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 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 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.  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  variables that are unset or null. (See the Base Definitions volume of
		 POSIX.1-2008, 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

       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 Technol-
       ogy  --	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 discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Stan-
       dard 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)