Can vim monitor realtime changes to a file - vim

Question

My question is similar to this how to monitor a text file in realtime
but I want to do it in vim. I know I can read an opened file use tail -f sample.xml file, and when new content is written to the file, it'll also write the new content to my screen. Can I have vim automatically fill the new data when a file is updated?

Answer 1

You can :set autoread so that vim reads the file when it changes. However (depending on your platform), you have to give it focus.
From the help:
When a file has been detected to have
been changed outside of Vim and it
has not been changed inside of Vim,
automatically read it again. When the
file has been deleted this is not
done.

Answer 2

Don't know about automatically, but you can type:
:e!
to reload the file

Answer 3

Put the following in your .vimrc:
" check one time after 4s of inactivity in normal mode
set autoread
au CursorHold * checktime

Answer 4

like #flukus said in a comment to a previous answer you can call feedkeys["lh"] (it moves the cursor to the right and back to the left, which normaly doesn't do harm when viewing a log file)
So, if you combine the rest of the answer you have a oneliner you can run from ex (whithin vim) when needed:
:set autoread | au CursorHold * checktime | call feedkeys("lh")
***(if you would want to jump (nearly) to the end of the file, just use "G" instead of "lh" with feedkeys)***
Explanation:
autoread: reads the file when changed from the outside (but it doesnt work on its own, there is no internal timer or something like that. It will only read the file when vim does an action, like a command in ex :!
CursorHold * checktime: when the cursor isn't moved by the user for the time specified in 'updatetime' (which is 4000 miliseconds by default) checktime is executed, which checks for changes from outside the file
call feedkeys("lh"): the cursor is moved once, right and back left. and then nothing happens (... which means, that CursorHold is triggered, which means we have a loop)
Additionally you can :set syntax=logtalk to color the log
To stop the scrolling when using call feedkeys("G"), execute :set noautoread - now vim will tell, that the file was change ans ask if one wants to read the changes or not)
(Does this have any sideeffects?)
Edit: I see one side-effect: if one uses "G" as the feedkey, it will scroll down every currently opened buffer?! So, it's not possible to work in the left buffer of a splittet window while having the right buffer scroll down a logfile automatically
Edit2: Another side effect is that when you enter the command line window(by using q:) an error message always pops up.

