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Basic Knowledge of Regular Expression

Recently I begin  to figure regular expression is really useful but hard to remember.
So this is just a tip for reviewing some basic knowledge about  javascript RegExp.

First  here is a link of W3school http://www.w3schools.com/jsref/jsref_obj_regexp.asp

And this link is for tesing http://www.regular-expressions.info/javascriptexample.html

if we want to find “test” in the string “give us a test and ” we can just use the javascript regex like this:

regex=test or regex =bt[a-z]+b or bt[a-z]{3}b  or bt[a-z]{1,3}

First one will directly find the result of “test”. The second one will find a string with the beginning of t and followed by at least one letter between a-z. The third one is to find a string beginning with t and followed by 3 letters.  The last one is to  find a string beginning with t and follow by some letters. The number of letters is  1 or 2 or 3.

Beside the most important thing when we try to avoid deadly command in webpage is to check whether this is a “;” or not.
Because “;” will give the right to use another command.
When we want to execute linux  command by using node.js,we need to be more careful about the security problem.Sometimes, there will be a error message like”fail to find the command”.
The best way to solve it is to use the direct path.For example: $which ssmtp
And it will show the path of that command ,then :/usr/bin/ssmtp ” + inviteEmail + ” </home/msg.txt
The command will be executed successfully.

And by the way,when we want to use regex in javascript, we should add “//”.
For example, “regex = /;/; “

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Class and functions in PHP

Today,I had a very interesting experience about PHP.
Here is a question about FizzBuzz:
Fizz Buzz
The aim of this test is to implement the FizzBuzz problem.
FizzBuzz is defined for the “natural numbers” (numbers greater than zero) as:
When divisible by 3, you should return “Fizz”.
When divisible by 5, you should return “Buzz”.
When divisible by both 3 and 5, you should return “FizzBuzz”.
When divisible by neither, you should return the number itself.
The test is expected to take around 10 minutes. When you are ready to take it, please follow the link below:
This test will require you to solve the exercise in the Php programming language.

Actually this is an easy question. The only thing you need is if and elseif.

However,when I clicked the link of this question. I realized that I was wrong.

The test program requires a class of PHP. To be honest ,this is the first time I know that class is important in PHP program. In my undergraduate study I never had an opportunity to use class in PHP.

As a result,I had to google some information about class and finally completed the exercise after 1 hour…

Here is some tips about this question:

1.class in PHP

some time we will use class to solve problem. It is common to use a class like that:
$fizzbuzz=fizz(10);
10 is the value of input and fizz() will return a value to $fizzbuzz.

2. __construct()

This is a really common function. You can not use it as a normal function in class. The main responsibility for this function is to declare values.
For example:

function _construct($number){
    $this->number=$number;
} 

3.Magic methods
Today I have to use one of the magic methods:_tostring()
This function is used when the class is treated as a string.That is to say,we can only return values in string type.
Here is an example:

function _tostring(){
   echo ‘Hello,world!’;
}

Sometimes we have to use it to return some integer.Then we will have to use another important point. We need to change the integer into string.
For example:

echo (string)$number;

Actually,this exercise is really useful and I have learned a lot from it,although
I may have lost the opportunity for interview…
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Shell commands under linux is interesting

I began to learn some basic knowledge about shell especially bash. At first it is strange but it is really important.Besides I also need to review Java because I may have to use Java to get a summer holiday job in the future.

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How to use Issh

I have got the account of CSE, that is to say I could use lads in my university. It was easy to  active the Yellow FORM of CSE and finally receive my password.Then I tried to connect my ipad to CSE’s computer.As it was the first time I knew Issh ,it was a totally disaster at beginning. I had to google almost everything about ssh and ‘how to use issh’. Fortunately,I got it.
The following is the process of how to use Issh
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As u can see,this is the interface of issh and the first thing we need to do is clicking the Add Configuration
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Here we can see,there is a list which should be filled with.The first one is Description,and you could just write down whatever you like because it is just a mark.Next step is to write the host.Host is the aim computer and you should figure out the IP of the aim computer.
Port should be default for beginer and login is your user name.Password is the last step.
Then click the save button.
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you will find your configuration in the middle,click it
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successfully!now you could  try a command ,what about top?
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commands are really usefully~