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MORE(P) 			    POSIX Programmer's Manual				  MORE(P)

NAME
       more - display files on a page-by-page basis

SYNOPSIS
       more [-ceisu][-n number][-p command][-t tagstring][file ...]

DESCRIPTION
       The  more utility shall read files and either write them to the terminal on a page-by-page
       basis or filter them to standard output. If standard output is not a terminal device,  all
       input  files  shall  be copied to standard output in their entirety, without modification,
       except as specified for the -s option.  If standard output is a terminal device, the files
       shall  be  written  a  number of lines (one screenful) at a time under the control of user
       commands. See the EXTENDED DESCRIPTION section.

       Certain block-mode terminals do not have all the capabilities  necessary  to  support  the
       complete more definition; they are incapable of accepting commands that are not terminated
       with a <newline>.  Implementations that support such terminals shall provide an	operating
       mode  to more in which all commands can be terminated with a <newline> on those terminals.
       This mode:

	* Shall be documented in the system documentation

	* Shall, at invocation, inform the user of the	terminal  deficiency  that  requires  the
	  <newline>  usage  and  provide  instructions	on  how this warning can be suppressed in
	  future invocations

	* Shall not be required for implementations supporting only fully capable terminals

	* Shall not affect commands already requiring <newline>s

	* Shall not affect users on the capable terminals from using more as  described  in  this
	  volume of IEEE Std 1003.1-2001

OPTIONS
       The  more  utility  shall  conform to the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -c     If a screen is to be written that has no lines in common with the  current  screen,
	      or  more is writing its first screen, more shall not scroll the screen, but instead
	      shall redraw each line of the screen in turn, from the top of  the  screen  to  the
	      bottom.  In  addition,  if  more	is  writing its first screen, the screen shall be
	      cleared. This option may be silently ignored on devices with insufficient  terminal
	      capabilities.

       -e     By  default,  more  shall  exit immediately after writing the last line of the last
	      file in the argument list. If the -e option is specified:

	       1. If there is only a single file in the argument list  and  that  file	was  com-
		  pletely displayed on a single screen, more shall exit immediately after writing
		  the last line of that file.

	       2. Otherwise, more shall exit only after reaching end-of-file on the last file  in
		  the  argument  list  twice  without  an intervening operation. See the EXTENDED
		  DESCRIPTION section.

       -i     Perform pattern matching in searches without regard to case; see the  Base  Defini-
	      tions  volume  of  IEEE Std 1003.1-2001,	Section  9.2,  Regular Expression General
	      Requirements.

       -n  number
	      Specify the number of lines per screenful. The number argument is a positive  deci-
	      mal  integer.  The  -n  option  shall  override  any values obtained from any other
	      source.

       -p  command
	      Each time a screen from a new file is displayed  or  redisplayed	(including  as	a
	      result  of more commands; for example, :p), execute the more command(s) in the com-
	      mand arguments in the order specified, as if entered by the user	after  the  first
	      screen  has been displayed. No intermediate results shall be displayed (that is, if
	      the command is a movement to a screen different from the normal first screen,  only
	      the  screen  resulting from the command shall be displayed.) If any of the commands
	      fail for any reason, an informational message to this effect shall be written,  and
	      no further commands specified using the -p option shall be executed for this file.

       -s     Behave as if consecutive empty lines were a single empty line.

       -t  tagstring
	      Write the screenful of the file containing the tag named by the tagstring argument.
	      See the ctags utility. The tags feature represented by -t tagstring and the :t com-
	      mand  is optional. It shall be provided on any system that also provides a conform-
	      ing implementation of ctags; otherwise, the use of -t produces undefined results.

       The filename resulting from the -t option shall be logically added as a prefix to the list
       of  command  line  files,  as  if specified by the user. If the tag named by the tagstring
       argument is not found, it shall be an error, and more shall take no further action.

       If the tag specifies a line number, the first line of the display shall contain the begin-
       ning  of  that  line.  If the tag specifies a pattern, the first line of the display shall
       contain the beginning of the matching text from the first line of the file  that  contains
       that  pattern.  If  the	line does not exist in the file or matching text is not found, an
       informational message to this effect shall  be  displayed,  and	more  shall  display  the
       default screen as if -t had not been specified.

