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VI(1P)                     POSIX Programmer's Manual                    VI(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       vi - screen-oriented (visual) display editor

SYNOPSIS
       vi [-rR][-c command][-t tagstring][-w size][file ...]

DESCRIPTION
       This  utility  shall  be provided on systems that both support the User Portability Utilities option and define
       the POSIX2_CHAR_TERM symbol. On other systems it is optional.

       The vi (visual) utility is a screen-oriented text editor. Only the open and visual  modes  of  the  editor  are
       described  in  IEEE Std 1003.1-2001; see the line editor ex for additional editing capabilities used in vi. The
       user can switch back and forth between vi and ex and execute ex commands from within vi.

       This reference page uses the term edit buffer to describe the current working text. No specific  implementation
       is  implied  by  this  term.  All  editing changes are performed on the edit buffer, and no changes to it shall
       affect any file until an editor command writes the file.

       When using vi, the terminal screen acts as a window into the editing buffer. Changes made to the editing buffer
       shall  be reflected in the screen display; the position of the cursor on the screen shall indicate the position
       within the editing buffer.

       Certain terminals do not have all the capabilities necessary to support the complete vi definition. When  these
       commands  cannot be supported on such terminals, this condition shall not produce an error message such as "not
       an editor command" or report a syntax error. The implementation may either  accept  the  commands  and  produce
       results on the screen that are the result of an unsuccessful attempt to meet the requirements of this volume of
       IEEE Std 1003.1-2001 or report an error describing the terminal-related deficiency.

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

       The following options shall be supported:

       -c  command
              See the ex command description of the -c option.

       -r     See the ex command description of the -r option.

       -R     See the ex command description of the -R option.

       -t  tagstring
              See the ex command description of the -t option.

       -w  size
              See the ex command description of the -w option.


OPERANDS
       See the OPERANDS section of the ex command for a description of the operands supported by the vi command.

STDIN
       If standard input is not a terminal device, the results are undefined.  The standard input consists of a series
       of commands and input text, as described in the EXTENDED DESCRIPTION section.

       If a read from the standard input returns an error, or if the editor detects an end-of-file condition from  the
       standard input, it shall be equivalent to a SIGHUP asynchronous event.

INPUT FILES
       See the INPUT FILES section of the ex command for a description of the input files supported by the vi command.

ENVIRONMENT VARIABLES
       See the ENVIRONMENT VARIABLES section of the ex command for the environment variables that affect the execution
       of the vi command.

ASYNCHRONOUS EVENTS
       See  the  ASYNCHRONOUS EVENTS section of the ex for the asynchronous events that affect the execution of the vi
       command.

STDOUT
       If standard output is not a terminal device, undefined results occur.

       Standard output may be used for writing prompts to the user, for informational messages, and for writing  lines
       from the file.

STDERR
       If standard output is not a terminal device, undefined results occur.

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       See  the  OUTPUT FILES section of the ex command for a description of the output files supported by the vi com-
       mand.

EXTENDED DESCRIPTION
       If the terminal does not have the capabilities necessary to support an unspecified portion of  the  vi  defini-
       tion, implementations shall start initially in ex mode or open mode.  Otherwise, after initialization, vi shall
       be in command mode; text input mode can be entered by one of several commands used to insert or change text. In
       text  input  mode, <ESC> can be used to return to command mode; other uses of <ESC> are described later in this
       section; see Terminate Command or Input Mode .

   Initialization in ex and vi
       See Initialization in ex and vi for a description of ex and vi initialization for the vi utility.

   Command Descriptions in vi
       The following symbols are used in this reference page to represent arguments to commands.

       buffer See the description of buffer in the EXTENDED  DESCRIPTION  section  of  the  ex  utility;  see  Command
              Descriptions in ex .

       In  open and visual mode, when a command synopsis shows both [ buffer] and [ count] preceding the command name,
       they can be specified in either order.

       count  A positive integer used as an optional argument to most commands, either to give a repeat count or as  a
              size. This argument is optional and shall default to 1 unless otherwise specified.

       The Synopsis lines for the vi commands <control>-G, <control>-L, <control>-R, <control>-], %, &, ^, D, m, M, Q,
       u, U, and ZZ do not have count as an optional argument. Regardless, it shall not be an error to specify a count
       to these commands, and any specified count shall be ignored.

       motion An  optional  trailing argument used by the !, <, >, c, d, and y commands, which is used to indicate the
              region of text that shall be affected by the command. The motion can be either one of the command  char-
              acters  repeated or one of several other vi commands (listed in the following table). Each of the appli-
              cable commands specifies the region of text matched by repeating the command; each command that  can  be
              used as a motion command specifies the region of text it affects.

       Commands that take motion arguments operate on either lines or characters, depending on the circumstances. When
       operating on lines, all lines that fall partially or wholly within the text region specified  for  the  command
       shall  be  affected. When operating on characters, only the exact characters in the specified text region shall
       be affected. Each motion command specifies this individually.

       When commands that may be motion commands are not used as motion commands, they shall set the current  position
       to the current line and column as specified.

       The following commands shall be valid cursor motion commands:


              <apostrophe>       (    -    j    H
              <carriage-return>  )    $    k    L
              <comma>            [[   %    l    M
              <control>-H        ]]   _    n    N
              <control>-N        {    ;    t    T
              <control>-P        }    ?    w    W
              <grave accent>     ^    b    B
              <newline>          +    e    E
              <space>            |    f    F
              <zero>             /    h    G

       Any  count  that is specified to a command that has an associated motion command shall be applied to the motion
       command. If a count is applied to both the command and its associated motion command, the effect shall be  mul-
       tiplicative.


       The following symbols are used in this section to specify locations in the edit buffer:

       current character

              The character that is currently indicated by the cursor.

       end of a line

              The  point located between the last non- <newline> (if any) and the terminating <newline> of a line. For
              an empty line, this location coincides with the beginning of the line.

       end of the edit buffer

              The location corresponding to the end of the last line in the edit buffer.


       The following symbols are used in this section to specify command actions:

       bigword
              In the POSIX locale, vi shall recognize four kinds of bigwords:

               1. A maximal sequence of non- <blank>s preceded and followed by <blank>s or the beginning or end  of  a
                  line or the edit buffer


               2. One or more sequential blank lines


               3. The first character in the edit buffer


               4. The last non- <newline> in the edit buffer


       word   In the POSIX locale, vi shall recognize five kinds of words:

               1. A maximal sequence of letters, digits, and underscores, delimited at both ends by:

                   * Characters other than letters, digits, or underscores


                   * The beginning or end of a line


                   * The beginning or end of the edit buffer



               2. A  maximal sequence of characters other than letters, digits, underscores, or <blank>s, delimited at
                  both ends by:

                   * A letter, digit, underscore


                   * <blank>s


                   * The beginning or end of a line


                   * The beginning or end of the edit buffer



               3. One or more sequential blank lines


               4. The first character in the edit buffer


               5. The last non- <newline> in the edit buffer


       section boundary

              A section boundary is one of the following:

               1. A line whose first character is a <form-feed>


               2. A line whose first character is an open curly brace ( '{' )


               3. A line whose first character is a period and whose second and third characters match a two-character
                  pair in the sections edit option (see ed)


               4. A  line whose first character is a period and whose only other character matches the first character
                  of a two-character pair in the sections edit option, where the second character of the two-character
                  pair is a <space>


               5. The first line of the edit buffer


               6. The  last line of the edit buffer if the last line of the edit buffer is empty or if it is a ]] or }
                  command; otherwise, the last non- <newline> of the last line of the edit buffer


       paragraph boundary

              A paragraph boundary is one of the following:

               1. A section boundary


               2. A line whose first character is a period and whose second and third characters match a two-character
                  pair in the paragraphs edit option (see ed)


               3. A  line whose first character is a period and whose only other character matches the first character
                  of a two-character pair in the paragraphs edit option,  where  the  second  character  of  the  two-
                  character pair is a <space>


               4. One or more sequential blank lines


       remembered search direction

              See the description of remembered search direction in ed.

       sentence boundary

              A sentence boundary is one of the following:

               1. A paragraph boundary


               2. The first non- <blank> that occurs after a paragraph boundary


               3. The  first  non-  <blank>  that occurs after a period ( '.' ), exclamation mark ( '!' ), or question
                  mark ( '?' ), followed by two <space>s or the end of a line; any number of closing parenthesis ( ')'
                  ),  closing  brackets  (  ']'  ),  double quote ( ' ),' or single quote ( '" ) characters can appear
                  between the punctuation mark and the two <space>s or end-of-line



       In the remainder of the description of the vi utility, the term "buffer line" refers to  a  line  in  the  edit
       buffer and the term "display line" refers to the line or lines on the display screen used to display one buffer
       line. The term "current line" refers to a specific "buffer line".

       If there are display lines on the screen for which there are no corresponding buffer lines because they  corre-
       spond to lines that would be after the end of the file, they shall be displayed as a single tilde ( '~' ) char-
       acter, plus the terminating <newline>.

       The last line of the screen shall be used to report errors or display informational messages. It shall also  be
       used  to display the input for "line-oriented commands" ( /, ?, :, and !). When a line-oriented command is exe-
       cuted, the editor shall enter text input mode on the last line on the  screen,  using  the  respective  command
       characters  as  prompt characters. (In the case of the ! command, the associated motion shall be entered by the
       user before the editor enters text input mode.) The line entered by the user shall be  terminated  by  a  <new-
       line>,  a  non- <control>-V-escaped <carriage-return>, or unescaped <ESC>. It is unspecified if more characters
       than require a display width minus one column number of screen columns can be entered.

       If any command is executed that overwrites a portion of the screen other than the last line of the screen  (for
       example, the ex suspend or ! commands), other than the ex shell command, the user shall be prompted for a char-
       acter before the screen is refreshed and the edit session continued.

       <tab>s shall take up the number of columns on the screen set by the tabstop edit option (see ed), unless  there
       are less than that number of columns before the display margin that will cause the displayed line to be folded;
       in this case, they shall only take up the number of columns up to that boundary.

       The cursor shall be placed on the current line and relative to the current column as specified by each  command
       described in the following sections.

       In open mode, if the current line is not already displayed, then it shall be displayed.

       In  visual  mode,  if  the  current line is not displayed, then the lines that are displayed shall be expanded,
       scrolled, or redrawn to cause an unspecified portion of the current line to be displayed.   If  the  screen  is
       redrawn,  no  more  than  the number of display lines specified by the value of the window edit option shall be
       displayed (unless the current line cannot be completely displayed in the number of display lines  specified  by
       the  window edit option) and the current line shall be positioned as close to the center of the displayed lines
       as possible (within the constraints imposed by the distance of the line from the beginning or end of  the  edit
       buffer). If the current line is before the first line in the display and the screen is scrolled, an unspecified
       portion of the current line shall be placed on the first line of the display. If the current line is after  the
       last line in the display and the screen is scrolled, an unspecified portion of the current line shall be placed
       on the last line of the display.

       In visual mode, if a line from the edit buffer (other than the current line) does not  entirely  fit  into  the
       lines  at  the bottom of the display that are available for its presentation, the editor may choose not to dis-
       play any portion of the line. The lines of the display that do not contain text from the edit buffer  for  this
       reason shall each consist of a single '@' character.

       In  visual mode, the editor may choose for unspecified reasons to not update lines in the display to correspond
       to the underlying edit buffer text. The lines of the display that do not correctly correspond to text from  the
       edit  buffer  for this reason shall consist of a single '@' character (plus the terminating <newline>), and the
       <control>-R command shall cause the editor to update the screen to correctly represent the edit buffer.

       Open and visual mode commands that set the current column set it to a column position in the display, and not a
       character  position  in the line. In this case, however, the column position in the display shall be calculated
       for an infinite width display; for example, the column related to a character that is part of a line  that  has
       been  folded  onto  additional  screen  lines will be offset from the display line column where the buffer line
       begins, not from the beginning of a particular display line.

       The display cursor column in the display is based on the value of the current column,  as  follows,  with  each
       rule applied in turn:

        1. If  the current column is after the last display line column used by the displayed line, the display cursor
           column shall be set to the last display line column occupied by the last  non-  <newline>  in  the  current
           line; otherwise, the display cursor column shall be set to the current column.


        2. If  the  character  of  which some portion is displayed in the display line column specified by the display
           cursor column requires more than a single display line column:

            a. If in text input mode, the display cursor column shall be adjusted to the first display line column  in
               which any portion of that character is displayed.


            b. Otherwise,  the  display  cursor  column shall be adjusted to the last display line column in which any
               portion of that character is displayed.



       The current column shall not be changed by these adjustments to the display cursor column.

       If an error occurs during the parsing or execution of a vi command:

        * The terminal shall be alerted. Execution of the vi command shall stop, and the cursor (for example, the cur-
          rent line and column) shall not be further modified.


        * Unless  otherwise  specified  by  the following command sections, it is unspecified whether an informational
          message shall be displayed.


        * Any partially entered vi command shall be discarded.


        * If the vi command resulted from a map expansion, all characters from that map expansion shall be  discarded,
          except as otherwise specified by the map command (see ed).


        * If  the  vi  command resulted from the execution of a buffer, no further commands caused by the execution of
          the buffer shall be executed.


   Page Backwards
       Synopsis:


              [count] <control>-B


       If in open mode, the <control>-B command shall behave identically to the z command. Otherwise, if  the  current
       line is the first line of the edit buffer, it shall be an error.

       If  the  window  edit  option is less than 3, display a screen where the last line of the display shall be some
       portion of:


              (current first line) -1

       otherwise, display a screen where the first line of the display shall be some portion of:


              (current first line) - count x ((window edit option) -2)

       If this calculation would result in a line that is before the first line of the edit buffer, the first line  of
       the display shall display some portion of the first line of the edit buffer.

       Current  line: If no lines from the previous display remain on the screen, set to the last line of the display;
       otherwise, set to ( line - the number of new lines displayed on this screen).

       Current column: Set to non- <blank>.

