Programs & Examples On #Signing

A digital signature is a mathematical scheme for demonstrating the authenticity of a digital message or document.

Difference between signature versions - V1 (Jar Signature) and V2 (Full APK Signature) while generating a signed APK in Android Studio?

It is a new signing mechanism introduced in Android 7.0, with additional features designed to make the APK signature more secure.

It is not mandatory. You should check BOTH of those checkboxes if possible, but if the new V2 signing mechanism gives you problems, you can omit it.

So you can just leave V2 unchecked if you encounter problems, but should have it checked if possible.

UPDATED: This is now mandatory when targeting Android 11.

What is the difference between encrypting and signing in asymmetric encryption?

When encrypting, you use their public key to write a message and they use their private key to read it.

When signing, you use your private key to write message's signature, and they use your public key to check if it's really yours.

I want to use my private key to generate messages so only I can possibly be the sender.

I want my public key to be used to read the messages and I do not care who reads them

This is signing, it is done with your private key.

I want to be able to encrypt certain information and use it as a product key for my software.

I only care that I am the only one who can generate these.

If you only need to know it to yourself, you don't need to mess with keys to do this. You may just generate random data and keep it in a database.

But if you want people to know that the keys are really yours, you need to generate random data, keep in it a database AND sign it with your key.

I would like to include my public key in my software to decrypt/read the signature of the key.

You'll probably need to purchase a certificate for your public key from a commercial provider like Verisign or Thawte, so that people may check that no one had forged your software and replaced your public key with theirs.

How to retrieve Key Alias and Key Password for signed APK in android studio(migrated from Eclipse)

In ubuntu, we can find all password related to keystore from the given path.

/home/user/.AndroidStudio2.2(current version)/system/log/idea.log.x(older versions)

edit the file and search android.injected.signing.store , then you can find the passwords.

-Pandroid.injected.signing.store.file= path to your keystore 
-Pandroid.injected.signing.store.password=yourstorepassword
-Pandroid.injected.signing.key.alias=yourkeyalias
-Pandroid.injected.signing.key.password=yourkeypassword

How to sign an android apk file

For users of IntelliJ IDEA or Android Studio make these steps:
* From the menu Build/Generate signed APK
* You need to create a keystore path. From the dialog click Create new. You will create a jks file that includes your keys. Select folder, define a password. So your keystore ok.
* Create new key by for your application by using alias, key password, your name etc.
* Click next.
* From the dialog either select Proguard or not.

Your signed APK file is ready.

Help file: https://www.jetbrains.com/idea/webhelp/generate-signed-apk-wizard.html

How can I add private key to the distribution certificate?

since xcode5 organizer no longer team section exists. but the bold sentence was the answer for me. God thanks there is another mac to restore and import to problemmatic mac. now all is ok.

LINQ equivalent of foreach for IEnumerable<T>

To stay fluent one can use such a trick:

GetItems()
    .Select(i => new Action(i.DoStuf)))
    .Aggregate((a, b) => a + b)
    .Invoke();

More elegant way of declaring multiple variables at the same time

What's the problem , in fact ?

If you really need or want 10 a, b, c, d, e, f, g, h, i, j , there will be no other possibility, at a time or another, to write a and write b and write c.....

If the values are all different, you will be obliged to write for exemple

a = 12
b= 'sun'
c = A() #(where A is a class)
d = range(1,102,5)
e = (line in filehandler if line.rstrip())
f = 0,12358
g = True
h = random.choice
i = re.compile('^(!=  ab).+?<span>')
j = [78,89,90,0]

that is to say defining the "variables" individually.

Or , using another writing, no need to use _ :

a,b,c,d,e,f,g,h,i,j =\
12,'sun',A(),range(1,102,5),\
(line for line in filehandler if line.rstrip()),\
0.12358,True,random.choice,\
re.compile('^(!=  ab).+?<span>'),[78,89,90,0]

or

a,b,c,d,e,f,g,h,i,j =\
(12,'sun',A(),range(1,102,5),
 (line for line in filehandler if line.rstrip()),
 0.12358,True,random.choice,
 re.compile('^(!=  ab).+?<span>'),[78,89,90,0])

.

If some of them must have the same value, is the problem that it's too long to write

a, b, c, d, e, f, g, h, i, j = True, True, True, True, True, False, True ,True , True, True 

?

Then you can write:

a=b=c=d=e=g=h=i=k=j=True
f = False

.