       If  both the -t tagstring and -p command options are given, the -t tagstring shall be pro-
       cessed first; that is, the file and starting line for the display shall be as specified by
       -t,  and then the -p more command shall be executed. If the line (matching text) specified
       by the -t command does not exist (is not found), no -p more command shall be executed  for
       this file at any time.

       -u     Treat  a	<backspace> as a printable control character, displayed as an implementa-
	      tion-defined character sequence (see the EXTENDED DESCRIPTION section), suppressing
	      backspacing and the special handling that produces underlined or standout mode text
	      on some terminal types. Also, do not ignore a <carriage-return> at  the  end  of	a
	      line.

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. If a file is '-' , the standard input shall be read at that point in
	      the sequence.

STDIN
       The  standard input shall be used only if no file operands are specified, or if a file op-
       erand is '-' .

INPUT FILES
       The input files being examined shall be text files. If  standard  output  is  a	terminal,
       standard  error shall be used to read commands from the user. If standard output is a ter-
       minal, standard error is not readable, and command input is needed, more  may  attempt  to
       obtain  user  commands  from  the controlling terminal (for example, /dev/tty); otherwise,
       more shall terminate with an error indicating that it was unable to read user commands. If
       standard  output  is  not  a  terminal,	no error shall result if standard error cannot be
       opened for reading.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of more:

       COLUMNS
	      Override the system-selected horizontal display line size. See the Base Definitions
	      volume  of  IEEE Std 1003.1-2001, Chapter 8, Environment Variables for valid values
	      and results when it is unset or null.

       EDITOR Used by the v command to select an editor. See the EXTENDED DESCRIPTION section.

       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, Inter-
	      nationalization 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 interna-
	      tionalization variables.

       LC_COLLATE

	      Determine the locale for the behavior of ranges, equivalence  classes,  and  multi-
	      character collating elements within regular expressions.

       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  argu-
	      ments and input files) and the behavior of character classes within regular expres-
	      sions.

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error and informative messages written to stan-
	      dard output.

       NLSPATH
	      Determine the location of message catalogs for the processing of LC_MESSAGES .

       LINES  Override the system-selected vertical screen size, used as the number of lines in a
	      screenful.  See  the  Base  Definitions  volume of IEEE Std 1003.1-2001, Chapter 8,
	      Environment Variables for valid values and results when it is unset or null. The -n
	      option  shall take precedence over the LINES variable for determining the number of
	      lines in a screenful.

       MORE   Determine a string containing options described in  the  OPTIONS	section  preceded
	      with hyphens and <blank>-separated as on the command line. Any command line options
	      shall be processed after those in the MORE variable, as if the command line were:

	      more $MORE options operands

       The MORE variable shall take precedence over the TERM and LINES variables for  determining
       the number of lines in a screenful.

       TERM   Determine  the  name  of	the  terminal type. If this variable is unset or null, an
	      unspecified default terminal type is used.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       The standard output shall be used to write the contents of the input files.

STDERR
       The standard error shall be used for diagnostic messages and user commands (see the  INPUT
       FILES section), and, if standard output is a terminal device, to write a prompting string.
       The prompting string shall appear on the screen line below the last line of the file  dis-
       played  in  the current screenful. The prompt shall contain the name of the file currently
       being examined and shall contain an end-of-file indication and the name of the next  file,
       if  any,  when  prompting at the end-of-file. If an error or informational message is dis-
       played, it is unspecified whether it is contained in the prompt. If it is not contained in
       the  prompt,  it shall be displayed and then the user shall be prompted for a continuation
       character, at which point another message or the user prompt may be displayed. The  prompt
       is otherwise unspecified. It is unspecified whether informational messages are written for
       other user commands.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       The following section describes the behavior of more when the standard output is a  termi-
       nal  device.  If  the  standard	output is not a terminal device, no options other than -s
       shall have any effect, and all input files shall be copied to  standard	output	otherwise
       unmodified, at which time more shall exit without further action.

       The number of lines available per screen shall be determined by the -n option, if present,
       or by examining values in the environment (see the ENVIRONMENT VARIABLES section). If nei-
       ther method yields a number, an unspecified number of lines shall be used.

       The maximum number of lines written shall be one less than this number, because the screen
       line after the last line written shall be used to write a user prompt and user  input.  If
       the  number  of	lines  in  the	screen is less than two, the results are undefined. It is
       unspecified whether user input is permitted to be longer than the remainder of the  single
       line where the prompt has been written.

