Insert

Nvim :help pages, generated from source using the tree-sitter-vimdoc parser.


Insert-mode Inserting and replacing text mode-ins-repl
Most of this file is about Insert and Replace mode. At the end are a few commands for inserting text in other ways.
An overview of the most often used commands can be found in chapter 24 of the user manual usr_24.txt.
Also see 'virtualedit', for moving the cursor to positions where there is no character. Useful for editing a table.

1. Special keys ins-special-keys

In Insert and Replace mode, the following characters have a special meaning; other characters are inserted directly. To insert one of these special characters into the buffer, precede it with CTRL-V. To insert a <Nul> character use "CTRL-V CTRL-@" or "CTRL-V 000". On some systems, you have to use "CTRL-V 003" to insert a CTRL-C.Note: When CTRL-V is mapped you can often use CTRL-Q instead i_CTRL-Q.
If you are working in a special language mode when inserting text, see the 'langmap' option, 'langmap', on how to avoid switching this mode on and off all the time.
char action

i_CTRL-[ i_<Esc>

<Esc> or CTRL-[ End insert or Replace mode, go back to Normal mode. Finish abbreviation. Note: If your <Esc> key is hard to hit, try CTRL-[ instead. i_META i_ALT ALT (META) may act like <Esc> if the chord is not mapped. For example <A-x> acts like <Esc>x if <A-x> does not have an insert-mode mapping. i_CTRL-C CTRL-C Quit insert mode, go back to Normal mode. Do not check for abbreviations. Does not trigger the InsertLeave autocommand event.
i_CTRL-@ CTRL-@ Insert previously inserted text and stop insert.
i_CTRL-A CTRL-A Insert previously inserted text.
i_CTRL-H i_<BS> i_BS <BS> or CTRL-H Delete the character before the cursor (see i_backspacing about joining lines). i_<Del> i_DEL <Del> Delete the character under the cursor. If the cursor is at the end of the line, and the 'backspace' option includes "eol" (the default), delete the <EOL>; the next line is appended after the current one. i_CTRL-W CTRL-W Delete the word before the cursor (see i_backspacing about joining lines). See the section "word motions", word-motions, for the definition of a word. i_CTRL-W-default By default, sets a new undo point before deleting. default-mappings i_CTRL-U CTRL-U Delete all entered characters before the cursor in the current line. If there are no newly entered characters and 'backspace' is not empty, delete all characters before the cursor in the current line. If C-indenting is enabled the indent will be adjusted if the line becomes blank. See i_backspacing about joining lines. i_CTRL-U-default By default, sets a new undo point before deleting. default-mappings i_CTRL-I i_<Tab> i_Tab <Tab> or CTRL-I Insert a tab. If the 'expandtab' option is on, the equivalent number of spaces is inserted (use CTRL-V <Tab> to avoid the expansion; use CTRL-Q <Tab> if CTRL-V is mapped i_CTRL-Q). See also the 'smarttab' option and ins-expandtab. i_CTRL-J i_<NL> <NL> or CTRL-J Begin new line. i_CTRL-M i_<CR> <CR> or CTRL-M Begin new line. i_CTRL-K CTRL-K {char1} [char2] Enter digraph (see digraphs). When {char1} is a special key, the code for that key is inserted in <> form. For example, the string "<S-Space>" can be entered by typing <C-K><S-Space> (two keys). Neither char is considered for mapping.
CTRL-N Find next keyword (see i_CTRL-N). CTRL-P Find previous keyword (see i_CTRL-P).
CTRL-R {register} i_CTRL-R Insert the contents of a register. Between typing CTRL-R and the second character, '"' will be displayed to indicate that you are expected to enter the name of a register. The text is inserted as if you typed it, but mappings and abbreviations are not used. If you have options like 'textwidth', 'formatoptions', or 'autoindent' set, this will influence what will be inserted. This is different from what happens with the "p" command and pasting with the mouse. Special registers: '"' the unnamed register, containing the text of the last delete or yank '%' the current file name '#' the alternate file name "*" the clipboard contents (X11: primary selection) '+' the clipboard contents '/' the last search pattern ':' the last command-line '.' the last inserted text i_CTRL-R_- '-' the last small (less than a line) delete register. This is repeatable using . since it remembers the register to put instead of the literal text to insert. i_CTRL-R_= '=' the expression register: you are prompted to enter an expression (see expression) Note that 0x80 (128 decimal) is used for special keys. E.g., you can use this to move the cursor up: CTRL-R ="\<Up>" Use CTRL-R CTRL-R to insert text literally. When the result is a List the items are used as lines. They can have line breaks inside too. When the result is a Float it's automatically converted to a String. When append() or setline() is invoked the undo sequence will be broken. See registers about registers.
CTRL-R CTRL-R {register} i_CTRL-R_CTRL-R Insert the contents of a register. Works like using a single CTRL-R, but the text is inserted literally, not as if typed. This differs when the register contains characters like <BS>. Example, where register a contains "ab^Hc":
CTRL-R a                results in "ac".
CTRL-R CTRL-R a                results in "ab^Hc".
Options 'textwidth', 'formatoptions', etc. still apply. If you also want to avoid these, use CTRL-R CTRL-O, see below. The '.' register (last inserted text) is still inserted as typed. After this command, the '.' register contains the text from the register as if it was inserted by typing it.
CTRL-R CTRL-O {register} i_CTRL-R_CTRL-O Insert the contents of a register literally and don't auto-indent. Does the same as pasting with the mouse <MiddleMouse>. When the register is linewise this will insert the text above the current line, like with P. The '.' register (last inserted text) is still inserted as typed. After this command, the '.' register contains the command typed and not the text. I.e., the literals "^R^O" and not the text from the register. Does not replace characters in Replace-mode!
CTRL-R CTRL-P {register} i_CTRL-R_CTRL-P Insert the contents of a register literally and fix the indent, like [<MiddleMouse>. The '.' register (last inserted text) is still inserted as typed. After this command, the '.' register contains the command typed and not the text. I.e., the literals "^R^P" and not the text from the register. Does not replace characters in Replace-mode!
i_CTRL-T CTRL-T Insert one shiftwidth of indent at the start of the current line. The indent is always rounded to a 'shiftwidth'. i_CTRL-D CTRL-D Delete one shiftwidth of indent at the start of the current line. The indent is always rounded to a 'shiftwidth'.
i_0_CTRL-D 0 CTRL-D Delete all indent in the current line.
i_^_CTRL-D ^ CTRL-D Delete all indent in the current line. The indent is restored in the next line. This is useful when inserting a label.
i_CTRL-V CTRL-V Insert next non-digit literally. It's also possible to enter the decimal, octal or hexadecimal value of a character i_CTRL-V_digit. The characters typed right after CTRL-V are not considered for mapping. For special keys, the CTRL modifier may be included into the key to produce a control character. If there is no control character for the key then its key-notation is inserted. Note: When CTRL-V is mapped (e.g., to paste text) you can often use CTRL-Q instead i_CTRL-Q.
i_CTRL-Q CTRL-Q Same as CTRL-V. Note: Some terminal connections may eat CTRL-Q, it doesn't work then. It does work in the GUI.

CTRL-SHIFT-V i_CTRL-SHIFT-V i_CTRL-SHIFT-Q

CTRL-SHIFT-Q Works just like CTRL-V, but do not try to include the CTRL modifier into the key.
CTRL-X Enter CTRL-X mode. This is a sub-mode where commands can be given to complete words or scroll the window. See i_CTRL-X and ins-completion.
i_CTRL-E CTRL-E Insert the character which is below the cursor. i_CTRL-Y CTRL-Y Insert the character which is above the cursor. Note that for CTRL-E and CTRL-Y 'textwidth' is not used, to be able to copy characters from a long line.
i_CTRL-_ CTRL-_ Switch between insert direction, by toggling 'revins', as follows:
When in a rightleft window, 'revins' is toggled, since English will likely be inserted in this case.
When in a norightleft window, 'revins' is toggled, since a rightleft language will likely be inserted in this case.
CTRL-_ moves the cursor to the end of the typed text.
This command is only available when the 'allowrevins' option is set. Please refer to rileft.txt for more information about right-to-left mode.
i_CTRL-^ CTRL-^ Toggle the use of typing language characters. When language :lmap mappings are defined:
If 'iminsert' is 1 (langmap mappings used) it becomes 0 (no langmap mappings used).
If 'iminsert' has another value it becomes 1, thus langmap mappings are enabled. When no language mappings are defined:
If 'iminsert' is 2 (Input Method used) it becomes 0 (no Input Method used).
If 'iminsert' has another value it becomes 2, thus the Input Method is enabled. When set to 1, the value of the "b:keymap_name" variable, the 'keymap' option or "<lang>" appears in the status line. The language mappings are normally used to type characters that are different from what the keyboard produces. The 'keymap' option can be used to install a whole number of them.
i_CTRL-] CTRL-] Trigger abbreviation, without inserting a character.
i_<Insert> <Insert> Toggle between Insert and Replace mode.

