File: vi.1p

package info (click to toggle)
manpages-posix 1.67-3
links: PTS
area: non-free
in suites: sarge
size: 9,564 kB
ctags: 6
sloc: makefile: 69; sh: 37
file content (4963 lines) | stat: -rw-r--r-- 154,923 bytes
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "VI" P 2003 POSIX
.\" vi 
.SH NAME
vi \- screen-oriented (visual) display editor
.SH SYNOPSIS
.LP
\fBvi\fP \fB[\fP\fB-rR\fP\fB][\fP\fB-c\fP \fIcommand\fP\fB][\fP\fB-t\fP
\fItagstring\fP\fB][\fP\fB-w\fP \fIsize\fP\fB][\fP\fIfile\fP \fB...\fP\fB]\fP\fB\fP
.SH DESCRIPTION
.LP
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.
.LP
The \fIvi\fP (visual) utility is a screen-oriented text editor. Only
the open and visual modes of the editor are described in
IEEE\ Std\ 1003.1-2001; see the line editor \fIex\fP for additional
editing
capabilities used in \fIvi\fP. The user can switch back and forth
between \fIvi\fP and \fIex\fP and execute \fIex\fP commands from within
\fIvi\fP.
.LP
This reference page uses the term \fIedit buffer\fP 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.
.LP
When using \fIvi\fP, 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.
.LP
Certain terminals do not have all the capabilities necessary to support
the complete \fIvi\fP definition. When these commands
cannot be supported on such terminals, this condition shall not produce
an error message such as "not an editor command" or
report a syntax error. The implementation may either accept the commands
and produce results on the screen that are the result of
an unsuccessful attempt to meet the requirements of this volume of
IEEE\ Std\ 1003.1-2001 or report an error describing the
terminal-related deficiency.
.SH OPTIONS
.LP
The \fIvi\fP utility shall conform to the Base Definitions volume
of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
.LP
The following options shall be supported:
.TP 7
\fB-c\ \fP \fIcommand\fP
See the \fIex\fP command description of the \fB-c\fP option.
.TP 7
\fB-r\fP
See the \fIex\fP command description of the \fB-r\fP option.
.TP 7
\fB-R\fP
See the \fIex\fP command description of the \fB-R\fP option.
.TP 7
\fB-t\ \fP \fItagstring\fP
See the \fIex\fP command description of the \fB-t\fP option.
.TP 7
\fB-w\ \fP \fIsize\fP
See the \fIex\fP command description of the \fB-w\fP option.
.sp
.SH OPERANDS
.LP
See the OPERANDS section of the \fIex\fP command for a description
of the operands supported
by the \fIvi\fP command.
.SH STDIN
.LP
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.
.LP
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
.LP
See the INPUT FILES section of the \fIex\fP command for a description
of the input files
supported by the \fIvi\fP command.
.SH ENVIRONMENT VARIABLES
.LP
See the ENVIRONMENT VARIABLES section of the \fIex\fP command for
the environment variables
that affect the execution of the \fIvi\fP command.
.SH ASYNCHRONOUS EVENTS
.LP
See the ASYNCHRONOUS EVENTS section of the \fIex\fP for the asynchronous
events that affect
the execution of the \fIvi\fP command.
.SH STDOUT
.LP
If standard output is not a terminal device, undefined results occur.
.LP
Standard output may be used for writing prompts to the user, for informational
messages, and for writing lines from the
file.
.SH STDERR
.LP
If standard output is not a terminal device, undefined results occur.
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
See the OUTPUT FILES section of the \fIex\fP command for a description
of the output files
supported by the \fIvi\fP command.
.SH EXTENDED DESCRIPTION
.LP
If the terminal does not have the capabilities necessary to support
an unspecified portion of the \fIvi\fP definition,
implementations shall start initially in \fIex\fP mode or open mode.
Otherwise, after
initialization, \fIvi\fP shall be in command mode; text input mode
can be entered by one of several commands used to insert or
change text. In text input mode, <ESC> can be used to return to command
mode; other uses of <ESC> are described later
in this section; see Terminate Command or Input Mode .
.SS Initialization in ex and vi
.LP
See \fIInitialization in ex and vi\fP for a description of \fIex\fP
and \fIvi\fP initialization for the \fIvi\fP utility.
.SS Command Descriptions in vi
.LP
The following symbols are used in this reference page to represent
arguments to commands.
.TP 7
\fIbuffer\fP
See the description of \fIbuffer\fP in the EXTENDED DESCRIPTION section
of the \fIex\fP
utility; see \fICommand Descriptions in ex\fP . 
.LP
In open and visual mode, when a command synopsis shows both [ \fIbuffer\fP]
and [ \fIcount\fP] preceding the command name,
they can be specified in either order.
.TP 7
\fIcount\fP
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. 
.LP
The Synopsis lines for the \fIvi\fP commands <control>-G, <control>-L,
<control>-R, <control>-],
\fB%\fP, \fB&\fP, \fB^\fP, \fBD\fP, \fBm\fP, \fBM\fP, \fBQ\fP, \fBu\fP,
\fBU\fP, and \fBZZ\fP do not have
\fIcount\fP as an optional argument. Regardless, it shall not be an
error to specify a \fIcount\fP to these commands, and any
specified \fIcount\fP shall be ignored.
.TP 7
\fImotion\fP
An optional trailing argument used by the \fB!\fP, \fB<\fP, \fB>\fP,
\fBc\fP, \fBd\fP, and \fBy\fP 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 \fIvi\fP 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. 
.LP
Commands that take \fImotion\fP 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.
.LP
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.
.LP
The following commands shall be valid cursor motion commands:
.sp
.RS
.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
\fP
.fi
.RE
.LP
Any \fIcount\fP that is specified to a command that has an associated
motion command shall be applied to the motion command. If
a \fIcount\fP is applied to both the command and its associated motion
command, the effect shall be multiplicative.
.sp
.LP
The following symbols are used in this section to specify locations
in the edit buffer:
.TP 7
\fIcurrent\ character\fP
.sp
The character that is currently indicated by the cursor.
.TP 7
\fIend\ of\ a\ line\fP
.sp
The point located between the last non- <newline> (if any) and the
terminating <newline> of a line. For an empty line,
this location coincides with the beginning of the line.
.TP 7
\fIend\ of\ the\ edit\ buffer\fP
.sp
The location corresponding to the end of the last line in the edit
buffer.
.sp
.LP
The following symbols are used in this section to specify command
actions:
.TP 7
\fIbigword\fP
In the POSIX locale, \fIvi\fP shall recognize four kinds of \fIbigwords\fP:
.RS
.IP " 1." 4
A maximal sequence of non- <blank>s preceded and followed by <blank>s
or the beginning or end of a line or the edit
buffer
.LP
.IP " 2." 4
One or more sequential blank lines
.LP
.IP " 3." 4
The first character in the edit buffer
.LP
.IP " 4." 4
The last non- <newline> in the edit buffer
.LP
.RE
.TP 7
\fIword\fP
In the POSIX locale, \fIvi\fP shall recognize five kinds of words:
.RS
.IP " 1." 4
A maximal sequence of letters, digits, and underscores, delimited
at both ends by:
.RS
.IP " *" 3
Characters other than letters, digits, or underscores
.LP
.IP " *" 3
The beginning or end of a line
.LP
.IP " *" 3
The beginning or end of the edit buffer
.LP
.RE
.LP
.IP " 2." 4
A maximal sequence of characters other than letters, digits, underscores,
or <blank>s, delimited at both ends by:
.RS
.IP " *" 3
A letter, digit, underscore
.LP
.IP " *" 3
<blank>s
.LP
.IP " *" 3
The beginning or end of a line
.LP
.IP " *" 3
The beginning or end of the edit buffer
.LP
.RE
.LP
.IP " 3." 4
One or more sequential blank lines
.LP
.IP " 4." 4
The first character in the edit buffer
.LP
.IP " 5." 4
The last non- <newline> in the edit buffer
.LP
.RE
.TP 7
\fIsection\ boundary\fP
.sp
A \fIsection boundary\fP is one of the following: 
.RS
.IP " 1." 4
A line whose first character is a <form-feed>
.LP
.IP " 2." 4
A line whose first character is an open curly brace ( \fB'{'\fP )
.LP
.IP " 3." 4
A line whose first character is a period and whose second and third
characters match a two-character pair in the \fBsections\fP
edit option (see \fIed\fP)
.LP
.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 \fBsections\fP edit option, where the second character of the
two-character pair is a <space>
.LP
.IP " 5." 4
The first line of the edit buffer
.LP
.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 \fB]]\fP or \fB}\fP command;
otherwise, the last non- <newline> of the last line of the edit buffer
.LP
.RE
.TP 7
\fIparagraph\ boundary\fP
.sp
A \fIparagraph boundary\fP is one of the following: 
.RS
.IP " 1." 4
A section boundary
.LP
.IP " 2." 4
A line whose first character is a period and whose second and third
characters match a two-character pair in the
\fBparagraphs\fP edit option (see \fIed\fP)
.LP
.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 \fIparagraphs\fP edit option, where the second character of the
two-character pair is a <space>
.LP
.IP " 4." 4
One or more sequential blank lines
.LP
.RE
.TP 7
\fIremembered\ search\ direction\fP
.sp
See the description of \fIremembered search direction\fP in \fIed\fP.
.TP 7
\fIsentence\ boundary\fP
.sp
A \fIsentence boundary\fP is one of the following: 
.RS
.IP " 1." 4
A paragraph boundary
.LP
.IP " 2." 4
The first non- <blank> that occurs after a paragraph boundary
.LP
.IP " 3." 4
The first non- <blank> that occurs after a period ( \fB'.'\fP ), exclamation
mark ( \fB'!'\fP ), or question mark (
\fB'?'\fP ), followed by two <space>s or the end of a line; any number
of closing parenthesis ( \fB')'\fP ), closing
brackets ( \fB']'\fP ), double quote ( \fB' ),'\fP or single quote
( \fB'"\fP ) characters can appear between the
punctuation mark and the two <space>s or end-of-line
.LP
.RE
.sp
.LP
In the remainder of the description of the \fIvi\fP 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".
.LP
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 ( \fB'~'\fP ) character, plus the terminating
<newline>.
.LP
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" ( \fB/\fP, \fB?\fP, \fB:\fP,
and \fB!\fP). 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 \fB!\fP 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- <control>-V-escaped
<carriage-return>, or unescaped <ESC>. It is unspecified if more characters
than require a display width minus one
column number of screen columns can be entered.
.LP
If any command is executed that overwrites a portion of the screen
other than the last line of the screen (for example, the \fIex\fP
\fBsuspend\fP or \fB!\fP commands), other than the \fIex\fP \fBshell\fP
command, the user shall be prompted for a character before the screen
is
refreshed and the edit session continued.
.LP
<tab>s shall take up the number of columns on the screen set by the
\fBtabstop\fP edit option (see \fIed\fP), 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.
.LP
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.
.LP
In open mode, if the current line is not already displayed, then it
shall be displayed.
.LP
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 \fBwindow\fP edit option shall
be displayed (unless the current line cannot be completely
displayed in the number of display lines specified by the \fBwindow\fP
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.
.LP
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 \fB'@'\fP
character.
.LP
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 \fB'@'\fP character (plus the terminating <newline>),
and the <control>-R command shall cause
the editor to update the screen to correctly represent the edit buffer.
.LP
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.
.LP
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- <newline>
in the current line; otherwise, the display cursor column
shall be set to the current column.
.LP
.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
.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.
.LP
.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.
.LP
.RE
.LP
.LP
The current column shall not be changed by these adjustments to the
display cursor column.
.LP
If an error occurs during the parsing or execution of a \fIvi\fP command:
.IP " *" 3
The terminal shall be alerted. Execution of the \fIvi\fP command shall
stop, and the cursor (for example, the current line and
column) shall not be further modified.
.LP
.IP " *" 3
Unless otherwise specified by the following command sections, it is
unspecified whether an informational message shall be
displayed.
.LP
.IP " *" 3
Any partially entered \fIvi\fP command shall be discarded.
.LP
.IP " *" 3
If the \fIvi\fP command resulted from a \fBmap\fP expansion, all characters
from that \fBmap\fP expansion shall be discarded,
except as otherwise specified by the \fBmap\fP command (see \fIed\fP).
.LP
.IP " *" 3
If the \fIvi\fP command resulted from the execution of a buffer, no
further commands caused by the execution of the buffer
shall be executed.
.LP
.SS Page Backwards
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-B
\fP
.fi
.RE
.sp
.LP
If in open mode, the <control>-B command shall behave identically
to the \fBz\fP command. Otherwise, if the current line
is the first line of the edit buffer, it shall be an error.
.LP
If the \fBwindow\fP edit option is less than 3, display a screen where
the last line of the display shall be some portion
of:
.sp
.RS
.nf

\fB(\fP\fIcurrent first line\fP\fB) -1
\fP
.fi
.RE
.LP
otherwise, display a screen where the first line of the display shall
be some portion of:
.sp
.RS
.nf

