Simple Tips for developers

Skipping Certificate Checks with wget

2015-01-18T14:06:00.002+00:00

Just a quick post - if you want to download a file using wget from a server that has an invalid ssl certificate (expired, not from a trusted issuer etc) and you're confident the server is correct then you can use the --no-check-certificate switch to make wget ignore the certificate error:

$ wget --no-check-certificate http://downloadfile.com

Convert flv to mp4 on mac for free using open source tools

2012-10-22T17:52:00.001+01:00

I'm not paying some rip off price to convert a bunch of flv's into mp4's so I can load them onto my ipad. The solution was actually pretty simple:

First off, installing the ffmpeg library you need to specify which compiler to use:

$ brew install ffmpeg --use-clang

Once you've sorted that, just navigate to the directory containing your flvs, and type:

$ for file in *.flv; do; /usr/local/bin/ffmpeg -i $file.flv -sameq -vcodec libx264 -ar 22050 $file.mp4; done

Job done.

Install GNU GCC on OSX Mountain Lion the easy way using Homebrew

2012-08-28T11:17:00.002+01:00

This is actually targeted towards our OSX friends, here's a problem I came up against recently setting up a new mac book air, running OS X Mountain Lion, ready for ruby on rails development.

If you need to install any Ruby that’s older than 1.9.3, such as 1.9.2, 1.8.7 or REE, you’ll need to install GCC 4.2. Apple does not ship the Command Line Tools with gcc-4.2compiler anymore (you can check by running which gcc-4.2), so you need to install it via Homebrew. By default, Homebrew doesn’t include any formula that ships with the OS in the main repository, so you’ll have to enable homebrew-dupes repository by using brew tap

brew tap homebrew/dupes
brew install apple-gcc42

Voila! Now you can compile any library that requires non-LLVM GCC.

How to format a hard drive so it works with Linux, Mac OSX and Windows

2012-08-26T13:10:00.002+01:00

This is such a great tip, I'm actually excited to share it. If you have an external hard drive its not unreasonable so suggest that you might want to connect it to more than one computer. Its also quite possible you'll want to read and write with more than one type of Operating System. You would think this would just be standard stuff, but its not. However, as is so often the case, linux makes it easy for you. Simply connect the drive and using disk utils or type (this only works with the device mounted):

$ mount|grep ^'/dev'

To list the devices and identify your chosen disk. Then we need to install a small utility called udftools, as usual is as simple as:

$ sudo apt-get install udftools

Then we're ready to format your hard disk, ready for use. Just type the following command:

$ sudo mkudffs --media-type=hd --blocksize=512 /dev/sdx

(You need to replace /dev/sdx with your device id)
Once thats done, you are free to mount your device in which ever OS you like and it should work as expected.
Enjoy your day :)

Useful debugging tip: Printing arrays in a human readable format using ruby-debug

2012-08-08T14:55:00.001+01:00

When using ruby-debug, sometimes you want to list the methods an object has.
When you just print out the array you'll get a big unreadable list like this:

(rdb:1) p subject.methods

│[:call, :[], :===, :yield, :to_proc, :arity, :clone, :dup, :==, :eql?, :hash, :to_s, :lambda?, :b
│inding, :curry, :source_location, :parameters, :bind, :psych_to_yaml, :to_yaml_properties, :to_ya
..
│ry, :`, :shared_examples, :shared_context, :share_examples_for, :shared_examples_for, :share_as,
│ual?, :!, :!=, :instance_eval, :instance_exec, :__send__, :__id__]

However, using "ps" generates a far more readable, alphabetically sorted list:

(rdb:1) ps subject.methods

│!                        gem                              require_dependency
│!=                       hash                             require_or_load
│!~                       html_safe?                       respond_to?
│<=>                      in?                              respond_to_missing?
...
│freeze                   quietly                          with_options
│friendly_id?             require                          with_warnings
│frozen?                  require_association              yield

Not something you'll need all the time, but definitely a good to know....

Run Nyan Cat in your terminal

2012-07-25T16:23:00.000+01:00

This needs no introduction, its just cos its cool...

Open a terminal window and type:

$ telnet miku.acm.uiuc.edu

enjoy....

How to easily sort your mp3's by genre

2012-07-05T08:25:00.001+01:00

Its not very often that I want to promote my own code, but there's something I've found really useful in getting my mp3 library sorted just the way I want.