i_backspacing

The effect of the <BS>, CTRL-W, and CTRL-U depend on the 'backspace' option (unless 'revins' is set). This is a comma-separated list of items:
item action
indent allow backspacing over autoindent eol allow backspacing over end-of-line (join lines) start allow backspacing over the start position of insert; CTRL-W and CTRL-U stop once at the start position
When 'backspace' is empty, Vi compatible backspacing is used. You cannot backspace over autoindent, before column 1 or before where insert started.
For backwards compatibility the values "0", "1", "2" and "3" are also allowed, see 'backspace'.
If the 'backspace' option does contain "eol" and the cursor is in column 1 when one of the three keys is used, the current line is joined with the previous line. This effectively deletes the <EOL> in front of the cursor.
i_CTRL-V_digit With CTRL-V the decimal, octal or hexadecimal value of a character can be entered directly. This way you can enter any character, except a line break (<NL>, value 10). There are five ways to enter the character value:
first char mode max nr of chars max value
(none) decimal 3 255 o or O octal 3 377 (255) x or X hexadecimal 2 ff (255) u hexadecimal 4 ffff (65535) U hexadecimal 8 7fffffff (2147483647)
Normally you would type the maximum number of characters. Thus to enter a space (value 32) you would type <C-V>032. You can omit the leading zero, in which case the character typed after the number must be a non-digit. This happens for the other modes as well: As soon as you type a character that is invalid for the mode, the value before it will be used and the "invalid" character is dealt with in the normal way.
If you enter a value of 10, it will end up in the file as a 0. The 10 is a <NL>, which is used internally to represent the <Nul> character. When writing the buffer to a file, the <NL> character is translated into <Nul>. The <NL> character is written at the end of each line. Thus if you want to insert a <NL> character in a file you will have to make a line break. Also see 'fileformat'.
i_CTRL-X insert_expand CTRL-X enters a sub-mode where several commands can be used. Most of these commands do keyword completion; see ins-completion.
Two commands can be used to scroll the window up or down, without exiting insert mode:
i_CTRL-X_CTRL-E CTRL-X CTRL-E scroll window one line up. When doing completion look here: complete_CTRL-E
i_CTRL-X_CTRL-Y CTRL-X CTRL-Y scroll window one line down. When doing completion look here: complete_CTRL-Y
After CTRL-X is pressed, each CTRL-E (CTRL-Y) scrolls the window up (down) by one line unless that would cause the cursor to move from its current position in the file. As soon as another key is pressed, CTRL-X mode is exited and that key is interpreted as in Insert mode.

2. Special special keys ins-special-special

The following keys are special. They stop the current insert, do something, and then restart insertion. This means you can do something without getting out of Insert mode. This is very handy if you prefer to use the Insert mode all the time, just like editors that don't have a separate Normal mode. You can use CTRL-O if you want to map a function key to a command.
The changes (inserted or deleted characters) before and after these keys can be undone separately. Only the last change can be redone and always behaves like an "i" command.
char action

<Up> cursor one line up i_<Up>

<Down> cursor one line down i_<Down> CTRL-G <Up> cursor one line up, insert start column i_CTRL-G_<Up> CTRL-G k cursor one line up, insert start column i_CTRL-G_k CTRL-G CTRL-K cursor one line up, insert start column i_CTRL-G_CTRL-K CTRL-G <Down> cursor one line down, insert start column i_CTRL-G_<Down> CTRL-G j cursor one line down, insert start column i_CTRL-G_j CTRL-G CTRL-J cursor one line down, insert start column i_CTRL-G_CTRL-J <Left> cursor one character left i_<Left> <Right> cursor one character right i_<Right> <S-Left> cursor one word back (like "b" command) i_<S-Left> <C-Left> cursor one word back (like "b" command) i_<C-Left> <S-Right> cursor one word forward (like "w" command) i_<S-Right> <C-Right> cursor one word forward (like "w" command) i_<C-Right> <Home> cursor to first char in the line i_<Home> <End> cursor to after last char in the line i_<End> <C-Home> cursor to first char in the file i_<C-Home> <C-End> cursor to after last char in the file i_<C-End> <LeftMouse> cursor to position of mouse click i_<LeftMouse> <S-Up> move window one page up i_<S-Up> <PageUp> move window one page up i_<PageUp> <S-Down> move window one page down i_<S-Down> <PageDown> move window one page down i_<PageDown> <ScrollWheelDown> move window three lines down i_<ScrollWheelDown> <S-ScrollWheelDown> move window one page down i_<S-ScrollWheelDown> <ScrollWheelUp> move window three lines up i_<ScrollWheelUp> <S-ScrollWheelUp> move window one page up i_<S-ScrollWheelUp> <ScrollWheelLeft> move window six columns left i_<ScrollWheelLeft> <S-ScrollWheelLeft> move window one page left i_<S-ScrollWheelLeft> <ScrollWheelRight> move window six columns right i_<ScrollWheelRight> <S-ScrollWheelRight> move window one page right i_<S-ScrollWheelRight> CTRL-O execute one command, return to Insert mode i_CTRL-O CTRL-\ CTRL-O like CTRL-O but don't move the cursor i_CTRL-\_CTRL-O CTRL-G u close undo sequence, start new change i_CTRL-G_u CTRL-G U don't start a new undo block with the next i_CTRL-G_U left/right cursor movement, if the cursor stays within the same line

