On Unicode

Michał ‘mina86’ Nazarewicz | 25 października 2015

There is a lot of misconceptions about Unicode. Most are there because people assume what they know about ASCII or ISO-8859-* is true about Unicode. They are usually harmless but they tend to creep into minds of people who work with text which leads to badly designed software and technical decisions made based on false information.

Without further ado, here’s a few facts about Unicode that might surprise you.

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Bash right prompt

Michał ‘mina86’ Nazarewicz | 28 września 2015

There are multiple ways to customise Bash prompt. There’s no need to look for long to find plethora of examples with fancy, colourful PS1s. What have been a bit problematic is having text on the right of the input line. In this article I’ll try to address that shortcoming.

Getting text on the right

The typical approach is using PROMPT_COMMAND to output desired content. The variable specifies a shell code Bash executes prior to rendering the primary prompt (i.e. PS1).

The idea is to align text to the right and then using carrier return move the cursor back to the beginning of the line where Bash will start rendering its prompt. Let’s look at an example of showing time in various locations:

__command_rprompt() {
	local times= n=$COLUMNS tz
	for tz in ZRH:Europe/Zurich PIT:US/Eastern \
	          MTV:US/Pacific TOK:Asia/Tokyo; do
		[ $n -gt 40 ] || break
		times="$times ${tz%%:*}\e[30;1m:\e[0;36;1m"
		times="$times$(TZ=${tz#*:} date +%H:%M)\e[0m"
		n=$(( $n - 10 ))
	done
	[ -z "$times" ] || printf "%${n}s$times\\r" ''
}
PROMPT_COMMAND=__command_rprompt
Terminal window presenting right prompt behaviour.

Clearing the line on execution

It has one annoying issue. The right text reminds on screen even after executing a command. Typically this is a matter of aesthetic but it also makes copying and pasting session history more convoluted.

A manual solution is to use redraw-current-line readline function (e.g. often bound to C-l). It clears the line and prints the prompt and whatever input has been entered thus far. PROMPT_COMMAND is not executed so the right text does not reappear.

Lack of automation can be addressed with a tiny bit of readline magic and a ~/.inputrc file which deserves much more fame than what it usually gets.

Tricky part is bindind C-m and C-j to two readline functions, redraw-current-line followed by accept-line, which is normally not possible. This limitation can be overcome by binding the key sequences to a different sequence which will be interpreted recursively.

To test that idea it’s enough to execute:

bind '\C-l:redraw-current-line'
bind '\M-\C-j:accept-line'
bind '\C-j:"\C-l\M-\C-j"' '\C-m:"\C-j"'

Making this permanent is as easy as adding the following lines to ~/.inputrc:

$if Bash
    "\C-l": redraw-current-line
    "\e\C-j": accept-line
    "\C-j": "\C-l\e\C-j"
    "\C-m": "\C-l\e\C-j"
$endif

With that, the right prompt will disappear as soon as the shell command is executed. (Note the use of \M- in bind command vs. \e in ~/.inputrc file).

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Mobile is the Future

Michał ‘mina86’ Nazarewicz | 17 marca 2015

Photo of a smashed mobile phone.

(photo Cory Doctorow, CC-BY-SA)

A few days ago I received an email from Google Wembaster Tools saying no more no less but: ‘Your webpage sucks on mobile devices!’ Or something. Now that I think of it, I could have been worded slightly differently. The gist was the same though.

I never really paid that much attention to how my site looks on phones and tables. I’ve made sure it loaded and looked, but apart from that never spent much time on the issue. I always thought optimising for a small screen would be a lengthy and painful process. How mistaken I was!

In my defence, when I last looked at the problem, state of mobile browsers was different; now there are really just two things to do. First of all, add a viewport meta tag, e.g.:

<meta name=viewport
      content="width=device-width, initial-scale=1">

and then use min-width or max-width CSS media queries. Admittedly the second part may take some time, but if your layout uses simple markup rather than being TABLE-based, reading the excellent article on A List Apart might turn out to be the most time consuming step.

If you haven’t already, do take a look at whether your website looks reasonably well on small screens. Apparently mobile is the future, or some such.

The ‘bad’ news is that I’ve dropped endless scroll feature. This is because in narrow layout the sidebar moves to the bottom and endless scrolling would make it unreachable since it would run away all the time.

The time has come to stand up for the GPL

Michał ‘mina86’ Nazarewicz | 11 marca 2015

For people who know me it should come with no surprise that support free software in most forms it can take. I also believe that if someone gives you something at zero price, basic courtesy dictates that you follow wishes of that person. This is why when Software Freedom Conservancy started a GPL Compliance Project for Linux Developers I didn’t hesitate even for a minute to offer little Linux copyright I held to help the effort.

Most importantly though, it is why I fully support Conservancy in taking legal action against VMware which for years has been out of compliance with Linux’s license.

If you care about free software, the GPL or want more projects like OpenWrt, consider donating to help Christoph Hellwig and the Conservancy with their legal battle against this multi-billion-dollar corporation who for some reason decided to free-ride on other people’s work without respecting their wishes.

If you don’t feel like, or for whatever reason cannot donate, twitting something along the lines of ‘Play by the rules, @VMware. I defend the #GPL with Christoph & @Conservancy. #DTRTvmware Help at https://sfconservancy.org/supporter/’ or otherwise spreading the word will help as well. Oh, and in case you were, like I was, wondering — DTRT stands for ‘do the right thing’.

And if you want to know more: