monochromatic blog:
git clone git://
Log | Files | Refs

commit de4e65b4240ca5739b3e1d7e210d98a29637fea3
parent 23af2ff1ceb80c450a83ba1f2af4827ac8822c45
Author: z3bra <>
Date:   Wed,  2 Apr 2014 12:33:49 +0200

New article about status bar

2014/04/meeting-at-the-bar.txt | 517+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ | 12++++++------
index.txt | 6++++++
3 files changed, 529 insertions(+), 6 deletions(-)

diff --git a/2014/04/meeting-at-the-bar.txt b/2014/04/meeting-at-the-bar.txt @@ -0,0 +1,517 @@ +# [Meeting at the bar](#) +## &mdash; 02 April, 2014 + +### Introduction + +Hi everybody ! This post is more or less the continuation of my previous one: +[Home, sweet home](/2013/10/home-sweet-home.html). We will take desktop +customisations a little further here, so I'll assume that you, the reader, know +the base of linux system administration. + +Status bar can display anything you feed them with, so let's make that food +useful to us. We will learn how to display system informations on your screen. + +Here we go! + +### Summary + +* [head-up display](#hud) +* [fetching informations](#grab) + + +<h3 id='hud'>head-up display</h3> + +First of all, let's understand what an HUD is. Gamers can go the the next +paragraph. An HUD display some information you (most of the time) wants to see. +In video-games, that will be your life/armor points, or the number of ammos +loaded in your gun. Those information are almost always visible and are updated +in real-time. + +But we're not playing video games here. And you're probably not reading with a +loaded gun in your hand. So, sitting in front of your computer, you want other +kind of informations. We will talk about those informations later. +First, let's see HOW we will display them on-screen. I currently know 4 ways of +doing it (understand, I've not tried the alternatives): + +#### dzen + +From the official website: + +> Dzen is a general purpose messaging, notification and menuing program for +> X11. It was designed to be scriptable in any language and integrate well +> with window managers like dwm, wmii and xmonad though it will work with +> any windowmanger. + +Seems great ! Dzen is really simple to use, pipe text to it, and watch it +appear on your screen: + + echo shblah | dzen2 -w 120 -x 10 -y 10 -p 5 + +I'm not a huge fan of dzen anymore. I used to be (You can do awesome things +with dzen, just check [earsplit's dekstop](, but +I discovered a new tool that is basically dzen simplified, and written on top of +XCB (see the fourth alternative: bar). + +#### conky + +Here comes the king of HUDs, ladies and gentlmen, please put a knee to the +ground! +Conky's job is to display every possible information on your screen, in a really +eye-candy way. I made +[this]( monthes ago +using conky (do not ask for configs or wallpaper, I don't have them anymore). + +It is extensible in lua and has a heavy set of features built-in. +Check this out: [conky's variables]( +I've been using conky for weeks, but I just got bored. I realised that I did not +need so much infos in real-time. But that was a fun period ! + +Conky reads its configuration from the `~/.conkyrc` file. A minimalist config +would be: + + cat <<EOF > ~/.conkyrc + alignment tl + gap_x 10 + gap_y 40 + + TEXT + shblah + EOF + conky & + +But for just a simple thing, that's a bit overkill. +Note that there is also conky-cli that output informations to stdout. That is +useful to build informations lines to feed a bar with. To have a quick idea of +how this works, check this +[nice forum post]( by jmbi. + +#### tmux statusbar + +This one is a bit out of competition, but worth mentionning. TMux stands for +terminal multiplexer. Short story, you can have multiple terminal within a +single terminal window. But it offers a nice feature: a status bar, that is +displayed at the bottom of the window. You can run any command in here, or even +shell scripts, and the output will sit just there. + +Tmux actually have a left and right status bar. So just pick one (or both) to +display some infos: + + echo "set-option -g status-left "shblah" >> ~/.tmux.conf + tmux + +Phyrne wrote a [nice article]( +about it. Just read it. + +#### bar + +My last and prefered option, the bar made by LemonBoy ! +This small piece of software is a stripped down clone of dzen, written on top +of XCB (a better librairy to communicate with the X server). It's fast, it's +light and you can even script it, as it now has a clickable item that you can +use to start applications. More infos [here]( + +Bar is pretty easy to use. It works the same way dzen does, by piping text to +it: + + echo 'shblah' | bar -g 120x20+10+80 -p + +Starting from now, I will use bar as my tool of choice, but use the one you +prefer, they can all do such a thing (well, conky has pretty much everything +done for you, but meh) ! + +<h3 id='grab'>fetching informations</h3> + +Once you now which tool you'll use to display your informations, you need to +decide which one you want. For the purpose of the article, I'll settle on 8 of +them: + +* current date / time +* battery level +* sound level +* CPU load +* RAM used +* network connection state +* window manager groups +* mpd's current playing song + +I choosed those to show you many way to fetch informations on your computer. + +Before going any further, I need to introduce to you the tools we'll need, and +that we just CAN'T avoid to fetch informations.. + +* `awk` -- a powerfull script language, I don't know enough about this, though +* `cut` -- cut a string in small parts, and pick some parts of it +* `grep` -- should I really present 'grep' ? +* `sed` -- stream editor, it's useful to format outputs +* `test` -- test an expression and return 0 if it's true, >0 otherwise + +By the way, that would be a **HUGE** plus to know about [regular +expressions]( +So, here we go! + +#### current date / time + +There is nothing hard with it. The `date` utility has a parameter to format its +output. So we'll just use that: + + date '+%Y-%m-%d %H:%M' # print current date and time: yyyy-mm-dd HH:MM + +#### battery level + +There is this tool, `acpi` that can be used to output some infos on you system +power. But that's just not fun! We'll be messing with the `/sys` directory, +which is a goldmine. Feel free to navigate it, to see what you can find. + +Back to the battery. We are interested in two information, the current +charge of the battery (in percent) and if the charger is plugged in, or not. _on +my system_ (because it may be different on yours), I have those two files: + + /sys/class/power_supply/BAT1/capacity # contains a value from 0 to 100 + /sys/class/power_supply/BAT1/status # either "Charging" or "Discharging" + +We will then be able to output the battery level, and do some action, depending +on the battery state. To get the info: + + BATC=/sys/class/power_supply/BAT1/capacity + BATS=/sys/class/power_supply/BAT1/status + + # prepend percentage with a '+' if charging, '-' otherwise + test "`cat $BATS`" = "Charging" && echo -n '+' || echo -n '-' + + # append the character '%' after the number + sed 's/$/%/' $BATC + +#### sound level + +This one is always a pain.. I will assume that you use ALSA as your sound +system (because I have no idea how OSS or PulseAudio works). + +First, you need to know which channel your want to watch. Most of the time, +'Master' is a good choice. I personnally use `alsamixer` to navigate between the +channels to see what they are related to. The `alsa-utils` packages (name may +vary depending on the distribution) contains a utility named `amixer` to +interact with the system. The special command `amixer get <CONTROL>` is used to +query informations about a channel. But the output is awful to look at, so we'll +need to format it. Example output: + + ───── amixer get Master + Simple mixer control 'Master',0 + Capabilities: pvolume pvolume-joined pswitch pswitch-joined + Playback channels: Mono + Limits: Playback 0 - 64 + Mono: Playback 53 [84%] [-10.00dB] [on] + +You can notice that the info we're interested in sits at the end of the output. +That will make things easier. + + # parse amixer output to get ONLY the level. Will output "84%" + amixer get Master | sed -n 's/^.