The CTRL-O command sometimes has a side effect: If the cursor was beyond the end of the line, it will be put on the last character in the line. In mappings it's often better to use <Esc> (first put an "x" in the text, <Esc> will then always put the cursor on it). Or use CTRL-\ CTRL-O, but then beware of the cursor possibly being beyond the end of the line. Note that the command following CTRL-\ CTRL-O can still move the cursor, it is not restored to its original position.
The CTRL-O command takes you to Normal mode. If you then use a command enter Insert mode again it normally doesn't nest. Thus when typing "a<C-O>a" and then <Esc> takes you back to Normal mode, you do not need to type <Esc> twice. An exception is when not typing the command, e.g. when executing a mapping or sourcing a script. This makes mappings work that briefly switch to Insert mode.
The shifted cursor keys are not available on all terminals.
Another side effect is that a count specified before the "i" or "a" command is ignored. That is because repeating the effect of the command after CTRL-O is too complicated.
An example for using CTRL-G u:
:inoremap <C-H> <C-G>u<C-H>
This redefines the backspace key to start a new undo sequence. You can now undo the effect of the backspace key, without changing what you typed before that, with CTRL-O u. Another example:
:inoremap <CR> <C-]><C-G>u<CR>
This starts a new undo block at each line break. It also expands abbreviations before this.
An example for using CTRL-G U:
inoremap <Left>  <C-G>U<Left>
inoremap <Right> <C-G>U<Right>
inoremap <expr> <Home> col('.') == match(getline('.'), '\S') + 1 ?
 \ repeat('<C-G>U<Left>', col('.') - 1) :
 \ (col('.') < match(getline('.'), '\S') ?
 \     repeat('<C-G>U<Right>', match(getline('.'), '\S') + 0) :
 \     repeat('<C-G>U<Left>', col('.') - 1 - match(getline('.'), '\S')))
inoremap <expr> <End> repeat('<C-G>U<Right>', col('$') - col('.'))
inoremap ( ()<C-G>U<Left>
This makes it possible to use the cursor keys in Insert mode, without starting a new undo block and therefore using . (redo) will work as expected. Also entering a text like (with the "(" mapping from above):
Lorem ipsum (dolor
will be repeatable by using . to the expected
Lorem ipsum (dolor)
Using CTRL-O splits undo: the text typed before and after it is undone separately. If you want to avoid this (e.g., in a mapping) you might be able to use CTRL-R = i_CTRL-R. E.g., to call a function:
:imap <F2> <C-R>=MyFunc()<CR>
When the 'whichwrap' option is set appropriately, the <Left> and <Right> keys on the first/last character in the line make the cursor wrap to the previous/next line.
The CTRL-G j and CTRL-G k commands can be used to insert text in front of a column. Example:
int i;
int j;
Position the cursor on the first "int", type "istatic <C-G>j ". The result is:
static int i;
       int j;
When inserting the same text in front of the column in every line, use the Visual blockwise command "I" v_b_I.
The 'textwidth' option can be used to automatically break a line before it gets too long. Set the 'textwidth' option to the desired maximum line length. If you then type more characters (not spaces or tabs), the last word will be put on a new line (unless it is the only word on the line). If you set 'textwidth' to 0, this feature is disabled.
The 'wrapmargin' option does almost the same. The difference is that 'textwidth' has a fixed width while 'wrapmargin' depends on the width of the screen. When using 'wrapmargin' this is equal to using 'textwidth' with a value equal to (columns - 'wrapmargin'), where columns is the width of the screen.
When 'textwidth' and 'wrapmargin' are both set, 'textwidth' is used.
If you don't really want to break the line, but view the line wrapped at a convenient place, see the 'linebreak' option.
The line is only broken automatically when using Insert mode, or when appending to a line. When in replace mode and the line length is not changed, the line will not be broken.
Long lines are broken if you enter a non-white character after the margin. The situations where a line will be broken can be restricted by adding characters to the 'formatoptions' option: "l" Only break a line if it was not longer than 'textwidth' when the insert started. "v" Only break at a white character that has been entered during the current insert command. This is mostly Vi-compatible. "lv" Only break if the line was not longer than 'textwidth' when the insert started and only at a white character that has been entered during the current insert command. Only differs from "l" when entering non-white characters while crossing the 'textwidth' boundary.
Normally an internal function will be used to decide where to break the line. If you want to do it in a different way set the 'formatexpr' option to an expression that will take care of the line break.
If you want to format a block of text, you can use the "gq" operator. Type "gq" and a movement command to move the cursor to the end of the block. In many cases, the command "gq}" will do what you want (format until the end of paragraph). Alternatively, you can use "gqap", which will format the whole paragraph, no matter where the cursor currently is. Or you can use Visual mode: hit "v", move to the end of the block, and type "gq". See also gq.
If the 'expandtab' option is on, spaces will be used to fill the amount of whitespace of the tab. If you want to enter a real <Tab>, type CTRL-V first (use CTRL-Q when CTRL-V is mapped i_CTRL-Q). The 'expandtab' option is off by default. Note that in Replace mode, a single character is replaced with several spaces. The result of this is that the number of characters in the line increases. Backspacing will delete one space at a time. The original character will be put back for only one space that you backspace over (the last one).
ins-smarttab When the 'smarttab' option is on, a <Tab> inserts 'shiftwidth' positions at the beginning of a line and 'tabstop' positions in other places. This means that often spaces instead of a <Tab> character are inserted. When 'smarttab' is off, a <Tab> always inserts 'tabstop' positions, and 'shiftwidth' is only used for ">>" and the like.
ins-softtabstop When the 'softtabstop' option is non-zero, a <Tab> inserts 'softtabstop' positions, and a <BS> used to delete white space, will delete 'softtabstop' positions. This feels like 'tabstop' was set to 'softtabstop', but a real <Tab> character still takes 'tabstop' positions, so your file will still look correct when used by other applications.
If 'softtabstop' is non-zero, a <BS> will try to delete as much white space to move to the previous 'softtabstop' position, except when the previously inserted character is a space, then it will only delete the character before the cursor. Otherwise you cannot always delete a single character before the cursor. You will have to delete 'softtabstop' characters first, and then type extra spaces to get where you want to be.
Enter Replace mode with the "R" command in normal mode.
In Replace mode, one character in the line is deleted for every character you type. If there is no character to delete (at the end of the line), the typed character is appended (as in Insert mode). Thus the number of characters in a line stays the same until you get to the end of the line. If a <NL> is typed, a line break is inserted and no character is deleted.
Be careful with <Tab> characters. If you type a normal printing character in its place, the number of characters is still the same, but the number of columns will become smaller.
If you delete characters in Replace mode (with <BS>, CTRL-W, or CTRL-U), what happens is that you delete the changes. The characters that were replaced are restored. If you had typed past the existing text, the characters you added are deleted. This is effectively a character-at-a-time undo.
If the 'expandtab' option is on, a <Tab> will replace one character with several spaces. The result of this is that the number of characters in the line increases. Backspacing will delete one space at a time. The original character will be put back for only one space that you backspace over (the last one).

6. Virtual Replace mode vreplace-mode Virtual-Replace-mode

Enter Virtual Replace mode with the "gR" command in normal mode.
Virtual Replace mode is similar to Replace mode, but instead of replacing actual characters in the file, you are replacing screen real estate, so that characters further on in the file never appear to move.
So if you type a <Tab> it may replace several normal characters, and if you type a letter on top of a <Tab> it may not replace anything at all, since the <Tab> will still line up to the same place as before.
Typing a <NL> still doesn't cause characters later in the file to appear to move. The rest of the current line will be replaced by the <NL> (that is, they are deleted), and replacing continues on the next line. A new line is NOT inserted unless you go past the end of the file.
Interesting effects are seen when using CTRL-T and CTRL-D. The characters before the cursor are shifted sideways as normal, but characters later in the line still remain still. CTRL-T will hide some of the old line under the shifted characters, but CTRL-D will reveal them again.
As with Replace mode, using <BS> etc will bring back the characters that were replaced. This still works in conjunction with 'smartindent', CTRL-T and CTRL-D, 'expandtab', 'smarttab', 'softtabstop', etc.
In 'list' mode, Virtual Replace mode acts as if it was not in 'list' mode, unless "L" is in 'cpoptions'.
Note that the only situations for which characters beyond the cursor should appear to move are in List mode 'list', and occasionally when 'wrap' is set (and the line changes length to become shorter or wider than the width of the screen). In other cases spaces may be inserted to avoid following characters to move.
This mode is very useful for editing <Tab> separated columns in tables, for entering new data while keeping all the columns aligned.