But before I send you off to the code, let me first explain the itch that forced the scratch. I have lots of music files, some are used for easy listening, some are used for DJ'ing with the most amazing open source DJ software. The tracks for DJ'ing are a different style so I keep them in a different folder. Before though, I had everything in one huge Music folder.

What I needed was a way to sort all the files by genre so then I could pull out the dj tracks easily. I tried all sorts of apps but nothing quite did what I needed. So it was time to roll up my sleaves and roll my own. Turns out it wasn't that tricky.

I used python because its fast, and there's some good libraries out there to help with reading the mp3 meta data.

The project started out just trying to sort a bunch of mp3's by genre, but as you'll see, I have added a few more scripts to help with things like rounding bpm, clearing track numbers from the title, printing duplicates, and various other tricks.

The code is available here:

https://github.com/ktec/audioscripts

Please be warned, though, these scripts can damage your files, so make sure you back up your files before you start!!!!

If you have suggestions or improvements, please feel free to fork the project and send me pull request.

Convert a list of files to lowercase with one line command

2012-07-04T09:24:00.000+01:00

If you've got a bunch of files with names in mixed case, and you want them all neat and tidy with lowercase, this is way to do it:

for x in $(ls); do mv $x $(echo $x  | tr '[A-Z]' '[a-z]'); done;

Learn to use git merge like a pro

2012-07-02T02:45:00.001+01:00

Its been a long time since I moved from svn over to using git as my source control of choice, and the benefits are huge, but I still remember those first few months trying to understand it.

For a long time I've been following the principal of branch per feature, or hack, but when it comes to merging I've always just merged straight back in. Thats fine, but if you're like me, you commit every 5 minutes to ensure you have a clean backup - the problem with this is you master branch gets flooded with micro commits - and consequently the log also. And this also makes life harder in the future when you decided to pull a feature, or you want to allow another developer to pull the feature into their own branch. This is where squashing the merge into one commit really makes sense.

Today I figured its about time I started squashing, so after a quick google I found this great resource. Its well worth adding to your feed reader.

How to search for a word in all files recursively

2012-06-27T05:56:00.001+01:00

It occurred to me today that I use this command all the time, but hadn't posted about it. Its only a short one, but so useful.

Lets say you want to look through all files in the current directory recursively...grep comes to the rescue:

$ grep -r "Search Term Here" .

Is all you need!!! There's many more options to play with, but this is a great start for beginners.

Where's my bash command history?

2012-06-23T00:14:00.004+01:00

If you're like me, you use the terminal all day long, and sometimes forget those useful commands you use the history feature to remind yourself like this:

history | grep "search term here"

Sometimes however, that command you worked out just isnt there anymore, but fear not, Bash keeps it’s own history in a file. You can view that file as stated before, or by opening

~/.bash_history

You can search through your bash_history by piping your history file into grep like so:

more ~/.bash_history | grep "wget"

Chances are, you'll find your command. So whats going on here? Well if you pop open your ~/.bashrc file you'll find the following settings:

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1024
HISTFILESIZE=40960

As you can see, the history is cropped, but the commands are stored in the file, so this means your shell opens quickly, and doesn't load that whole 40Mb file (mine is set really large so I can store everything - and I usually transfer this to new builds)

So there you have it, despite what it might seem, all is not lost....

segmentation fault error?

2012-06-20T00:04:00.002+01:00

Find out yourself :-) This really helped me today....

If you are using gcc, add -g flag when compiling, and then run it using gdb:

$ gdb your-executable

and then

 > run

and then when it gives the seg-fault, this is where we can start debugging:

 > backtrace

This will give you a good hint about what is wrong.

Update the year on a bunch of photos from the command line

2012-06-13T22:59:00.001+01:00

Its an easy mistake to make, you reset your camera, and enter the date wrong - well maybe just part of the date - this is exactly what I did, I added 2013 instead of 2012. Now a bunch of my photos are sorted wrong and I want to fix it. Being linux of course there's an easy command line solution.

Using a clever little utility called jhead makes it easy to manipulate the EXIF data for jpeg files. This is easy to install as always:

$ sudo apt-get install jhead

Now we can update the header, we need a small bash script to run through all JPG's in the current directory and update the year, then update the filestamp and we're good to go:

#~/bin/bash
for i in *.jpg
do
jhead -ds2012 $i
jhead -ft $i
done

Now just make it executable with:

$ chmod +x ./update_exif_year.sh

And now just run your new script and sit back and enjoy...

