Return the currently active minibuffer window, or nil if none.

Search for partial matches to STRING in COLLECTION.
Test each of the possible completions specified by COLLECTION
to see if it begins with STRING.  The possible completions may be
strings or symbols.  Symbols are converted to strings before testing,
see `symbol-name'.
The value is a list of all the possible completions that match STRING.

If COLLECTION is an alist, the keys (cars of elements) are the
possible completions.  If an element is not a cons cell, then the
element itself is the possible completion.
If COLLECTION is a hash-table, all the keys that are strings or symbols
are the possible completions.
If COLLECTION is an obarray, the names of all symbols in the obarray
are the possible completions.

COLLECTION can also be a function to do the completion itself.
It receives three arguments: the values STRING, PREDICATE and t.
Whatever it returns becomes the value of `all-completions'.

If optional third argument PREDICATE is non-nil,
it is used to test each possible match.
The match is a candidate only if PREDICATE returns non-nil.
The argument given to PREDICATE is the alist element
or the symbol from the obarray.  If COLLECTION is a hash-table,
predicate is called with two arguments: the key and the value.
Additionally to this predicate, `completion-regexp-list'
is used to further constrain the set of candidates.

An obsolete optional fourth argument HIDE-SPACES is still accepted for
backward compatibility.  If non-nil, strings in COLLECTION that start
with a space are ignored unless STRING itself starts with a space.

Like `assoc' but specifically for strings (and symbols).

This returns the first element of LIST whose car matches the string or
symbol KEY, or nil if no match exists.  When performing the
comparison, symbols are first converted to strings, and unibyte
strings to multibyte.  If the optional arg CASE-FOLD is non-nil, case
is ignored.

Unlike `assoc', KEY can also match an entry in LIST consisting of a
single string, rather than a cons cell whose car is a string.

Read a string in the minibuffer, with completion.
PROMPT is a string to prompt with; normally it ends in a colon and a space.
COLLECTION can be a list of strings, an alist, an obarray or a hash table.
COLLECTION can also be a function to do the completion itself.
PREDICATE limits completion to a subset of COLLECTION.
See `try-completion' and `all-completions' for more details
 on completion, COLLECTION, and PREDICATE.

REQUIRE-MATCH can take the following values:
- t means that the user is not allowed to exit unless
  the input is (or completes to) an element of COLLECTION or is null.
- nil means that the user can exit with any input.
- `confirm' means that the user can exit with any input, but she needs
  to confirm her choice if the input is not an element of COLLECTION.
- `confirm-after-completion' means that the user can exit with any
  input, but she needs to confirm her choice if she called
  `minibuffer-complete' right before `minibuffer-complete-and-exit'
  and the input is not an element of COLLECTION.
- anything else behaves like t except that typing RET does not exit if it
  does non-null completion.

If the input is null, `completing-read' returns DEF, or the first element
of the list of default values, or an empty string if DEF is nil,
regardless of the value of REQUIRE-MATCH.

If INITIAL-INPUT is non-nil, insert it in the minibuffer initially,
  with point positioned at the end.
  If it is (STRING . POSITION), the initial input is STRING, but point
  is placed at _zero-indexed_ position POSITION in STRING.  (*Note*
  that this is different from `read-from-minibuffer' and related
  functions, which use one-indexing for POSITION.)  This feature is
  deprecated--it is best to pass nil for INITIAL-INPUT and supply the
  default value DEF instead.  The user can yank the default value into
  the minibuffer easily using M-x next-history-element.

HIST, if non-nil, specifies a history list and optionally the initial
  position in the list.  It can be a symbol, which is the history list
  variable to use, or it can be a cons cell (HISTVAR . HISTPOS).  In
  that case, HISTVAR is the history list variable to use, and HISTPOS
  is the initial position (the position in the list used by the
  minibuffer history commands).  For consistency, you should also
  specify that element of the history as the value of
  INITIAL-INPUT.  (This is the only case in which you should use
  INITIAL-INPUT instead of DEF.)  Positions are counted starting from
  1 at the beginning of the list.  The variable `history-length'
  controls the maximum length of a history list.

