TweetFollow Us on Twitter

Mac in the Shell: Dropbox in the Shell

Volume Number: 26
Issue Number: 03
Column Tag: Mac in the Shell

Mac in the Shell: Dropbox in the Shell

Or, Integrating Dropbox and bash!

by Edward Marczak

Welcome

Last month, I promised to get back to some shell topics. This month, I'll do just that. I've become a pretty big fan of Dropbox (http://getdropbox.com). However, it's rare that I access it directly in the GUI. This makes simplifying my life with Dropbox in a shell a pretty high priority. This article will look at how I've integrated Dropbox and my bash shell environment.

Why Dropbox?

If you're unfamiliar with Dropbox, it's a cloud-based storage solution that two-way syncs between the Dropbox servers and a folder on any machines that you've installed the Dropbox client on. Of course, like Apple's iDisk, you provide credentials, so it only syncs your files. Dropbox is cross-platform and has clients for Mac, Linux and Windows. Dropbox allows you to define where your local Dropbox folder is located. Unlike iDisk, which tries to act like it's magic and shield you from its workings, Dropbox acts much more naturally. You are asked to define a folder that is your Dropbox. That's it. From then on, anything that you put in that folder is kept in sync.

I don't want to spend too much time on why I love Dropbox. You're either using Dropbox already and know how good it is, you're thinking of trying it (go try it now at the link mentioned in the intro) or have decided that you don't care for it. If you're in the latter camp, perhaps this article can give you some ideas for similar challenges you may face.

I work on different computers all the time: I have several at work and a few at home. This was quite a challenge for me initially since I had long used the traditional one-laptop-for-everything setup. While I don't need identical environments on every machine I use, there are certain aspects I like to configure in a similar manner. There are also certain tools that I'd like to have access to and certain files that I want to tote about. I have a MobileMe account, so, why don't I just use iDisk for this?

Initially, I tried to use iDisk, but the first barrier was that iDisk is just unbearably slow. Even with a pretty fast connection to the Internet, sync times were just unacceptable. The sync routine for iDisk is also a bit messy. It would often complain of file conflicts for no reason that I could figure out. This is disruptive, as the conflict dialog just pops up over whatever you're doing. Constantly. Perhaps the biggest deal-breaker is that iDisk does not support symlinks. Well, if you keep a local copy of your iDisk, symlinks work fine locally, but they will not be synced up to MobileMe, and therefore won't come down to any other computers syncing to the same iDisk.

There were even more issues, but that was enough for me to start looking for alternatives. A number of friends were using Dropbox, so I gave it a try. Well, everything that I just mentioned is wrong with iDisk is just fine in Dropbox. First, it's fast. Second, it feels better integrated into Mac OS X than just about any third-party product that I've used, and possibly even more so than iDisk. It's absolutely invisible. Finally, my favorite: symlinks work just fine (even though I've modified my workflow and not using them much anymore).

Shell Integration

When I said earlier that Dropbox is very 'natural' and behaves as one would expect, that includes how it responds in a shell. While iDisk mounts a local diskimage, you can't define where that is located. (Well, OK...the disk image is stored in ~/Library/FileSync/(FS_identifier)/(MobileMe_username)_iDisk.sparsebundle and I suppose you could symlink it somewhere. But that doesn't stop the mount from appearing in /Volumes). The Dropbox folder, on the other hand, acts just like any folder (directory) on the system. You can view it in the GUI, or you can list it in a shell. You can 'cd' to it in a shell and manipulate it. Like you'd expect.

That all seems pretty good, right? How much more would you expect to do? Here are some ideas.

Where's Dropbox?

Since Dropbox, as a solution is intended for multiple computers, each computer needs its own client install. Nothing says that the location of the Dropbox folder must be the same on each. By default, the Dropbox installer offers to put the defined folder in your home directory. However, I often move that into /Users/Shared or other locations. I've certainly developed variances among my installs. This is pretty easy to solve using a common shell convention: environment variables.

A review on environment variables: like most shells, bash supports session-persistent in-memory variables. Variables can store string or numeric values. There's even an array type, but it's seldom used and fairly tricky ugly to handle. (Seriously, if you're trying to use arrays in bash you should really consider moving to a scripting language that had arrays in mind from the beginning. Ruby and Python are two excellent examples).

Two important characteristics about environment variables: 1) They're available in all shell contexts. That is, they're defined in each shell you create, and any that fork from that shell. 2) When the $ character is encountered, the shell performs variable expansion. This lets us use variables that we've defined to build up other strings and commands.