\fB(\fP\fIcurrent first line\fP\fB) -\fP \fIcount\fP \fBx ((window edit option) -2)
\fP
.fi
.RE
.LP
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.
.LP
\fICurrent line\fP: If no lines from the previous display remain on
the screen, set to the last line of the display; otherwise,
set to ( \fIline\fP - the number of new lines displayed on this screen).
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Scroll Forward
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-D
\fP
.fi
.RE
.sp
.LP
If the current line is the last line of the edit buffer, it shall
be an error.
.LP
If no \fIcount\fP is specified, \fIcount\fP shall default to the \fIcount\fP
associated with the previous <control>-D
or <control>-U command. If there was no previous <control>-D or <control>-U
command, \fIcount\fP shall default
to the value of the \fBscroll\fP edit option.
.LP
If in open mode, write lines starting with the line after the current
line, until \fIcount\fP lines or the last line of the
file have been written.
.LP
\fICurrent line\fP: If the current line + \fIcount\fP is past the
last line of the edit buffer, set to the last line of the
edit buffer; otherwise, set to the current line + \fIcount\fP.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Scroll Forward by Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-E
\fP
.fi
.RE
.sp
.LP
Display the line count lines after the last line currently displayed.
.LP
If the last line of the edit buffer is displayed, it shall be an error.
If there is no line \fIcount\fP 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.
.LP
\fICurrent line\fP: Unchanged if the previous current character is
displayed; otherwise, set to the first line displayed.
.LP
\fICurrent column\fP: Unchanged.
.SS Page Forward
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-F
\fP
.fi
.RE
.sp
.LP
If in open mode, the <control>-F command shall behave identically
to the \fBz\fP command. Otherwise, if the current line
is the last line of the edit buffer, it shall be an error.
.LP
If the \fBwindow\fP edit option is less than 3, display a screen where
the first line of the display shall be some portion
of:
.sp
.RS
.nf

\fB(\fP\fIcurrent last line\fP\fB) +1
\fP
.fi
.RE
.LP
otherwise, display a screen where the first line of the display shall
be some portion of:
.sp
.RS
.nf

\fB(\fP\fIcurrent first line\fP\fB) +\fP \fIcount\fP \fBx ((window edit option) -2)
\fP
.fi
.RE
.LP
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.
.LP
\fICurrent line\fP: If no lines from the previous display remain on
the screen, set to the first line of the display;
otherwise, set to ( \fIline\fP + the number of new lines displayed
on this screen).
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Display Information
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-G
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIex\fP \fBfile\fP command.
.SS Move Cursor Backwards
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-H
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fBh
.sp

the current\fP \fIerase\fP \fBcharacter (see stty)
\fP
.fi
.RE
.sp
.LP
If there are no characters before the current character on the current
line, it shall be an error. If there are less than
\fIcount\fP previous characters on the current line, \fIcount\fP shall
be adjusted to the number of previous characters on the
line.
.LP
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 \fIcount\fPth character before
the starting cursor.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to ( \fIcolumn\fP - the number of columns
occupied by \fIcount\fP characters ending with the
previous current column).
.SS Move Down
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<newline>
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fB<control>-J
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fB<control>-M
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fB<control>-N
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fBj
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fB<carriage-return>
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fB+
\fP
.fi
.RE
.sp
.LP
If there are less than \fIcount\fP lines after the current line in
the edit buffer, it shall be an error.
.LP
If used as a motion command:
.IP " 1." 4
The text region shall include the starting line and the next \fIcount\fP
- 1 lines.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in line mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to \fIcurrent line\fP+ \fIcount\fP.
.LP
\fICurrent column\fP: Set to non- <blank> for the <carriage-return>,
<control>-M, and \fB+\fP commands;
otherwise, unchanged.
.SS Clear and Redisplay
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-L
\fP
.fi
.RE
.sp
.LP
If in open mode, clear the screen and redisplay the current line.
Otherwise, clear and redisplay the screen.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Unchanged.
.SS Move Up
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-P
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fBk
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fB-
\fP
.fi
.RE
.sp
.LP
If there are less than \fIcount\fP lines before the current line in
the edit buffer, it shall be an error.
.LP
If used as a motion command:
.IP " 1." 4
The text region shall include the starting line and the previous \fIcount\fP
lines.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in line mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to \fIcurrent line\fP - \fIcount\fP.
.LP
\fICurrent column\fP: Set to non- <blank> for the \fB-\fP command;
otherwise, unchanged.
.SS Redraw Screen
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-R
\fP
.fi
.RE
.sp
.LP
If any lines have been deleted from the display screen and flagged
as deleted on the terminal using the \fB@\fP convention (see
the beginning of the EXTENDED DESCRIPTION section), they shall be
redisplayed to match the contents of the edit buffer.
.LP
It is unspecified whether lines flagged with \fB@\fP because they
do not fit on the terminal display shall be affected.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Unchanged.
.SS Scroll Backward
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-U
\fP
.fi
.RE
.sp
.LP
If the current line is the first line of the edit buffer, it shall
be an error.
.LP
If no \fIcount\fP is specified, \fIcount\fP shall default to the \fIcount\fP
associated with the previous <control>-D
or <control>-U command. If there was no previous <control>-D or <control>-U
command, \fIcount\fP shall default
to the value of the \fBscroll\fP edit option.
.LP
\fICurrent line\fP: If \fIcount\fP is greater than the current line,
set to 1; otherwise, set to the current line -
\fIcount\fP.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Scroll Backward by Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<control>-Y
\fP
.fi
.RE
.sp
.LP
Display the line \fIcount\fP lines before the first line currently
displayed.
.LP
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.
.LP
\fICurrent line\fP: Unchanged if the previous current character is
displayed; otherwise, set to the first line displayed.
.LP
\fICurrent column\fP: Unchanged.
.SS Edit the Alternate File
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-^
\fP
.fi
.RE
.sp
This command shall be equivalent to the \fIex\fP \fBedit\fP command,
with the alternate
pathname as its argument. 
.SS Terminate Command or Input Mode
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<ESC>
\fP
.fi
.RE
.sp
.LP
If a partial \fIvi\fP command (as defined by at least one, non- \fIcount\fP
character) has been entered, discard the
\fIcount\fP and the command character(s).
.LP
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.
.LP
Otherwise, it shall be an error.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Unchanged.
.SS Search for tagstring
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-]
\fP
.fi
.RE
.sp
.LP
If the current character is not a word or <blank>, it shall be an
error.
.LP
This command shall be equivalent to the \fIex\fP \fBtag\fP command,
with the argument to
that command defined as follows.
.LP
If the current character is a <blank>:
.IP " 1." 4
Skip all <blank>s after the cursor up to the end of the line.
.LP
.IP " 2." 4
If the end of the line is reached, it shall be an error.
.LP
.LP
Then, the argument to the \fIex\fP \fBtag\fP 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
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<space>
.sp

