jasonwryan.com

Miscellaneous ephemera…

Simple Reminders

Due to a rather embarrassing episode in #archlinux a couple of weeks ago, where I naively shared one of the first bash scripts I had written without first looking back over it1, and had to subsequently endure what felt like the ritual code mocking, but was in fact some helpful pointers as to how I could make the script suck less (a lot less) I have been going through those older scripts and applying the little knowledge that I have picked up in the interim; reappraising the usefulness of the scripts as I go.

One that has proved to be of some utility for many years now is a simple wrapper script I wrote to help manage my finances. Like many useful scripts, it was written quickly and has been in constant use ever since; becoming almost transparent it is so ingrained in my workflow.

The script allows me to manage the lag between when a company emails me an invoice and when the payment is actually due. I find that companies will typically email their invoices to me some weeks in advance, whereupon I will make a mental note and then, unsurprisingly, promptly forget all about it, thereby opening myself up for penalties for late payment. It didn’t take me long (well, in my defence, a lot less time than it took for invoices to become digital) to realise that there was a better way™ - a script.

The at command is purpose built for running aperiodic commands at a later time (whereas cron is for periodic tasks). So, using at(1), once I receive an invoice, I can set a reminder closer to the final payment window, thereby avoiding both the late payment penalty—and the loss of interest were I to pay it on receipt. I just needed a script to make it painless to achieve.

The main function of the script is pretty self-explanatory:

todo
aread() {
  read -p "Time of message? [HH:MM] " attime
  read -p "Date of message? [DD.MM.YY] " atdate
  read -p "Message body? " message

  timexp='^[0-9]{2}:[0-9]{2}'
  datexp='^[0-9]{2}.[0-9]{2}.[0-9]{2}'

  if [[ $attime =~ $timexp && $atdate =~ $datexp ]]; then
     at "$attime" "$atdate" << EOF
     printf '%s\n' "$message" | mutt -s "REMINDER" jasonwryan@gmail.com
EOF
  else
     printf '%s\n' "Incorrectly formatted values, bailing..." && exit 1
  fi
}

Now, an invoice arrives, I open it and fire up a scratchpad, and follow the prompts. A couple of weeks later, the reminder email arrives and I login to my bank account and dispatch payment. You could, of course, have the script trigger some other form of notification, but an email works well for me.

The rest of the script is similarly basic; just some options for listing and reading any queued jobs and some more rudimentary checking. The full script is in my bitbucket repo2.

Update 7/09/14

Not more than a couple of hours after posting this, Florian Pritz pinged me in #archlinux with some great suggestions for improving the script. I particularly liked relying on date(1) handling the input format for the time and date values. He also suggested a readline wrapper called (appropriately enough) rlwrap and a tmpfile to better manage input validation. You can see his full diff of changes. In the end, I adopted the date suggestion but passed on rlwrap. Thanks for the great pointers, Florian.

Notes

  1. In the interests of full disclosure, the most egregious line was myterm=$(echo $TERM) which I would hope I copied blindly from somewhere else, but accept full responsibility for nonetheless.
  2. Don’t poke around too much in there, I still have quite a lot of cleaning up to do…

Creative Commons image by Adelle and Justin on Flickr.

Building from Source

One of the real strengths of Arch is its ability to be customised. Not just in terms of the packages that you choose to install, but how those packages themselves can be patched, altered or otherwise configured to suit your workflow and setup. I have posted previously about, for example, building Vim or hacking PKGBUILDS. What makes all this possible is the wonderful ABS, the Arch Build System.

Essentially a tree of all of the PKGBUILDs (and other necessary files) for the packages in the official repositories, the ABS is the means by which you can easily acquire, compile and install any of the packages on your system:

ABS is made up of a directory tree (the ABS tree) residing under /var/abs. This tree contains many subdirectories, each within a category and each named by their respective package. This tree represents (but does not contain) all official Arch software, retrievable through the SVN system.

Arch Wiki ABS

I have been using ABS since I started running Arch and it has worked well. I wrote a simple script to check for and download updates when required to help simplify the process and have been generally content with that approach. That isn’t to say that elements of this process couldn’t be improved. One of the small niggles is that the ABS only syncs once a day so there is almost always—for me down here in .nz, anyway—at least a full day’s wait between the package hitting the local mirror and the updated ABS version arriving. The other issue is that you download and sync the entire tree…

That all changed when, at the start of this month, one of the Arch developers, Dave Reisner, opened a thread on the Arch boards announcing asp, the Arch Source Package management tool, a git-based alternative for abs1.

Basically a 200-line bash script, asp is an improvement over abs insofar as you get the updated PKGBUILDs immediately; you can choose between just pulling the necessary source files (as per abs), or checking out the package branch so that you can create your own development branch and, for example, keep your patch set in git as well.

