How I started programming

Sunday, 12 March 2017

I've written parts of this story in the past, but never in one place and never in much detail. So why not now?

In 1982 my family moved house, so one morning I went to school and at lunch-time I had to walk home to a completely different house.

We moved sometime towards the end of the year, and ended up spending lots of money replacing the windows of the new place. For people in York I was born in Farrar Street, Y010 3BY, and we moved to a place on Thief Lane, YO1 3HS. Being named as it was I "ironically" stole at least two street-signs and hung them on my bedroom wall. I suspect my parents were disappointed.

Anyway the net result of this relocation, and the extra repairs meant that my sisters and I had a joint Christmas present that year, a ZX Spectrum 48k.

I tried to find pictures of what we received but unfortunately the web doesn't remember the precise bundle. All together though we received:

I know we also received Horace and the Spiders, and I have vague memories of some other things being included, including a Space Invaders clone. No doubt my parents bought them separately.

Highlights of my Spectrum-gaming memories include R-Type, Strider, and the various "Dizzy" games. Some of the latter I remember very fondly.

Unfortunately this Christmas was pretty underwhelming. We unpacked the machine, we cabled it up to the family TV-set - we only had the one, after all - and then proceeded to be very disappointed when nothing we did resulted in a successful game! It turns out our cassette-deck was not good enough. Being back in the 80s the shops were closed over Christmas, and my memory is that it was around January before we received a working tape-player/recorder, such that we could load games.

Happily the computer came with manuals. I read one, skipping words and terms I didn't understand. I then read the other, which was the spiral-bound orange book. It contained enough examples and decent wording that I learned to write code in BASIC. Not bad for an 11/12 year old.

Later I discovered that my local library contained "computer books". These were colourful books that promised "The Mystery of Silver Mounter", or "Write your own ADVENTURE PROGRAMS". But were largely dry books that contained nothing but multi-page listings of BASIC programs to type in. Often with adjustments that had to be made for your own computer-flavour (BASIC varying between different systems).

If you want to recapture the magic scroll to the foot of this Osbourne page and you can download them!

Later I taught myself Z80 Assembly Language, partly via the Spectrum manual and partly via such books as these two (which I still own 30ish years later):

  • Understanding your Spectrum, Basic & Machine Code Programming.
    • by Dr Ian Logan
  • An introduction to Z80 Machine Code.
    • R.A & J.W Penfold

Pretty much the only reason I continued down this path is because I wanted infinite/extra lives in the few games I owned. (Which were largely pirated via the schoolboy network of parents with cassette-copiers.)

Eventually I got some of my l33t POKES printed in magazines, and received free badges from the magazines of the day such as Your Sinclair & Sinclair User. For example I was "Hacker of the Month" in the Your Sinclair issue 67 , Page 32, apparently because I "asked so nicely in my letter".

Terrible scan is terrible:

Anyway that takes me from 1980ish to 1984. The only computer I ever touched was a Spectrum. Friends had other things, and there were Sega consoles, but I have no memories of them. Suffice it to say that later when I first saw a PC (complete with Hercules graphics, hard drives, and similar sourcery, running GEM IIRC) I was pleased that Intel assembly was "similar" to Z80 assembly - and now I know the reason why.

Some time in the future I might document how I got my first computer job. It is hillarious. As was my naivete.



Rotating passwords

Friday, 24 February 2017

Like many people I use a password-manage to record logins to websites. I previously used a tool called pwsafe, but these days I switched to using pass.

Although I don't like the fact the meta-data is exposed the tool is very useful, and its integration with git is both simple and reliable.

Reading about the security issue that recently affected cloudflare made me consider rotating some passwords. Using git I figured I could look at the last update-time of my passwords. Indeed that was pretty simple:

git ls-tree -r --name-only HEAD | while read filename; do
  echo "$(git log -1 --format="%ad" -- $filename) $filename"

Of course that's not quite enough because we want it sorted, and to do that using the seconds-since-epoch is neater. All together I wrote this:

# Show password age - should be useful for rotation - we first of all
# format the timestamp of every *.gpg file, as both unix+relative time,
# then we sort, and finally we output that sorted data - but we skip
# the first field which is the unix-epoch time.
( git ls-tree -r --name-only HEAD | grep '\.gpg$' | while read filename; do \
      echo "$(git log -1 --format="%at %ar" -- $filename) $filename" ; done ) \
        | sort | awk '{for (i=2; i<NF; i++) printf $i " "; print $NF}'

Not the cleanest script I've ever hacked together, but the output is nice:

 steve@ssh ~ $ cd ~/Repos/personal/pass/
 steve@ssh ~/Repos/personal/pass $ ./password-age | head -n 5
 1 year, 10 months ago GPG/root@localhost.gpg
 1 year, 10 months ago GPG/
 1 year, 10 months ago GPG/
 1 year, 10 months ago Git/
 1 year, 10 months ago Git/

Now I need to pick the sites that are more than a year old and rotate credentials. Or delete accounts, as appropriate.



Apologies for the blog-churn.