\fP\fB[\fP\fIcount\fP\fB]\fP \fBl\fP  (ell)
.fi
.RE
.sp
.LP
If there are less than \fIcount\fP non- <newline>s after the cursor
on the current line, \fIcount\fP shall be adjusted
to the number of non- <newline>s after the cursor on the line.
.LP
If used as a motion command:
.IP " 1." 4
If the current or \fIcount\fPth character after the cursor is the
last non- <newline> in the line, the text region shall
be comprised of the current character up to and including the last
non- <newline> in the line. Otherwise, the text region
shall be from the current character up to, but not including, the
\fIcount\fPth character after the cursor.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
If there are no non- <newline>s after the current character on the
current line, it shall be an error.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to the last column that displays any portion
of the \fIcount\fPth character after the current
character.
.SS Replace Text with Results from Shell Command
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB!\fP \fImotion shell-commands\fP \fB<newline>
\fP
.fi
.RE
.sp
.LP
If the motion command is the \fB!\fP command repeated:
.IP " 1." 4
If the edit buffer is empty and no \fIcount\fP was supplied, the command
shall be the equivalent of the \fIex\fP \fB:read\fP \fB!\fP command,
with the text input, and no text shall be copied to any
buffer.
.LP
.IP " 2." 4
Otherwise:
.RS
.IP " a." 4
If there are less than \fIcount\fP -1 lines after the current line
in the edit buffer, it shall be an error.
.LP
.IP " b." 4
The text region shall be from the current line up to and including
the next \fIcount\fP -1 lines.
.LP
.RE
.LP
.LP
Otherwise, the text region shall be the lines in which any character
of the text region specified by the motion command
appear.
.LP
Any text copied to a buffer shall be in line mode.
.LP
This command shall be equivalent to the \fIex\fP \fB!\fP command for
the specified
lines.
.SS Move Cursor to End-of-Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB$
\fP
.fi
.RE
.sp
.LP
It shall be an error if there are less than ( \fIcount\fP -1) lines
after the current line in the edit buffer.
.LP
If used as a motion command:
.IP " 1." 4
If \fIcount\fP is 1:
.RS
.IP " a." 4
It shall be an error if the line is empty.
.LP
.IP " b." 4
Otherwise, the text region shall consist of all characters from the
starting cursor to the last non- <newline> in the
line, inclusive, and any text copied to a buffer shall be in character
mode.
.LP
.RE
.LP
.IP " 2." 4
Otherwise, if the starting cursor position is at or before the first
non- <blank> in the line, the text region shall
consist of the current and the next \fIcount\fP -1 lines, and any
text saved to a buffer shall be in line mode.
.LP
.IP " 3." 4
Otherwise, the text region shall consist of all characters from the
starting cursor to the last non- <newline> in the line
that is \fIcount\fP -1 lines forward from the current line, and any
text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the \fIcurrent line\fP + \fIcount\fP-1.
.LP
\fICurrent column\fP: The current column is set to the last display
line column of the last non- <newline> in the line,
or column position 1 if the line is empty.
.LP
The current column shall be adjusted to be on the last display line
column of the last non- <newline> of the current line
as subsequent commands change the current line, until a command changes
the current column.
.SS Move to Matching Character
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB%
\fP
.fi
.RE
.sp
.LP
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.
.LP
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.
.LP
Matching shall be determined as follows, for an open parenthesis:
.IP " 1." 4
Set a counter to 1.
.LP
.IP " 2." 4
Search forwards until a parenthesis is found or the end of the edit
buffer is reached.
.LP
.IP " 3." 4
If the end of the edit buffer is reached, it shall be an error.
.LP
.IP " 4." 4
If an open parenthesis is found, increment the counter by 1.
.LP
.IP " 5." 4
If a close parenthesis is found, decrement the counter by 1.
.LP
.IP " 6." 4
If the counter is zero, the current character is the matching character.
.LP
.LP
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.
.LP
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.
.LP
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- <blank> non- <newline> in the starting line, and the matching
cursor position was at or after the last non-
<blank> non- <newline> in the matching line, the text region shall
consist of the current line to the matching line,
inclusive, and any text copied to a buffer shall be in line mode.
.LP
.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- <blank> non- <newline> in the starting line, and the matching
cursor position was at or before the first non-
<blank> non- <newline> in the matching line, the text region shall
consist of the current line to the matching line,
inclusive, and any text copied to a buffer shall be in line mode.
.LP
.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.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the line where the matching character is
located.
.LP
\fICurrent column\fP: Set to the last column where any portion of
the matching character is displayed.
.SS Repeat Substitution
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB&
\fP
.fi
.RE
.sp
.LP
Repeat the previous substitution command. This command shall be equivalent
to the \fIex\fP
\fB&\fP command with the current line as its addresses, and without
\fIoptions\fP, \fIcount\fP, or \fIflags\fP.
.SS Return to Previous Context at Beginning of Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB'\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
It shall be an error if there is no line in the edit buffer marked
by \fIcharacter\fP.
.LP
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.
.LP
.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.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the line referenced by the mark.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Return to Previous Context
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB`\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
It shall be an error if the marked line is no longer in the edit buffer.
If the marked line no longer contains a character in
the saved numbered character position, it shall be as if the marked
position is the first non- <blank>.
.LP
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.
.LP
.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.
.LP
.IP " 3." 4
If the starting line is empty or the starting cursor is at or before
the first non- <blank> non- <newline> of the
starting line, and the marked cursor line is empty or the marked cursor
references the first 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.
.LP
.IP " 4." 4
Otherwise, if the marked cursor line is empty or the marked cursor
references a character at or before the first non-
<blank> non- <newline> of the marked cursor line, the region of text
shall be from the starting cursor to the last non-
<newline> of the line before the marked cursor line, inclusive, and
any text copied to a buffer shall be in character
mode.
.LP
.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.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the line referenced by the mark.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the character referenced by the mark is displayed.
.SS Return to Previous Section
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB[[
\fP
.fi
.RE
.sp
.LP
Move the cursor backward through the edit buffer to the first character
of the previous section boundary, \fIcount\fP
times.
.LP
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 \fIcount\fPth next boundary starts, and any text
copied to a buffer shall be in line mode.
.LP
.IP " 2." 4
If the boundary was the last line of the edit buffer or the last non-
<newline> of the last line of the edit buffer, the
text region shall consist of the last character in the edit buffer
up to and including the starting character, and any text saved
to a buffer shall be in character mode.
.LP
.IP " 3." 4
Otherwise, the text region shall consist of the starting character
up to but not including the first character in the
\fIcount\fPth next boundary, and any text copied to a buffer shall
be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the line where the \fIcount\fPth next boundary
in the edit buffer starts.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the first character of the \fIcount\fPth next boundary is
displayed, or column position 1 if the line is empty.
.SS Move to Next Section
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB]]
\fP
.fi
.RE
.sp
.LP
Move the cursor forward through the edit buffer to the first character
of the next section boundary, \fIcount\fP times.
.LP
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 \fIcount\fPth previous boundary starts, and any
text copied to a buffer shall be in line mode.
.LP
.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.
.LP
.IP " 3." 4
Otherwise, the text region shall consist of the first character in
the \fIcount\fPth previous section boundary up to but not
including the starting character, and any text copied to a buffer
shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the line where the \fIcount\fPth previous
boundary in the edit buffer starts.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the first character of the \fIcount\fPth previous
boundary is displayed, or column position 1 if the line is empty.
.SS Move to First Non-<blank> Position on Current Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB^
\fP
.fi
.RE
.sp
If used as a motion command: 
.IP " 1." 4
If the line has no non- <blank> non- <newline>s, or if the cursor
is at the first non- <blank> non-
<newline> of the line, it shall be an error.
.LP
.IP " 2." 4
If the cursor is before the first non- <blank> non- <newline> of the
line, the text region shall be comprised of the
current character, up to, but not including, the first non- <blank>
non- <newline> of the line.
.LP
.IP " 3." 4
If the cursor is after the first non- <blank> non- <newline> of the
line, the text region shall be from the
character before the starting cursor up to and including the first
non- <blank> non- <newline> of the line.
.LP
.IP " 4." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Current and Line Above
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB_
\fP
.fi
.RE
.sp
.LP
If there are less than \fIcount\fP -1 lines after the current line
in the edit buffer, it shall be an error.
.LP
If used as a motion command:
.IP " 1." 4
If \fIcount\fP is less than 2, the text region shall be the current
line.
.LP
.IP " 2." 4
Otherwise, the text region shall include the starting line and the
next \fIcount\fP -1 lines.
.LP
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to current line + \fIcount\fP -1.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Move Back to Beginning of Sentence
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB(
\fP
.fi
.RE
.sp
.LP
Move backward to the beginning of a sentence. This command shall be
equivalent to the \fB[[\fP command, with the exception that
sentence boundaries shall be used instead of section boundaries.
.SS Move Forward to Beginning of Sentence
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB)
\fP
.fi
.RE
.sp
.LP
Move forward to the beginning of a sentence. This command shall be
equivalent to the \fB]]\fP command, with the exception that
sentence boundaries shall be used instead of section boundaries.
.SS Move Back to Preceding Paragraph
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB{
\fP
.fi
.RE
.sp
.LP
Move back to the beginning of the preceding paragraph. This command
shall be equivalent to the \fB[[\fP command, with the
exception that paragraph boundaries shall be used instead of section
boundaries.
.SS Move Forward to Next Paragraph
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB}
\fP
.fi
.RE
.sp
.LP
Move forward to the beginning of the next paragraph. This command
shall be equivalent to the \fB]]\fP command, with the
exception that paragraph boundaries shall be used instead of section
boundaries.
.SS Move to Specific Column Position
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB|
\fP
.fi
.RE
.sp
.LP
For the purposes of this command, lines that are too long for the
current display and that have been folded shall be treated as
having a single, 1-based, number of columns.
.LP
If there are less than \fIcount\fP columns in which characters from
the current line are displayed on the screen, \fIcount\fP
shall be adjusted to be the last column in which any portion of the
line is displayed on the screen.
.LP
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 \fIcount\fPth column of the line, it shall be
an error.
.LP
.IP " 2." 4
If the cursor is before the \fIcount\fPth column of the line, the
text region shall be comprised of the current character, up
to but not including the character on the \fIcount\fPth column of
the line.
.LP
.IP " 3." 4
If the cursor is after the \fIcount\fPth column of the line, the text
region shall be from the character before the starting
cursor up to and including the character on the \fIcount\fPth column
of the line.
.LP
.IP " 4." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the character that is displayed in the \fIcount\fP column
of the line is displayed.
.SS Reverse Find Character
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB,
\fP
.fi
.RE
.sp
.LP
If the last \fBF\fP, \fBf\fP, \fBT\fP, or \fBt\fP command was \fBF\fP,
\fBf\fP, \fBT\fP, or \fBt\fP, this command shall
be equivalent to an \fBf\fP, \fBF\fP, \fBt\fP, or \fBT\fP command,
respectively, with the specified \fIcount\fP and the same
search character.
.LP
If there was no previous \fBF\fP, \fBf\fP, \fBT\fP, or \fBt\fP command,
it shall be an error.
.SS Repeat
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB.
\fP
.fi
.RE
.sp
.LP
Repeat the last \fB!\fP, \fB<\fP, \fB>\fP, \fBA\fP, \fBC\fP, \fBD\fP,
\fBI\fP, \fBJ\fP, \fBO\fP, \fBP\fP,
\fBR\fP, \fBS\fP, \fBX\fP, \fBY\fP, \fBa\fP, \fBc\fP, \fBd\fP, \fBi\fP,
\fBo\fP, \fBp\fP, \fBr\fP, \fBs\fP, \fBx\fP,
\fBy\fP, or \fB~\fP 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.
.LP
Repeated commands with associated motion commands shall repeat the
motion command as well; however, any specified \fIcount\fP
shall replace the \fIcount\fP(s) that were originally specified to
the repeated command or its associated motion command.
.LP
If the motion component of the repeated command is \fBf\fP, \fBF\fP,
\fBt\fP, or \fBT\fP, the repeated command shall not set
the remembered search character for the \fB;\fP and \fB,\fP commands.
.LP
If the repeated command is \fBp\fP or \fBP\fP, 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.
.LP
If the repeated character is a text input command, the input text
associated with that command is repeated literally:
.IP " *" 3
Input characters are neither macro or abbreviation-expanded.
.LP
.IP " *" 3
Input characters are not interpreted in any special way with the exception
that <newline>, <carriage-return>, and
<control>-T behave as described in Input Mode Commands in vi .
.LP
.LP
\fICurrent line\fP: Set as described for the repeated command.
.LP
\fICurrent column\fP: Set as described for the repeated command.
.SS Find Regular Expression
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB/
\fP
.fi
.RE
.sp
.LP
If the input line contains no non- <newline>s, it shall be equivalent
to a line containing only the last regular
expression encountered. The enhanced regular expressions supported
by \fIvi\fP are described in \fIRegular Expressions in ex\fP .
.LP
Otherwise, the line shall be interpreted as one or more regular expressions,
optionally followed by an address offset or a
\fIvi\fP \fBz\fP command.
.LP
If the regular expression is not the last regular expression on the
line, or if a line offset or \fBz\fP command is specified,
the regular expression shall be terminated by an unescaped \fB'/'\fP
character, which shall not be used as part of the regular
expression. If the regular expression is not the first regular expression
on the line, it shall be preceded by zero or more
<blank>s, a semicolon, zero or more <blank>s, and a leading \fB'/'\fP
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.
.LP
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 \fBwrapscan\fP 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.
.LP
An optional address offset (see \fIAddressing in ex\fP ) can be specified
after the last
regular expression by including a trailing \fB'/'\fP character after
the regular expression and specifying the address offset.
This offset will be from the line containing the match for the last
regular expression specified. It shall be an error if the line
offset would indicate a line address less than 1 or greater than the
last line in the edit buffer. An address offset of zero shall
be supported. It shall be an error to follow the address offset with
any other characters than <blank>s.
.LP
If not used as a motion command, an optional \fBz\fP command (see
Redraw Window ) can be
specified after the last regular expression by including a trailing
\fB'/'\fP character after the regular expression, zero or
more <blank>s, a \fB'z'\fP , zero or more <blank>s, an optional new
\fBwindow\fP edit option value, zero or more
<blank>s, and a location character. The effect shall be as if the
\fBz\fP command was executed after the \fB/\fP command.
It shall be an error to follow the \fBz\fP command with any other
characters than <blank>s.
.LP
The remembered search direction shall be set to forward.
.LP
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.
.LP
.IP " 2." 4
If any address offset is specified, the last match shall be adjusted
by the specified offset as described previously.
.LP
.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.
.LP
.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.
.LP
.IP " 5." 4
Otherwise, if the starting line is empty or the starting cursor is
at or before the first non- <blank> non-
<newline> of the starting line, and the last match line is empty or
the last match starts at the first character of the last
match line, the text region shall consist of all lines containing
characters from the starting cursor to the line before the last
match line, inclusive, and any text copied to a buffer shall be in
line mode.
.LP
.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- <blank>
non- <newline> of the last match line, the region of text shall be
from the current cursor to the last non- <newline>
of the line before the last match line, inclusive, and any text copied
to a buffer shall be in character mode.
.LP
.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.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: If a match is found, set to the last matched line
plus the address offset, if any; otherwise,
unchanged.
.LP
\fICurrent column\fP: 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
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB0 \fP (zero)
.fi
.RE
.sp
.LP
Move to the first character on the current line. The character \fB'0'\fP
shall not be interpreted as a command if it is
immediately preceded by a digit.
.LP
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.
.LP
.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.
.LP
.IP " 3." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: 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
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB:
\fP
.fi
.RE
.sp
.LP
Execute one or more \fIex\fP commands.
.LP
If any portion of the screen other than the last line of the screen
was overwritten by any \fIex\fP command (except \fBshell\fP), \fIvi\fP
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.
.LP
If the next character entered is a \fB':'\fP , another \fIex\fP command
shall be accepted
and executed. Any other character shall cause the screen to be refreshed
and \fIvi\fP shall return to command mode.
.LP
\fICurrent line\fP: As specified for the \fIex\fP command.
.LP
\fICurrent column\fP: As specified for the \fIex\fP command.
.SS Repeat Find
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB;
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the last \fBF\fP, \fBf\fP, \fBT\fP,
or \fBt\fP command, with the specified \fIcount\fP,
and with the same search character used for the last \fBF\fP, \fBf\fP,
\fBT\fP, or \fBt\fP command. If there was no previous
\fBF\fP, \fBf\fP, \fBT\fP, or \fBt\fP command, it shall be an error.
.SS Shift Left
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB<\fP \fImotion\fP
.fi
.RE
.sp
.LP
If the motion command is the \fB<\fP command repeated:
.IP " 1." 4
If there are less than \fIcount\fP -1 lines after the current line
in the edit buffer, it shall be an error.
.LP
.IP " 2." 4
The text region shall be from the current line, up to and including
the next \fIcount\fP -1 lines.
.LP
.LP
Shift any line in the text region specified by the \fIcount\fP and
motion command one shiftwidth (see the \fIex\fP \fBshiftwidth\fP option)
toward the start of the line, as described by the \fIex\fP \fB<\fP
command. The unshifted lines shall be copied to the unnamed buffer
in line
mode.
.LP
\fICurrent line\fP: 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.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Shift Right
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB>\fP \fImotion\fP
.fi
.RE
.sp
.LP
If the motion command is the \fB>\fP command repeated:
.IP " 1." 4
If there are less than \fIcount\fP -1 lines after the current line
in the edit buffer, it shall be an error.
.LP
.IP " 2." 4
The text region shall be from the current line, up to and including
the next \fIcount\fP -1 lines.
.LP
.LP
Shift any line with characters in the text region specified by the
\fIcount\fP and motion command one shiftwidth (see the \fIex\fP \fBshiftwidth\fP
option) away from the start of the line, as described by the \fIex\fP
\fB>\fP command. The unshifted lines shall be copied into the unnamed
buffer in line
mode.
.LP
\fICurrent line\fP: 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.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Scan Backwards for Regular Expression
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB?
\fP
.fi
.RE
.sp
.LP
Scan backwards; the \fB?\fP command shall be equivalent to the \fB/\fP
command (see Find Regular
Expression ) with the following exceptions:
.IP " 1." 4
The input prompt shall be a \fB'?'\fP .
.LP
.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).
.LP
.IP " 3." 4
The search direction shall be from the cursor toward the beginning
of the edit buffer, and the \fBwrapscan\fP edit option shall
affect whether the search wraps to the end of the edit buffer and
continues.
.LP
.IP " 4." 4
The remembered search direction shall be set to backward.
.LP
.SS Execute
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB@\fP\fIbuffer\fP
.fi
.RE
.sp
.LP
If the \fIbuffer\fP is specified as \fB@\fP, the last buffer executed
shall be used. If no previous buffer has been executed,
it shall be an error.
.LP
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.
.LP
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.
.LP
If a \fIcount\fP is specified, behave as if that count were entered
as user input before the characters from the \fB@\fP
buffer were entered.
.LP
\fICurrent line\fP: As specified for the individual commands.
.LP
\fICurrent column\fP: As specified for the individual commands.
.SS Reverse Case
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fB~
\fP
.fi
.RE
.sp
.LP
Reverse the case of the current character and the next \fIcount\fP
-1 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.
.LP
If there are less than \fIcount\fP -1 characters after the cursor
in the edit buffer, \fIcount\fP shall be adjusted to the
number of characters after the cursor in the edit buffer minus 1.
.LP
For the purposes of this command, the next character after the last
non- <newline> on the line shall be the next character
in the edit buffer.
.LP
\fICurrent line\fP: Set to the line including the ( \fIcount\fP-1)th
character after the cursor.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the ( \fIcount\fP-1)th character after the cursor is
displayed.
.SS Append
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBa
\fP
.fi
.RE
.sp
.LP
Enter text input mode after the current cursor position. No characters
already in the edit buffer shall be affected by this
command. A \fIcount\fP shall cause the input text to be appended \fIcount\fP
-1 more times to the end of the input.
.LP
\fICurrent line/column\fP: As specified for the text input commands
(see Input Mode Commands in
vi ).
.SS Append at End-of-Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBA
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIvi\fP command:
.sp
.RS
.nf

