neulab/tldr huggingface dataset:
If the -r option was specified, the first time a file in the initial argument list or a file specified by the -t option is edited, if recovery information has previously been saved about it, that information shall be recovered and the editor shall behave as if the contents of the edit buffer have already been modified. If there are multiple instances of the file to be recovered, the one most recently saved shall be recovered, and an informational message that there are previous versions of the file that can be recovered shall be written. If no recovery information about a file is available, an informational message to this effect shall be written, and the edit shall proceed as usual.
If the -c option was specified, the first time a file that already exists (including a file that might not exist but for which recovery information is available, when the -r option is specified) replaces or initializes the contents of the edit buffer, the current line shall be set to the last line of the edit buffer, the current column shall be set to non-<blank>, and the ex commands specified with the -c option shall be executed. In this case, the current line and current column shall not be set as described for the command associated with the replacement or initialization of the edit buffer contents. However, if the -t option or a tag command is associated with this action, the -c option commands shall be executed and then the movement to the tag shall be performed.
The current argument list shall initially be set to the filenames specified by the user on the command line. If no filenames are specified by the user, the current argument list shall be empty. If the -t option was specified, it is unspecified whether any filename resulting from tag processing shall be prepended to the current argument list. In the case where the filename is added as a prefix to the current argument list, the current argument list reference shall be set to that filename. In the case where the filename is not added as a prefix to the current argument list, the current argument list reference shall logically be located before the first of the filenames specified on the command line (for example, a subsequent ex next command shall edit the first filename from the command line). If the -t option was not specified, the current argument list reference shall be to the first of the filenames on the command line.
Addressing in ex Addressing in ex relates to the current line and the current column; the address of a line is its 1-based line number, the address of a column is its 1-based count from the beginning of the line. Generally, the current line is the last line affected by a command. The current line number is the address of the current line. In each command description, the effect of the command on the current line number and the current column is described.
Addresses are constructed as follows:
1. The character '.'  (period) shall address the current line.
2. The character '$' shall address the last line of the edit buffer.
3. The positive decimal number n shall address the nth line of the edit buffer.
4. The address "'x" refers to the line marked with the mark name character 'x', which shall be a lowercase letter from the portable character set, the backquote character, or the single-quote character. It shall be an error if the line that was marked is not currently present in the edit buffer or the mark has not been set. Lines can be marked with the ex mark or k commands, or the vi m command.
5. A regular expression enclosed by <slash> characters ('/') shall address the first line found by searching forwards from the line following the current line toward the end of the edit buffer and stopping at the first line for which the line excluding the terminating <newline> matches the regular expression. As stated in Regular Expressions in ex, an address consisting of a null regular expression delimited by <slash> characters ("//") shall address the next line for which the line excluding the terminating <newline> matches the last regular expression encountered. In addition, the second <slash> can be omitted at the end of a command line. If the wrapscan edit option is set, the search shall wrap around to the beginning of the edit buffer and continue up to and including the current line, so that the entire edit buffer is searched. Within the regular expression, the sequence "\/" shall represent a literal <slash> instead of the regular expression delimiter.
6. A regular expression enclosed in <question-mark> characters ('?') shall address the first line found by searching backwards from the line preceding the current line toward the beginning of the edit buffer and stopping at the first line for which the line excluding the terminating <newline> matches the regular expression. An address consisting of a null regular expression delimited by <question-mark> characters ("??") shall address the previous line for which the line excluding the terminating <newline> matches the last regular expression encountered. In addition, the second <question-mark> can be omitted at the end of a command line. If the wrapscan edit option is set, the search shall wrap around from the beginning of the edit buffer to the end of the edit buffer and continue up to and including the current line, so that the entire edit buffer is searched. Within the regular expression, the sequence "\?" shall represent a literal <question-mark> instead of the RE delimiter.
7. A <plus-sign> ('+') or a <hyphen-minus> ('-') followed by a decimal number shall address the current line plus or minus the number. A '+' or '-' not followed by a decimal number shall address the current line plus or minus 1.
Addresses can be followed by zero or more address offsets, optionally <blank>-separated.  Address offsets are constructed as follows:
1. A '+' or '-' immediately followed by a decimal number shall add (subtract) the indicated number of lines to (from) the address. A '+' or '-' not followed by a decimal number shall add (subtract) 1 to (from) the address.
2. A decimal number shall add the indicated number of lines to the address.
It shall not be an error for an intermediate address value to be less than zero or greater than the last line in the edit buffer. It shall be an error for the final address value to be less than zero or greater than the last line in the edit buffer.
Commands take zero, one, or two addresses; see the descriptions of 1addr and 2addr in Command Descriptions in ex.  If more than the required number of addresses are provided to a command that requires zero addresses, it shall be an error. Otherwise, if more than the required number of addresses are provided to a command, the addresses specified first shall be evaluated and then discarded until the maximum number of valid addresses remain.