       The  number  of	columns available per line shall be determined by examining values in the
       environment (see the ENVIRONMENT VARIABLES section), with a default value as described  in
       the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables.

       Lines that are longer than the display shall be folded; the length at which folding occurs
       is unspecified, but should be appropriate for the output device. Folding may occur between
       glyphs of single characters that take up multiple display columns.

       When  standard output is a terminal and -u is not specified, more shall treat <backspace>s
       and <carriage-return>s specially:

	* A character, followed first by a sequence of n <backspace>s (where n is the same as the
	  number  of  column positions that the character occupies), then by n underscore charac-
	  ters ( '_' ), shall cause that character to be written as underlined text, if the  ter-
	  minal   type	 supports  that.  The  n  underscore  characters,  followed  first  by	n
	  <backspace>s, then any character with n column positions, shall also cause that charac-
	  ter to be written as underlined text, if the terminal type supports that.

	* A  sequence  of  n  <backspace>s (where n is the same as the number of column positions
	  that the previous character occupies) that  appears  between	two  identical	printable
	  characters  shall  cause  the first of those two characters to be written as emboldened
	  text (that is, visually brighter, standout mode, or inverse-video mode), if the  termi-
	  nal  type  supports that, and the second to be discarded. Immediately subsequent occur-
	  rences of <backspace>/ character pairs for that same character shall also be discarded.
	  (For example, the sequence "a\ba\ba\ba" is interpreted as a single emboldened 'a' .)

	* The  more  utility shall logically discard all other <backspace>s from the line as well
	  as the character which precedes them, if any.

	* A <carriage-return> at the end of a line shall be ignored, rather than being written as
	  a non-printable character, as described in the next paragraph.

       It  is  implementation-defined how other non-printable characters are written. Implementa-
       tions should use the same format that they use for the ex print command; see  the  OPTIONS
       section within the ed utility. It is unspecified whether a multi-column character shall be
       separated if it crosses a display line boundary; it shall not be discarded.  The  behavior
       is  unspecified if the number of columns on the display is less than the number of columns
       any single character in the line being displayed would occupy.

       When each new file is displayed (or redisplayed), more shall write the first screen of the
       file.  Once  the initial screen has been written, more shall prompt for a user command. If
       the execution of the user command results in a screen that has lines in	common	with  the
       current screen, and the device has sufficient terminal capabilities, more shall scroll the
       screen; otherwise, it is unspecified whether the screen is scrolled or redrawn.

       For all files but the last (including standard input if no file was specified, and for the
       last  file  as  well,  if the -e option was not specified), when more has written the last
       line in the file, more shall prompt for a user command.	This  prompt  shall  contain  the
       name  of  the next file as well as an indication that more has reached end-of-file. If the
       user command is f, <control>-F, <space>, j, <newline>, d, <control>-D, or  s,  more  shall
       display the next file. Otherwise, if displaying the last file, more shall exit. Otherwise,
       more shall execute the user command specified.

       Several of the commands described in this section display a previous screen from the input
       stream. In the case that text is being taken from a non-rewindable stream, such as a pipe,
       it is implementation-defined how much backwards motion is supported. If a  command  cannot
       be  executed  because of a limitation on backwards motion, an error message to this effect
       shall be displayed, the current screen shall not change, and the user  shall  be  prompted
       for another command.

       If  a  command  cannot  be performed because there are insufficient lines to display, more
       shall alert the terminal. If a command cannot be performed because there are  insufficient
       lines to display or a / command fails: if the input is the standard input, the last screen
       in the file may be displayed; otherwise, the current file and screen shall not change, and
       the user shall be prompted for another command.

       The  interactive commands in the following sections shall be supported.	Some commands can
       be preceded by a decimal integer, called count in the following descriptions. If not spec-
       ified  with  the command, count shall default to 1. In the following descriptions, pattern
       is  a  basic  regular  expression,  as  described  in  the  Base  Definitions  volume   of
       IEEE Std 1003.1-2001,  Section  9.3, Basic Regular Expressions. The term "examine" is his-
       torical usage meaning "open the file  for  viewing'';  for  example,  more  foo	would  be
       expressed as examining file foo.