\fB$\fP \fB[\fP \fIcount\fP \fB]\fP \fBa
\fP
.fi
.RE
.LP
(see Append ).
.SS Move Backward to Preceding Word
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBb
\fP
.fi
.RE
.sp
.LP
With the exception that words are used as the delimiter instead of
bigwords, this command shall be equivalent to the \fBB\fP
command.
.SS Move Backward to Preceding Bigword
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBB
\fP
.fi
.RE
.sp
.LP
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
\fIcount\fP bigwords begin between the cursor and the start of the
edit buffer, \fIcount\fP shall be adjusted to the number of
bigword beginnings between the cursor and the start of the edit buffer.
.LP
If used as a motion command:
.IP " 1." 4
The text region shall be from the first character of the \fIcount\fPth
previous bigword beginning up to but not including the
cursor character.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the line containing the \fIcurrent column\fP.
.LP
\fICurrent column\fP: Set to the last column upon which any part of
the first character of the \fIcount\fPth previous bigword
is displayed.
.SS Change
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBc\fP \fImotion\fP
.fi
.RE
.sp
.LP
If the motion command is the \fBc\fP command repeated:
.IP " 1." 4
The buffer text shall be in line mode.
.LP
.IP " 2." 4
If there are less than \fIcount\fP -1 lines after the current line
in the edit buffer, it shall be an error.
.LP
.IP " 3." 4
The text region shall be from the current line up to and including
the next \fIcount\fP -1 lines.
.LP
.LP
Otherwise, the buffer text mode and text region shall be as specified
by the motion command.
.LP
The replaced text shall be copied into \fIbuffer\fP, 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.
.LP
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.
.LP
.IP " 2." 4
If the \fBautoindent\fP edit option is set, \fBautoindent\fP characters
equal to the \fBautoindent\fP characters on the first
line deleted shall be inserted as if entered by the user.
.LP
.LP
Otherwise, if characters from more than one line are in the region
of text:
.IP " 1." 4
The text shall be deleted.
.LP
.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.
.LP
.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.
.LP
.LP
Otherwise:
.IP " 1." 4
If the glyph for \fB'$'\fP is smaller than the region, the end of
the region shall be marked with a \fB'$'\fP .
.LP
.IP " 2." 4
The editor shall enter text input mode, overwriting the region of
text.
.LP
.LP
\fICurrent line/column\fP: As specified for the text input commands
(see Input Mode Commands in
vi ).
.SS Change to End-of-Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBC
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIvi\fP command:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBc$
\fP
.fi
.RE
.LP
See the \fBc\fP command.
.SS Delete
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBd\fP \fImotion\fP
.fi
.RE
.sp
.LP
If the motion command is the \fBd\fP command repeated:
.IP " 1." 4
The buffer text shall be in line mode.
.LP
.IP " 2." 4
If there are less than \fIcount\fP -1 lines after the current line
in the edit buffer, it shall be an error.
.LP
.IP " 3." 4
The text region shall be from the current line up to and including
the next \fIcount\fP -1 lines.
.LP
.LP
Otherwise, the buffer text mode and text region shall be as specified
by the motion command.
.LP
If in open mode, and the current line is deleted, and the line remains
on the display, an \fB'@'\fP character shall be
displayed as the first glyph of that line.
.LP
Delete the region of text into \fIbuffer\fP, 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.
.LP
\fICurrent line\fP: 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.
.LP
\fICurrent column\fP:
.IP " 1." 4
If the line is empty, set to column position 1.
.LP
.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
.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.
.LP
.IP " b." 4
Otherwise, set to the last column in which any portion of any character
in the line is displayed.
.LP
.RE
.LP
.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.
.LP
.IP " 4." 4
Otherwise, set to the last column in which any portion of any character
in the line is displayed.
.LP
.SS Delete to End-of-Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB]\fP \fBD
\fP
.fi
.RE
.sp
.LP
Delete the text from the current position to the end of the current
line; equivalent to the \fIvi\fP command:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB]\fP \fBd$
\fP
.fi
.RE
.SS Move to End-of-Word
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBe
\fP
.fi
.RE
.sp
.LP
With the exception that words are used instead of bigwords as the
delimiter, this command shall be equivalent to the \fBE\fP
command.
.SS Move to End-of-Bigword
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBE
\fP
.fi
.RE
.sp
.LP
If the edit buffer is empty it shall be an error. If less than \fIcount\fP
bigwords end between the cursor and the end of the
edit buffer, \fIcount\fP shall be adjusted to the number of bigword
endings between the cursor and the end of the edit buffer.
.LP
If used as a motion command:
.IP " 1." 4
The text region shall be from the last character of the \fIcount\fPth
next bigword up to and including the cursor
character.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to the line containing the current column.
.LP
\fICurrent column\fP: Set to the last column upon which any part of
the last character of the \fIcount\fPth next bigword is
displayed.
.SS Find Character in Current Line (Forward)
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBf\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
It shall be an error if \fIcount\fP occurrences of the character do
not occur after the cursor in the line.
.LP
If used as a motion command:
.IP " 1." 4
The text range shall be from the cursor character up to and including
the \fIcount\fPth occurrence of the specified character
after the cursor.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the \fIcount\fPth occurrence of the specified character
after the cursor appears in the line.
.SS Find Character in Current Line (Reverse)
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBF\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
It shall be an error if \fIcount\fP occurrences of the character do
not occur before the cursor in the line.
.LP
If used as a motion command:
.IP " 1." 4
The text region shall be from the \fIcount\fPth occurrence of the
specified character before the cursor, up to, but not
including the cursor character.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the \fIcount\fPth occurrence of the specified character
before the cursor appears in the line.
.SS Move to Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBG
\fP
.fi
.RE
.sp
.LP
If \fIcount\fP is not specified, it shall default to the last line
of the edit buffer. If \fIcount\fP is greater than the last
line of the edit buffer, it shall be an error.
.LP
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.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in line mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Set to \fIcount\fP if \fIcount\fP is specified;
otherwise, the last line.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Move to Top of Screen
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBH
\fP
.fi
.RE
.sp
.LP
If the beginning of the line \fIcount\fP greater than the first line
of which any portion appears on the display does not
exist, it shall be an error.
.LP
If used as a motion command:
.IP " 1." 4
If in open mode, the text region shall be the current line.
.LP
.IP " 2." 4
Otherwise, the text region shall be from the starting line up to and
including (the first line of the display + \fIcount\fP
-1).
.LP
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.LP
.LP
If not used as a motion command:
.LP
If in open mode, this command shall set the current column to non-
<blank> and do nothing else.
.LP
Otherwise, it shall set the current line and current column as follows.
.LP
\fICurrent line\fP: Set to (the first line of the display + \fIcount\fP
-1).
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Insert Before Cursor
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBi
\fP
.fi
.RE
.sp
.LP
Enter text input mode before the current cursor position. No characters
already in the edit buffer shall be affected by this
command. A \fIcount\fP shall cause the input text to be appended \fIcount\fP
-1 more times to the end of the input.
.LP
\fICurrent line/column\fP: As specified for the text input commands
(see Input Mode Commands in
vi ).
.SS Insert at Beginning of Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBI
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIvi\fP command ^[ \fIcount\fP]
\fBi\fP.
.SS Join
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBJ
\fP
.fi
.RE
.sp
.LP
If the current line is the last line in the edit buffer, it shall
be an error.
.LP
This command shall be equivalent to the \fIex\fP \fBjoin\fP command
with no addresses, and
an \fIex\fP command \fIcount\fP value of 1 if \fIcount\fP was not
specified or if a
\fIcount\fP of 1 was specified, and an \fIex\fP command \fIcount\fP
value of \fIcount\fP -1
for any other value of \fIcount\fP, except that the current line and
column shall be set as follows.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: The last column in which any portion of the
character following the last character in the initial line is
displayed, or the last non- <newline> in the line if no characters
were appended.
.SS Move to Bottom of Screen
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBL
\fP
.fi
.RE
.sp
.LP
If the beginning of the line \fIcount\fP less than the last line of
which any portion appears on the display does not exist, it
shall be an error.
.LP
If used as a motion command:
.IP " 1." 4
If in open mode, the text region shall be the current line.
.LP
.IP " 2." 4
Otherwise, the text region shall include all lines from the starting
cursor line to (the last line of the display -(
\fIcount\fP -1)).
.LP
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.LP
.LP
If not used as a motion command:
.IP " 1." 4
If in open mode, this command shall set the current column to non-
<blank> and do nothing else.
.LP
.IP " 2." 4
Otherwise, it shall set the current line and current column as follows.
.LP
.LP
\fICurrent line\fP: Set to (the last line of the display -( \fIcount\fP
-1)).
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Mark Position
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBm\fP \fIletter\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIex\fP \fBmark\fP command
with the specified
character as an argument.
.SS Move to Middle of Screen
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBM
\fP
.fi
.RE
.sp
.LP
The middle line of the display shall be calculated as follows:
.sp
.RS
.nf