Sunday, 19 February 2017

I've been tweaking my blog a little over the past few days, getting ready for a new release of the chronicle blog compiler (github).

During the course of that I rewrote all the posts to have 100% lower-case file-paths. Redirection-pages have been auto-generated for each page which was previously mixed-case, but unfortunately that will have meant that the RSS feed updated unnecessarily:

  • If it used to contain:
  • It would have been updated to contain

That triggered a lot of spamming, as the URLs would have shown up as being new/unread/distinct.



Old packages are interesting.

Thursday, 9 February 2017

Recently Vincent Bernat wrote about writing his own simple terminal, using vte. That was a fun read, as the sample code built really easily and was functional.

At the end of his post he said :

evilvte is quite customizable and can be lightweight. Consider it as a first alternative. Honestly, I don’t remember why I didn’t pick it.

That set me off looking at evilvte, and it was one of those rare projects which seems to be pretty stable, and also hasn't changed in any recent release of Debian GNU/Linux:

  • lenny had 0.4.3-1.
  • etch had nothing.
  • squeeze had 0.4.6-1.
  • wheezy has release 0.5.1-1.
  • jessie has release 0.5.1-1.
  • stretch has release 0.5.1-1.
  • sid has release 0.5.1-1.

I wonder if it would be possible to easily generate a list of packages which have the same revision in multiple distributions? Anyway I had a look at the source, and unfortunately spotted that it didn't entirely handle clicking on hyperlinks terribly well. Clicking on a link would pretty much run:

 firefox '%s'

That meant there was an obvious security problem.

It is a great terminal though, and it just goes to show how short, simple, and readable such things can be. I enjoyed looking at the source, and furthermore enjoyed using it. Unfortunately due to a dependency issue it looks like this package will be removed from stretch.



I've built a product, not a project

Thursday, 2 February 2017

The past few days I've been doing more arduino-work. In between dying of sleep-exhaustion.

One thing that always annoyed me was that I had to hard-code my WiFi credentials in my projects, with code like this:

// Connect to the SCOTLAND network
WiFi.begin("SCOTLAND", "highlander1");

// Attempt to connect - TODO: Timeout on failure
while (WiFi.status() != WL_CONNECTED)

// Now we're connected show the local IP address.
lcd.print("WiFi connected  ");

Whilst looking at another project I found a great solution though. There is a library called WiFiManager which behaves perfectly:

  • If you've stored connection details it will connect to the local WiFI network using those, automatically.
  • If you've not saved previous connection details it will instead configure the device to work as an Access Point
    • You can then connect to that access point and see a list of local WiFi networks.
    • Choose the appropriate one from the list, enter your password, and these details are saved for the future.
    • The device will then reset, join the network via your saved choices and acquire an IP via DHCP as you'd expect.

The code for this is beautifully simple:

// Connect to WiFI with saved credentials, if any.
// Otherwise work as an access-point, named TRAM-TIMES, and
// let the user fill out their details.
WiFiManager wifiManager;

This means my current project, which continues to revolve around tram-times, is so very much more user-friendly. It is a product you could package and take to a friends house, not a project you have to recompile to tweak.

For that reason, user-niceness, I reworked the on-board HTTP status-page to use bootstrap, be themed, and look nicer. Other than being housed in a horrid case the project actually looks like a product. Not one I'd buy, but neither one I'm ashamed of sharing.

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So I've been playing with hardware

Saturday, 28 January 2017

At the end of December I decided I was going to do hardware "things", and so far that has worked out pretty well.

One of the reasons I decided to play with Arduinos is that I assumed I could avoid all forms of soldering. I've done soldering often enough to know I can manage it, but not quite often enough that I feel comfortable doing so.

Unfortunately soldering has become a part of my life once again, as too many of the things I've been playing with have required pins soldering to them before I can connect them.

Soldering aside I've been having fun, and I have deployed several "real" projects in and around my flat. Perhaps the most interesting project shows the arrival time of the next tram to arrive at the end of my street:

That's simple, reliable, and useful. I have another project which needs to be documented which combineds a WeMos D1 and a vibration sensor - no sniggers - to generate an alert when the washing machine is done. Having a newborn baby around the place means that we have a lot of laundry to manage, and we keep forgetting that we've turned the washing machine on. Oops.

Anyway. Hardware. More fun than I expected. I've even started ordering more components for bigger projects.

I'll continue to document the various projects online, mostly to make sure I remember the basics:

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Patching scp and other updates.

Sunday, 8 January 2017

I use openssh every day, be it the ssh command for connecting to remote hosts, or the scp command for uploading/downloading files.

Once a day, or more, I forget that scp uses the non-obvious -P flag for specifying the port, not the -p flag that ssh uses.

