Editing Auto-save current buffer periodically

{{TipImported
|id=248
|previous=247
|next=249
|created=May 17, 2002
|complexity=intermediate
|author=salmanhalim
|version=6.0
|rating=14/9
|category1=
|category2=
}}
I have no idea if this was implemented in vim 5.3 or not, but you can definitely do the following kludge in 6.x by using CursorHold and localtime:

When you start reading a file, set a buffer variable to the current time:
 au BufRead,BufNewFile * let b:start_time=localtime()

Set a CursorHold event to check to see if enough time has elapsed since the last save and save if not:
 au CursorHold * call UpdateFile()

Define a function to save the file if needed:

<pre>
" only write if needed and update the start time after the save
function! UpdateFile()
  if ((localtime() - b:start_time) >= 60)
    update
    let b:start_time=localtime()
  else
    echo "Only " . (localtime() - b:start_time) . " seconds have elapsed so far."
  endif
endfunction
</pre>

Reset the start time explicitly after each save.
 au BufWritePre * let b:start_time=localtime()

Obviously, you should get rid of the else portion once you're certain that this does indeed do what you wanted.

The thing to note is that the CursorHold will only fire after 'updatetime' milliseconds of inactivity have elapsed. So, if you type rapidly for one and a half minutes non-stop, it won't actually save anything until you STOP activity long enough. This may be what you want anyway because it won't interrupt your activity with a forced save.

The actual save-delay can be changed from '60' to another number (in seconds) or a variable or anything like that. This entire functionality can be easily wrapped inside a nice script which enables/disables this on a per-buffer basis (maybe with maps etc.). If desired, I can provide that also.

==Comments==
This is cool. However I personally like how swap files do this for me. By default a swap file is writen to after either 200 characters are typed or 4 seconds of inactivity has elapsed. Since a swap file writes faster and updates sooner a recovery is quite simple and sometimes more reliable if something goes wrong.

This is just my personal preference. Some may like the physical auto saving as opposed to swap file recovery. Word for example uses both methods by default. (Yes, I know bad example! Please no flames. ^_^)

----
It wasn't my intention to provide this as a mechanism without knowing about the swap file -- am fully aware of how that works. However, someone had asked about this on the Vim email list and since I posted a longish answer there, I decided to make a tip out of it also.

----

For a normal user this could be quite useful. 

I want to add a word of warning, though. System administrators should be leery about using this. Applications that watch a file and reparse it automatically may have unexpected behavior if it reads a file which contains a partial update. 

While this isn't standard practice in Linux, it does happen -- /etc/crontab is oftentimes handled this way, for instance. 

I don't know if Vim holds the file open in Windows or whether it closes after reading and reopens it to write. If it holds it open, it can't happen in Windows because Windows will keep the file locked until the file is closed. If Vim closes and reopens the file, though, it could also happen in Windows.

This does frequently impact web application configuration files, though. Many web apps will reread the file anytime the CGI is called. In this case, while you're editing the file, the CGI could fail. Editing a PHP-based configuration file will usually show this problem.

[[User:Steven Black|Steven Black]] 18:05, December 9, 2010 (UTC)

----

I want to use autosave only for my notes - that is a file which is typically opened many days in vim and I modify it every now and then. So I created '''~/.vim/ftplugin/notes.vim''':
<pre>
au CursorHold <buffer> update
</pre>

And in such buffer it's just fine to ''':set ft=notes''' and the file is being save periodically.