FLX » Code Snippet of the Week http://flx.me rambles, code and science! Tue, 09 Mar 2010 12:47:09 +0000 en hourly 1 http://wordpress.org/?v=abc Command line snippet of the week: 3 http://flx.me/command-line-snippet-of-the-week-3/ http://flx.me/command-line-snippet-of-the-week-3/#comments Thu, 21 Jan 2010 13:59:35 +0000 FLX http://flx.me/?p=597 Wouldn’t it be nice to check if a program is running? You can do that and make it start conditionally if it isn’t running. Very handy for service daemons that always need to be running. Can be used with cron as well:

ps -C servicedaemon || { servicedaemon & }

Replace servicedaemon with your own process that needs to be checked. The second servicedaemon value describes what program it needs to start if it’s not running.

]]> http://flx.me/command-line-snippet-of-the-week-3/feed/ 0 Command line snippet of the week: 2 http://flx.me/command-line-snippet-of-the-week-2/ http://flx.me/command-line-snippet-of-the-week-2/#comments Thu, 14 Jan 2010 13:34:47 +0000 FLX http://flx.me/?p=593 The snippet this week will be about copying arguments without retyping everything. It would be easier to show you how this works:

$ cd /home/user/flx
cd: /home/user/flx: No such file or directory
$ mkdir !*
mkdir /home/user/flx

By using !* it repeats all arguments previously used. If you only want to use the second argument for example, you use !:2.

]]> http://flx.me/command-line-snippet-of-the-week-2/feed/ 0 Command line snippet of the week: 1 http://flx.me/command-line-snippet-of-the-week-1/ http://flx.me/command-line-snippet-of-the-week-1/#comments Thu, 07 Jan 2010 13:32:15 +0000 FLX http://flx.me/?p=590 New year, new snippets! Belated good wishes from me as well :-)

Anyway, this week’s snippet is on basic steganography. In this case we would like to hide a rar file in a image, we can do that by doing the following:

cat picture.png archive.rar > hidden_archive_in_pic.png

This will create a valid png image for viewing with a secret rar file inside!
When you want to retrieve the hidden files, download the image, rename to .rar and extract.

]]> http://flx.me/command-line-snippet-of-the-week-1/feed/ 0 Command line snippet of the week: 53 http://flx.me/command-line-snippet-of-the-week-53/ http://flx.me/command-line-snippet-of-the-week-53/#comments Thu, 31 Dec 2009 14:00:39 +0000 FLX http://flx.me/?p=303 Last one of this year!

Need to mass extract several RAR archives from different folders? Create a file called “massunrar” in /usr/bin and paste the following content:

find . -type f -name *.r01 -exec unrar e {} \;
find . -type f -name *.part01.rar -exec unrar e {} \;
echo "Found files:"
find . -type f -name *.r01
find . -type f -name *.part01.rar

Be sure to chmod “massunrar” to make it executable:

chmod +x /usr/bin/massunrar

Run “massunrar” in the parent folder to let it search for rar files in all subdirectories and extract them.
More to follow next year!

]]> http://flx.me/command-line-snippet-of-the-week-53/feed/ 0 Command line snippet of the week: 52 http://flx.me/command-line-snippet-of-the-week-52/ http://flx.me/command-line-snippet-of-the-week-52/#comments Thu, 24 Dec 2009 14:00:19 +0000 FLX http://flx.me/?p=301 Need to have IP location information? Use:

curl -s "http://www.geody.com/geoip.php?ip=$(curl -s icanhazip.com)" | sed '/^IP:/!d;s/<[^>][^>]*>//g'

It returns with your IP information such as:

IP: 13.13.133.713 Location: Amsterdam, NOORD-HOLLAND, Netherlands   (N.V. XS4ALL)

Replace (curl -s icanhazip.com) to show a different IP than your own.

]]> http://flx.me/command-line-snippet-of-the-week-52/feed/ 0 Command line snippet of the week: 51 http://flx.me/command-line-snippet-of-the-week-51/ http://flx.me/command-line-snippet-of-the-week-51/#comments Thu, 17 Dec 2009 14:00:23 +0000 FLX http://flx.me/?p=297 Need to empty a file fast? Try:

> file.txt

Shortest emptier in town!

]]> http://flx.me/command-line-snippet-of-the-week-51/feed/ 0 Command line snippet of the week: 50 http://flx.me/command-line-snippet-of-the-week-50/ http://flx.me/command-line-snippet-of-the-week-50/#comments Thu, 10 Dec 2009 14:00:40 +0000 FLX http://flx.me/?p=293 command_with_insufficient_permissions Permission denied sudo !! The !! parameter repeats the previous command, thus no need to retype! Source: shell-fu]]> Forget that your running as underprivileged? No need to retype the command:

> command_with_insufficient_permissions
Permission denied

sudo !!

The !! parameter repeats the previous command, thus no need to retype!

Source: shell-fu

]]> http://flx.me/command-line-snippet-of-the-week-50/feed/ 0 Command line snippet of the week: 49 http://flx.me/command-line-snippet-of-the-week-49/ http://flx.me/command-line-snippet-of-the-week-49/#comments Thu, 03 Dec 2009 14:00:57 +0000 FLX http://flx.me/?p=291 Want to show something on your machine to someone over the web? Don’t copy it or upload it somewhere, try this command (requires Python):

alias webshare='python -c "import SimpleHTTPServer;SimpleHTTPServer.test()"'

Just run “webshare” and the current directory and everything beneath it will be served from a new web server listening on port 8000. When you are finished, just hit control-c to close the webserver.

]]> http://flx.me/command-line-snippet-of-the-week-49/feed/ 0 Command line snippet of the week: 48 http://flx.me/command-line-snippet-of-the-week-48/ http://flx.me/command-line-snippet-of-the-week-48/#comments Thu, 26 Nov 2009 14:05:22 +0000 FLX http://flx.me/?p=287 Hate having to remember all switches for each different unpacker? You can fix that!
Create a new file in /usr/bin/ called “extract” and paste the following code:

if [ -f $1 ] ; then
case $1 in
    *.tar.bz2)   tar xvjf $1        ;;
    *.tar.gz)    tar xvzf $1     ;;
    *.bz2)       bunzip2 $1       ;;
    *.rar)       unrar x $1     ;;
    *.gz)        gunzip $1     ;;
    *.tar)       tar xvf $1        ;;
    *.tbz2)      tar xvjf $1      ;;
    *.tgz)       tar xvzf $1       ;;
    *.zip)       unzip $1     ;;
    *.Z)         uncompress $1  ;;
    *.7z)        7z x $1    ;;
    *)           echo "'$1' cannot be extracted via &gt;extract&lt;" ;;
esac
else
echo "'$1' is not a valid file"
fi

be sure to chmod it to executable:

chmod +x /usr/bin/extract

This code will save you time by extracting almost any kind of archive by using the command:

extract my_awesome_archive.tar.gz
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