I don't understand what is exactly your problem. If you want to write a code, you're obliged to use the characters required by the writing of the instructions and definitions. What else ?

I wonder if your question isn't the sign that you misunderstand something.

When one writes a = 10 , one don't create a variable in the sense of "chunk of memory whose value can change". This instruction:

  • either triggers the creation of an object of type integer and value 10 and the binding of a name 'a' with this object in the current namespace

  • or re-assign the name 'a' in the namespace to the object 10 (because 'a' was precedently binded to another object)

I say that because I don't see the utility to define 10 identifiers a,b,c... pointing to False or True. If these values don't change during the execution, why 10 identifiers ? And if they change, why defining the identifiers first ?, they will be created when needed if not priorly defined

Your question appears weird to me

MySQL Install: ERROR: Failed to build gem native extension

If you use Percona Mysql server

$ yum install Percona-Server-devel-55

$ gem install mysql

Overflow-x:hidden doesn't prevent content from overflowing in mobile browsers

try

html, body {
  overflow-x:hidden 
} 

instead of just

body {
  overflow-x:hidden 
}

Change the color of a checked menu item in a navigation drawer

Here is the another way to achive this:

public boolean onOptionsItemSelected(MenuItem item) {

    int id = item.getItemId();

    item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
        @Override
        public boolean onMenuItemClick(MenuItem item) {
            item.setEnabled(true);
            item.setTitle(Html.fromHtml("<font color='#ff3824'>Settings</font>"));
            return false;
            }
        });


    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

}

Using Google Text-To-Speech in Javascript

I don't know of Google voice, but using the javaScript speech SpeechSynthesisUtterance, you can add a click event to the element you are reference to. eg:

_x000D_
_x000D_
const listenBtn = document.getElementById('myvoice');

listenBtn.addEventListener('click', (e) => {
  e.preventDefault();

  const msg = new SpeechSynthesisUtterance(
    "Hello, hope my code is helpful"
  );
  window.speechSynthesis.speak(msg);

});
_x000D_
<button type="button" id='myvoice'>Listen to me</button>
_x000D_
_x000D_
_x000D_

Display image at 50% of its "native" size

This should work:

img {
    max-width: 50%;
    height: auto;
}

Any free WPF themes?

I bought a theme from www.xamltemplates.net. The themes ship with source code so you can tweak them. They also offer a free theme (source code included).

How to hide element using Twitter Bootstrap and show it using jQuery?

?? The righter answer

In Bootstrap 4 you hide the element:

<p id="insufficient-balance-warning" class="d-none alert alert-danger">Pay me</p>

Then, sure, you could literally show it with:

if (pizzaFundsAreLow) {
  $('#insufficient-balance-warning').removeClass('d-none');
}

But if you do it the semantic way, by transferring responsibility from Bootstrap to jQuery, then you can use other jQuery niceties like fading:

if (pizzaFundsAreLow) {
  $('#insufficient-balance-warning').hide().removeClass('d-none').fadeIn();
}

With CSS, how do I make an image span the full width of the page as a background image?

If you're hoping to use background-image: url(...);, I don't think you can. However, if you want to play with layering, you can do something like this:

<img class="bg" src="..." />

And then some CSS:

.bg
{
  width: 100%;
  z-index: 0;
}

You can now layer content above the stretched image by playing with z-indexes and such. One quick note, the image can't be contained in any other elements for the width: 100%; to apply to the whole page.

Here's a quick demo if you can't rely on background-size: http://jsfiddle.net/bB3Uc/

MySQL JOIN with LIMIT 1 on joined table

Another example with 3 nested tables: 1/ User 2/ UserRoleCompanie 3/ Companie

  • 1 user has many UserRoleCompanie.
  • 1 UserRoleCompanie has 1 user and 1 Company
  • 1 Companie has many UserRoleCompanie
SELECT 
u.id as userId, 
u.firstName,
u.lastName,
u.email,
urc.id ,
urc.companieRole,
c.id as companieId,
c.name as companieName
FROM User as u 
JOIN UserRoleCompanie as urc ON u.id = urc.userId
    AND urc.id = (
        SELECT urc2.id
        FROM UserRoleCompanie urc2 
        JOIN Companie ON urc2.companieId = Companie.id
        AND urc2.userId = u.id 
        AND Companie.isPersonal = false
        order by Companie.createdAt DESC
        
        limit 1
    )
    