\fB(the top line of the display) + (((number of lines displayed) +1) /2) -1
\fP
.fi
.RE
.LP
If used as a motion command:
.IP " 1." 4
If in open mode, the text region shall be the current line.
.LP
.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.
.LP
.IP " 3." 4
Any text copied to a buffer shall be in line mode.
.LP
.LP
If not used as a motion command:
.LP
If in open mode, this command shall set the current column to non-
<blank> and do nothing else.
.LP
Otherwise, it shall set the current line and current column as follows.
.LP
\fICurrent line\fP: Set to the middle line of the display.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Repeat Regular Expression Find (Forward)
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBn
\fP
.fi
.RE
.sp
.LP
If the remembered search direction was forward, the \fBn\fP command
shall be equivalent to the \fIvi\fP \fB/\fP command with
no characters entered by the user. Otherwise, it shall be equivalent
to the \fIvi\fP \fB?\fP command with no characters entered
by the user.
.LP
If the \fBn\fP command is used as a motion command for the \fB!\fP
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 \fB'!'\fP character as the text input.
.SS Repeat Regular Expression Find (Reverse)
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBN
\fP
.fi
.RE
.sp
.LP
Scan for the next match of the last pattern given to \fB/\fP or \fB?\fP,
but in the reverse direction; this is the reverse of
\fBn\fP.
.LP
If the remembered search direction was forward, the \fBN\fP command
shall be equivalent to the \fIvi\fP \fB?\fP command with
no characters entered by the user. Otherwise, it shall be equivalent
to the \fIvi\fP \fB/\fP command with no characters entered
by the user. If the \fBN\fP command is used as a motion command for
the \fB!\fP 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 \fB!\fP character as the text input.
.SS Insert Empty Line Below
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBo
\fP
.fi
.RE
.sp
.LP
Enter text input mode in a new line appended after the current line.
A \fIcount\fP shall cause the input text to be appended
\fIcount\fP -1 more times to the end of the already added text, each
time starting on a new, appended line.
.LP
\fICurrent line/column\fP: As specified for the text input commands
(see Input Mode Commands in
vi ).
.SS Insert Empty Line Above
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBO
\fP
.fi
.RE
.sp
.LP
Enter text input mode in a new line inserted before the current line.
A \fIcount\fP shall cause the input text to be appended
\fIcount\fP -1 more times to the end of the already added text, each
time starting on a new, appended line.
.LP
\fICurrent line/column\fP: As specified for the text input commands
(see Input Mode Commands in
vi ).
.SS Put from Buffer Following
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB]\fP \fBp
\fP
.fi
.RE
.sp
.LP
If no \fIbuffer\fP is specified, the unnamed buffer shall be used.
.LP
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 \fIcount\fP shall cause the buffer
text to be appended \fIcount\fP -1 more times to the end of
the already added text, each time starting on a new, appended line.
.LP
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 \fIcount\fP shall cause the buffer text to be
appended \fIcount\fP -1 more times to the end of the already added
text, each time starting after the last added character.
.LP
\fICurrent line\fP: If the buffer text is in line mode, set the line
to line +1; otherwise, unchanged.
.LP
\fICurrent column\fP: If the buffer text is in line mode:
.IP " 1." 4
If there is a non- <blank> in the first line of the buffer, set to
the last column on which any portion of the first non-
<blank> in the line is displayed.
.LP
.IP " 2." 4
If there is no non- <blank> in the first line of the buffer, set to
the last column on which any portion of the last non-
<newline> in the first line of the buffer is displayed.
.LP
.LP
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.
.LP
.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.
.LP
.IP " 3." 4
Otherwise, set to the first column on which any portion of the first
character from the buffer is displayed.
.LP
.SS Put from Buffer Before
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB]\fP \fBP
\fP
.fi
.RE
.sp
.LP
If no \fIbuffer\fP is specified, the unnamed buffer shall be used.
.LP
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 \fIcount\fP shall cause the buffer
text to be appended \fIcount\fP -1 more times to the end of
the already added text, each time starting on a new, appended line.
.LP
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 \fIcount\fP shall cause the buffer text to
be appended \fIcount\fP -1 more times to the end of the already added
text, each time starting after the last added character.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: If the buffer text is in line mode:
.IP " 1." 4
If there is a non- <blank> in the first line of the buffer, set to
the last column on which any portion of that character
is displayed.
.LP
.IP " 2." 4
If there is no non- <blank> in the first line of the buffer, set to
the last column on which any portion of the last non-
<newline> in the first line of the buffer is displayed.
.LP
.LP
If the buffer text is in character mode:
.IP " 1." 4
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.
.LP
.IP " 2." 4
Otherwise, set to the first column on which any portion of the first
character from the buffer is displayed.
.LP
.SS Enter ex Mode
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBQ
\fP
.fi
.RE
.sp
.LP
Leave visual or open mode and enter \fIex\fP command mode.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Unchanged.
.SS Replace Character
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBr\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
Replace the \fIcount\fP characters at and after the cursor with the
specified character. If there are less than \fIcount\fP
non- <newline>s at and after the cursor on the line, it shall be an
error.
.LP
If character is <control>-V, any next character other than the <newline>
shall be stripped of any special meaning
and used as a literal character.
.LP
If character is <ESC>, no replacement shall be made and the current
line and current column shall be unchanged.
.LP
If character is <carriage-return> or <newline>, \fIcount\fP new lines
shall be appended to the current line. All
but the last of these lines shall be empty. \fIcount\fP 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 \fBautoindent\fP edit option
is set, they shall be preceded by the same number of \fBautoindent\fP
characters found on the line from which the command was
executed.
.LP
\fICurrent line\fP: Unchanged unless the replacement character is
a <carriage-return> or <newline>, in which case
it shall be set to line + \fIcount\fP.
.LP
\fICurrent column\fP: Set to the last column position on which a portion
of the last replaced character is displayed, or if the
replacement character caused new lines to be created, set to non-
<blank>.
.SS Replace Characters
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBR
\fP
.fi
.RE
.sp
.LP
Enter text input mode at the current cursor position possibly replacing
text on the current line. A \fIcount\fP shall cause the
input text to be appended \fIcount\fP -1 more times to the end of
the input.
.LP
\fICurrent line/column\fP: As specified for the text input commands
(see Input Mode Commands in
vi ).
.SS Substitute Character
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBs
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIvi\fP command:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBc<space>
\fP
.fi
.RE
.SS Substitute Lines
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBS
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIvi\fP command:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBc_
\fP
.fi
.RE
.SS Move Cursor to Before Character (Forward)
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBt\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
It shall be an error if \fIcount\fP occurrences of the character do
not occur after the cursor in the line.
.LP
If used as a motion command:
.IP " 1." 4
The text region shall be from the cursor up to but not including the
\fIcount\fPth occurrence of the specified character after
the cursor.
.LP
.IP " 2." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the character before the \fIcount\fPth occurrence of the
specified character after the cursor appears in the line.
.SS Move Cursor to After Character (Reverse)
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBT\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
It shall be an error if \fIcount\fP occurrences of the character do
not occur before the cursor in the line.
.LP
If used as a motion command:
.IP " 1." 4
If the character before the cursor is the specified character, it
shall be an error.
.LP
.IP " 2." 4
The text region shall be from the character before the cursor up to
but not including the \fIcount\fPth occurrence of the
specified character before the cursor.
.LP
.IP " 3." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
If not used as a motion command:
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to the last column in which any portion
of the character after the \fIcount\fPth occurrence of the
specified character before the cursor appears in the line.
.SS Undo
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBu
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIex\fP \fBundo\fP command
except that the current
line and current column shall be set as follows:
.LP
\fICurrent line\fP: 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.
.LP
\fICurrent column\fP: If undoing an \fIex\fP command, set to the first
non-
<blank>.
.LP
Otherwise, if undoing a text input command:
.IP " 1." 4
If the command was a \fBC\fP, \fBc\fP, \fBO\fP, \fBo\fP, \fBR\fP,
\fBS\fP, or \fBs\fP command, the current column shall
be set to the value it held when the text input command was entered.
.LP
.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- <newline>s follow the text deleted from this line, set to the
last column in which any portion of the last non-
<newline> in the line is displayed, or 1 if the line is empty.
.LP
.LP
Otherwise, if a single line was modified (that is, not added or deleted)
by the \fBu\fP 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.
.LP
.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- <newline>s follow the deleted text, set to the last column
in which any portion of the last non- <newline>
in the line is displayed, or 1 if the line is empty.
.LP
.LP
Otherwise, set to non- <blank>.
.SS Undo Current Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBU
\fP
.fi
.RE
.sp
.LP
Restore the current line to its state immediately before the most
recent time that it became the current line.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: 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
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBw
\fP
.fi
.RE
.sp
.LP
With the exception that words are used as the delimiter instead of
bigwords, this command shall be equivalent to the \fBW\fP
command.
.SS Move to Beginning of Bigword
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBW
\fP
.fi
.RE
.sp
.LP
If the edit buffer is empty, it shall be an error. If there are less
than \fIcount\fP bigwords between the cursor and the end
of the edit buffer, \fIcount\fP shall be adjusted to move the cursor
to the last bigword in the edit buffer.
.LP
If used as a motion command:
.IP " 1." 4
If the associated command is \fBc\fP, \fIcount\fP 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.
.LP
.IP " 2." 4
If there are less than \fIcount\fP 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.
.LP
.IP " 3." 4
If there are <blank>s or an end-of-line that precede the \fIcount\fPth
bigword, and the associated command is \fBc\fP,
the region of text shall be up to and including the last character
before the preceding <blank>s or end-of-line.
.LP
.IP " 4." 4
If there are <blank>s or an end-of-line that precede the bigword,
and the associated command is \fBd\fP or \fBy\fP, the
region of text shall be up to and including the last <blank> before
the start of the bigword or end-of-line.
.LP
.IP " 5." 4
Any text copied to a buffer shall be in character mode.
.LP
.LP
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.
.LP
.LP
\fICurrent line\fP: Set to the line containing the current column.
.LP
\fICurrent column\fP: Set to the last column in which any part of
the first character of the \fIcount\fPth next bigword is
displayed.
.SS Delete Character at Cursor
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBx
\fP
.fi
.RE
.sp
.LP
Delete the \fIcount\fP characters at and after the current character
into \fIbuffer\fP, if specified, and into the unnamed
buffer.
.LP
If the line is empty, it shall be an error. If there are less than
\fIcount\fP non- <newline>s at and after the cursor on
the current line, \fIcount\fP shall be adjusted to the number of non-
<newline>s at and after the cursor.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: If the line is empty, set to column position
1. Otherwise, if there were \fIcount\fP or less non-
<newline>s at and after the cursor on the current line, set to the
last column that displays any part of the last non-
<newline> of the line. Otherwise, unchanged.
.SS Delete Character Before Cursor
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBX
\fP
.fi
.RE
.sp
.LP
Delete the \fIcount\fP characters before the current character into
\fIbuffer\fP, if specified, and into the unnamed
buffer.
.LP
If there are no characters before the current character on the current
line, it shall be an error. If there are less than
\fIcount\fP previous characters on the current line, \fIcount\fP shall
be adjusted to the number of previous characters on the
line.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to (current column - the width of the deleted
characters).
.SS Yank
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBy\fP \fImotion\fP
.fi
.RE
.sp
.LP
Copy (yank) the region of text into \fIbuffer\fP, if specified, and
into the unnamed buffer.
.LP
If the motion command is the \fBy\fP command repeated:
.IP " 1." 4
The buffer shall be in line mode.
.LP
.IP " 2." 4
If there are less than \fIcount\fP -1 lines after the current line
in the edit buffer, it shall be an error.
.LP
.IP " 3." 4
The text region shall be from the current line up to and including
the next \fIcount\fP -1 lines.
.LP
.LP
Otherwise, the buffer text mode and text region shall be as specified
by the motion command.
.LP
\fICurrent line\fP: 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.
.LP
\fICurrent column\fP:
.IP " 1." 4
If the motion was from the current cursor position toward the end
of the edit buffer, unchanged.
.LP
.IP " 2." 4
Otherwise, if the current line is empty, set to column position 1.
.LP
.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.
.LP
.SS Yank Current Line
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBY
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIvi\fP command:
.sp
.RS
.nf

\fB[\fP\fIbuffer\fP\fB][\fP\fIcount\fP\fB]\fP \fBy_
\fP
.fi
.RE
.SS Redraw Window
.LP
If in open mode, the \fBz\fP command shall have the Synopsis:
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIcount\fP\fB]\fP \fBz
\fP
.fi
.RE
.sp
.LP
If \fIcount\fP is not specified, it shall default to the \fBwindow\fP
edit option -1. The \fBz\fP command shall be equivalent
to the \fIex\fP \fBz\fP command, with a type character of \fB=\fP
and a \fIcount\fP of
\fIcount\fP -2, except that the current line and current column shall
be set as follows, and the \fBwindow\fP edit option shall
not be affected. If the calculation for the \fIcount\fP argument would
result in a negative number, the \fIcount\fP argument to
the \fIex\fP \fBz\fP command shall be zero. A blank line shall be
written after the last line
is written.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Unchanged.
.LP
If not in open mode, the \fBz\fP command shall have the following
Synopsis:
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB[\fP\fIline\fP\fB]\fP \fBz\fP \fB[\fP\fIcount\fP\fB]\fP \fIcharacter\fP
.fi
.RE
.sp
.LP
If \fIline\fP is not specified, it shall default to the current line.
If \fIline\fP 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.
.LP
If \fIcount\fP is specified, the value of the \fBwindow\fP edit option
shall be set to \fIcount\fP (as described in the \fIex\fP \fBwindow\fP
command), and the screen shall be redrawn.
.LP
\fIline\fP shall be placed as specified by the following characters:
.TP 7
<newline>,\ <carriage-return>
.sp
Place the beginning of the line on the first line of the display.
.TP 7
\fB\&.\fP
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 \fBM\fP command.
.TP 7
\fB-\fP
Place an unspecified portion of the line on the last line of the display.
.TP 7
\fB+\fP
If \fIline\fP was specified, equivalent to the <newline> case. If
\fIline\fP 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.
.TP 7
\fB^\fP
If \fIline\fP 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. 
.LP
Otherwise, display a screen where the last line of the display shall
contain an unspecified portion of (current first line -1).
If this calculation results in a line before the beginning of the
edit buffer, it shall be an error.
.sp
.LP
\fICurrent line\fP: If \fIline\fP and the \fB'^'\fP 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 -1).
.LP
.IP " 2." 4
Otherwise, set to the last line of the display.
.LP
.LP
If \fIline\fP and the \fB'+'\fP character were specified, set to the
first line of the display.
.LP
Otherwise, if \fIline\fP was specified, set to \fIline\fP.
.LP
Otherwise, unchanged.
.LP
\fICurrent column\fP: Set to non- <blank>.
.SS Exit
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBZZ
\fP
.fi
.RE
.sp
.LP
This command shall be equivalent to the \fIex\fP \fBxit\fP command
with no addresses,
trailing \fB!\fP, or filename (see the \fIex\fP \fBxit\fP command).
.SS Input Mode Commands in vi
.LP
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
.LP
Characters in this category shall not be modified during text input
mode.
.LP
.IP " 2." 4
\fBautoindent\fP characters
.LP
\fBautoindent\fP 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, \fBO\fP or \fBo\fP (see the \fIex\fP \fBautoindent\fP
command), as if entered
by the user.
.LP
It shall be possible to erase \fBautoindent\fP characters with the
<control>-D command; it is unspecified whether they
can be erased by <control>-H, <control>-U, and <control>-W characters.
Erasing any \fBautoindent\fP character
turns the glyph into erase-columns and deletes the character from
the edit buffer, but does not change its representation on the
screen.
.LP
.IP " 3." 4
Text input characters
.LP
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.
.LP
Each text input character entered by the user (that does not have
a special meaning) shall be treated as follows:
.RS
.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.
.LP
.IP " b." 4
If there are no erase-columns on the screen, the text input command
was the \fBR\fP 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
\fBslowopen\fP edit option is not set, the corresponding glyph on
the screen shall become erase-columns.
.LP
.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.)
.LP
.IP " d." 4
If additional display line columns are needed to display the text
input character:
.RS
.IP " 1." 4
If the \fBslowopen\fP edit option is set, the text input characters
shall be displayed on subsequent display line columns,
overwriting any characters displayed in those columns.
.LP
.IP " 2." 4
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.
.LP
.RE
.LP
.RE
.LP
.IP " 4." 4
Erase-columns
.LP
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.
.LP
Erase-columns are initially the region of text specified by the \fBc\fP
command (see Change );
however, erasing \fBautoindent\fP or text input characters causes
the glyphs of the erased characters to be treated as
erase-columns.
.LP
.IP " 5." 4
Characters following the text region for the \fBc\fP command, or the
text input entry point for all other commands
.LP
Characters in this category shall not be modified during text input
mode, except as specified in category 3.b. for the \fBR\fP
text input command, or as <blank>s deleted when a <newline> or <carriage-return>
is entered.
.LP
.LP
It is unspecified whether it is an error to attempt to erase past
the beginning of a line that was created by the entry of a
<newline> or <carriage-return> during text input mode. If it is not
an error, the editor shall behave as if the erasing
character was entered immediately after the last text input character
entered on the previous line, and all of the non-
<newline>s on the current line shall be treated as erase-columns.
.LP
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
.LP
.IP " 2." 4
Otherwise, if the \fBslowopen\fP edit option is set, on the first
display line column after the last character in the first,
second, or third categories, if one exists
.LP
.IP " 3." 4
Otherwise, the first column that displays any part of the first character
in the fifth category, if one exists
.LP
.IP " 4." 4
Otherwise, the display line column after the last character in the
first, second, or third categories, if one exists
.LP
.IP " 5." 4
Otherwise, on column position 1
.LP
.LP
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 \fBslowopen\fP edit
option is not set, the current cursor character shall always be
updated.
.LP
The following specifications are for command characters entered during
text input mode.
.SS NUL
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fBNUL
\fP
.fi
.RE
.sp
.LP
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
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-D
\fP
.fi
.RE
.sp
.LP
The <control>-D character shall have no special meaning when in text
input mode for a line-oriented command (see Command Descriptions in
vi ).
.LP
This command need not be supported on block-mode terminals.
.LP
If the cursor does not follow an \fBautoindent\fP character, or an
\fBautoindent\fP character and a \fB'0'\fP or
\fB'^'\fP character:
.IP " 1." 4
If the cursor is in column position 1, the <control>-D character shall
be discarded and no further action taken.
.LP
.IP " 2." 4
Otherwise, the <control>-D character shall have no special meaning.
.LP
.LP
If the last input character was a \fB'0'\fP , the cursor shall be
moved to column position 1.
.LP
Otherwise, if the last input character was a \fB'^'\fP , the cursor
shall be moved to column position 1. In addition, the
\fBautoindent\fP level for the next input line shall be derived from
the same line from which the \fBautoindent\fP level for the
current input line was derived.
.LP
Otherwise, the cursor shall be moved back to the column after the
previous shiftwidth (see the \fIex\fP \fBshiftwidth\fP command) boundary.
.LP
All of the glyphs on columns between the starting cursor position
and (inclusively) the ending cursor position shall become
erase-columns as described in Input Mode Commands in vi .
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to 1 if the <control>-D was preceded by
a \fB'^'\fP or \fB'0'\fP ; otherwise, set to
(column -1) -((column -2) % \fBshiftwidth\fP).
.SS <control>-H
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-H
\fP
.fi
.RE
.sp
.LP
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.
.LP
If there are characters other than \fBautoindent\fP characters that
have been input on the current line before the cursor, the
cursor shall move back one character.
.LP
Otherwise, if there are \fBautoindent\fP characters on the current
line before the cursor, it is implementation-defined whether
the <control>-H command is an error or if the cursor moves back one
\fBautoindent\fP character.
.LP
Otherwise, if the cursor is in column position 1 and there are previous
lines that have been input, it is implementation-defined
whether the <control>-H command is an error or if it is equivalent
to entering <control>-H after the last input
character on the previous input line.
.LP
Otherwise, it shall be an error.
.LP
All of the glyphs on columns between the starting cursor position
and (inclusively) the ending cursor position shall become
erase-columns as described in Input Mode Commands in vi .
.LP
The current erase character (see \fIstty\fP) shall cause an equivalent
action to the
<control>-H command, unless the previously inserted character was
a backslash, in which case it shall be as if the literal
current erase character had been inserted instead of the backslash.
.LP
\fICurrent line\fP: Unchanged, unless previously input lines are erased,
in which case it shall be set to line -1.
.LP
\fICurrent column\fP: Set to the first column that displays any portion
of the character backed up over.
.SS <newline>
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<newline>
.sp