$ sh ./update_exif_year.sh

I tend to keep little scripts like this in my local bin,

$ mv ./update_exif_year.sh ~/bin/

Convert Google Maps Zoom level to traditional Map scale

2012-05-20T03:42:00.003+01:00

Ever wondered how to convert map scale to google zoom and vice versa?
I’ve made some calculations using the tilling scheme provided by google to calculate envelope’s in each zoom level.
(Remember that Google Maps use Mercator meters)
Here are my results:

Zoom level 0    1:20,088,000 meters
Zoom level 1    1:10,044,000 meters
Zoom level 2    1:5,022,000 meters
Zoom level 3    1:2,511,000 meters
Zoom level 4    1:1,255,500 meters
Zoom level 5    1:627,750 meters
Zoom level 6    1:313,875 meters
Zoom level 7    1:156,938 meters
Zoom level 8    1:78,469 meters
Zoom level 9    1:39,234 meters
Zoom level 10 1:19,617 meters
Zoom level 11 1:9,809 meters
Zoom level 12 1:4,909 meters
Zoom level 13 1:2,452 meters
Zoom level 14 1:1,226 meters
Zoom level 15 1:613 meters
Zoom level 16 1:307 meters
Zoom level 17 1:153 meters
Zoom level 18 1:77 meters
Zoom level 19 1:38 meters

possibly undefined macro: AM_GCONF_SOURCE_2

2012-04-23T02:43:00.002+01:00

When trying to generate the GNU-style infrastructure for an open source project recently I was faced with this interesting error:

configure.ac:39: error: possibly undefined macro: AM_GLIB_GNU_GETTEXT
configure.ac:196: error: possibly undefined macro: AM_GCONF_SOURCE_2
autoreconf2.50: /usr/bin/autoconf failed with exit status: 1

Fortunately the answer is easy, just install this:

$ sudo apt-get install libgconf2-dev

How can I extract a load of zip files in a directory?

2012-04-19T14:01:00.003+01:00

Use the command line of course!!

$ find -name "*.zip" -exec unzip {} \;

How to kill defunct processes in linux

2012-04-15T14:42:00.003+01:00

Many of us have faced this questions so many times. May be many of us have solved this issue too. Here, in this topic I just want to help those who were not able to sort out this issue and find it hard to kill these processes.

Sometimes when we run command

$ ps ax | grep sh

We get below output

11771 ?        Zs     0:00 [sh] 
14305 pts/0    S+     0:00 grep sh
26038 ?        Zs     0:00 [sh] 
23023 pts/0    Ss     0:00 -bash

and so on...

In above output we see some <defunct>, which means the process is either completed its task or has been corrupted or killed, but its child processes are still running or these parent process is monitoring its child process, hence we see these entries.

To kill this kind of process kill -9 PID don't work, we can try to kill with this command but it will show this again and again.
So we need to kill the parent process of this process.
For which we need to know, which is parent process of this defunct process. To know this we need to run below command which will show us which is the parent process of this process;

$ ps -ef | grep defunct

This will give output as below;

root     11771 11764  0 Mar11 ?        00:00:00 [sh] <defunct>
root     14440 23058  0 23:14 pts/0    00:00:00 grep defunct
root     26038 26037  0 14:51 ?        00:00:00 [sh] <defunct>

In above output we can see 6 columns which are as follows;

UID       PID    PPID   C   STIME   TTY    TIME       CMD
root     11771    11764 0   Mar11   ?      00:00:00   [sh] 
root     14440    23058 0   23:14   pts/0  00:00:00   grep defunct
root     26038    26037 0   14:51   ?      00:00:00   [sh]

I've adjusted above column to understand better.

So now we have got parent process id from above command. Now just kill the parent process id.

$ kill -9 11764 26037

And verify that now you are not getting any <defunct> process in out put of below command.

$ ps ax | grep sh

An error occured while installing RedCloth (4.2.7) SOLVED

2012-04-07T00:16:00.004+01:00

Ok, so an error occurred, but how do you get around it?

You can solve this with issue by overriding the compiling CFLAGS like this:

$ gem install RedCloth -v 4.2.7 -- --with-cflags=\"-O3 -pipe \
            -march=core2 -Wno-unused-but-set-variable\"

Note:
-O3: third optimization level (hard-core users). You can use -O2 instead.

-march=core2: my processor family. You can use -march=native instead.

-Wno-unused-but-set-variable: ignoring unused but set variable warning.