7. Insert mode completion ins-completion

In Insert and Replace mode, there are several commands to complete part of a keyword or line that has been typed. This is useful if you are using complicated keywords (e.g., function names with capitals and underscores).
Completion can be done for:
1. Whole lines i_CTRL-X_CTRL-L 2. keywords in the current file i_CTRL-X_CTRL-N 3. keywords in 'dictionary' i_CTRL-X_CTRL-K 4. keywords in 'thesaurus', thesaurus-style i_CTRL-X_CTRL-T 5. keywords in the current and included files i_CTRL-X_CTRL-I 6. tags i_CTRL-X_CTRL-] 7. file names i_CTRL-X_CTRL-F 8. definitions or macros i_CTRL-X_CTRL-D 9. Vim command-line i_CTRL-X_CTRL-V 10. User defined completion i_CTRL-X_CTRL-U 11. omni completion i_CTRL-X_CTRL-O 12. Spelling suggestions i_CTRL-X_s 13. keywords in 'complete' i_CTRL-N i_CTRL-P
Additionally, i_CTRL-X_CTRL-Z stops completion without changing the text.
All these, except CTRL-N and CTRL-P, are done in CTRL-X mode. This is a sub-mode of Insert and Replace modes. You enter CTRL-X mode by typing CTRL-X and one of the CTRL-X commands. You exit CTRL-X mode by typing a key that is not a valid CTRL-X mode command. Valid keys are the CTRL-X command itself, CTRL-N (next), and CTRL-P (previous).
To get the current completion information, complete_info() can be used. Also see the 'infercase' option if you want to adjust the case of the match.
complete_CTRL-E When completion is active you can use CTRL-E to stop it and go back to the originally typed text. The CTRL-E will not be inserted.
complete_CTRL-Y When the popup menu is displayed you can use CTRL-Y to stop completion and accept the currently selected entry. The CTRL-Y is not inserted. Typing a space, Enter, or some other unprintable character will leave completion mode and insert that typed character.
When the popup menu is displayed there are a few more special keys, see popupmenu-keys.
Note: The keys that are valid in CTRL-X mode are not mapped. This allows for :map <C-F> <C-X><C-F> to work. The key that ends CTRL-X mode (any key that is not a valid CTRL-X mode command) is mapped. Also, when doing completion with 'complete' mappings apply as usual.
E565 Note: While completion is active Insert mode can't be used recursively and buffer text cannot be changed. Mappings that somehow invoke ":normal i.." will generate an E565 error.
The following mappings are suggested to make typing the completion commands a bit easier (although they will hide other commands):
:inoremap <C-]> <C-X><C-]>
:inoremap <C-F> <C-X><C-F>
:inoremap <C-D> <C-X><C-D>
:inoremap <C-L> <C-X><C-L>
As a special case, typing CTRL-R to perform register insertion (see i_CTRL-R) will not exit CTRL-X mode. This is primarily to allow the use of the '=' register to call some function to determine the next operation. If the contents of the register (or result of the '=' register evaluation) are not valid CTRL-X mode keys, then CTRL-X mode will be exited as if those keys had been typed.
For example, the following will map <Tab> to either actually insert a <Tab> if the current line is currently only whitespace, or start/continue a CTRL-N completion operation:
function! CleverTab()
   if strpart( getline('.'), 0, col('.')-1 ) =~ '^\s*$'
      return "\<Tab>"
   else
      return "\<C-N>"
   endif
endfunction
inoremap <Tab> <C-R>=CleverTab()<CR>
Completing whole lines compl-whole-line
i_CTRL-X_CTRL-L CTRL-X CTRL-L Search backwards for a line that starts with the same characters as those in the current line before the cursor. Indent is ignored. The matching line is inserted in front of the cursor. The 'complete' option is used to decide which buffers are searched for a match. Both loaded and unloaded buffers are used. CTRL-L or CTRL-P Search backwards for next matching line. This line replaces the previous matching line.
CTRL-N Search forward for next matching line. This line replaces the previous matching line.
CTRL-X CTRL-L After expanding a line you can additionally get the line next to it by typing CTRL-X CTRL-L again, unless a double CTRL-X is used. Only works for loaded buffers.
Completing keywords in current file compl-current
i_CTRL-X_CTRL-P i_CTRL-X_CTRL-N CTRL-X CTRL-N Search forwards for words that start with the keyword in front of the cursor. The found keyword is inserted in front of the cursor.
CTRL-X CTRL-P Search backwards for words that start with the keyword in front of the cursor. The found keyword is inserted in front of the cursor.
CTRL-N Search forward for next matching keyword. This keyword replaces the previous matching keyword.
CTRL-P Search backwards for next matching keyword. This keyword replaces the previous matching keyword.
CTRL-X CTRL-N or CTRL-X CTRL-P Further use of CTRL-X CTRL-N or CTRL-X CTRL-P will copy the words following the previous expansion in other contexts unless a double CTRL-X is used.
If there is a keyword in front of the cursor (a name made out of alphabetic characters and characters in 'iskeyword'), it is used as the search pattern, with "\<" prepended (meaning: start of a word). Otherwise "\<\k\k" is used as search pattern (start of any keyword of at least two characters).
In Replace mode, the number of characters that are replaced depends on the length of the matched string. This works like typing the characters of the matched string in Replace mode.
If there is not a valid keyword character before the cursor, any keyword of at least two characters is matched. e.g., to get: printf("(%g, %g, %g)", vector[0], vector[1], vector[2]); just type: printf("(%g, %g, %g)", vector[0], ^P[1], ^P[2]);
The search wraps around the end of the file, the value of 'wrapscan' is not used here.
Multiple repeats of the same completion are skipped; thus a different match will be inserted at each CTRL-N and CTRL-P (unless there is only one matching keyword).
Single character matches are never included, as they usually just get in the way of what you were really after. e.g., to get: printf("name = %s\n", name); just type: printf("name = %s\n", n^P); or even: printf("name = %s\n", ^P); The 'n' in '\n' is skipped.
After expanding a word, you can use CTRL-X CTRL-P or CTRL-X CTRL-N to get the word following the expansion in other contexts. These sequences search for the text just expanded and further expand by getting an extra word. This is useful if you need to repeat a sequence of complicated words. Although CTRL-P and CTRL-N look just for strings of at least two characters, CTRL-X CTRL-P and CTRL-X CTRL-N can be used to expand words of just one character. e.g., to get: M&eacute;xico you can type: M^N^P^X^P^X^P CTRL-N starts the expansion and then CTRL-P takes back the single character "M", the next two CTRL-X CTRL-P's get the words "&eacute" and ";xico".
If the previous expansion was split, because it got longer than 'textwidth', then just the text in the current line will be used.
If the match found is at the end of a line, then the first word in the next line will be inserted and the message "Word from other line" displayed, if this word is accepted the next CTRL-X CTRL-P or CTRL-X CTRL-N will search for those lines starting with this word.
Completing keywords in 'dictionary' compl-dictionary
i_CTRL-X_CTRL-K CTRL-X CTRL-K Search the files given with the 'dictionary' option for words that start with the keyword in front of the cursor. This is like CTRL-N, but only the dictionary files are searched, not the current file. The found keyword is inserted in front of the cursor. This could potentially be pretty slow, since all matches are found before the first match is used. By default, the 'dictionary' option is empty. For suggestions where to find a list of words, see the 'dictionary' option. 'ignorecase', 'smartcase' and 'infercase' apply.
CTRL-K or CTRL-N Search forward for next matching keyword. This keyword replaces the previous matching keyword.
CTRL-P Search backwards for next matching keyword. This keyword replaces the previous matching keyword.
Completing words in 'thesaurus' compl-thesaurus
i_CTRL-X_CTRL-T CTRL-X CTRL-T Works as CTRL-X CTRL-K, but in a special way. It uses the 'thesaurus' option instead of 'dictionary'. If a match is found in the thesaurus file, all the remaining words on the same line are included as matches, even though they don't complete the word. Thus a word can be completely replaced.
CTRL-T or CTRL-N Search forward for next matching keyword. This keyword replaces the previous matching keyword.
CTRL-P Search backwards for next matching keyword. This keyword replaces the previous matching keyword.
In the file used by the 'thesaurus' option each line in the file should contain words with similar meaning, separated by non-keyword characters (white space is preferred). Maximum line length is 510 bytes.
For an example, imagine the 'thesaurus' file has a line like this:
angry furious mad enraged
Placing the cursor after the letters "ang" and typing CTRL-X CTRL-T would complete the word "angry"; subsequent presses would change the word to "furious", "mad" etc.
Other uses include translation between two languages, or grouping API functions by keyword.
An English word list was added to this github issue: https://github.com/vim/vim/issues/629#issuecomment-443293282 Unpack thesaurus_pkg.zip, put the thesaurus.txt file somewhere, e.g. ~/.vim/thesaurus/english.txt, and the 'thesaurus' option to this file name.
Completing keywords with 'thesaurusfunc' compl-thesaurusfunc
If the 'thesaurusfunc' option is set, then the user specified function is invoked to get the list of completion matches and the 'thesaurus' option is not used. See complete-functions for an explanation of how the function is invoked and what it should return.
Here is an example that uses the "aiksaurus" command (provided by Magnus Groß):
func Thesaur(findstart, base)
  if a:findstart
    return searchpos('\<', 'bnW', line('.'))[1] - 1
  endif
  let res = []
  let h = ''
  for l in systemlist('aiksaurus ' .. shellescape(a:base))
    if l[:3] == '=== '
      let h = '(' .. substitute(l[4:], ' =*$', ')', '')
    elseif l ==# 'Alphabetically similar known words are: '
      let h = "\U0001f52e"
    elseif l[0] =~ '\a' || (h ==# "\U0001f52e" && l[0] ==# "\t")
      call extend(res, map(split(substitute(l, '^\t', '', ''), ', '), {_, val -> {'word': val, 'menu': h}}))
    endif
  endfor
  return res
endfunc
if exists('+thesaurusfunc')
  set thesaurusfunc=Thesaur
endif
Completing keywords in the current and included files compl-keyword
The 'include' option is used to specify a line that contains an include file name. The 'path' option is used to search for include files.
i_CTRL-X_CTRL-I CTRL-X CTRL-I Search for the first keyword in the current and included files that starts with the same characters as those before the cursor. The matched keyword is inserted in front of the cursor.
CTRL-N Search forwards for next matching keyword. This keyword replaces the previous matching keyword. Note: CTRL-I is the same as <Tab>, which is likely to be typed after a successful completion, therefore CTRL-I is not used for searching for the next match.
CTRL-P Search backward for previous matching keyword. This keyword replaces the previous matching keyword.
CTRL-X CTRL-I Further use of CTRL-X CTRL-I will copy the words following the previous expansion in other contexts unless a double CTRL-X is used.
Completing tags compl-tag i_CTRL-X_CTRL-] CTRL-X CTRL-] Search for the first tag that starts with the same characters as before the cursor. The matching tag is inserted in front of the cursor. Alphabetic characters and characters in 'iskeyword' are used to decide which characters are included in the tag name (same as for a keyword). See also CTRL-]. The 'showfulltag' option can be used to add context from around the tag definition. CTRL-] or CTRL-N Search forwards for next matching tag. This tag replaces the previous matching tag.
CTRL-P Search backward for previous matching tag. This tag replaces the previous matching tag.
Completing file names compl-filename i_CTRL-X_CTRL-F CTRL-X CTRL-F Search for the first file name that starts with the same characters as before the cursor. The matching file name is inserted in front of the cursor. Alphabetic characters and characters in 'isfname' are used to decide which characters are included in the file name.Note: the 'path' option is not used here (yet). CTRL-F or CTRL-N Search forwards for next matching file name. This file name replaces the previous matching file name.
CTRL-P Search backward for previous matching file name. This file name replaces the previous matching file name.
Completing definitions or macros compl-define
The 'define' option is used to specify a line that contains a definition. The 'include' option is used to specify a line that contains an include file name. The 'path' option is used to search for include files.
i_CTRL-X_CTRL-D CTRL-X CTRL-D Search in the current and included files for the first definition (or macro) name that starts with the same characters as before the cursor. The found definition name is inserted in front of the cursor. CTRL-D or CTRL-N Search forwards for next matching macro name. This macro name replaces the previous matching macro name.
CTRL-P Search backward for previous matching macro name. This macro name replaces the previous matching macro name.
CTRL-X CTRL-D Further use of CTRL-X CTRL-D will copy the words following the previous expansion in other contexts unless a double CTRL-X is used.
Completing Vim commands compl-vim
Completion is context-sensitive. It works like on the Command-line. It completes an Ex command as well as its arguments. This is useful when writing a Vim script.
i_CTRL-X_CTRL-V CTRL-X CTRL-V Guess what kind of item is in front of the cursor and find the first match for it. Note: When CTRL-V is mapped you can often use CTRL-Q instead of i_CTRL-Q. CTRL-V or CTRL-N Search forwards for next match. This match replaces the previous one.
CTRL-P Search backwards for previous match. This match replaces the previous one.
CTRL-X CTRL-V Further use of CTRL-X CTRL-V will do the same as CTRL-V. This allows mapping a key to do Vim command completion, for example:
:imap <Tab> <C-X><C-V>
User defined completion compl-function
Completion is done by a function that can be defined by the user with the 'completefunc' option. See below for how the function is called and an example complete-functions.
i_CTRL-X_CTRL-U CTRL-X CTRL-U Guess what kind of item is in front of the cursor and find the first match for it. CTRL-U or CTRL-N Use the next match. This match replaces the previous one.
CTRL-P Use the previous match. This match replaces the previous one.
Omni completion compl-omni
Completion is done by a function that can be defined by the user with the 'omnifunc' option. This is to be used for filetype-specific completion.
See below for how the function is called and an example complete-functions. For remarks about specific filetypes see compl-omni-filetypes. More completion scripts will appear, check www.vim.org. Currently there is a first version for C++.
i_CTRL-X_CTRL-O CTRL-X CTRL-O Guess what kind of item is in front of the cursor and find the first match for it. CTRL-O or CTRL-N Use the next match. This match replaces the previous one.
CTRL-P Use the previous match. This match replaces the previous one.
Spelling suggestions compl-spelling
A word before or at the cursor is located and correctly spelled words are suggested to replace it. If there is a badly spelled word in the line, before or under the cursor, the cursor is moved to after it. Otherwise the word just before the cursor is used for suggestions, even though it isn't badly spelled.
NOTE: CTRL-S suspends display in many Unix terminals. Use 's' instead. Type CTRL-Q to resume displaying.
i_CTRL-X_CTRL-S i_CTRL-X_s CTRL-X CTRL-S or CTRL-X s Locate the word in front of the cursor and find the first spell suggestion for it. CTRL-S or CTRL-N Use the next suggestion. This replaces the previous one. Note that you can't use 's' here.
CTRL-P Use the previous suggestion. This replaces the previous one.
Completing keywords from different sources compl-generic
i_CTRL-N CTRL-N Find next match for words that start with the keyword in front of the cursor, looking in places specified with the 'complete' option. The found keyword is inserted in front of the cursor.
i_CTRL-P CTRL-P Find previous match for words that start with the keyword in front of the cursor, looking in places specified with the 'complete' option. The found keyword is inserted in front of the cursor.
CTRL-N Search forward for next matching keyword. This keyword replaces the previous matching keyword.
CTRL-P Search backwards for next matching keyword. This keyword replaces the previous matching keyword.
CTRL-X CTRL-N or CTRL-X CTRL-P Further use of CTRL-X CTRL-N or CTRL-X CTRL-P will copy the words following the previous expansion in other contexts unless a double CTRL-X is used.
Stop completion compl-stop
i_CTRL-X_CTRL-Z CTRL-X CTRL-Z Stop completion without changing the text.

