Becoming root from inside Vim

Question

Sometimes I start editing configuration files in /etc using Vim, but forget to use sudo to start Vim. The inevitable result then is that after finishing my edits I encounter the dreaded notice that I don't have the permission to save the file.

Mostly the edits are small enough that I just exit Vim and do the whole thing again as root. I could of course save to a location I can write to and then copy as root, but that is also somewhat annoying.

But I'm sure there is an easier way to become root or use sudo from inside Vim, without having to discard the changes. If the method would not rely on sudo being set up for the user that would be even better.

Solution 1

sudo cannot change the effective user of an existing process, it always creates a new process that has the elevated privileges and the original shell is unaffected. This is a fundamental of UNIX design. I most often just save the file to /tmp as a workaround. If you really want to save it directly you might try using a feature of Vim where it can pipe a file to another process. Try saving with this command:

:w !sudo dd of=%

Tested and works. Vim will then ask you to reload the file, but it's unnecessary: you can just press o to avoid reloading and losing your undo history. You can even save this to a Vim command/function or even bind it to a key for easy access, but I'll leave that as an exercise to the reader.

Solution 2

Saving the file as root:

:w !sudo tee %

Solution 3

Call sudoedit to edit files as root.

Think of the inconvenience when calling vim directly as a warning that you're being too casual in doing something potentially dangerous.

Solution 4

You can put this in your .vimrc

cmap w!! %!sudo tee > /dev/null %

You trigger it by doing :w!! - it will push the file through sudo tee to the current filename (%).

From a now-deleted post at https://stackoverflow.com/questions/95072/what-are-your-favorite-vim-tricks; see also: https://stackoverflow.com/questions/1218390/what-is-your-most-productive-shortcut-with-vim

Solution 5

This also works well:

:w !sudo sh -c "cat > %"

This is inspired by the comment of @Nathan Long in this answer.

NOTICE:

" must be used instead of ' because we want % to be expanded before passing to shell.

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Comments

[Admin]

I got into the habit of using sudoedit instead of vim for all admin editing. It's one way to never run into this problem anymore :). +1 for Gilles' answer.

[Admin]

These alernative Q&A's from SO are useful so linking to them here: Getting root permissions on a file inside of vi? & How does the vim “write with sudo” trick work?.

[msaif]

You should wrap the % in quotes in case the filename contains a space.

[msaif]

Also: this will not reset the 'modified' setting; you can do that manually with set nomodified.

[msaif]

Actually, if you really want to be careful, you should do exec 'w !sudo dd of=' . shellescape(expand('%')) in case the filename contains quotes, backslashes, dollar-signs, etc.

[jwodder]

How is that different to the Commandlinefu -command by plaes?

[penguin359]

@hhh Using tee as @plaes suggests will send the entire file to your terminal screen as well as write it out to the filesystem which may not be very desirable, especially when editing a large file over a slow terminal/network connection.

[jw013]

One could always add > /dev/null to the tee command.

[penguin359]

Hmm, maybe someone needs to post the performance comparison between using "dd of=%" vs. "tee % >/dev/null" On one hand dd copies using tiny 512 byte blocks, but on the other hand, tee spins it's wheels writing a full copy of the file to the bit-bucket. I wonder who will win in the end.

[towo]

And if you've got moreutils installed, just use !sudo sponge % instead.

[TamaMcGlinn]

this throws an error for me: sudo: no tty present and no askpass program specified. askpass is accessible directly and works fine normally.