'\" et
.TH VI "1P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.

.SH NAME
vi
\(em screen-oriented (visual) display editor
.SH SYNOPSIS
.LP
.nf
vi \fB[\fR\(mirR\fB] [\fR\(mic \fIcommand\fB] [\fR\(mit \fItagstring\fB] [\fR\(miw \fIsize\fB] [\fIfile\fR...\fB]\fR
.fi
.SH 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.
.P
The
.IR vi
(visual) utility is a screen-oriented text editor. Only the open and
visual modes of the editor are described in POSIX.1\(hy2008; see the line editor
.IR ex
for additional editing capabilities used in
.IR vi .
The user can switch back and forth between
.IR vi
and
.IR ex
and execute
.IR ex
commands from within
.IR vi .
.P
This reference page uses the term
.IR "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.
.P
When using
.IR 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.
.P
Certain terminals do not have all the capabilities necessary to support
the complete
.IR 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 POSIX.1\(hy2008
or report an error describing the terminal-related deficiency.
.SH OPTIONS
The
.IR vi
utility shall conform to the Base Definitions volume of POSIX.1\(hy2008,
.IR "Section 12.2" ", " "Utility Syntax Guidelines",
except that
.BR '\(pl' 
may be recognized as an option delimiter as well as
.BR '\(mi' .
.P
The following options shall be supported:
.IP "\fB\(mic\ \fIcommand\fR" 10
See the
.IR ex
command description of the
.BR \(mic
option.
.IP "\fB\(mir\fP" 10
See the
.IR ex
command description of the
.BR \(mir
option.
.IP "\fB\(miR\fP" 10
See the
.IR ex
command description of the
.BR \(miR
option.
.IP "\fB\(mit\ \fItagstring\fR" 10
See the
.IR ex
command description of the
.BR \(mit
option.
.IP "\fB\(miw\ \fIsize\fR" 10
See the
.IR ex
command description of the
.BR \(miw
option.
.SH OPERANDS
See the OPERANDS section of the
.IR ex
command for a description of the operands supported by the
.IR vi
command.
.SH 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.
.P
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.
.SH "INPUT FILES"
See the INPUT FILES section of the
.IR ex
command for a description of the input files supported by the
.IR vi
command.
.SH "ENVIRONMENT VARIABLES"
See the ENVIRONMENT VARIABLES section of the
.IR ex
command for the environment variables that affect the execution of the
.IR vi
command.
.SH "ASYNCHRONOUS EVENTS"
See the ASYNCHRONOUS EVENTS section of the
.IR ex
for the asynchronous events that affect the execution of the
.IR vi
command.
.SH STDOUT
If standard output is not a terminal device, undefined results occur.
.P
Standard output may be used for writing prompts to the user, for
informational messages, and for writing lines from the file.
.SH STDERR
If standard output is not a terminal device, undefined results occur.
.P
The standard error shall be used only for diagnostic messages.
.SH "OUTPUT FILES"
See the OUTPUT FILES section of the
.IR ex
command for a description of the output files supported by the
.IR vi
command.
.SH "EXTENDED DESCRIPTION"
If the terminal does not have the capabilities necessary to support an
unspecified portion of the
.IR vi
definition, implementations shall start initially in
.IR ex
mode or open mode. Otherwise, after initialization,
.IR 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
.IR "Terminate Command or Input Mode".
.SS "Initialization in ex and vi"
.P
See
.IR "Initialization in ex and vi"
for a description of
.IR ex
and
.IR vi
initialization for the
.IR vi
utility.
.SS "Command Descriptions in vi"
.P
The following symbols are used in this reference page to represent
arguments to commands.
.IP "\fIbuffer\fR" 8
See the description of
.IR buffer
in the EXTENDED DESCRIPTION section of the
.IR ex
utility; see
.IR "Command Descriptions in ex".
.RS 8 
.P
In open and visual mode, when a command synopsis shows both [\c
.IR buffer ]
and [\c
.IR count ]
preceding the command name, they can be specified in either order.
.RE
.IP "\fIcount\fR" 8
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.
.RS 8 
.P
The Synopsis lines for the
.IR vi
commands
<control>\(hyG,
<control>\(hyL,
<control>\(hyR,
<control>\(hy],
.BR % ,
.BR & ,
.BR ^ ,
.BR D ,
.BR m ,
.BR M ,
.BR Q ,
.BR u ,
.BR U ,
and
.BR ZZ
do not have
.IR count
as an optional argument. Regardless, it shall not be an error to
specify a
.IR count
to these commands, and any specified
.IR count
shall be ignored.
.RE
.IP "\fImotion\fR" 8
An optional trailing argument used by the
.BR ! ,
.BR < ,
.BR > ,
.BR c ,
.BR d ,
and
.BR 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
characters repeated or one of several other
.IR vi
commands (listed in the following table). Each of the applicable
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.
.RS 8 
.P
Commands that take
.IR 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.
.P
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.
.P
The following commands shall be valid cursor motion commands:
.sp
.RS 4
.nf
\fB
<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
.fi \fR
.P
.RE
.P
Any
.IR count
that is specified to a command that has an associated motion command
shall be applied to the motion command. If a
.IR count
is applied to both the command and its associated motion command, the
effect shall be multiplicative.
.RE
.P
The following symbols are used in this section to specify locations
in the edit buffer:
.IP "\fIcurrent\ character\fP" 8
.br
The character that is currently indicated by the cursor.
.IP "\fIend\ of\ a\ line\fP" 8
.br
The point located between the last non-\c
<newline>
(if any) and the terminating
<newline>
of a line. For an empty line, this location coincides with the
beginning of the line.
.IP "\fIend\ of\ the\ edit\ buffer\fP" 8
.br
The location corresponding to the end of the last line in the edit
buffer.
.P
The following symbols are used in this section to specify command
actions:
.IP "\fIbigword\fP" 8
In the POSIX locale,
.IR vi
shall recognize four kinds of
.IR bigwords :
.RS 8 
.IP " 1." 4
A maximal sequence of non-\c
<blank>
characters preceded and followed by
<blank>
characters or the beginning or end of a line or the edit buffer
.IP " 2." 4
One or more sequential blank lines
.IP " 3." 4
The first character in the edit buffer
.IP " 4." 4
The last non-\c
<newline>
in the edit buffer
.RE
.IP "\fIword\fP" 8
In the POSIX locale,
.IR vi
shall recognize five kinds of words:
.RS 8 
.IP " 1." 4
A maximal sequence of letters, digits, and underscores, delimited at
both ends by:
.RS 4 
.IP -- 4
Characters other than letters, digits, or underscores
.IP -- 4
The beginning or end of a line
.IP -- 4
The beginning or end of the edit buffer
.RE
.IP " 2." 4
A maximal sequence of characters other than letters, digits, underscores, or
<blank>
characters, delimited at both ends by:
.RS 4 
.IP -- 4
A letter, digit, underscore
.IP -- 4
<blank>
characters
.IP -- 4
The beginning or end of a line
.IP -- 4
The beginning or end of the edit buffer
.RE
.IP " 3." 4
One or more sequential blank lines
.IP " 4." 4
The first character in the edit buffer
.IP " 5." 4
The last non-\c
<newline>
in the edit buffer
.RE
.IP "\fIsection\ boundary\fR" 8
.br
A
.IR "section boundary"
is one of the following:
.RS 8 
.IP " 1." 4
A line whose first character is a
<form-feed>
.IP " 2." 4
A line whose first character is an open curly brace (\c
.BR '{' )
.IP " 3." 4
A line whose first character is a
<period>
and whose second and third characters match a two-character pair in the
.BR sections
edit option (see
.IR ed )
.IP " 4." 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
.BR sections
edit option, where the second character of the two-character pair is a
<space>
.IP " 5." 4
The first line of the edit buffer
.IP " 6." 4
The last line of the edit buffer if the last line of the edit buffer is
empty or if it is a
.BR ]]
or
.BR }
command; otherwise, the last non-\c
<newline>
of the last line of the edit buffer
.RE
.IP "\fIparagraph\ boundary\fR" 8
.br
A
.IR "paragraph boundary"
is one of the following:
.RS 8 
.IP " 1." 4
A section boundary
.IP " 2." 4
A line whose first character is a
<period>
and whose second and third characters match a two-character pair in the
.BR paragraphs
edit option (see
.IR ed )
.IP " 3." 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
.IR paragraphs
edit option, where the second character of the two-character pair is a
<space>
.IP " 4." 4
One or more sequential blank lines
.RE
.IP "\fIremembered\ search\ direction\fR" 8
.br
See the description of \fIremembered search direction\fP in
.IR ed .
.IP "\fIsentence\ boundary\fR" 8
.br
A
.IR "sentence boundary"
is one of the following:
.RS 8 
.IP " 1." 4
A paragraph boundary
.IP " 2." 4
The first non-\c
<blank>
that occurs after a paragraph boundary
.IP " 3." 4
The first non-\c
<blank>
that occurs after a
<period>
(\c
.BR '.' ),
<exclamation-mark>
(\c
.BR '!' ),
or
<question-mark>
(\c
.BR '?' ),
followed by two
<space>
characters or the end of a line; any number of closing parenthesis (\c
.BR ')' ),
closing brackets (\c
.BR ']' ),
double-quote (\c
.BR '\&"' ),
or single-quote (\c
<apostrophe>)
characters can appear between the punctuation mark and the two
<space>
characters or end-of-line
.RE
.P
In the remainder of the description of the
.IR 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''.
.P
If there are display lines on the screen for which there are no
corresponding buffer lines because they correspond to lines that would
be after the end of the file, they shall be displayed as a single
<tilde>
(\c
.BR '~' )
character, plus the terminating
<newline>.
.P
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'' (\c
.BR / ,
.BR ? ,
.BR : ,
and
.BR ! ).
When a line-oriented command is executed, 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
.BR !
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
<newline>,
a non-\c
<control>\(hyV-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.
.P
If any command is executed that overwrites a portion of the screen
other than the last line of the screen (for example, the
.IR ex
.BR suspend
or
.BR !
commands), other than the
.IR ex
.BR shell
command, the user shall be prompted for a character before the screen
is refreshed and the edit session continued.
.P
<tab>
characters shall take up the number of columns on the screen set by the
.BR tabstop
edit option (see
.IR 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.
.P
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.
.P
In open mode, if the current line is not already displayed, then it
shall be displayed.
.P
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
.BR window
edit option shall be displayed (unless the current line cannot be
completely displayed in the number of display lines specified by the
.BR 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.
.P
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
display 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
.BR '@' 
character.
.P
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
.BR '@' 
character (plus the terminating
<newline>),
and the
<control>\(hyR
command shall cause the editor to update the screen to correctly
represent the edit buffer.
.P
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.
.P
The display cursor column in the display is based on the value of the
current column, as follows, with each rule applied in turn:
.IP " 1." 4
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-\c
<newline>
in the current line; otherwise, the display cursor column shall be set
to the current column.
.IP " 2." 4
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:
.RS 4 
.IP " a." 4
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.
.IP " b." 4
Otherwise, the display cursor column shall be adjusted to the last
display line column in which any portion of that character is
displayed.
.RE
.P
The current column shall not be changed by these adjustments to the
display cursor column.
.P
If an error occurs during the parsing or execution of a
.IR vi
command:
.IP " *" 4
The terminal shall be alerted. Execution of the
.IR vi
command shall stop, and the cursor (for example, the current line and
column) shall not be further modified.
.IP " *" 4
Unless otherwise specified by the following command sections, it is
unspecified whether an informational message shall be displayed.
.IP " *" 4
Any partially entered
.IR vi
command shall be discarded.
.IP " *" 4
If the
.IR vi
command resulted from a
.BR map
expansion, all characters from that
.BR map
expansion shall be discarded, except as otherwise specified by the
.BR map
command (see
.IR ed ).
.IP " *" 4
If the
.IR vi
command resulted from the execution of a buffer, no further commands
caused by the execution of the buffer shall be executed.
.SS "Page Backwards"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-B
.fi \fR
.P
.RE
.RE
.P
If in open mode, the
<control>\(hyB
command shall behave identically to the
.BR z
command. Otherwise, if the current line is the first line of the edit
buffer, it shall be an error.
.P
If the
.BR window
edit option is less than 3, display a screen where the last line of the
display shall be some portion of:
.sp
.RS 4
.nf
\fB
(\fIcurrent first line\fR) \(mi1
.fi \fR
.P
.RE
.P
otherwise, display a screen where the first line of the display shall
be some portion of:
.sp
.RS 4
.nf
\fB
(\fIcurrent first line\fR) \(mi \fIcount\fR x ((window edit option) \(mi2)
.fi \fR
.P
.RE
.P
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.
.P
.IR "Current line" :
If no lines from the previous display remain on the screen, set to the
last line of the display; otherwise, set to (\c
.IR line
\(mi the number of new lines displayed on this screen).
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Scroll Forward"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-D
.fi \fR
.P
.RE
.RE
.P
If the current line is the last line of the edit buffer, it shall be an
error.
.P
If no
.IR count
is specified,
.IR count
shall default to the
.IR count
associated with the previous
<control>\(hyD
or
<control>\(hyU
command. If there was no previous
<control>\(hyD
or
<control>\(hyU
command,
.IR count
shall default to the value of the
.BR scroll
edit option.
