hpr_transcripts/hpr3386.txt

Episode: 3386
Title: HPR3386: What's for dinner?
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr3386/hpr3386.mp3
Transcribed: 2025-10-24 22:30:10

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This is Hacker Public Radio Episode 3386 for Mundy, the 26th of July 2021.
Tid's show is entitled, What's For Dinner? It is hosted by Dave Morris and is about 22 minutes long
and carries an explicit flag. The summary is some scripts and a database for randomly choosing
which meal to cook. This episode of HPR is brought to you by an honest host.com.
Get 15% discount on all shared hosting with the offer code HPR15. That's HPR15.
Better web hosting that's honest and fair at An HonestHost.com.
Hi everybody. Welcome to Hacker Public Radio. This is Dave Morris. I want to talk today
about a bit of software that I've written and I'm entitled to show what's for dinner
and about some scripts and a database that I've written for randomly choosing which meal
to cook on a particular time. Now I have two grown up children. I live on my own these days
but every week, pretty much every week, they come over for dinner. I cooked dinner for them.
What I normally do is to prepare something for the Wednesday and make enough of it so we can
also eat it on the Thursday and that's every week when they're around and always around. I normally
do the cooking as I say but we're gradually evolving to think where some of the meals in the list
managed by one of the kids. Anyway in 2019, I thought it would be useful if I had some sort of a
random chooser to decide what we should do for next week because before that I think we'd just
been saying what are you fancy next week and they'd say oh could you do blah blah blah and I would
do that but we'd sometimes they'd go oh I don't know, you choose. So I like to solve these
such problems with a bit of software. Initially I wrote a bash script I called it choose meal
and it used a simple CSV file of meal names and the date last eaten so we could avoid choosing
the same one too often. This was not very good. It showed its weaknesses quite quickly. It wasn't
long before choose meal got rewritten in Perl which is the scripting language I prefer to use
still these days. Languages go in and out fashion Perl was fashionable when I was working and I wrote
a lot stuff in it. I've not really had a great desire to move on to other scripting languages.
Perl is not fashionable anymore but it does the job pretty well. I do rather like the way it does
it. It's stuck in a rut probably but there you go. Anyway this time I decided to use a database
and I chose sqlite to create it and the database is pretty simple it just contains two tables.
One for the meals themselves just a simple description. I'll come on to what I store in seven
a minute and there's another table for the history of the choices made. It was partly because
that was a way of avoiding choosing the same one too often but it's also quite nice to produce
historical reports I thought. Now in 2019 the design of this system was very specific to our
needs one choice per week on a Wednesday so it was not something like I could hand over to anybody
else which seemed like a bad idea. I mentioned this to Ken when we were all coming 2019 he said oh
that sounds interesting and I thought ah yeah but it's tailored for us not for anybody else.
So in late 2020 during the lockdown and all that stuff the covid era and in early 2021
I redesigned this system and I'm going to talk a bit about what I did in the redesign in this show
and in May 2021 a more general design was added to the public GitLab repository that I'd set up
and I began preparing to make this show. Just taking a while I'm not very quick at doing these
things. I'd never intended this system to hold recipes as such partly because I have a collection
of recipes that I've constructed from various sources online things recipe books and so on
fiddle around with them and so on. I've typed them up in LibreOffice and then I printed them out
put them in a folder and sometimes I do things which are multi-component like when we have curry
I pick things components for that so there's no hard and fast recipe menu for that particular one.
