head(P)                                                 head(P)





NAME
       head - copy the first part of files

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

DESCRIPTION
       The head utility shall copy its input files to the stan-
       dard output, ending the output for each file at a desig-
       nated point.

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

OPTIONS
       The  head  utility shall conform to the Base Definitions
       volume of IEEE Std 1003.1-2001,  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 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 only if no file oper-
       ands are specified. 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 internationaliza-
              tion  variables  that are unset or null. (See the
              Base Definitions volume of  IEEE Std 1003.1-2001,
              Section  8.2,  Internationalization Variables for
              the precedence of internationalization  variables
              used  to  determine  the  values  of locale cate-
              gories.)

       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 mes-
              sages 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 pre-
       cede 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
       The obsolescent - number form is withdrawn in this  ver-
       sion.  Applications should use the -n number option.

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  war-
       ranted its inclusion alongside tail.

       This standard version of head follows the Utility Syntax
       Guidelines.  The -n option was added to this new  inter-
       face  so  that  head  and  tail  would be more logically
       related.

       There is no -c option (as there is in tail)  because  it
       is  not  historical practice and because other utilities
       in this volume of IEEE Std 1003.1-2001  provide  similar
       functionality.

FUTURE DIRECTIONS
       None.

SEE ALSO
       sed , tail

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in
       electronic form from  IEEE  Std  1003.1,  2003  Edition,
       Standard  for Information Technology -- Portable Operat-
       ing System Interface (POSIX), The Open Group Base Speci-
       fications Issue 6, Copyright (C) 2001-2003 by the Insti-
       tute 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.open-
       group.org/unix/online.html .



POSIX                         2003                      head(P)