.P
If in open mode, write lines starting with the line after the current
line, until
.IR count
lines or the last line of the file have been written.
.P
.IR "Current line" :
If the current line +
.IR 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 +
.IR count .
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Scroll Forward by Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-E
.fi \fR
.P
.RE
.RE
.P
Display the line count lines after the last line currently displayed.
.P
If the last line of the edit buffer is displayed, it shall be an error.
If there is no line
.IR 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.
.P
.IR "Current line" :
Unchanged if the previous current character is displayed; otherwise,
set to the first line displayed.
.P
.IR "Current column" :
Unchanged.
.SS "Page Forward"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-F
.fi \fR
.P
.RE
.RE
.P
If in open mode, the
<control>\(hyF
command shall behave identically to the
.BR z
command. Otherwise, if the current line is the last line of the edit
buffer, it shall be an error.
.P
If the
.BR window
edit option is less than 3, display a screen where the first line of
the display shall be some portion of:
.sp
.RS 4
.nf
\fB
(\fIcurrent last line\fR) +1
.fi \fR
.P
.RE
.P
otherwise, display a screen where the first line of the display shall
be some portion of:
.sp
.RS 4
.nf
\fB
(\fIcurrent first line\fR) + \fIcount\fR x ((window edit option) \(mi2)
.fi \fR
.P
.RE
.P
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.
.P
.IR "Current line" :
If no lines from the previous display remain on the screen, set to the
first line of the display; otherwise, set to (\c
.IR line
+ the number of new lines displayed on this screen).
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Display Information"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-G
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR ex
.BR file
command.
.SS "Move Cursor Backwards"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-H
.br
\fB[\fIcount\fB]\fR h
.br
the current \fIerase\fP character (see stty)
.fi \fR
.P
.RE
.RE
.P
If there are no characters before the current character on the current
line, it shall be an error. If there are less than
.IR count
previous characters on the current line,
.IR count
shall be adjusted to the number of previous characters on the line.
.P
If used as a motion command:
.IP " 1." 4
The text region shall be from the character before the starting cursor
up to and including the
.IR count th
character before the starting cursor.
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to (\c
.IR column
\(mi the number of columns occupied by
.IR count
characters ending with the previous current column).
.SS "Move Down"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <newline>
.br
\fB[\fIcount\fB]\fR <control>-J
.br
\fB[\fIcount\fB]\fR <control>-M
.br
\fB[\fIcount\fB]\fR <control>-N
.br
\fB[\fIcount\fB]\fR j
.br
\fB[\fIcount\fB]\fR <carriage-return>
.br
\fB[\fIcount\fB]\fR +
.fi \fR
.P
.RE
.RE
.P
If there are less than
.IR count
lines after the current line in the edit buffer, it shall be an error.
.P
If used as a motion command:
.IP " 1." 4
The text region shall include the starting line and the next
.IR count
\(mi 1 lines.
.IP " 2." 4
Any text copied to a buffer shall be in line mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to
.IR "current line" +
.IR count .
.P
.IR "Current column" :
Set to non-\c
<blank>
for the
<carriage-return>,
<control>\(hyM,
and
.BR +
commands; otherwise, unchanged.
.SS "Clear and Redisplay"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-L
.fi \fR
.P
.RE
.RE
.P
If in open mode, clear the screen and redisplay the current line.
Otherwise, clear and redisplay the screen.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Unchanged.
.SS "Move Up"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-P
.br
\fB[\fIcount\fB]\fR k
.br
\fB[\fIcount\fB]\fR \(mi
.fi \fR
.P
.RE
.RE
.P
If there are less than
.IR count
lines before the current line in the edit buffer, it shall be an
error.
.P
If used as a motion command:
.IP " 1." 4
The text region shall include the starting line and the previous
.IR count
lines.
.IP " 2." 4
Any text copied to a buffer shall be in line mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to
.IR "current line"
\(mi
.IR count .
.P
.IR "Current column" :
Set to non-\c
<blank>
for the
.BR \(mi
command; otherwise, unchanged.
.SS "Redraw Screen"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-R
.fi \fR
.P
.RE
.RE
.P
If any lines have been deleted from the display screen and flagged as
deleted on the terminal using the
.BR @
convention (see the beginning of the EXTENDED DESCRIPTION section),
they shall be redisplayed to match the contents of the edit buffer.
.P
It is unspecified whether lines flagged with
.BR @
because they do not fit on the terminal display shall be affected.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Unchanged.
.SS "Scroll Backward"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-U
.fi \fR
.P
.RE
.RE
.P
If the current line is the first line of the edit buffer, it shall be
an error.
.P
If no
.IR count
is specified,
.IR count
shall default to the
.IR count
associated with the previous
<control>\(hyD
or
<control>\(hyU
command. If there was no previous
<control>\(hyD
or
<control>\(hyU
command,
.IR count
shall default to the value of the
.BR scroll
edit option.
.P
.IR "Current line" :
If
.IR count
is greater than the current line, set to 1; otherwise, set to the
current line \(mi
.IR count .
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Scroll Backward by Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <control>-Y
.fi \fR
.P
.RE
.RE
.P
Display the line
.IR count
lines before the first line currently displayed.
.P
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.
.P
.IR "Current line" :
Unchanged if the previous current character is displayed; otherwise,
set to the first line displayed.
.P
.IR "Current column" :
Unchanged.
.SS "Edit the Alternate File"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-^
.fi \fR
.P
.RE
.RE
This command shall be equivalent to the
.IR ex
.BR edit
command, with the alternate pathname as its argument.
.SS "Terminate Command or Input Mode"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<ESC>
.fi \fR
.P
.RE
.RE
.P
If a partial
.IR vi
command (as defined by at least one, non-\c
.IR count
character) has been entered, discard the
.IR count
and the command character(s).
.P
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.
.P
Otherwise, it shall be an error.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Unchanged.
.SS "Search for tagstring"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-]
.fi \fR
.P
.RE
.RE
.P
If the current character is not a word or
<blank>,
it shall be an error.
.P
This command shall be equivalent to the
.IR ex
.BR tag
command, with the argument to that command defined as follows.
.P
If the current character is a
<blank>:
.IP " 1." 4
Skip all
<blank>
characters after the cursor up to the end of the line.
.IP " 2." 4
If the end of the line is reached, it shall be an error.
.P
Then, the argument to the
.IR ex
.BR tag
command shall be the current character and all subsequent characters,
up to the first non-word character or the end of the line.
.SS "Move Cursor Forward"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR <space>
.br
\fB[\fIcount\fB]\fR l\fR  (ell)\fR
.fi \fR
.P
.RE
.RE
.P
If there are less than
.IR count
non-\c
<newline>
characters after the cursor on the current line,
.IR count
shall be adjusted to the number of non-\c
<newline>
characters after the cursor on the line.
.P
If used as a motion command:
.IP " 1." 4
If the current or
.IR count th
character after the cursor is the last non-\c
<newline>
in the line, the text region shall be comprised of the current
character up to and including the last non-\c
<newline>
in the line. Otherwise, the text region shall be from the current
character up to, but not including, the
.IR count th
character after the cursor.
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
If there are no non-\c
<newline>
characters after the current character on the current line, it shall be
an error.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to the last column that displays any portion of the
.IR count th
character after the current character.
.SS "Replace Text with Results from Shell Command"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR ! \fImotion shell-commands\fR <newline>
.fi \fR
.P
.RE
.RE
.P
If the motion command is the
.BR !
command repeated:
.IP " 1." 4
If the edit buffer is empty and no
.IR count
was supplied, the command shall be the equivalent of the
.IR ex
.BR :read
.BR !
command, with the text input, and no text shall be copied to any
buffer.
.IP " 2." 4
Otherwise:
.RS 4 
.IP " a." 4
If there are less than
.IR count
\(mi1 lines after the current line in the edit buffer, it shall be an
error.
.IP " b." 4
The text region shall be from the current line up to and including the
next
.IR count
\(mi1 lines.
.RE
.P
Otherwise, the text region shall be the lines in which any character of
the text region specified by the motion command appear.
.P
Any text copied to a buffer shall be in line mode.
.P
This command shall be equivalent to the
.IR ex
.BR !
command for the specified lines.
.SS "Move Cursor to End-of-Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR $
.fi \fR
.P
.RE
.RE
.P
It shall be an error if there are less than (\c
.IR count
\(mi1) lines after the current line in the edit buffer.
.P
If used as a motion command:
.IP " 1." 4
If
.IR count
is 1:
.RS 4 
.IP " a." 4
It shall be an error if the line is empty.
.IP " b." 4
Otherwise, the text region shall consist of all characters from the
starting cursor to the last non-\c
<newline>
in the line, inclusive, and any text copied to a buffer shall be in
character mode.
.RE
.IP " 2." 4
Otherwise, if the starting cursor position is at or before the first
non-\c
<blank>
in the line, the text region shall consist of the current and the next
.IR count
\(mi1 lines, and any text saved to a buffer shall be in line mode.
.IP " 3." 4
Otherwise, the text region shall consist of all characters from the
starting cursor to the last non-\c
<newline>
in the line that is
.IR count
\(mi1 lines forward from the current line, and any text copied to a
buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the
.IR "current line"
+
.IR count \(mi1.
.P
.IR "Current column" :
The current column is set to the last display line column of the last
non-\c
<newline>
in the line, or column position 1 if the line is empty.
.P
The current column shall be adjusted to be on the last display line
column of the last non-\c
<newline>
of the current line as subsequent commands change the current line,
until a command changes the current column.
.SS "Move to Matching Character"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
%
.fi \fR
.P
.RE
.RE
.P
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.
.P
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.
.P
Matching shall be determined as follows, for an open parenthesis:
.IP " 1." 4
Set a counter to 1.
.IP " 2." 4
Search forwards until a parenthesis is found or the end of the edit
buffer is reached.
.IP " 3." 4
If the end of the edit buffer is reached, it shall be an error.
.IP " 4." 4
If an open parenthesis is found, increment the counter by 1.
.IP " 5." 4
If a close parenthesis is found, decrement the counter by 1.
.IP " 6." 4
If the counter is zero, the current character is the matching
character.
.P
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.
.P
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.
.P
If used as a motion command:
.IP " 1." 4
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-\c
<blank>
non-\c
<newline>
in the starting line, and the matching cursor position was at or after
the last non-\c
<blank>
non-\c
<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.
.IP " 2." 4
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-\c
<blank>
non-\c
<newline>
in the starting line, and the matching cursor position was at or before
the first non-\c
<blank>
non-\c
<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.
.IP " 3." 4
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.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the line where the matching character is located.
.P
.IR "Current column" :
Set to the last column where any portion of the matching character is
displayed.
.SS "Repeat Substitution"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
&
.fi \fR
.P
.RE
.RE
.P
Repeat the previous substitution command. This command shall be
equivalent to the
.IR ex
.BR &
command with the current line as its addresses, and without
.IR options ,
.IR count ,
or
.IR flags .
.SS "Return to Previous Context at Beginning of Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\&' \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
It shall be an error if there is no line in the edit buffer marked by
.IR character .
.P
If used as a motion command:
.IP " 1." 4
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.
.IP " 2." 4
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.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the line referenced by the mark.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Return to Previous Context"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\&` \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
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-\c
<blank>.
.P
If used as a motion command:
.IP " 1." 4
It shall be an error if the marked cursor references the same character
in the edit buffer as the starting cursor.
.IP " 2." 4
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.
.IP " 3." 4
If the starting line is empty or the starting cursor is at or before
the first non-\c
<blank>
non-\c
<newline>
of the starting line, and the marked cursor line is empty or the marked
cursor references the first character 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.
.IP " 4." 4
Otherwise, if the marked cursor line is empty or the marked cursor
references a character at or before the first non-\c
<blank>
non-\c
<newline>
of the marked cursor line, the region of text shall be from the
starting cursor to the last non-\c
<newline>
of the line before the marked cursor line, inclusive, and any text
copied to a buffer shall be in character mode.
.IP " 5." 4
Otherwise, the region of text shall be from the starting cursor
(inclusive), to the marked cursor (exclusive), and any text copied to a
buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the line referenced by the mark.
.P
.IR "Current column" :
Set to the last column in which any portion of the character referenced
by the mark is displayed.
.SS "Return to Previous Section"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR [[
.fi \fR
.P
.RE
.RE
.P
Move the cursor backward through the edit buffer to the first character
of the previous section boundary,
.IR count
times.
.P
If used as a motion command:
.IP " 1." 4
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
.IR count th
next boundary starts, and any text copied to a buffer shall be in line
mode.
.IP " 2." 4
If the boundary was the last line of the edit buffer or the last non-\c
<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.
.IP " 3." 4
Otherwise, the text region shall consist of the starting character up
to but not including the first character in the
.IR count th
next boundary, and any text copied to a buffer shall be in character
mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the line where the
.IR count th
next boundary in the edit buffer starts.
.P
.IR "Current column" :
Set to the last column in which any portion of the first character of
the
.IR count th
next boundary is displayed, or column position 1 if the line is empty.
.SS "Move to Next Section"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR ]]
.fi \fR
.P
.RE
.RE
.P
Move the cursor forward through the edit buffer to the first character
of the next section boundary,
.IR count
times.
.P
If used as a motion command:
.IP " 1." 4
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
.IR count th
previous boundary starts, and any text copied to a buffer shall be in
line mode.
.IP " 2." 4
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.