Addresses shall be separated from each other by a <comma> (',') or a <semicolon> (';').  If no address is specified before or after a <comma> or <semicolon> separator, it shall be as if the address of the current line was specified before or after the separator. In the case of a <semicolon> separator, the current line ('.')  shall be set to the first address, and only then will the next address be calculated. This feature can be used to determine the starting line for forwards and backwards searches (see rules 5. and 6.).
A <percent-sign> ('%') shall be equivalent to entering the two addresses "1,$".
Any delimiting <blank> characters between addresses, address separators, or address offsets shall be discarded.
Command Line Parsing in ex The following symbol is used in this and following sections to describe parsing behavior:
escape    If a character is referred to as ``<backslash>-escaped'' or ``<control>‐V-escaped'', it shall mean that the character acquired or lost a special meaning by virtue of being preceded, respectively, by a <backslash> or <control>‐V character. Unless otherwise specified, the escaping character shall be discarded at that time and shall not be further considered for any purpose.
Command-line parsing shall be done in the following steps. For each step, characters already evaluated shall be ignored; that is, the phrase ``leading character'' refers to the next character that has not yet been evaluated.
1. Leading <colon> characters shall be skipped.
2. Leading <blank> characters shall be skipped.
3. If the leading character is a double-quote character, the characters up to and including the next non-<backslash>-escaped <newline> shall be discarded, and any subsequent characters shall be parsed as a separate command.
4. Leading characters that can be interpreted as addresses shall be evaluated; see Addressing in ex.
5. Leading <blank> characters shall be skipped.
6. If the next character is a <vertical-line> character or a <newline>:
a. If the next character is a <newline>:
i.  If ex is in open or visual mode, the current line shall be set to the last address specified, if any.
ii.  Otherwise, if the last command was terminated by a <vertical-line> character, no action shall be taken; for example, the command "||<newline>" shall execute two implied commands, not three.
iii. Otherwise, step 6.b. shall apply.
b. Otherwise, the implied command shall be the print command. The last #, p, and l flags specified to any ex command shall be remembered and shall apply to this implied command.  Executing the ex number, print, or list command shall set the remembered flags to #, nothing, and l, respectively, plus any other flags specified for that execution of the number, print, or list command.
If ex is not currently performing a global or v command, and no address or count is specified, the current line shall be incremented by 1 before the command is executed. If incrementing the current line would result in an address past the last line in the edit buffer, the command shall fail, and the increment shall not happen.
c. The <newline> or <vertical-line> character shall be discarded and any subsequent characters shall be parsed as a separate command.
7. The command name shall be comprised of the next character (if the character is not alphabetic), or the next character and any subsequent alphabetic characters (if the character is alphabetic), with the following exceptions:
a. Commands that consist of any prefix of the characters in the command name delete, followed immediately by any of the characters 'l', 'p', '+', '-', or '#' shall be interpreted as a delete command, followed by a <blank>, followed by the characters that were not part of the prefix of the delete command. The maximum number of characters shall be matched to the command name delete; for example, "del" shall not be treated as "de" followed by the flag l.
b. Commands that consist of the character 'k', followed by a character that can be used as the name of a mark, shall be equivalent to the mark command followed by a <blank>, followed by the character that followed the 'k'.
c. Commands that consist of the character 's', followed by characters that could be interpreted as valid options to the s command, shall be the equivalent of the s command, without any pattern or replacement values, followed by a <blank>, followed by the characters after the 's'.
8. The command name shall be matched against the possible command names, and a command name that contains a prefix matching the characters specified by the user shall be the executed command. In the case of commands where the characters specified by the user could be ambiguous, the executed command shall be as follows:
┌───┬────────┬┬───┬───────┬┬───┬───────┐ │a  │ append ││n  │ next  ││t  │ t     │ │c  │ change ││p  │ print ││u  │ undo  │ │ch │ change ││pr │ print ││un │ undo  │ │e  │ edit   ││r  │ read  ││v  │ v     │ │m  │ move   ││re │ read  ││w  │ write │ │ma │ mark   ││s  │ s     ││   │       │ └───┴────────┴┴───┴───────┴┴───┴───────┘ Implementation extensions with names causing similar ambiguities shall not be checked for a match until all possible matches for commands specified by POSIX.1‐2008 have been checked.
9. If the command is a !  command, or if the command is a read command followed by zero or more <blank> characters and a !, or if the command is a write command followed by one or more <blank> characters and a !, the rest of the command shall include all characters up to a non-<backslash>-escaped <newline>.  The <newline> shall be discarded and any subsequent characters shall be parsed as a separate ex command.