*\[\([0-9]\+%\).*$/\1/p' + +#### CPU load + +There are many way to get the current CPU load. `iostat` is one of them, and as +it's easy to parse its output, i'll go with a trickier approach, using `ps` and +`bc`. + +To get the current CPU load used by every program, one can use this command: + + # gives you the CPU load used by every running program + # 'args' is used here just so you can see the programs command lines + + ps -eo pcpu,argv + +We don't care about idling programs that uses '0.0' load or the header '%CPU', +so we can just remove them with `grep -vE '0.0|%CPU'`. + + ps -eo pcpu | grep -vE '0.0|%CPU' + +We now have a list of the CPU loads actually used, but per program. We just need +to sum them up! +The problem is: bash _CAN'T_ perform floating point operations. And thus, we +will need the help of the great `bc` to do so (if you don't have this installed, +I recommend that you just get it right away!). + +`bc` takes operations from stdin, and outputs to stdout. Pretty simple. Pretty +good. + + # use the "here-line" feature. + # tr replaces newlines with space, that we change in '+' through sed + # The whole line goes to bc which outputs the result + + CALC=`ps -eo pcpu | grep -vE '0.0|%CPU' | tr "\n" " " | sed 's/ / + /g'` + echo `bc <<< $LINE`% + +#### RAM used + +To display RAM usage (in the form `xx% (<used>/<total>)`, we will use another +place of the filesystem: `/proc`. This will be easier to find memory usage here, +than battery level in `/sys`: + + ───── ls /proc/ | grep 'mem' + iomem + meminfo + +If you take a quick look at `iomem`, you'll understand that it's **NOT** the +file we want here (I don't understand a bit of it)! Instead, let's take a look +at meminfo: + + ───── sed 8q /proc/meminfo + MemTotal: 2748648 kB + MemFree: 2209672 kB + Buffers: 34016 kB + Cached: 270728 kB + SwapCached: 0 kB + Active: 182292 kB + Inactive: 272636 kB + Active(anon): 150948 kB + +Good, good, exactly the information we want! So let's just extract them, using +`awk` to fetch _ONLY_ the column containing the value (Yeah, that's why I use +awk for mostly. I'll need to dive a little more in that language): + + ───── grep -E 'Mem(Total|Free)' /proc/meminfo |awk '{print $2}' + 2748648 + 2204288 + +At this point, you might realise that those two number are not really useful. We +will need to modify them a little by converting them to Mib, and making a ratio +out of them: + + # store the total and free memory in two variables + read t f <<< `grep -E 'Mem(Total|Free)' /proc/meminfo |awk '{print $2}'` + + # then, calcultate the percentage of memory used (scale=2 tells bc to + # calculate two digits after the floating point) + # cut will help us to get rid of the floating point that is useless here + echo `bc <<< "scale=2; 100 - $f / $t * 100" | cut -d. -f1`% + +#### network connection state + +Mmh, this one can be tricky! Ther are two cases here: + +* You have one interface +* You have more than one interface + +The first one is quite simple: use your interface name directly, and skip the +following section. + +Now what if you have, let's say two interfaces: ethernet, and wifi. Let's find +out HOW to get the currently used. +We will need two tools for that: `ip` (from `iproute2`) and `iwconfig` (from +`wireless_tools`). We will get the interfaces with `ip`, and recognize the wifi +interface using `iwconfig`. Sounds easy huh ? + + # The following assumes you have 3 interfaces: loopback, ethernet, wifi + read lo int1 int2 <<< `ip link | sed -n 's/^[0-9]: \(.