I found a way to do this in this question: [https://graphicdesign.stackexchange.com/questions/50051/inkscape-center-drawing-to-page-via-command-line-terminal/50052#50052][1]

With "foo.svg" as the image to edit:

    inkscape --verb=EditSelectAll --verb=AlignHorizontalCenter --verb=AlignVerticalCenter --verb=FileSave --verb=FileQuit foo.svg

To edit all svg images in the current directory:

    inkscape --verb=EditSelectAll --verb=AlignHorizontalCenter --verb=AlignVerticalCenter --verb=FileSave --verb=FileClose *.svg

But this second command opens a ton of windows, which will make your computer crash if you're editing too many images. For **Linux only**, this command will work better:

    for img in $(ls *.svg) ; do inkscape --verb=EditSelectAll --verb=AlignHorizontalCenter --verb=AlignVerticalCenter --verb=FileSave --verb=FileQuit $img ; done

For the above command, if any of the files are symlinks, Inkscape will edit the target file that the symlink points  to. If you don't want Inkscape to do this, you can filter out any symlinks with this command:

    for img in $(ls *.svg) ; do if [[ $(readlink $img) == "" ]] ; then inkscape --verb=EditSelectAll --verb=AlignHorizontalCenter --verb=AlignVerticalCenter --verb=FileSave --verb=FileQuit $img ; fi ; done

<hr></hr>
While I'm at it, I might as well post the bash script I made for this:

	#!/bin/bash
	# inkscape-center <file-or-directory>...

	_analyse() {
		if [ -d "${1}" ] ; then
			_centerAll "${1}" ;
		else
			_center "${1}" ;
		fi
	}

	_centerAll() {
		cd "${1}" ;
		for img in $(ls "*.svg") ; do
			_filterSyms "${img}" ;
		done
	}

	_filterSyms() {
		if [[ $(readlink "${1}") == "" ]] ; then
			_center "${1}"
		fi
	}

	_center() {
		inkscape --verb=EditSelectAll --verb=AlignHorizontalCenter --verb=AlignVerticalCenter --verb=FileSave --verb=FileQuit "${1}"
	}

	for arg ; do
		_analyse "${arg}" ;
	done

I called it `inkscape-center` and run it like this:

    inkscape-center <file-or-directory>

It takes as many arguments as you want, so you can do something like this:

    inkscape-center 1st.svg 2nd.svg 3rd.svg 4th.svg

**Be careful**- If you specify a directory instead of a file, it'll edit every svg file in that directory.


  [1]: https://graphicdesign.stackexchange.com/questions/50051/inkscape-center-drawing-to-page-via-command-line-terminal/50052#50052