10. Otherwise, if the command is an edit, ex, or next command, or a visual command while in open or visual mode, the next part of the command shall be parsed as follows:
a. Any '!'  character immediately following the command shall be skipped and be part of the command.
b. Any leading <blank> characters shall be skipped and be part of the command.
c. If the next character is a '+', characters up to the first non-<backslash>-escaped <newline> or non-<backslash>-escaped <blank> shall be skipped and be part of the command.
d. The rest of the command shall be determined by the steps specified in paragraph 12.
11. Otherwise, if the command is a global, open, s, or v command, the next part of the command shall be parsed as follows:
a. Any leading <blank> characters shall be skipped and be part of the command.
b. If the next character is not an alphanumeric, double-quote, <newline>, <backslash>, or <vertical-line> character:
i.  The next character shall be used as a command delimiter.
ii.  If the command is a global, open, or v command, characters up to the first non-<backslash>-escaped <newline>, or first non-<backslash>-escaped delimiter character, shall be skipped and be part of the command.
iii. If the command is an s command, characters up to the first non-<backslash>-escaped <newline>, or second non-<backslash>-escaped delimiter character, shall be skipped and be part of the command.
c. If the command is a global or v command, characters up to the first non-<backslash>-escaped <newline> shall be skipped and be part of the command.
d. Otherwise, the rest of the command shall be determined by the steps specified in paragraph 12.
12. Otherwise:
a. If the command was a map, unmap, abbreviate, or unabbreviate command, characters up to the first non-<control>‐V-escaped <newline>, <vertical-line>, or double-quote character shall be skipped and be part of the command.
b. Otherwise, characters up to the first non-<backslash>-escaped <newline>, <vertical-line>, or double-quote character shall be skipped and be part of the command.
c. If the command was an append, change, or insert command, and the step 12.b. ended at a <vertical-line> character, any subsequent characters, up to the next non-<backslash>-escaped <newline> shall be used as input text to the command.
d. If the command was ended by a double-quote character, all subsequent characters, up to the next non-<backslash>-escaped <newline>, shall be discarded.
e. The terminating <newline> or <vertical-line> character shall be discarded and any subsequent characters shall be parsed as a separate ex command.
Command arguments shall be parsed as described by the Synopsis and Description of each individual ex command. This parsing shall not be <blank>-sensitive, except for the !  argument, which must follow the command name without intervening <blank> characters, and where it would otherwise be ambiguous. For example, count and flag arguments need not be <blank>-separated because "d22p" is not ambiguous, but file arguments to the ex next command must be separated by one or more <blank> characters. Any <blank> in command arguments for the abbreviate, unabbreviate, map, and unmap commands can be <control>‐V-escaped, in which case the <blank> shall not be used as an argument delimiter. Any <blank> in the command argument for any other command can be <backslash>-escaped, in which case that <blank> shall not be used as an argument delimiter.
Within command arguments for the abbreviate, unabbreviate, map, and unmap commands, any character can be <control>‐V-escaped.  All such escaped characters shall be treated literally and shall have no special meaning. Within command arguments for all other ex commands that are not regular expressions or replacement strings, any character that would otherwise have a special meaning can be <backslash>-escaped.  Escaped characters shall be treated literally, without special meaning as shell expansion characters or '!', '%', and '#' expansion characters. See Regular Expressions in ex and Replacement Strings in ex for descriptions of command arguments that are regular expressions or replacement strings.
Non-<backslash>-escaped '%' characters appearing in file arguments to any ex command shall be replaced by the current pathname; unescaped '#' characters shall be replaced by the alternate pathname. It shall be an error if '%' or '#' characters appear unescaped in an argument and their corresponding values are not set.
Non-<backslash>-escaped '!'  characters in the arguments to either the ex !  command or the open and visual mode !  command, or in the arguments to the ex read command, where the first non-<blank> after the command name is a '!'  character, or in the arguments to the ex write command where the command name is followed by one or more <blank> characters and the first non-<blank> after the command name is a '!'  character, shall be replaced with the arguments to the last of those three commands as they appeared after all unescaped '%', '#', and '!'  characters were replaced. It shall be an error if '!'  characters appear unescaped in one of these commands and there has been no previous execution of one of these commands.
If an error occurs during the parsing or execution of an ex command:
*  An informational message to this effect shall be written. Execution of the ex command shall stop, and the cursor (for example, the current line and column) shall not be further modified.
*  If the ex command resulted from a map expansion, all characters from that map expansion shall be discarded, except as otherwise specified by the map command.
*  Otherwise, if the ex command resulted from the processing of an EXINIT environment variable, a .exrc file, a :source command, a -c option, or a +command specified to an ex edit, ex, next, or visual command, no further commands from the source of the commands shall be executed.