A complete list of AIM listed stock EPIC codes

2012-04-03T12:30:00.001+01:00

SPA FDT RGO C21 TTR 3DD ATUK ABBY ABB ABC ABL ACC AXS ACM ACMG APL ACTA AEG ADA ADT AFMF ASW AMS APC ATG AFN AEC AFC AFF AOF AAAM AFCR ACU AFE AMEI AME AMI AGI AGTA ATE ACS AIM AIEA APG AISI AKR ALBA ABM ALO ADI AXM ALK ALLG APNO AGY APHA APH AGLD ALL APS ATPT ALR AN. ALT ANR AMBR AMER AFS AMO AMP AMC AEN AND ASY ABH ANGM AGL AAZ ANCR ANTP AEY AOR API ABTX ARBB ARCH AR. ARC ARDN ARGO AREO ARG AGQ AAU ADID ADIS AMR ARTA ART AST ASH ACHP ADH ACHL AGP PALM ASC ASTO ASTR ATH AHG ATC ATL AUG AUK AUL AURR AUR ACZ ALG AVCT AVA AVN AVR AVS AVIA AVG AVI AVM BPM BPC BLEY BML BTC BGO BNK BAO BQS BHL BCBS BCBW BCB BHR BEG BVM BZM BEM BMR BKY BEST BXP BZT BGTI BGBL BDT BILL BILN BIP BIOM BKSA BLCK BES BLNX BLU BSST BODI BDI BOOM BOR BLVN BRY BMTP BMTO BMT BJU BSP BRH BREE BRT BRK BKWB BRU BUR BRST BYOT CDN CMCL CNN TREE CAMB CAO CNMI CF. CPX CMIP CEL CPC CIU CAPE CLA CPUB CARE CTH CPT CDY CBOX CSH CMX CVH CAZA CAZD CBAY CB. CLTV CLL CCP CCPA CCPC CNKS CAML CEPS CFU CWR CGH CORE CORW CMH CPL CPLC CPLP CCT CHAR CCAP CHC CAE CLS CFC CGA CGOP CGOW CPEH CHNS CHWI CWO CTG CHH CHL CICR COP CCS CAP CEB CEBW CLEA CTN CLC CLF CPSP CZA CEO CBRA CGG CHRT CFX COL COMS CNC CNR CXM CON CDG CGM CFL CIC COO CDC CRA CORO COV CPS RIG CRW CRAW CRHL CRO TIDE CIG CMG CSB CRS CSC CSFG CSS CBX CUP CVSG CYAN CRX CSG DOO DAY DAN DTG DTC DTE DAV DWSN DCD DDD DL. DLC DEMG DSN DEO DESC DES DDE DWHT DWHA DHIR DCP DGB DIGI DSG DXR DME DISL DMP DODS DCI DPL DMG DOTD DBAY DPP DQE DRG DUPD DRV ETX EPO EBP EEP ELR EFD EBQ ECK EAH ECV ECR EDL EDD EGS EDR EIH EKF ELCO ELE EKT ECAP ECAW EMED EML EMIS EMR EME EO. EDA ENEG EGX ENGI ETQ EXXI EXXS EEE ENV ENVS ESR EVN EVNW ENRT ESO EQEO EQEW EHP PAL ERE EROS ERU ESG ESS ECDC EUA EIIB ENK EOG ECPC EGU EVT EVOL XPS FTS FRP FKL FOGL FSF FPM FDBK FRX FCR FFA FND FIF FDI FAN FDP FPO FKE FITB FLK FSG FBT FRM FTE FEP FEN FRR FML FCRM FUZ8 FIP FUM FFY GAH GAL GLR GON GTE GAS GBG GCM GBF GEM GNG GPK GTC GGG GLOK GBR GED GBP GBO GMA GOAL GOI GOO GDP GRL GHH GWMO GGP GCO GDG GKO GLIF GSL GFM NBT GTL GKP GPX GVC GWP HAT HAIK HALO HAL HMB HUW HMY HGR8 HDD HSP HAR HGV HVE HTI HTIA HCEG HLO HSM HVT HVTB HVTA HLS HEGY HCL HEP HER HSS HGM HTIG HRCO HMLH HDT HZM HTT HCP HUM HCM HYD HYR HYDG ISL IDG ICB IDA IDS IDOX IBPO IGAS ILA IKA ILX IGE ILI IMTK IMJ IME IDH IMM IHUK IPX IPEL IVOF IVON IVO IMD IRG IGC IGCW IHC IEL IRGP IND IDM IRC INDI INFO INFS IIP IIPW INFA IMAC INL INNO INC INS IFM IHP INB IGP ISG INTQ ITQ IMIC IGR INRE INVU IOF IOM IPNT IPP IPSA IPS IQE ISPH ISH IBB ITA IAE ITM JQV CRPR JHDA JHD JPLH JRIC JIM JLF JHL JJB JLH JSG JNY JSJS JSM JUB JLP JDG JIL JCR KBT KAH KLG KDR KBC KDDG KEA KED KEFI KLN KEN KENZ KIBO KWI KIO