<carriage-return>
.sp

<control>-J
.sp

<control>-M
\fP
.fi
.RE
.sp
.LP
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.
.LP
Otherwise, terminate the current line. If there are no characters
other than \fBautoindent\fP characters on the line, all
characters on the line shall be discarded. Otherwise, it is unspecified
whether the \fBautoindent\fP characters in the line are
modified by entering these characters.
.LP
Continue text input mode on a new line appended after the current
line. If the \fBslowopen\fP 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.
.LP
If the \fBautoindent\fP edit option is set, an appropriate number
of \fBautoindent\fP characters shall be added as a prefix to
the line as described by the \fIex\fP \fBautoindent\fP edit option.
.LP
All columns after the cursor that are erase-columns (as described
in Input Mode Commands in vi )
shall be discarded.
.LP
If the \fBautoindent\fP edit option is set, all <blank>s immediately
following the cursor shall be discarded.
.LP
All remaining characters after the cursor shall be transferred to
the new line, positioned after any \fBautoindent\fP
characters.
.LP
\fICurrent line\fP: Set to current line +1.
.LP
\fICurrent column\fP: Set to the first column that displays any portion
of the first character after the \fBautoindent\fP
characters on the new line, if any, or the first column position after
the last \fBautoindent\fP character, if any, or column
position 1.
.SS <control>-T
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-T
\fP
.fi
.RE
.sp
.LP
The <control>-T character shall have no special meaning when in text
input mode for a line-oriented command (see Command Descriptions in
vi ).
.LP
This command need not be supported on block-mode terminals.
.LP
Behave as if the user entered the minimum number of <blank>s necessary
to move the cursor forward to the column position
after the next \fBshiftwidth\fP (see the \fIex\fP \fBshiftwidth\fP
command) boundary.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Set to \fIcolumn\fP + \fBshiftwidth\fP - ((column
-1) % \fBshiftwidth\fP).
.SS <control>-U
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-U
\fP
.fi
.RE
.sp
.LP
If there are characters other than \fBautoindent\fP characters that
have been input on the current line before the cursor, the
cursor shall move to the first character input after the \fBautoindent\fP
characters.
.LP
Otherwise, if there are \fBautoindent\fP characters on the current
line before the cursor, it is implementation-defined whether
the <control>-U command is an error or if the cursor moves to the
first column position on the line.
.LP
Otherwise, if the cursor is in column position 1 and there are previous
lines that have been input, it is implementation-defined
whether the <control>-U command is an error or if it is equivalent
to entering <control>-U after the last input
character on the previous input line.
.LP
Otherwise, it shall be an error.
.LP
All of the glyphs on columns between the starting cursor position
and (inclusively) the ending cursor position shall become
erase-columns as described in Input Mode Commands in vi .
.LP
The current \fIkill\fP character (see \fIstty\fP) shall cause an equivalent
action to the
<control>-U command, unless the previously inserted character was
a backslash, in which case it shall be as if the literal
current \fIkill\fP character had been inserted instead of the backslash.
.LP
\fICurrent line\fP: Unchanged, unless previously input lines are erased,
in which case it shall be set to line -1.
.LP
\fICurrent column\fP: Set to the first column that displays any portion
of the last character backed up over.
.SS <control>-V
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-V
.sp

<control>-Q
\fP
.fi
.RE
.sp
.LP
Allow the entry of any subsequent character, other than <control>-J
or the <newline>, as a literal character,
removing any special meaning that it may have to the editor in text
input mode. If a <control>-V or <control>-Q is
entered before a <control>-J or <newline>, the <control>-V or <control>-Q
character shall be discarded, and
the <control>-J or <newline> shall behave as described in the <newline>
command character during input mode.
.LP
For purposes of the display only, the editor shall behave as if a
\fB'^'\fP character was entered, and the cursor shall be
positioned as if overwriting the \fB'^'\fP character. When a subsequent
character is entered, the editor shall behave as if that
character was entered instead of the original <control>-V or <control>-Q
character.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP: Unchanged.
.SS <control>-W
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<control>-W
\fP
.fi
.RE
.sp
.LP
If there are characters other than \fBautoindent\fP characters that
have been input on the current line before the cursor, the
cursor shall move back over the last word preceding the cursor (including
any <blank>s between the end of the last word and
the current cursor); the cursor shall not move to before the first
character after the end of any \fBautoindent\fP characters.
.LP
Otherwise, if there are \fBautoindent\fP characters on the current
line before the cursor, it is implementation-defined whether
the <control>-W command is an error or if the cursor moves to the
first column position on the line.
.LP
Otherwise, if the cursor is in column position 1 and there are previous
lines that have been input, it is implementation-defined
whether the <control>-W command is an error or if it is equivalent
to entering <control>-W after the last input
character on the previous input line.
.LP
Otherwise, it shall be an error.
.LP
All of the glyphs on columns between the starting cursor position
and (inclusively) the ending cursor position shall become
erase-columns as described in Input Mode Commands in vi .
.LP
\fICurrent line\fP: Unchanged, unless previously input lines are erased,
in which case it shall be set to line -1.
.LP
\fICurrent column\fP: Set to the first column that displays any portion
of the last character backed up over.
.SS <ESC>
.TP 7
\fISynopsis\fP:
.sp
.RS
.nf

\fB<ESC>
\fP
.fi
.RE
.sp
.LP
If input was part of a line-oriented command:
.IP " 1." 4
If \fIinterrupt\fP was entered, text input mode shall be terminated
and the editor shall return to command mode. The terminal
shall be alerted.
.LP
.IP " 2." 4
If <ESC> was entered, text input mode shall be terminated and the
command shall continue execution with the input
provided.
.LP
.LP
Otherwise, terminate text input mode and return to command mode.
.LP
Any \fBautoindent\fP characters entered on newly created lines that
have no other non- <newline>s shall be deleted.
.LP
Any leading \fBautoindent\fP and <blank>s on newly created lines shall
be rewritten to be the minimum number of
<blank>s possible.
.LP
The screen shall be redisplayed as necessary to match the contents
of the edit buffer.
.LP
\fICurrent line\fP: Unchanged.
.LP
\fICurrent column\fP:
.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.
.LP
.IP " 2." 4
Otherwise, if a character is displayed in the current column, unchanged.
.LP
.IP " 3." 4
Otherwise, set to column position 1.
.LP
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
Successful completion.
.TP 7
>0
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
When any error is encountered and the standard input is not a terminal
device file, \fIvi\fP shall not write the file or return
to command or text input mode, and shall terminate with a non-zero
exit status.
.LP
Otherwise, when an unrecoverable error is encountered it shall be
equivalent to a SIGHUP asynchronous event.
.LP
Otherwise, when an error is encountered, the editor shall behave as
specified in Command
Descriptions in vi .
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
None.
.SH EXAMPLES
.LP
None.
.SH RATIONALE
.LP
See the RATIONALE for \fIex\fP for more information on \fIvi\fP. Major
portions of the \fIvi\fP utility
specification point to \fIex\fP to avoid inadvertent divergence. While
\fIex\fP and \fIvi\fP have historically been implemented as a single
utility, this is not required by
IEEE\ Std\ 1003.1-2001.
.LP
It is recognized that portions of \fIvi\fP 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 \fIvi\fP
implementation should provide the full set of capabilities on
all terminals capable of supporting them.
.LP
Historically, \fIvi\fP exited immediately if the standard input was
not a terminal. IEEE\ Std\ 1003.1-2001 permits, but
does not require, this behavior. An end-of-file condition is not equivalent
to an end-of-file character. A common end-of-file
character, <control>-D, is historically a \fIvi\fP command.
.LP
The text in the STDOUT section reflects the usage of the verb \fIdisplay\fP
in this section; some implementations of \fIvi\fP
use standard output to write to the terminal, but IEEE\ Std\ 1003.1-2001
does not require that to be the case.
.LP
Historically, implementations reverted to open mode if the terminal
was incapable of supporting full visual mode.
IEEE\ Std\ 1003.1-2001 requires this behavior. Historically, the open
mode of \fIvi\fP 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. IEEE\ Std\ 1003.1-2001 requires conformance to
historical practice.
.LP
Historically, \fIex\fP and \fIvi\fP implementations have expected
text to proceed in the
usual European/Latin order of left to right, top to bottom. There
is no requirement in IEEE\ Std\ 1003.1-2001 that this be
the case. The 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.
.LP
Historically, lines past the end of the edit buffer were marked with
single tilde ( \fB'~'\fP ) 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 \fB'~'\fP character.
.LP
Historically, the \fIvi\fP 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 \fB'@'\fP
characters, instead of displaying part of the line.
IEEE\ Std\ 1003.1-2001 permits, but does not require, this behavior.
Implementations are encouraged to attempt always to
display a complete line at the bottom of the screen when doing scrolling
or screen positioning by buffer lines.
.LP
Historically, lines marked with \fB'@'\fP 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 \fB'@'\fP sign instead of being updated to match the current
text. IEEE\ Std\ 1003.1-2001 permits, but does not
require this feature because it is used ever less frequently as terminals
become smarter and connections are faster.
.SS Initialization in ex and vi
.LP
Historically, \fIvi\fP always had a line in the edit buffer, even
if the edit buffer was "empty". For example:
.IP " 1." 4
The \fIex\fP command \fB=\fP executed from visual mode wrote "1" when
the buffer was
empty.
.LP
.IP " 2." 4
Writes from visual mode of an empty edit buffer wrote files of a single
character (a <newline>), while writes from \fIex\fP mode of an empty
edit buffer wrote empty files.
.LP
.IP " 3." 4
Put and read commands into an empty edit buffer left an empty line
at the top of the edit buffer.
.LP
.LP
For consistency, IEEE\ Std\ 1003.1-2001 does not permit any of these
behaviors.
.LP
Historically, \fIvi\fP did not always return the terminal to its original
modes; for example, ICRNL was modified if it was not
originally set. IEEE\ Std\ 1003.1-2001 does not permit this behavior.
.SS Command Descriptions in vi
.LP
Motion commands are among the most complicated aspects of \fIvi\fP
to describe. With some exceptions, the text region and
buffer type effect of a motion command on a \fIvi\fP command are described
on a case-by-case basis. The descriptions of text
regions in IEEE\ Std\ 1003.1-2001 are not intended to imply direction;
that is, an inclusive region from line \fIn\fP to
line \fIn\fP+5 is identical to a region from line \fIn\fP+5 to line
\fIn\fP. This is of more than academic interest-movements to
marks can be in either direction, and, if the \fBwrapscan\fP option
is set, so can movements to search points. Historically, lines
are always stored into buffers in text order; that is, from the start
of the edit buffer to the end. IEEE\ Std\ 1003.1-2001
requires conformance to historical practice.
.LP
Historically, command counts were applied to any associated motion,
and were multiplicative to any supplied motion count. For
example, \fB2cw\fP is the same as \fBc2w\fP, and \fB2c3w\fP is the
same as \fBc6w\fP. IEEE\ Std\ 1003.1-2001 requires
this behavior. Historically, \fIvi\fP commands that used bigwords,
words, paragraphs, and sentences as objects treated groups of
empty lines, or lines that contained only <blank>s, inconsistently.
Some commands treated them as a single entity, while
others treated each line separately. For example, the \fBw\fP, \fBW\fP,
and \fBB\fP commands treated groups of empty lines as
individual words; that is, the command would move the cursor to each
new empty line. The \fBe\fP and \fBE\fP commands treated
groups of empty lines as a single word; that is, the first use would
move past the group of lines. The \fBb\fP command would just
beep at the user, or if done from the start of the line as a motion
command, fail in unexpected ways. If the lines contained only
(or ended with) <blank>s, the \fBw\fP and \fBW\fP commands would just
beep at the user, the \fBE\fP and \fBe\fP commands
would treat the group as a single word, and the \fBB\fP and \fBb\fP
commands would treat the lines as individual words. For
consistency and simplicity of specification, IEEE\ Std\ 1003.1-2001
requires that all \fIvi\fP commands treat groups of
empty or blank lines as a single entity, and that movement through
lines ending with <blank>s be consistent with other
movements.
.LP
Historically, \fIvi\fP documentation indicated that any number of
double quotes were skipped after punctuation marks at
sentence boundaries; however, implementations only skipped single
quotes. IEEE\ Std\ 1003.1-2001 requires both to be
skipped.
.LP
Historically, the first and last characters in the edit buffer were
word boundaries. This historical practice is required by
IEEE\ Std\ 1003.1-2001.
.LP
Historically, \fIvi\fP attempted to update the minimum number of columns
on the screen possible, which could lead to misleading
information being displayed. IEEE\ Std\ 1003.1-2001 makes no requirements
other than that the current character being
entered is displayed correctly, leaving all other decisions in this
area up to the implementation.
.LP
Historically, lines were arbitrarily folded between columns of any
characters that required multiple column positions on the
screen, with the exception of tabs, which terminated at the right-hand
margin. IEEE\ Std\ 1003.1-2001 permits the former
and requires the latter. Implementations that do not arbitrarily break
lines between columns of characters that occupy multiple
column positions should not permit the cursor to rest on a column
that does not contain any part of a character.
.LP
The historical \fIvi\fP 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
\fBj\fP or \fBk\fP, should work on buffer lines. Commands like
\fBdj\fP, or \fBj.\fP, where \fB.\fP 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>-D, <control>-F,
and \fBH\fP. If the window is fairly
small, using buffer lines in these cases can result in completely
random motion; for example, \fB1\fP <control>-D can result
in a completely changed screen, without any overlap. This is clearly
not what the user wanted. The problem is even worse in the
case of the \fBH\fP, \fBL\fP, and \fBM\fP commands-as they position
the cursor at the first non- <blank> of the line, they
may all refer to the same location in large lines, and will result
in no movement at all.
.LP
In addition, if the line is larger than the screen, using buffer lines
can make it impossible to display parts of the line-there
are not any commands that do not display the beginning of the line
in historical \fIvi\fP, and if both the beginning and end of
the line cannot be on the screen at the same time, the user suffers.
Finally, the page and half-page scrolling commands
historically moved to the first non- <blank> in the new line. If the
line is approximately the same size as the screen, this
is inadequate because the cursor before and after a <control>-D command
will refer to the same location on the screen.
.LP
Implementations of \fIex\fP and \fIvi\fP exist that do not have these
problems because the
relevant commands ( <control>-B, <control>-D, <control>-F, <control>-U,
<control>-Y,
<control>-E, \fBH\fP, \fBL\fP, and \fBM)\fP operate on display (screen)
lines, not (edit) buffer lines.
.LP
IEEE\ Std\ 1003.1-2001 does not permit this behavior by default because
the standard developers believed that users
would find it too confusing. However, historical practice has been
relaxed. For example, \fIex\fP and \fIvi\fP 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 \fB'@'\fP
characters. This behavior is permitted, but not required
by IEEE\ Std\ 1003.1-2001, so that it is possible for implementations
to support long lines in small screens more
reasonably without changing the commands to be oriented to the display
(instead of oriented to the buffer).
IEEE\ Std\ 1003.1-2001 also permits implementations to refuse to edit
any edit buffer containing a line that will not fit
on the screen in its entirety.
.LP
The display area (for example, the value of the \fBwindow\fP 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 \fIex\fP
commands generally always
caused the screen to be redrawn. IEEE\ Std\ 1003.1-2001 does not specify
a standard behavior because there may be external
issues, such as connection speed, the number of characters necessary
to redraw as opposed to scroll, or terminal capabilities that
implementations will have to accommodate.
.LP
The current line in IEEE\ Std\ 1003.1-2001 maps one-to-one to a buffer
line in the file. The current column does not.
There are two different column values that are described by IEEE\ Std\ 1003.1-2001.
The first is the current column value
as set by many of the \fIvi\fP 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.
.LP
Commands that set the current line, but that do not set the current
cursor value (for example, \fBj\fP and \fBk\fP) attempt to
get as close as possible to the remembered column position, so that
the cursor tends to restrict itself to a vertical column as the
user moves around in the edit buffer. IEEE\ Std\ 1003.1-2001 requires
conformance to 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.
.LP
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, \fB:\fP, \fB!\fP, \fB/\fP,
or \fB?\fP. IEEE\ Std\ 1003.1-2001 permits,
but does not require, this limitation.
.LP
Historically, "soft" errors in \fIvi\fP 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 \fIvi\fP, 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 \fBh\fP at the left
margin, <control>-B or \fB[[\fP at the beginning of the file, \fB2G\fP
at the end of the file, and so on. In addition,
errors such as \fB%\fP, \fB]]\fP, \fB}\fP, \fB)\fP, \fBN\fP, \fBn\fP,
\fBf\fP, \fBF\fP, \fBt\fP, and \fBT\fP failing to
find the searched-for object were soft as well. Less consistently,
\fB/\fP and \fB?\fP displayed an error message if the pattern
was not found, \fB/\fP, \fB?\fP, \fBN\fP, and \fBn\fP displayed an
error message if no previous regular expression had been
specified, and \fB;\fP did not display an error message if no previous
\fBf\fP, \fBF\fP, \fBt\fP, or \fBT\fP command had
occurred. Also, behavior in this area might reasonably be based on
a runtime evaluation of the speed of a network connection.
Finally, some implementations have provided error messages for soft
errors in order to assist naive users, based on the value of a
verbose edit option. IEEE\ Std\ 1003.1-2001 does not list specific
errors for which an error message shall be displayed.
Implementations should conform to historical practice in the absence
of any strong reason to diverge.
.SS Page Backwards
.LP
The <control>-B and <control>-F commands historically considered it
an error to attempt to page past the beginning
or end of the file, whereas the <control>-D and <control>-U commands
simply moved to the beginning or end of the file.
For consistency, IEEE\ Std\ 1003.1-2001 requires the latter behavior
for all four commands. All four commands still
consider it an error if the current line is at the beginning ( <control>-B,
<control>-U) or end ( <control>-F,
<control>-D) of the file. Historically, the <control>-B and <control>-F
commands skip two lines in order to
include overlapping lines when a single command is entered. This makes
less sense in the presence of a \fIcount\fP, as there will
be, by definition, no overlapping lines. The actual calculation used
by historical implementations of the \fIvi\fP editor for
<control>-B was:
.sp
.RS
.nf