You can elect to locate the local git repository in a directory of your choosing by exporting ASPROOT, there are Tab completion scripts for bash and zsh and a succinct man page. Overall, for a utility that is only three weeks old, asp is already fulfilling the function of a drop-in replacement; a faster, more flexible tool for building Arch packages from source.

With thy sharp teeth this knot intrinsicate
Of life at once untie…

Antony and Cleopatra V.ii

Notes

  1. The package, not the entire build system…

Creative Commons image, Red Lego Brick by Brian Dill on Flickr.

pass{,word} manager

After posting last week about KeePassC as a password manager, a couple of people immediately commented about a utility billed as “the standard Unix password manager.” This is definitely one of the reasons I continue to write up my experiences with free and open source software: as soon as you think that you have learned something, someone will either offer a correction or encourage you to explore something else that is similar, related or interesting for some other tangential reason.

So, I was off down that path… Called simply pass, it is a 600 line bash script that uses GPG encryption and some other standard tools and scripts to organize and manage your password files. I had never heard of it but, based on Cayetano and Bigby’s recommendations, I thought it would be worth a look.

On of the reasons that I had not come across it before was that, after using KeePassX for so long, I had assumed that I would need to continue to use that database format; so when I was looking for an alternative, KeePassC was a natural fit (and a fine application). The question of migrating my data hadn’t even occurred to me…

It turns out that the migration process to pass is extraordinarily well catered for: there are 10 migration scripts for a range of different formats, including keepassx2pass.py, which takes the exported XML KeePassX database file and creates your pass files,ordered by the schema you had used in that application. You just need to make sure you amend the shebang to python2 before running the script, otherwise it will fail with an unhelpful error message.

After using KeePassX to dump my database, before I could use the script to create my pass directories, I had to export the PASSWORD_STORE_DIR environment variable to place the top level pass directory in an alternate location. This way, instead of initializing a git repository, I could have the store synced by Syncthing. The git idea is a good one, but I’m not particularly interested in version controlling these directories, and I have no intention, encrypted or not, of pushing them to someone else’s server.

That constitutes the basic setup. It took a grand total of five minutes. The real strength of pass, however, is in its integration with two other fantastic tools: keychain and dmenu. Together with pass, these constitute a secure, convenient and effortless workflow for managing your passwords. With your GPG key loaded into keychain, you are only prompted for your master passphrase once1 and with Chris Down’s excellent passmenu script, you can use dmenu to sort through your password files, Tab complete the one you are looking for and have it copied to your clipboard with a couple of keystrokes.

After using Chris’ script for a couple of days, I made a few alterations to suit my setup: removed the xdotool stuff (as I don’t need it), included dmenu formatting options to match my dwm statusbar and, most significantly, changed the way that the files are printed in dmenu to remove the visual clutter of the parent directories, ie., print archwiki as opposed to internet/archwiki:

dpass
#!/usr/bin/env bash
# based on: https://github.com/cdown/passmenu

shopt -s nullglob globstar

nb='#121212'
nf='#696969'
sb='#121212'
sf='#914E89'
font="Dejavu Sans Mono:medium:size=7.5"
dmenucmd=( dmenu -i -fn "$font" -nb "$nb" -nf "$nf" -sb "$sb" -sf "$sf" )

prefix=${PASSWORD_STORE_DIR:-~/.password-store}
files=( "$prefix"/**/*.gpg )
files=( "${files[@]#"$prefix"/}" )
files=( "${files[@]%.gpg}" )
fbase=( "${files[@]##*/}" )

word=$(printf '%s\n' "${fbase[@]}" | "${dmenucmd[@]}" "$@")

if [[ -n $word ]]; then
  for match in "${files[@]}"; do  
    if [[ $word == ${match#*/} ]]; then
      /usr/bin/pass show -c "$match" 2>/dev/null
    fi  
  done
fi

It does introduce some more complexity into the script, but it makes it a lot easier for me to identify the desired password when reading it in dmenu.

Now, when I need a to enter a password, I hit my dmenu hotkey, type dpass Enter and the first couple of letters of the desired password filename, TabEnter and the password is loaded and ready to go. There are also completion scripts for the main shells, and even one for fish2 for the iconoclasts…

While I have no complaints at all with KeePassC, I have found this pass setup to be a lot less intrusive to use, it seamlessly integrates with my workflow, and the passwords themselves are much simpler to manage. Short of someone else popping up in the comments with another compelling proposition, I’m content with the way this has worked out. Many thanks to Cayetano Santos and Bigby James for the push.

Notes

  1. There is a very annoying bug open for keychain that means if, as I do, you start keychain from your $HOME/.profile or $ZDOTDIR/.zprofile you will need to enter the same passphrase to unlock a sub-key before you can use pass (the same thing applies to Mutt). This gets really ugly if you attempt to use dmenu before unlocking your key…
  2. Finally, a command line shell for the 90s… Indeed.

Creative Commons image by Intel Free Press on Flickr.