124 lines
4.1 KiB
Plaintext
124 lines
4.1 KiB
Plaintext
Interfacing Kakoune with external programs
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==========================================
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In order to interact with the external world, Kakoune uses the shell, mainly
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through the +%sh{ ... }+ string type, and it's control socket.
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Basic interaction
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-----------------
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For synchronous operations, +%sh{ ... }+ blocks are easy to use, they behave
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similarly to +$( ... )+ shell construct.
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For example, one can echo the current time in Kakoune status line using:
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[source,bash]
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----
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:echo %sh{ date }
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----
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For asynchronous operations, the Kakoune Unix stream socket can be used. This
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is the same socket that Kakoune clients connect to. It is available through
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+kak_session+ environment variable: the socket is +/tmp/kak-${kak_session}+
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For example, we can echo a message in Kakoune in 10 seconds with:
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[source,bash]
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----
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:nop %sh{ (
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sleep 10
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echo "eval -client '$kak_client' 'echo sleep ended'" |
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kak -p ${kak_session}
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) >& /dev/null < /dev/null & }
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----
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* The +nop+ command is used so that any eventual output from the
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+%sh{ ... }+ is not interpreted by Kakoune
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* When writing to the socket, Kakoune has no way to guess in which
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client's context the command should be evaluated. A temporary
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context is used, which does not have any user interface, so if we want
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to interact with the user, we need to use the +eval+ command, with
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it's +-client+ option to send commands to a specific client.
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* For the command to run asynchronously, we wrap it in a sub shell
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with parenthesis, redirect it's +std{in,err,out}+ to +/dev/null+, and
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run it in background with +&+. Using this pattern, the shell does
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not wait for this sub shell to finish before quitting.
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Interactive output
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------------------
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It is a frequent interaction mode to run a program and display it's output
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in a Kakoune buffer.
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The common pattern to do that is to use a fifo buffer:
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[source,bash]
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-----
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%sh{
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# Create a temporary fifo for communication
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output=$(mktemp -d -t kak-temp-XXXXXXXX)/fifo
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mkfifo ${output}
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# run command detached from the shell
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( run command here >& ${output} ) >& /dev/null < /dev/null &
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# Open the file in Kakoune and add a hook to remove the fifo
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echo "edit! -fifo %{output} *buffer-name*
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hook buffer BufClose .* %{ nop %sh{ rm -r $(dirname ${output}} }"
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}
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-----
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This is a very simple example, most of the time, the echo command will as
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well contains
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-----
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set buffer filetype <...>
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-----
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and some hooks for this filetype will have been written
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Completion candidates
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---------------------
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Most of the time, filetype specific completion should be provided by
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external programs.
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external completions are provided using the +completions+ option, which
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have the following format.
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----
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line.column[+len]@timestamp:candidate1:candidate2:...
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----
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the first element of this string list specify where and when this completions
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applies, the others are simply completion candidates.
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As a completion program may take some time to compute the candidates, it should
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run asynchronously. In order to do that, the following pattern may be used:
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[source,bash]
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-----
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# Declare the option which will store the temporary filename
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decl str plugin_filename
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%sh{
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# ask Kakoune to write current buffer to temporary file
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filename=$(mktemp -t kak-temp.XXXXXXXX)
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echo "set buffer plugin_filename '$filename'
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write '$filename'"
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}
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# End the %sh{} so that it's output gets executed by Kakoune.
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# Use a nop so that any eventual output of this %sh does not get interpreted.
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nop %sh{ ( # launch a detached shell
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buffer="${kak_opt_plugin_filename}"
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line="${kak_cursor_line}"
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column="${kak_cursor_column}"
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# run completer program and put output in colon separated format
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candidates=$(completer $buffer $line $column | completer_filter)
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# remove temporary file
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rm $buffer
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# generate completion option value
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completions="$line.$column@$kak_timestamp:$candidates"
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# write to Kakoune socket for the buffer that triggered the completion
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echo "set buffer=${kak_bufname} completions '$completions'" |
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kak -p ${kak_session}
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) >& /dev/null < /dev/null & }
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-----
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