   Scroll Forward
       Synopsis:


              [count] <control>-D


       If the current line is the last line of the edit buffer, it shall be an error.

       If no count is specified, count shall default to the count associated with the previous  <control>-D  or  <con-
       trol>-U  command. If there was no previous <control>-D or <control>-U command, count shall default to the value
       of the scroll edit option.

       If in open mode, write lines starting with the line after the current line, until count lines or the last  line
       of the file have been written.

       Current line: If the current line + count is past the last line of the edit buffer, set to the last line of the
       edit buffer; otherwise, set to the current line + count.

       Current column: Set to non- <blank>.

   Scroll Forward by Line
       Synopsis:


              [count] <control>-E


       Display the line count lines after the last line currently displayed.

       If the last line of the edit buffer is displayed, it shall be an error.  If there is no line count lines  after
       the  last line currently displayed, the last line of the display shall display some portion of the last line of
       the edit buffer.

       Current line: Unchanged if the previous current character is displayed; otherwise, set to the first  line  dis-
       played.

       Current column: Unchanged.

   Page Forward
       Synopsis:


              [count] <control>-F


       If  in  open mode, the <control>-F command shall behave identically to the z command. Otherwise, if the current
       line is the last line of the edit buffer, it shall be an error.

       If the window edit option is less than 3, display a screen where the first line of the display  shall  be  some
       portion of:


              (current last line) +1

       otherwise, display a screen where the first line of the display shall be some portion of:


              (current first line) + count x ((window edit option) -2)

       If this calculation would result in a line that is after the last line of the edit buffer, the last line of the
       display shall display some portion of the last line of the edit buffer.

       Current line: If no lines from the previous display remain on the screen, set to the first line of the display;
       otherwise, set to ( line + the number of new lines displayed on this screen).

       Current column: Set to non- <blank>.

   Display Information
       Synopsis:


              <control>-G


       This command shall be equivalent to the ex file command.

   Move Cursor Backwards
       Synopsis:


              [count] <control>-H


              [count] h


              the current erase character (see stty)


       If there are no characters before the current character on the current line, it shall be an error. If there are
       less than count previous characters on the current line, count shall be adjusted  to  the  number  of  previous
       characters on the line.

       If used as a motion command:

        1. The  text  region  shall  be  from the character before the starting cursor up to and including the countth
           character before the starting cursor.


        2. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to ( column - the number of columns occupied by count characters ending with  the  previous
       current column).

   Move Down
       Synopsis:


              [count] <newline>


              [count] <control>-J


              [count] <control>-M


              [count] <control>-N


              [count] j


              [count] <carriage-return>


              [count] +


       If there are less than count lines after the current line in the edit buffer, it shall be an error.

       If used as a motion command:

        1. The text region shall include the starting line and the next count - 1 lines.


        2. Any text copied to a buffer shall be in line mode.


       If not used as a motion command:

       Current line: Set to current line+ count.

       Current  column:  Set  to  non-  <blank>  for  the  <carriage-return>,  <control>-M, and + commands; otherwise,
       unchanged.

   Clear and Redisplay
       Synopsis:


              <control>-L


       If in open mode, clear the screen and redisplay the current line.  Otherwise, clear and redisplay the screen.

       Current line: Unchanged.

       Current column: Unchanged.

   Move Up
       Synopsis:


              [count] <control>-P


              [count] k


              [count] -


       If there are less than count lines before the current line in the edit buffer, it shall be an error.

       If used as a motion command:

        1. The text region shall include the starting line and the previous count lines.


        2. Any text copied to a buffer shall be in line mode.


       If not used as a motion command:

       Current line: Set to current line - count.

       Current column: Set to non- <blank> for the - command; otherwise, unchanged.

   Redraw Screen
       Synopsis:


              <control>-R


       If any lines have been deleted from the display screen and flagged as deleted on the terminal using the @  con-
       vention  (see  the  beginning of the EXTENDED DESCRIPTION section), they shall be redisplayed to match the con-
       tents of the edit buffer.

       It is unspecified whether lines flagged with @ because they do  not  fit  on  the  terminal  display  shall  be
       affected.

       Current line: Unchanged.

       Current column: Unchanged.

   Scroll Backward
       Synopsis:


              [count] <control>-U


       If the current line is the first line of the edit buffer, it shall be an error.

       If  no  count  is specified, count shall default to the count associated with the previous <control>-D or <con-
       trol>-U command. If there was no previous <control>-D or <control>-U command, count shall default to the  value
       of the scroll edit option.

       Current  line: If count is greater than the current line, set to 1; otherwise, set to the current line - count.

       Current column: Set to non- <blank>.

   Scroll Backward by Line
       Synopsis:


              [count] <control>-Y


       Display the line count lines before the first line currently displayed.

       If the current line is the first line of the edit buffer, it shall be  an  error.  If  this  calculation  would
       result  in a line that is before the first line of the edit buffer, the first line of the display shall display
       some portion of the first line of the edit buffer.

       Current line: Unchanged if the previous current character is displayed; otherwise, set to the first  line  dis-
       played.

       Current column: Unchanged.

   Edit the Alternate File
       Synopsis:


              <control>-^

       This command shall be equivalent to the ex edit command, with the alternate pathname as its argument.

   Terminate Command or Input Mode
       Synopsis:


              <ESC>


       If  a partial vi command (as defined by at least one, non- count character) has been entered, discard the count
       and the command character(s).

       Otherwise, if no command characters have been entered, and the <ESC> was the result of  a  map  expansion,  the
       terminal shall be alerted and the <ESC> character shall be discarded, but it shall not be an error.

       Otherwise, it shall be an error.

       Current line: Unchanged.

       Current column: Unchanged.

   Search for tagstring
       Synopsis:


              <control>-]


       If the current character is not a word or <blank>, it shall be an error.

       This command shall be equivalent to the ex tag command, with the argument to that command defined as follows.

       If the current character is a <blank>:

        1. Skip all <blank>s after the cursor up to the end of the line.


        2. If the end of the line is reached, it shall be an error.


       Then,  the  argument  to the ex tag command shall be the current character and all subsequent characters, up to
       the first non-word character or the end of the line.

   Move Cursor Forward
       Synopsis:


              [count] <space>


              [count] l  (ell)


       If there are less than count non- <newline>s after the cursor on the current line, count shall be  adjusted  to
       the number of non- <newline>s after the cursor on the line.

       If used as a motion command:

        1. If  the  current  or  countth  character  after the cursor is the last non- <newline> in the line, the text
           region shall be comprised of the current character up to and including the last non- <newline> in the line.
           Otherwise,  the text region shall be from the current character up to, but not including, the countth char-
           acter after the cursor.


        2. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       If there are no non- <newline>s after the current character on the current line, it shall be an error.

       Current line: Unchanged.

       Current column: Set to the last column that displays any portion of the countth  character  after  the  current
       character.

   Replace Text with Results from Shell Command
       Synopsis:


              [count] ! motion shell-commands <newline>


       If the motion command is the ! command repeated:

        1. If  the edit buffer is empty and no count was supplied, the command shall be the equivalent of the ex :read
           ! command, with the text input, and no text shall be copied to any buffer.


        2. Otherwise:

            a. If there are less than count -1 lines after the current line in the edit buffer, it shall be an  error.


            b. The text region shall be from the current line up to and including the next count -1 lines.



       Otherwise, the text region shall be the lines in which any character of the text region specified by the motion
       command appear.

       Any text copied to a buffer shall be in line mode.

       This command shall be equivalent to the ex ! command for the specified lines.

   Move Cursor to End-of-Line
       Synopsis:


              [count] $


       It shall be an error if there are less than ( count -1) lines after the current line in the edit buffer.

       If used as a motion command:

        1. If count is 1:

            a. It shall be an error if the line is empty.


            b. Otherwise, the text region shall consist of all characters from the starting cursor to  the  last  non-
               <newline> in the line, inclusive, and any text copied to a buffer shall be in character mode.



        2. Otherwise,  if  the  starting  cursor position is at or before the first non- <blank> in the line, the text
           region shall consist of the current and the next count -1 lines, and any text saved to a buffer shall be in
           line mode.


        3. Otherwise,  the text region shall consist of all characters from the starting cursor to the last non- <new-
           line> in the line that is count -1 lines forward from the current line, and any text  copied  to  a  buffer
           shall be in character mode.


       If not used as a motion command:

       Current line: Set to the current line + count-1.

       Current  column:  The  current  column is set to the last display line column of the last non- <newline> in the
       line, or column position 1 if the line is empty.

       The current column shall be adjusted to be on the last display line column of the last non-  <newline>  of  the
       current line as subsequent commands change the current line, until a command changes the current column.

   Move to Matching Character
       Synopsis:


              %


       If  the  character at the current position is not a parenthesis, bracket, or curly brace, search forward in the
       line to the first one of those characters. If no such character is found, it shall be an error.

       The matching character shall be the parenthesis, bracket, or curly brace matching the parenthesis, bracket,  or
       curly brace, respectively, that was at the current position or that was found on the current line.

       Matching shall be determined as follows, for an open parenthesis:

        1. Set a counter to 1.


        2. Search forwards until a parenthesis is found or the end of the edit buffer is reached.


        3. If the end of the edit buffer is reached, it shall be an error.


        4. If an open parenthesis is found, increment the counter by 1.


        5. If a close parenthesis is found, decrement the counter by 1.


        6. If the counter is zero, the current character is the matching character.


       Matching  for  a  close  parenthesis  shall  be equivalent, except that the search shall be backwards, from the
       starting character to the beginning of the buffer, a close parenthesis shall increment the counter by 1, and an
       open parenthesis shall decrement the counter by 1.

       Matching  for  brackets  and curly braces shall be equivalent, except that searching shall be done for open and
       close brackets or open and close curly braces.  It  is  implementation-defined  whether  other  characters  are
       searched for and matched as well.

       If used as a motion command:

        1. If  the  matching cursor was after the starting cursor in the edit buffer, and the starting cursor position
           was at or before the first non- <blank> non- <newline> in the starting line, and the matching cursor  posi-
           tion  was at or after the last non- <blank> non- <newline> in the matching line, the text region shall con-
           sist of the current line to the matching line, inclusive, and any text copied to a buffer shall be in  line
           mode.


        2. If  the matching cursor was before the starting cursor in the edit buffer, and the starting cursor position
           was at or after the last non- <blank> non- <newline> in the starting line, and the matching cursor position
           was  at or before the first non- <blank> non- <newline> in the matching line, the text region shall consist
           of the current line to the matching line, inclusive, and any text copied to a buffer shall be in line mode.


        3. Otherwise,  the  text  region shall consist of the starting character to the matching character, inclusive,
           and any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Set to the line where the matching character is located.

       Current column: Set to the last column where any portion of the matching character is displayed.

   Repeat Substitution
       Synopsis:


              &


       Repeat the previous substitution command. This command shall be equivalent to the ex & command with the current
       line as its addresses, and without options, count, or flags.

   Return to Previous Context at Beginning of Line
       Synopsis:


              ' character


       It shall be an error if there is no line in the edit buffer marked by character.

       If used as a motion command:

        1. If the starting cursor is after the marked cursor, then the locations of the starting cursor and the marked
           cursor in the edit buffer shall be logically swapped.


        2. The text region shall consist of the starting line up to and including the marked line, and any text copied
           to a buffer shall be in line mode.


       If not used as a motion command:

       Current line: Set to the line referenced by the mark.

       Current column: Set to non- <blank>.

   Return to Previous Context
       Synopsis:


              ' character


       It shall be an error if the marked line is no longer in the edit buffer.  If the marked line no longer contains
       a character in the saved numbered character position, it shall be as if the marked position is the  first  non-
       <blank>.

       If used as a motion command:

        1. It  shall be an error if the marked cursor references the same character in the edit buffer as the starting
           cursor.


        2. If the starting cursor is after the marked cursor, then the locations of the starting cursor and the marked
           cursor in the edit buffer shall be logically swapped.


        3. If  the starting line is empty or the starting cursor is at or before the first non- <blank> non- <newline>
           of the starting line, and the marked cursor line is empty or the marked cursor references the first charac-
           ter  of  the  marked cursor line, the text region shall consist of all lines containing characters from the
           starting cursor to the line before the marked cursor line, inclusive, and any text copied to a buffer shall
           be in line mode.


        4. Otherwise,  if the marked cursor line is empty or the marked cursor references a character at or before the
           first non- <blank> non- <newline> of the marked cursor line, the region of text shall be from the  starting
           cursor to the last non- <newline> of the line before the marked cursor line, inclusive, and any text copied
           to a buffer shall be in character mode.


        5. Otherwise, the region of text shall be from the starting cursor (inclusive), to the marked  cursor  (exclu-
           sive), and any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Set to the line referenced by the mark.

       Current  column:  Set  to  the last column in which any portion of the character referenced by the mark is dis-
       played.

   Return to Previous Section
       Synopsis:


              [count] [[


       Move the cursor backward through the edit buffer to the first character of the previous section boundary, count
       times.

       If used as a motion command:

        1. If  the starting cursor was at the first character of the starting line or the starting line was empty, and
           the first character of the boundary was the first character of the boundary line,  the  text  region  shall
           consist  of  the  current line up to and including the line where the countth next boundary starts, and any
           text copied to a buffer shall be in line mode.


        2. If the boundary was the last line of the edit buffer or the last non- <newline> of the  last  line  of  the
           edit buffer, the text region shall consist of the last character in the edit buffer up to and including the
           starting character, and any text saved to a buffer shall be in character mode.


        3. Otherwise, the text region shall consist of the starting character up to but not including the first  char-
           acter in the countth next boundary, and any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Set to the line where the countth next boundary in the edit buffer starts.

       Current column: Set to the last column in which any portion of the first character of the countth next boundary
       is displayed, or column position 1 if the line is empty.

   Move to Next Section
       Synopsis:


              [count] ]]


       Move the cursor forward through the edit buffer to the first character of  the  next  section  boundary,  count
       times.

