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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 decimal 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 speci-
       fied.
OPERANDS
       The following operand shall be supported:
       file      A pathname of an input file. If no file operands  are  speci-
                 fied, 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.  Otherwise, 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 vari-
                 ables that are unset or null. (See the Base Definitions  vol-
                 ume  of POSIX.1-2008, 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 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  histori-
       cal 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 Electri-
       cal  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 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.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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                             HEAD(1P)