termtosvg – record terminal sessions as SVG animations

termtosvg (GitHub repo) is a handy little tool that makes recording animated sessions in the terminal as simple as humanly possible. Instead of generating heavy graphics or video animations, this tool creates SVG files, which are a lot smaller and easier. There is also a selection of themes to choose from.

Th resulting SVG files can be used as quick demos and guides in READMEs on GitHub, or as tutorials for your application’s website.

Lazydocker – a simple terminal UI for both docker and docker-compose

Lazydocker is a simple terminal UI for easier management of Docker. This is particularly useful for new Docker users, but can as well save plenty of keystrokes to the seasoned administrators.

Bash trick: Repeat last command until success

More and more often I come across a scenario where I need to repeat the shell command until it succeeds. Here are a couple of examples:

  • Reboot a server. Try to remotely login to it via ssh. This fails until the server actually boots up. Keep trying until connected.
  • Start an application that writes to the log file. Run “tail -f some.log” to watch the log messages. This fails if the log file does not exist yet. Keep trying until the application creates the log file and writes something into it.

Sure, I can always press the up arrow key and Enter, to repeat the last command from the history. But it is a tiny bit annoying.

Today I came across this little trick, that solves the problem. Add the following function to your .bashrc:

rpt() {
  CMD=$(fc -ln | tail -n 2 | head -n 1)
  echo "repeating until success: $CMD"
  until $CMD
  do
    sleep 1
  done
}

Now you can run “rpt” to repeat the latest command until it succeeds.

Handy!

Falsehoods programmers believe about Unix time

A while back I blogged a collection of “Falsehoods programmers believe about …“. One of those things was time. Today I came across a nice addition to that – “Falsehoods programmers believe about Unix time“.

These three facts all seem eminently sensible and reasonable, right?
1. Unix time is the number of seconds since 1 January 1970 00:00:00 UTC
2. If I wait exactly one second, Unix time advances by exactly one second
3. Unix time can never go backwards
False, false, false.

All three of these are false and for the same reason – leap seconds. The article provides a nice and easy explanation of how and why that happens.