\fB((current first line) - count x (window edit option)) +2
\fP
.fi
.RE
.LP
and for <control>-F was:
.sp
.RS
.nf

\fB((current first line) + count x (window edit option)) -2
\fP
.fi
.RE
.LP
This calculation does not work well when intermixing commands with
and without counts; for example, \fB3\fP <control>-F
is not equivalent to entering the <control>-F command three times,
and is not reversible by entering the <control>-B
command three times. For consistency with other \fIvi\fP commands
that take counts, IEEE\ Std\ 1003.1-2001 requires a
different calculation.
.SS Scroll Forward
.LP
The 4BSD and System V implementations of \fIvi\fP differed on the
initial value used by the \fBscroll\fP command. 4BSD
used:
.sp
.RS
.nf

\fB((window edit option) +1) /2
\fP
.fi
.RE
.LP
while System V used the value of the \fBscroll\fP edit option. The
System V version is specified by
IEEE\ Std\ 1003.1-2001 because the standard developers believed that
it was more intuitive and permitted the user a method
of setting the scroll value initially without also setting the number
of lines that are displayed.
.SS Scroll Forward by Line
.LP
Historically, the <control>-E and <control>-Y commands considered
it an error if the last and first lines,
respectively, were already on the screen. IEEE\ Std\ 1003.1-2001 requires
conformance to historical practice. Historically,
the <control>-E and <control>-Y commands had no effect in open mode.
For simplicity and consistency of specification,
IEEE\ Std\ 1003.1-2001 requires that they behave as usual, albeit
with a single line screen.
.SS Clear and Redisplay
.LP
The historical <control>-L command refreshed the screen exactly as
it was supposed to be currently displayed, replacing
any \fB'@'\fP characters for lines that had been deleted but not updated
on the screen with refreshed \fB'@'\fP characters.
The intent of the <control>-L command is to refresh when the screen
has been accidentally overwritten; for example, by a
\fBwrite\fP command from another user, or modem noise.
.SS Redraw Screen
.LP
The historical <control>-R command redisplayed only when necessary
to update lines that had been deleted but not updated
on the screen and that were flagged with \fB'@'\fP characters. There
is no requirement that the screen be in any way refreshed
if no lines of this form are currently displayed. IEEE\ Std\ 1003.1-2001
permits implementations to extend this command to
refresh lines on the screen flagged with \fB'@'\fP 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
.LP
Historically, the first non- <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
\fB'#'\fP character in the text \fB"#bar@"\fP , the tag was \fB"#bar"\fP
\&. On the character \fB'b'\fP it was
\fB"bar"\fP , and on the \fB'a'\fP it was \fB"ar"\fP . IEEE\ Std\ 1003.1-2001
requires this behavior.
.SS Replace Text with Results from Shell Command
.LP
Historically, the \fB<\fP, \fB>\fP, and \fB!\fP commands considered
most cursor motions other than line-oriented
motions an error; for example, the command \fB>/foo<CR>\fP succeeded,
while the command \fB>l\fP 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
.LP
Other matching characters have been left implementation-defined in
order to allow extensions such as matching \fB'<'\fP
and \fB'>'\fP for searching HTML, or \fB#ifdef\fP, \fB#else\fP, and
\fB#endif\fP for searching C source.
.SS Repeat Substitution
.LP
IEEE\ Std\ 1003.1-2001 requires that any \fBc\fP and \fBg\fP flags
specified to the previous substitute command be
ignored; however, the \fBr\fP flag may still apply, if supported by
the implementation.
.SS Return to Previous (Context or Section)
.LP
The \fB[[\fP, \fB]]\fP, \fB(\fP, \fB)\fP, \fB{\fP, and \fB}\fP 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,
\fIvi\fP section boundaries at the beginning and end of
the edit buffer were the first non- <blank> on the first and last
lines of the edit buffer if one exists; otherwise, the last
character of the first and last lines of the edit buffer if one exists.
To increase consistency with other section locations, this
has been simplified by IEEE\ Std\ 1003.1-2001 to the first character
of the first and last lines of the edit buffer, or the
first and the last lines of the edit buffer if they are empty.
.LP
Sentence boundaries were problematic in the historical \fIvi\fP. They
were not only the boundaries as defined for the section
and paragraph commands, but they were the first non- <blank> that
occurred after those boundaries, as well. Historically, the
\fIvi\fP section commands were documented as taking an optional window
size as a \fIcount\fP preceding the command. This was not
implemented in historical versions, so IEEE\ Std\ 1003.1-2001 requires
that the \fIcount\fP repeat the command, for
consistency with other \fIvi\fP commands.
.SS Repeat
.LP
Historically, mapped commands other than text input commands could
not be repeated using the \fBperiod\fP command.
IEEE\ Std\ 1003.1-2001 requires conformance to historical practice.
.LP
The restrictions on the interpretation of special characters (for
example, <control>-H) in the repetition of text input
mode commands is intended to match historical practice. For example,
given the input sequence:
.sp
.RS
.nf

\fBiab<control>-H<control>-H<control>-Hdef<escape>
\fP
.fi
.RE
.LP
the user should be informed of an error when the sequence is first
entered, but not during a command repetition. The character
<control>-T is specifically exempted from this restriction. Historical
implementations of \fIvi\fP ignored <control>-T
characters that were input in the original command during command
repetition. IEEE\ Std\ 1003.1-2001 prohibits this
behavior.
.SS Find Regular Expression
.LP
Historically, commands did not affect the line searched to or from
if the motion command was a search ( \fB/\fP, \fB?\fP,
\fBN\fP, \fBn\fP) and the final position was the start/end of the
line. There were some special cases and \fIvi\fP was not
consistent. IEEE\ Std\ 1003.1-2001 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 \fBwrapscan\fP) to the original
location. IEEE\ Std\ 1003.1-2001 requires that this behavior be treated
as an error.
.LP
Historically, the syntax \fB"/RE/0"\fP was used to force the command
to cut text in line mode. IEEE\ Std\ 1003.1-2001
requires conformance to historical practice.
.LP
Historically, in open mode, a \fBz\fP 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, IEEE\ Std\ 1003.1-2001
does not permit this behavior.
.LP
Historically, trailing \fBz\fP commands were permitted and ignored
if entered as part of a search used as a motion command. For
consistency and simplicity of specification, IEEE\ Std\ 1003.1-2001
does not permit this behavior.
.SS Execute an ex Command
.LP
Historically, \fIvi\fP implementations restricted the commands that
could be entered on the colon command line (for example,
\fBappend\fP and \fBchange\fP), and some other commands were known
to cause them to fail catastrophically. For consistency,
IEEE\ Std\ 1003.1-2001 does not permit these restrictions. When executing
an \fIex\fP
command by entering \fB:\fP, 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 \fIex\fP command
mode by using the \fIvi\fP
\fBQ\fP command (and later resuming visual mode with the \fIex\fP
\fBvi\fP command). In \fIex\fP command mode, the single-line limitation
does not exist. So, for example, the following
is valid:
.sp
.RS
.nf

