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 correspond-
       ing 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 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 operands 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 internationalization 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 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:

	      "
==> %s <==
", <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 version.  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 warranted its inclusion alongside tail.

       This standard 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.

       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 Technol-
       ogy -- 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								  HEAD(1P)