*  Otherwise, if the ex command resulted from the execution of a buffer or a global or v command, no further commands caused by the execution of the buffer or the global or v command shall be executed.
*  Otherwise, if the ex command was not terminated by a <newline>, all characters up to and including the next non-<backslash>-escaped <newline> shall be discarded.
Input Editing in ex The following symbol is used in this and the following sections to specify command actions:
word      In the POSIX locale, a word consists of a maximal sequence of letters, digits, and underscores, delimited at both ends by characters other than letters, digits, or underscores, or by the beginning or end of a line or the edit buffer.
When accepting input characters from the user, in either ex command mode or ex text input mode, ex shall enable canonical mode input processing, as defined in the System Interfaces volume of POSIX.1‐2017.
If in ex text input mode:
1. If the number edit option is set, ex shall prompt for input using the line number that would be assigned to the line if it is entered, in the format specified for the ex number command.
2. If the autoindent edit option is set, ex shall prompt for input using autoindent characters, as described by the autoindent edit option. autoindent characters shall follow the line number, if any.
If in ex command mode:
1. If the prompt edit option is set, input shall be prompted for using a single ':' character; otherwise, there shall be no prompt.
The input characters in the following sections shall have the following effects on the input line.
Scroll Synopsis:
See the description of the stty eof character in stty.
If the eof character is the first character entered on the line, the line shall be evaluated as if it contained two characters: a <control>‐D and a <newline>.
Otherwise, the eof character shall have no special meaning.
If the cursor follows an autoindent character, the autoindent characters in the line shall be modified so that a part of the next text input character will be displayed on the first column in the line after the previous shiftwidth edit option column boundary, and the user shall be prompted again for input for the same line.
Otherwise, if the cursor follows a '0', which follows an autoindent character, and the '0' was the previous text input character, the '0' and all autoindent characters in the line shall be discarded, and the user shall be prompted again for input for the same line.
Otherwise, if the cursor follows a '^', which follows an autoindent character, and the '^' was the previous text input character, the '^' and all autoindent characters in the line shall be discarded, and the user shall be prompted again for input for the same line. In addition, the autoindent level for the next input line shall be derived from the same line from which the autoindent level for the current input line was derived.
Otherwise, if there are no autoindent or text input characters in the line, the eof character shall be discarded.
<newline> Synopsis:
<newline> <control>-J
Cause the command line to be parsed; <control>‐J shall be mapped to the <newline> for this purpose.
Terminate the current line. If there are no characters other than autoindent characters on the line, all characters on the line shall be discarded.
Prompt for text input on a new line after the current line. If the autoindent edit option is set, an appropriate number of autoindent characters shall be added as a prefix to the line as described by the ex autoindent edit option.
<backslash> Synopsis:
<backslash>
Allow the entry of a subsequent <newline> or <control>‐J as a literal character, removing any special meaning that it may have to the editor during text input mode. The <backslash> character shall be retained and evaluated when the command line is parsed, or retained and included when the input text becomes part of the edit buffer.
<control>‐V Synopsis:
<control>-V
Allow the entry of any subsequent character as a literal character, removing any special meaning that it may have to the editor during text input mode. The <control>‐V character shall be discarded before the command line is parsed or the input text becomes part of the edit buffer.
If the ``literal next'' functionality is performed by the underlying system, it is implementation-defined whether a character other than <control>‐V performs this function.
<control>‐W Synopsis:
<control>-W
Discard the <control>‐W, and the word previous to it in the input line, including any <blank> characters following the word and preceding the <control>‐W.  If the ``word erase'' functionality is performed by the underlying system, it is implementation-defined whether a character other than <control>‐W performs this function.
Command Descriptions in ex The following symbols are used in this section to represent command modifiers. Some of these modifiers can be omitted, in which case the specified defaults shall be used.
1addr     A single line address, given in any of the forms described in Addressing in ex; the default shall be the current line ('.'), unless otherwise specified.
If the line address is zero, it shall be an error, unless otherwise specified in the following command descriptions.
If the edit buffer is empty, and the address is specified with a command other than =, append, insert, open, put, read, or visual, or the address is not zero, it shall be an error.
2addr     Two addresses specifying an inclusive range of lines. If no addresses are specified, the default for 2addr shall be the current line only (".,."), unless otherwise specified in the following command descriptions. If one address is specified, 2addr shall specify that line only, unless otherwise specified in the following command descriptions.
It shall be an error if the first address is greater than the second address.
If the edit buffer is empty, and the two addresses are specified with a command other than the !, write, wq, or xit commands, or either address is not zero, it shall be an error.
count     A positive decimal number. If count is specified, it shall be equivalent to specifying an additional address to the command, unless otherwise specified by the following command descriptions. The additional address shall be equal to the last address specified to the command (either explicitly or by default) plus count-1.