.IP " 3." 4
Otherwise, the text region shall consist of the first character in the
.IR count th
previous section boundary up to but not including the starting
character, and any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the line where the
.IR count th
previous boundary in the edit buffer starts.
.P
.IR "Current column" :
Set to the last column in which any portion of the first character of
the
.IR count th
previous boundary is displayed, or column position 1 if the line is
empty.
.SS "Move to First Non-<blank> Position on Current Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\&^
.fi \fR
.P
.RE
.RE
If used as a motion command:
.IP " 1." 4
If the line has no non-\c
<blank>
non-\c
<newline>
characters, or if the cursor is at the first non-\c
<blank>
non-\c
<newline>
of the line, it shall be an error.
.IP " 2." 4
If the cursor is before the first non-\c
<blank>
non-\c
<newline>
of the line, the text region shall be comprised of the current
character, up to, but not including, the first non-\c
<blank>
non-\c
<newline>
of the line.
.IP " 3." 4
If the cursor is after the first non-\c
<blank>
non-\c
<newline>
of the line, the text region shall be from the character before the
starting cursor up to and including the first non-\c
<blank>
non-\c
<newline>
of the line.
.IP " 4." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Current and Line Above"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR _
.fi \fR
.P
.RE
.RE
.P
If there are less than
.IR count
\(mi1 lines after the current line in the edit buffer, it shall be an
error.
.P
If used as a motion command:
.IP " 1." 4
If
.IR count
is less than 2, the text region shall be the current line.
.IP " 2." 4
Otherwise, the text region shall include the starting line and the next
.IR count
\(mi1 lines.
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to current line +
.IR count
\(mi1.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Move Back to Beginning of Sentence"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR (
.fi \fR
.P
.RE
.RE
.P
Move backward to the beginning of a sentence. This command shall be
equivalent to the
.BR [[
command, with the exception that sentence boundaries shall be used
instead of section boundaries.
.SS "Move Forward to Beginning of Sentence"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR )
.fi \fR
.P
.RE
.RE
.P
Move forward to the beginning of a sentence. This command shall be
equivalent to the
.BR ]]
command, with the exception that sentence boundaries shall be used
instead of section boundaries.
.SS "Move Back to Preceding Paragraph"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR {
.fi \fR
.P
.RE
.RE
.P
Move back to the beginning of the preceding paragraph. This command
shall be equivalent to the
.BR [[
command, with the exception that paragraph boundaries shall be used
instead of section boundaries.
.SS "Move Forward to Next Paragraph"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR }
.fi \fR
.P
.RE
.RE
.P
Move forward to the beginning of the next paragraph. This command
shall be equivalent to the
.BR ]]
command, with the exception that paragraph boundaries shall be used
instead of section boundaries.
.SS "Move to Specific Column Position"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR |
.fi \fR
.P
.RE
.RE
.P
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\(mibased, number of columns.
.P
If there are less than
.IR count
columns in which characters from the current line are displayed on the
screen,
.IR count
shall be adjusted to be the last column in which any portion of the
line is displayed on the screen.
.P
If used as a motion command:
.IP " 1." 4
If the line is empty, or the cursor character is the same as the
character on the
.IR count th
column of the line, it shall be an error.
.IP " 2." 4
If the cursor is before the
.IR count th
column of the line, the text region shall be comprised of the current
character, up to but not including the character on the
.IR count th
column of the line.
.IP " 3." 4
If the cursor is after the
.IR count th
column of the line, the text region shall be from the character before
the starting cursor up to and including the character on the
.IR count th
column of the line.
.IP " 4." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to the last column in which any portion of the character that is
displayed in the
.IR count
column of the line is displayed.
.SS "Reverse Find Character"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR ,
.fi \fR
.P
.RE
.RE
.P
If the last
.BR F ,
.BR f ,
.BR T ,
or
.BR t
command was
.BR F ,
.BR f ,
.BR T ,
or
.BR t ,
this command shall be equivalent to an
.BR f ,
.BR F ,
.BR t ,
or
.BR T
command, respectively, with the specified
.IR count
and the same search character.
.P
If there was no previous
.BR F ,
.BR f ,
.BR T ,
or
.BR t
command, it shall be an error.
.SS "Repeat"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR .
.fi \fR
.P
.RE
.RE
.P
Repeat the last
.BR ! ,
.BR < ,
.BR > ,
.BR A ,
.BR C ,
.BR D ,
.BR I ,
.BR J ,
.BR O ,
.BR P ,
.BR R ,
.BR S ,
.BR X ,
.BR Y ,
.BR a ,
.BR c ,
.BR d ,
.BR i ,
.BR o ,
.BR p ,
.BR r ,
.BR s ,
.BR x ,
.BR y ,
or
.BR ~
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.
.P
Repeated commands with associated motion commands shall repeat the
motion command as well; however, any specified
.IR count
shall replace the
.IR count (s)
that were originally specified to the repeated command or its
associated motion command.
.P
If the motion component of the repeated command is
.BR f ,
.BR F ,
.BR t ,
or
.BR T ,
the repeated command shall not set the remembered search character for
the
.BR ;
and
.BR ,
commands.
.P
If the repeated command is
.BR p
or
.BR 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.
.P
If the repeated character is a text input command, the input text
associated with that command is repeated literally:
.IP " *" 4
Input characters are neither macro or abbreviation-expanded.
.IP " *" 4
Input characters are not interpreted in any special way with the
exception that
<newline>,
<carriage-return>,
and
<control>\(hyT
behave as described in
.IR "Input Mode Commands in vi".
.P
.IR "Current line" :
Set as described for the repeated command.
.P
.IR "Current column" :
Set as described for the repeated command.
.SS "Find Regular Expression"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
/
.fi \fR
.P
.RE
.RE
.P
If the input line contains no non-\c
<newline>
characters, it shall be equivalent to a line containing only the
last regular expression encountered. The enhanced regular expressions
supported by
.IR vi
are described in
.IR "Regular Expressions in ex".
.P
Otherwise, the line shall be interpreted as one or more regular
expressions, optionally followed by an address offset or a
.IR vi
.BR z
command.
.P
If the regular expression is not the last regular expression on the
line, or if a line offset or
.BR z
command is specified, the regular expression shall be terminated by an
unescaped
.BR '/' 
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>
characters, a
<semicolon>,
zero or more
<blank>
characters, and a leading
.BR '/' 
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.
.P
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
.BR 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.
.P
An optional address offset (see
.IR "Addressing in ex")
can be specified after the last regular expression by including a
trailing
.BR '/' 
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>
characters.
.P
If not used as a motion command, an optional
.BR z
command (see
.IR "Redraw Window")
can be specified after the last regular expression by including a
trailing
.BR '/' 
character after the regular expression, zero or more
<blank>
characters, a
.BR 'z' ,
zero or more
<blank>
characters, an optional new
.BR window
edit option value, zero or more
<blank>
characters, and a location character. The effect shall be as if the
.BR z
command was executed after the
.BR /
command. It shall be an error to follow the
.BR z
command with any other characters than
<blank>
characters.
.P
The remembered search direction shall be set to forward.
.P
If used as a motion command:
.IP " 1." 4
It shall be an error if the last match references the same character in
the edit buffer as the starting cursor.
.IP " 2." 4
If any address offset is specified, the last match shall be adjusted by
the specified offset as described previously.
.IP " 3." 4
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.
.IP " 4." 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.
.IP " 5." 4
Otherwise, if the starting line is empty or the starting cursor is at
or before the first non-\c
<blank>
non-\c
<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.
.IP " 6." 4
Otherwise, if the last match line is empty or the last match begins at
a character at or before the first non-\c
<blank>
non-\c
<newline>
of the last match line, the region of text shall be from the current
cursor to the last non-\c
<newline>
of the line before the last match line, inclusive, and any text copied
to a buffer shall be in character mode.
.IP " 7." 4
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.
.P
If not used as a motion command:
.P
.IR "Current line" :
If a match is found, set to the last matched line plus the address
offset, if any; otherwise, unchanged.
.P
.IR "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.
.SS "Move to First Character in Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
0  \fR(zero)\fR
.fi \fR
.P
.RE
.RE
.P
Move to the first character on the current line. The character
.BR '0' 
shall not be interpreted as a command if it is immediately preceded by
a digit.
.P
If used as a motion command:
.IP " 1." 4
If the cursor character is the first character in the line, it shall be
an error.
.IP " 2." 4
The text region shall be from the character before the cursor character
up to and including the first character in the line.
.IP " 3." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "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.
.SS "Execute an ex Command"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
:
.fi \fR
.P
.RE
.RE
.P
Execute one or more
.IR ex
commands.
.P
If any portion of the screen other than the last line of the screen was
overwritten by any
.IR ex
command (except
.BR shell ),
.IR 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.
.P
If the next character entered is a
.BR ':' ,
another
.IR ex
command shall be accepted and executed. Any other character shall cause
the screen to be refreshed and
.IR vi
shall return to command mode.
.P
.IR "Current line" :
As specified for the
.IR ex
command.
.P
.IR "Current column" :
As specified for the
.IR ex
command.
.SS "Repeat Find"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR ;
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the last
.BR F ,
.BR f ,
.BR T ,
or
.BR t
command, with the specified
.IR count ,
and with the same search character used for the last
.BR F ,
.BR f ,
.BR T ,
or
.BR t
command. If there was no previous
.BR F ,
.BR f ,
.BR T ,
or
.BR t
command, it shall be an error.
.SS "Shift Left"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR < \fImotion\fR
.fi \fR
.P
.RE
.RE
.P
If the motion command is the
.BR <
command repeated:
.IP " 1." 4
If there are less than
.IR count
\(mi1 lines after the current line in the edit buffer, it shall be an
error.
.IP " 2." 4
The text region shall be from the current line, up to and including the
next
.IR count
\(mi1 lines.
.P
Shift any line in the text region specified by the
.IR count
and motion command one shiftwidth (see the
.IR ex
.BR shiftwidth
option) toward the start of the line, as described by the
.IR ex
.BR <
command. The unshifted lines shall be copied to the unnamed buffer in
line mode.
.P
.IR "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.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Shift Right"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR > \fImotion\fR
.fi \fR
.P
.RE
.RE
.P
If the motion command is the
.BR >
command repeated:
.IP " 1." 4
If there are less than
.IR count
\(mi1 lines after the current line in the edit buffer, it shall be an
error.
.IP " 2." 4
The text region shall be from the current line, up to and including the
next
.IR count
\(mi1 lines.
.P
Shift any line with characters in the text region specified by the
.IR count
and motion command one shiftwidth (see the
.IR ex
.BR shiftwidth
option) away from the start of the line, as described by the
.IR ex
.BR >
command. The unshifted lines shall be copied into the unnamed buffer in
line mode.
.P
.IR "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.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Scan Backwards for Regular Expression"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
?
.fi \fR
.P
.RE
.RE
.P
Scan backwards; the
.BR ?
command shall be equivalent to the
.BR /
command (see
.IR "Find Regular Expression")
with the following exceptions:
.IP " 1." 4
The input prompt shall be a
.BR '?' .
.IP " 2." 4
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).
.IP " 3." 4
The search direction shall be from the cursor toward the beginning of
the edit buffer, and the
.BR wrapscan
edit option shall affect whether the search wraps to the end of the
edit buffer and continues.
.IP " 4." 4
The remembered search direction shall be set to backward.
.SS "Execute"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
@\fIbuffer\fR
.fi \fR
.P
.RE
.RE
.P
If the
.IR buffer
is specified as
.BR @ ,
the last buffer executed shall be used. If no previous buffer has been
executed, it shall be an error.
.P
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.
.P
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.
.P
If a
.IR count
is specified, behave as if that count were entered as user input before
the characters from the
.BR @
buffer were entered.
.P
.IR "Current line" :
As specified for the individual commands.
.P
.IR "Current column" :
As specified for the individual commands.
.SS "Reverse Case"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR ~
.fi \fR
.P
.RE
.RE
.P
Reverse the case of the current character and the next
.IR count
\(mi1 characters, such that lowercase characters that have uppercase
counterparts shall be changed to uppercase characters, and uppercase
characters that have lowercase counterparts shall be changed to
lowercase characters, as prescribed by the current locale. No other
characters shall be affected by this command.
.P
If there are less than
.IR count
\(mi1 characters after the cursor in the edit buffer,
.IR count
shall be adjusted to the number of characters after the cursor in the
edit buffer minus 1.
.P
For the purposes of this command, the next character after the last
non-\c
<newline>
on the line shall be the next character in the edit buffer.
.P
.IR "Current line" :
Set to the line including the (\c
.IR count \(mi1)th
character after the cursor.
.P
.IR "Current column" :
Set to the last column in which any portion of the (\c
.IR count \(mi1)th
character after the cursor is displayed.
.SS "Append"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR a
.fi \fR
.P
.RE
.RE
.P
Enter text input mode after the current cursor position. No characters
already in the edit buffer shall be affected by this command. A
.IR count
shall cause the input text to be appended
.IR count
\(mi1 more times to the end of the input.
.P
.IR "Current line/column" :
As specified for the text input commands (see
.IR "Input Mode Commands in vi").
.SS "Append at End-of-Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR A
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR vi
command:
.sp
.RS 4
.nf
\fB
\fR$\fB [ \fIcount \fB]\fR a
.fi \fR
.P
.RE
.P
(see
.IR "Append").