KGI KSI KYS KUBC LGN LKI LND LOGP LTHP LTHM LEAF LED LDP LDSG LEE LEG LGNG LGO LRL LID LSIC LSI LGT LCT LPX LIV LOQ LHD LOK LMT LRM LSC LCG LOND LONG LONR LZM LWT LCA LPH LPA LEF LEFW LUD LUP LXB WINK SAA MPE MOIL MMS MAI MJW MMF MSS MNGS BB43 MAN MFX MPLE MAR MAC MARL MCII MASA MTEC MTA MTW MXP MAX MXM MAYG MUBL MCRB MDM MDY MOG MVC MEDU MEDG MDC MSQ MDZ MDST MEDI MDW MEN MHG MERC MRG MES MTT MRX MTL MNC MET MRM MBH MSYS MST MSG MWH MIO MIRL MIN MIRA MLD MCAP TMMG MDG MOS MBT MBW MBO MWG MONI MM. MRN MORT MCM MTV MOGP MWE MUL MUR MWA MBE NBR NANO NASA NSN NARS NGR NPE NUS NBNK NCCL NEO NET NETD NPT NGH NWKI NEPI NWT NRR NFC NGG NXS NGP NICL URU HAWK NBL NTBC NCON NLD NMG NSH NORK NBB NGL NRRP NTA NBI NTBR NWIG NTOG NVTA NOP NUM NWF NYO OTE OAH OCL OBT OPF OHM OEX ODX OMG ONL OBP OPG OSG OPE OPAY ORA ORCP OCH OGN OPP ORM OMI OSU OTC OTV OTM OVG OXA OCG ONG OXS PACL PAX PHU PCA PMS PAF PPA PMR PANR PRG PAA PKG PPH PMG PSQ PGD PFP PTS PHO PTV PGL PNA PEN PPR PNG PGH PEG PTMN PDL PET MATD PCI PELE PTR PHRX PHRM PKP PSL PHSC PYC PGB PCL PINN PIP PTD PVT PPT PPTR PHC PIM PLA PPN PTEC PLE POS PMK PMEA PMEW POLR POL PTCM PMP PCGB PFLM POWR PRA PMA PPC PRES PRZ PACC PFO PRP PDC PCF PCFB PHD PBTY PIL PRO PGC PTH PROP PPIX PPIR PMHL PRDF PVF PRM PPS PROV PXS PVR PRX PGS PSPI PTO PUR PURE PDX QRES QIH QDG QFI QYM RGI RAB RSS RDP RAM RMM RQIH RRL RNSM RRF REM RUSP RCG RLE RGD REAL RC2 RMP RLH RRR REDT RDF RHL RHM RED RPT RGT RGM RGS GMX RENE RNWH REH WIND RSOX RIIG RST RTG RHEP RIC RBN RSI RKH ROM ROL RXP RTC RUBI RES RUR RWS SNT SBLM SAC SAF SAG SLE SND SAND SLG SLGB SAR SAVG SCLP SCPA SCEL SDI SSY SGZ SCO SEA SEE SER SRB SQZ SVO SVR SEV SVCA SHG SHRE SCAP SHLP SHOK SIAG STEC SGR SRX SGM SNS SLN SID SIM SNCL SXX SRSP SRE SSV SPL SKHG SKYW SLM SLNG STF SNAK SGO SPFL SRT SSP SOLO SOLG SOMA SOM SBD SPE SORB SOU SAL SPK SEGR SYG SDIC MCAU SRO SPMG SPSM SQS SQB SQBW SPPC SDM STAF STA SGI SVE SOG STEL STCM SEY SGG SAPO STL STM STT STR SNRP STI STV STVW STTM SUMM SKR SRES SC. STK SCE SUN SUH SWL SWJ SWP SLV SYM SNG SYNC SAM SYN SYS TAIH TTV TPF TND TAN TNG TNZ TAST TAU TAW TEG TJI TEF TCM TIL TAL TEX TCF THG TYM THAL THB TFL TQC THR TFW TIR TIK TMW TNCS TNCI TRX TSW TAM TAMW TXR TMT TMC TOL TLDH TOT TLY TTNA TTNM TOU TMZ TRP TOYE TRCS TRE TRAK TBI TSG TRT TVZ TRV TSTR TRIC TCN TRC TPJ TSTL TPS TRBO TVCH TWE TWEW TXO TYRU TYR UBC UKR UTN UFG ULT UEP UCP UCG UNG UVEL UEN URA UEM VPP VAL VCF VML VGM VELO VEL VMP VRP VVS VTU VIY VOG VNH VNI VPF VOF VNL VDN VIP VIR VOC VIS VGAS VLE VPHA VYKE WHI WALG WGB WAS WTH WATR WET WFC 2020 TWL WTI WEB WPR WEST WTN WHL WSG WTE WST WFCA WBN WORK WSI WKS WOR WSPR WREN WYG WYN WSP XCAP XEL XCT XGT XGTA XTR XXIC YCI YCO YGH YOU YNGA YNGN YUJ ZMNO ZIOC ZEN ZTR ZOX ZOO ZYT