       In the following descriptions, unless otherwise specified, line is a line in the more dis-
       play, not a line from the file being examined.

       In the following descriptions, the current position refers to two things:

	1. The position of the current line on the screen

	2. The line number (in the file) of the current line on the screen

       Usually, the line on the screen corresponding to the current position is the third line on
       the  screen.  If this is not possible (there are fewer than three lines to display or this
       is the first page of the file, or it is the last page of the file), then the current posi-
       tion is either the first or last line on the screen as described later.

   Help
       Synopsis:

	      h

       Write  a summary of these commands and other implementation-defined commands. The behavior
       shall be as if the more utility were executed with the -e option on a file that	contained
       the  summary  information. The user shall be prompted as described earlier in this section
       when end-of-file is reached. If the user command is one of those specified to continue  to
       the next file, more shall return to the file and screen state from which the h command was
       executed.

   Scroll Forward One Screenful
       Synopsis:

	      [count]f
	      [count]<control>-F

       Scroll forward count lines, with a default of one screenful.  If count is  more	than  the
       screen size, only the final screenful shall be written.

   Scroll Backward One Screenful
       Synopsis:

	      [count]b
	      [count]<control>-B

       Scroll backward count lines, with a default of one screenful (see the -n option). If count
       is more than the screen size, only the final screenful shall be written.

   Scroll Forward One Line
       Synopsis:

	      [count]<space>
	      [count]j
	      [count]<newline>

       Scroll forward count lines. The default count for the <space> shall be one screenful;  for
       j  and <newline>, one line. The entire count lines shall be written, even if count is more
       than the screen size.

   Scroll Backward One Line
       Synopsis:

	      [count]k

       Scroll backward count lines. The entire count lines shall be written,  even  if	count  is
       more than the screen size.

   Scroll Forward One Half Screenful
       Synopsis:

	      [count]d
	      [count]<control>-D

       Scroll  forward	count  lines,  with a default of one half of the screen size. If count is
       specified, it shall become the new default for subsequent d, <control>-D, and u commands.

   Skip Forward One Line
       Synopsis:

	      [count]s

       Display the screenful beginning with the line count lines after the last line on the  cur-
       rent  screen.  If  count  would	cause  the current position to be such that less than one
       screenful would be written, the last screenful in the file shall be written.

   Scroll Backward One Half Screenful
       Synopsis:

	      [count]u
	      [count]<control>-U

       Scroll backward count lines, with a default of one half of the screen size.  If	count  is
       specified,  it  shall  become  the new default for subsequent d, <control>-D, u, and <con-
       trol>-U commands. The entire count lines shall be written, even if count is more than  the
       screen size.

   Go to Beginning of File
       Synopsis:

	      [count]g

       Display the screenful beginning with line count.

   Go to End-of-File
       Synopsis:

	      [count]G

       If  count  is  specified,  display the screenful beginning with the line count. Otherwise,
       display the last screenful of the file.

   Refresh the Screen
       Synopsis:

	      r
	      <control>-L

       Refresh the screen.

   Discard and Refresh
       Synopsis:

	      R

       Refresh the screen, discarding any buffered input. If the current  file	is  non-seekable,
       buffered  input shall not be discarded and the R command shall be equivalent to the r com-
       mand.

   Mark Position
       Synopsis:

	      mletter

       Mark the current position with the letter named by letter,  where  letter  represents  the
       name  of  one  of  the lowercase letters of the portable character set. When a new file is
       examined, all marks may be lost.

   Return to Mark
       Synopsis:

	      'letter

       Return to the position that was previously marked with the letter named by letter,  making
       that line the current position.

   Return to Previous Position
       Synopsis:

	      ''

       Return  to  the	position from which the last large movement command was executed (where a
       "large movement" is defined as any movement of more than a screenful of lines). If no such
       movements have been made, return to the beginning of the file.

   Search Forward for Pattern
       Synopsis:

	      [count]/[!]pattern<newline>

       Display	the  screenful beginning with the countth line containing the pattern. The search
       shall start after the first line currently displayed. The null regular  expression  (  '/'
       followed  by  a	<newline>) shall repeat the search using the previous regular expression,
       with a default count. If the character '!' is included, the matching lines shall be  those
       that  do  not contain the pattern. If no match is found for the pattern, a message to that
       effect shall be displayed.

