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Monday, September 24, 2012

News: Unusual commands in linux : pv

Today I will speak about pv command.
Pipe viewer - pv is a terminal-based tool for monitoring the progress of data through a pipeline written by Andrew Wood
To install pv on Fedora or CentOS do this:
$ sudo yum install pv
You can read the man file to get more help:
man pv
The result is:
NAME
       pv - monitor the progress of data through a pipe

SYNOPSIS
       pv [OPTION] [FILE]...
       pv [-h|-V]

DESCRIPTION
       pv  allows  a  user  to see the progress of data through a pipeline, by
       giving information such as time  elapsed,  percentage  completed  (with
       progress  bar),  current  throughput  rate, total data transferred, and
       ETA.

       To use it, insert it in a pipeline  between  two  processes,  with  the
       appropriate  options.  Its standard input will be passed through to its
       standard output and progress will be shown on standard error.
Let's see some examples.
You can get precise time how long it will take.
$ pv voronoi.py | python 
 737B 0:00:00 [86.9kB/s] [==================================>] 100%
You can see how fast the computer reads from /dev/zero.
$ pv /dev/zero > /dev/null
1.1GB 0:00:05 [   2GB/s] [    <=>                                            ]
You can use the dialog to show a progress bar.
To do this you need to use -n arg.
$ (pv -n /dev/zero > /dev/null) 2>&1 | dialog --gauge "Please wait" 10 70 0

Wednesday, September 19, 2012

Make one simple kernel module using C programming language.

Today I will try to explain how to make a kernel module.
Basically, a kernel module it's one piece of code that can be loaded and unloaded into the kernel.
You can read about kernel modules from here.
Now, let's try to make a simple kernel module.
Writing your own module can be done if you know some basic rules.
First, about how to use modules.
Suppose you have a new module named kernelmoduletest.
How to load the module.
Just use this command in your module kernel folder:
#insmod kernelmoduletest.ko
Next, test the kernel module messages.
This can be done with:
#dmesg | tail
Also, you need to remove the kernel module.
$ rmmod kernelmoduletest 
ERROR: Removing 'kernelmoduletest': Operation not permitted
This means you need to have superuser rights. So use the sudo or su command.
Then use the rmmod command.
Know how to make the kernel module skeleton.
This is not very simple because you need to know many things about kernel and programming.
But you can try the test with some simple example like this example:
Create the c file named kernelmoduletest and add this source code:
#include <linux module.h="">
#include <linux kernel.h="">

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("kernelmoduletest");
MODULE_AUTHOR("Catalin George Festila/mythcat/catafest");

int init_module() {

    printk(KERN_INFO "Now I will initialize my  kernel module\n");

    printk(KERN_INFO "Test: Hello World !\n");

    return 0;
}

void cleanup_module() {

    printk(KERN_INFO "Bad!... kernel module unloaded.\n");
}</linux></linux>
Make a new file named Makefile.
Add this to tell how to compile the kernel module.
obj-m += kernelmoduletest.o
all:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
Compile your kernel module
Just use make command.
# make
...
  Building modules, stage 2.
  MODPOST 1 modules
...
make[1]: Leaving directory `/usr/src/linux-headers-2.6.31-14-generic'
If you test your module using the commands from the top of this tutorial, you can see that:

[14694.779227] Now I will initialize my  kernel module
[14694.779233] Test: Hello World !
[15049.825605] Bad!... kernel module unloaded.
If you have already made kernel modules and the subject it's interesting for you, send me an email.
Thank you. Regards.

Sunday, September 2, 2012

News: Tips and tricks: watch and cat.

Sometimes it is necessary to find solutions.
Today's example involves two Linux commands:
watch and cat
Here is a simple method by creating a script that returns an output:
while [ 1 ]; do cat /proc/meminfo; date; echo; sleep 1; done
Make this script executable and name it: meminfo.
The output is then processed by the command:
$ watch -d ./meminfo 
This simple method can be applied to other files ...

Thursday, August 30, 2012

Using SL4A bash shell script to connect Linux with Android tablet .

Using Linux with Android OS is very simple.
I install the next two android application: sl4a_r6.apk and PythonForAndroid-r7b1.apk.
Use the PythonForAndroid-r7b1.apk just if you want to write some python scripts.
We can download it from here.
The first: sl4a_r6 it's used to write and run scripts like bash shell, HTML, Java, Python.
With this, the SL4A provides and make APIs available via JSON RPC calls.
The PythonForAndroid-r7b1 allow you to install python modules...
We can read more on this website.
Let's start with one simple bash shell script.
We will make a shell script to test the connection between Linux and Android tablet.
The connection will be through a wireless router that has opened the port through which the communication.
Tablet has Android 4.0.
We use the Linux command NC, see: nc command.
This is the script on the tablet and it will run first.
nc -l -p 7000
See the next image:

Button 1 - run the script
Button 2 - edit the script
Button 3 - save the script
Button 4 - remove the script
Use the next command with your IP on the Linux terminal.
nc xxx.xxx.xxx.xxx 7000
If you type something in your terminal you will see on a tablet.
The input from my linux terminal can be seen in the next image:

Ant this is the output on my tablet.

We can test multiple features of command nc.
I'm just curious if you have some new ideas on this subject.

Friday, August 24, 2012

News: New GTK3 theme make your Linux to look like an Android

The new GTK3 theme inspired by Android will make your Linux nicer.
reNIX Gnome Shell theme: [link]
reNIX (for Chrome/Chromium): [link]

Tuesday, August 14, 2012

News: About light laptop with your Linux distros.

ZaReason is launching a thin and light laptop called the UltraLap 430.
Linux computer builder has all the specs you’d expect from a modern ultrabook.
Prices start at $899 and it's available now from the ZaReason store.

Features:
  • 14.1" HD (1366x768) Glossy LED Backlit Display
  • 3rd Generation Intel Core Processor
  • Intel HD 4000 Graphics
  • Quick performance and power-on times with Solid State Disks
  • HD Stereo Speakers
  • 802.11 B/G/N WiFi included
  • Bluetooth
  • 3 in-1 card reader -- SD/MMC/MS supported
  • 1.3 Megapixel HD webcam included
  • Multi-gesture touchpad
Ports:
  • HDMI port
  • Gigabit Ethernet port
  • Kensington lock port
  • Headphone/Mic Jack
  • 2 USB 3.0 ports
  • 1 USB 2.0 port
Specs:
  • Your choice of a variety of Open Source operating systems, like Fedora 17
  • Battery Life: Up to 6 hrs
  • Dimensions (WxDxH): 13.5in x 9.25in x .75in
  • Weight: ~3.5 lbs

Friday, August 10, 2012

News: Google Translate Android can translate from pictures.

News about Google Translate Android.
Use camera to take a picture and brush text to translate - available on Android 2.3 and above.
Get instant translation results as you type.
Choose dialect preference for speech input.
Japanese handwriting now recognizes multiple characters at once.
Added access network state permission to check network availability when sending requests.
Try this on play.google.com