.SS "Move Backward to Preceding Word"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR b
.fi \fR
.P
.RE
.RE
.P
With the exception that words are used as the delimiter instead of
bigwords, this command shall be equivalent to the
.BR B
command.
.SS "Move Backward to Preceding Bigword"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR B
.fi \fR
.P
.RE
.RE
.P
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
.IR count
bigwords begin between the cursor and the start of the edit buffer,
.IR count
shall be adjusted to the number of bigword beginnings between the
cursor and the start of the edit buffer.
.P
If used as a motion command:
.IP " 1." 4
The text region shall be from the first character of the
.IR count th
previous bigword beginning up to but not including the cursor
character.
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the line containing the
.IR "current column" .
.P
.IR "Current column" :
Set to the last column upon which any part of the first character of
the
.IR count th
previous bigword is displayed.
.SS "Change"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR c \fImotion\fR
.fi \fR
.P
.RE
.RE
.P
If the motion command is the
.BR c
command repeated:
.IP " 1." 4
The buffer text shall be in line mode.
.IP " 2." 4
If there are less than
.IR count
\(mi1 lines after the current line in the edit buffer, it shall be an
error.
.IP " 3." 4
The text region shall be from the current line up to and including the
next
.IR count
\(mi1 lines.
.P
Otherwise, the buffer text mode and text region shall be as specified
by the motion command.
.P
The replaced text shall be copied into
.IR 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.
.P
If the buffer text is in line mode:
.IP " 1." 4
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.
.IP " 2." 4
If the
.BR autoindent
edit option is set,
.BR autoindent
characters equal to the
.BR autoindent
characters on the first line deleted shall be inserted as if entered by
the user.
.P
Otherwise, if characters from more than one line are in the region of
text:
.IP " 1." 4
The text shall be deleted.
.IP " 2." 4
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.
.IP " 3." 4
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.
.br
.P
Otherwise:
.IP " 1." 4
If the glyph for
.BR '$' 
is smaller than the region, the end of the region shall be marked with
a
.BR '$' .
.IP " 2." 4
The editor shall enter text input mode, overwriting the region of
text.
.P
.IR "Current line/column" :
As specified for the text input commands (see
.IR "Input Mode Commands in vi").
.SS "Change to End-of-Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR C
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR vi
command:
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR c$
.fi \fR
.P
.RE
.P
See the
.BR c
command.
.SS "Delete"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR d \fImotion\fR
.fi \fR
.P
.RE
.RE
.P
If the motion command is the
.BR d
command repeated:
.IP " 1." 4
The buffer text shall be in line mode.
.IP " 2." 4
If there are less than
.IR count
\(mi1 lines after the current line in the edit buffer, it shall be an
error.
.IP " 3." 4
The text region shall be from the current line up to and including the
next
.IR count
\(mi1 lines.
.P
Otherwise, the buffer text mode and text region shall be as specified
by the motion command.
.P
If in open mode, and the current line is deleted, and the line remains
on the display, an
.BR '@' 
character shall be displayed as the first glyph of that line.
.P
Delete the region of text into
.IR 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.
.P
.IR "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.
.P
.IR "Current column" :
.IP " 1." 4
If the line is empty, set to column position 1.
.IP " 2." 4
Otherwise, if the buffer text is in line mode or the motion was from
the cursor toward the end of the edit buffer:
.RS 4 
.IP " a." 4
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.
.IP " b." 4
Otherwise, set to the last column in which any portion of any character
in the line is displayed.
.RE
.IP " 3." 4
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.
.IP " 4." 4
Otherwise, set to the last column in which any portion of any character
in the line is displayed.
.SS "Delete to End-of-Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB]\fR D
.fi \fR
.P
.RE
.RE
.P
Delete the text from the current position to the end of the current
line; equivalent to the
.IR vi
command:
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB]\fR d$
.fi \fR
.P
.RE
.SS "Move to End-of-Word"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR e
.fi \fR
.P
.RE
.RE
.P
With the exception that words are used instead of bigwords as the
delimiter, this command shall be equivalent to the
.BR E
command.
.SS "Move to End-of-Bigword"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR E
.fi \fR
.P
.RE
.RE
.P
If the edit buffer is empty it shall be an error. If less than
.IR count
bigwords end between the cursor and the end of the edit buffer,
.IR count
shall be adjusted to the number of bigword endings between the cursor
and the end of the edit buffer.
.P
If used as a motion command:
.IP " 1." 4
The text region shall be from the last character of the
.IR count th
next bigword up to and including the cursor character.
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to the line containing the current column.
.P
.IR "Current column" :
Set to the last column upon which any part of the last character of the
.IR count th
next bigword is displayed.
.SS "Find Character in Current Line (Forward)"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR f \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
It shall be an error if
.IR count
occurrences of the character do not occur after the cursor in the
line.
.P
If used as a motion command:
.IP " 1." 4
The text range shall be from the cursor character up to and including
the
.IR count th
occurrence of the specified character after the cursor.
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to the last column in which any portion of the
.IR count th
occurrence of the specified character after the cursor appears in the
line.
.SS "Find Character in Current Line (Reverse)"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR F \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
It shall be an error if
.IR count
occurrences of the character do not occur before the cursor in the
line.
.P
If used as a motion command:
.IP " 1." 4
The text region shall be from the
.IR count th
occurrence of the specified character before the cursor, up to, but not
including the cursor character.
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to the last column in which any portion of the
.IR count th
occurrence of the specified character before the cursor appears in the
line.
.SS "Move to Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR G
.fi \fR
.P
.RE
.RE
.P
If
.IR count
is not specified, it shall default to the last line of the edit buffer.
If
.IR count
is greater than the last line of the edit buffer, it shall be an
error.
.P
If used as a motion command:
.IP " 1." 4
The text region shall be from the cursor line up to and including the
specified line.
.IP " 2." 4
Any text copied to a buffer shall be in line mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Set to
.IR count
if
.IR count
is specified; otherwise, the last line.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Move to Top of Screen"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR H
.fi \fR
.P
.RE
.RE
.P
If the beginning of the line
.IR count
greater than the first line of which any portion appears on the display
does not exist, it shall be an error.
.P
If used as a motion command:
.IP " 1." 4
If in open mode, the text region shall be the current line.
.IP " 2." 4
Otherwise, the text region shall be from the starting line up to and
including (the first line of the display +
.IR count
\(mi1).
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.P
If not used as a motion command:
.P
If in open mode, this command shall set the current column to non-\c
<blank>
and do nothing else.
.P
Otherwise, it shall set the current line and current column as
follows.
.P
.IR "Current line" :
Set to (the first line of the display +
.IR count
\(mi1).
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Insert Before Cursor"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR i
.fi \fR
.P
.RE
.RE
.P
Enter text input mode before the current cursor position. No characters
already in the edit buffer shall be affected by this command. A
.IR count
shall cause the input text to be appended
.IR count
\(mi1 more times to the end of the input.
.P
.IR "Current line/column" :
As specified for the text input commands (see
.IR "Input Mode Commands in vi").
.SS "Insert at Beginning of Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR I
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR vi
command ^[\c
.IR count ]\c
.BR i .
.SS "Join"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR J
.fi \fR
.P
.RE
.RE
.P
If the current line is the last line in the edit buffer, it shall be an
error.
.P
This command shall be equivalent to the
.IR ex
.BR join
command with no addresses, and an
.IR ex
command
.IR count
value of 1 if
.IR count
was not specified or if a
.IR count
of 1 was specified, and an
.IR ex
command
.IR count
value of
.IR count
\(mi1 for any other value of
.IR count ,
except that the current line and column shall be set as follows.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
The last column in which any portion of the character following the
last character in the initial line is displayed, or the last non-\c
<newline>
in the line if no characters were appended.
.SS "Move to Bottom of Screen"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR L
.fi \fR
.P
.RE
.RE
.P
If the beginning of the line
.IR count
less than the last line of which any portion appears on the display
does not exist, it shall be an error.
.P
If used as a motion command:
.IP " 1." 4
If in open mode, the text region shall be the current line.
.IP " 2." 4
Otherwise, the text region shall include all lines from the starting
cursor line to (the last line of the display \(mi(\c
.IR count
\(mi1)).
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.P
If not used as a motion command:
.IP " 1." 4
If in open mode, this command shall set the current column to non-\c
<blank>
and do nothing else.
.IP " 2." 4
Otherwise, it shall set the current line and current column as follows.
.P
.IR "Current line" :
Set to (the last line of the display \(mi(\c
.IR count
\(mi1)).
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Mark Position"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
m \fIletter\fR
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR ex
.BR mark
command with the specified character as an argument.
.SS "Move to Middle of Screen"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
M
.fi \fR
.P
.RE
.RE
.P
The middle line of the display shall be calculated as follows:
.sp
.RS 4
.nf
\fB
(the top line of the display) + (((number of lines displayed) +1) /2) \(mi1
.fi \fR
.P
.RE
.P
If used as a motion command:
.IP " 1." 4
If in open mode, the text region shall be the current line.
.IP " 2." 4
Otherwise, the text region shall include all lines from the starting
cursor line up to and including the middle line of the display.
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.P
If not used as a motion command:
.P
If in open mode, this command shall set the current column to non-\c
<blank>
and do nothing else.
.P
Otherwise, it shall set the current line and current column as
follows.
.P
.IR "Current line" :
Set to the middle line of the display.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Repeat Regular Expression Find (Forward)"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
n
.fi \fR
.P
.RE
.RE
.P
If the remembered search direction was forward, the
.BR n
command shall be equivalent to the
.IR vi
.BR /
command with no characters entered by the user. Otherwise, it shall be
equivalent to the
.IR vi
.BR ?
command with no characters entered by the user.
.P
If the
.BR n
command is used as a motion command for the
.BR !
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
.BR '!' 
character as the text input.
.SS "Repeat Regular Expression Find (Reverse)"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
N
.fi \fR
.P
.RE
.RE
.P
Scan for the next match of the last pattern given to
.BR /
or
.BR ? ,
but in the reverse direction; this is the reverse of
.BR n .
.P
If the remembered search direction was forward, the
.BR N
command shall be equivalent to the
.IR vi
.BR ?
command with no characters entered by the user. Otherwise, it shall be
equivalent to the
.IR vi
.BR /
command with no characters entered by the user. If the
.BR N
command is used as a motion command for the
.BR !
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
.BR !
character as the text input.
.SS "Insert Empty Line Below"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
o
.fi \fR
.P
.RE
.RE
.P
Enter text input mode in a new line appended after the current line. A
.IR count
shall cause the input text to be appended
.IR count
\(mi1 more times to the end of the already added text, each time
starting on a new, appended line.
.P
.IR "Current line/column" :
As specified for the text input commands (see
.IR "Input Mode Commands in vi").
.SS "Insert Empty Line Above"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
O
.fi \fR
.P
.RE
.RE
.P
Enter text input mode in a new line inserted before the current line. A
.IR count
shall cause the input text to be appended
.IR count
\(mi1 more times to the end of the already added text, each time
starting on a new, appended line.
.P
.IR "Current line/column" :
As specified for the text input commands (see
.IR "Input Mode Commands in vi").
.SS "Put from Buffer Following"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB]\fR p
.fi \fR
.P
.RE
.RE
.P
If no
.IR buffer
is specified, the unnamed buffer shall be used.
.P
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
.IR count
shall cause the buffer text to be appended
.IR count
\(mi1 more times to the end of the already added text, each time
starting on a new, appended line.
.P
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
.IR count
shall cause the buffer text to be appended
.IR count
\(mi1 more times to the end of the already added text, each time
starting after the last added character.
.P
.IR "Current line" :
If the buffer text is in line mode, set the line to line +1; otherwise,
unchanged.
.P
.IR "Current column" :
If the buffer text is in line mode:
.IP " 1." 4
If there is a non-\c
<blank>
in the first line of the buffer, set to the last column on which any
portion of the first non-\c
<blank>
in the line is displayed.
.IP " 2." 4
If there is no non-\c
<blank>
in the first line of the buffer, set to the last column on which any
portion of the last non-\c
<newline>
in the first line of the buffer is displayed.
.P
If the buffer text is in character mode:
.IP " 1." 4
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.
.IP " 2." 4
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.
.IP " 3." 4
Otherwise, set to the first column on which any portion of the first
character from the buffer is displayed.
.SS "Put from Buffer Before"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB]\fR P
.fi \fR
.P
.RE
.RE
.P
If no
.IR buffer
is specified, the unnamed buffer shall be used.
.P
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
.IR count
shall cause the buffer text to be appended
.IR count
\(mi1 more times to the end of the already added text, each time
starting on a new, appended line.
.P
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
.IR count
shall cause the buffer text to be appended
.IR count
\(mi1 more times to the end of the already added text, each time
starting after the last added character.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
If the buffer text is in line mode:
.IP " 1." 4
If there is a non-\c
<blank>
in the first line of the buffer, set to the last column on which any
portion of that character is displayed.
.IP " 2." 4
If there is no non-\c
<blank>
in the first line of the buffer, set to the last column on which any
portion of the last non-\c
<newline>
in the first line of the buffer is displayed.
.P
If the buffer text is in character mode:
.IP " 1." 4
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.
.IP " 2." 4
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.
.IP " 3." 4
Otherwise, set to the first column on which any portion of the first
character from the buffer is displayed.
