From: dbucklin@sdf.org Date: 2018-10-24 Subject: Using GNU Recutils to Track Car Maintenance History I have an older car that needs regular maintenance. My maintenance history is stored on a pile of crumpled papers in the glovebox. This makes it hard to get a holistic picture of my car's mainte- nance history. It's good to know what you've had done when the service department is making recommendations. There are services like Carfax that will provide a detailed history for a little money, but the value of something like Carfax is to see maintenance records for a used car before you buy it, not to track maintenance on a vehicle you already own. Plus, I already have two years of maintenance data sitting in the glovebox. What information to track? I've created a class diagram to help me think through this. @startuml 'render at plantuml.com/plantuml class Car class Activity class Provider Car: make Car: model Car: year Activity: date Activity: mileage Service: description Provider: name Provider: address Provider: city Provider: state Provider: zip Car *-- Activity Provider *-- Activity Activity *-- Service @enduml So we have a **Car** that represents my Honda, a **Provider** like Jiffy Lube, an **Activity** representing a visit to the shop, and **Service** items that represent specific things that were done to the car, like an oil change. I'm going to change this a bit when I implement it in recutils. * I only have one car, so I'm not going to associate data with a car. * I'm going to merge the Activity and Service objects. There will be some duplication of data, but it will be easier to manage. * I'll be doing all my reporting from the Service type, so that's where I'll store all the foreign keys. Here is my recfile with all the field properties. You could, of course, do much of this in a spreadsheet, sacrificing some flexi- bility. %rec: Service %key: Id %auto: Id %type: Provider rec Provider %type: Mileage int %sort: Mileage %mandatory: Id Date Mileage Description Provider %rec: Provider %key: Id %auto: Id %mandatory: Id Name Now, I've gone through the nominally laborious task of translating my service invoices into recfiles. I had to summarize some of the line items on the invoices. I did this in an editor, but you could also use recins, possibly within a script. %rec: Service %key: Id %auto: Id %type: Provider rec Provider %sort: Mileage Id: 1 Date: 2017-06-12 Mileage: 151140 Description: Tire rotation Provider: 1 Id: 2 Date: 2017-06-12 Mileage: 151140 Description: Replaced thermostat, refilled and bled cooling system Provider: 1 Id: 3 Date: 2017-06-12 Mileage: 151140 Description: Replaced cabin air filter Provider: 1 %rec: Provider %key: Id %auto: Id Id: 1 Name: Honda Dealer Now I can pull a succinct history using recsel. recsel -t Service -pDate,Mileage,Description service.rec to get Date: 2018-09-10 Mileage: Description: Reinstall FR bumper, clips Date: 2017-02-21 Mileage: 148881 Description: Minor inspection Date: 2017-02-27 Mileage: 149003 Description: Oil Change I can limit the data returned using a selection expression. For example, I can have it show only oil changes. recsel -t Service -e 'Description = "Oil Change"' -pDate,Mileage,Description service.rec to get Date: 2017-02-27 Mileage: 149003 Description: Oil Change Date: 2017-10-20 Mileage: 155328 Description: Oil Change Date: 2018-01-03 Mileage: 158262 Description: Oil Change It would be pretty neat to see how many miles had elapsed between oil changes. I think awk would be a good tool for this. First, we need to transform these vertical records into linewise records. There are probably a number of ways to do this. Here's an awk script that does the job. awk '/./ {ln = ln $0 "\t"}; /^$/ {print ln; ln = ""};' You could also do it in sed like this: sed -ne '/./ H;/^$/ {x;s/^\n//;s/\n/\t/g;p};${g;s/^\n//;s/\n/\t/g;p}' One more thing we need to do is strip the field labels from the output of recsel. This is easily done by changing the `-p` option to `-P`. So, to get tabular output, we pipe the output of recsel into awk. recsel -t Service -e 'Description = "Oil Change"' -PDate,Mileage,Description service.rec | awk '/./ {ln = ln $0 "\t"}; /^$/ {print ln; ln = ""};' to get 2017-02-27 149003 Oil Change 2017-10-20 155328 Oil Change 2018-01-03 158262 Oil Change 2018-05-17 162140 Oil Change Now we can do some math with another awk script. This script looks at the mileage on each line, subtracts the mileage from the previ- ous line, and displays the difference at the end of the line. awk '{print $0 "\t" $2-prev; prev = $2}' We can pipe the output of the previous command into this awk script to get 2017-02-27 149003 Oil Change 149003 2017-10-20 155328 Oil Change 6325 2018-01-03 158262 Oil Change 2934 2018-05-17 162140 Oil Change 3878 My guess is I lost a service record for an oil change somewhere during June 2017. I could check my credit card statements during that period to see if I can find a payment to an auto shop. I like to think that I'm diligent about oil changes, but I can see I have some room for improvement. More ideas: * Add an Exhibit Number to each Service record so that you can quickly find the specific paper maintenance record that it came from. * Use a plotting tool like GNUplot or Google Charts to plot mileage or expense over time. * Track maintenance expenses against the market value of the car to help you decide when to replace it. * Print a succinct maintenance history to keep in your glovebox.