AUTO-COMPLETION compl-autocomplete

To get basic "autocompletion" without installing a plugin, try this script:
local triggers = {"."}
vim.api.nvim_create_autocmd("InsertCharPre", {
  buffer = vim.api.nvim_get_current_buf(),
  callback = function()
    if vim.fn.pumvisible() == 1 or vim.fn.state("m") == "m" then
      return
    end
    local char = vim.v.char
    if vim.list_contains(triggers, char) then
      local key = vim.keycode("<C-x><C-n>")
      vim.api.nvim_feedkeys(key, "m", false)
    end
  end
})

FUNCTIONS FOR FINDING COMPLETIONS complete-functions

The function is called in two different ways:
First the function is called to find the start of the text to be completed.
Later the function is called to actually find the matches.
On the first invocation the arguments are: a:findstart 1 a:base empty
The function must return the column where the completion starts. It must be a number between zero and the cursor column "col('.')". This involves looking at the characters just before the cursor and including those characters that could be part of the completed item. The text between this column and the cursor column will be replaced with the matches. If the returned value is larger than the cursor column, the cursor column is used.
Negative return values: -2 To cancel silently and stay in completion mode. -3 To cancel silently and leave completion mode. Another negative value: completion starts at the cursor column
On the second invocation the arguments are: a:findstart 0 a:base the text with which matches should match; the text that was located in the first call (can be empty)
The function must return a List with the matching words. These matches usually include the "a:base" text. When there are no matches return an empty List. Note that the cursor may have moved since the first invocation, the text may have been changed.
In order to return more information than the matching words, return a Dict that contains the List. The Dict can have these items: words The List of matching words (mandatory). refresh A string to control re-invocation of the function (optional). The only value currently recognized is "always", the effect is that the function is called whenever the leading text is changed. Other items are ignored.
For acting upon end of completion, see the CompleteDonePre and CompleteDone autocommand event.
For example, the function can contain this:
let matches = ... list of words ...
return {'words': matches, 'refresh': 'always'}
complete-items Each list item can either be a string or a Dictionary. When it is a string it is used as the completion. When it is a Dictionary it can contain these items: word the text that will be inserted, mandatory abbr abbreviation of "word"; when not empty it is used in the menu instead of "word" menu extra text for the popup menu, displayed after "word" or "abbr" info more information about the item, can be displayed in a preview window kind single letter indicating the type of completion icase when non-zero case is to be ignored when comparing items to be equal; when omitted zero is used, thus items that only differ in case are added equal when non-zero, always treat this item to be equal when comparing. Which means, "equal=1" disables filtering of this item. dup when non-zero this match will be added even when an item with the same word is already present. empty when non-zero this match will be added even when it is an empty string user_data custom data which is associated with the item and available in v:completed_item; it can be any type; defaults to an empty string
All of these except "icase", "equal", "dup" and "empty" must be a string. If an item does not meet these requirements then an error message is given and further items in the list are not used. You can mix string and Dictionary items in the returned list.
The "menu" item is used in the popup menu and may be truncated, thus it should be relatively short. The "info" item can be longer, it will be displayed in the preview window when "preview" appears in 'completeopt'. The "info" item will also remain displayed after the popup menu has been removed. This is useful for function arguments. Use a single space for "info" to remove existing text in the preview window. The size of the preview window is three lines, but 'previewheight' is used when it has a value of 1 or 2.
The "kind" item uses a single letter to indicate the kind of completion. This may be used to show the completion differently (different color or icon). Currently these types can be used: v variable f function or method m member of a struct or class t typedef d #define or macro
When searching for matches takes some time call complete_add() to add each match to the total list. These matches should then not appear in the returned list! Call complete_check() now and then to allow the user to press a key while still searching for matches. Stop searching when it returns non-zero.
E840 The function is allowed to move the cursor, it is restored afterwards. The function is not allowed to move to another window or delete text.
An example that completes the names of the months:
fun! CompleteMonths(findstart, base)
  if a:findstart
    " locate the start of the word
    let line = getline('.')
    let start = col('.') - 1
    while start > 0 && line[start - 1] =~ '\a'
      let start -= 1
    endwhile
    return start
  else
    " find months matching with "a:base"
    let res = []
    for m in split("Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec")
      if m =~ '^' .. a:base
        call add(res, m)
      endif
    endfor
    return res
  endif
endfun
set completefunc=CompleteMonths
The same, but now pretending searching for matches is slow:
fun! CompleteMonths(findstart, base)
  if a:findstart
    " locate the start of the word
    let line = getline('.')
    let start = col('.') - 1
    while start > 0 && line[start - 1] =~ '\a'
      let start -= 1
    endwhile
    return start
  else
    " find months matching with "a:base"
    for m in split("Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec")
      if m =~ '^' .. a:base
        call complete_add(m)
      endif
      sleep 300m        " simulate searching for next match
      if complete_check()
        break
      endif
    endfor
    return []
  endif
endfun
set completefunc=CompleteMonths