.SS "Enter ex Mode"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
Q
.fi \fR
.P
.RE
.RE
.P
Leave visual or open mode and enter
.IR ex
command mode.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Unchanged.
.SS "Replace Character"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR r \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
Replace the
.IR count
characters at and after the cursor with the specified character. If
there are less than
.IR count
non-\c
<newline>
characters at and after the cursor on the line, it shall be an error.
.P
If character is
<control>\(hyV,
any next character other than the
<newline>
shall be stripped of any special meaning and used as a literal
character.
.P
If character is
<ESC>,
no replacement shall be made and the current line and current column
shall be unchanged.
.P
If character is
<carriage-return>
or
<newline>,
.IR count
new lines shall be appended to the current line. All but the last of
these lines shall be empty.
.IR 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
.BR autoindent
edit option is set, they shall be preceded by the same number of
.BR autoindent
characters found on the line from which the command was executed.
.P
.IR "Current line" :
Unchanged unless the replacement character is a
<carriage-return>
or
<newline>,
in which case it shall be set to line +
.IR count .
.P
.IR "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-\c
<blank>.
.SS "Replace Characters"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
R
.fi \fR
.P
.RE
.RE
.P
Enter text input mode at the current cursor position possibly
replacing text on the current line. A
.IR count
shall cause the input text to be appended
.IR count
\(mi1 more times to the end of the input.
.P
.IR "Current line/column" :
As specified for the text input commands (see
.IR "Input Mode Commands in vi").
.SS "Substitute Character"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR s
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR vi
command:
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR c<space>
.fi \fR
.P
.RE
.SS "Substitute Lines"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR S
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR vi
command:
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR c_
.fi \fR
.P
.RE
.SS "Move Cursor to Before Character (Forward)"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR t \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
It shall be an error if
.IR count
occurrences of the character do not occur after the cursor in the
line.
.P
If used as a motion command:
.IP " 1." 4
The text region shall be from the cursor up to but not including the
.IR count th
occurrence of the specified character after the cursor.
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to the last column in which any portion of the character before the
.IR count th
occurrence of the specified character after the cursor appears in the
line.
.SS "Move Cursor to After Character (Reverse)"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR T \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
It shall be an error if
.IR count
occurrences of the character do not occur before the cursor in the
line.
.P
If used as a motion command:
.IP " 1." 4
If the character before the cursor is the specified character, it shall
be an error.
.IP " 2." 4
The text region shall be from the character before the cursor up to but
not including the
.IR count th
occurrence of the specified character before the cursor.
.IP " 3." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to the last column in which any portion of the character after the
.IR count th
occurrence of the specified character before the cursor appears in the
line.
.SS "Undo"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
u
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR ex
.BR undo
command except that the current line and current column shall be set as
follows:
.P
.IR "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.
.P
.IR "Current column" :
If undoing an
.IR ex
command, set to the first non-\c
<blank>.
.P
Otherwise, if undoing a text input command:
.IP " 1." 4
If the command was a
.BR C ,
.BR c ,
.BR O ,
.BR o ,
.BR R ,
.BR S ,
or
.BR s
command, the current column shall be set to the value it held when the
text input command was entered.
.IP " 2." 4
Otherwise, set to the last column in which any portion of the first
character after the deleted text is displayed, or, if no non-\c
<newline>
characters follow the text deleted from this line, set to the last column
in which any portion of the last non-\c
<newline>
in the line is displayed, or 1 if the line is empty.
.P
Otherwise, if a single line was modified (that is, not added or
deleted) by the
.BR u
command:
.IP " 1." 4
If text was added or changed, set to the last column in which any
portion of the first character added or changed is displayed.
.IP " 2." 4
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-\c
<newline>
characters follow the deleted text, set to the last column in which any
portion of the last non-\c
<newline>
in the line is displayed, or 1 if the line is empty.
.P
Otherwise, set to non-\c
<blank>.
.SS "Undo Current Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
U
.fi \fR
.P
.RE
.RE
.P
Restore the current line to its state immediately before the most
recent time that it became the current line.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to the first column in the line in which any portion of the first
character in the line is displayed.
.SS "Move to Beginning of Word"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR w
.fi \fR
.P
.RE
.RE
.P
With the exception that words are used as the delimiter instead of
bigwords, this command shall be equivalent to the
.BR W
command.
.SS "Move to Beginning of Bigword"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR W
.fi \fR
.P
.RE
.RE
.P
If the edit buffer is empty, it shall be an error. If there are less
than
.IR count
bigwords between the cursor and the end of the edit buffer,
.IR count
shall be adjusted to move the cursor to the last bigword in the edit
buffer.
.P
If used as a motion command:
.IP " 1." 4
If the associated command is
.BR c ,
.IR 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.
.IP " 2." 4
If there are less than
.IR 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.
.IP " 3." 4
If there are
<blank>
characters or an end-of-line that precede the
.IR count th
bigword, and the associated command is
.BR c ,
the region of text shall be up to and including the last character
before the preceding
<blank>
characters or end-of-line.
.IP " 4." 4
If there are
<blank>
characters or an end-of-line that precede the bigword, and the associated
command is
.BR d
or
.BR y ,
the region of text shall be up to and including the last
<blank>
before the start of the bigword or end-of-line.
.IP " 5." 4
Any text copied to a buffer shall be in character mode.
.P
If not used as a motion command:
.IP " 1." 4
If the cursor is on the last character of the edit buffer, it shall be
an error.
.P
.IR "Current line" :
Set to the line containing the current column.
.P
.IR "Current column" :
Set to the last column in which any part of the first character of the
.IR count th
next bigword is displayed.
.SS "Delete Character at Cursor"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR x
.fi \fR
.P
.RE
.RE
.P
Delete the
.IR count
characters at and after the current character into
.IR buffer ,
if specified, and into the unnamed buffer.
.P
If the line is empty, it shall be an error. If there are less than
.IR count
non-\c
<newline>
characters at and after the cursor on the current line,
.IR count
shall be adjusted to the number of non-\c
<newline>
characters at and after the cursor.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
If the line is empty, set to column position 1. Otherwise, if there
were
.IR count
or less non-\c
<newline>
characters at and after the cursor on the current line, set to the last
column that displays any part of the last non-\c
<newline>
of the line. Otherwise, unchanged.
.SS "Delete Character Before Cursor"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR X
.fi \fR
.P
.RE
.RE
.P
Delete the
.IR count
characters before the current character into
.IR buffer ,
if specified, and into the unnamed buffer.
.P
If there are no characters before the current character on the current
line, it shall be an error. If there are less than
.IR count
previous characters on the current line,
.IR count
shall be adjusted to the number of previous characters on the line.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to (current column \(mi the width of the deleted characters).
.SS "Yank"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR y \fImotion\fR
.fi \fR
.P
.RE
.RE
.P
Copy (yank) the region of text into
.IR buffer ,
if specified, and into the unnamed buffer.
.P
If the motion command is the
.BR y
command repeated:
.IP " 1." 4
The buffer shall be in line mode.
.IP " 2." 4
If there are less than
.IR count
\(mi1 lines after the current line in the edit buffer, it shall be an
error.
.IP " 3." 4
The text region shall be from the current line up to and including the
next
.IR count
\(mi1 lines.
.P
Otherwise, the buffer text mode and text region shall be as specified
by the motion command.
.P
.IR "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.
.P
.IR "Current column" :
.IP " 1." 4
If the motion was from the current cursor position toward the end of
the edit buffer, unchanged.
.IP " 2." 4
Otherwise, if the current line is empty, set to column position 1.
.IP " 3." 4
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.
.SS "Yank Current Line"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR Y
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR vi
command:
.sp
.RS 4
.nf
\fB
\fB[\fIbuffer\fB][\fIcount\fB]\fR y_
.fi \fR
.P
.RE
.SS "Redraw Window"
.P
If in open mode, the
.BR z
command shall have the Synopsis:
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIcount\fB]\fR z
.fi \fR
.P
.RE
.RE
.P
If
.IR count
is not specified, it shall default to the
.BR window
edit option \(mi1. The
.BR z
command shall be equivalent to the
.IR ex
.BR z
command, with a type character of
.BR =
and a
.IR count
of
.IR count
\(mi2, except that the current line and current column shall be set as
follows, and the
.BR window
edit option shall not be affected. If the calculation for the
.IR count
argument would result in a negative number, the
.IR count
argument to the
.IR ex
.BR z
command shall be zero. A blank line shall be written after the last
line is written.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Unchanged.
.P
If not in open mode, the
.BR z
command shall have the following Synopsis:
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
\fB[\fIline\fB]\fR z \fB[\fIcount\fB] \fIcharacter\fR
.fi \fR
.P
.RE
.RE
.P
If
.IR line
is not specified, it shall default to the current line. If
.IR 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.
.P
If
.IR count
is specified, the value of the
.BR window
edit option shall be set to
.IR count
(as described in the
.IR ex
.BR window
command), and the screen shall be redrawn.
.P
.IR line
shall be placed as specified by the following characters:
.IP "<newline>,\ <carriage-return>" 6
.br
Place the beginning of the line on the first line of the display.
.IP "\fR.\fP" 6
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
.BR M
command.
.IP "\fR\(mi\fP" 6
Place an unspecified portion of the line on the last line of the
display.
.IP "\fR+\fP" 6
If
.IR line
was specified, equivalent to the
<newline>
case. If
.IR 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.
.IP "\fR^\fP" 6
If
.IR 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, display the first screen of the edit
buffer.
.RS 6 
.P
Otherwise, display a screen where the last line of the display shall
contain an unspecified portion of (current first line \(mi1). If this
calculation results in a line before the beginning of the edit buffer,
it shall be an error.
.RE
.br
.P
.IR "Current line" :
If
.IR line
and the
.BR '^' 
character were specified:
.IP " 1." 4
If the first screen was displayed as a result of the command attempting
to display lines before the beginning of the edit buffer: if the first
screen was already displayed, unchanged; otherwise, set to (current
first line \(mi1).
.IP " 2." 4
Otherwise, set to the last line of the display.
.P
If
.IR line
and the
.BR '\(pl' 
character were specified, set to the first line of the display.
.P
Otherwise, if
.IR line
was specified, set to
.IR line .
.P
Otherwise, unchanged.
.P
.IR "Current column" :
Set to non-\c
<blank>.
.SS "Exit"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
ZZ
.fi \fR
.P
.RE
.RE
.P
This command shall be equivalent to the
.IR ex
.BR xit
command with no addresses, trailing
.BR ! ,
or filename (see the
.IR ex
.BR xit
command).
.SS "Input Mode Commands in vi"
.P
In text input mode, the current line shall consist of zero or more of
the following categories, plus the terminating
<newline>:
.IP " 1." 4
Characters preceding the text input entry point
.RS 4 
.P
Characters in this category shall not be modified during text input
mode.
.RE
.IP " 2." 4
.BR autoindent
characters
.RS 4 
.P
.BR 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 command itself; for
example,
.BR O
or
.BR o
(see the
.IR ex
.BR autoindent
command), as if entered by the user.
.P
It shall be possible to erase
.BR autoindent
characters with the
<control>\(hyD
command; it is unspecified whether they can be erased by
<control>\(hyH,
<control>\(hyU,
and
<control>\(hyW
characters. Erasing any
.BR autoindent
character turns the glyph into erase-columns and deletes the character
from the edit buffer, but does not change its representation on the
screen.
.RE
.IP " 3." 4
Text input characters
.RS 4 
.P
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.
.P
Each text input character entered by the user (that does not have a
special meaning) shall be treated as follows:
.IP " a." 4
The text input character shall be appended to the last character in the
edit buffer from the first, second, or third categories.
.IP " b." 4
If there are no erase-columns on the screen, the text input command was
the
.BR R
command, and characters in the fifth category from the original line
follow the cursor, the next such character shall be deleted from the
edit buffer. If the
.BR slowopen
edit option is not set, the corresponding glyph on the screen shall
become erase-columns.
.IP " c." 4
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 overwritten,
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.)
.IP " d." 4
If additional display line columns are needed to display the text input
character:
.RS 4 
.IP " i." 5
If the
.BR slowopen
edit option is set, the text input characters shall be displayed on
subsequent display line columns, overwriting any characters displayed
in those columns.
.IP ii. 5
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.
.RE
.RE
.IP " 4." 4
Erase-columns
.RS 4 
.P
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.
.P
Erase-columns are initially the region of text specified by the
.BR c
command (see
.IR "Change");
however, erasing
.BR autoindent
or text input characters causes the glyphs of the erased characters to
be treated as erase-columns.
.RE
.IP " 5." 4
Characters following the text region for the
.BR c
command, or the text input entry point for all other commands
.RS 4 
.P
Characters in this category shall not be modified during text input
mode, except as specified in category 3.b. for the
.BR R
text input command, or as
<blank>
characters deleted when a
<newline>
or
<carriage-return>
is entered.
.RE
.P
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-\c
<newline>
characters on the current line shall be treated as erase-columns.
.P
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:
.IP " 1." 4
On the first column that displays any part of the first erase-column,
if one exists
.IP " 2." 4
Otherwise, if the
.BR 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
.IP " 3." 4
Otherwise, the first column that displays any part of the first
character in the fifth category, if one exists
.IP " 4." 4
Otherwise, the display line column after the last character in the
first, second, or third categories, if one exists
.IP " 5." 4
Otherwise, on column position 1
.P
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
.BR slowopen
edit option is not set, the current cursor character shall always be
updated.