Answer 5

Stick this in your .vimrc and it should work like a boss. (Taken from: http://vim.wikia.com/wiki/Have_Vim_check_automatically_if_the_file_has_changed_externally)
" Function to Watch for changes if buffer changed on disk
function! WatchForChanges(bufname, ...)
" Figure out which options are in effect
if a:bufname == '*'
let id = 'WatchForChanges'.'AnyBuffer'
" If you try to do checktime *, you'll get E93: More than one match for * is given
let bufspec = ''
else
if bufnr(a:bufname) == -1
echoerr "Buffer " . a:bufname . " doesn't exist"
return
end
let id = 'WatchForChanges'.bufnr(a:bufname)
let bufspec = a:bufname
end
if len(a:000) == 0
let options = {}
else
if type(a:1) == type({})
let options = a:1
else
echoerr "Argument must be a Dict"
end
end
let autoread = has_key(options, 'autoread') ? options['autoread'] : 0
let toggle = has_key(options, 'toggle') ? options['toggle'] : 0
let disable = has_key(options, 'disable') ? options['disable'] : 0
let more_events = has_key(options, 'more_events') ? options['more_events'] : 1
let while_in_this_buffer_only = has_key(options, 'while_in_this_buffer_only') ? options['while_in_this_buffer_only'] : 0
if while_in_this_buffer_only
let event_bufspec = a:bufname
else
let event_bufspec = '*'
end
let reg_saved = #"
"let autoread_saved = &autoread
let msg = "\n"
" Check to see if the autocommand already exists
redir #"
silent! exec 'au '.id
redir END
let l:defined = (#" !~ 'E216: No such group or event:')
" If not yet defined...
if !l:defined
if l:autoread
let msg = msg . 'Autoread enabled - '
if a:bufname == '*'
set autoread
else
setlocal autoread
end
end
silent! exec 'augroup '.id
if a:bufname != '*'
"exec "au BufDelete ".a:bufname . " :silent! au! ".id . " | silent! augroup! ".id
"exec "au BufDelete ".a:bufname . " :echomsg 'Removing autocommands for ".id."' | au! ".id . " | augroup! ".id
exec "au BufDelete ".a:bufname . " execute 'au! ".id."' | execute 'augroup! ".id."'"
end
exec "au BufEnter ".event_bufspec . " :checktime ".bufspec
exec "au CursorHold ".event_bufspec . " :checktime ".bufspec
exec "au CursorHoldI ".event_bufspec . " :checktime ".bufspec
" The following events might slow things down so we provide a way to disable them...
" vim docs warn:
" Careful: Don't do anything that the user does
" not expect or that is slow.
if more_events
exec "au CursorMoved ".event_bufspec . " :checktime ".bufspec
exec "au CursorMovedI ".event_bufspec . " :checktime ".bufspec
end
augroup END
let msg = msg . 'Now watching ' . bufspec . ' for external updates...'
end
" If they want to disable it, or it is defined and they want to toggle it,
if l:disable || (l:toggle && l:defined)
if l:autoread
let msg = msg . 'Autoread disabled - '
if a:bufname == '*'
set noautoread
else
setlocal noautoread
end
end
" Using an autogroup allows us to remove it easily with the following
" command. If we do not use an autogroup, we cannot remove this
" single :checktime command
" augroup! checkforupdates
silent! exec 'au! '.id
silent! exec 'augroup! '.id
let msg = msg . 'No longer watching ' . bufspec . ' for external updates.'
elseif l:defined
let msg = msg . 'Already watching ' . bufspec . ' for external updates'
end
echo msg
let #"=reg_saved
endfunction
let autoreadargs={'autoread':1}
execute WatchForChanges("*",autoreadargs)

Answer 6

Tail Bundle should do what you want. Note, haven't used it myself.

Answer 7

There is a plugin also:
https://github.com/djoshea/vim-autoread
This was the only way I could make this work on OSX.

Answer 8

If unix + neovim
:term tail -f <filename>
Obviously this won't work for everyone, but it's how I do it.

Answer 9

To enable reloading if you open a specific file, you can add this to your .vimrc and use a modeline like vim: set ft+=.watch:. It takes advantage of the feature to set multiple filetypes for a buffer (see below):
vim9script
command WatchFiles {
autocmd! AUWatchFile FocusGained,VimResume,BufEnter,WinEnter,CursorHold * checktime
autocmd! AUWatchFile BufEnter,InsertEnter,CursorHold,CursorHoldI <buffer> checktime
setlocal autoread
checktime
}
command UnwatchFiles {
autocmd! AUWatchFile
set autoread<
}
# To enable this, you may use e.g. a modeline: `vim: set ft+=.watch`
def WatchAutomatically()
# Check if the "list" of filetypes (a dot separated string) contains 'watch'.
if -1 != match(&filetype, "\\(^\\|\\.\\)watch\\($\\|\\.\\)")
WatchFiles
endif
enddef
augroup AUWatchFile | augroup END
autocmd BufWinEnter * call WatchAutomatically()
More details
You are able to set multiple filetypes separated by .:
When a dot appears in the value then this separates two filetype
names. Example:
/* vim: set filetype=c.doxygen : */ ~
See :help 'filetype'.
Keep in mind that you should manipulate the filetype first and set additional options after that in the modeline. Otherwise these options may be overridden by the settings specific for the filetype.
Btw, the above is a Vim9 script (which I discovered today). Translating it back to a good-old Vim script is trivial:
Use " for comments.
Transform multi-line commands like this:
command UnwatchFiles
\ autocmd! AUWatchFile
\ | set autoread<
Remove the vim9script line.
See :help Vim9-script for details.
Shortcomings
Reloading is not limited to the buffer which contains the modeline. You may disable it again with :UnwatchFiles.
It is still dump polling.

Answer 10

VIM will warn you when a file has been updated so that you don't overwrite changes that have been made since you opened it. It will prompt you at that point to reload the file.