   Search Backward for Pattern
       Synopsis:

	      [count]?[!]pattern<newline>

       Display the screenful beginning with the countth previous line containing the pattern. The
       search  shall  start  on the last line before the first line currently displayed. The null
       regular expression ( '?' followed by a <newline>) shall repeat the search using the previ-
       ous  regular  expression, with a default count. If the character '!' is included, matching
       lines shall be those that do not contain the pattern.  If no match is found for	the  pat-
       tern, a message to that effect shall be displayed.

   Repeat Search
       Synopsis:

	      [count]n

       Repeat the previous search for countth line containing the last pattern (or not containing
       the last pattern, if the previous search was "/!" or "?!"  ).

   Repeat Search in Reverse
       Synopsis:

	      [count]N

       Repeat the search in the opposite direction of the previous search for  the  countth  line
       containing  the	last  pattern (or not containing the last pattern, if the previous search
       was "/!" or "?!" ).

   Examine New File
       Synopsis:

	      :e [filename]<newline>

       Examine a new file. If the filename argument is not specified, the current file	(see  the
       :n  and	:p  commands  below) shall be re-examined. The filename shall be subjected to the
       process of shell word expansions (see Word Expansions ); if more than  a  single  pathname
       results,  the  effects  are unspecified.  If filename is a number sign ( '#' ), the previ-
       ously examined file shall be re-examined. If filename is not  accessible  for  any  reason
       (including  that it is a non-seekable file), an error message to this effect shall be dis-
       played and the current file and screen shall not change.

   Examine Next File
       Synopsis:

	      [count]:n

       Examine the next file. If a number count is specified, the  countth  next  file	shall  be
       examined. If filename refers to a non-seekable file, the results are unspecified.

   Examine Previous File
       Synopsis:

	      [count]:p

       Examine the previous file. If a number count is specified, the countth previous file shall
       be examined. If filename refers to a non-seekable file, the results are unspecified.

   Go to Tag
       Synopsis:

	      :t tagstring<newline>

       If the file containing the tag named by the tagstring argument is not  the  current  file,
       examine the file, as if the :e command was executed with that file as the argument. Other-
       wise, or in addition, display the screenful beginning with the tag, as described  for  the
       -t option (see the OPTIONS section).  If the ctags utility is not supported by the system,
       the use of :t produces undefined results.

   Invoke Editor
       Synopsis:

	      v

       Invoke an editor to edit the current file being examined. If standard input is being exam-
       ined, the results are unspecified. The name of the editor shall be taken from the environ-
       ment variable EDITOR , or shall default to vi. If the last pathname component in EDITOR is
       either  vi  or ex, the editor shall be invoked with a -c linenumber command line argument,
       where linenumber is the line number of the file line containing the display line currently
       displayed  as the first line of the screen. It is implementation-defined whether line-set-
       ting options are passed to editors other than vi and ex.

       When the editor exits, more shall resume with the same file and screen as when the  editor
       was invoked.

   Display Position
       Synopsis:

	      =
	      <control>-G

       Write  a message for which the information references the first byte of the line after the
       last line of the file on the screen.  This message shall include the name of the file cur-
       rently being examined, its number relative to the total number of files there are to exam-
       ine, the line number in the file, the byte number and the total bytes  in  the  file,  and
       what  percentage  of the file precedes the current position. If more is reading from stan-
       dard input, or the file is shorter than a single screen, the line number, the byte number,
       the total bytes, and the percentage need not be written.

   Quit
       Synopsis:

	      q
	      :q
	      ZZ

       Exit more.

EXIT STATUS
       The following exit values shall be returned:

	0     Successful completion.

       >0     An error occurred.

CONSEQUENCES OF ERRORS
       If  an error is encountered accessing a file when using the :n command, more shall attempt
       to examine the next file in the	argument  list,  but  the  final  exit	status	shall  be
       affected.   If  an  error  is  encountered accessing a file via the :p command, more shall
       attempt to examine the previous file in the argument list, but the final exit status shall
       be  affected.   If an error is encountered accessing a file via the :e command, more shall
       remain in the current file and the final exit status shall not be affected.

       The following sections are informative.