If this would result in an address greater than the last line of the edit buffer, it shall be corrected to equal the last line of the edit buffer.
flags     One or more of the characters '+', '-', '#', 'p', or 'l' (ell). The flag characters can be <blank>-separated, and in any order or combination. The characters '#', 'p', and 'l' shall cause lines to be written in the format specified by the print command with the specified flags.
The lines to be written are as follows:
1. All edit buffer lines written during the execution of the ex &, ~, list, number, open, print, s, visual, and z commands shall be written as specified by flags.
2. After the completion of an ex command with a flag as an argument, the current line shall be written as specified by flags, unless the current line was the last line written by the command.
The characters '+' and '-' cause the value of the current line after the execution of the ex command to be adjusted by the offset address as described in Addressing in ex.  This adjustment shall occur before the current line is written as described in 2. above.
The default for flags shall be none.
buffer    One of a number of named areas for holding text. The named buffers are specified by the alphanumeric characters of the POSIX locale. There shall also be one ``unnamed'' buffer. When no buffer is specified for editor commands that use a buffer, the unnamed buffer shall be used.  Commands that store text into buffers shall store the text as it was before the command took effect, and shall store text occurring earlier in the file before text occurring later in the file, regardless of how the text region was specified. Commands that store text into buffers shall store the text into the unnamed buffer as well as any specified buffer.
In ex commands, buffer names are specified as the name by itself. In open or visual mode commands the name is preceded by a double-quote ('"') character.
If the specified buffer name is an uppercase character, and the buffer contents are to be modified, the buffer shall be appended to rather than being overwritten. If the buffer is not being modified, specifying the buffer name in lowercase and uppercase shall have identical results.
There shall also be buffers named by the numbers 1 through 9. In open and visual mode, if a region of text including characters from more than a single line is being modified by the vi c or d commands, the motion character associated with the c or d commands specifies that the buffer text shall be in line mode, or the commands %, `, /, ?, (, ), N, n, {, or } are used to define a region of text for the c or d commands, the contents of buffers 1 through 8 shall be moved into the buffer named by the next numerically greater value, the contents of buffer 9 shall be discarded, and the region of text shall be copied into buffer 1. This shall be in addition to copying the text into a user-specified buffer or unnamed buffer, or both. Numeric buffers can be specified as a source buffer for open and visual mode commands; however, specifying a numeric buffer as the write target of an open or visual mode command shall have unspecified results.
The text of each buffer shall have the characteristic of being in either line or character mode. Appending text to a non-empty buffer shall set the mode to match the characteristic of the text being appended. Appending text to a buffer shall cause the creation of at least one additional line in the buffer. All text stored into buffers by ex commands shall be in line mode. The ex commands that use buffers as the source of text specify individually how buffers of different modes are handled. Each open or visual mode command that uses buffers for any purpose specifies individually the mode of the text stored into the buffer and how buffers of different modes are handled.
file      Command text used to derive a pathname. The default shall be the current pathname, as defined previously, in which case, if no current pathname has yet been established it shall be an error, except where specifically noted in the individual command descriptions that follow.  If the command text contains any of the characters '~', '{', '[', '*', '?', '$', '"', backquote, single-quote, and <backslash>, it shall be subjected to the process of ``shell expansions'', as described below; if more than a single pathname results and the command expects only one, it shall be an error.
The process of shell expansions in the editor shall be done as follows. The ex utility shall pass two arguments to the program named by the shell edit option; the first shall be -c, and the second shall be the string "echo" and the command text as a single argument. The standard output and standard error of that command shall replace the command text.
!         A character that can be appended to the command name to modify its operation, as detailed in the individual command descriptions. With the exception of the ex read, write, and ! commands, the '!'  character shall only act as a modifier if there are no <blank> characters between it and the command name.
remembered search direction The vi commands N and n begin searching in a forwards or backwards direction in the edit buffer based on a remembered search direction, which is initially unset, and is set by the ex global, v, s, and tag commands, and the vi / and ? commands.
Abbreviate Synopsis:
ab[breviate][lhs rhs]
If lhs and rhs are not specified, write the current list of abbreviations and do nothing more.
Implementations may restrict the set of characters accepted in lhs or rhs, except that printable characters and <blank> characters shall not be restricted. Additional restrictions shall be implementation-defined.
In both lhs and rhs, any character may be escaped with a <control>‐V, in which case the character shall not be used to delimit lhs from rhs, and the escaping <control>‐V shall be discarded.
In open and visual text input mode, if a non-word or <ESC> character that is not escaped by a <control>‐V character is entered after a word character, a check shall be made for a set of characters matching lhs, in the text input entered during this command. If it is found, the effect shall be as if rhs was entered instead of lhs.