*\):.*$/\1/p'` + + # iwconfig returns an error code if the interface tested has no wireless + # extensions + if iwconfig $int1 2>&1 >/dev/null; then + wifi=$int1 + eth0=$int2 + else + wifi=$int2 + eth0=$int1 + fi + + # this line will set the variable $int to $eth0 if it's up, and $wifi + # otherwise. I assume that if ethernet is UP, then it has priority over + # wifi. If you have a better idea, please share :) + ip link show $eth0 | grep 'UP' >/dev/null && int=$eth0 || int=$wifi + +This is now the time to see if network is up or not. For that, a simple `ping` +would do the trick: + + # just output the interface name. Could obviously be done in the 'ping' + # query + echo -n "$int" + + # Send a single packet, to speed up the test. I use google's DNS, + # but feel free to use any ip address you want. Be sure to put an IP, not a + # domain name. You'll bypass the DNS resolution that can take some precious + # miliseconds ;) + ping -c 1 2>&1 >/dev/null && echo "connected" || echo "disconnected" + + +#### window manager groups + +Aaah, the information that has the most way to be fetched! The problem with +this, is that every window manager provide a different way to fetch the number +of workspaces, and the current one. If you're lucky, and that your WM is +[EWMH]( compliant, `xprop` will be the way to +go. For the others, you will need to find a proper way on your own. For exemple, +to get the number of groups and the current group with ratpoison: + + echo "`ratpoison -c groups| cut -sd'*' -f1`/`ratpoison -c groups| wc -l`" + +iBack to the topic, fetching current group out of all the groups. To make this a +little more exiting, we will output something like `--o---`, 'o' being the +current desktop, '-' being the other desktops. + +The first step is to fetch the number of desktops, and the index of the current +one. To do that, let's use `xprop` + + cur=`xprop -root _NET_CURRENT_DESKTOP | awk '{print $3}' + tot=`xprop -root _NET_NUMBER_OF_DESKTOP | awk '{print $3}' + +If that enough for you, you can obviously just output `$cur/$tot` ;) +But now, the desktop indicator. To do that, there is two solutions: + +* cicle through all the groups and output either '=' or '|' +* ouput the correct number of '|' before and after '|' + +I tried both versions, and `time` reports that they are they're _almost_ the +same: + + ───── time; time + ==|======= + + real 0m0.025s + user 0m0.013s + system 0m0.000s + ==|======= + + real 0m0.020s + user 0m00m0.013s + system 0m0.000s + +We will then use the 'fillup' one. To improve performances, we will first fill a +variable with the 'group line', and then output it. It goes like this: + + # Desktop numbers start at 0. if you want desktop 2 to be in second place, + # start counting from 1 instead of 0. But wou'll lose a group ;) + for w in `seq 0 $((cur - 1))`; do line="${line}="; done + + # enough =, let's print the current desktop + line="${line}|" + + # En then the other groups + for w in `seq 1 $((cur + 2))`; do line="${line}="; done + + # don't forget to print that line! + echo $line + +#### mpd's current playing song + +After all that we did alredy, printing the current playing should bequite easy +as: + + cur=`mpc current` + test -n "$cur" && echo $cur || echo "- stopped -" + +Easy isn't it ? So let's add some difficulties to it. What if you have only 120 +pixels to display that ? +Aaaah trickyer isn't it ? + +Don't worry, I wrote a small tool for that: +[skroll]( You can see it in action +[here]( + +So now, our output has just become: + + cur=`mpc current` + test -n "$cur" && echo $cur |skroll -n 20 -d0.5 -r || echo "- stopped -" + +A small drawback with this approach: you can't put other infos in the same bar +as a `skroll`ing output, because it uses a `\n` or a `\r` to print the output. + +#### wrap it all ! + +Now that we have a whole bunch of informations, it's time to put them all in a +script, that we will pipe later to our HUD. + + #!