In order to interact with the external world, Kakoune uses the shell, mainly
through the %sh{ … }
string type, and its control socket.
For synchronous operations, %sh{ … }
blocks are easy to use, they behave
similarly to $( … )
shell construct.
For example, one can echo the current time in Kakoune’s status line using:
:echo %sh{ date }
For asynchronous operations, the Kakoune Unix stream socket can be used. This
is the same socket that Kakoune clients connect to. It is available through the
kak_session
environment variable: the socket is
/tmp/kakoune/${username}/${kak_session}
For example, we can echo a message in Kakoune in 10 seconds with:
:nop %sh{ {
sleep 10
echo "eval -client '$kak_client' 'echo sleep ended'" |
kak -p ${kak_session}
} > /dev/null 2>&1 < /dev/null & }
-
The
nop
command is used so that any eventual output from the%sh{ … }
is not interpreted by Kakoune -
When writing to the socket, Kakoune has no way to guess in which client’s context the command should be evaluated. A temporary context is used, which does not have any user interface, so if we want to interact with the user, we need to use the
eval
command, with its-client
option to send commands to a specific client. -
For the command to run asynchronously, we wrap it in a sub shell with braces, redirect its
std{in,err,out}
to/dev/null
, and run it in background with&
. Using this pattern, the shell does not wait for this sub shell to finish before quitting.
It is a frequent interaction mode to run a program and display its output in a Kakoune buffer.
The common pattern to do that is to use a fifo buffer:
evaluate-commands %sh{
# Create a temporary fifo for communication
output=$(mktemp -d -t kak-temp-XXXXXXXX)/fifo
mkfifo ${output}
# run command detached from the shell
{ run command here > ${output} } > /dev/null 2>&1 < /dev/null &
# Open the file in Kakoune and add a hook to remove the fifo
echo "edit! -fifo ${output} *buffer-name*
hook buffer BufClose .* %{ nop %sh{ rm -r $(dirname ${output})} }"
}
This is a very simple example, most of the time, the echo command will as well contain
set buffer filetype <...>
and some hooks for this filetype will have been written
Filetype specific completion should be provided by external programs.
External completions are provided using an option to store completion, which have the following format.
line.column[+len]@timestamp candidate1|select1|menu1 candidate2|select2|menu2 ...
the first element of this string list specify where and when this completion
applies, the others are a triplet <completion text>|<select cmd>|<menu text>
The select command is executed whenever this menu item gets selected, and
is usually used to display an item specific documentation with
info -placement menu '<menu item description>'
The menu text is a markup string (see :doc faces
markup-strings
), so it can contain {face}
directives.
To effectively use that completion option, it should get added to the completers option.
set -add buffer completers option=my_option_name ---
As a completion program may take some time to compute the candidates, it should run asynchronously. In order to do that, the following pattern may be used:
# Declare the option which will store the temporary filename
decl str plugin_filename
# Declare the completion option
decl completions plugin_completions
# Add plugin_completions to completers for files of good filetype
hook global BufSetOption filetype=my_filetype %{
set -add buffer completers option=plugin_completions
}
evaluate-commands %sh{
# ask Kakoune to write current buffer to temporary file
filename=$(mktemp -t kak-temp.XXXXXXXX)
echo "set buffer plugin_filename '$filename'
write '$filename'"
}
# End the %sh{} so that its output gets executed by Kakoune.
# Use a nop so that any eventual output of this %sh does not get interpreted.
nop %sh{ { # launch a detached shell
buffer="${kak_opt_plugin_filename}"
line="${kak_cursor_line}"
column="${kak_cursor_column}"
# run completer program and format the output in a list of completions
candidates=$(completer $buffer $line $column | completer_filter)
# remove temporary file
rm $buffer
# generate completion option value
completions="$line.$column@$kak_timestamp $candidates"
# write to Kakoune socket for the buffer that triggered the completion
echo "set buffer=${kak_bufname} plugin_completions $completions" |
kak -p ${kak_session}
} > /dev/null 2>&1 < /dev/null & }