The set of characters that are checked is defined as follows:
1. If there are no characters inserted before the word and non-word or <ESC> characters that triggered the check, the set of characters shall consist of the word character.
2. If the character inserted before the word and non-word or <ESC> characters that triggered the check is a word character, the set of characters shall consist of the characters inserted immediately before the triggering characters that are word characters, plus the triggering word character.
3. If the character inserted before the word and non-word or <ESC> characters that triggered the check is not a word character, the set of characters shall consist of the characters that were inserted before the triggering characters that are neither <blank> characters nor word characters, plus the triggering word character.
It is unspecified whether the lhs argument entered for the ex abbreviate and unabbreviate commands is replaced in this fashion. Regardless of whether or not the replacement occurs, the effect of the command shall be as if the replacement had not occurred.
Current line: Unchanged.
Current column: Unchanged.
Append Synopsis:
[1addr] a[ppend][!]
Enter ex text input mode; the input text shall be placed after the specified line. If line zero is specified, the text shall be placed at the beginning of the edit buffer.
This command shall be affected by the number and autoindent edit options; following the command name with '!'  shall cause the autoindent edit option setting to be toggled for the duration of this command only.
Current line: Set to the last input line; if no lines were input, set to the specified line, or to the first line of the edit buffer if a line of zero was specified, or zero if the edit buffer is empty.
Current column: Set to non-<blank>.
Arguments Synopsis:
ar[gs]
Write the current argument list, with the current argument-list entry, if any, between '[' and ']' characters.
Change Synopsis:
[2addr] c[hange][!][count]
Enter ex text input mode; the input text shall replace the specified lines. The specified lines shall be copied into the unnamed buffer, which shall become a line mode buffer.
Current line: Set to the last input line; if no lines were input, set to the line before the first address, or to the first line of the edit buffer if there are no lines preceding the first address, or to zero if the edit buffer is empty.
Change Directory Synopsis:
chd[ir][!][directory] cd[!][directory]
Change the current working directory to directory.
If no directory argument is specified, and the HOME environment variable is set to a non-null and non-empty value, directory shall default to the value named in the HOME environment variable. If the HOME environment variable is empty or is undefined, the default value of directory is implementation-defined.
If no '!'  is appended to the command name, and the edit buffer has been modified since the last complete write, and the current pathname does not begin with a '/', it shall be an error.
Copy Synopsis:
[2addr] co[py] 1addr [flags] [2addr] t 1addr [flags]
Copy the specified lines after the specified destination line; line zero specifies that the lines shall be placed at the beginning of the edit buffer.
Current line: Set to the last line copied.
Delete Synopsis:
[2addr] d[elete][buffer][count][flags]
Delete the specified lines into a buffer (defaulting to the unnamed buffer), which shall become a line-mode buffer.
Flags can immediately follow the command name; see Command Line Parsing in ex.
Current line: Set to the line following the deleted lines, or to the last line in the edit buffer if that line is past the end of the edit buffer, or to zero if the edit buffer is empty.
Edit Synopsis:
e[dit][!][+command][file] ex[!][+command][file]
If no '!'  is appended to the command name, and the edit buffer has been modified since the last complete write, it shall be an error.
If file is specified, replace the current contents of the edit buffer with the current contents of file, and set the current pathname to file. If file is not specified, replace the current contents of the edit buffer with the current contents of the file named by the current pathname. If for any reason the current contents of the file cannot be accessed, the edit buffer shall be empty.
The +command option shall be <blank>-delimited; <blank> characters within the +command can be escaped by preceding them with a <backslash> character. The +command shall be interpreted as an ex command immediately after the contents of the edit buffer have been replaced and the current line and column have been set.
If the edit buffer is empty:
Current line: Set to 0.
Current column: Set to 1.
Otherwise, if executed while in ex command mode or if the +command argument is specified:
Current line: Set to the last line of the edit buffer.
Otherwise, if file is omitted or results in the current pathname:
Current line: Set to the first line of the edit buffer.
Otherwise, if file is the same as the last file edited, the line and column shall be set as follows; if the file was previously edited, the line and column may be set as follows:
Current line: Set to the last value held when that file was last edited. If this value is not a valid line in the new edit buffer, set to the first line of the edit buffer.
Current column: If the current line was set to the last value held when the file was last edited, set to the last value held when the file was last edited.  Otherwise, or if the last value is not a valid column in the new edit buffer, set to non-<blank>.
File Synopsis:
f[ile][file]
If a file argument is specified, the alternate pathname shall be set to the current pathname, and the current pathname shall be set to file.