DEF, if non-nil, is the default value or the list of default values.

If INHERIT-INPUT-METHOD is non-nil, the minibuffer inherits
  the current input method and the setting of `enable-multibyte-characters'.

Completion ignores case if the ambient value of
  `completion-ignore-case' is non-nil.

See also `completing-read-function'.

Return value of Lisp expression read using the minibuffer.
Prompt with PROMPT.  If non-nil, optional second arg INITIAL-CONTENTS
is a string to insert in the minibuffer before reading.
(INITIAL-CONTENTS can also be a cons of a string and an integer.
Such arguments are used as in `read-from-minibuffer'.)

Perform completion on buffer names.
If the argument FLAG is nil, invoke `try-completion', if it's t, invoke
`all-completions', otherwise invoke `test-completion'.

The arguments STRING and PREDICATE are as in `try-completion',
`all-completions', and `test-completion'.

Return the user input in a minibuffer as a string.
If the current buffer is not a minibuffer, return its entire contents.

Return the user input in a minibuffer as a string, without text-properties.
If the current buffer is not a minibuffer, return its entire contents.

Return current depth of activations of minibuffer, a nonnegative integer.

Return the prompt string of the currently-active minibuffer.
If no minibuffer is active, return nil.

Return the buffer position of the end of the minibuffer prompt.
Return (point-min) if current buffer is not a minibuffer.

Return t if BUFFER is a minibuffer.
No argument or nil as argument means use current buffer as BUFFER.
BUFFER can be a buffer or a buffer name.

Read the name of a buffer and return as a string.
Prompt with PROMPT.
Optional second arg DEF is value to return if user enters an empty line.
 If DEF is a list of default values, return its first element.
Optional third arg REQUIRE-MATCH determines whether non-existing
 buffer names are allowed.  It has the same meaning as the
 REQUIRE-MATCH argument of `completing-read'.
The argument PROMPT should be a string ending with a colon and a space.
If `read-buffer-completion-ignore-case' is non-nil, completion ignores
case while reading the buffer name.
If `read-buffer-function' is non-nil, this works by calling it as a
function, instead of the usual behavior.

Read the name of a command and return as a symbol.
Prompt with PROMPT.  By default, return DEFAULT-VALUE or its first element
if it is a list.

Read a string from the minibuffer, prompting with string PROMPT.
The optional second arg INITIAL-CONTENTS is an obsolete alternative to
  DEFAULT-VALUE.  It normally should be nil in new code, except when
  HIST is a cons.  It is discussed in more detail below.

Third arg KEYMAP is a keymap to use whilst reading;
  if omitted or nil, the default is `minibuffer-local-map'.

If fourth arg READ is non-nil, interpret the result as a Lisp object
  and return that object:
  in other words, do `(car (read-from-string INPUT-STRING))'

Fifth arg HIST, if non-nil, specifies a history list and optionally
  the initial position in the list.  It can be a symbol, which is the
  history list variable to use, or a cons cell (HISTVAR . HISTPOS).
  In that case, HISTVAR is the history list variable to use, and
  HISTPOS is the initial position for use by the minibuffer history
  commands.  For consistency, you should also specify that element of
  the history as the value of INITIAL-CONTENTS.  Positions are counted
  starting from 1 at the beginning of the list.

Sixth arg DEFAULT-VALUE, if non-nil, should be a string, which is used
  as the default to `read' if READ is non-nil and the user enters
  empty input.  But if READ is nil, this function does _not_ return
  DEFAULT-VALUE for empty input!  Instead, it returns the empty string.

  Whatever the value of READ, DEFAULT-VALUE is made available via the
  minibuffer history commands.  DEFAULT-VALUE can also be a list of
  strings, in which case all the strings are available in the history,
  and the first string is the default to `read' if READ is non-nil.

Seventh arg INHERIT-INPUT-METHOD, if non-nil, means the minibuffer inherits
 the current input method and the setting of `enable-multibyte-characters'.

If the variable `minibuffer-allow-text-properties' is non-nil,
 then the string which is returned includes whatever text properties
 were present in the minibuffer.  Otherwise the value has no text properties.