       If used as a motion command:

        1. If  the starting cursor was at the first character of the starting line or the starting line was empty, and
           the first character of the boundary was the first character of the boundary line,  the  text  region  shall
           consist  of  the  current line up to and including the line where the countth previous boundary starts, and
           any text copied to a buffer shall be in line mode.


        2. If the boundary was the first line of the edit buffer, the text region shall consist of the first character
           in the edit buffer up to but not including the starting character, and any text copied to a buffer shall be
           in character mode.


        3. Otherwise, the text region shall consist of the first character in the countth previous section boundary up
           to but not including the starting character, and any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Set to the line where the countth previous boundary in the edit buffer starts.

       Current  column:  Set  to  the  last column in which any portion of the first character of the countth previous
       boundary is displayed, or column position 1 if the line is empty.

   Move to First Non-<blank> Position on Current Line
       Synopsis:


              ^

       If used as a motion command:

        1. If the line has no non- <blank> non- <newline>s, or if the cursor is at the first non- <blank>  non-  <new-
           line> of the line, it shall be an error.


        2. If  the  cursor  is before the first non- <blank> non- <newline> of the line, the text region shall be com-
           prised of the current character, up to, but not including, the first non- <blank>  non-  <newline>  of  the
           line.


        3. If the cursor is after the first non- <blank> non- <newline> of the line, the text region shall be from the
           character before the starting cursor up to and including the first non- <blank> non- <newline> of the line.


        4. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to non- <blank>.

   Current and Line Above
       Synopsis:


              [count] _


       If there are less than count -1 lines after the current line in the edit buffer, it shall be an error.

       If used as a motion command:

        1. If count is less than 2, the text region shall be the current line.


        2. Otherwise, the text region shall include the starting line and the next count -1 lines.


        3. Any text copied to a buffer shall be in line mode.


       If not used as a motion command:

       Current line: Set to current line + count -1.

       Current column: Set to non- <blank>.

   Move Back to Beginning of Sentence
       Synopsis:


              [count] (


       Move  backward  to  the  beginning  of a sentence. This command shall be equivalent to the [[ command, with the
       exception that sentence boundaries shall be used instead of section boundaries.

   Move Forward to Beginning of Sentence
       Synopsis:


              [count] )


       Move forward to the beginning of a sentence. This command shall be equivalent  to  the  ]]  command,  with  the
       exception that sentence boundaries shall be used instead of section boundaries.

   Move Back to Preceding Paragraph
       Synopsis:


              [count] {


       Move back to the beginning of the preceding paragraph. This command shall be equivalent to the [[ command, with
       the exception that paragraph boundaries shall be used instead of section boundaries.

   Move Forward to Next Paragraph
       Synopsis:


              [count] }


       Move forward to the beginning of the next paragraph. This command shall be equivalent to the ]]  command,  with
       the exception that paragraph boundaries shall be used instead of section boundaries.

   Move to Specific Column Position
       Synopsis:


              [count] |


       For  the  purposes  of  this command, lines that are too long for the current display and that have been folded
       shall be treated as having a single, 1-based, number of columns.

       If there are less than count columns in which characters from the current line are  displayed  on  the  screen,
       count shall be adjusted to be the last column in which any portion of the line is displayed on the screen.

       If used as a motion command:

        1. If  the  line  is  empty, or the cursor character is the same as the character on the countth column of the
           line, it shall be an error.


        2. If the cursor is before the countth column of the line, the text region shall be comprised of  the  current
           character, up to but not including the character on the countth column of the line.


        3. If  the  cursor is after the countth column of the line, the text region shall be from the character before
           the starting cursor up to and including the character on the countth column of the line.


        4. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in which any portion of the character that is  displayed  in  the  count
       column of the line is displayed.

   Reverse Find Character
       Synopsis:


              [count] ,


       If  the last F, f, T, or t command was F, f, T, or t, this command shall be equivalent to an f, F, t, or T com-
       mand, respectively, with the specified count and the same search character.

       If there was no previous F, f, T, or t command, it shall be an error.

   Repeat
       Synopsis:


              [count] .


       Repeat the last !, <, >, A, C, D, I, J, O, P, R, S, X, Y, a, c, d, i, o, p, r, s, x, y, or ~ command. It  shall
       be  an  error if none of these commands have been executed. Commands (other than commands that enter text input
       mode) executed as a result of map expansions, shall not change the value of the last repeatable command.

       Repeated commands with associated motion commands shall repeat the motion command as well; however, any  speci-
       fied  count shall replace the count(s) that were originally specified to the repeated command or its associated
       motion command.

       If the motion component of the repeated command is f, F, t, or T, the repeated command shall not set the remem-
       bered search character for the ; and , commands.

       If  the repeated command is p or P, and the buffer associated with that command was a numeric buffer named with
       a number less than 9, the buffer associated with the repeated command shall be set to be the  buffer  named  by
       the name of the previous buffer logically incremented by 1.

       If the repeated character is a text input command, the input text associated with that command is repeated lit-
       erally:

        * Input characters are neither macro or abbreviation-expanded.


        * Input characters are not interpreted in any special  way  with  the  exception  that  <newline>,  <carriage-
          return>, and <control>-T behave as described in Input Mode Commands in vi .


       Current line: Set as described for the repeated command.

       Current column: Set as described for the repeated command.

   Find Regular Expression
       Synopsis:


              /


       If  the input line contains no non- <newline>s, it shall be equivalent to a line containing only the last regu-
       lar expression encountered. The enhanced regular expressions supported by vi are described in  Regular  Expres-
       sions in ex .

       Otherwise,  the line shall be interpreted as one or more regular expressions, optionally followed by an address
       offset or a vi z command.

       If the regular expression is not the last regular expression on the line, or if a line offset or z  command  is
       specified, the regular expression shall be terminated by an unescaped '/' character, which shall not be used as
       part of the regular expression. If the regular expression is not the first regular expression on the  line,  it
       shall  be  preceded  by zero or more <blank>s, a semicolon, zero or more <blank>s, and a leading '/' character,
       which shall not be interpreted as part of the regular expression. It shall be an error to precede  any  regular
       expression with any characters other than these.

       Each  search shall begin from the character after the first character of the last match (or, if it is the first
       search, after the cursor). If the wrapscan edit option is set, the  search  shall  continue  to  the  character
       before  the  starting  cursor  character; otherwise, to the end of the edit buffer. It shall be an error if any
       search fails to find a match, and an informational message to this effect shall be displayed.

       An optional address offset (see Addressing in ex ) can be  specified  after  the  last  regular  expression  by
       including a trailing '/' character after the regular expression and specifying the address offset.  This offset
       will be from the line containing the match for the last regular expression specified. It shall be an  error  if
       the  line offset would indicate a line address less than 1 or greater than the last line in the edit buffer. An
       address offset of zero shall be supported. It shall be an error to follow the address  offset  with  any  other
       characters than <blank>s.

       If  not  used  as  a motion command, an optional z command (see Redraw Window ) can be specified after the last
       regular expression by including a trailing '/' character after the regular expression, zero or more <blank>s, a
       'z',  zero  or  more  <blank>s, an optional new window edit option value, zero or more <blank>s, and a location
       character. The effect shall be as if the z command was executed after the / command.  It shall be an  error  to
       follow the z command with any other characters than <blank>s.

       The remembered search direction shall be set to forward.

       If used as a motion command:

        1. It  shall  be  an  error if the last match references the same character in the edit buffer as the starting
           cursor.


        2. If any address offset is specified, the last match shall be adjusted by the specified offset  as  described
           previously.


        3. If  the  starting  cursor  is  after the last match, then the locations of the starting cursor and the last
           match in the edit buffer shall be logically swapped.


        4. If any address offset is specified, the text region shall consist of all lines containing  characters  from
           the  starting  cursor  to  the last match line, inclusive, and any text copied to a buffer shall be in line
           mode.


        5. Otherwise, if the starting line is empty or the starting cursor is at or before the first non- <blank> non-
           <newline>  of  the  starting  line,  and the last match line is empty or the last match starts at the first
           character of the last match line, the text region shall consist of all lines containing characters from the
           starting cursor to the line before the last match line, inclusive, and any text copied to a buffer shall be
           in line mode.


        6. Otherwise, if the last match line is empty or the last match begins at a character at or before  the  first
           non-  <blank> non- <newline> of the last match line, the region of text shall be from the current cursor to
           the last non- <newline> of the line before the last match line, inclusive, and any text copied to a  buffer
           shall be in character mode.


        7. Otherwise,  the  region of text shall be from the current cursor (inclusive), to the first character of the
           last match (exclusive), and any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: If a match is found, set to the last matched line plus the address  offset,  if  any;  otherwise,
       unchanged.

       Current  column:  Set to the last column on which any portion of the first character in the last matched string
       is displayed, if a match is found; otherwise, unchanged.

   Move to First Character in Line
       Synopsis:


              0  (zero)


       Move to the first character on the current line. The character '0' shall not be interpreted as a command if  it
       is immediately preceded by a digit.

       If used as a motion command:

        1. If the cursor character is the first character in the line, it shall be an error.


        2. The text region shall be from the character before the cursor character up to and including the first char-
           acter in the line.


        3. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current column: The last column in which any portion of the first character in the line is displayed, or if the
       line is empty, unchanged.

   Execute an ex Command
       Synopsis:


              :


       Execute one or more ex commands.

       If  any  portion of the screen other than the last line of the screen was overwritten by any ex command (except
       shell), vi shall display a message indicating that it is waiting for an input from the  user,  and  shall  then
       read a character. This action may also be taken for other, unspecified reasons.

       If  the next character entered is a ':', another ex command shall be accepted and executed. Any other character
       shall cause the screen to be refreshed and vi shall return to command mode.

       Current line: As specified for the ex command.

       Current column: As specified for the ex command.

   Repeat Find
       Synopsis:


              [count] ;


       This command shall be equivalent to the last F, f, T, or t command, with the specified count, and with the same
       search  character  used  for the last F, f, T, or t command. If there was no previous F, f, T, or t command, it
       shall be an error.

   Shift Left
       Synopsis:


              [count] < motion


       If the motion command is the < command repeated:

        1. If there are less than count -1 lines after the current line in the edit buffer, it shall be an error.


        2. The text region shall be from the current line, up to and including the next count -1 lines.


       Shift any line in the text region specified by the  count  and  motion  command  one  shiftwidth  (see  the  ex
       shiftwidth option) toward the start of the line, as described by the ex < command. The unshifted lines shall be
       copied to the unnamed buffer in line mode.

       Current line: If the motion was from the current cursor position toward the end of the edit buffer,  unchanged.
       Otherwise,  set  to  the  first line in the edit buffer that is part of the text region specified by the motion
       command.

       Current column: Set to non- <blank>.

   Shift Right
       Synopsis:


              [count] > motion


       If the motion command is the > command repeated:

        1. If there are less than count -1 lines after the current line in the edit buffer, it shall be an error.


        2. The text region shall be from the current line, up to and including the next count -1 lines.


       Shift any line with characters in the text region specified by the count and motion command one shiftwidth (see
       the  ex  shiftwidth  option)  away  from the start of the line, as described by the ex > command. The unshifted
       lines shall be copied into the unnamed buffer in line mode.

       Current line: If the motion was from the current cursor position toward the end of the edit buffer,  unchanged.
       Otherwise,  set  to  the  first line in the edit buffer that is part of the text region specified by the motion
       command.

       Current column: Set to non- <blank>.

   Scan Backwards for Regular Expression
       Synopsis:


              ?


       Scan backwards; the ? command shall be equivalent to the / command (see Find Regular Expression ) with the fol-
       lowing exceptions:

        1. The input prompt shall be a '?' .


        2. Each  search  shall begin from the character before the first character of the last match (or, if it is the
           first search, the character before the cursor character).


        3. The search direction shall be from the cursor toward the beginning of the edit  buffer,  and  the  wrapscan
           edit option shall affect whether the search wraps to the end of the edit buffer and continues.


        4. The remembered search direction shall be set to backward.


   Execute
       Synopsis:


              @buffer


       If  the  buffer  is specified as @, the last buffer executed shall be used. If no previous buffer has been exe-
       cuted, it shall be an error.

       Behave as if the contents of the named buffer were entered as standard input. After each line  of  a  line-mode
       buffer, and all but the last line of a character mode buffer, behave as if a <newline> were entered as standard
       input.

       If an error occurs during this process, an error message shall be written, and  no  more  characters  resulting
       from the execution of this command shall be processed.

       If  a  count  is specified, behave as if that count were entered as user input before the characters from the @
       buffer were entered.

       Current line: As specified for the individual commands.

       Current column: As specified for the individual commands.

   Reverse Case
       Synopsis:


              [count] ~


       Reverse the case of the current character and the next count -1 characters, such that lowercase characters that
       have uppercase counterparts shall be changed to uppercase characters, and uppercase characters that have lower-
       case counterparts shall be changed to lowercase characters, as prescribed by  the  current  locale.   No  other
       characters shall be affected by this command.

       If  there are less than count -1 characters after the cursor in the edit buffer, count shall be adjusted to the
       number of characters after the cursor in the edit buffer minus 1.

       For the purposes of this command, the next character after the last non- <newline> on the  line  shall  be  the
       next character in the edit buffer.

       Current line: Set to the line including the ( count-1)th character after the cursor.

       Current  column:  Set to the last column in which any portion of the ( count-1)th character after the cursor is
       displayed.

   Append
       Synopsis:


              [count] a


       Enter text input mode after the current cursor position. No characters already in  the  edit  buffer  shall  be
       affected  by  this command. A count shall cause the input text to be appended count -1 more times to the end of
       the input.

       Current line/column: As specified for the text input commands (see Input Mode Commands in vi ).

   Append at End-of-Line
       Synopsis:


              [count] A


       This command shall be equivalent to the vi command:


              $ [ count ] a

       (see Append ).

   Move Backward to Preceding Word
       Synopsis:


              [count] b


       With the exception that words are used as the delimiter instead of bigwords, this command shall  be  equivalent
       to the B command.