INSERT COMPLETION POPUP MENU ins-completion-menu

popupmenu-completion Vim can display the matches in a simplistic popup menu.
The menu is used when:
The 'completeopt' option contains "menu" or "menuone".
The terminal supports at least 8 colors.
There are at least two matches. One if "menuone" is used.
The 'pumheight' option can be used to set a maximum height. The default is to use all space available. The 'pumwidth' option can be used to set a minimum width. The default is 15 characters.
There are three states: 1. A complete match has been inserted, e.g., after using CTRL-N or CTRL-P. 2. A cursor key has been used to select another match. The match was not inserted then, only the entry in the popup menu is highlighted. 3. Only part of a match has been inserted and characters were typed or the backspace key was used. The list of matches was then adjusted for what is in front of the cursor.
You normally start in the first state, with the first match being inserted. When "longest" is in 'completeopt' and there is more than one match you start in the third state.
If you select another match, e.g., with CTRL-N or CTRL-P, you go to the first state. This doesn't change the list of matches.
When you are back at the original text then you are in the third state. To get there right away you can use a mapping that uses CTRL-P right after starting the completion:
:imap <F7> <C-N><C-P>
popupmenu-keys In the first state these keys have a special meaning: <BS> and CTRL-H Delete one character, find the matches for the word before the cursor. This reduces the list of matches, often to one entry, and switches to the second state. Any non-special character: Stop completion without changing the match and insert the typed character.
In the second and third state these keys have a special meaning: <BS> and CTRL-H Delete one character, find the matches for the shorter word before the cursor. This may find more matches. CTRL-L Add one character from the current match, may reduce the number of matches. any printable, non-white character: Add this character and reduce the number of matches.
In all three states these can be used: CTRL-Y Yes: Accept the currently selected match and stop completion. CTRL-E End completion, go back to what was there before selecting a match (what was typed or longest common string). <PageUp> Select a match several entries back, but don't insert it. <PageDown> Select a match several entries further, but don't insert it. <Up> Select the previous match, as if CTRL-P was used, but don't insert it. <Down> Select the next match, as if CTRL-N was used, but don't insert it. <Space> or <Tab> Stop completion without changing the match and insert the typed character.
The behavior of the <Enter> key depends on the state you are in: first state: Use the text as it is and insert a line break. second state: Insert the currently selected match. third state: Use the text as it is and insert a line break.
In other words: If you used the cursor keys to select another entry in the list of matches then the <Enter> key inserts that match. If you typed something else then <Enter> inserts a line break.
The colors of the menu can be changed with these highlight groups: Pmenu normal item hl-Pmenu PmenuSel selected item hl-PmenuSel PmenuSbar scrollbar hl-PmenuSbar PmenuThumb thumb of the scrollbar hl-PmenuThumb
There are no special mappings for when the popup menu is visible. However, you can use an Insert mode mapping that checks the pumvisible() function to do something different. Example:
:inoremap <Down> <C-R>=pumvisible() ? "\<lt>C-N>" : "\<lt>Down>"<CR>
You can use of <expr> in mapping to have the popup menu used when typing a character and some condition is met. For example, for typing a dot:
inoremap <expr> . MayComplete()
func MayComplete()
    if (can complete)
      return ".\<C-X>\<C-O>"
    endif
    return '.'
endfunc
See :map-<expr> for more info.

FILETYPE-SPECIFIC REMARKS FOR OMNI COMPLETION compl-omni-filetypes

The file used for {filetype} should be autoload/{filetype}complete.vim in 'runtimepath'. Thus for "java" it is autoload/javacomplete.vim.
Completion of C code requires a tags file. You should use Universal/ Exuberant ctags, because it adds extra information that is needed for completion. You can find it here: Universal Ctags: https://ctags.io
Universal Ctags is preferred, Exuberant Ctags is no longer maintained.
If you want to complete system functions you can do something like this. Use ctags to generate a tags file for all the system header files:
% ctags -R -f ~/.config/nvim/systags /usr/include /usr/local/include
In your vimrc file add this tags file to the 'tags' option:
set tags+=~/.config/nvim/systags
When using CTRL-X CTRL-O after a name without any "." or "->" it is completed from the tags file directly. This works for any identifier, also function names. If you want to complete a local variable name, which does not appear in the tags file, use CTRL-P instead.
When using CTRL-X CTRL-O after something that has "." or "->" Vim will attempt to recognize the type of the variable and figure out what members it has. This means only members valid for the variable will be listed.
When a member name already was complete, CTRL-X CTRL-O will add a "." or "->" for composite types.
Vim doesn't include a C compiler, only the most obviously formatted declarations are recognized. Preprocessor stuff may cause confusion. When the same structure name appears in multiple places all possible members are included.
Complete properties and their appropriate values according to CSS 2.1 specification.
CTRL-X CTRL-O provides completion of various elements of (X)HTML files. It is designed to support writing of XHTML 1.0 Strict files but will also work for other versions of HTML. Features:
after "<" complete tag name depending on context (no div suggestion inside of an a tag); '/>' indicates empty tags
inside of tag complete proper attributes (no width attribute for an a tag); show also type of attribute; "*" indicates required attributes
when attribute has limited number of possible values help to complete them
complete names of entities
complete values of "class" and "id" attributes with data obtained from <style> tag and included CSS files
when completing value of "style" attribute or working inside of "style" tag switch to ft-css-omni completion
when completing values of events attributes or working inside of "script" tag switch to ft-javascript-omni completion
when used after "</" CTRL-X CTRL-O will close the last opened tag
Note: When used first time completion menu will be shown with little delay
this is time needed for loading of data file. Note: Completion may fail in badly formatted documents. In such case try to run :make command to detect formatting problems.
HTML flavor html-flavor
The default HTML completion depends on the filetype. For HTML files it is HTML 4.01 Transitional ('filetype' is "html"), for XHTML it is XHTML 1.0 Strict ('filetype' is "xhtml").
When doing completion outside of any other tag you will have possibility to choose DOCTYPE and the appropriate data file will be loaded and used for all next completions.
More about format of data file in xml-omni-datafile. Some of the data files may be found on the Vim website (www).
Note that b:html_omni_flavor may point to a file with any XML data. This makes possible to mix PHP (ft-php-omni) completion with any XML dialect (assuming you have data file for it). Without setting that variable XHTML 1.0 Strict will be used.
Completion of most elements of JavaScript language and DOM elements.
Complete:
variables
function name; show function arguments
function arguments
properties of variables trying to detect type of variable
complete DOM objects and properties depending on context
keywords of language
Completion works in separate JavaScript files (&ft==javascript), inside of <script> tag of (X)HTML and in values of event attributes (including scanning of external files).
DOM compatibility
At the moment (beginning of 2006) there are two main browsers - MS Internet Explorer and Mozilla Firefox. These two applications are covering over 90% of market. Theoretically standards are created by W3C organisation (https://www.w3.org/) but they are not always followed/implemented.
IE        FF        W3C  Omni completion ~
+/-        +/-        +    +                     ~
+        +        -    +                     ~
+        -        -    -                     ~
-        +        -    -                     ~
Regardless from state of implementation in browsers but if element is defined in standards, completion plugin will place element in suggestion list. When both major engines implemented element, even if this is not in standards it will be suggested. All other elements are not placed in suggestion list.
Completion of PHP code requires a tags file for completion of data from external files and for class aware completion. You should use Universal/ Exuberant ctags version 5.5.4 or newer. You can find it here:
Universal Ctags: https://ctags.io
Script completes:
after $ variables name
if variable was declared as object add "->", if tags file is available show name of class
after "->" complete only function and variable names specific for given class. To find class location and contents tags file is required. Because PHP isn't strongly typed language user can use @var tag to declare class:
/* @var $myVar myClass */
$myVar->
Still, to find myClass contents tags file is required.
function names with additional info:
in case of built-in functions list of possible arguments and after | type data returned by function
in case of user function arguments and name of file where function was defined (if it is not current file)
constants names
class names after "new" declaration
Note: when doing completion first time Vim will load all necessary data into memory. It may take several seconds. After next use of completion delay should not be noticeable.
Script detects if cursor is inside <?php ?> tags. If it is outside it will automatically switch to HTML/CSS/JavaScript completion.Note: contrary to original HTML files completion of tags (and only tags) isn't context aware.
NOTE: compl-omni for Ruby code requires provider-ruby to be installed.
Ruby completion will parse your buffer on demand in order to provide a list of completions. These completions will be drawn from modules loaded by "require" and modules defined in the current buffer.
The completions provided by CTRL-X CTRL-O are sensitive to the context:
CONTEXT COMPLETIONS PROVIDED
1. Not inside a class definition Classes, constants and globals
2. Inside a class definition Methods or constants defined in the class
3. After '.', '::' or ':' Methods applicable to the object being dereferenced
4. After ':' or ':foo' Symbol name (beginning with "foo")
Notes:
Vim will load/evaluate code in order to provide completions. This may cause some code execution, which may be a concern. This is no longer enabled by default, to enable this feature add
let g:rubycomplete_buffer_loading = 1
<- In context 1 above, Vim can parse the entire buffer to add a list of classes to the completion results. This feature is turned off by default, to enable it add
let g:rubycomplete_classes_in_global = 1
to your vimrc
In context 2 above, anonymous classes are not supported.
In context 3 above, Vim will attempt to determine the methods supported by the object.
Vim can detect and load the Rails environment for files within a rails project. The feature is disabled by default, to enable it add
let g:rubycomplete_rails = 1
to your vimrc
Vim has the ability to color syntax highlight nearly 500 languages. Part of this highlighting includes knowing what keywords are part of a language. Many filetypes already have custom completion scripts written for them, the syntaxcomplete plugin provides basic completion for all other filetypes. It does this by populating the omni completion list with the text Vim already knows how to color highlight. It can be used for any filetype and provides a minimal language-sensitive completion.
To enable syntax code completion you can run:
setlocal omnifunc=syntaxcomplete#Complete
You can automate this by placing the following in your init.vim (after any ":filetype" command):
if has("autocmd") && exists("+omnifunc")
    autocmd Filetype *
                \        if &omnifunc == "" |
                \                setlocal omnifunc=syntaxcomplete#Complete |
                \        endif
endif
The above will set completion to this script only if a specific plugin does not already exist for that filetype.
Each filetype can have a wide range of syntax items. The plugin allows you to customize which syntax groups to include or exclude from the list. Let's have a look at the PHP filetype to see how this works.
If you edit a file called, index.php, run the following command:
syntax list
The first thing you will notice is that there are many different syntax groups. The PHP language can include elements from different languages like HTML, JavaScript and many more. The syntax plugin will only include syntax groups that begin with the filetype, "php", in this case. For example these syntax groups are included by default with the PHP: phpEnvVar, phpIntVar, phpFunctions.
If you wish non-filetype syntax items to also be included, you can use a regular expression syntax (added in version 13.0 of autoload/syntaxcomplete.vim) to add items. Looking at the output from ":syntax list" while editing a PHP file I can see some of these entries:
htmlArg,htmlTag,htmlTagName,javaScriptStatement,javaScriptGlobalObjects
To pick up any JavaScript and HTML keyword syntax groups while editing a PHP file, you can use 3 different regexs, one for each language. Or you can simply restrict the include groups to a particular value, without using a regex string:
let g:omni_syntax_group_include_php = 'php\w\+,javaScript\w\+,html\w\+'
let g:omni_syntax_group_include_php = 'phpFunctions,phpMethods'
The basic form of this variable is:
let g:omni_syntax_group_include_{filetype} = 'regex,comma,separated'
The PHP language has an enormous number of items which it knows how to syntax highlight. These items will be available within the omni completion list.
Some people may find this list unwieldy or are only interested in certain items. There are two ways to prune this list (if necessary). If you find certain syntax groups you do not wish displayed you can use two different methods to identify these groups. The first specifically lists the syntax groups by name. The second uses a regular expression to identify both syntax groups. Simply add one the following to your vimrc:
let g:omni_syntax_group_exclude_php = 'phpCoreConstant,phpConstant'
let g:omni_syntax_group_exclude_php = 'php\w*Constant'
Add as many syntax groups to this list by comma separating them. The basic form of this variable is:
let g:omni_syntax_group_exclude_{filetype} = 'regex,comma,separated'
You can create as many of these variables as you need, varying only the filetype at the end of the variable name.
The plugin uses the isKeyword option to determine where word boundaries are for the syntax items. For example, in the Scheme language completion should include the "-", call-with-output-file. Depending on your filetype, this may not provide the words you are expecting. Setting the g:omni_syntax_use_iskeyword option to 0 will force the syntax plugin to break on word characters. This can be controlled adding the following to your vimrc:
let g:omni_syntax_use_iskeyword = 0
For plugin developers, the plugin exposes a public function OmniSyntaxList. This function can be used to request a List of syntax items. When editing a SQL file (:e syntax.sql) you can use the ":syntax list" command to see the various groups and syntax items. For example:
syntax list
Yields data similar to this:
sqlOperator xxx some prior all like and any escape exists in is not
or intersect minus between distinct
links to Operator
sqlType xxx varbit varchar nvarchar bigint int uniqueidentifier
date money long tinyint unsigned xml text smalldate
double datetime nchar smallint numeric time bit char
varbinary binary smallmoney
image float integer timestamp real decimal
There are two syntax groups listed here: sqlOperator and sqlType. To retrieve a List of syntax items you can call OmniSyntaxList a number of different ways. To retrieve all syntax items regardless of syntax group:
echo OmniSyntaxList( [] )
To retrieve only the syntax items for the sqlOperator syntax group:
echo OmniSyntaxList( ['sqlOperator'] )
To retrieve all syntax items for both the sqlOperator and sqlType groups:
echo OmniSyntaxList( ['sqlOperator', 'sqlType'] )
A regular expression can also be used:
echo OmniSyntaxList( ['sql\w\+'] )
From within a plugin, you would typically assign the output to a List:
let myKeywords = []
let myKeywords = OmniSyntaxList( ['sqlKeyword'] )

SQL ft-sql-omni

Completion for the SQL language includes statements, functions, keywords. It will also dynamically complete tables, procedures, views and column lists with data pulled directly from within a database. For detailed instructions and a tutorial see omni-sql-completion.
The SQL completion plugin can be used in conjunction with other completion plugins. For example, the PHP filetype has its own completion plugin. Since PHP is often used to generate dynamic website by accessing a database, the SQL completion plugin can also be enabled. This allows you to complete PHP code and SQL code at the same time.
Vim 7 provides a mechanism for context aware completion of XML files. It depends on a special xml-omni-datafile and two commands: :XMLns and :XMLent. Features are:
after "<" complete the tag name, depending on context
inside of a tag complete proper attributes
when an attribute has a limited number of possible values help to complete them
complete names of entities (defined in xml-omni-datafile and in the current file with "<!ENTITY" declarations)
when used after "</" CTRL-X CTRL-O will close the last opened tag
Format of XML data file xml-omni-datafile
XML data files are stored in the "autoload/xml" directory in 'runtimepath'. Vim distribution provides examples of data files in the "$VIMRUNTIME/autoload/xml" directory. They have a meaningful name which will be used in commands. It should be a unique name which will not create conflicts. For example, the name xhtml10s.vim means it is the data file for XHTML 1.0 Strict.
Each file contains a variable with a name like g:xmldata_xhtml10s . It is a compound from two parts:
1. "g:xmldata_" general prefix, constant for all data files 2. "xhtml10s" the name of the file and the name of the described XML dialect; it will be used as an argument for the :XMLns command
Part two must be exactly the same as name of file.
The variable is a Dictionary. Keys are tag names and each value is a two element List. The first element of the List is also a List with the names of possible children. The second element is a Dictionary with the names of attributes as keys and the possible values of attributes as values. Example:
let g:xmldata_crippled = {
\ "vimxmlentities": ["amp", "lt", "gt", "apos", "quot"],
\ 'vimxmlroot': ['tag1'],
\ 'tag1':
\ [ ['childoftag1a', 'childoftag1b'], {'attroftag1a': [],
\ 'attroftag1b': ['valueofattr1', 'valueofattr2']}],
\ 'childoftag1a':
\ [ [], {'attrofchild': ['attrofchild']}],
\ 'childoftag1b':
\ [ ['childoftag1a'], {'attrofchild': []}],
\ "vimxmltaginfo": {
\ 'tag1': ['Menu info', 'Long information visible in preview window']},
\ 'vimxmlattrinfo': {
\ 'attrofchild': ['Menu info', 'Long information visible in preview window']}}
This example would be put in the "autoload/xml/crippled.vim" file and could help to write this file:
<tag1 attroftag1b="valueofattr1">
    <childoftag1a attrofchild>
            &amp; &lt;
    </childoftag1a>
    <childoftag1b attrofchild="5">
        <childoftag1a>
            &gt; &apos; &quot;
        </childoftag1a>
    </childoftag1b>
</tag1>
In the example four special elements are visible:
1. "vimxmlentities" - a special key with List containing entities of this XML dialect. 2. If the list containing possible values of attributes has one element and this element is equal to the name of the attribute this attribute will be treated as boolean and inserted as "attrname" and not as 'attrname="' 3. "vimxmltaginfo" - a special key with a Dictionary containing tag names as keys and two element List as values, for additional menu info and the long description. 4. "vimxmlattrinfo" - special key with Dictionary containing attribute names as keys and two element List as values, for additional menu info and long description.
Note: Tag names in the data file MUST not contain a namespace description. Check xsl.vim for an example. Note: All data and functions are publicly available as global variables/functions and can be used for personal editing functions.
DTD -> Vim dtd2vim
On www is the script dtd2vim which parses DTD and creates an XML data file for Vim XML omni completion.
Check the beginning of that file for usage details. The script requires perl and:
Commands
:XMLns {name} [{namespace}] :XMLns
Vim has to know which data file should be used and with which namespace. For loading of the data file and connecting data with the proper namespace use :XMLns command. The first (obligatory) argument is the name of the data (xhtml10s, xsl). The second argument is the code of namespace (h, xsl). When used without a second argument the dialect will be used as default - without namespace declaration. For example to use XML completion in .xsl files:
:XMLns xhtml10s
:XMLns xsl xsl
:XMLent {name} :XMLent
By default entities will be completed from the data file of the default namespace. The XMLent command should be used in case when there is no default namespace:
:XMLent xhtml10s
Usage
While used in this situation (after declarations from previous part, | is cursor position):
<|
Will complete to an appropriate XHTML tag, and in this situation:
<xsl:|
Will complete to an appropriate XSL tag.
The script xmlcomplete.vim, provided through the autoload mechanism, has the xmlcomplete#GetLastOpenTag() function which can be used in XML files to get the name of the last open tag (b:unaryTagsStack has to be defined):
:echo xmlcomplete#GetLastOpenTag("b:unaryTagsStack")

8. Insert mode commands inserting

The following commands can be used to insert new text into the buffer. They can all be undone and repeated with the "." command.
a a Append text after the cursor [count] times. If the cursor is in the first column of an empty line Insert starts there. But not when 'virtualedit' is set!
A A Append text at the end of the line [count] times. For using "A" in Visual block mode see v_b_A.
<insert> or i insert <Insert> i Insert text before the cursor [count] times. When using CTRL-O in Insert mode i_CTRL-O the count is not supported.
I I Insert text before the first non-blank in the line [count] times. When the 'H' flag is present in 'cpoptions' and the line only contains blanks, insert start just before the last blank. For using "I" in Visual block mode see v_b_I.
gI gI Insert text in column 1 [count] times.
gi gi Insert text in the same position as where Insert mode was stopped last time in the current buffer. This uses the '^ mark. It's different from "`^i" when the mark is past the end of the line. The position is corrected for inserted/deleted lines, but NOT for inserted/deleted characters. When the :keepjumps command modifier is used the '^ mark won't be changed.
o o Begin a new line below the cursor and insert text, repeat [count] times.
O O Begin a new line above the cursor and insert text, repeat [count] times.
These commands are used to start inserting text. You can end insert mode with <Esc>. See mode-ins-repl for the other special characters in Insert mode. The effect of [count] takes place after Insert mode is exited.
When 'autoindent' is on, the indent for a new line is obtained from the previous line. When 'smartindent' or 'cindent' is on, the indent for a line is automatically adjusted for C programs.
'formatoptions' can be set to copy the comment leader when opening a new line.
'textwidth' can be set to the maximum width for a line. When a line becomes too long when appending characters a line break is automatically inserted.

9. Ex insert commands inserting-ex

:a :append :{range}a[ppend][!] Insert several lines of text below the specified line. If the {range} is missing, the text will be inserted after the current line. Adding [!] toggles 'autoindent' for the time this command is executed.
:i :in :insert :{range}i[nsert][!] Insert several lines of text above the specified line. If the {range} is missing, the text will be inserted before the current line. Adding [!] toggles 'autoindent' for the time this command is executed.
These two commands will keep on asking for lines, until you type a line containing only a ".". Watch out for lines starting with a backslash, see line-continuation.
When in Ex mode (see -e) a backslash at the end of the line can be used to insert a NUL character. To be able to have a line ending in a backslash use two backslashes. This means that the number of backslashes is halved, but only at the end of the line.
NOTE: These commands cannot be used with :global or :vglobal. ":append" and ":insert" don't work properly in between ":if" and ":endif", ":for" and ":endfor", ":while" and ":endwhile".
:start :startinsert :star[tinsert][!] Start Insert mode (or Terminal-mode in a terminal buffer) just after executing this command. Works like typing "i" in Normal mode. When the ! is included it works like "A", append to the line. Otherwise insertion starts at the cursor position. Note that when using this command in a function or script, the insertion only starts after the function or script is finished. This command does not work from :normal.
:stopi :stopinsert :stopi[nsert] Stop Insert mode or Terminal-mode as soon as possible. Works like typing <Esc> in Insert mode. Can be used in an autocommand, example:
:au BufEnter scratch stopinsert
replacing-ex :startreplace :startr[eplace][!] Start Replace mode just after executing this command. Works just like typing "R" in Normal mode. When the ! is included it acts just like "$R" had been typed (ie. begin replace mode at the end-of-line). Other- wise replacement begins at the cursor position. Note that when using this command in a function or script that the replacement will only start after the function or script is finished.
:startgreplace :startg[replace][!] Just like :startreplace, but use Virtual Replace mode, like with gR.

10. Inserting a file inserting-file

:r :re :read :r[ead] [++opt] [name] Insert the file [name] (default: current file) below the cursor. See ++opt for the possible values of [++opt].
:{range}r[ead] [++opt] [name] Insert the file [name] (default: current file) below the specified line. See ++opt for the possible values of [++opt].
:r! :read! :[range]r[ead] [++opt] !{cmd} Execute {cmd} and insert its standard output below the cursor or the specified line. A temporary file is used to store the output of the command which is then read into the buffer. 'shellredir' is used to save the output of the command, which can be set to include stderr or not. {cmd} is executed like with ":!{cmd}", any '!' is replaced with the previous command :!. See ++opt for the possible values of [++opt].
These commands insert the contents of a file, or the output of a command, into the buffer. They can be undone. They cannot be repeated with the "." command. They work on a line basis, insertion starts below the line in which the cursor is, or below the specified line. To insert text above the first line use the command ":0r {name}".
After the ":read" command, the cursor is left on the first non-blank in the first new line. Unless in Ex mode, then the cursor is left on the last new line (sorry, this is Vi compatible).
If a file name is given with ":r", it becomes the alternate file. This can be used, for example, when you want to edit that file instead: ":e! #". This can be switched off by removing the 'a' flag from the 'cpoptions' option.
Of the [++opt] arguments one is specifically for ":read", the ++edit argument. This is useful when the ":read" command is actually used to read a file into the buffer as if editing that file. Use this command in an empty buffer:
:read ++edit filename
The effect is that the 'fileformat', 'fileencoding', 'bomb', etc. options are set to what has been detected for "filename". Note that a single empty line remains, you may want to delete it.
file-read The 'fileformat' option sets the <EOL> style for a file:
'fileformat' characters name
"dos" <CR><NL> or <NL> DOS format "unix" <NL> Unix format "mac" <CR> Mac format
If 'fileformat' is "dos", a <CR> in front of an <NL> is ignored and a CTRL-Z at the end of the file is ignored.
If 'fileformat' is "mac", a <NL> in the file is internally represented by a <CR>. This is to avoid confusion with a <NL> which is used to represent a <NUL>. See CR-used-for-NL.
If the 'fileformats' option is not empty Vim tries to recognize the type of <EOL> (see file-formats). However, the 'fileformat' option will not be changed, the detected format is only used while reading the file. A similar thing happens with 'fileencodings'.
On non-Win32 systems the message "[dos format]" is shown if a file is read in DOS format, to remind you that something unusual is done. On Macintosh and Win32 the message "[unix format]" is shown if a file is read in Unix format. On non-Macintosh systems, the message "[mac format]" is shown if a file is read in Mac format.
An example on how to use ":r !":
:r !uuencode binfile binfile
This command reads "binfile", uuencodes it and reads it into the current buffer. Useful when you are editing e-mail and want to include a binary file.
read-messages When reading a file Vim will display a message with information about the read file. In the table is an explanation for some of the items. The others are self explanatory. Using the long or the short version depends on the 'shortmess' option.
long short meaning
[readonly] {RO} the file is write protected [fifo/socket] using a stream [fifo] using a fifo stream [socket] using a socket stream [CR missing] reading with "dos" 'fileformat' and a NL without a preceding CR was found. [NL found] reading with "mac" 'fileformat' and a NL was found (could be "unix" format) [long lines split] at least one line was split in two [NOT converted] conversion from 'fileencoding' to 'encoding' was desired but not possible [converted] conversion from 'fileencoding' to 'encoding' done [READ ERRORS] not all of the file could be read
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