\fBQ
s/break here/break\\
here/
vi
\fP
.fi
.RE
.LP
IEEE\ Std\ 1003.1-2001 requires that, if the \fIex\fP command overwrites
any part of
the screen that would be erased by a refresh, \fIvi\fP 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.
IEEE\ Std\ 1003.1-2001 requires conformance to historical practice.
.SS Shift Left (Right)
.LP
Refer to the Rationale for the \fB!\fP and \fB/\fP commands. Historically,
the \fB<\fP and \fB>\fP commands sometimes
moved the cursor to the first non- <blank> (for example if the command
was repeated or with \fB_\fP as the motion command),
and sometimes left it unchanged. IEEE\ Std\ 1003.1-2001 does not permit
this inconsistency, requiring instead that the
cursor always move to the first non- <blank>. Historically, the \fB<\fP
and \fB>\fP commands did not support buffer
arguments, although some implementations allow the specification of
an optional buffer. This behavior is neither required nor
disallowed by IEEE\ Std\ 1003.1-2001.
.SS Execute
.LP
Historically, buffers could execute other buffers, and loops, infinite
and otherwise, were possible.
IEEE\ Std\ 1003.1-2001 requires conformance to historical practice.
The * \fIbuffer\fP syntax of \fIex\fP is not required in \fIvi\fP,
because it is not historical practice and has been used in some
\fIvi\fP implementations to support additional scripting languages.
.SS Reverse Case
.LP
Historically, the \fB~\fP command ignored any associated \fIcount\fP,
and acted only on the characters in the current
line. For consistency with other \fIvi\fP commands, IEEE\ Std\ 1003.1-2001
requires that an associated \fIcount\fP act on
the next \fIcount\fP characters, and that the command move to subsequent
lines if warranted by \fIcount\fP, to make it possible
to modify large pieces of text in a reasonably efficient manner. There
exist \fIvi\fP implementations that optionally require an
associated motion command for the \fB~\fP command. Implementations
supporting this functionality are encouraged to base it on
the \fBtildedop\fP edit option and handle the text regions and cursor
positioning identically to the \fByank\fP command.
.SS Append
.LP
Historically, \fIcount\fPs specified to the \fBA\fP, \fBa\fP, \fBI\fP,
and \fBi\fP commands repeated the input of the first
line \fIcount\fP times, and did not repeat the subsequent lines of
the input text. IEEE\ Std\ 1003.1-2001 requires that
the entire text input be repeated \fIcount\fP times.
.SS Move Backward to Preceding Word
.LP
Historically, \fIvi\fP became confused if word commands were used
as motion commands in empty files.
IEEE\ Std\ 1003.1-2001 requires that this be an error. Historical
implementations of \fIvi\fP had a large number of bugs
in the word movement commands, and they varied greatly in behavior
in the presence of empty lines, "words" made up of a single
character, and lines containing only <blank>s. For consistency and
simplicity of specification,
IEEE\ Std\ 1003.1-2001 does not permit this behavior.
.SS Change to End-of-Line
.LP
Some historical implementations of the \fBC\fP command did not behave
as described by IEEE\ Std\ 1003.1-2001 when the
\fB$\fP key was remapped because they were implemented by pushing
the \fB$\fP key onto the input queue and reprocessing it.
IEEE\ Std\ 1003.1-2001 does not permit this behavior. Historically,
the \fBC\fP, \fBS\fP, and \fBs\fP commands did not
copy replaced text into the numeric buffers. For consistency and simplicity
of specification, IEEE\ Std\ 1003.1-2001
requires that they behave like their respective \fBc\fP commands in
all respects.
.SS Delete
.LP
Historically, lines in open mode that were deleted were scrolled up,
and an \fB@\fP glyph written over the beginning of the
line. In the case of terminals that are incapable of the necessary
cursor motions, the editor erased the deleted line from the
screen. IEEE\ Std\ 1003.1-2001 requires conformance to historical
practice; that is, if the terminal cannot display the
\fB'@'\fP character, the line cannot remain on the screen.
.SS Delete to End-of-Line
.LP
Some historical implementations of the \fBD\fP command did not behave
as described by IEEE\ Std\ 1003.1-2001 when the
\fB$\fP key was remapped because they were implemented by pushing
the \fB$\fP key onto the input queue and reprocessing it.
IEEE\ Std\ 1003.1-2001 does not permit this behavior.
.SS Join
.LP
An historical oddity of \fIvi\fP is that the commands \fBJ\fP, \fB1J\fP,
and \fB2J\fP are all equivalent.
IEEE\ Std\ 1003.1-2001 requires conformance to historical practice.
The \fIvi\fP \fBJ\fP command is specified in terms of
the \fIex\fP \fBjoin\fP command with an \fIex\fP command
\fIcount\fP value. The address correction for a \fIcount\fP that is
past the end of the edit buffer is necessary for historical
compatibility for both \fIex\fP and \fIvi\fP.
.SS Mark Position
.LP
Historical practice is that only lowercase letters, plus \fB'`'\fP
and \fB'"\fP , could be used to mark a cursor
position. IEEE\ Std\ 1003.1-2001 requires conformance to historical
practice, but encourages implementations to support
other characters as marks as well.
.SS Repeat Regular Expression Find (Forward and Reverse)
.LP
Historically, the \fBN\fP and \fBn\fP commands could not be used as
motion components for the \fBc\fP command. With the
exception of the \fBcN\fP command, which worked if the search crossed
a line boundary, the text region would be discarded, and the
user would not be in text input mode. For consistency and simplicity
of specification, IEEE\ Std\ 1003.1-2001 does not
permit this behavior.
.SS Insert Empty Line (Below and Above)
.LP
Historically, counts to the \fBO\fP and \fBo\fP commands were used
as the number of physical lines to open, if the terminal
was dumb and the \fBslowopen\fP option was not set. This was intended
to minimize traffic over slow connections and repainting for
dumb terminals. IEEE\ Std\ 1003.1-2001 does not permit this behavior,
requiring that a \fIcount\fP 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 \fBslowopen\fP edit option.
.SS Put from Buffer (Following and Before)
.LP
Historically, \fIcount\fPs to the \fBp\fP and \fBP\fP commands were
ignored if the buffer was a line mode buffer, but were
(mostly) implemented as described in IEEE\ Std\ 1003.1-2001 if the
buffer was a character mode buffer. Because
implementations exist that do not have this limitation, and because
pasting lines multiple times is generally useful,
IEEE\ Std\ 1003.1-2001 requires that \fIcount\fP be supported for
all \fBp\fP and \fBP\fP commands.
.LP
Historical implementations of \fIvi\fP were widely known to have major
problems in the \fBp\fP and \fBP\fP 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.
.LP
Historically, a \fBP\fP or \fBp\fP command (or an \fIex\fP \fBput\fP
command executed
from open or visual mode) executed in an empty file, left an empty
line as the first line of the file. For consistency and
simplicity of specification, IEEE\ Std\ 1003.1-2001 does not permit
this behavior.
.SS Replace Character
.LP
Historically, the \fBr\fP command did not correctly handle the \fIerase\fP
and \fIword erase\fP characters as arguments, nor
did it handle an associated \fIcount\fP greater than 1 with a <carriage-return>
argument, for which it replaced \fIcount\fP
characters with a single <newline>. IEEE\ Std\ 1003.1-2001 does not
permit these inconsistencies.
.LP
Historically, the \fBr\fP command permitted the <control>-V escaping
of entered characters, such as <ESC> and the
<carriage-return>; however, it required two leading <control>-V characters
instead of one.
IEEE\ Std\ 1003.1-2001 requires that this be changed for consistency
with the other text input commands of \fIvi\fP.
.LP
Historically, it is an error to enter the \fBr\fP command if there
are less than \fIcount\fP characters at or after the cursor
in the line. While a reasonable and unambiguous extension would be
to permit the \fBr\fP command on empty lines, it would require
that too large a \fIcount\fP be adjusted to match the number of characters
at or after the cursor for consistency, which is
sufficiently different from historical practice to be avoided. IEEE\ Std\ 1003.1-2001
requires conformance to historical
practice.
.SS Replace Characters
.LP
Historically, if there were \fBautoindent\fP characters in the line
on which the \fBR\fP command was run, and
\fBautoindent\fP was set, the first <newline> would be properly indented
and no characters would be replaced by the
<newline>. Each additional <newline> would replace \fIn\fP characters,
where \fIn\fP was the number of characters
that were needed to indent the rest of the line to the proper indentation
level. This behavior is a bug and is not permitted by
IEEE\ Std\ 1003.1-2001.
.SS Undo
.LP
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- <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 \fBo\fP text
input command, followed by an \fBundo\fP would return the cursor to
the location where the \fBo\fP command was entered, but a
\fBcw\fP command followed by an \fBo\fP command followed by an \fBundo\fP
would return the cursor to the first non-
<blank> of the line. IEEE\ Std\ 1003.1-2001 requires the most useful
of these behaviors, and discards the least
useful, in the interest of consistency and simplicity of specification.
.SS Yank
.LP
Historically, the \fByank\fP 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 \fB_\fP command, or for the \fBG\fP and
\fB'\fP 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 \fByank\fP 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
\fByank\fP command. IEEE\ Std\ 1003.1-2001 requires that all \fByank\fP
commands associated with backward motions move
the cursor to the end of the motion for consistency, and specifically,
to make \fB'\fP commands as motions consistent with search
patterns as motions.
.SS Yank Current Line
.LP
Some historical implementations of the \fBY\fP command did not behave
as described by IEEE\ Std\ 1003.1-2001 when the
\fB'_'\fP key was remapped because they were implemented by pushing
the \fB'_'\fP key onto the input queue and reprocessing
it. IEEE\ Std\ 1003.1-2001 does not permit this behavior.
.SS Redraw Window
.LP
Historically, the \fBz\fP command always redrew the screen. This is
permitted but not required by
IEEE\ Std\ 1003.1-2001, because of the frequent use of the \fBz\fP
command in macros such as \fBmap n nz.\fP 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>-L and <control>-R commands.
.LP
The semantics of \fBz^\fP are confusing at best. Historical practice
is that the screen before the screen that ended with the
specified line is displayed. IEEE\ Std\ 1003.1-2001 requires conformance
to historical practice.
.LP
Historically, the \fBz\fP 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
\fB'@'\fP characters. If the partial line would normally have been
displayed at the top of the screen, the command would fail.
For consistency and simplicity of specification, IEEE\ Std\ 1003.1-2001
does not permit this behavior.
.LP
Historically, the \fBz\fP command with a line specification of 1 ignored
the command. For consistency and simplicity of
specification, IEEE\ Std\ 1003.1-2001 does not permit this behavior.
.LP
Historically, the \fBz\fP command did not set the cursor column to
the first non- <blank> for the character if the first
screen was to be displayed, and was already displayed. For consistency
and simplicity of specification,
IEEE\ Std\ 1003.1-2001 does not permit this behavior.
.SS Input Mode Commands in vi
.LP
Historical implementations of \fIvi\fP did not permit the user to
erase more than a single line of input, or to use normal
erase characters such as \fIline erase\fP, \fIworderase\fP, and \fIerase\fP
to erase \fBautoindent\fP characters. As there
exist implementations of \fIvi\fP that do not have these limitations,
both behaviors are permitted, but only historical practice
is required. In the case of these extensions, \fIvi\fP is required
to pause at the \fBautoindent\fP and previous line
boundaries.
.LP
Historical implementations of \fIvi\fP updated only the portion of
the screen where the current cursor character was displayed.
For example, consider the \fIvi\fP input keystrokes:
.sp
.RS
.nf

\fBiabcd<escape>0C<tab>
\fP
.fi
.RE
.LP
Historically, the <tab> would overwrite the characters \fB"abcd"\fP
when it was displayed. Other implementations
replace only the \fB'a'\fP 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
.nf

\fBiabcd<ESC>0R<tab><ESC>
\fP
.fi
.RE
.LP
the historical implementation results in the string \fB"bcd"\fP disappearing
and then magically reappearing when the
<ESC> character is entered. IEEE\ Std\ 1003.1-2001 requires the former
behavior when overwriting erase-columns-that
is, overwriting characters that are no longer logically part of the
edit buffer-and the latter behavior otherwise.
.LP
Historical implementations of \fIvi\fP discarded the <control>-D and
<control>-T characters when they were entered
at places where their command functionality was not appropriate. IEEE\ Std\ 1003.1-2001
requires that the <control>-T
functionality always be available, and that <control>-D be treated
as any other key when not operating on \fBautoindent\fP
characters.
.SS NUL
.LP
Some historical implementations of \fIvi\fP limited the number of
characters entered using the NUL input character to 256
bytes. IEEE\ Std\ 1003.1-2001 permits this limitation; however, implementations
are encouraged to remove this limit.
.SS <control>-D
.LP
See also Rationale for the input mode command <newline>. The hidden
assumptions in the <control>-D command (and in
the \fIvi\fP \fBautoindent\fP specification in general) is that <space>s
take up a single column on the screen and that
<tab>s are comprised of an integral number of <space>s.
.SS <newline>
.LP
Implementations are permitted to rewrite \fBautoindent\fP characters
in the line when <newline>, <carriage-return>,
<control>-D, and <control>-T are entered, or when the \fBshift\fP
commands are used, because historical
implementations have both done so and found it necessary to do so.
For example, a <control>-D when the cursor is preceded by
a single <tab>, with \fBtabstop\fP set to 8, and \fBshiftwidth\fP
set to 3, will result in the <tab> being replaced
by several <space>s.
.SS <control>-T
.LP
See also the Rationale for the input mode command <newline>. Historically,
<control>-T only worked if no non-
<blank>s had yet been input in the current input line. In addition,
the characters inserted by <control>-T were treated
as \fBautoindent\fP 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, IEEE\ Std\ 1003.1-2001 requires that
both limitations be removed.
.SS <control>-V
.LP
Historically, \fIvi\fP used \fB^V\fP, regardless of the value of the
literal-next character of the terminal.
IEEE\ Std\ 1003.1-2001 requires conformance to historical practice.
.LP
The uses described for <control>-V can also be accomplished with <control>-Q,
which is useful on terminals that use
<control>-V for the down-arrow function. However, most historical
implementations use <control>-Q for the
\fItermios\fP START character, so the editor will generally not receive
the <control>-Q unless \fBstty ixon\fP mode is set
to off. (In addition, some historical implementations of \fIvi\fP
explicitly set \fBixon\fP mode to on, so it was difficult for
the user to set it to off.) Any of the command characters described
in IEEE\ Std\ 1003.1-2001 can be made ineffective by
their selection as \fItermios\fP control characters, using the \fIstty\fP
utility or other
methods described in the System Interfaces volume of IEEE\ Std\ 1003.1-2001.
.SS <ESC>
.LP
Historically, SIGINT alerted the terminal when used to end input mode.
This behavior is permitted, but not required, by
IEEE\ Std\ 1003.1-2001.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIed\fP , \fIex\fP , \fIstty\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .