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job_control.txt    Nvim


                 NVIM REFERENCE MANUAL    by Thiago de Arruda


Nvim job control                                        job job-control

Job control is a way to perform multitasking in Nvim, so scripts can spawn and
control multiple processes without blocking the current Nvim instance.

                                      Type gO to see the table of contents.

==============================================================================
Concepts

Job Id                                                  job-id

Each job is identified by an integer id, unique for the life of the current
Nvim session. Each job-id is a valid channel-id: they share the same "key
space". Functions like jobstart() return job ids; functions like
jobstop(), chansend(), rpcnotify(), and rpcrequest() take job ids.

Job stdio streams form a channel which can send and receive raw bytes or
msgpack-rpc messages.

==============================================================================
Usage                                                   job-control-usage

To control jobs, use the "job…" family of functions: jobstart(),
jobstop(), etc.

Example: 

    function! s:OnEvent(job_id, data, event) dict
      if a:event == 'stdout'
        let str = self.shell.' stdout: '.join(a:data)
      elseif a:event == 'stderr'
        let str = self.shell.' stderr: '.join(a:data)
      else
        let str = self.shell.' exited'
      endif

      call append(line('$'), str)
    endfunction
    let s:callbacks = {
    \ 'on_stdout': function('s:OnEvent'),
    \ 'on_stderr': function('s:OnEvent'),
    \ 'on_exit': function('s:OnEvent')
    \ }
    let job1 = jobstart(['bash'], extend({'shell': 'shell 1'}, s:callbacks))
    let job2 = jobstart(['bash', '-c', 'for i in {1..10}; do echo hello $i!; sleep 1; done'], extend({'shell': 'shell 2'}, s:callbacks))

To test the above script, copy it to a file ~/foo.vim and run it: 
    nvim -u ~/foo.vim

Description of what happens:
  - Two bash shells are spawned by jobstart() with their stdin/stdout/stderr
    streams connected to nvim.
  - The first shell is idle, waiting to read commands from its stdin.
  - The second shell is started with -c which executes the command (a for-loop
    printing 0 through 9) and then exits.
  - OnEvent() callback is passed to jobstart() to handle various job
    events. It displays stdout/stderr data received from the shells.

For on_stdout and on_stderr see channel-callback.
                                                        on_exit
Arguments passed to on_exit callback:
  0: job-id
  1: Exit-code of the process, or 128+SIGNUM if by signal (e.g. 143 on SIGTERM).
  2: Event type: "exit"


  Note: Buffered stdout/stderr data which has not been flushed by the sender
        will not trigger the on_stdout/on_stderr callback (but if the process
        ends, the on_exit callback will be invoked).
        For example, "ruby -e" buffers output, so small strings will be
        buffered unless "auto-flushing" ($stdout.sync=true) is enabled. 
          function! Receive(job_id, data, event)
            echom printf('%s: %s',a:event,string(a:data))
          endfunction
          call jobstart(['ruby', '-e',
            \ '$stdout.sync = true; 5.times do sleep 1 and puts "Hello Ruby!" end'],
            \ {'on_stdout': 'Receive'})
       https://github.com/neovim/neovim/issues/1592

  Note 2:
        Job event handlers may receive partial (incomplete) lines. For a given
        invocation of on_stdout/on_stderr, a:data is not guaranteed to end
        with a newline.
          - abcdefg may arrive as ['abc'], ['defg'].
          - abc\nefg may arrive as `['abc', '']`, ['efg'] or ['abc'],
            ['','efg'], or even ['ab'], ['c','efg'].
        Easy way to deal with this: initialize a list as [''], then append
        to it as follows: 
          let s:chunks = ['']
          func! s:on_stdout(job_id, data, event) dict
            let s:chunks[-1] .= a:data[0]
            call extend(s:chunks, a:data[1:])
          endf


The jobstart-options dictionary is passed as self to the callback.
The above example could be written in this "object-oriented" style: 

    let Shell = {}

    function Shell.on_stdout(_job_id, data, event)
      call append(line('$'),
            \ printf('[%s] %s: %s', a:event, self.name, join(a:data[:-2])))
    endfunction

    let Shell.on_stderr = function(Shell.on_stdout)

    function Shell.on_exit(job_id, _data, event)
      let msg = printf('job %d ("%s") finished', a:job_id, self.name)
      call append(line('$'), printf('[%s] BOOM!', a:event))
      call append(line('$'), printf('[%s] %s!', a:event, msg))
    endfunction

    function Shell.new(name, cmd)
      let object = extend(copy(g:Shell), {'name': a:name})
      let object.cmd = ['sh', '-c', a:cmd]
      let object.id = jobstart(object.cmd, object)
      $
      return object
    endfunction

    let instance = Shell.new('bomb',
          \ 'for i in $(seq 9 -1 1); do echo $i 1>&$((i % 2 + 1)); sleep 1; done')

To send data to the job's stdin, use chansend(): 
    :call chansend(job1, "ls\n")
    :call chansend(job1, "invalid-command\n")
    :call chansend(job1, "exit\n")

A job may be killed with jobstop(): 
    :call jobstop(job1)

A job may be killed at any time with the jobstop() function:

    :call jobstop(job1)

Individual streams can be closed without killing the job, see chanclose().

==============================================================================
 vim:tw=78:ts=8:noet:ft=help:norl:


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