GNU Recutils

Fred and George, Turtles in love

Fred and George, Turtles in love

There are hundreds of cool command line tools that have been made over the years built on the unix philosophy. Plain text is powerful, ubiquitous, and human-centric. It was also the only option for computing for quite a while. It’s no surprise that some of the most sophisticated tools are focused on it.

One such package is GNU Recutils, a set of tools and libraries to access human-editable, plain text databases called recfiles. Using plain text that is primarily human-readable as a database is just frankly cool as hell.

Recutils is a collection of tools, like recins, recdel, and recsel used to manage these recfiles/databases. They allow for all the normal basic relational database operations, typing, auto-incrementing, and even field-level crypto. All of this power is yours with the bonus that your database is a human-readable text file that you can grep/awk/sed freely, and a line-oriented structure makes it perfect for version control systems.

Recfiles

%rec: Book
%mandatory: Title
%type: Location enum loaned home unknown
%doc:
+ A book in my personal collection.

Title: GNU Emacs Manual
Author: Richard M. Stallman
Publisher: FSF
Location: home

Title: The Colour of Magic
Author: Terry Pratchett
Location: loaned

Title: Mio Cid
Author: Anonymous
Location: home

Title: chapters.gnu.org administration guide
Author: Nacho Gonzalez
Author: Jose E. Marchesi
Location: unknown

Title: Yeelong User Manual
Location: home

A recfile begins with an optional structure definition using % prefixes. There’s a lot of power available in this, including the defining of relations between tables, constraints, types, and more. You can use the built-in type definitions or define your own using regular expressions (plain text woo).

Following this header bit, the individual records are listed with a blank line separating entries. Have a look at how amazingly readable the data is!

Here’s a more sophisticated example that shows a relationship in action:

%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

Car service examples courtesy of dbucklin’s gopher post.

Queries & other operations

$ recsel -e "Location = 'loaned'" -P Title books.rec
The Colour of Magic

Querying your recfile database is usually done with recsel (recfile select). You specify the table to query, expressions, fields to return, and the file and the output comes to standard out.

To insert data you use the recins (recfile insert) command:

$ recins -t Task              \
    -f Id -v 10               \
    -f Title  -v "New issue." \
    -f Status -v NEW          \
    TODO.rec

Again it’s a simple syntax. You provide the table to insert into, a list of fields & values (-f & -v, respectively), and the filename. If you prefer, you can use the -r switch to provide the field & value as one string.

How about deleting records? Can you guess the syntax?

$ recdel -c -t Task -e "Status = 'CLOSED'" TODO.rec

Yep, it’s pretty much the same as the select, as one would expect.

What else?

There’s other convenient tools, like the ability to convert to and from CSV formats, alternative output modes that make it work well with awk, password-protected fields, and so on. The package is quite robust and well maintained by Jose E. Marchesi, who can be found in the #recutils room on irc.freenode.net.

The full documentation is seriously impressive. Check it out.

I’ll be adopting it into my tools immediately!

(yes, the offical package image is two gay turtles)