LEFT JOIN Companie as c ON urc.companieId = c.id
+---------------------------+-----------+--------------------+---------------------------+---------------------------+--------------+---------------------------+-------------------+
| userId                    | firstName | lastName           | email                     | id                        | companieRole | companieId                | companieName      |
+---------------------------+-----------+--------------------+---------------------------+---------------------------+--------------+---------------------------+-------------------+
| cjjt9s9iw037f0748raxmnnde | henry     | pierrot            | [email protected]           | cjtuflye81dwt0748e4hnkiv0 | OWNER        | cjtuflye71dws0748r7vtuqmg | leclerc           |

Multiline editing in Visual Studio Code

Use Ctrl + D to use multi word edit of same words in Windows and Linux.

Use CMD + D for Mac.

How to determine if a string is a number with C++?

Why reinvent the wheel? The C standard library (available in C++ as well) has a function that does exactly this:

char* p;
long converted = strtol(s, &p, 10);
if (*p) {
    // conversion failed because the input wasn't a number
}
else {
    // use converted
}

If you want to handle fractions or scientific notation, go with strtod instead (you'll get a double result).

If you want to allow hexadecimal and octal constants in C/C++ style ("0xABC"), then make the last parameter 0 instead.

Your function then can be written as

bool isParam(string line)
{
    char* p;
    strtol(line.c_str(), &p, 10);
    return *p == 0;
}

How to convert object to Dictionary<TKey, TValue> in C#?

this should work:

for numbers, strings, date, etc.:

    public static void MyMethod(object obj)
    {
        if (typeof(IDictionary).IsAssignableFrom(obj.GetType()))
        {
            IDictionary idict = (IDictionary)obj;

            Dictionary<string, string> newDict = new Dictionary<string, string>();
            foreach (object key in idict.Keys)
            {
                newDict.Add(key.ToString(), idict[key].ToString());
            }
        }
        else
        {
            // My object is not a dictionary
        }
    }

if your dictionary also contains some other objects:

    public static void MyMethod(object obj)
    {
        if (typeof(IDictionary).IsAssignableFrom(obj.GetType()))
        {
            IDictionary idict = (IDictionary)obj;
            Dictionary<string, string> newDict = new Dictionary<string, string>();

            foreach (object key in idict.Keys)
            {
                newDict.Add(objToString(key), objToString(idict[key]));
            }
        }
        else
        {
            // My object is not a dictionary
        }
    }

    private static string objToString(object obj)
    {
        string str = "";
        if (obj.GetType().FullName == "System.String")
        {
            str = (string)obj;
        }
        else if (obj.GetType().FullName == "test.Testclass")
        {
            TestClass c = (TestClass)obj;
            str = c.Info;
        }
        return str;
    }

How to represent matrices in python

Take a look at this answer:

from numpy import matrix
from numpy import linalg
A = matrix( [[1,2,3],[11,12,13],[21,22,23]]) # Creates a matrix.
x = matrix( [[1],[2],[3]] )                  # Creates a matrix (like a column vector).
y = matrix( [[1,2,3]] )                      # Creates a matrix (like a row vector).
print A.T                                    # Transpose of A.
print A*x                                    # Matrix multiplication of A and x.
print A.I                                    # Inverse of A.
print linalg.solve(A, x)     # Solve the linear equation system.

Get JSONArray without array name?

JSONArray has a constructor which takes a String source (presumed to be an array).

So something like this

JSONArray array = new JSONArray(yourJSONArrayAsString);

Func delegate with no return type

All Func delegates return something; all the Action delegates return void.

Func<TResult> takes no arguments and returns TResult:

public delegate TResult Func<TResult>()

Action<T> takes one argument and does not return a value:

public delegate void Action<T>(T obj)

Action is the simplest, 'bare' delegate:

public delegate void Action()

There's also Func<TArg1, TResult> and Action<TArg1, TArg2> (and others up to 16 arguments). All of these (except for Action<T>) are new to .NET 3.5 (defined in System.Core).

Using a string variable as a variable name

You can use setattr

name  = 'varname'
value = 'something'

setattr(self, name, value) #equivalent to: self.varname= 'something'

print (self.varname)
#will print 'something'

But, since you should inform an object to receive the new variable, this only works inside classes or modules.

How do you UDP multicast in Python?