/bin/sh + # + # z3bra - (c) wtfpl 2014 + # Fetch infos on your computer, and print them to stdout every second. + + clock() { + date '+%Y-%m-%d %H:%M' + } + + battery() { + BATC=/sys/class/power_supply/BAT1/capacity + BATS=/sys/class/power_supply/BAT1/status + + # prepend percentage with a '+' if charging, '-' otherwise + test "`cat $BATS`" = "Charging" && echo -n '+' || echo -n '-' + + # append the character '%' after the number + sed 's/$/%/' $BATC + } + + volume() { + amixer get Master | sed -n 's/^.*\[\([0-9]\+%\).*$/\1/p' + } + + cpuload() { + CALC=`ps -eo pcpu |grep -vE '0.0|%CPU' |tr "\n" " " |sed 's/ / + /g'` + echo `bc <<< $LINE`% + } + + memused() { + read t f <<< `grep -E 'Mem(Total|Free)' /proc/meminfo |awk '{print $2}'` + echo `bc <<< "scale=2; 100 - $f / $t * 100" | cut -d. -f1`% + } + + network() { + if iwconfig $int1 2>&1 >/dev/null; then + wifi=$int1 + eth0=$int2 + else + wifi=$int2 + eth0=$int1 + fi + ip link show $eth0 | grep 'UP' >/dev/null && int=$eth0 || int=$wifi + + ping -c 1 2>&1 >/dev/null && + echo "$int connected" || echo "$int disconnected" + } + + groups() { + cur=`xprop -root _NET_CURRENT_DESKTOP | awk '{print $3}' + tot=`xprop -root _NET_NUMBER_OF_DESKTOP | awk '{print $3}' + + for w in `seq 0 $((cur - 1))`; do line="${line}="; done + line="${line}|" + for w in `seq 1 $((cur + 2))`; do line="${line}="; done + echo $line + } + + nowplaying() { + cur=`mpc current` + # this line allow to choose whether the output will scroll or not + test "$1" = "scroll" && PARSER='skroll -n20 -d0.5 -r' || PARSER='cat' + test -n "$cur" && $PARSER <<< $cur || echo "- stopped -" + } + + # This loop will fill a buffer with our infos, and output it to stdout. + (while :; do + buf="" + buf="${buf} [$(groups)] -- " + buf="${buf} CLK: $(clock) -" + buf="${buf} NET: $(network) -" + buf="${buf} CPU: $(cpuload) -" + buf="${buf} RAM: $(memused) -" + buf="${buf} VOL: $(volume) -" + buf="${buf} MPD: $(nowplaying)" # use $(nowplaying scroll) to get a + # scrolling output! + echo $buf + sleep 1 # The HUD will be updated every second + done) + +All you have to do now is to pipe this script to your status bar of choice: +`./bar-generator | bar -B \#1d1d1d`. + +There you are! You now know how (ow ow ow) make your system talk to you. +Obviously, this is a raw script, and it can be heavily improved (eg, add some +colors, parse CLI arguments, etc..). + +But I'm pretty sure that it's a good start for your imagination. By the way, if +you find neat tricks to improve the performances of the functions listed above, +feel free to mail me these, I'll be glad to modify them! + +Now go ahead, and watch how your computer tell you how he (or she) feels... +Isn't that **amazing** ?! + +<!-- vim: set ft=markdown ts=4 et tw=80: --> diff --git a/ b/ @@ -4,16 +4,16 @@ NAME = monochromatic PREFIX = /srv/http/ PAGES = index.html \ - 2013/12/love-me-some-latex.html \ - 2013/11/plain-old-mails.html \ - 2013/10/home-sweet-home.html \ + about.html \ 2013/08/test-your-css.html \ 2013/08/the-hard-way.html \ 2013/09/java-without-eclipse.html \ - 2014/03/unleash-your-desktop.html \ - 2014/03/toolbox.html \ + 2013/10/home-sweet-home.html \ + 2013/11/plain-old-mails.html \ + 2013/12/love-me-some-latex.html \ 2014/01/images-in-terminal.html \ - about.html + 2014/03/toolbox.html \ + 2014/04/meeting-at-the-bar.html FEEDS = rss/feed.xml EXTRA = css img favicon.ico diff --git a/index.txt b/index.txt @@ -1,3 +1,9 @@ +# [Meeting at the bar](/2014/04/meeting-at-the-bar.html) +## &mdash; 02 April, 2014 +I know that I will deceive some people but I'm not talking about alcohol here! +This article is about building a status bar for your beloved desktop. And we +will do this **the hard way**... + # [Toolbox](/2014/03/toolbox.html) ## &mdash; 12 March, 2014 Yeah, yet another list of unix tools. Feel free to avoid it, but you'll