The first think that I want to know is this: where is the Dropbox folder on the machine I'm using? Conveniently, Dropbox stores all installation information in an sqlite3 database in a user's home directory. One of the rows of the database is the path to the current Dropbox folder. Excellent. Mac OS X loves sqlite3 and has the command-line binary built-in. Extracting the value of the path is easy:

sqlite3 ~/.dropbox/dropbox.db 'select value from config 
where key="dropbox_path"'
Vi9Wb2x1bWVzL2bbhWVzL1VzZXJzL1YoMTMlZC9nZXJtERMyb3Bib3gKcDEKLg==

Oh, what's this? Unsurprisingly, this value is not stored as plain text. Nor, though, is it encrypted. It's base64 encoded and 'pickled' for serialization. Looks like the Dropbox developers are fans of Python. Python supports a serialization library called 'pickle'. This causes us to run into a small, but surmountable issue: there are no tools that allow us to directly unpickle an object completely within bash. I wrote a small utility in Python that gets me all of this information, but I promised to focus on the shell only, and this is a good opportunity to explore more tools.

First, we'll use the sqlite3 command to get the information from the database. As shown above, the command needs to know which database to read and the SQL command to run against the database. The HOME variable is defined for us in a shell environment, and points to the home directory of the current user. So, the command I'll recommend (and shown in the complete example) uses the ${HOME} variable over the '~' character.

Next, we need to base64 decode the value we get out of the database. OS X doesn't have a single, explicit command that performs a base64 decode. Again, you could use a Python or Perl one-liner, but I prefer to use the multi-faceted openssl binary, which contains a base64 decode routine.

One the value is base64 decoded, you'll notice some extra characters at the beginning of the output, and one on a separate line. This is a result of the pickle serialization. Let's get rid of the separate, second line right away. To do this, I use head. The head utility is a counterpart to tail. The former will display the first n number of lines from the beginning of a file, while the latter will display the last n lines from the end of a file. We only want the first line, so, we pass that information in as an argument. Finally, there's that one extra character up front. We can trim that out with the cut command. We simply tell cut that we only want from character (the -c switch) 2 onward.

If you remember pipes, they come in handy here. A pipe connects the output of one binary to the input of another. Often, programs operate on files on-disk. For example, the head utility can be used like this:

head -3 filename.txt

That will display the first three lines of the file filename.txt. Well, Unix treats just about everything as a file-even input and output. In the case of using a pipe, you're taking the standard output (represented as a file as /dev/stdout) of one program and making it the input (/dev/stdin) of another application (one that reads standard in. Not all do).

Stringing it all together, the final command looks like this:

sqlite3 ${HOME}/.dropbox/dropbox.db 'select value from config where 
key="dropbox_path"' | openssl base64 -d | head -1 | cut -c 2-

This displays where the current user's Dropbox folder is. More than display it, we want to store it for future use. Here's what I'd put in my .bash_profile script to accomplish this:

# Setup Dropbox Location - used in scripts
DB=$(sqlite3 ${HOME}/.dropbox/dropbox.db 'select value from config where key="dropbox_path"'
| openssl base64 -d | head -1 | cut -c 2-)

This takes advantage of bash's command substitution. The $(COMMAND) construct allows bash to substitute COMMAND with its output. A simple example:

$ START_TIME=$(date)
$ echo $START_TIME
Fri Mar 12 08:31:31 EST 2010

In the Dropbox example, we're assigning the output of our string of commands-which ultimately outputs the Dropbox path-to the variable DB. From that point forward, we can reference this path as ${DB}

What's This All Good For?

Now we have the local Dropbox folder path. Whoopee. Where can you do anything with that? In other scripts, of course. I actually have several directories in my home directory that are actually stored in my Dropbox folder. This is possible thanks to the magic of symlinks.

A symlink is just a pointer to a file on disk. The ln command is used to create links. Long time Mac users can equate this to a Finder alias. But they're a little different. In essence, a symlink is just another name for a file. Mac OS X provides two kinds of links: hard and symbolic. A hard link effectively is the linked file. An example will make this clear:

$ echo "This is a test" > linktext.txt
$ ln linktext.txt hardlink.txt
$ rm linktext.txt 
$ cat hardlink.txt 
This is a test

What just happened here?

First, a file is created by echo-ing the text "This is a test" into linktext.txt. Then, the ln command is used to create a hard link, named hardlink.txt. Now, the name "hardlink.txt" uses the same inode as linktext.txt, making them the same file. To prove this, in the next step removes the original file. But there's still a pointer to that data on the filesystem: our hardlink, hardlink.txt. To prove this, we can use cat to dump the contents of hardlink.txt. Look at that, it's the same as our original file that we "deleted." Only when we remove hardlink.txt will this directory entry be freed up.