Write an informational message. If the file has a current pathname, it shall be included in this message; otherwise, the message shall indicate that there is no current pathname. If the edit buffer contains lines, the current line number and the number of lines in the edit buffer shall be included in this message; otherwise, the message shall indicate that the edit buffer is empty. If the edit buffer has been modified since the last complete write, this fact shall be included in this message. If the readonly edit option is set, this fact shall be included in this message. The message may contain other unspecified information.
Global Synopsis:
[2addr] g[lobal] /pattern/ [commands] [2addr] v /pattern/ [commands]
The optional '!'  character after the global command shall be the same as executing the v command.
If pattern is empty (for example, "//") or not specified, the last regular expression used in the editor command shall be used as the pattern.  The pattern can be delimited by <slash> characters (shown in the Synopsis), as well as any non-alphanumeric or non-<blank> other than <backslash>, <vertical-line>, <newline>, or double-quote.
If no lines are specified, the lines shall default to the entire file.
The global and v commands are logically two-pass operations. First, mark the lines within the specified lines for which the line excluding the terminating <newline> matches (global) or does not match (v or global!) the specified pattern. Second, execute the ex commands given by commands, with the current line ('.')  set to each marked line. If an error occurs during this process, or the contents of the edit buffer are replaced (for example, by the ex :edit command) an error message shall be written and no more commands resulting from the execution of this command shall be processed.
Multiple ex commands can be specified by entering multiple commands on a single line using a <vertical-line> to delimit them, or one per line, by escaping each <newline> with a <backslash>.
If no commands are specified:
1. If in ex command mode, it shall be as if the print command were specified.
2. Otherwise, no command shall be executed.
For the append, change, and insert commands, the input text shall be included as part of the command, and the terminating <period> can be omitted if the command ends the list of commands. The open and visual commands can be specified as one of the commands, in which case each marked line shall cause the editor to enter open or visual mode. If open or visual mode is exited using the vi Q command, the current line shall be set to the next marked line, and open or visual mode reentered, until the list of marked lines is exhausted.
The global, v, and undo commands cannot be used in commands.  Marked lines may be deleted by commands executed for lines occurring earlier in the file than the marked lines. In this case, no commands shall be executed for the deleted lines.
If the remembered search direction is not set, the global and v commands shall set it to forward.
The autoprint and autoindent edit options shall be inhibited for the duration of the g or v command.
Current line: If no commands executed, set to the last marked line. Otherwise, as specified for the executed ex commands.
Current column: If no commands are executed, set to non-<blank>; otherwise, as specified for the individual ex commands.
Insert Synopsis:
[1addr] i[nsert][!]
Enter ex text input mode; the input text shall be placed before the specified line. If the line is zero or 1, the text shall be placed at the beginning of the edit buffer.
Current line: Set to the last input line; if no lines were input, set to the line before the specified line, or to the first line of the edit buffer if there are no lines preceding the specified line, or zero if the edit buffer is empty.
Join Synopsis:
[2addr] j[oin][!][count][flags]
If count is specified:
If no address was specified, the join command shall behave as if 2addr were the current line and the current line plus count (.,. + count).
If one address was specified, the join command shall behave as if 2addr were the specified address and the specified address plus count (addr,addr + count).
If two addresses were specified, the join command shall behave as if an additional address, equal to the last address plus count -1 (addr1,addr2,addr2 + count -1), was specified.
If this would result in a second address greater than the last line of the edit buffer, it shall be corrected to be equal to the last line of the edit buffer.
If no count is specified:
If no address was specified, the join command shall behave as if 2addr were the current line and the next line (.,. +1).
If one address was specified, the join command shall behave as if 2addr were the specified address and the next line (addr,addr +1).
Join the text from the specified lines together into a single line, which shall replace the specified lines.
If a '!'  character is appended to the command name, the join shall be without modification of any line, independent of the current locale.
Otherwise, in the POSIX locale, set the current line to the first of the specified lines, and then, for each subsequent line, proceed as follows:
1. Discard leading <space> characters from the line to be joined.
2. If the line to be joined is now empty, delete it, and skip steps 3 through 5.
3. If the current line ends in a <blank>, or the first character of the line to be joined is a ')' character, join the lines without further modification.
4. If the last character of the current line is a '.', join the lines with two <space> characters between them.
5. Otherwise, join the lines with a single <space> between them.
Current line: Set to the first line specified.
List Synopsis:
[2addr] l[ist][count][flags]
This command shall be equivalent to the ex command:
[2addr] p[rint][count] l[flags]
See Print.
Map Synopsis:
map[!][lhs rhs]
If lhs and rhs are not specified:
1. If '!'  is specified, write the current list of text input mode maps.
2. Otherwise, write the current list of command mode maps.
3. Do nothing more.
Implementations may restrict the set of characters accepted in lhs or rhs, except that printable characters and <blank> characters shall not be restricted. Additional restrictions shall be implementation-defined. In both lhs and rhs, any character can be escaped with a <control>‐V, in which case the character shall not be used to delimit lhs from rhs, and the escaping <control>‐V shall be discarded.