.P
The following specifications are for command characters entered during
text input mode.
.SS "NUL"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
NUL
.fi \fR
.P
.RE
.RE
.P
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.
.SS "<control>-D"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-D
.fi \fR
.P
.RE
.RE
.P
The
<control>\(hyD
character shall have no special meaning when in text input
mode for a line-oriented command (see
.IR "Command Descriptions in vi").
.P
This command need not be supported on block-mode terminals.
.P
If the cursor does not follow an
.BR autoindent
character, or an
.BR autoindent
character and a
.BR '0' 
or
.BR '^' 
character:
.IP " 1." 4
If the cursor is in column position 1, the
<control>\(hyD
character shall be discarded and no further action taken.
.IP " 2." 4
Otherwise, the
<control>\(hyD
character shall have no special meaning.
.P
If the last input character was a
.BR '0' ,
the cursor shall be moved to column position 1.
.P
Otherwise, if the last input character was a
.BR '^' ,
the cursor shall be moved to column position 1. In addition, the
.BR autoindent
level for the next input line shall be derived from the same line from
which the
.BR autoindent
level for the current input line was derived.
.P
Otherwise, the cursor shall be moved back to the column after the
previous shiftwidth (see the
.IR ex
.BR shiftwidth
command) boundary.
.P
All of the glyphs on columns between the starting cursor position and
(inclusively) the ending cursor position shall become erase-columns as
described in
.IR "Input Mode Commands in vi".
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to 1 if the
<control>\(hyD
was preceded by a
.BR '^' 
or
.BR '0' ;
otherwise, set to (column \(mi1) \(mi((column \(mi2) %
.BR shiftwidth ).
.SS "<control>-H"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-H
.fi \fR
.P
.RE
.RE
.P
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.
.P
If there are characters other than
.BR autoindent
characters that have been input on the current line before the cursor,
the cursor shall move back one character.
.P
Otherwise, if there are
.BR autoindent
characters on the current line before the cursor, it is
implementation-defined whether the
<control>\(hyH
command is an error or if the cursor moves back one
.BR autoindent
character.
.P
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>\(hyH
command is an error or if it is equivalent to entering
<control>\(hyH
after the last input character on the previous input line.
.P
Otherwise, it shall be an error.
.P
All of the glyphs on columns between the starting cursor position and
(inclusively) the ending cursor position shall become erase-columns as
described in
.IR "Input Mode Commands in vi".
.P
The current erase character (see
.IR stty )
shall cause an equivalent action to the
<control>\(hyH
command, unless the previously inserted character was a
<backslash>,
in which case it shall be as if the literal current erase character had
been inserted instead of the
<backslash>.
.P
.IR "Current line" :
Unchanged, unless previously input lines are erased, in which case it
shall be set to line \(mi1.
.P
.IR "Current column" :
Set to the first column that displays any portion of the character
backed up over.
.SS "<newline>"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<newline>
.br
<carriage-return>
.br
<control>-J
.br
<control>-M
.fi \fR
.P
.RE
.RE
.P
If input was part of a line-oriented command, text input mode shall be
terminated and the command shall continue execution with the input
provided.
.P
Otherwise, terminate the current line. If there are no characters other
than
.BR autoindent
characters on the line, all characters on the line shall be discarded.
Otherwise, it is unspecified whether the
.BR autoindent
characters in the line are modified by entering these characters.
.P
Continue text input mode on a new line appended after the current line.
If the
.BR 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.
.P
If the
.BR autoindent
edit option is set, an appropriate number of
.BR autoindent
characters shall be added as a prefix to the line as described by the
.IR ex
.BR autoindent
edit option.
.P
All columns after the cursor that are erase-columns (as described in
.IR "Input Mode Commands in vi")
shall be discarded.
.P
If the
.BR autoindent
edit option is set, all
<blank>
characters immediately following the cursor shall be discarded.
.P
All remaining characters after the cursor shall be transferred to the
new line, positioned after any
.BR autoindent
characters.
.P
.IR "Current line" :
Set to current line +1.
.P
.IR "Current column" :
Set to the first column that displays any portion of the first
character after the
.BR autoindent
characters on the new line, if any, or the first column position after
the last
.BR autoindent
character, if any, or column position 1.
.SS "<control>-T"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-T
.fi \fR
.P
.RE
.RE
.P
The
<control>\(hyT
character shall have no special meaning when in text input mode for a
line-oriented command (see
.IR "Command Descriptions in vi").
.P
This command need not be supported on block-mode terminals.
.P
Behave as if the user entered the minimum number of
<blank>
characters necessary to move the cursor forward to the column position
after the next
.BR shiftwidth
(see the
.IR ex
.BR shiftwidth
command) boundary.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Set to
.IR column
+
.BR shiftwidth
\(mi ((column \(mi1) %
.BR shiftwidth ).
.SS "<control>-U"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-U
.fi \fR
.P
.RE
.RE
.P
If there are characters other than
.BR autoindent
characters that have been input on the current line before the cursor,
the cursor shall move to the first character input after the
.BR autoindent
characters.
.P
Otherwise, if there are
.BR autoindent
characters on the current line before the cursor, it is
implementation-defined whether the
<control>\(hyU
command is an error or if the cursor moves to the first column position
on the line.
.P
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>\(hyU
command is an error or if it is equivalent to entering
<control>\(hyU
after the last input character on the previous input line.
.P
Otherwise, it shall be an error.
.P
All of the glyphs on columns between the starting cursor position and
(inclusively) the ending cursor position shall become erase-columns as
described in
.IR "Input Mode Commands in vi".
.P
The current
.IR kill
character (see
.IR stty )
shall cause an equivalent action to the
<control>\(hyU
command, unless the previously inserted character was a
<backslash>,
in which case it shall be as if the literal current
.IR kill
character had been inserted instead of the
<backslash>.
.P
.IR "Current line" :
Unchanged, unless previously input lines are erased, in which case it
shall be set to line \(mi1.
.P
.IR "Current column" :
Set to the first column that displays any portion of the last character
backed up over.
.SS "<control>-V"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-V
.br
<control>-Q
.fi \fR
.P
.RE
.RE
.P
Allow the entry of any subsequent character, other than
<control>\(hyJ
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>\(hyV
or
<control>\(hyQ
is entered before a
<control>\(hyJ
or
<newline>,
the
<control>\(hyV
or
<control>\(hyQ
character shall be discarded, and the
<control>\(hyJ
or
<newline>
shall behave as described in the
<newline>
command character during input mode.
.P
For purposes of the display only, the editor shall behave as if a
.BR '^' 
character was entered, and the cursor shall be positioned as if
overwriting the
.BR '^' 
character. When a subsequent character is entered, the editor shall
behave as if that character was entered instead of the original
<control>\(hyV
or
<control>\(hyQ
character.
.P
.IR "Current line" :
Unchanged.
.P
.IR "Current column" :
Unchanged.
.SS "<control>-W"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<control>-W
.fi \fR
.P
.RE
.RE
.P
If there are characters other than
.BR 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>
characters 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
.BR autoindent
characters.
.P
Otherwise, if there are
.BR autoindent
characters on the current line before the cursor, it is
implementation-defined whether the
<control>\(hyW
command is an error or if the cursor moves to the first column position
on the line.
.P
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>\(hyW
command is an error or if it is equivalent to entering
<control>\(hyW
after the last input character on the previous input line.
.P
Otherwise, it shall be an error.
.P
All of the glyphs on columns between the starting cursor position and
(inclusively) the ending cursor position shall become erase-columns as
described in
.IR "Input Mode Commands in vi".
.P
.IR "Current line" :
Unchanged, unless previously input lines are erased, in which case it
shall be set to line \(mi1.
.P
.IR "Current column" :
Set to the first column that displays any portion of the last character
backed up over.
.SS "<ESC>"
.IP "\fISynopsis\fR:" 10
.sp -1v
.RS 10 
.sp
.RS 4
.nf
\fB
<ESC>
.fi \fR
.P
.RE
.RE
.P
If input was part of a line-oriented command:
.IP " 1." 4
If
.IR interrupt
was entered, text input mode shall be terminated and the editor shall
return to command mode. The terminal shall be alerted.
.IP " 2." 4
If
<ESC>
was entered, text input mode shall be terminated and the command shall
continue execution with the input provided.
.P
Otherwise, terminate text input mode and return to command mode.
.P
Any
.BR autoindent
characters entered on newly created lines that have no other non-\c
<newline>
characters shall be deleted.
.P
Any leading
.BR autoindent
and
<blank>
characters on newly created lines shall be rewritten to be the minimum
number of
<blank>
characters possible.
.P
The screen shall be redisplayed as necessary to match the contents of
the edit buffer.
.P
.IR "Current line" :
Unchanged.
.br
.P
.IR "Current column" :
.IP " 1." 4
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.
.IP " 2." 4
Otherwise, if a character is displayed in the current column,
unchanged.
.IP " 3." 4
Otherwise, set to column position 1.
.SH "EXIT STATUS"
The following exit values shall be returned:
.IP "\00" 6
Successful completion.
.IP >0 6
An error occurred.
.SH "CONSEQUENCES OF ERRORS"
When any error is encountered and the standard input is not a terminal
device file,
.IR vi
shall not write the file or return to command or text input mode, and
shall terminate with a non-zero exit status.
.P
Otherwise, when an unrecoverable error is encountered it shall be
equivalent to a SIGHUP asynchronous event.
.P
Otherwise, when an error is encountered, the editor shall behave as
specified in
.IR "Command Descriptions in vi".
.LP
.IR "The following sections are informative."
.SH "APPLICATION USAGE"
None.
.SH EXAMPLES
None.
.SH RATIONALE
See the RATIONALE for
.IR "\fIex\fR\^"
for more information on
.IR vi .
Major portions of the
.IR vi
utility specification point to
.IR ex
to avoid inadvertent divergence. While
.IR ex
and
.IR vi
have historically been implemented as a single utility, this is not
required by POSIX.1\(hy2008.
.P
It is recognized that portions of
.IR 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 requirement that such features
should work on all terminals. It is the intention, however, that a
.IR vi
implementation should provide the full set of capabilities on all
terminals capable of supporting them.
.P
Historically,
.IR vi
exited immediately if the standard input was not a terminal. POSIX.1\(hy2008
permits, but does not require, this behavior. An end-of-file condition
is not equivalent to an end-of-file character. A common end-of-file
character,
<control>\(hyD,
is historically a
.IR vi
command.
.P
The text in the STDOUT section reflects the usage of the verb
.IR display
in this section; some implementations of
.IR vi
use standard output to write to the terminal, but POSIX.1\(hy2008 does not
require that to be the case.
.P
Historically, implementations reverted to open mode if the terminal was
incapable of supporting full visual mode. POSIX.1\(hy2008 requires this
behavior. Historically, the open mode of
.IR vi
behaved roughly equivalently 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 messages). In addition, some few commands behaved differently in
open mode than in visual mode. POSIX.1\(hy2008 requires conformance to historical
practice.
.P
Historically,
.IR ex
and
.IR 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 POSIX.1\(hy2008 that this be the case. The specification was
deliberately written using words like ``before'', ``after'', ``first'',
and ``last'' in order to permit implementations to support the natural
text order of the language.
.P
Historically, lines past the end of the edit buffer were marked with
single
<tilde>
(\c
.BR '~' )
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
.BR '~' 
character.
.P
Historically, the
.IR vi
editor attempted to display only complete lines at the bottom of the
screen (it did display 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
.BR '@' 
characters, instead of displaying part of the line. POSIX.1\(hy2008 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.
.P
Historically, lines marked with
.BR '@' 
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
.BR '@' 
sign instead of being updated to match the current text. POSIX.1\(hy2008 permits,
but does not require this feature because it is used ever less
frequently as terminals become smarter and connections are faster.
.SS "Initialization in ex and vi"
.P
Historically,
.IR vi
always had a line in the edit buffer, even if the edit buffer was
``empty''. For example:
.IP " 1." 4
The
.IR ex
command
.BR =
executed from visual mode wrote ``1'' when the buffer was empty.
.IP " 2." 4
Writes from visual mode of an empty edit buffer wrote files of a single
character (a
<newline>),
while writes from
.IR ex
mode of an empty edit buffer wrote empty files.
.IP " 3." 4
Put and read commands into an empty edit buffer left an empty line at
the top of the edit buffer.
.P
For consistency, POSIX.1\(hy2008 does not permit any of these behaviors.
.P
Historically,
.IR vi
did not always return the terminal to its original modes; for example,
ICRNL was modified if it was not originally set. POSIX.1\(hy2008 does not permit
this behavior.
.SS "Command Descriptions in vi"
.P
Motion commands are among the most complicated aspects of
.IR vi
to describe. With some exceptions, the text region and buffer type
effect of a motion command on a
.IR vi
command are described on a case-by-case basis. The descriptions of text
regions in POSIX.1\(hy2008 are not intended to imply direction; that is, an
inclusive region from line
.IR n
to line
.IR n +5
is identical to a region from line
.IR n +5
to line
.IR n .
This is of more than academic interest\(emmovements to marks can be in
either direction, and, if the
.BR 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. POSIX.1\(hy2008 requires conformance to historical
practice.