APPLICATION USAGE
       When the standard output is not a terminal, only  the  -s  filter-modification  option  is
       effective.  This is based on historical practice. For example, a typical implementation of
       man pipes its output through more -s to squeeze excess white  space  for  terminal  users.
       When man is piped to lp, however, it is undesirable for this squeezing to happen.

EXAMPLES
       The -p allows arbitrary commands to be executed at the start of each file. Examples are:

       more  -p G  file1 file2

	      Examine each file starting with its last screenful.

       more  -p  100 file1 file2

	      Examine each file starting with line 100 in the current position (usually the third
	      line, so line 98 would be the first line written).

       more  -p  /100 file1 file2

	      Examine each file starting with the first line containing the string "100"  in  the
	      current position

RATIONALE
       The  more  utility,  available in BSD and BSD-derived systems, was chosen as the prototype
       for the POSIX file display program since it is more widely available than either the  pub-
       lic-domain  program less or than pg, a pager provided in System V. The 4.4 BSD more is the
       model for the features selected; it is almost fully upwards-compatible from  the  4.3  BSD
       version	in  wide  use and has become more amenable for vi users.  Several features origi-
       nally derived from various file editors, found in both less and pg,  have  been	added  to
       this volume of IEEE Std 1003.1-2001 as they have proved extremely popular with users.

       There  are  inconsistencies  between more and vi that result from historical practice. For
       example, the single-character commands h, f, b, and <space> are screen movers in more, but
       cursor  movers  in  vi. These inconsistencies were maintained because the cursor movements
       are not applicable to more and the powerful functionality achieved without the use of  the
       control key justifies the differences.

       The  tags  interface  has  been included in a program that is not a text editor because it
       promotes another degree of consistent operation with vi. It is conceivable that the paging
       environment  of	more  would  be  superior  for browsing source code files in some circum-
       stances.

       The operating mode referred to for block-mode terminals effectively adds  a  <newline>  to
       each  Synopsis  line  that currently has none. So, for example, d <newline> would page one
       screenful.  The mode could be triggered by a command line option, environment variable, or
       some  other  method.  The  details  are not imposed by this volume of IEEE Std 1003.1-2001
       because there are so few systems known to support such  terminals.  Nevertheless,  it  was
       considered  that  all systems should be able to support more given the exception cited for
       this small community of terminals because, in comparison to vi, the cursor  movements  are
       few and the command set relatively amenable to the optional <newline>s.

       Some  versions of more provide a shell escaping mechanism similar to the ex ! command. The
       standard developers did not consider that this was necessary in a paginator,  particularly
       given  the  wide  acceptance of multiple window terminals and job control features.  (They
       chose to retain such features in the editors and mailx because the shell interaction  also
       gives an opportunity to modify the editing buffer, which is not applicable to more.)

       The  -p (position) option replaces the + command because of the Utility Syntax Guidelines.
       In early proposals, it took a pattern argument, but historical less provided the more gen-
       eral  facility of a command. It would have been desirable to use the same -c as ex and vi,
       but the letter was already in use.

       The text stating "from a non-rewindable stream ... implementations may limit the amount of
       backwards  motion  supported"  would  allow  an implementation that permitted no backwards
       motion beyond text already on the screen. It was not possible to require a minimum  amount
       of  backwards  motion that would be effective for all conceivable device types. The imple-
       mentation should allow the user to back up as far as possible, within device  and  reason-
       able memory allocation constraints.

       Historically,  non-printable  characters  were displayed using the ARPA standard mappings,
       which are as follows:

	1. Printable characters are left alone.

	2. Control characters less than \177 are represented as followed by the character  offset
	   from the '@' character in the ASCII map; for example, \007 is represented as 'G' .

	3. \177 is represented as followed by '?' .

       The  display of characters having their eighth bit set was less standard.  Existing imple-
       mentations use hex (0x00), octal (\000), and a meta-bit	display.  (The	latter	displayed
       characters  with  their eighth bit set as the two characters "M-" , followed by the seven-
       bit display as described previously.) The latter probably has the best claim to historical
       practice because it was used with the -v option of 4 BSD and 4 BSD-derived versions of the
       cat utility since 1980.

       No specific display format  is  required  by  IEEE Std 1003.1-2001.   Implementations  are
       encouraged to conform to historic practice in the absence of any strong reason to diverge.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Shell Command Language , ctags , ed , ex , vi

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  MORE(P)
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