   Move Backward to Preceding Bigword
       Synopsis:


              [count] B


       If  the  edit buffer is empty or the cursor is on the first character of the edit buffer, it shall be an error.
       If less than count bigwords begin between the cursor and the start of the edit buffer, count shall be  adjusted
       to the number of bigword beginnings between the cursor and the start of the edit buffer.

       If used as a motion command:

        1. The  text  region shall be from the first character of the countth previous bigword beginning up to but not
           including the cursor character.


        2. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Set to the line containing the current column.

       Current column: Set to the last column upon which any part of the first character of the countth previous  big-
       word is displayed.

   Change
       Synopsis:


              [buffer][count] c motion


       If the motion command is the c command repeated:

        1. The buffer text shall be in line mode.


        2. If there are less than count -1 lines after the current line in the edit buffer, it shall be an error.


        3. The text region shall be from the current line up to and including the next count -1 lines.


       Otherwise, the buffer text mode and text region shall be as specified by the motion command.

       The  replaced  text  shall  be copied into buffer, if specified, and into the unnamed buffer. If the text to be
       replaced contains characters from more than a single line, or the buffer text is in  line  mode,  the  replaced
       text shall be copied into the numeric buffers as well.

       If the buffer text is in line mode:

        1. Any  lines  that  contain  characters in the region shall be deleted, and the editor shall enter text input
           mode at the beginning of a new line which shall replace the first line deleted.


        2. If the autoindent edit option is set, autoindent characters equal to the autoindent characters on the first
           line deleted shall be inserted as if entered by the user.


       Otherwise, if characters from more than one line are in the region of text:

        1. The text shall be deleted.


        2. Any  text  remaining in the last line in the text region shall be appended to the first line in the region,
           and the last line in the region shall be deleted.


        3. The editor shall enter text input mode after the last character not deleted from the first line in the text
           region, if any; otherwise, on the first column of the first line in the region.


       Otherwise:

        1. If the glyph for '$' is smaller than the region, the end of the region shall be marked with a '$' .


        2. The editor shall enter text input mode, overwriting the region of text.


       Current line/column: As specified for the text input commands (see Input Mode Commands in vi ).

   Change to End-of-Line
       Synopsis:


              [buffer][count] C


       This command shall be equivalent to the vi command:


              [buffer][count] c$

       See the c command.

   Delete
       Synopsis:


              [buffer][count] d motion


       If the motion command is the d command repeated:

        1. The buffer text shall be in line mode.


        2. If there are less than count -1 lines after the current line in the edit buffer, it shall be an error.


        3. The text region shall be from the current line up to and including the next count -1 lines.


       Otherwise, the buffer text mode and text region shall be as specified by the motion command.

       If  in  open mode, and the current line is deleted, and the line remains on the display, an '@' character shall
       be displayed as the first glyph of that line.

       Delete the region of text into buffer, if specified, and into the unnamed buffer. If the  text  to  be  deleted
       contains characters from more than a single line, or the buffer text is in line mode, the deleted text shall be
       copied into the numeric buffers, as well.

       Current line: Set to the first text region line that appears in the edit buffer,  unless  that  line  has  been
       deleted,  in  which  case  it shall be set to the last line in the edit buffer, or line 1 if the edit buffer is
       empty.

       Current column:

        1. If the line is empty, set to column position 1.


        2. Otherwise, if the buffer text is in line mode or the motion was from the cursor toward the end of the  edit
           buffer:

            a. If  a  character  from the current line is displayed in the current column, set to the last column that
               displays any portion of that character.


            b. Otherwise, set to the last column in which any portion of any character in the line is displayed.



        3. Otherwise, if a character is displayed in the column that began the text region, set  to  the  last  column
           that displays any portion of that character.


        4. Otherwise, set to the last column in which any portion of any character in the line is displayed.


   Delete to End-of-Line
       Synopsis:


              [buffer] D


       Delete the text from the current position to the end of the current line; equivalent to the vi command:


              [buffer] d$

   Move to End-of-Word
       Synopsis:


              [count] e


       With  the  exception that words are used instead of bigwords as the delimiter, this command shall be equivalent
       to the E command.

   Move to End-of-Bigword
       Synopsis:


              [count] E


       If the edit buffer is empty it shall be an error. If less than count bigwords end between the  cursor  and  the
       end of the edit buffer, count shall be adjusted to the number of bigword endings between the cursor and the end
       of the edit buffer.

       If used as a motion command:

        1. The text region shall be from the last character of the countth next bigword up to and including the cursor
           character.


        2. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Set to the line containing the current column.

       Current column: Set to the last column upon which any part of the last character of the countth next bigword is
       displayed.

   Find Character in Current Line (Forward)
       Synopsis:


              [count] f character


       It shall be an error if count occurrences of the character do not occur after the cursor in the line.

       If used as a motion command:

        1. The text range shall be from the cursor character up to and including the countth occurrence of the  speci-
           fied character after the cursor.


        2. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current  column: Set to the last column in which any portion of the countth occurrence of the specified charac-
       ter after the cursor appears in the line.

   Find Character in Current Line (Reverse)
       Synopsis:


              [count] F character


       It shall be an error if count occurrences of the character do not occur before the cursor in the line.

       If used as a motion command:

        1. The text region shall be from the countth occurrence of the specified character before the cursor,  up  to,
           but not including the cursor character.


        2. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current  column: Set to the last column in which any portion of the countth occurrence of the specified charac-
       ter before the cursor appears in the line.

   Move to Line
       Synopsis:


              [count] G


       If count is not specified, it shall default to the last line of the edit buffer. If count is greater  than  the
       last line of the edit buffer, it shall be an error.

       If used as a motion command:

        1. The text region shall be from the cursor line up to and including the specified line.


        2. Any text copied to a buffer shall be in line mode.


       If not used as a motion command:

       Current line: Set to count if count is specified; otherwise, the last line.

       Current column: Set to non- <blank>.

   Move to Top of Screen
       Synopsis:


              [count] H


       If the beginning of the line count greater than the first line of which any portion appears on the display does
       not exist, it shall be an error.

       If used as a motion command:

        1. If in open mode, the text region shall be the current line.


        2. Otherwise, the text region shall be from the starting line up to and including (the first line of the  dis-
           play + count -1).


        3. Any text copied to a buffer shall be in line mode.


       If not used as a motion command:

       If in open mode, this command shall set the current column to non- <blank> and do nothing else.

       Otherwise, it shall set the current line and current column as follows.

       Current line: Set to (the first line of the display + count -1).

       Current column: Set to non- <blank>.

   Insert Before Cursor
       Synopsis:


              [count] i


       Enter  text  input  mode  before the current cursor position. No characters already in the edit buffer shall be
       affected by this command. A count shall cause the input text to be appended count -1 more times to the  end  of
       the input.

       Current line/column: As specified for the text input commands (see Input Mode Commands in vi ).

   Insert at Beginning of Line
       Synopsis:


              [count] I


       This command shall be equivalent to the vi command ^[ count] i.

   Join
       Synopsis:


              [count] J


       If the current line is the last line in the edit buffer, it shall be an error.

       This  command  shall be equivalent to the ex join command with no addresses, and an ex command count value of 1
       if count was not specified or if a count of 1 was specified, and an ex command count value of count -1 for  any
       other value of count, except that the current line and column shall be set as follows.

       Current line: Unchanged.

       Current  column: The last column in which any portion of the character following the last character in the ini-
       tial line is displayed, or the last non- <newline> in the line if no characters were appended.

   Move to Bottom of Screen
       Synopsis:


              [count] L


       If the beginning of the line count less than the last line of which any portion appears on the display does not
       exist, it shall be an error.

       If used as a motion command:

        1. If in open mode, the text region shall be the current line.


        2. Otherwise,  the  text region shall include all lines from the starting cursor line to (the last line of the
           display -( count -1)).


        3. Any text copied to a buffer shall be in line mode.


       If not used as a motion command:

        1. If in open mode, this command shall set the current column to non- <blank> and do nothing else.


        2. Otherwise, it shall set the current line and current column as follows.


       Current line: Set to (the last line of the display -( count -1)).

       Current column: Set to non- <blank>.

   Mark Position
       Synopsis:


              m letter


       This command shall be equivalent to the ex mark command with the specified character as an argument.

   Move to Middle of Screen
       Synopsis:


              M


       The middle line of the display shall be calculated as follows:


              (the top line of the display) + (((number of lines displayed) +1) /2) -1

       If used as a motion command:

        1. If in open mode, the text region shall be the current line.


        2. Otherwise, the text region shall include all lines from the starting cursor line up to  and  including  the
           middle line of the display.


        3. Any text copied to a buffer shall be in line mode.


       If not used as a motion command:

       If in open mode, this command shall set the current column to non- <blank> and do nothing else.

       Otherwise, it shall set the current line and current column as follows.

       Current line: Set to the middle line of the display.

       Current column: Set to non- <blank>.

   Repeat Regular Expression Find (Forward)
       Synopsis:


              n


       If  the  remembered search direction was forward, the n command shall be equivalent to the vi / command with no
       characters entered by the user. Otherwise, it shall be equivalent to  the  vi  ?  command  with  no  characters
       entered by the user.

       If  the n command is used as a motion command for the !  command, the editor shall not enter text input mode on
       the last line on the screen, and shall behave as if the user entered a single '!' character as the text  input.

   Repeat Regular Expression Find (Reverse)
       Synopsis:


              N


       Scan  for the next match of the last pattern given to / or ?, but in the reverse direction; this is the reverse
       of n.

       If the remembered search direction was forward, the N command shall be equivalent to the vi ? command  with  no
       characters  entered  by  the  user.  Otherwise,  it  shall be equivalent to the vi / command with no characters
       entered by the user. If the N command is used as a motion command for the ! command, the editor shall not enter
       text input mode on the last line on the screen, and shall behave as if the user entered a single ! character as
       the text input.

   Insert Empty Line Below
       Synopsis:


              o


       Enter text input mode in a new line appended after the current line.  A count shall cause the input text to  be
       appended  count -1 more times to the end of the already added text, each time starting on a new, appended line.

       Current line/column: As specified for the text input commands (see Input Mode Commands in vi ).

   Insert Empty Line Above
       Synopsis:


              O


       Enter text input mode in a new line inserted before the current line.  A count shall cause the input text to be
       appended  count -1 more times to the end of the already added text, each time starting on a new, appended line.

       Current line/column: As specified for the text input commands (see Input Mode Commands in vi ).

   Put from Buffer Following
       Synopsis:


              [buffer] p


       If no buffer is specified, the unnamed buffer shall be used.

       If the buffer text is in line mode, the text shall be appended below the current line, and  each  line  of  the
       buffer  shall become a new line in the edit buffer. A count shall cause the buffer text to be appended count -1
       more times to the end of the already added text, each time starting on a new, appended line.

       If the buffer text is in character mode, the text shall be appended into the current line after the cursor, and
       each line of the buffer other than the first and last shall become a new line in the edit buffer. A count shall
       cause the buffer text to be appended count -1 more times to the end of the already added text, each time start-
       ing after the last added character.

       Current line: If the buffer text is in line mode, set the line to line +1; otherwise, unchanged.

       Current column: If the buffer text is in line mode:

        1. If  there is a non- <blank> in the first line of the buffer, set to the last column on which any portion of
           the first non- <blank> in the line is displayed.


        2. If there is no non- <blank> in the first line of the buffer, set to the last column on which any portion of
           the last non- <newline> in the first line of the buffer is displayed.


       If the buffer text is in character mode:

        1. If the text in the buffer is from more than a single line, then set to the last column on which any portion
           of the first character from the buffer is displayed.


        2. Otherwise, if the buffer is the unnamed buffer, set to the last column on which any  portion  of  the  last
           character from the buffer is displayed.


        3. Otherwise,  set  to  the  first  column on which any portion of the first character from the buffer is dis-
           played.


   Put from Buffer Before
       Synopsis:


              [buffer] P


       If no buffer is specified, the unnamed buffer shall be used.

       If the buffer text is in line mode, the text shall be inserted above the current line, and  each  line  of  the
       buffer  shall become a new line in the edit buffer. A count shall cause the buffer text to be appended count -1
       more times to the end of the already added text, each time starting on a new, appended line.

       If the buffer text is in character mode, the text shall be inserted into the current line  before  the  cursor,
       and  each  line of the buffer other than the first and last shall become a new line in the edit buffer. A count
       shall cause the buffer text to be appended count -1 more times to the end of the already added text, each  time
       starting after the last added character.

       Current line: Unchanged.

       Current column: If the buffer text is in line mode:

        1. If  there is a non- <blank> in the first line of the buffer, set to the last column on which any portion of
           that character is displayed.


        2. If there is no non- <blank> in the first line of the buffer, set to the last column on which any portion of
           the last non- <newline> in the first line of the buffer is displayed.


       If the buffer text is in character mode:

        1. If the buffer is the unnamed buffer, set to the last column on which any portion of the last character from
           the buffer is displayed.


        2. Otherwise, set to the first column on which any portion of the first character  from  the  buffer  is  dis-
           played.


   Enter ex Mode
       Synopsis:


              Q


       Leave visual or open mode and enter ex command mode.

       Current line: Unchanged.

       Current column: Unchanged.

   Replace Character
       Synopsis:


              [count] r character


       Replace the count characters at and after the cursor with the specified character. If there are less than count
       non- <newline>s at and after the cursor on the line, it shall be an error.

       If character is <control>-V, any next character other than the <newline> shall be stripped of any special mean-
       ing and used as a literal character.

       If character is <ESC>, no replacement shall be made and the current line and current column shall be unchanged.

       If character is <carriage-return> or <newline>, count new lines shall be appended to the current line. All  but
       the  last  of  these lines shall be empty. count characters at and after the cursor shall be discarded, and any
       remaining characters after the cursor in the current line shall be moved to the last of the new lines.  If  the
       autoindent  edit option is set, they shall be preceded by the same number of autoindent characters found on the
       line from which the command was executed.

       Current line: Unchanged unless the replacement character is a <carriage-return> or <newline>, in which case  it
       shall be set to line + count.