.P
Historically, command counts were applied to any associated motion, and
were multiplicative to any supplied motion count. For example,
.BR 2cw
is the same as
.BR c2w ,
and
.BR 2c3w
is the same as
.BR c6w .
POSIX.1\(hy2008 requires this behavior. Historically,
.IR vi
commands that used bigwords, words, paragraphs, and sentences as
objects treated groups of empty lines, or lines that contained only
<blank>
characters, inconsistently. Some commands treated them as a single entity,
while others treated each line separately. For example, the
.BR w ,
.BR W ,
and
.BR B
commands treated groups of empty lines as individual words; that is,
the command would move the cursor to each new empty line. The
.BR e
and
.BR E
commands treated groups of empty lines as a single word; that is, the
first use would move past the group of lines. The
.BR 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>
characters, the
.BR w
and
.BR W
commands would just beep at the user, the
.BR E
and
.BR e
commands would treat the group as a single word, and the
.BR B
and
.BR b
commands would treat the lines as individual words. For consistency and
simplicity of specification, POSIX.1\(hy2008 requires that all
.IR vi
commands treat groups of empty or blank lines as a single entity, and
that movement through lines ending with
<blank>
characters be consistent with other movements.
.P
Historically,
.IR vi
documentation indicated that any number of double-quotes were skipped
after punctuation marks at sentence boundaries; however,
implementations only skipped single-quotes. POSIX.1\(hy2008 requires both to be
skipped.
.P
Historically, the first and last characters in the edit buffer were
word boundaries. This historical practice is required by POSIX.1\(hy2008.
.P
Historically,
.IR vi
attempted to update the minimum number of columns on the screen
possible, which could lead to misleading information being displayed.
POSIX.1\(hy2008 makes no requirements other than that the current character being
entered is displayed correctly, leaving all other decisions in this
area up to the implementation.
.P
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. POSIX.1\(hy2008
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.
.P
The historical
.IR 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
.BR j
or
.BR k ,
should work on buffer lines. Commands like
.BR dj ,
or
.BR j. ,
where
.BR .
is a change command, only make sense for buffer lines. It is not,
however, the right thing to do for screen motion or scrolling commands
like
<control>\(hyD,
<control>\(hyF,
and
.BR H .
If the window is fairly small, using buffer lines in these cases can
result in completely random motion; for example,
.BR 1 \c
<control>\c
.BR \(hyD
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
.BR H ,
.BR L ,
and
.BR M
commands\(emas they position the cursor at the first non-\c
<blank>
of the line, they may all refer to the same location in large lines,
and will result in no movement at all.
.P
In addition, if the line is larger than the screen, using buffer
lines can make it impossible to display parts of the line\(emthere are
not any commands that do not display the beginning of the line in
historical
.IR 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-\c
<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>\(hyD
command will refer to the same location on the screen.
.P
Implementations of
.IR ex
and
.IR vi
exist that do not have these problems because the relevant commands (\c
<control>\(hyB,
<control>\(hyD,
<control>\(hyF,
<control>\(hyU,
<control>\(hyY,
<control>\(hyE,
.BR H ,
.BR L ,
and
.BR M)
operate on display (screen) lines, not (edit) buffer lines.
.P
POSIX.1\(hy2008 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,
.IR ex
and
.IR vi
historically 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
.BR '@' 
characters. This behavior is permitted, but not required by POSIX.1\(hy2008, 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). POSIX.1\(hy2008 also permits
implementations to refuse to edit any edit buffer containing a line
that will not fit on the screen in its entirety.
.P
The display area (for example, the value of the
.BR 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
.IR ex
commands generally always caused the screen to be redrawn. POSIX.1\(hy2008 does
not specify a standard behavior because there may be external issues,
such as connection speed, the number of characters necessary to redraw
as opposed to scroll, or terminal capabilities that implementations
will have to accommodate.
.P
The current line in POSIX.1\(hy2008 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 POSIX.1\(hy2008. The first is the current column
value as set by many of the
.IR 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.
.P
Commands that set the current line, but that do not set the current
cursor value (for example,
.BR j
and
.BR 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. POSIX.1\(hy2008 requires conformance to
historical 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.
.P
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,
.BR : ,
.BR ! ,
.BR / ,
or
.BR ? .
POSIX.1\(hy2008 permits, but does not require, this limitation.
.P
Historically, ``soft'' errors in
.IR 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
.IR 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
.BR h
at the left margin,
<control>\(hyB
or
.BR [[
at the beginning of the file,
.BR 2G
at the end of the file, and so on. In addition, errors such as
.BR % ,
.BR ]] ,
.BR } ,
.BR ) ,
.BR N ,
.BR n ,
.BR f ,
.BR F ,
.BR t ,
and
.BR T
failing to find the searched-for object were soft as well. Less
consistently,
.BR /
and
.BR ?
displayed an error message if the pattern was not found,
.BR / ,
.BR ? ,
.BR N ,
and
.BR n
displayed an error message if no previous regular expression had been
specified, and
.BR ;
did not display an error message if no previous
.BR f ,
.BR F ,
.BR t ,
or
.BR 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. POSIX.1\(hy2008 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.
.SS "Page Backwards"
.P
The
<control>\(hyB
and
<control>\(hyF
commands historically considered it an error to attempt to page past
the beginning or end of the file, whereas the
<control>\(hyD
and
<control>\(hyU
commands simply moved to the beginning or end of the file. For
consistency, POSIX.1\(hy2008 requires the latter behavior for all four commands.
All four commands still consider it an error if the current line is at
the beginning (\c
<control>\(hyB,
<control>\(hyU)
or end (\c
<control>\(hyF,
<control>\(hyD)
of the file. Historically, the
<control>\(hyB
and
<control>\(hyF
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
.IR count ,
as there will be, by definition, no overlapping lines. The actual
calculation used by historical implementations of the
.IR vi
editor for
<control>\(hyB
was:
.sp
.RS 4
.nf
\fB
((current first line) \(mi count x (window edit option)) +2
.fi \fR
.P
.RE
.P
and for
<control>\(hyF
was:
.sp
.RS 4
.nf
\fB
((current first line) + count x (window edit option)) \(mi2
.fi \fR
.P
.RE
.P
This calculation does not work well when intermixing commands with and
without counts; for example,
.BR 3\c
<control>\(hyF
is not equivalent to entering the
<control>\(hyF
command three times, and is not reversible by entering the
<control>\(hyB
command three times. For consistency with other
.IR vi
commands that take counts, POSIX.1\(hy2008 requires a different calculation.
.SS "Scroll Forward"
.P
The 4BSD and System V implementations of
.IR vi
differed on the initial value used by the
.BR scroll
command. 4BSD used:
.sp
.RS 4
.nf
\fB
((window edit option) +1) /2
.fi \fR
.P
.RE
.P
while System V used the value of the
.BR scroll
edit option. The System V version is specified by POSIX.1\(hy2008 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.
.SS "Scroll Forward by Line"
.P
Historically, the
<control>\(hyE
and
<control>\(hyY
commands considered it an error if the last and first lines,
respectively, were already on the screen. POSIX.1\(hy2008 requires conformance to
historical practice. Historically, the
<control>\(hyE
and
<control>\(hyY
commands had no effect in open mode. For simplicity and consistency of
specification, POSIX.1\(hy2008 requires that they behave as usual, albeit with a
single line screen.
.SS "Clear and Redisplay"
.P
The historical
<control>\(hyL
command refreshed the screen exactly as it was supposed to be currently
displayed, replacing any
.BR '@' 
characters for lines that had been deleted but not updated on the
screen with refreshed
.BR '@' 
characters. The intent of the
<control>\(hyL
command is to refresh when the screen has been accidentally
overwritten; for example, by a
.BR write
command from another user, or modem noise.
.SS "Redraw Screen"
.P
The historical
<control>\(hyR
command redisplayed only when necessary to update lines that had been
deleted but not updated on the screen and that were flagged with
.BR '@' 
characters. There is no requirement that the screen be in any way
refreshed if no lines of this form are currently displayed. POSIX.1\(hy2008
permits implementations to extend this command to refresh lines on the
screen flagged with
.BR '@' 
characters because they are too long to be displayed in the current
framework; however, the current line and column need not be modified.
.SS "Search for tagstring"
.P
Historically, the first non-\c
<blank>
at or after the cursor was the first character, and all subsequent
characters 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
.BR '#' 
character in the text
.BR \(dq#bar@\(dq ,
the tag was
.BR \(dq#bar\(dq .
On the character
.BR 'b' 
it was
.BR \(dqbar\(dq ,
and on the
.BR 'a' 
it was
.BR \(dqar\(dq .
POSIX.1\(hy2008 requires this behavior.
.SS "Replace Text with Results from Shell Command"
.P
Historically, the
.BR < ,
.BR > ,
and
.BR !
commands considered most cursor motions other than line-oriented
motions an error; for example, the command
.BR ">/foo<CR>"
succeeded, while the command
.BR ">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.
.SS "Move to Matching Character"
.P
Other matching characters have been left implementation-defined in
order to allow extensions such as matching
.BR '<' 
and
.BR '>' 
for searching HTML, or
.BR #ifdef ,
.BR #else ,
and
.BR #endif
for searching C source.
.SS "Repeat Substitution"
.P
POSIX.1\(hy2008 requires that any
.BR c
and
.BR g
flags specified to the previous substitute command be ignored; however,
the
.BR r
flag may still apply, if supported by the implementation.
.SS "Return to Previous (Context or Section)"
.P
The
.BR [[ ,
.BR ]] ,
.BR ( ,
.BR ) ,
.BR { ,
and
.BR }
commands are all affected by ``section boundaries'', but in some
historical implementations 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. Historically,
.IR vi
section boundaries at the beginning and end of the edit buffer were the
first non-\c
<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 POSIX.1\(hy2008 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.
.P
Sentence boundaries were problematic in the historical
.IR vi .
They were not only the boundaries as defined for the section and
paragraph commands, but they were the first non-\c
<blank>
that occurred after those boundaries, as well. Historically, the
.IR vi
section commands were documented as taking an optional window size as a
.IR count
preceding the command. This was not implemented in historical versions,
so POSIX.1\(hy2008 requires that the
.IR count
repeat the command, for consistency with other
.IR vi
commands.
.SS "Repeat"
.P
Historically, mapped commands other than text input commands could not
be repeated using the
.BR period
command. POSIX.1\(hy2008 requires conformance to historical practice.
.P
The restrictions on the interpretation of special characters (for
example,
<control>\(hyH)
in the repetition of text input mode commands is intended to match
historical practice. For example, given the input sequence:
.sp
.RS 4
.nf
\fB
iab<control>-H<control>-H<control>-Hdef<escape>
.fi \fR
.P
.RE
.P
the user should be informed of an error when the sequence is first
entered, but not during a command repetition. The character
<control>\(hyT
is specifically exempted from this restriction. Historical
implementations of
.IR vi
ignored
<control>\(hyT
characters that were input in the original command during command
repetition. POSIX.1\(hy2008 prohibits this behavior.
.SS "Find Regular Expression"
.P
Historically, commands did not affect the line searched to or from if
the motion command was a search (\c
.BR / ,
.BR ? ,
.BR N ,
.BR n )
and the final position was the start/end of the line. There were some
special cases and
.IR vi
was not consistent. POSIX.1\(hy2008 does not permit this behavior, for
consistency. Historical implementations permitted but were unable to
handle searches as motion commands that wrapped (that is, due to the
edit option
.BR wrapscan )
to the original location. POSIX.1\(hy2008 requires that this behavior be treated
as an error.
.P
Historically, the syntax
.BR \(dq/RE/0\(dq 
was used to force the command to cut text in line mode. POSIX.1\(hy2008 requires
conformance to historical practice.
.P
Historically, in open mode, a
.BR z
specified to a search command redisplayed the current line instead of
displaying the current screen with the current line highlighted. For
consistency and simplicity of specification, POSIX.1\(hy2008 does not permit this
behavior.
.P
Historically, trailing
.BR z
commands were permitted and ignored if entered as part of a search used
as a motion command. For consistency and simplicity of specification,
POSIX.1\(hy2008 does not permit this behavior.
.SS "Execute an ex Command"
.P
Historically,
.IR vi
implementations restricted the commands that could be entered on the
colon command line (for example,
.BR append
and
.BR change ),
and some other commands were known to cause them to fail
catastrophically. For consistency, POSIX.1\(hy2008 does not permit these
restrictions. When executing an
.IR ex
command by entering
.BR : ,
it is not possible to enter a
<newline>
as part of the command because it is considered the end of the command.
A different approach is to enter
.IR ex
command mode by using the
.IR vi
.BR Q
command (and later resuming visual mode with the
.IR ex
.BR vi
command). In
.IR ex
command mode, the single-line limitation does not exist. So, for
example, the following is valid:
.sp
.RS 4
.nf
\fB
Q
s/break here/break\e
here/
vi
.fi \fR
.P
.RE
.P
POSIX.1\(hy2008 requires that, if the
.IR ex
command overwrites any part of the screen that would be erased by a
refresh,
.IR 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
probably 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 indignation back into historical behavior. POSIX.1\(hy2008 requires
conformance to historical practice.
