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.1‐2017, 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.1‐2017,   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:

           "\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

       When  using head to process pathnames, it is recommended that LC_ALL, or at least LC_CTYPE
       and LC_COLLATE, are set to POSIX or C in the environment, since pathnames can contain byte
       sequences  that  do not form valid characters in some locales, in which case the utility's
       behavior would be undefined. In  the  POSIX  locale  each  byte  is  a  valid  single-byte
       character, and therefore this problem is avoided.

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.1‐2017 provide similar functionality.

FUTURE DIRECTIONS

       None.

SEE ALSO

       sed, tail

       The Base Definitions volume of POSIX.1‐2017, 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
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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 .