Author Archives: jontas

About jontas

I like to make things that people find useful.

MYSQL Creating several UUIDs at one single time

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I recently ran into the problem that I had too add two rows to a database that uses a UUID (in this case converted to a binary) as a key.
The problem I had was that running two insert statements after each other (just separated by “;”) then the same id was generated.
A workaround I have found is to sleep for a second between the two statements.

Examples (using SELECT instead of INSERT):
Getting the same id twice

SELECT UNHEX(REPLACE(UUID(),'-','')) AS uuid1,  UNHEX(REPLACE(UUID(),'-','')) AS uuid2;
-- Shows: "849392548f1311df91b70019dbd264f1"	"849392908f1311df91b70019dbd264f1"

Adding a sleep to get different ids

SELECT UNHEX(REPLACE(UUID(),'-','')) AS uuid1, SLEEP(1), UNHEX(REPLACE(UUID(),'-','')) AS uuid2
-- Shows: "3901c1928f1511df91b70019dbd264f1"	"0"	"399a5b148f1511df91b70019dbd264f1"

And another one using INSERTS

INSERT INTO testTable (id) VALUES (UNHEX(REPLACE(UUID(),'-','')));
SLEEP(1);
INSERT INTO testTable (id) VALUES (UNHEX(REPLACE(UUID(),'-','')));

PHP: Converting a bool value to a string value

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The first idea that comes into mind for doing this is to simply make a typecast of the boolean variable to a string and use that (which works)

$testVar = false;
echo (string)$testVar; //will output a empty string (as that evaluates to false)
$testVar = true;
echo (string)$testVar; //will output 1 (as that evaluates to true)

but what if the requirement is that the string should say true or false

$testVar = false;
echo $testVar ? 'true' : 'false'; //will output false
$testVar = true;
echo $testVar ? 'true' : 'false'; //will output true

(While the above example might seam useless I recently had to do this for a db insert)

Disable (or change) the Click sound in Internet Explorer or Windows Explorer

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When you open a folder in Windows Explorer a click sound is played. To disable this there are two ways to do it:

  • Turn it off using the control panel:
    1. Open “Start”->”Settings”->”Control Panel”
    2. Open up “Sounds and Audio Devices”
    3. Open the tab that says “Sounds”
    4. Scroll down until you find “Windows Explorer”->”Start Navigation”
    5. When you mark this line at the bottom there is a drop down that is labeled “Sounds:” Here you should be able to change to anther sound or “none” if you do not wish a click.
  • The second option is a bit more direct and rude – but if the above does not work for you (for me something kept resetting the old sound); just remove the file that contains the click sound.
    1. Open up a Windows Explorer and go to “%windir%\Media” and find the file that is named “Windows XP Start.wav”
    2. Either remove it (permanently) or rename it to something that windows won’t recognize (but you can – so you later can reverse this if you would like to)

Different line-endings on diffrent OS

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Windows, Linux/Unix and Mac have different line-endings on text files.

A quick overview on the endings are:

  • Windows-style line endings are CRLF ( \r\n or hex 0D0A )
  • Mac-style line endings are CR ( \r or hex 0D )
  • Unix-style line endings are LF ( \n or hex 0A )

A HEX editor can be used to double check that the correct endings are written.

Pine: Flags

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To mark a message as unread in pine this can be done using flags.
First flags have to be turned on in setup
[M]ain [S]etup [C]onfig
Then find “enable-flag-cmd” and turn it on.
After this marking a message as unread is done by “* N” in the list view or when looking at the message.

All the flags are:

  • [N]New
  • [D]Deleted
  • [*] Important
  • [A] Answered

[^T] Can be used to see all the flags and set/unset them one by one (or all).

PHP: Static functions in a Class

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Static functions can be used without instantiating the object.

A quick example of a static function is shown below as well as a comparison with a non static function.

A quick example of this (in PHP5):

class TestClass{
	static function staticFunction(){
		echo "static function called";
	}
 
	function nonStaticFunction(){
		echo "nonstatic function was called";
	}
}
 
TestClass::staticFunction(); //will echo static function called
 
$testClass = new TestClass();
$testClass.nonStaticFunction(); //will echo nonstatic function was called
unset($testClass);

PHP: converting a uuid stored as BINARY(16) in mysql to RFC 4122 format

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If you are storing uuid’s are BINARY(16) in the database, then the following will turn the stored id to the “original” format.

$uuidReadable = unpack("h*",$uuid);
$uuidReadable = preg_replace("/([0-9a-f]{8})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{12})/", "$1-$2-$3-$4-$5", $uuidReadable);
$uuidReadable = array_merge($uuidReadable);
echo "uuid is " . $uuidReadable[0];

MySQL inserting UUID to a binary(16) field

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It is advantageous to store a UUID (acc to RFC 4122) in a binary(16) field in the database.
It is not hard to create such a table and to insert data into it.

CREATE TABLE IF NOT EXISTS test_table (
  id BINARY(16) NOT NULL,
  name VARCHAR(128) NOT NULL,
  PRIMARY KEY  (id)
) 
 
INSERT INTO test_table (id, name) VALUES
(UNHEX(REPLACE(UUID(),'-','')), 'test1'),
(UNHEX(REPLACE(UUID(),'-','')), 'test2'),
(UNHEX(REPLACE(UUID(),'-','')), 'test3')

apt-get WARNING: The following packages cannot be authenticated!

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apt-get is verifying the packages before installing them.
If the keys are not up to date, then apt-get upgrade will issue a warning.

WARNING: The following packages cannot be authenticated!
  ure uno-libs3
Install these packages without verification [y/N]?

The way to solve this is rather simple, just run apt-get update and it should download the keys automatically.

apt-key handles keys, using apt-key list will show you the keys that are on the computer.