The remainder of this documentation string describes the
INITIAL-CONTENTS argument in more detail.  It is only relevant when
studying existing code, or when HIST is a cons.  If non-nil,
INITIAL-CONTENTS is a string to be inserted into the minibuffer before
reading input.  Normally, point is put at the end of that string.
However, if INITIAL-CONTENTS is (STRING . POSITION), the initial
input is STRING, but point is placed at _one-indexed_ position
POSITION in the minibuffer.  Any integer value less than or equal to
one puts point at the beginning of the string.  *Note* that this
behavior differs from the way such arguments are used in `completing-read'
and some related functions, which use zero-indexing for POSITION.

Return a Lisp object read using the minibuffer, unevaluated.
Prompt with PROMPT.  If non-nil, optional second arg INITIAL-CONTENTS
is a string to insert in the minibuffer before reading.
(INITIAL-CONTENTS can also be a cons of a string and an integer.
Such arguments are used as in `read-from-minibuffer'.)

Read a string from the terminal, not allowing blanks.
Prompt with PROMPT.  Whitespace terminates the input.  If INITIAL is
non-nil, it should be a string, which is used as initial input, with
point positioned at the end, so that SPACE will accept the input.
(Actually, INITIAL can also be a cons of a string and an integer.
Such values are treated as in `read-from-minibuffer', but are normally
not useful in this function.)
Third arg INHERIT-INPUT-METHOD, if non-nil, means the minibuffer inherits
the current input method and the setting of`enable-multibyte-characters'.

Read a string from the minibuffer, prompting with string PROMPT.
If non-nil, second arg INITIAL-INPUT is a string to insert before reading.
  This argument has been superseded by DEFAULT-VALUE and should normally
  be nil in new code.  It behaves as in `read-from-minibuffer'.  See the
  documentation string of that function for details.
The third arg HISTORY, if non-nil, specifies a history list
  and optionally the initial position in the list.
See `read-from-minibuffer' for details of HISTORY argument.
Fourth arg DEFAULT-VALUE is the default value or the list of default values.
 If non-nil, it is used for history commands, and as the value (or the first
 element of the list of default values) to return if the user enters the
 empty string.
Fifth arg INHERIT-INPUT-METHOD, if non-nil, means the minibuffer inherits
 the current input method and the setting of `enable-multibyte-characters'.

Read the name of a user variable and return it as a symbol.
Prompt with PROMPT.  By default, return DEFAULT-VALUE or its first element
if it is a list.
A user variable is one for which `user-variable-p' returns non-nil.

Specify which minibuffer window to use for the minibuffer.
This affects where the minibuffer is displayed if you put text in it
without invoking the usual minibuffer commands.

Return non-nil if STRING is a valid completion.
Takes the same arguments as `all-completions' and `try-completion'.
If COLLECTION is a function, it is called with three arguments:
the values STRING, PREDICATE and `lambda'.

Return common substring of all completions of STRING in COLLECTION.
Test each possible completion specified by COLLECTION
to see if it begins with STRING.  The possible completions may be
strings or symbols.  Symbols are converted to strings before testing,
see `symbol-name'.
All that match STRING are compared together; the longest initial sequence
common to all these matches is the return value.
If there is no match at all, the return value is nil.
For a unique match which is exact, the return value is t.

If COLLECTION is an alist, the keys (cars of elements) are the
possible completions.  If an element is not a cons cell, then the
element itself is the possible completion.
If COLLECTION is a hash-table, all the keys that are strings or symbols
are the possible completions.
If COLLECTION is an obarray, the names of all symbols in the obarray
are the possible completions.

COLLECTION can also be a function to do the completion itself.
It receives three arguments: the values STRING, PREDICATE and nil.
Whatever it returns becomes the value of `try-completion'.

If optional third argument PREDICATE is non-nil,
it is used to test each possible match.
The match is a candidate only if PREDICATE returns non-nil.
The argument given to PREDICATE is the alist element
or the symbol from the obarray.  If COLLECTION is a hash-table,
predicate is called with two arguments: the key and the value.
Additionally to this predicate, `completion-regexp-list'
is used to further constrain the set of candidates.