A symbolic link, used much more frequently, is a separate entry on disk that points to the original file. Unlike a hard link, deleting the original file will free the directory entry. This is much more akin to a Finder alias. However, a Finder alias is only understood by the Finder, and not by shell tools. A symlink is much more flexible, being understood by both the Finder and the shell. Let's look at an example:

$ echo "This is a test" > linktext.txt
$ ln -s linktext.txt symlink.txt
$ ls -l
total 16
-rw-r-r- 1 erm admin 15 Mar 12 18:36 linktext.txt
lrwxr-xr-x 1 erm admin 12 Mar 12 18:36 symlink.txt -> linktext.txt
$ cat symlink.txt
This is a test
$ rm linktext.txt 
$ cat symlink.txt 
cat: symlink.txt: No such file or directory

You'll see that unlike hard links, a symbolic link is separate from the original file. In this example, we create a file using echo to redirect text, then create a symbolic link to it. Note that we use the -s switch with ln. By default, ln creates a hard link. The -s switch instructs ln to create a symbolic link. If we try the same delete-and-use-it test that we did with the hard link, we're going to be disappointed. As shown, after removing the original file, the symlink points to nothing.

While it may seem the hard links are better in some respects, symlinks are actually a little more flexible. Since inodes are only unique to a given file system, hard links cannot span across file systems. Another limitation of hard links is that they can only point to files, not directories. A common use of symlinks is to use a common name to point to the latest distribution directory of an application or web directory. For example:

web-site-1.0/
web-site-2.0/
htdocs -> web-site-1.0

In this case, web-site-1.0 is the current site. Once web-site-2.0 is complete and ready to become the main site, all that needs to be done is to point the symlink to the new directory.

Other Ways to Integrate

Now that I have these basics out of the way and I have easy access to my Dropbox folder and a variable with the Dropbox folder path, what do I use it for? First, I have a script that configures a new machine to my liking.

In my Dropbox folder, I store my ~/bin directory. The idea is that I can symlink to it from my home directory. (I've actually changed how I do this-read until the end of this article to read how I now handle this). Inside of ~/bin, I keep a setup script that configures a new machine for my use. One thing that this script relies on: the $DB variable-it needs to know where I've configured the Dropbox folder to be. On (most) any new machine, my workflow is something like this:

1. Create login account

2. Install Dropbox

3. Run ${DB}/bin/setup_new.sh - the setup script

What does this setup script do? I'll just generalize here as the script is incredibly specific to the way I work. However, the important thing is that it can bootstrap my environment just from the Dropbox folder.

First, it symlinks ~/bin folder back to itself. Since we already know the path, this is pretty easy:

ln -s ${DB}/bin ${HOME}/bin

A nicer way to handle this involves some logic and error checking:

#!/bin/bash
# Setup links to bin folder
ERROR=0
if [ -d ${HOME}/bin ]; then
  mv ${HOME}/bin ${HOME}/bin.old
  if [ $? != 0 ]; then
    echo "ERROR: Could not move current ~/bin directory"
    ERROR=1
  fi
fi
if [ -f ${HOME}/bin ]; then
  echo "ERROR: ~/bin already exists - not touching"
  ERROR=1
fi
if [[ $ERROR == 0 ]]; then
  echo "Linking ${HOME}/bin -> ${DB}/bin"
  ln -s ${DB}/bin ${HOME}/bin
fi

Conditional statements will be looked at in more detail in a future column.

The second thing my setup_new.sh script does is to call another script that runs several defaults commands that tweak things just the way I like them. (Yes, I like seeing all files in the Finder, and no, I do not want a warning when I empty the trash). I keep it in s separate script just because I like the modularity and possibility of easily running it without needing to run the entire setup_main.sh script.

Summary and Epilogue

This article demonstrates one way to integrate your shell experience with a perhaps not-so-obvious GUI element. In this case, once your shell knows where the Dropbox folder is, it can perform any manner of syncing action. Which reminds me: I said I'd talk a little bit about how I'm doing things differently now.

I did start off with the same system that I mention here-just symlinking files and folders over to certain locations in my Dropbox folder. In fact, I still do that with certain files and folders, but have begun a hybrid strategy. For my ~/bin and ~/dev folders, I just store my git repository for each on Dropbox. This way, the new machine setup scrip can just check out bin and dev into the new home folder. Any changes in ~/bin and ~/dev can get checked in when ready. Those changes will then be staged on Dropbox, ready for checkout by any other of my Dropbox clients.