.SS "Shift Left (Right)"
.P
Refer to the Rationale for the
.BR !
and
.BR /
commands. Historically, the
.BR <
and
.BR >
commands sometimes moved the cursor to the first non-\c
<blank>
(for example if the command was repeated or with
.BR _
as the motion command), and sometimes left it unchanged. POSIX.1\(hy2008 does not
permit this inconsistency, requiring instead that the cursor always
move to the first non-\c
<blank>.
Historically, the
.BR <
and
.BR >
commands did not support buffer arguments, although some
implementations allow the specification of an optional buffer. This
behavior is neither required nor disallowed by POSIX.1\(hy2008.
.SS "Execute"
.P
Historically, buffers could execute other buffers, and loops, infinite
and otherwise, were possible. POSIX.1\(hy2008 requires conformance to historical
practice. The *\c
.IR buffer
syntax of
.IR ex
is not required in
.IR vi ,
because it is not historical practice and has been used in some
.IR vi
implementations to support additional scripting languages.
.SS "Reverse Case"
.P
Historically, the
.BR ~
command ignored any associated
.IR count ,
and acted only on the characters in the current line. For consistency
with other
.IR vi
commands, POSIX.1\(hy2008 requires that an associated
.IR count
act on the next
.IR count
characters, and that the command move to subsequent lines if warranted
by
.IR count ,
to make it possible to modify large pieces of text in a reasonably
efficient manner. There exist
.IR vi
implementations that optionally require an associated motion command
for the
.BR ~
command. Implementations supporting this functionality are encouraged
to base it on the
.BR tildedop
edit option and handle the text regions and cursor positioning
identically to the
.BR yank
command.
.SS "Append"
.P
Historically,
.IR count s
specified to the
.BR A ,
.BR a ,
.BR I ,
and
.BR i
commands repeated the input of the first line
.IR count
times, and did not repeat the subsequent lines of the input text. POSIX.1\(hy2008
requires that the entire text input be repeated
.IR count
times.
.SS "Move Backward to Preceding Word"
.P
Historically,
.IR vi
became confused if word commands were used as motion commands in empty
files. POSIX.1\(hy2008 requires that this be an error. Historical implementations
of
.IR 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>
characters. For consistency and simplicity of specification, POSIX.1\(hy2008 does
not permit this behavior.
.SS "Change to End-of-Line"
.P
Some historical implementations of the
.BR C
command did not behave as described by POSIX.1\(hy2008 when the
.BR $
key was remapped because they were implemented by pushing the
.BR $
key onto the input queue and reprocessing it. POSIX.1\(hy2008 does not permit
this behavior. Historically, the
.BR C ,
.BR S ,
and
.BR s
commands did not copy replaced text into the numeric buffers. For
consistency and simplicity of specification, POSIX.1\(hy2008 requires that they
behave like their respective
.BR c
commands in all respects.
.SS "Delete"
.P
Historically, lines in open mode that were deleted were scrolled up,
and an
.BR @
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. POSIX.1\(hy2008 requires conformance to
historical practice; that is, if the terminal cannot display the
.BR '@' 
character, the line cannot remain on the screen.
.SS "Delete to End-of-Line"
.P
Some historical implementations of the
.BR D
command did not behave as described by POSIX.1\(hy2008 when the
.BR $
key was remapped because they were implemented by pushing the
.BR $
key onto the input queue and reprocessing it. POSIX.1\(hy2008 does not permit
this behavior.
.SS "Join"
.P
An historical oddity of
.IR vi
is that the commands
.BR J ,
.BR 1J ,
and
.BR 2J
are all equivalent. POSIX.1\(hy2008 requires conformance to historical practice.
The
.IR vi
.BR J
command is specified in terms of the
.IR ex
.BR join
command with an
.IR ex
command
.IR count
value. The address correction for a
.IR count
that is past the end of the edit buffer is necessary for historical
compatibility for both
.IR ex
and
.IR vi .
.SS "Mark Position"
.P
Historical practice is that only lowercase letters, plus backquote and
single-quote, could be used to mark a cursor position. POSIX.1\(hy2008 requires
conformance to historical practice, but encourages implementations to
support other characters as marks as well.
.SS "Repeat Regular Expression Find (Forward and Reverse)"
.P
Historically, the
.BR N
and
.BR n
commands could not be used as motion components for the
.BR c
command. With the exception of the
.BR 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, POSIX.1\(hy2008 does not
permit this behavior.
.SS "Insert Empty Line (Below and Above)"
.P
Historically, counts to the
.BR O
and
.BR o
commands were used as the number of physical lines to open, if the
terminal was dumb and the
.BR slowopen
option was not set. This was intended to minimize traffic over slow
connections and repainting for dumb terminals. POSIX.1\(hy2008 does not permit
this behavior, requiring that a
.IR count
to the open command behave as for other text input commands. This
change to historical practice was made for consistency, and because a
superset of the functionality is provided by the
.BR slowopen
edit option.
.SS "Put from Buffer (Following and Before)"
.P
Historically,
.IR count s
to the
.BR p
and
.BR P
commands were ignored if the buffer was a line mode buffer, but were
(mostly) implemented as described in POSIX.1\(hy2008 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, POSIX.1\(hy2008 requires that
.IR count
be supported for all
.BR p
and
.BR P
commands.
.P
Historical implementations of
.IR vi
were widely known to have major problems in the
.BR p
and
.BR 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.
.P
Historically, a
.BR P
or
.BR p
command (or an
.IR ex
.BR 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, POSIX.1\(hy2008 does not permit this behavior.
.SS "Replace Character"
.P
Historically, the
.BR r
command did not correctly handle the
.IR erase
and
.IR "word erase"
characters as arguments, nor did it handle an associated
.IR count
greater than 1 with a
<carriage-return>
argument, for which it replaced
.IR count
characters with a single
<newline>.
POSIX.1\(hy2008 does not permit these inconsistencies.
.P
Historically, the
.BR r
command permitted the
<control>\(hyV
escaping of entered characters, such as
<ESC>
and the
<carriage-return>;
however, it required two leading
<control>\(hyV
characters instead of one. POSIX.1\(hy2008 requires that this be changed for
consistency with the other text input commands of
.IR vi .
.P
Historically, it is an error to enter the
.BR r
command if there are less than
.IR count
characters at or after the cursor in the line. While a reasonable and
unambiguous extension would be to permit the
.BR r
command on empty lines, it would require that too large a
.IR 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. POSIX.1\(hy2008 requires conformance to historical
practice.
.SS "Replace Characters"
.P
Historically, if there were
.BR autoindent
characters in the line on which the
.BR R
command was run, and
.BR autoindent
was set, the first
<newline>
would be properly indented and no characters would be replaced by the
<newline>.
Each additional
<newline>
would replace
.IR n
characters, where
.IR 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 POSIX.1\(hy2008.
.SS "Undo"
.P
Historical practice for cursor positioning after undoing commands was
mixed. In most cases, when undoing commands 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-\c
<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
.BR o
text input command, followed by an
.BR undo
would return the cursor to the location where the
.BR o
command was entered, but a
.BR cw
command followed by an
.BR o
command followed by an
.BR undo
would return the cursor to the first non-\c
<blank>
of the line. POSIX.1\(hy2008 requires the most useful of these behaviors, and
discards the least useful, in the interest of consistency and
simplicity of specification.
.SS "Yank"
.P
Historically, the
.BR yank
command did not move to the end of the motion if the motion was in the
forward direction. It moved to the end of the motion if the motion was
in the backward direction, except for the
.BR _
command, or for the
.BR G
and
.BR '
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
.BR 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
.BR yank
command. POSIX.1\(hy2008 requires that all
.BR yank
commands associated with backward motions move the cursor to the end of
the motion for consistency, and specifically, to make
.BR '
commands as motions consistent with search patterns as motions.
.SS "Yank Current Line"
.P
Some historical implementations of the
.BR Y
command did not behave as described by POSIX.1\(hy2008 when the
.BR '_' 
key was remapped because they were implemented by pushing the
.BR '_' 
key onto the input queue and reprocessing it. POSIX.1\(hy2008 does not permit
this behavior.
.SS "Redraw Window"
.P
Historically, the
.BR z
command always redrew the screen. This is permitted but not required by
POSIX.1\(hy2008, because of the frequent use of the
.BR z
command in macros such as
.BR "map n nz."
for screen positioning, 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>\(hyL
and
<control>\(hyR
commands.
.P
The semantics of
.BR z^
are confusing at best. Historical practice is that the screen before
the screen that ended with the specified line is displayed. POSIX.1\(hy2008
requires conformance to historical practice.
.P
Historically, the
.BR 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
.BR '@' 
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, POSIX.1\(hy2008 does not permit this behavior.
.P
Historically, the
.BR z
command with a line specification of 1 ignored the command. For
consistency and simplicity of specification, POSIX.1\(hy2008 does not permit this
behavior.
.P
Historically, the
.BR z
command did not set the cursor column to the first non-\c
<blank>
for the character if the first screen was to be displayed, and was
already displayed. For consistency and simplicity of specification,
POSIX.1\(hy2008 does not permit this behavior.
.SS "Input Mode Commands in vi"
.P
Historical implementations of
.IR vi
did not permit the user to erase more than a single line of input,
or to use normal erase characters such as
.IR "line erase" ,
.IR worderase ,
and
.IR erase
to erase
.BR autoindent
characters. As there exist implementations of
.IR vi
that do not have these limitations, both behaviors are permitted, but
only historical practice is required. In the case of these extensions,
.IR vi
is required to pause at the
.BR autoindent
and previous line boundaries.
.P
Historical implementations of
.IR vi
updated only the portion of the screen where the current cursor
character was displayed. For example, consider the
.IR vi
input keystrokes:
.sp
.RS 4
.nf
\fB
iabcd<escape>0C<tab>
.fi \fR
.P
.RE
.P
Historically, the
<tab>
would overwrite the characters
.BR \(dqabcd\(dq 
when it was displayed. Other implementations replace only the
.BR '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:
.sp
.RS 4
.nf
\fB
iabcd<ESC>0R<tab><ESC>
.fi \fR
.P
.RE
.P
the historical implementation results in the string
.BR \(dqbcd\(dq 
disappearing and then magically reappearing when the
<ESC>
character is entered. POSIX.1\(hy2008 requires the former behavior when
overwriting erase-columns\(emthat is, overwriting characters that are no
longer logically part of the edit buffer\(emand the latter behavior
otherwise.
.P
Historical implementations of
.IR vi
discarded the
<control>\(hyD
and
<control>\(hyT
characters when they were entered at places where their command
functionality was not appropriate. POSIX.1\(hy2008 requires that the
<control>\(hyT
functionality always be available, and that
<control>\(hyD
be treated as any other key when not operating on
.BR autoindent
characters.
.SS "NUL"
.P
Some historical implementations of
.IR vi
limited the number of characters entered using the NUL input character
to 256 bytes. POSIX.1\(hy2008 permits this limitation; however, implementations
are encouraged to remove this limit.
.SS "<control>\(hyD"
.P
See also Rationale for the input mode command
<newline>.
The hidden assumptions in the
<control>\(hyD
command (and in the
.IR vi
.BR autoindent
specification in general) is that
<space>
characters take up a single column on the screen and that
<tab>
characters are comprised of an integral number of
<space>
characters.
.SS "<newline>"
.P
Implementations are permitted to rewrite
.BR autoindent
characters in the line when
<newline>,
<carriage-return>,
<control>\(hyD,
and
<control>\(hyT
are entered, or when the
.BR shift
commands are used, because historical implementations have both done so
and found it necessary to do so. For example, a
<control>\(hyD
when the cursor is preceded by a single
<tab>,
with
.BR tabstop
set to 8, and
.BR shiftwidth
set to 3, will result in the
<tab>
being replaced by several
<space>
characters.
.SS "<control>\(hyT"
.P
See also the Rationale for the input mode command
<newline>.
Historically,
<control>\(hyT
only worked if no non-\c
<blank>
characters had yet been input in the current input line. In addition,
the characters inserted by
<control>\(hyT
were treated as
.BR autoindent
characters, and could not be erased using normal user erase characters.
Because implementations exist that do not have these limitations, and
as moving to a column boundary is generally useful, POSIX.1\(hy2008 requires that
both limitations be removed.
.SS "<control>\(hyV"
.P
Historically,
.IR vi
used
.BR ^V ,
regardless of the value of the literal-next character of the terminal.
POSIX.1\(hy2008 requires conformance to historical practice.
.P
The uses described for
<control>\(hyV
can also be accomplished with
<control>\(hyQ,
which is useful on terminals that use
<control>\(hyV
for the down-arrow function. However, most historical implementations
use
<control>\(hyQ
for the
.IR termios
START character, so the editor will generally not receive the
<control>\(hyQ
unless
.BR "stty ixon"
mode is set to off. (In addition, some historical implementations of
.IR vi
explicitly set
.BR ixon
mode to on, so it was difficult for the user to set it to off.) Any of
the command characters described in POSIX.1\(hy2008 can be made ineffective by
their selection as
.IR termios
control characters, using the
.IR stty
utility or other methods described in the System Interfaces volume of POSIX.1\(hy2008.
.SS "<ESC>"
.P
Historically, SIGINT alerted the terminal when used to end input
mode. This behavior is permitted, but not required, by POSIX.1\(hy2008.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIed\fR\^",
.IR "\fIex\fR\^",
.IR "\fIstty\fR\^"
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "Section 12.2" ", " "Utility Syntax Guidelines"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.unix.org/online.html .

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