Have some fun with that lot!!!

Ever wonder what all the directories in linux are for? Well here's how to find out...

2012-04-03T12:25:00.000+01:00

Take a read through this and you'll be a wise ol' owl by the end of it.

http://www.pathname.com/fhs/pub/fhs-2.3.html

Cant transfer music to my ipod with linux using Rhythmbox or Banshee

2012-04-03T03:46:00.000+01:00

If you've ever experienced the incredibly frustrating situation where your ipod show up on the desktop, but no matter what you try, you simply can't transfer files to it. Its enough to make you scream - and wonder why you ever thought buying an apple devise was a good idea.

Well its good that you came here, because there IS a solution. And its not hard to implement.

First off you need to establish the UUID (Universally Unique IDentifier) of your device.

ls -l /dev/disk/by-uuid

Once you have established your ipod's UUID, you can now add an entry to your systems fstab file, usually located here: /etc/fstab

The format you want is this:

UUID=DEVICE_UUID_HERE      /media/iPod     auto  rw,user,noauto  0   0

*You want to use UUID because /dev/sdX is not constant and may change when pluging other devices.

Then create the mount point:

mkdir /media/iPod

And finally remove the ipod and reconnect it and Voilà!

More ways to find out what version of Linux you are using....

2012-03-18T08:22:00.001+00:00

There are a lot of possible reasons why Ubuntu user may want to find out Ubuntu version installed on his or her computer. And this is not due to short-term memory or something. Many Ubuntu newbies just feel lost in all those Ubuntu codenames e.g. Lucid Lynx or Maverick Meerkat and version numbers like 10.04 LTS, 10.10 etc. There are several ways to find out what Ubuntu version is installed on a computer/laptop. See them below in this post.

The easiest way to get Ubuntu version and codename is to open Ubuntu menu –> System –> About Ubuntu. It will show version number of running that is usually enough for newbies:

Find out Ubuntu version using Command Line
In order to use one of the following ways to identify Ubuntu version you have to open Terminal (go to Ubuntu main menu –> Accessories –> Terminal):

cat /etc/issue

cat /etc/issue.net

This will show Ubuntu version number but without codename:

Ubuntu 10.04.1 LTS

Here is another command for the same purpose:

lsb_release -a

Sample output (taken at my Ubuntu Lucid Lynx):

Distributor ID: Ubuntu
Description: Ubuntu 10.04.1 LTS
Release: 10.04
Codename: lucid

This one shows complete information about version of Ubuntu you run at your computer including codename and release number.

Delete empty directories using linux

2012-03-09T09:35:00.001+00:00

Not sure how easy this is with Windows, but on Linux, if you want to delete all empty directories in the current path, just type this:

find -depth -type d -empty -exec rmdir {} \;

How to set your screen to go blank after X seconds on linux

2012-02-23T21:07:00.000+00:00

So lets say you use your laptop at night, and you want to leave it on, but have the screen go blank, how to do you get it to do that? Really easy actually. Type this command into your terminal and the screen will go blank after 10 seconds.

$ sudo xset s blank
$ sudo xset s 10

Lots more information about screen blanking here

Could not find a JavaScript runtime?

2012-02-23T02:27:00.000+00:00

If you get the "Could not find a JavaScript runtime" error when attempting to run a rails app using the foreman gem on ubuntu then its a simple fix:

$ sudo apt-get install nodejs

That will get you up and running...