If that sounds a little convoluted, well, it works really well for certain workflows, and not so much for others. That's why I have a hybrid approach. However, even files and folders that are symlinked directly into Dropbox are kept under version control (git).

Media of the month: "User Interface Design for Programmers" by Joel Spolsky (http://apress.com/book/view/1893115941). This is a bit of an oldie, but still a goodie. This book is a great read to get you outside of the tech mindset to help you design applications so they have an interface that humans can use.

See you next month with more back-to-the-shell topics.


Ed Marczak is the Executive Editor of MacTech Magazine. He has written the Mac in the Shell column since 2004.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Dropbox 193.4.5594 - Cloud backup and sy...
Dropbox is a file hosting service that provides cloud storage, file synchronization, personal cloud, and client software. It is a modern workspace that allows you to get to all of your files, manage... Read more
Google Chrome 122.0.6261.57 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
Skype 8.113.0.210 - Voice-over-internet...
Skype is a telecommunications app that provides HD video calls, instant messaging, calling to any phone number or landline, and Skype for Business for productive cooperation on the projects. This... Read more
Tor Browser 13.0.10 - Anonymize Web brow...
Using Tor Browser you can protect yourself against tracking, surveillance, and censorship. Tor was originally designed, implemented, and deployed as a third-generation onion-routing project of the U.... Read more
Deeper 3.0.4 - Enable hidden features in...
Deeper is a personalization utility for macOS which allows you to enable and disable the hidden functions of the Finder, Dock, QuickTime, Safari, iTunes, login window, Spotlight, and many of Apple's... Read more
OnyX 4.5.5 - Maintenance and optimizatio...
OnyX is a multifunction utility that you can use to verify the startup disk and the structure of its system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the... Read more
Hopper Disassembler 5.14.1 - Binary disa...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
WhatsApp 24.3.78 - Desktop client for Wh...
WhatsApp is the desktop client for WhatsApp Messenger, a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. WhatsApp Messenger is available for... Read more
War Thunder 2.33.0.135 - Multiplayer war...
In War Thunder, aircraft, attack helicopters, ground forces and naval ships collaborate in realistic competitive battles. You can choose from over 1,500 vehicles and an extensive variety of combat... Read more
Iridient Developer 4.2 - Powerful image-...
Iridient Developer (was RAW Developer) is a powerful image-conversion application designed specifically for OS X. Iridient Developer gives advanced photographers total control over every aspect of... Read more

Latest Forum Discussions

See All

Gorgeous Tactical Puzzle Game ‘Howl’ is...
Following its release on PC and Nintendo Switch this past November, and it’s arrival on Xbox and PlayStation back in January, publisher Astragon Entertainment and developer Mi’pu’mi Games are now bringing their super stylish tactical puzzler Howl to... | Read more »
Best iPhone Game Updates: ‘Shoot the Moo...
Hello everyone, and welcome to the week! It’s time once again for our look back at the noteworthy updates of the last seven days. It feels like a bit of a dry spell this week, at least in terms of really interesting updates. I mean, I found some... | Read more »
Celebrate Phobies spooky second annivers...
Get ready to have that classic song stuck in your head, as Phobies celebrates its second anniversary with the release of its latest update; Birthday Bash, Monster Mash. Starting March 5th and lasting for four weeks, it will be a month of... | Read more »
‘Dissidia Final Fantasy Opera Omnia’ Sto...
Square Enix finally shut down Dissidia Final Fantasy Opera Omnia (Free) on iOS and Android last week following the end of service announcement back in November last year. Following the game shutting down, Square Enix | Read more »
‘Monster Hunter Now’ Is Celebrating the...
Niantic and Capcom have begun celebrating the 20th anniversary of Capcom’s best franchise from today inside Monster Hunter Now (Free) on iOS and Android for a limited time. | Read more »
New ‘Warframe Mobile’ Update Adds 60fps...
Warframe Mobile (Free) launched worldwide on iOS just under two weeks ago. I’ve been playing it for review across multiple iOS devices, but have also been picking it up on Steam Deck and Switch to compare. Right from launch, I was impressed with... | Read more »
Passionate About Fidget Toys – The Touch...
In this week’s episode of The TouchArcade Show we kick things off with some passionate discussion about… fidget toys? For some reason? We quickly change gears to talk about the card-based rogulike Balatro, which we’ve both been playing and enjoying... | Read more »
TouchArcade Game of the Week: ‘Flying Ta...
For me Hexage is one of those developers that harkens back to the early days of the App Store and really the beginnings of iPhone gaming. I have spent many collective hours playing the likes of Totemo, Radiant, Radiant Defense, EVAC, Reaper… the... | Read more »
SwitchArcade Round-Up: ‘Ufouria 2: The S...
Hello gentle readers, and welcome to the SwitchArcade Round-Up for March 1st, 2024. In today’s article, we’re looking at the remaining releases of the week. There are a few really good ones today, but the bin bunch certainly isn’t going home hungry... | Read more »
Steam Deck Weekly: Reviews of PowerWash...
Welcome to the first Steam Deck Weekly of March and this week’s edition is bigger than usual. I was a bit unwell last week and had to push some reviews to this week. Alongside that, there have been many notable announcements, releases, and new Steam... | Read more »

