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= Expansions

== Strings

\'strings'::
    uninterpreted strings, use a backslash (\') to escape the separator
"strings"::
    expanded strings, % strings (c.f. next section) contained are expended,
    use a backslash (\\%) to escape the separator
%\{strings\}::
    these strings are very useful when entering commands
+
    * the '{' and '}' delimiters are configurable, any non alphanumeric
    character can be used
+
----------------------------------------------------------
e.g. %[string], %<string>, %(string), %~string~, %!string!
----------------------------------------------------------
    * if the character following '%' is one of '{[(<', then the closing
    one is the matching '}])>' and the delimiters are not escapable but
    are nestable
+
-----------------------------------------------------------
e.g. %{ roger {}; } is a valid string, %{ marcel \} as well
-----------------------------------------------------------

== Typed expansions

%\{strings\} can have an expansion type between the *%* and the opening
character. They will be written *%<type>\{<content>\}*. They will be
expanded according to the given *<type>* using *<content>* as its
parameter:

*sh*::
    shell expansion, similar to posix shell '$(...)' construct (c.f. next
    section)
*reg*::
    register expansion, will expand to the content of the register named
    by *<content>*.
*opt*::
    option expansion, will expand to the value of the option named by
    *<content>*
*val*::
    value expansion, will expand to the value of the environment variables
    available to shell expansion. *<content>* shall be the name of that
    variable without the *kak_* prefix.
*arg*::
    argument expansion, expand to the arguments of the current
    command, *<content>* can be a number, or @ for all arguments

== Shell expansions

The '%sh{...}' expansion replaces its content with the output of the
shell commands in it. The following environment variables are used to pass
informations about Kakoune's state:

*kak_selection*::
    content of the main selection
*kak_selections*::
    content of the selection separated by colons, colons in the selection
    contents are escaped with a backslash
*kak_selection_desc*::
    range of the main selection, represented as anchor,cursor; anchor
    and cursor are in this format: line.column
*kak_selections_desc*::
    range of the selections separated by colons
*kak_bufname*::
    name of the current buffer
*kak_buffile*::
    full path of the file or same as kak_bufname when there’s no
    associated file
*kak_buflist*::
    the current buffer list, each buffer separated by a colon
*kak_buf_line_count*::
    the current buffer line count
*kak_timestamp*::
    timestamp of the current buffer, the timestamp is an integer value
    which is incremented each time the buffer is modified
*kak_history_id*::
    history id of the current buffer, the history id is an integer value
    which is used to reference a specific buffer version in the undo tree
*kak_runtime*::
    directory containing the kak support files, determined from kakoune's
    binary location.
*kak_config*::
    directory containing the user configuration
*kak_count*::
    count parameter passed to the command
*kak_register*::
    register parameter passed to the command
*kak_opt_<name>*::
    value of option *name*
*kak_reg_<r>*::
    value of register *r*
*kak_session*::
    name of the current session
*kak_client*::
    name of the current client
*kak_client_pid*::
    process id of the current client
*kak_client_list*::
    list of clients connected to the current session
*kak_source*::
    path of the file currently getting executed (through the source
    command)
*kak_modified*::
    buffer has modifications not saved
*kak_cursor_line*::
    line of the end of the main selection
*kak_cursor_column*::
    column of the end of the main selection (in byte)
*kak_cursor_char_value*::
    unicode value of the codepoint under the cursor
*kak_cursor_char_column*::
    column of the end of the main selection (in character)
*kak_cursor_byte_offset*::
    Offset of the main selection from the beginning of the buffer (in bytes).
*kak_window_width*::
    width of the current kakoune window
*kak_window_height*::
    height of the current kakoune window
*kak_hook_param*::
    filtering text passed to the currently executing hook
*kak_hook_param_capture_N*::
    text captured by the hook filter regex capture N
*kak_client_env_<name>*::
    value of the *name* variable in the client environment
    (e.g. *$kak_client_env_SHELL* is the SHELL variable)

Note that in order for Kakoune to pass a value in the environment, the
variable has to be spelled out within the body of the expansion.

Those environment variables are available in every context where
Kakoune use a shell command, such as the `|`, `!` or `$` normal
mode commands (See <<keys#,`:doc keys`>>).

== Markup strings

In certain contexts, Kakoune can take a markup string, which is a string
containing formatting informations. In these strings, the {facename}
syntax will enable the face facename until another face gets activated,
or the end of the string is reached.

Literal '{' characters shall be written '\{', and a literal backslash ('\')
that precedes a '{' character shall be escaped as well ('\\').