How Dropbox saved my command line

August 10, 2009

I live in the command line across many Unix-like platforms and networks. I have two Mac laptops, two Linux workstations, shell logins scattered across the multiverse, and even a couple Windows VMs to boot. I’ve tried versioning my shell configuration files, but that requires me to check in/check out my changes across all environments. This turned out to be less than ideal. More manual effort, more hassle.

Enter Dropbox that syncs the files across multiple machines seamlessly and even gives you a bit of revision history. I concocted a system on top of Dropbox that allows me to have global, per OS, and per machine shell configs. For example, here are all the Bash config files I keep in sync via Dropbox (machine names changed to protect the innocent):

$ ls ~/Dropbox/shell/bash
bashbootstrap  bashrc
bashrc-Darwin  bashrc-Darwin-laptopname  bashrc-Darwin-mininame
bashrc-Linux  bashrc-Linux-machineone  bashrc-Linux-machinetwo

Let’s ignore the bashbootstrap file for the moment. You will notice that we have a globally-applied config file, bashrc, two OS specific config files, bashrc-Linux, bashrc-Darwin, and several machine specific ones. (By the way, Darwin is the name of OS X’s BSD-like kernel.)

What ties it all together is the bashbootstrap file. It loads each applicable config file in order of increasing specificity, this allows per OS and per machine overrides to have higher precedence. Additionally, we silently skip missing config files; you need not create empty config files for each of your machines to keep the script happy.

On a new machine, after installing Dropbox on ~/Dropbox, I move away the default .bashrc and just symlink the bootstrap file in its place instead:

$ mv ~/.bashrc ~/.bashrc.bak
$ ln -s ~/Dropbox/shell/bash/bashbootstrap  ~/.bashrc

Oh, and here are the contents of the bashbootstrap file:

if [ -z "$PS1" ]; then
   return
fi

dropboxshelldir=~/Dropbox/shell
dropboxdir=$dropboxshelldir/bash
masterbashrc=$dropboxdir/bashrc
osbashrc=$masterbashrc-`uname`
localbashrc=$osbashrc-`hostname | cut -d. -f1`

echo -n "Applicable shell configs: "
for bashfile in "$masterbashrc" "$osbashrc" "$localbashrc"; do
  if [ -r $bashfile ]; then
    . $bashfile
    echo -n "`basename $bashfile` "
  fi
done
echo

# Set convenience aliases
myed=${VISUAL:-${EDITOR:-vim}}
alias editbashrc="$myed $masterbashrc"
alias editosbashrc="$myed $osbashrc"
alias editlocalbashrc="$myed $localbashrc"

One final note, this script also provides three convenience aliases for editing your Bash config files without having to remember where they are stored.