       Current column: Set to the last column position on which a portion of the last replaced character is displayed,
       or if the replacement character caused new lines to be created, set to non- <blank>.

   Replace Characters
       Synopsis:


              R


       Enter text input mode at the current cursor position possibly replacing text on the current line. A count shall
       cause the input text to be appended count -1 more times to the end of the input.

       Current line/column: As specified for the text input commands (see Input Mode Commands in vi ).

   Substitute Character
       Synopsis:


              [buffer][count] s


       This command shall be equivalent to the vi command:


              [buffer][count] c<space>

   Substitute Lines
       Synopsis:


              [buffer][count] S


       This command shall be equivalent to the vi command:


              [buffer][count] c_

   Move Cursor to Before Character (Forward)
       Synopsis:


              [count] t character


       It shall be an error if count occurrences of the character do not occur after the cursor in the line.

       If used as a motion command:

        1. The  text  region  shall be from the cursor up to but not including the countth occurrence of the specified
           character after the cursor.


        2. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in which any portion of the character before the countth  occurrence  of
       the specified character after the cursor appears in the line.

   Move Cursor to After Character (Reverse)
       Synopsis:


              [count] T character


       It shall be an error if count occurrences of the character do not occur before the cursor in the line.

       If used as a motion command:

        1. If the character before the cursor is the specified character, it shall be an error.


        2. The  text  region  shall be from the character before the cursor up to but not including the countth occur-
           rence of the specified character before the cursor.


        3. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in which any portion of the character after the  countth  occurrence  of
       the specified character before the cursor appears in the line.

   Undo
       Synopsis:


              u


       This  command  shall be equivalent to the ex undo command except that the current line and current column shall
       be set as follows:

       Current line: Set to the first line added or changed if any; otherwise, move to the line preceding any  deleted
       text if one exists; otherwise, move to line 1.

       Current column: If undoing an ex command, set to the first non- <blank>.

       Otherwise, if undoing a text input command:

        1. If  the  command was a C, c, O, o, R, S, or s command, the current column shall be set to the value it held
           when the text input command was entered.


        2. Otherwise, set to the last column in which any portion of the first character after  the  deleted  text  is
           displayed,  or,  if  no  non-  <newline>s follow the text deleted from this line, set to the last column in
           which any portion of the last non- <newline> in the line is displayed, or 1 if the line is empty.


       Otherwise, if a single line was modified (that is, not added or deleted) by the u command:

        1. If text was added or changed, set to the last column in which any portion of the first character  added  or
           changed is displayed.


        2. If  text  was deleted, set to the last column in which any portion of the first character after the deleted
           text is displayed, or, if no non- <newline>s follow the deleted text, set to the last column in  which  any
           portion of the last non- <newline> in the line is displayed, or 1 if the line is empty.


       Otherwise, set to non- <blank>.

   Undo Current Line
       Synopsis:


              U


       Restore  the current line to its state immediately before the most recent time that it became the current line.

       Current line: Unchanged.

       Current column: Set to the first column in the line in which any portion of the first character in the line  is
       displayed.

   Move to Beginning of Word
       Synopsis:


              [count] w


       With  the  exception that words are used as the delimiter instead of bigwords, this command shall be equivalent
       to the W command.

   Move to Beginning of Bigword
       Synopsis:


              [count] W


       If the edit buffer is empty, it shall be an error. If there are less than count bigwords between the cursor and
       the  end of the edit buffer, count shall be adjusted to move the cursor to the last bigword in the edit buffer.

       If used as a motion command:

        1. If the associated command is c, count is 1, and the cursor is on a <blank>, the region of text shall be the
           current character and no further action shall be taken.


        2. If  there  are less than count bigwords between the cursor and the end of the edit buffer, then the command
           shall succeed, and the region of text shall include the last character of the edit buffer.


        3. If there are <blank>s or an end-of-line that precede the countth bigword, and the associated command is  c,
           the region of text shall be up to and including the last character before the preceding <blank>s or end-of-
           line.


        4. If there are <blank>s or an end-of-line that precede the bigword, and the associated command is d or y, the
           region  of  text  shall  be up to and including the last <blank> before the start of the bigword or end-of-
           line.


        5. Any text copied to a buffer shall be in character mode.


       If not used as a motion command:

        1. If the cursor is on the last character of the edit buffer, it shall be an error.


       Current line: Set to the line containing the current column.

       Current column: Set to the last column in which any part of the first character of the countth next bigword  is
       displayed.

   Delete Character at Cursor
       Synopsis:


              [buffer][count] x


       Delete  the count characters at and after the current character into buffer, if specified, and into the unnamed
       buffer.

       If the line is empty, it shall be an error. If there are less than count non- <newline>s at and after the  cur-
       sor on the current line, count shall be adjusted to the number of non- <newline>s at and after the cursor.

       Current line: Unchanged.

       Current  column:  If  the  line is empty, set to column position 1. Otherwise, if there were count or less non-
       <newline>s at and after the cursor on the current line, set to the last column that displays any  part  of  the
       last non- <newline> of the line. Otherwise, unchanged.

   Delete Character Before Cursor
       Synopsis:


              [buffer][count] X


       Delete  the  count  characters  before  the  current  character into buffer, if specified, and into the unnamed
       buffer.

       If there are no characters before the current character on the current line, it shall be an error. If there are
       less  than  count  previous  characters  on the current line, count shall be adjusted to the number of previous
       characters on the line.

       Current line: Unchanged.

       Current column: Set to (current column - the width of the deleted characters).

   Yank
       Synopsis:


              [buffer][count] y motion


       Copy (yank) the region of text into buffer, if specified, and into the unnamed buffer.

       If the motion command is the y command repeated:

        1. The buffer shall be in line mode.


        2. If there are less than count -1 lines after the current line in the edit buffer, it shall be an error.


        3. The text region shall be from the current line up to and including the next count -1 lines.


       Otherwise, the buffer text mode and text region shall be as specified by the motion command.

       Current line: If the motion was from the current cursor position toward the end of the edit buffer,  unchanged.
       Otherwise,  set  to  the  first line in the edit buffer that is part of the text region specified by the motion
       command.

       Current column:

        1. If the motion was from the current cursor position toward the end of the edit buffer, unchanged.


        2. Otherwise, if the current line is empty, set to column position 1.


        3. Otherwise, set to the last column that displays any part of the first character in the file that is part of
           the text region specified by the motion command.


   Yank Current Line
       Synopsis:


              [buffer][count] Y


       This command shall be equivalent to the vi command:


              [buffer][count] y_

   Redraw Window
       If in open mode, the z command shall have the Synopsis:

       Synopsis:


              [count] z


       If  count is not specified, it shall default to the window edit option -1. The z command shall be equivalent to
       the ex z command, with a type character of = and a count of count -2, except that the current line and  current
       column  shall  be  set as follows, and the window edit option shall not be affected. If the calculation for the
       count argument would result in a negative number, the count argument to the ex z command shall be zero. A blank
       line shall be written after the last line is written.

       Current line: Unchanged.

       Current column: Unchanged.

       If not in open mode, the z command shall have the following Synopsis:

       Synopsis:


              [line] z [count] character


       If  line is not specified, it shall default to the current line.  If line is specified, but is greater than the
       number of lines in the edit buffer, it shall default to the number of lines in the edit buffer.

       If count is specified, the value of the window edit option shall be set to count (as described in the ex window
       command), and the screen shall be redrawn.

       line shall be placed as specified by the following characters:

       <newline>, <carriage-return>

              Place the beginning of the line on the first line of the display.

       .      Place  the  beginning  of the line in the center of the display. The middle line of the display shall be
              calculated as described for the M command.

       -      Place an unspecified portion of the line on the last line of the display.

       +      If line was specified, equivalent to the <newline> case. If line was not  specified,  display  a  screen
              where  the  first  line  of the display shall be (current last line) +1. If there are no lines after the
              last line in the display, it shall be an error.

       ^      If line was specified, display a screen where the last line of the display shall contain an  unspecified
              portion of the first line of a display that had an unspecified portion of the specified line on the last
              line of the display. If this calculation results in a line before the beginning of the edit buffer, dis-
              play the first screen of the edit buffer.

       Otherwise, display a screen where the last line of the display shall contain an unspecified portion of (current
       first line -1).  If this calculation results in a line before the beginning of the edit buffer, it shall be  an
       error.


       Current line: If line and the '^' character were specified:

        1. If  the first screen was displayed as a result of the command attempting to display lines before the begin-
           ning of the edit buffer: if the first screen was already displayed, unchanged; otherwise, set  to  (current
           first line -1).


        2. Otherwise, set to the last line of the display.


       If line and the '+' character were specified, set to the first line of the display.

       Otherwise, if line was specified, set to line.

       Otherwise, unchanged.

       Current column: Set to non- <blank>.

   Exit
       Synopsis:


              ZZ


       This  command  shall be equivalent to the ex xit command with no addresses, trailing !, or filename (see the ex
       xit command).

   Input Mode Commands in vi
       In text input mode, the current line shall consist of zero or more of the following categories, plus the termi-
       nating <newline>:

        1. Characters preceding the text input entry point

       Characters in this category shall not be modified during text input mode.


        2. autoindent characters

       autoindent characters shall be automatically inserted into each line that is created in text input mode, either
       as a result of entering a <newline> or <carriage-return> while in text input mode, or as an effect of the  com-
       mand itself; for example, O or o (see the ex autoindent command), as if entered by the user.

       It  shall  be  possible  to erase autoindent characters with the <control>-D command; it is unspecified whether
       they can be erased by <control>-H, <control>-U, and <control>-W characters.  Erasing any  autoindent  character
       turns the glyph into erase-columns and deletes the character from the edit buffer, but does not change its rep-
       resentation on the screen.


        3. Text input characters

       Text input characters are the characters entered by the user. Erasing any text input character turns the  glyph
       into  erase-columns  and  deletes the character from the edit buffer, but does not change its representation on
       the screen.

       Each text input character entered by the user (that does not have a special meaning) shall be treated  as  fol-
       lows:

               a. The  text input character shall be appended to the last character in the edit buffer from the first,
                  second, or third categories.


               b. If there are no erase-columns on the screen, the text input command was the R command,  and  charac-
                  ters  in  the fifth category from the original line follow the cursor, the next such character shall
                  be deleted from the edit buffer. If the slowopen edit option is not set, the corresponding glyph  on
                  the screen shall become erase-columns.


               c. If there are erase-columns on the screen, as many columns as they occupy, or as are necessary, shall
                  be overwritten to display the text input character. (If only part of a multi-column glyph  is  over-
                  written,  the remainder shall be left on the screen, and continue to be treated as erase-columns; it
                  is unspecified whether the remainder of the glyph is modified in any way.)


               d. If additional display line columns are needed to display the text input character:

                   1. If the slowopen edit option is set, the text input characters shall be displayed  on  subsequent
                      display line columns, overwriting any characters displayed in those columns.


                   2. Otherwise,  any  characters currently displayed on or after the column on the display line where
                      the text input character is to be displayed shall be pushed ahead the  number  of  display  line
                      columns necessary to display the rest of the text input character.




        4. Erase-columns

       Erase-columns  are  not logically part of the edit buffer, appearing only on the screen, and may be overwritten
       on the screen by subsequent text input characters. When text input mode ends, all erase-columns shall no longer
       appear on the screen.

       Erase-columns  are  initially  the  region  of  text specified by the c command (see Change ); however, erasing
       autoindent or text input characters causes the glyphs of the erased characters to be treated as  erase-columns.


        5. Characters  following  the  text region for the c command, or the text input entry point for all other com-
           mands

       Characters in this category shall not be modified during text input mode, except as specified in category  3.b.
       for the R text input command, or as <blank>s deleted when a <newline> or <carriage-return> is entered.


       It  is  unspecified whether it is an error to attempt to erase past the beginning of a line that was created by
       the entry of a <newline> or <carriage-return> during text input mode. If it is not an error, the  editor  shall
       behave  as  if the erasing character was entered immediately after the last text input character entered on the
       previous line, and all of the non- <newline>s on the current line shall be treated as erase-columns.

       When text input mode is entered, or after a text input mode character is entered (except as specified  for  the
       special characters below), the cursor shall be positioned as follows:

        1. On the first column that displays any part of the first erase-column, if one exists


        2. Otherwise, if the slowopen edit option is set, on the first display line column after the last character in
           the first, second, or third categories, if one exists


        3. Otherwise, the first column that displays any part of the first character in the  fifth  category,  if  one
           exists


        4. Otherwise,  the  display line column after the last character in the first, second, or third categories, if
           one exists


        5. Otherwise, on column position 1


       The characters that are updated on the screen during text input mode are unspecified, other than that the  last
       text  input  character shall always be updated, and, if the slowopen edit option is not set, the current cursor
       character shall always be updated.

       The following specifications are for command characters entered during text input mode.

   NUL
       Synopsis:


              NUL


       If the first character of the text input is a NUL, the most recently input text shall be input as if entered by
       the  user, and then text input mode shall be exited. The text shall be input literally; that is, characters are
       neither macro or abbreviation expanded, nor are any characters  interpreted  in  any  special  manner.   It  is
       unspecified whether implementations shall support more than 256 bytes of remembered input text.

   <control>-D
       Synopsis:


              <control>-D


       The  <control>-D  character  shall  have no special meaning when in text input mode for a line-oriented command
       (see Command Descriptions in vi ).

       This command need not be supported on block-mode terminals.

       If the cursor does not follow an autoindent character, or an autoindent character and a '0' or '^' character:

        1. If the cursor is in column position 1, the <control>-D character shall be discarded and no  further  action
           taken.


        2. Otherwise, the <control>-D character shall have no special meaning.


       If the last input character was a '0', the cursor shall be moved to column position 1.

       Otherwise,  if the last input character was a '^', the cursor shall be moved to column position 1. In addition,
       the autoindent level for the next input line shall be derived from the same  line  from  which  the  autoindent
       level for the current input line was derived.