Price Scanner via MacPrices.net

Apple discontinues 15-inch M2 MacBook Airs, d...
With today’s introduction of new M3-powered 15″ MacBook Airs, Apple has dropped prices on clearance, Certified Refurbished, 15″ M2 MacBook Airs to a new low of $1019. These are the cheapest 15″... Read more
Price Drop! 13-inch M2 MacBook Airs at Apple...
Apple has dropped prices on Certified Refurbished 13″ M2 MacBook Airs to a new low of $849. These are the cheapest M2-powered MacBooks for sale at Apple. Apple’s one-year warranty is included,... Read more
Apple finally discontinues the 13-inch M1 Mac...
With the introduction of M3-powered 13″ MacBook Airs today, Apple has dropped prices on clearance 13″ M1 MacBook Airs, Certified Refurbished, to $759 for 8-Core CPU/7-Core GPU/256GB models and $929... Read more
Updated Apple iPad Price Trackers
Our Apple award-winning iPad Price Trackers are the best place to find the latest information on iPad sales and deals. We track prices from 20+ Apple retailers, including Apple, Amazon, Best Buy,... Read more
Updated Apple MacBook Price Trackers
Our Apple award-winning MacBook Price Trackers are continually updated with the latest information on prices, bundles, and availability for 16″, 14″, and (recently-discontinued) 13″ MacBook Pros... Read more
Mac Studios with Apple M2 Max and M2 Ultra CP...
B&H Photo has the standard-configuration Mac Studio model with Apple’s M2 Ultra CPU in stock today and on sale for $300 off MSRP, now $3699 (24-Core CPU and 64GB RAM/1TB SSD). B&H Photo has... Read more
Extended: Switch to Verizon and get the Apple...
Verizon has the iPhone 15 on sale for $0 per month when you add a new line if service. Discount is applied to your account monthly over a 36 month term and is valid for the 128GB model. For the first... Read more
Select 16-inch M3 Pro and M3 Max MacBook Pros...
B&H Photo has select 16-inch M3 Pro and M3 Max MacBook Pros on sale for $250 off MSRP. Their prices are the lowest currently available for these configurations. Free 1-2 day shipping is available... Read more
27-inch Apple Studio Displays on sale for $10...
B&H Photo has 27″ Apple Studio Displays on sale for $100 off MSRP today. Free 1-2 day shipping is available to most US addresses: – Studio Display (Standard glass, Tilt stand): $1499 $100 off... Read more
iPad Airs return to their all-time lowest pri...
Best Buy has 10.9″ M1 WiFi iPad Airs on record-low sale prices again for $150 off Apple’s MSRP, starting at $449. Sale prices for online orders only, in-store price may vary. Order online, and choose... Read more

Jobs Board

Teller Part Time *Apple* Valley MN *Apple*...
…is not eligible for Visa sponsorship **Posting Location:** + 15574 Pilot Knod Road Apple Valley, MN 55124 @RWF22 **Posting End Date:** Job posting may come down Read more
*Apple* End User Support Specialist - North...
…that they are performed. + Responsible for support of all College owned Apple computers, mobile ios devices, and peripherals, and for diagnosing and resolving Read more
Omnichannel Associate - *Apple* Blossom Mal...
Omnichannel Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Teller Part Time *Apple* Valley MN *Apple*...
…is not eligible for Visa sponsorship **Posting Location:** + 15574 Pilot Knod Road Apple Valley, MN 55124 @RWF22 **Posting End Date:** Job posting may come down Read more
Nurse Anesthetist - *Apple* Hill Surgery Ce...
Nurse Anesthetist - Apple Hill Surgery Center WellSpan Medical Group, York, PA | Advanced Practice Providers | Certified Registered Nurse Anesthetists | FTE: 1 | Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.