Have a look at py-multicast. Network module can check if an interface supports multicast (on Linux at least).

import multicast
from multicast import network

receiver = multicast.MulticastUDPReceiver ("eth0", "238.0.0.1", 1234 )
data = receiver.read()
receiver.close()

config = network.ifconfig()
print config['eth0'].addresses
# ['10.0.0.1']
print config['eth0'].multicast
#True - eth0 supports multicast
print config['eth0'].up
#True - eth0 is up

Perhaps problems with not seeing IGMP, were caused by an interface not supporting multicast?

Why can't I reference my class library?

This sounds like a similar issue with ReSharper:

http://www.jetbrains.net/devnet/thread/275827

According to one user in the thread forcing a build fixes the issue (CTRL+Shift+B) after the first build..

Sounds like an issue with ReSharper specifically in their case.. Have you tried building regardless of the warnings and possible false errors?

Nginx no-www to www and www to no-www

not sure if anyone notice it may be correct to return a 301 but browsers choke on it to doing

rewrite ^(.*)$ https://yoursite.com$1; 

is faster than:

return 301 $scheme://yoursite.com$request_uri;

How to write/update data into cells of existing XLSX workbook using xlsxwriter in python

If you have issue with writing into an existing xls file because it is already created you need to put checking part like below:

PATH='filename.xlsx'
if os.path.isfile(PATH):
    print "File exists and will be overwrite NOW"
else:
    print "The file is missing, new one is created"

... and here part with the data you want to add

Android runOnUiThread explanation

This should work for you

 public class MyActivity extends Activity {

    protected ProgressDialog mProgressDialog;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        populateTable();
    }

    private void populateTable() {
        mProgressDialog = ProgressDialog.show(this, "Please wait","Long operation starts...", true);
        new Thread() {
            @Override
            public void run() {

                doLongOperation();
                try {

                    // code runs in a thread
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            mProgressDialog.dismiss();
                        }
                    });
                } catch (final Exception ex) {
                    Log.i("---","Exception in thread");
                }
            }
        }.start();

    }

    /** fake operation for testing purpose */
    protected void doLongOperation() {
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
        }

    }
}

How to declare string constants in JavaScript?

Just declare variable outside of scope of any js function. Such variables will be global.

Find the day of a week

start = as.POSIXct("2017-09-01")
end = as.POSIXct("2017-09-06")

dat = data.frame(Date = seq.POSIXt(from = start,
                                   to = end,
                                   by = "DSTday"))

# see ?strptime for details of formats you can extract

# day of the week as numeric (Monday is 1)
dat$weekday1 = as.numeric(format(dat$Date, format = "%u"))

# abbreviated weekday name
dat$weekday2 = format(dat$Date, format = "%a")

# full weekday name
dat$weekday3 = format(dat$Date, format = "%A")

dat
# returns
    Date       weekday1 weekday2  weekday3
1 2017-09-01        5      Fri    Friday
2 2017-09-02        6      Sat    Saturday
3 2017-09-03        7      Sun    Sunday
4 2017-09-04        1      Mon    Monday
5 2017-09-05        2      Tue    Tuesday
6 2017-09-06        3      Wed    Wednesday

selecting unique values from a column

Use something like this in case you also want to output products details per date as JSON and the MySQL version does not support JSON functions.

SELECT `date`,
CONCAT('{',GROUP_CONCAT('{\"id\": \"',`product_id`,'\",\"name\": \"',`product_name`,'\"}'),'}') as `productsJSON`
FROM `buy` group by `date` 
order by `date` DESC

 product_id product_name     date  
|    1     |     azd    | 2011-12-12 |
|    2     |     xyz    | 2011-12-12 |
|    3     |     ase    | 2011-12-11 |
|    4     |     azwed  | 2011-12-11 |
|    5     |     wed    | 2011-12-10 |
|    6     |     cvg    | 2011-12-10 |
|    7     |     cvig   | 2011-12-09 |

RESULT
       date                                productsJSON
2011-12-12T00:00:00Z    {{"id": "1","name": "azd"},{"id": "2","name": "xyz"}}
2011-12-11T00:00:00Z    {{"id": "3","name": "ase"},{"id": "4","name": "azwed"}}
2011-12-10T00:00:00Z    {{"id": "5","name": "wed"},{"id": "6","name": "cvg"}}
2011-12-09T00:00:00Z    {{"id": "7","name": "cvig"}}

Try it out in SQL Fiddle

If you are using a MySQL version that supports JSON functions then the above query could be re-written:

SELECT `date`,JSON_OBJECTAGG(CONCAT('product-',`product_id`),JSON_OBJECT('id', `product_id`, 'name', `product_name`)) as `productsJSON`
FROM `buy` group by `date`
order by `date` DESC;

Try both in DB Fiddle

.autocomplete is not a function Error

I faced the same problem and try to solve, but unfortunately it wouldn't work anymore ! If you are facing the same problem and can't find the solution, it may help you.

