of POSIX.1-2008,  Section  8.2,  Interna-
		 tionalization	Variables  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  inter-
		 nationalization 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 standard output shall contain designated portions of the input files.

       If multiple file operands are specified, head shall precede the output for each	with  the
       header:

	   "\n==> %s <==\n", <pathname>

       except that the first header written shall not include the initial <newline>.

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
       None.

EXAMPLES
       To  write  the  first  ten  lines of all files (except those with a leading period) in the
       directory:

	   head -- *

RATIONALE
       Although it is possible to simulate head with sed 10q for  a  single  file,  the  standard
       developers  decided  that  the  popularity of head on historical BSD systems warranted its
       inclusion alongside tail.

       POSIX.1-2008 version of head follows the Utility Syntax	Guidelines.  The  -n  option  was
       added to this new interface so that head and tail would be more logically related. Earlier
       versions of this standard allowed a -number option. This form is no  longer  specified  by
       POSIX.1-2008 but may be present in some implementations.

       There  is  no  -c  option  (as there is in tail) because it is not historical practice and
       because other utilities in this volume of POSIX.1-2008 provide similar functionality.

FUTURE DIRECTIONS
       None.

SEE ALSO
       sed, tail

       The Base Definitions volume of POSIX.1-2008, Chapter  8,  Environment  Variables,  Section
       12.2, Utility Syntax Guidelines

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.	(This  is
       POSIX.1-2008  with the 2013 Technical Corrigendum 1 applied.) In the event of any discrep-
       ancy 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group			       2013					 HEAD(1P)
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