If the character '!'  is appended to the map command name, the mapping shall be effective during open or visual text input mode rather than open or visual command mode. This allows lhs to have two different map definitions at the same time: one for command mode and one for text input mode.
For command mode mappings:
When the lhs is entered as any part of a vi command in open or visual mode (but not as part of the arguments to the command), the action shall be as if the corresponding rhs had been entered.
If any character in the command, other than the first, is escaped using a <control>‐V character, that character shall not be part of a match to an lhs.
It is unspecified whether implementations shall support map commands where the lhs is more than a single character in length, where the first character of the lhs is printable.
If lhs contains more than one character and the first character is '#', followed by a sequence of digits corresponding to a numbered function key, then when this function key is typed it shall be mapped to rhs.  Characters other than digits following a '#' character also represent the function key named by the characters in the lhs following the '#' and may be mapped to rhs.  It is unspecified how function keys are named or what function keys are supported.
For text input mode mappings:
When the lhs is entered as any part of text entered in open or visual text input modes, the action shall be as if the corresponding rhs had been entered.
If any character in the input text is escaped using a <control>‐V character, that character shall not be part of a match to an lhs.
It is unspecified whether the lhs text entered for subsequent map or unmap commands is replaced with the rhs text for the purposes of the screen display; regardless of whether or not the display appears as if the corresponding rhs text was entered, the effect of the command shall be as if the lhs text was entered.
If only part of the lhs is entered, it is unspecified how long the editor will wait for additional, possibly matching characters before treating the already entered characters as not matching the lhs.
The rhs characters shall themselves be subject to remapping, unless otherwise specified by the remap edit option, except that if the characters in lhs occur as prefix characters in rhs, those characters shall not be remapped.
On block-mode terminals, the mapping need not occur immediately (for example, it may occur after the terminal transmits a group of characters to the system), but it shall achieve the same results as if it occurred immediately.
Mark Synopsis:
[1addr] ma[rk] character [1addr] k character
Implementations shall support character values of a single lowercase letter of the POSIX locale and the backquote and single-quote characters; support of other characters is implementation-defined.
If executing the vi m command, set the specified mark to the current line and 1-based numbered character referenced by the current column, if any; otherwise, column position 1.
Otherwise, set the specified mark to the specified line and 1-based numbered first non-<blank> non-<newline> in the line, if any; otherwise, the last non-<newline> in the line, if any; otherwise, column position 1.
The mark shall remain associated with the line until the mark is reset or the line is deleted. If a deleted line is restored by a subsequent undo command, any marks previously associated with the line, which have not been reset, shall be restored as well. Any use of a mark not associated with a current line in the edit buffer shall be an error.
The marks ` and ' shall be set as described previously, immediately before the following events occur in the editor:
1. The use of '$' as an ex address
2. The use of a positive decimal number as an ex address
3. The use of a search command as an ex address
4. The use of a mark reference as an ex address
5. The use of the following open and visual mode commands: <control>‐], %, (, ), [, ], {, }
6. The use of the following open and visual mode commands: ', G, H, L, M, z if the current line will change as a result of the command
7. The use of the open and visual mode commands: /, ?, N, `, n if the current line or column will change as a result of the command
8. The use of the ex mode commands: z, undo, global, v
For rules 1., 2., 3., and 4., the ` and ' marks shall not be set if the ex command is parsed as specified by rule 6.a. in Command Line Parsing in ex.
For rules 5., 6., and 7., the ` and ' marks shall not be set if the commands are used as motion commands in open and visual mode.
For rules 1., 2., 3., 4., 5., 6., 7., and 8., the ` and ' marks shall not be set if the command fails.
The ` and ' marks shall be set as described previously, each time the contents of the edit buffer are replaced (including the editing of the initial buffer), if in open or visual mode, or if in ex mode and the edit buffer is not empty, before any commands or movements (including commands or movements specified by the -c or -t options or the +command argument) are executed on the edit buffer. If in open or visual mode, the marks shall be set as if executing the vi m command; otherwise, as if executing the ex mark command.
When changing from ex mode to open or visual mode, if the ` and ' marks are not already set, the ` and ' marks shall be set as described previously.
Move Synopsis:
[2addr] m[ove] 1addr [flags]
Move the specified lines after the specified destination line. A destination of line zero specifies that the lines shall be placed at the beginning of the edit buffer. It shall be an error if the destination line is within the range of lines to be moved.
Current line: Set to the last of the moved lines.
Next Synopsis:
n[ext][!][+command][file ...]