       Otherwise,  the  cursor  shall be moved back to the column after the previous shiftwidth (see the ex shiftwidth
       command) boundary.

       All of the glyphs on columns between the starting cursor position and (inclusively) the ending cursor  position
       shall become erase-columns as described in Input Mode Commands in vi .

       Current line: Unchanged.

       Current  column:  Set  to  1  if  the  <control>-D was preceded by a '^' or '0' ; otherwise, set to (column -1)
       -((column -2) % shiftwidth).

   <control>-H
       Synopsis:


              <control>-H


       If in text input mode for a line-oriented command, and there are no characters to erase, text input mode  shall
       be  terminated,  no  further  action  shall  be done for this command, and the current line and column shall be
       unchanged.

       If there are characters other than autoindent characters that have been input on the current  line  before  the
       cursor, the cursor shall move back one character.

       Otherwise,  if  there  are  autoindent  characters on the current line before the cursor, it is implementation-
       defined whether the <control>-H command is an error or if the cursor moves back one autoindent character.

       Otherwise, if the cursor is in column position 1 and there are previous lines  that  have  been  input,  it  is
       implementation-defined  whether  the  <control>-H  command is an error or if it is equivalent to entering <con-
       trol>-H after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All of the glyphs on columns between the starting cursor position and (inclusively) the ending cursor  position
       shall become erase-columns as described in Input Mode Commands in vi .

       The  current erase character (see stty) shall cause an equivalent action to the <control>-H command, unless the
       previously inserted character was a backslash, in which case it shall be as if the literal current erase  char-
       acter had been inserted instead of the backslash.

       Current line: Unchanged, unless previously input lines are erased, in which case it shall be set to line -1.

       Current column: Set to the first column that displays any portion of the character backed up over.

   <newline>
       Synopsis:


              <newline>


              <carriage-return>


              <control>-J


              <control>-M


       If  input  was  part of a line-oriented command, text input mode shall be terminated and the command shall con-
       tinue execution with the input provided.

       Otherwise, terminate the current line. If there are no characters other than autoindent characters on the line,
       all  characters  on the line shall be discarded. Otherwise, it is unspecified whether the autoindent characters
       in the line are modified by entering these characters.

       Continue text input mode on a new line appended after the current line. If the slowopen edit option is set, the
       lines on the screen below the current line shall not be pushed down, but the first of them shall be cleared and
       shall appear to be overwritten. Otherwise, the lines of the screen below the current line shall be pushed down.

       If the autoindent edit option is set, an appropriate number of autoindent characters shall be added as a prefix
       to the line as described by the ex autoindent edit option.

       All columns after the cursor that are erase-columns (as described in Input Mode Commands in vi ) shall be  dis-
       carded.

       If the autoindent edit option is set, all <blank>s immediately following the cursor shall be discarded.

       All remaining characters after the cursor shall be transferred to the new line, positioned after any autoindent
       characters.

       Current line: Set to current line +1.

       Current column: Set to the first column that displays any portion of the first character after  the  autoindent
       characters  on  the new line, if any, or the first column position after the last autoindent character, if any,
       or column position 1.

   <control>-T
       Synopsis:


              <control>-T


       The <control>-T character shall have no special meaning when in text input mode  for  a  line-oriented  command
       (see Command Descriptions in vi ).

       This command need not be supported on block-mode terminals.

       Behave as if the user entered the minimum number of <blank>s necessary to move the cursor forward to the column
       position after the next shiftwidth (see the ex shiftwidth command) boundary.

       Current line: Unchanged.

       Current column: Set to column + shiftwidth - ((column -1) % shiftwidth).

   <control>-U
       Synopsis:


              <control>-U


       If there are characters other than autoindent characters that have been input on the current  line  before  the
       cursor, the cursor shall move to the first character input after the autoindent characters.

       Otherwise,  if  there  are  autoindent  characters on the current line before the cursor, it is implementation-
       defined whether the <control>-U command is an error or if the cursor moves to the first column position on  the
       line.

       Otherwise,  if  the  cursor  is  in  column position 1 and there are previous lines that have been input, it is
       implementation-defined whether the <control>-U command is an error or if it is  equivalent  to  entering  <con-
       trol>-U after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All  of the glyphs on columns between the starting cursor position and (inclusively) the ending cursor position
       shall become erase-columns as described in Input Mode Commands in vi .

       The current kill character (see stty) shall cause an equivalent action to the <control>-U command,  unless  the
       previously inserted character was a backslash, in which case it shall be as if the literal current kill charac-
       ter had been inserted instead of the backslash.

       Current line: Unchanged, unless previously input lines are erased, in which case it shall be set to line -1.

       Current column: Set to the first column that displays any portion of the last character backed up over.

   <control>-V
       Synopsis:


              <control>-V


              <control>-Q


       Allow the entry of any subsequent character, other than <control>-J or the <newline>, as a  literal  character,
       removing any special meaning that it may have to the editor in text input mode. If a <control>-V or <control>-Q
       is entered before a <control>-J or <newline>, the <control>-V or <control>-Q character shall be discarded,  and
       the <control>-J or <newline> shall behave as described in the <newline> command character during input mode.

       For  purposes  of  the  display only, the editor shall behave as if a '^' character was entered, and the cursor
       shall be positioned as if overwriting the '^' character. When a subsequent character  is  entered,  the  editor
       shall behave as if that character was entered instead of the original <control>-V or <control>-Q character.

       Current line: Unchanged.

       Current column: Unchanged.

   <control>-W
       Synopsis:


              <control>-W


       If  there  are  characters other than autoindent characters that have been input on the current line before the
       cursor, the cursor shall move back over the last word preceding the cursor (including any <blank>s between  the
       end of the last word and the current cursor); the cursor shall not move to before the first character after the
       end of any autoindent characters.

       Otherwise, if there are autoindent characters on the current line before  the  cursor,  it  is  implementation-
       defined  whether the <control>-W command is an error or if the cursor moves to the first column position on the
       line.

       Otherwise, if the cursor is in column position 1 and there are previous lines  that  have  been  input,  it  is
       implementation-defined  whether  the  <control>-W  command is an error or if it is equivalent to entering <con-
       trol>-W after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All of the glyphs on columns between the starting cursor position and (inclusively) the ending cursor  position
       shall become erase-columns as described in Input Mode Commands in vi .

       Current line: Unchanged, unless previously input lines are erased, in which case it shall be set to line -1.

       Current column: Set to the first column that displays any portion of the last character backed up over.

   <ESC>
       Synopsis:


              <ESC>


       If input was part of a line-oriented command:

        1. If  interrupt was entered, text input mode shall be terminated and the editor shall return to command mode.
           The terminal shall be alerted.


        2. If <ESC> was entered, text input mode shall be terminated and the command shall continue execution with the
           input provided.


       Otherwise, terminate text input mode and return to command mode.

       Any autoindent characters entered on newly created lines that have no other non- <newline>s shall be deleted.

       Any  leading  autoindent  and  <blank>s  on  newly created lines shall be rewritten to be the minimum number of
       <blank>s possible.

       The screen shall be redisplayed as necessary to match the contents of the edit buffer.

       Current line: Unchanged.

       Current column:

        1. If there are text input characters on the current line, the column shall be set to the  last  column  where
           any portion of the last text input character is displayed.


        2. Otherwise, if a character is displayed in the current column, unchanged.


        3. Otherwise, set to column position 1.


EXIT STATUS
       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.


CONSEQUENCES OF ERRORS
       When any error is encountered and the standard input is not a terminal device file, vi shall not write the file
       or return to command or text input mode, and shall terminate with a non-zero exit status.

       Otherwise, when an unrecoverable error is encountered it shall be equivalent to a SIGHUP asynchronous event.

       Otherwise, when an error is encountered, the editor shall behave as specified in Command Descriptions in vi .

       The following sections are informative.

APPLICATION USAGE
       None.

EXAMPLES
       None.

RATIONALE
       See the RATIONALE for ex for more information on vi. Major portions of the vi utility specification point to ex
       to  avoid  inadvertent divergence. While ex and vi have historically been implemented as a single utility, this
       is not required by IEEE Std 1003.1-2001.

       It is recognized that portions of vi would be difficult, if not impossible, to implement  satisfactorily  on  a
       block-mode  terminal,  or a terminal without any form of cursor addressing, thus it is not a mandatory require-
       ment that such features should work on all terminals. It is the intention, however, that  a  vi  implementation
       should provide the full set of capabilities on all terminals capable of supporting them.

       Historically, vi exited immediately if the standard input was not a terminal. IEEE Std 1003.1-2001 permits, but
       does not require, this behavior. An end-of-file condition is not equivalent to an end-of-file character. A com-
       mon end-of-file character, <control>-D, is historically a vi command.

       The  text in the STDOUT section reflects the usage of the verb display in this section; some implementations of
       vi use standard output to write to the terminal, but IEEE Std 1003.1-2001 does not require that to be the case.

       Historically,  implementations  reverted  to  open mode if the terminal was incapable of supporting full visual
       mode.  IEEE Std 1003.1-2001 requires this behavior. Historically, the open mode of vi behaved  roughly  equiva-
       lently  to the visual mode, with the exception that only a single line from the edit buffer (one "buffer line")
       was kept current at any time.  This line was normally displayed on the next-to-last line  of  a  terminal  with
       cursor  addressing (and the last line performed its normal visual functions for line-oriented commands and mes-
       sages).   In  addition,  some  few  commands  behaved  differently  in  open  mode   than   in   visual   mode.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

       Historically, ex and vi implementations have expected text to proceed in the usual European/Latin order of left
       to right, top to bottom. There is no requirement in IEEE Std 1003.1-2001 that this be the case. The  specifica-
       tion was deliberately written using words like "before", "after", "first", and "last" in order to permit imple-
       mentations to support the natural text order of the language.

       Historically, lines past the end of the edit buffer were marked with single tilde ( '~' ) characters; that  is,
       if the one-based display was 20 lines in length, and the last line of the file was on line one, then lines 2-20
       would contain only a single '~' character.

       Historically, the vi editor attempted to display only complete lines at the bottom of the screen (it  did  dis-
       play  partial  lines  at the top of the screen). If a line was too long to fit in its entirety at the bottom of
       the screen, the screen lines where the line would have been displayed were displayed as single '@'  characters,
       instead  of  displaying  part  of the line.  IEEE Std 1003.1-2001 permits, but does not require, this behavior.
       Implementations are encouraged to attempt always to display a complete line at the bottom of  the  screen  when
       doing scrolling or screen positioning by buffer lines.

       Historically,  lines  marked with '@' were also used to minimize output to dumb terminals over slow lines; that
       is, changes local to the cursor were updated, but changes to lines on the screen that were  not  close  to  the
       cursor   were  simply  marked  with  an  '@'  sign  instead  of  being  updated  to  match  the  current  text.
       IEEE Std 1003.1-2001 permits, but does not require this feature because it is used ever less frequently as ter-
       minals become smarter and connections are faster.

   Initialization in ex and vi
       Historically, vi always had a line in the edit buffer, even if the edit buffer was "empty". For example:

        1. The ex command = executed from visual mode wrote "1" when the buffer was empty.


        2. Writes  from  visual  mode  of  an empty edit buffer wrote files of a single character (a <newline>), while
           writes from ex mode of an empty edit buffer wrote empty files.


        3. Put and read commands into an empty edit buffer left an empty line at the top of the edit buffer.


       For consistency, IEEE Std 1003.1-2001 does not permit any of these behaviors.

       Historically, vi did not always return the terminal to its original modes; for example, ICRNL was  modified  if
       it was not originally set. IEEE Std 1003.1-2001 does not permit this behavior.

   Command Descriptions in vi
       Motion commands are among the most complicated aspects of vi to describe. With some exceptions, the text region
       and buffer type effect of a motion command on a vi command are described on a case-by-case basis. The  descrip-
       tions of text regions in IEEE Std 1003.1-2001 are not intended to imply direction; that is, an inclusive region
       from line n to line n+5 is identical to a region from line n+5 to line n. This is of more than academic  inter-
       est-movements  to  marks  can  be  in either direction, and, if the wrapscan option is set, so can movements to
       search points. Historically, lines are always stored into buffers in text order; that is, from the start of the
       edit buffer to the end. IEEE Std 1003.1-2001 requires conformance to historical practice.

       Historically,  command  counts  were  applied to any associated motion, and were multiplicative to any supplied
       motion count. For example, 2cw is the same as c2w, and 2c3w is the same as c6w.  IEEE Std 1003.1-2001  requires
       this  behavior.  Historically,  vi  commands  that  used  bigwords, words, paragraphs, and sentences as objects
       treated groups of empty lines, or lines that contained only <blank>s, inconsistently.   Some  commands  treated
       them  as  a  single  entity,  while  others treated each line separately. For example, the w, W, and B commands
       treated groups of empty lines as individual words; that is, the command would move the cursor to each new empty
       line.  The  e  and E commands treated groups of empty lines as a single word; that is, the first use would move
       past the group of lines. The b command would just beep at the user, or if done from the start of the line as  a
       motion command, fail in unexpected ways. If the lines contained only (or ended with) <blank>s, the w and W com-
       mands would just beep at the user, the E and e commands would treat the group as a single word, and the B and b
       commands  would  treat  the  lines  as  individual  words.  For  consistency  and  simplicity of specification,
       IEEE Std 1003.1-2001 requires that all vi commands treat groups of empty or blank lines as a single entity, and
       that movement through lines ending with <blank>s be consistent with other movements.

       Historically,  vi documentation indicated that any number of double quotes were skipped after punctuation marks
       at sentence boundaries; however, implementations only skipped single quotes. IEEE Std 1003.1-2001 requires both
       to be skipped.

       Historically,  the  first and last characters in the edit buffer were word boundaries. This historical practice
       is required by IEEE Std 1003.1-2001.

       Historically, vi attempted to update the minimum number of columns on the screen possible, which could lead  to
       misleading  information being displayed. IEEE Std 1003.1-2001 makes no requirements other than that the current
       character being entered is displayed correctly, leaving all other decisions in this area up to the  implementa-
       tion.

       Historically,  lines  were  arbitrarily  folded between columns of any characters that required multiple column
       positions  on  the  screen,  with  the  exception  of  tabs,  which  terminated  at  the   right-hand   margin.
       IEEE Std 1003.1-2001  permits the former and requires the latter. Implementations that do not arbitrarily break
       lines between columns of characters that occupy multiple column positions should not permit the cursor to  rest
       on a column that does not contain any part of a character.

       The  historical  vi  had  a problem in that all movements were by buffer lines, not by display or screen lines.
       This is often the right thing to do; for example, single line movements, such as j or k, should work on  buffer
       lines.  Commands like dj, or j., where . is a change command, only make sense for buffer lines. It is not, how-
       ever, the right thing to do for screen motion or scrolling commands like <control>-D, <control>-F,  and  H.  If
       the window is fairly small, using buffer lines in these cases can result in completely random motion; for exam-
       ple, 1 <control>-D can result in a completely changed screen, without any overlap. This is clearly not what the
       user  wanted.  The problem is even worse in the case of the H, L, and M commands-as they position the cursor at
       the first non- <blank> of the line, they may all refer to the same location in large lines, and will result  in
       no movement at all.

       In  addition, if the line is larger than the screen, using buffer lines can make it impossible to display parts
       of the line-there are not any commands that do not display the beginning of the line in historical vi,  and  if
       both  the  beginning  and end of the line cannot be on the screen at the same time, the user suffers.  Finally,
       the page and half-page scrolling commands historically moved to the first non- <blank> in the new line. If  the
       line  is  approximately  the  same size as the screen, this is inadequate because the cursor before and after a
       <control>-D command will refer to the same location on the screen.

       Implementations of ex and vi exist that do not have these problems because the relevant commands ( <control>-B,
       <control>-D,  <control>-F,  <control>-U,  <control>-Y,  <control>-E,  H,  L, and M) operate on display (screen)
       lines, not (edit) buffer lines.

       IEEE Std 1003.1-2001 does not permit this behavior by default because the  standard  developers  believed  that
       users  would  find it too confusing. However, historical practice has been relaxed. For example, ex and vi his-
       torically attempted, albeit sometimes unsuccessfully, to never put part of a  line  on  the  last  lines  of  a
       screen; for example, if a line would not fit in its entirety, no part of the line was displayed, and the screen
       lines corresponding to the line contained single '@' characters. This behavior is permitted, but  not  required
       by IEEE Std 1003.1-2001, so that it is possible for implementations to support long lines in small screens more
       reasonably without changing the commands to be oriented to the display (instead of  oriented  to  the  buffer).
       IEEE Std 1003.1-2001 also permits implementations to refuse to edit any edit buffer containing a line that will
       not fit on the screen in its entirety.

       The display area (for example, the value of the window edit option) has historically been "grown", or expanded,
       to  display new text when local movements are done in displays where the number of lines displayed is less than
       the maximum possible.  Expansion has historically been the first choice, when the target line is less than  the
       maximum  possible  expansion value away.  Scrolling has historically been the next choice, done when the target
       line is less than half a display away, and otherwise, the screen was redrawn. There were  exceptions,  however,
       in  that  ex commands generally always caused the screen to be redrawn. IEEE Std 1003.1-2001 does not specify a
       standard behavior because there may be external issues, such as connection speed, the number of characters nec-
       essary  to redraw as opposed to scroll, or terminal capabilities that implementations will have to accommodate.

       The current line in IEEE Std 1003.1-2001 maps one-to-one to a buffer line in the file. The current column  does
       not.   There are two different column values that are described by IEEE Std 1003.1-2001.  The first is the cur-
       rent column value as set by many of the vi commands. This value is remembered for the lifetime of  the  editor.
       The second column value is the actual position on the screen where the cursor rests. The two are not always the
       same. For example, when the cursor is backed by a multi-column character, the actual  cursor  position  on  the
       screen  has  historically  been  the  last column of the character in command mode, and the first column of the
       character in input mode.

       Commands that set the current line, but that do not set the current cursor value (for example, j and k) attempt
       to get as close as possible to the remembered column position, so that the cursor tends to restrict itself to a
       vertical column as the user moves around in the edit buffer. IEEE Std 1003.1-2001 requires conformance to  his-
       torical  practice,  requiring  that the display location of the cursor on the display line be adjusted from the
       current column value as necessary to support this historical behavior.

       Historically, only a single line (and for some terminals, a single line minus 1 column) of characters could  be
       entered  by  the user for the line-oriented commands; that is, :, !, /, or ?. IEEE Std 1003.1-2001 permits, but
       does not require, this limitation.

       Historically, "soft" errors in vi caused the terminal to be alerted, but no error message was displayed.  As  a
       general  rule,  no  error  message was displayed for errors in command execution in vi, when the error resulted
       from the user attempting an invalid or impossible action, or when a searched-for object was not found. Examples
       of  soft errors included h at the left margin, <control>-B or [[ at the beginning of the file, 2G at the end of
       the file, and so on. In addition, errors such as %, ]], }, ), N, n,  f,  F,  t,  and  T  failing  to  find  the
       searched-for object were soft as well. Less consistently, / and ? displayed an error message if the pattern was
       not found, /, ?, N, and n displayed an error message if no previous regular expression had been specified,  and
       ;  did  not  display an error message if no previous f, F, t, or T command had occurred. Also, behavior in this
       area might reasonably be based on a runtime evaluation of the speed of a  network  connection.   Finally,  some
       implementations have provided error messages for soft errors in order to assist naive users, based on the value
       of a verbose edit option. IEEE Std 1003.1-2001 does not list specific errors for which an error  message  shall
       be  displayed.   Implementations  should  conform to historical practice in the absence of any strong reason to
       diverge.

   Page Backwards
       The <control>-B and <control>-F commands historically considered it an error to attempt to page past the begin-
       ning  or end of the file, whereas the <control>-D and <control>-U commands simply moved to the beginning or end
       of the file.  For consistency, IEEE Std 1003.1-2001 requires the latter behavior for  all  four  commands.  All
       four commands still consider it an error if the current line is at the beginning ( <control>-B, <control>-U) or
       end ( <control>-F, <control>-D) of the file. Historically, the <control>-B and <control>-F  commands  skip  two
       lines  in  order  to  include  overlapping lines when a single command is entered. This makes less sense in the
       presence of a count, as there will be, by definition, no overlapping lines. The actual calculation used by his-
       torical implementations of the vi editor for <control>-B was:


              ((current first line) - count x (window edit option)) +2

       and for <control>-F was:


              ((current first line) + count x (window edit option)) -2

       This  calculation  does  not  work well when intermixing commands with and without counts; for example, 3 <con-
       trol>-F is not equivalent to entering the <control>-F command three times, and is not  reversible  by  entering
       the   <control>-B   command   three   times.   For  consistency  with  other  vi  commands  that  take  counts,
       IEEE Std 1003.1-2001 requires a different calculation.

   Scroll Forward
       The 4BSD and System V implementations of vi differed on the initial value used  by  the  scroll  command.  4BSD
       used:


              ((window edit option) +1) /2

       while   System  V  used  the  value  of  the  scroll  edit  option.  The  System  V  version  is  specified  by
       IEEE Std 1003.1-2001 because the standard developers believed that it was more intuitive and permitted the user
       a method of setting the scroll value initially without also setting the number of lines that are displayed.

   Scroll Forward by Line
       Historically,  the  <control>-E  and  <control>-Y  commands considered it an error if the last and first lines,
       respectively, were already on the screen. IEEE Std 1003.1-2001 requires  conformance  to  historical  practice.
       Historically,  the <control>-E and <control>-Y commands had no effect in open mode.  For simplicity and consis-
       tency of specification, IEEE Std 1003.1-2001 requires that they behave as usual,  albeit  with  a  single  line
       screen.

   Clear and Redisplay
       The  historical  <control>-L command refreshed the screen exactly as it was supposed to be currently displayed,
       replacing any '@' characters for lines that had been deleted but not updated on the screen with  refreshed  '@'
       characters.   The  intent  of the <control>-L command is to refresh when the screen has been accidentally over-
       written; for example, by a write command from another user, or modem noise.

   Redraw Screen
       The historical <control>-R command redisplayed only when necessary to update lines that had  been  deleted  but
       not updated on the screen and that were flagged with '@' characters. There is no requirement that the screen be
       in any way refreshed if no lines of this form are currently displayed. IEEE Std 1003.1-2001 permits implementa-
       tions  to  extend  this command to refresh lines on the screen flagged with '@' characters because they are too
       long to be displayed in the current framework; however, the current line and column need not be modified.

   Search for tagstring
       Historically, the first non- <blank> at or after the cursor was the first character, and all subsequent charac-
       ters  that  were word characters, up to the end of the line, were included. For example, with the cursor on the
       leading space or on the '#' character in the text "#bar@", the tag was "#bar" . On the  character  'b'  it  was
       "bar", and on the 'a' it was "ar" . IEEE Std 1003.1-2001 requires this behavior.

   Replace Text with Results from Shell Command
       Historically,  the  <,  >,  and  !  commands considered most cursor motions other than line-oriented motions an
       error; for example, the command >/foo<CR> succeeded, while the command >l failed, even though the  text  region
       described  by  the  two  commands might be identical.  For consistency, all three commands only consider entire
       lines and not partial lines, and the region is defined as any line that contains a character that was specified
       by the motion.

   Move to Matching Character
       Other  matching  characters have been left implementation-defined in order to allow extensions such as matching
       '<' and '>' for searching HTML, or #ifdef, #else, and #endif for searching C source.

   Repeat Substitution
       IEEE Std 1003.1-2001 requires that any c and g flags specified to the previous substitute command  be  ignored;
       however, the r flag may still apply, if supported by the implementation.

   Return to Previous (Context or Section)
       The  [[, ]], (, ), {, and } commands are all affected by "section boundaries", but in some historical implemen-
       tations not all of the commands recognize the same section boundaries. This is a bug,  not  a  feature,  and  a
       unique  section-boundary  algorithm  was not described for each command.  One special case that is preserved is
       that the sentence command moves to the end of the last line of the edit buffer while the other commands  go  to
       the  beginning,  in order to preserve the traditional character cut semantics of the sentence command. Histori-
       cally, vi section boundaries at the beginning and end of the edit buffer were the first  non-  <blank>  on  the
       first  and  last  lines  of  the edit buffer if one exists; otherwise, the last character of the first and last
       lines of the edit buffer if one exists.  To increase consistency with other section locations,  this  has  been
       simplified  by  IEEE Std 1003.1-2001  to the first character of the first and last lines of the edit buffer, or
       the first and the last lines of the edit buffer if they are empty.

       Sentence boundaries were problematic in the historical vi. They were not only the boundaries as defined for the
       section  and  paragraph commands, but they were the first non- <blank> that occurred after those boundaries, as
       well. Historically, the vi section commands were documented as taking an optional window size as a  count  pre-
       ceding  the command. This was not implemented in historical versions, so IEEE Std 1003.1-2001 requires that the
       count repeat the command, for consistency with other vi commands.

   Repeat
       Historically, mapped commands other than text input commands could not be repeated using  the  period  command.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

       The  restrictions  on  the interpretation of special characters (for example, <control>-H) in the repetition of
       text input mode commands is intended to match historical practice. For example, given the input sequence:


              iab<control>-H<control>-H<control>-Hdef<escape>

       the user should be informed of an error when the sequence is first entered, but not during  a  command  repeti-
       tion.  The  character <control>-T is specifically exempted from this restriction. Historical implementations of
       vi ignored <control>-T  characters  that  were  input  in  the  original  command  during  command  repetition.
       IEEE Std 1003.1-2001 prohibits this behavior.

   Find Regular Expression
       Historically,  commands  did not affect the line searched to or from if the motion command was a search ( /, ?,
       N, n) and the final position was the start/end of the line. There were some special cases and vi was  not  con-
       sistent.  IEEE Std 1003.1-2001  does not permit this behavior, for consistency. Historical implementations per-
       mitted but were unable to handle searches as motion commands that wrapped (that is,  due  to  the  edit  option
       wrapscan) to the original location. IEEE Std 1003.1-2001 requires that this behavior be treated as an error.

       Historically,  the  syntax "/RE/0" was used to force the command to cut text in line mode. IEEE Std 1003.1-2001
       requires conformance to historical practice.

       Historically, in open mode, a z specified to a search command redisplayed the current line instead of  display-
       ing  the  current  screen  with  the current line highlighted. For consistency and simplicity of specification,
       IEEE Std 1003.1-2001 does not permit this behavior.

       Historically, trailing z commands were permitted and ignored if entered as part of a search used  as  a  motion
       command. For consistency and simplicity of specification, IEEE Std 1003.1-2001 does not permit this behavior.

   Execute an ex Command
       Historically,  vi  implementations restricted the commands that could be entered on the colon command line (for
       example, append and change), and some other commands were known to cause them  to  fail  catastrophically.  For
       consistency,  IEEE Std 1003.1-2001 does not permit these restrictions. When executing an ex command by entering
       :, it is not possible to enter a <newline> as part of the command because it is considered the end of the  com-
       mand.  A  different  approach  is to enter ex command mode by using the vi Q command (and later resuming visual
       mode with the ex vi command). In ex command mode, the single-line limitation does not exist. So,  for  example,
       the following is valid:


              Q
              s/break here/break\
              here/
              vi

       IEEE Std 1003.1-2001 requires that, if the ex command overwrites any part of the screen that would be erased by
       a refresh, vi pauses for a character from the user. Historically, this character could be  any  character;  for
       example,  a character input by the user before the message appeared, or even a mapped character. This is proba-
       bly a bug, but implementations that have tried to be more rigorous by requiring that the user enter a  specific
       character,  or that the user enter a character after the message was displayed, have been forced by user indig-
       nation back into historical behavior.  IEEE Std 1003.1-2001 requires conformance to historical practice.

