Archive for January, 2010

fake a dual monitor display!

January 30th, 2010

Wouldn't we all love to have a beefy workstation with at least two giant lcd monitors? Alas, I have a slim laptop with a small screen. And another laptop, almost 10 years old, albeit with a nice and large screen. I naturally prefer to use the newer machine for performance, but it also means making do with a small monitor.

I can tell you it's a real pain to author latex documents this way, I can't fit both the kile and evince on the screen at the same time. It wasn't until recently that it hit me what I was doing wrong. There are three processes involved here:

  1. Document editor.
  2. Compiler (I run a loop that invokes make continuously in the background).
  3. Document viewer.

Come to think of it, this applies just as well to coding if you think "running the code" on the last step.

Well, X11 is a display server, for peet's sake! So you have the editor on the workstation, but then you log in from the other laptop (with the larger screen) and run evince to display there.

Just do:

oldlaptop$ ssh -XYC workstation

Don't ask me why -Y, I don't know, but that's how I get my ubuntu to allow remote connections.

a firewall in layman's terms

January 20th, 2010

Dealing with companies can be frustrating, because they like to appear opaque to the outside world. When you look on the website you find a page with contact information. You'll find a phone number and an email address, and maybe more than one if it's a large company with several departments. But they all point to the reception. Few companies are generous enough to give you direct access to their personnel with a listing of employees and their contact information.

So if there is a person you have to get to you have to do it through the reception. "Yes, I am blah and I need bleh and why don't you just transfer me to the person I need to talk to, per favore!" It's not a lot of fun, but this way whoever makes this decision to give out only the number of the reception can also decide who may and may not receive calls. And even on what conditions. If you say the magic word then, yes, you can get Frank on the line, otherwise not. And maybe Steve has been known to say too much and has a history of divulging information he wasn't supposed to. So no, you can't talk to Steve.

Well, this is the principle of a firewall. The reception screens calls with the discretion to reject or divert according to the protocol that has been instituted. Some people can be reached anytime, others only at certain intervals. Some are available depending on your request, and some are completely unreachable.

This picture, however, conflicts with the original meaning of the word firewall, which is a wall erected to stop a fire from spreading. Unconditionally.

detecting the os and distro on the system

January 6th, 2010

Linux, in all its diversity, sometimes lacks very basic mechanisms that you would be prepared to take for granted. For instance, picture this scenario.. you are on some system you don't know well. Maybe it's your friend who called you over to his house for help with something. Maybe it's the computer lab where you don't know the setup. Maybe it's a remote session to a box you've never seen. Quick question: what's it running?

Well, bash --version tells you about bash, ls --version tells you about coreutils and so on, you can keep going with that. uname will tell you about the platform and the kernel, useful stuff. What about the distro? Distros are diverse, sometimes it helps a lot to know what kind of environment you're in. Well, strangely enough, there's no standard answer to that.

They all do their own thing, if they do at all. Some distros use lsb_release to dispense this information. Others have files in /etc that you can check for, if you know what they are supposed to be called. So I decided to try and detect this. I've checked a bunch of livecds and it works on those distros that identify themselves somehow.


# Author: Martin Matusiak <>
# Licensed under the GNU Public License, version 3
# <desc> Detect OS (platform and version) of local machine </desc>
# <usage>
# source this file in bash, then run `osdetect`
# </usage>

_concat() {
	local s="$1";shift;
	while [ "$1" ]; do
		s="$s $1"; shift
	echo "$s" | sed "s|^[ \t]*||g" | sed "s|[ \t]*$||g"

_glob() {
	local file=
	local glob=
	local lst=
	while [ -z "$file" ] && [ "$1" ]; do
		lst=$(ls $glob 2>/dev/null | grep -v /etc/lsb-release)
		if [ "$lst" ]; then
			file=$(echo "$lst" | head -n1)
	echo "$file"

osdetect() {
	# ref:

	local os=
	local release=
	local machine=
	if ! which uname &>/dev/null; then
		echo -e "${cred}No uname on system${creset}" >&2
		os=$(uname -s)
		release=$(uname -r)
		machine=$(uname -m)
	if [ "$os" = "SunOS" ]; then
		machine=$(uname -p)
	local platform="$(_concat "$os" "$release" "$machine")"

	# prefer lsb_release
	if which lsb_release &>/dev/null; then
		local id="$(_concat "$(lsb_release -i | sed "s|.*:||g")")"
		local rel="$(_concat "$(lsb_release -r | sed "s|.*:||g")")"
		local code="$(_concat "$(lsb_release -c | sed "s|.*:||g")")"
	elif [ -f /etc/lsb-release ]; then
		local id="$(_concat "$(grep DISTRIB_ID /etc/lsb-release | sed "s|.*=||g")")"
		local rel="$(_concat "$(grep DISTRIB_RELEASE /etc/lsb-release | sed "s|.*=||g")")"
		local code="$(_concat "$(grep DISTRIB_CODENAME /etc/lsb-release | sed "s|.*=||g")")"

	# find a file or another
		local vfile=$(_glob "/etc/*-rel*" "/etc/*_ver*" "/etc/*-version")
		[ "$vfile" ] && local id=$(cat "$vfile")

		# distro specific
		[ "$vfile" = /etc/debian_version ] && [ "$id" ] && id="Debian $id"

	[ "$id" = "n/a" ] && id=
	[ "$rel" = "n/a" ] && rel=
	[ "$code" = "n/a" ] && code=

	local version="$(_concat "$id" "$rel" "$code")"
	[ ! -z "$version" ] && version=" ~ ${cyellow}$version${creset}"

	echo -e "Platform: ${ccyan}${platform}${creset}${version}"