So it doesn't seem appropriate to hold the recipes in the database or even references to them
but the more I think about it the more it might be something that I would like to do in the future
but don't hold your breath. So brief chat about the database itself. In case you're interested
the overall design developed is coming on and what I hold for each meal is a name a unique name
because it's a key. There's a figure which is the delay between occurrences of the meal so if I
a lot of them we've just got 28 so every every 28 days it can come up but some of them really
popular and I make it so they could come up in like a couple of weeks. I also keep a record of when
the meal was last eaten so it's easier to work out whether we're in the delay period from last
time. I can enable a disable a meal sometimes we disable them when we've got a bit fed up with them
or maybe they're seasonal. They also store notes about the meal just sort of general hints to
myself to don't forget to buy whatever it could you could you could make this more fancy you could
make it give you a shopping list or something or components of a shopping list or something like that
but I'm not really bothered about doing that. I can manage perfectly well as it is it's going to
it's probably domain it's sitting there on a get repository so if you if it sounds of any interest
to you you're perfectly welcome to fork it and mess around do your own thing the meal history
stuff is just a thing that links back to the meal table so it's got an ID in there meal ID
then the date of entry of the log it's it's a log table effectively then the minimum number of days
at the time the meal was chosen because I might be fiddling with that number so it's useful to keep
I think anyway the date this meal was previously eaten is there and date that it was last eaten
so there's a way of tracking back through the history of a given meal to see the dates on which it
was eaten and the the number of days between it all that sort of stuff some of which I use but it's
just more more me messing around or anything else I quite enjoyed playing with databases the history
table is written automatically using a trigger in the database so when something changes in the
the main meal information table then the the log is written so I've got two scripts that work with
this system one is called choose meal just like the original one was and it makes a random choice
from the database there's also manage meal which is something I wrote later which allows the
management of meal entries in the database and can do all the report generation and that sort of
stuff they both purl scripts they contain embedded documentation if you call the script with the
option hyphen help then it will give you a brief summary of the options and I'd use them you
also get more in-depth information by using the option hyphen man page where it will print the
entire documentation so they're all on the git repository on git lab and I've linked that in the
notes the idea was that if you wanted to install this you could clone the repository and maybe
keep a copy of the repo locally and then make another copy of it rather than running a
different thing out of the repo copy repository copy put it in a different directory up to you
if you want to do it there's an installation section later on in the notes that I'll talk about
briefly before you can use this thing you have to have a database and you need to put some meals
in it the number of meals you add to it depends on how often you plan to choose stuff what delay
you set and so forth so it's entirely possible for you to set things up so there's not enough or
the time between them is too long so that the chooser can't actually choose anything so
there's no I haven't come up with a simple way of determining that I suppose it would be possible
but it's a factor that you'd need to consider if you were working with this the database can easily
be populated with this managed meals script using the hyphen add option you can add meals in a disabled
state and then enable them later which I tend to do because I make them disabled while I'm maybe
experimenting with the the best recipe and switch them on so they become eligible for choice once
I'm happy with the recipe there's a summary option which lets you see all of what's in the database
you can list a given meal with a hyphen list option and you can add hyphen full to that
to get the notes as well now on the repository I've tried to write some pretty comprehensive
instructions and I'm not going to duplicate them here really because what's the point you can
go and read them there I just wanted to give you the flavor of it you might be saying well
this is of no interest to me whatsoever and you know maybe you're going to hit the delete button any
minute but in case you find it interesting you can go and look at the repository and decide whether
you want to go further with it so the choos meal script does the random choosing what I normally do
each week is to run choose meal with the hyphen verbose option and then and then put on the hyphen
dry hyphen run option that means it will have a go it'll make a choice but it won't save it
and it'll also tell you what it's choosing from because not all the meals in the database will be
eligible at any given time because of the delay number usually I get like four or five options that
it says are going to choose from and then it makes a choice so by default when you run it it makes
a choice for the current date but you can you can make it choose a future date by using the hyphen
date equals and then date using the ISO 8601 format is preferred I did try and write this so it could
handle different date formats but I haven't quite got it to the point where it will it will handle
as many as I expected I'd be able to to deal with the script itself can't be given a date like
next Friday but if you use a command substitution as the date and you use the date command
where you specify next Friday returning an ISO 8601 date as an example in the notes then that
that does the job and it makes a pretty good turn and he's fairly easy way you've got a type of
bit more brackets and dollars and stuff but it's it's okay then there's an alternative which is
if you want it you you want it to just choose for the same day each week as I do and that should
be the default but if you want to choose something special you could still override that then there's
a configuration file which specifies what your default date is I mentioned briefly what the
configuration file looks like it's a jam or file it's called dot choose meal dot yml but you can
provide other names if you want to to pursue it somewhere else I won't read out what I've written
here which tells you that how to lay out the file but basically you're declaring which which is your
preferred weekday if you're letting it make its own choice of day and in this case the name of the
weekday is Wednesday and the language used is English you can't actually write another language
just because the library underneath can handle that so yml is a bit of an odd thing to use it's
pretty simple to to write but it's a bit fussy about spaces and stuff think I've in the repo
quite an example that you could just edit your own desires if you wish I've also mentioned that
the file is similar in structure to the json if that's something you know better and I've shown
what it would look like in json form there's an online tool various tools that will convert from
yml to json so let's talk about installation if you wanted to install this it's a bit involved but
it's often the case with scripts and libraries and stuff I tested this on Raspberry Pi which didn't
have in any of the things that I have on my desktop machine so I found in order to get this to work
I needed to install various things I needed to install git the thing for managing repositories
sqlite 3 which is SQLite and pearl dock pearl hyphen dock which is the which contains tools for
displaying documentation in pearl files so I explain how you could get the repository and I'd
prefer to put these sorts of things in a directory called git with the capital g if you make the
directory go to it and then run git clone then it will create a directory underneath there with
the contents of the repository so and if you want to update it at a later stage because it's
under development this thing you can go to that directory whether where you just put the repository
and type git space pull to get the latest updates now I decided to put all of the stuff from the
all the yeah all the all everything from this repository into another directory which I call weekly
underscore menus with the capital W and I've got an example of an rsync command I think rsync
is built into you're going to need to install it if you're on a Raspberry Pi which grabs everything
out of the repository apart from files under the directory dot g it and buns them into that directory
so you could run that after if you wanted to do it that way you could run that after you did the
git pull you wanted to now there's quite a lot of pearl modules that this the script used
10 maybe actually count them the way you get them with pearl is not
dissimilar from the way that you get Python libraries with pip but with pearl you you're probably
best to use a thing called cpan m which is short for cpan minus cpan is a pearl thing
comprehensive pearl archive network so you can you can do what I've suggested here which is to run
use curl to download the cpan minus tool and you need to use a pseudo option to install it
you might be asked for a password but on the pie I was using the default user lowercase pie
I wasn't prompted so it's pretty quick to download and install so then you need to
cd to the weekly menus directory and then you can use a file called modules underscore needed
and feed that to the cpan m thing but there's an example of how you do that and I won't go into
detail with it here since it's pretty pretty straightforward and it's explained here in the notes
and you can actually rerun this at later stage and it will update any modules that won't need it
so having done that makes you it can take a while by the way there's 77 modules that got installed
in total because there's some of the modules I'm using have dependencies so on on a system that
doesn't have any pearls stuff on it you are going to have to download a fair bit but if you run
it again a later date to update things it will take far less time because all the dependencies
should have been satisfied so the final step in installation is to create the database and to do
that there's an example here running sqlite3 command making a file called meals.db which is the default
database name there's a file called meals underscore db.sql in the repository and that contains all
the commands needed to build the database then you can go in use the managed meal tool to add meals to
it and I've got an example shown here so how you do that if you're in the business of adding
the meal haggis neeps and tatties to your database I suggest that if you're into using this you take
regular backup of the database and I've included a script that will do this
and I run this every day at 21 55 and the reason I choose that time you could use any time you like
is that there is a master backup that runs at 10 o'clock at night every day so this makes sure
that the backups of the database get backed up to the master backup the script simply runs
sqlite in its backup mode and there's the the data in a file called meals underscore db followed by
a date and timestamp it also compresses it using bzip2 I mentioned here how you could
restore it if you if you happen to have lost your database for whatever reason you could restore
it from from a backup these cron script will actually delete old backups it's got a 140 day limit at
the moment but I'll let you fiddle around to that as the mood takes you it's it's not the best
way of making the backup least you've got something to fall back on I write it to a back to a direct
subject it called backups and it's it's good I have I have on occasion screwed up the database but
that's because of development and then I've been able to pull back breathe version from the from
this file but as I said I have a thing that does daily backups to an external disk which is a bit
better hopefully you're doing something with regard to backups that will handle this so what's
next for this system it we're going to do in the else with it well if I get any feedback I might
look at doing some other stuff there was a brief to do list here as a possible things
I might add to it I might add the ability to include or link to recipes so if you had a preferred
way of cooking hackies neeps and patties then it would be good to point to a recipe for that
and I also might just do some general tidying of the of the code there are a few issues that
I spotted as I was preparing this show nothing very very exciting so finch off with are there
some links I'm appointed at pearl five just in case you don't you do not have to speed with
what pearl does these days pearl five is still being developed at quite quite rapid rate there was
a version of pearl called pearl six that came out and it's totally different from the original
pearl pearl five so it got renamed as racco and and that seems to be coming along quite nicely
it's not going to be as popular as python and um another other scripting languages but it it has
very interesting features to it so it's it's worth being aware of it there's a pearl seven
in the making which will be the next updated pearl five obviously because they're to skip six
and if you don't know what ssqlite is then check that out because it's a really clever way of making
a small as it says here it's fast self-contained high reliability four featured sql database engine
you just make one file in which you can put a four pretty sophisticated database for three which
can do sort of things that a lot of the big expensive ones can do not all of the things that they
can do but but quite a lot and it's pretty easy to use from all sorts of languages and you probably
got it in in your setup somewhere it sits behind things like music players like it's on probably
on if you've got an android phone it's probably in there behind something or other because it's just
so easy to make a little database to to manage stuff with sqlite and i've also linked here to the
Git library book for weekly menus so i hope you found that at least mildly interesting and you
might indeed go and look further at this thing and and adopt it and if you do let me know okay then
bye bye
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