   Shift Left (Right)
       Refer to the Rationale for the ! and / commands. Historically, the < and > commands sometimes moved the  cursor
       to  the first non- <blank> (for example if the command was repeated or with _ as the motion command), and some-
       times left it unchanged. IEEE Std 1003.1-2001 does not permit this inconsistency, requiring  instead  that  the
       cursor  always  move to the first non- <blank>. Historically, the < and > commands did not support buffer argu-
       ments, although some implementations allow the specification of an optional buffer. This  behavior  is  neither
       required nor disallowed by IEEE Std 1003.1-2001.

   Execute
       Historically,  buffers  could  execute  other  buffers,  and  loops,  infinite  and  otherwise,  were possible.
       IEEE Std 1003.1-2001 requires conformance to historical practice.  The * buffer syntax of ex is not required in
       vi,  because  it  is not historical practice and has been used in some vi implementations to support additional
       scripting languages.

   Reverse Case
       Historically, the ~ command ignored any associated count, and acted only on the characters in the current line.
       For  consistency with other vi commands, IEEE Std 1003.1-2001 requires that an associated count act on the next
       count characters, and that the command move to subsequent lines if warranted by count, to make it  possible  to
       modify  large  pieces  of text in a reasonably efficient manner. There exist vi implementations that optionally
       require an associated motion command for the ~  command.  Implementations  supporting  this  functionality  are
       encouraged  to  base  it on the tildedop edit option and handle the text regions and cursor positioning identi-
       cally to the yank command.

   Append
       Historically, counts specified to the A, a, I, and i commands repeated the input of the first line count times,
       and  did  not repeat the subsequent lines of the input text. IEEE Std 1003.1-2001 requires that the entire text
       input be repeated count times.

   Move Backward to Preceding Word
       Historically,  vi  became  confused  if  word  commands  were  used  as  motion  commands   in   empty   files.
       IEEE Std 1003.1-2001  requires  that  this  be an error. Historical implementations of vi had a large number of
       bugs in the word movement commands, and they varied greatly in behavior in the presence of empty lines, "words"
       made up of a single character, and lines containing only <blank>s. For consistency and simplicity of specifica-
       tion, IEEE Std 1003.1-2001 does not permit this behavior.

   Change to End-of-Line
       Some historical implementations of the C command did not behave as described by IEEE Std 1003.1-2001 when the $
       key  was  remapped because they were implemented by pushing the $ key onto the input queue and reprocessing it.
       IEEE Std 1003.1-2001 does not permit this behavior. Historically, the  C,  S,  and  s  commands  did  not  copy
       replaced  text  into the numeric buffers. For consistency and simplicity of specification, IEEE Std 1003.1-2001
       requires that they behave like their respective c commands in all respects.

   Delete
       Historically, lines in open mode that were deleted were scrolled up, and an @ glyph written over the  beginning
       of the line. In the case of terminals that are incapable of the necessary cursor motions, the editor erased the
       deleted line from the screen. IEEE Std 1003.1-2001 requires conformance to historical practice; that is, if the
       terminal cannot display the '@' character, the line cannot remain on the screen.

   Delete to End-of-Line
       Some historical implementations of the D command did not behave as described by IEEE Std 1003.1-2001 when the $
       key was remapped because they were implemented by pushing the $ key onto the input queue and  reprocessing  it.
       IEEE Std 1003.1-2001 does not permit this behavior.

   Join
       An  historical  oddity  of  vi  is  that  the  commands J, 1J, and 2J are all equivalent.  IEEE Std 1003.1-2001
       requires conformance to historical practice.  The vi J command is specified in terms of  the  ex  join  command
       with  an  ex command count value. The address correction for a count that is past the end of the edit buffer is
       necessary for historical compatibility for both ex and vi.

   Mark Position
       Historical practice is that only lowercase letters, plus ''' and '", could be used to mark a  cursor  position.
       IEEE Std 1003.1-2001  requires  conformance  to  historical practice, but encourages implementations to support
       other characters as marks as well.

   Repeat Regular Expression Find (Forward and Reverse)
       Historically, the N and n commands could not be used as motion components for the c command. With the exception
       of  the cN command, which worked if the search crossed a line boundary, the text region would be discarded, and
       the user would not be in text input mode. For consistency and simplicity of specification, IEEE Std 1003.1-2001
       does not permit this behavior.

   Insert Empty Line (Below and Above)
       Historically, counts to the O and o commands were used as the number of physical lines to open, if the terminal
       was dumb and the slowopen option was not set. This was intended to minimize traffic over slow  connections  and
       repainting  for  dumb  terminals. IEEE Std 1003.1-2001 does not permit this behavior, requiring that a count to
       the open command behave as for other text input commands. This change to historical practice was made for  con-
       sistency, and because a superset of the functionality is provided by the slowopen edit option.

   Put from Buffer (Following and Before)
       Historically,  counts  to  the  p  and  P  commands were ignored if the buffer was a line mode buffer, but were
       (mostly) implemented as described in IEEE Std 1003.1-2001 if the buffer was a character  mode  buffer.  Because
       implementations  exist  that do not have this limitation, and because pasting lines multiple times is generally
       useful, IEEE Std 1003.1-2001 requires that count be supported for all p and P commands.

       Historical implementations of vi were widely known to have major problems in the p and P commands, particularly
       when  unusual  regions  of text were copied into the edit buffer. The standard developers viewed these as bugs,
       and they are not permitted for consistency and simplicity of specification.

       Historically, a P or p command (or an ex put command executed from open or visual mode) executed  in  an  empty
       file,  left  an  empty  line  as  the  first line of the file. For consistency and simplicity of specification,
       IEEE Std 1003.1-2001 does not permit this behavior.

   Replace Character
       Historically, the r command did not correctly handle the erase and word erase characters as arguments, nor  did
       it  handle  an  associated  count greater than 1 with a <carriage-return> argument, for which it replaced count
       characters with a single <newline>. IEEE Std 1003.1-2001 does not permit these inconsistencies.

       Historically, the r command permitted the <control>-V escaping of entered characters, such  as  <ESC>  and  the
       <carriage-return>;    however,   it   required   two   leading   <control>-V   characters   instead   of   one.
       IEEE Std 1003.1-2001 requires that this be changed for consistency with the other text input commands of vi.

       Historically, it is an error to enter the r command if there are less than count characters  at  or  after  the
       cursor  in  the  line.  While  a reasonable and unambiguous extension would be to permit the r command on empty
       lines, it would require that too large a count be adjusted to match the number of characters at  or  after  the
       cursor   for   consistency,   which   is  sufficiently  different  from  historical  practice  to  be  avoided.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

   Replace Characters
       Historically, if there were autoindent characters in the line on which the R command was  run,  and  autoindent
       was  set,  the first <newline> would be properly indented and no characters would be replaced by the <newline>.
       Each additional <newline> would replace n characters, where n was the number of characters that were needed  to
       indent  the  rest  of  the line to the proper indentation level. This behavior is a bug and is not permitted by
       IEEE Std 1003.1-2001.

   Undo
       Historical practice for cursor positioning after undoing commands was mixed. In most cases, when  undoing  com-
       mands  that  affected a single line, the cursor was moved to the start of added or changed text, or immediately
       after deleted text. However, if the user had moved from the line being changed, the column was  either  set  to
       the  first  non-  <blank>,  returned to the origin of the command, or remained unchanged. When undoing commands
       that affected multiple lines or entire lines, the cursor was moved to the first character  in  the  first  line
       restored.  As  an example of how inconsistent this was, a search, followed by an o text input command, followed
       by an undo would return the cursor to the location where the o command was entered, but a cw  command  followed
       by  an  o  command  followed  by  an  undo  would  return  the  cursor  to  the first non- <blank> of the line.
       IEEE Std 1003.1-2001 requires the most useful of these behaviors, and discards the least useful, in the  inter-
       est of consistency and simplicity of specification.

   Yank
       Historically,  the  yank  command did not move to the end of the motion if the motion was in the forward direc-
       tion. It moved to the end of the motion if the motion was in the backward direction, except for the _  command,
       or  for  the G and ' commands when the end of the motion was on the current line.  This was further complicated
       by the fact that for a number of motion commands, the yank command moved the cursor  but  did  not  update  the
       screen;  for  example,  a  subsequent command would move the cursor from the end of the motion, even though the
       cursor on the screen had not reflected the cursor movement for the yank command. IEEE Std 1003.1-2001  requires
       that  all  yank  commands associated with backward motions move the cursor to the end of the motion for consis-
       tency, and specifically, to make ' commands as motions consistent with search patterns as motions.

   Yank Current Line
       Some historical implementations of the Y command did not behave as described by IEEE Std 1003.1-2001  when  the
       '_' key was remapped because they were implemented by pushing the '_' key onto the input queue and reprocessing
       it. IEEE Std 1003.1-2001 does not permit this behavior.

   Redraw Window
       Historically,  the  z  command  always  redrew  the  screen.  This   is   permitted   but   not   required   by
       IEEE Std 1003.1-2001, because of the frequent use of the z command in macros such as map n nz. for screen posi-
       tioning, instead of its use to change the screen size. The  standard  developers  believed  that  expanding  or
       scrolling the screen offered a better interface for users. The ability to redraw the screen is preserved if the
       optional new window size is specified, and in the <control>-L and <control>-R commands.

       The semantics of z^ are confusing at best. Historical practice is that the screen before the screen that  ended
       with the specified line is displayed. IEEE Std 1003.1-2001 requires conformance to historical practice.

       Historically, the z command would not display a partial line at the top or bottom of the screen. If the partial
       line would normally have been displayed at the bottom of the screen, the command worked, but the  partial  line
       was  replaced  with  '@'  characters.  If the partial line would normally have been displayed at the top of the
       screen, the command would fail.  For consistency and simplicity of specification, IEEE Std 1003.1-2001 does not
       permit this behavior.

       Historically,  the z command with a line specification of 1 ignored the command. For consistency and simplicity
       of specification, IEEE Std 1003.1-2001 does not permit this behavior.

       Historically, the z command did not set the cursor column to the first non- <blank> for the  character  if  the
       first  screen  was to be displayed, and was already displayed. For consistency and simplicity of specification,
       IEEE Std 1003.1-2001 does not permit this behavior.

   Input Mode Commands in vi
       Historical implementations of vi did not permit the user to erase more than a single line of input, or  to  use
       normal erase characters such as line erase, worderase, and erase to erase autoindent characters. As there exist
       implementations of vi that do not have these limitations, both behaviors are  permitted,  but  only  historical
       practice  is  required. In the case of these extensions, vi is required to pause at the autoindent and previous
       line boundaries.

       Historical implementations of vi updated only the portion of the screen where the current cursor character  was
       displayed.  For example, consider the vi input keystrokes:


              iabcd<escape>0C<tab>

       Historically,  the  <tab>  would  overwrite  the characters "abcd" when it was displayed. Other implementations
       replace only the 'a' character with the <tab>, and then push the rest of the characters ahead  of  the  cursor.
       Both  implementations  have  problems.  The  historical implementation is probably visually nicer for the above
       example; however, for the keystrokes:


              iabcd<ESC>0R<tab><ESC>

       the historical implementation results in the string "bcd" disappearing and then magically reappearing when  the
       <ESC>  character  is entered. IEEE Std 1003.1-2001 requires the former behavior when overwriting erase-columns-
       that is, overwriting characters that are no longer logically part of the edit buffer-and  the  latter  behavior
       otherwise.

       Historical implementations of vi discarded the <control>-D and <control>-T characters when they were entered at
       places where their command functionality was not appropriate.  IEEE Std 1003.1-2001  requires  that  the  <con-
       trol>-T  functionality always be available, and that <control>-D be treated as any other key when not operating
       on autoindent characters.

   NUL
       Some historical implementations of vi limited the number of characters entered using the NUL input character to
       256 bytes. IEEE Std 1003.1-2001 permits this limitation; however, implementations are encouraged to remove this
       limit.

   <control>-D
       See also Rationale for the input mode command <newline>. The hidden assumptions in the <control>-D command (and
       in  the vi autoindent specification in general) is that <space>s take up a single column on the screen and that
       <tab>s are comprised of an integral number of <space>s.

   <newline>
       Implementations are permitted to rewrite autoindent characters in the line when  <newline>,  <carriage-return>,
       <control>-D,  and  <control>-T are entered, or when the shift commands are used, because historical implementa-
       tions have both done so and found it necessary to do so.  For example, a <control>-D when the  cursor  is  pre-
       ceded  by  a  single  <tab>,  with  tabstop  set  to 8, and shiftwidth set to 3, will result in the <tab> being
       replaced by several <space>s.

   <control>-T
       See also the Rationale for the input mode command <newline>. Historically, <control>-T only worked if  no  non-
       <blank>s had yet been input in the current input line. In addition, the characters inserted by <control>-T were
       treated as autoindent characters, and could not be erased using normal user erase characters. Because implemen-
       tations  exist  that  do  not  have  these limitations, and as moving to a column boundary is generally useful,
       IEEE Std 1003.1-2001 requires that both limitations be removed.

   <control>-V
       Historically,  vi  used  ^V,  regardless  of  the  value  of  the  literal-next  character  of  the   terminal.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

       The uses described for <control>-V can also be accomplished with <control>-Q, which is useful on terminals that
       use <control>-V for the down-arrow function. However, most historical implementations use <control>-Q  for  the
       termios  START character, so the editor will generally not receive the <control>-Q unless stty ixon mode is set
       to off. (In addition, some historical implementations of vi explicitly set ixon mode to on, so it was difficult
       for  the  user  to  set it to off.) Any of the command characters described in IEEE Std 1003.1-2001 can be made
       ineffective by their selection as termios control characters, using the stty utility or other methods described
       in the System Interfaces volume of IEEE Std 1003.1-2001.

   <ESC>
       Historically,  SIGINT  alerted  the  terminal when used to end input mode.  This behavior is permitted, but not
       required, by IEEE Std 1003.1-2001.

FUTURE DIRECTIONS
       None.

SEE ALSO
       ed, ex, stty

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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                               VI(1P)