Enough is enough. I shall not file a bug report against the Debian openssh-client page, because no doubt compatibility with both upstream, and other distributions, is important. But damnit I've had enough.

apt-get source openssh-client shows the appropriate code:

    fflag = tflag = 0;
    while ((ch = getopt(argc, argv, "dfl:prtvBCc:i:P:q12346S:o:F:")) != -1)
          switch (ch) {
            case 'P':
                    addargs(&remote_remote_args, "-p");
                    addargs(&remote_remote_args, "%s", optarg);
                    addargs(&args, "-p");
                    addargs(&args, "%s", optarg);
            case 'p':
                    pflag = 1;

Swapping those two flags around, and updating the format string appropriately, was sufficient to do the necessary.

In other news I've done some hardware development, using both Arduino boards and the WeMos D1-mini. I'm still at the stage where I'm flashing lights, and doing similarly trivial things:

I have more complex projects planned for the future, but these are on-hold until the appropriate parts are delivered:

  • MP3 playback.
  • Bluetooth-speakers.
  • Washing machine alarm.
  • LCD clock, with time set by NTP, and relay control.

Even with a few LEDs though I've had fun, for example writing a trivial binary display.



So I'm gonna start doing arduino-things

Saturday, 31 December 2016

Since I've got a few weeks off I've decided I need to find a project, or two, to occupy me. Happily the baby is settling in well, mostly he sleeps for 4-5 hours, then eats, before the cycle repeats. It could have been so much worse.

My plan is to start exploring Arduino-related projects. It has been years since I touched hardware, with the exception of building a new PC for myself every 12-48 months.

There are a few "starter kits" you can buy, consisting of a board, and some discrete components such as a bunch of buttons, an LCD-output screen, some sensors (pressure, water, tilt), etc.

There are also some nifty little pre-cooked components you can buy such as:

The appeal of the former is that I can get the hang of marrying hardware with software, and the appeal of the latter is that the whole thing is pre-built, so I don't need to worry about anything complex. Looking over similar builds people have made, the process is more akin to building with Lego than real hardware-assembling.

So, for the next few weeks my plan is to :

  • Explore the various sensors, and tutorials, via the starter-kit.
  • Wire the MP3-playback device to a wireless D1-mini-board.
    • Which will allow me to listen to (static) music stored on an SD-card.
    • And sending "next", "previous", "play", "volume-up", etc, via a mobile.

The end result should be that I will be able to listen to music in my living room. Albeit in a constrained fashion (if I want to change the music I'll have to swap out the files on the SD-card). But it's something that's vaguely useful, and something that I think is within my capability, even as a beginner.

I'm actually not sure what else I could usefully do, but I figured I could probably wire up a vibration sensor to another wireless board. The device can sit on the top of my washing machine:

  • If vibration is sensed move into the "washing is on" state.
    • If vibration stops after a few minutes move into the "washing machine done" state.
      • Send a HTTP GET-request, which will trigger an SMS/similar.

There's probably more to it than that, but I expect that a simple vibration sensor will be sufficient to allow me to get an alert of some kind when the washing machine is ready to be emptied - and I don't need to poke inside the guts of the washing machine, nor hang reed-switches off the door, etc.

Anyway the only downside to my plan is that no doubt shipping the toys from AliExpress will take 2-4 weeks. Oops.

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I finally made something worthwhile.

Monday, 26 December 2016

So for once I made something useful.


Oiva Adam Kemp.

Happy Christmas, if you believe in that kind of thing.



A simple Perl alternative to storing data in Redis

Friday, 16 December 2016

I continue to be a big user of Perl, and for many of my sites I avoid the use of MySQL which means that I largely store data in flat files, SQLite databases, or in memory via Redis.

One of my servers was recently struggling with RAM, and the suprising cause was "too much data" in Redis. (Surprising because I'd not been paying attention and seen how popular it was, and also because ASCII text compresses pretty well).

Read/Write speed isn't a real concern, so I figured I'd move the data into an SQLite database, but that would require rewriting the application.

The client library for Perl is pretty awesome, and simple usage looks like this:

# Connect to localhost.
my $r = Redis->new()

# simple storage
$r->set( "key", "value" );

# Work with sets
$r->sadd( "fruits", "orange" );
$r->sadd( "fruits", "apple" );
$r->sadd( "fruits", "blueberry" );
$r->sadd( "fruits", "banannanananananarama" );

# Show the set-count
print "There are " . $r->scard( "fruits" ) . " known fruits";

# Pick a random one
print "Here is a random one " . $r->srandmember( "fruits" ) . "\n";

I figured, if I ignored the Lua support and the other more complex operations, creating a compatible API implementation wouldn't be too hard. So rather than porting my application to using SQLite directly I could juse use a different client-library.

In short I change this:

use Redis;
my $r = Redis->new();

To this:

use Redis::SQLite;
my $r = Redis::SQLite->new();

And everything continues to work. I've implemented all the set-related functions except one, and a random smattering of the other simple operations.

The appropriate test-cases in the Redis client library (i.e. removing all references to things I didn't implement) pass, and my own new tests also make me confident.

It's obviously not a hard job, but it was a quick solution to a real problem and might be useful to others.

My image hosting site, and my markdown sharing site now both use this wrapper and seem to be performing well - but with more free RAM.

No doubt I'll add more of the simple primitives as time goes on, but so far I've done enough to be useful.

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