Category: Technology

Today, I bought a Bluetooth 4.0 dongle to connect my Logitech K760 keyboard. But I could not get it working with my Ubuntu system. Initially, I thought the Bluetooth adaptor does not support Ubuntu, as the product description says it only supports Windows… But lsusb shows the below output, which to me does not look like an OS issue.

xinquan@:~$ lsusb 
Bus 002 Device 003: ID 03f0:0324 Hewlett-Packard SK-2885 keyboard
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 007: ID 0b95:772a ASIX Electronics Corp. AX88772A Fast Ethernet
Bus 001 Device 006: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)

After attempting to connect via the Bluetooth GUI, it gave me a passcode to type in on my wireless keyboard, which I proceed to do. It immediately gave me this error: ‘Logitech K760 failed to connect’.

 

After some googling, it turns out that the passcode from the Bluetooth GUI was bogus, the correct passcode can be obtained from the command tool hcidump! Goshi… After I typed the passcode from hcidump, it connected successfully!

sudo apt-get install bluez-hcidump
sudo hcidump -at | grep -A 1 "User Passkey"

2015-03-27 11:29:29.787512 > HCI Event: User Passkey Notification (0x3b) plen 10
    bdaddr 00:1F:20:3E:53:A2 passkey 359872

For an hour or so, I have been debugging an SQL error thrown by the PostgresSQL in my CakePHP application. The error message was also not really helpful. Below is the SQL generated by the CakePHP update function

UPDATE "public"."posts" SET "value" = asap WHERE id = (1) 


SQLSTATE[42703]:
Undefined column: 7 ERROR: column "asap" does not exist LINE 1:


The culprit turns out to be that how quote is used to identify a string in SQL.
I have to explicitly put the single quote in the string value ‘asap’ in the CakePHP function below when updating a record of the Model Post.

The below is the signature of the updateAll function from CakePHP library.

public function updateAll($fields, $conditions);

The tricky part is you can’t quote strings in the conditions, but for the updating value of the fields, the string has to be single quoted.

     $this->Post->updateAll(
       array('Post.value' =>  "'asap'" ),
       array('Post.key = ' => "when"));

A further discussion can be seen at the stackoverflow page
http://stackoverflow.com/questions/1992314/what-is-the-difference-between-single-and-double-quotes-in-sql

Today, I discovered a great tool called “casperjs”, which allows you to test your website with Headless WebKit. Having just tried a few minutes, I instantly fall in love with this tool. You can use it to simulate almost any browser behavior.

Installing it on ubunutu is quite straightforward.

 

#clone the repository from the master branch
git clone git://github.com/n1k0/casperjs.git

#Symlink the relevant file into your bin or /usr/local/bin
ln -sf ~/repositories/casperjs/bin/casperjs /bin/casperj
ln -sf ~/repositories/casperjs/bin/casperjs /usr/bin/casperj