If you configure jquery/jquery-ui globally in webpack, you need to import autocomplete like this

import { autocomplete } from 'webpack-jquery-ui';

And you must include jquery-ui.css in the head section of html, i don't understand why its not working without it!

<link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">

Hope your problem will be solved.

And make sure you include/install the following three

  1. jquery-ui-css
  2. jquery-ui
  3. jquery

script to map network drive

Why not map the network drive but deselect "Reconnect at logon"? The drive will only connect when you try to access it. Note that some applications will fail if they point to it, but if you're accessing files directly through Windows Explorer this works great.

how to change default python version?

Do right thing, do thing right!

--->Zero Open your terminal,

--Firstly input python -V, It likely shows:

Python 2.7.10

-Secondly input python3 -V, It likely shows:

Python 3.7.2

--Thirdly input where python or which python, It likely shows:

/usr/bin/python

---Fourthly input where python3 or which python3, It likely shows:

/usr/local/bin/python3

--Fifthly add the following line at the bottom of your PATH environment variable file in ~/.profile file or ~/.bash_profile under Bash or ~/.zshrc under zsh.

alias python='/usr/local/bin/python3'

OR

alias python=python3

-Sixthly input source ~/.bash_profile under Bash or source ~/.zshrc under zsh.

--Seventhly Quit the terminal.

---Eighthly Open your terminal, and input python -V, It likely shows:

Python 3.7.2

I had done successfully try it.

Others, the ~/.bash_profile under zsh is not that ~/.bash_profile.

The PATH environment variable under zsh instead ~/.profile (or ~/.bash_file) via ~/.zshrc.

Help you guys!

How to run .jar file by double click on Windows 7 64-bit?

I tried all above steps to resolve the problem but nothing worked. I had installed both JDK and JRE.

In my case, one jar file was being opened by double click while other was not being opened. I examined those files and the probable reason was that which was being opened, was created using JAVA SE 6 and the one not being opened was created using JAVA SE 7. Although, the problematic jar file was being run via command prompt (java -jar myfile.jar).

I tried Right Click -> Properties -> Change to javaw.exe with both in JDK\bin directory and JRE\bin directory.

I was finally able to fix the problem by changing javaw.exe path (from JDK\bin to JRE\bin) in registry editor.

Go to HKEY_CLASSES_ROOT\jarfile\shell\open\command, the value was,

"C:\Program Files\Java\jdk-11.0.1\bin\javaw.exe" -jar "%1" %*

I changed it to,

"C:\Program Files\Java\jre1.8.0_191\bin\javaw.exe" -jar "%1" %*

and it worked. Now the jar file can be opened by double click.

How to detect when a youtube video finishes playing?

What you may want to do is include a script on all pages that does the following ... 1. find the youtube-iframe : searching for it by width and height by title or by finding www.youtube.com in its source. You can do that by ... - looping through the window.frames by a for-in loop and then filter out by the properties

  1. inject jscript in the iframe of the current page adding the onYoutubePlayerReady must-include-function http://shazwazza.com/post/Injecting-JavaScript-into-other-frames.aspx

  2. Add the event listeners etc..

Hope this helps

No operator matches the given name and argument type(s). You might need to add explicit type casts. -- Netbeans, Postgresql 8.4 and Glassfish

I guess this can be due to many things. In my case it was having "WHERE id IN" condition in my query and I was setting IDs separated by dash as a string using setString method on PreparedStatement.

Not sure if there is better way to do this but I just added placeholder in my statement and replaced it by values on my own.

JQuery Bootstrap Multiselect plugin - Set a value as selected in the multiselect dropdown

work fine for me ,change ids according to you requirement.

$("#FormId select#status_id_new").val('');
 $("#FormId select#status_id_new").multiselect("refresh");

Cloning git repo causes error - Host key verification failed. fatal: The remote end hung up unexpectedly

Resolved the issue... you need to add the ssh public key to your github account.

  1. Verify that the ssh keys have been setup correctly.
    1. Run ssh-keygen
    2. Enter the password (keep the default path - ~/.ssh/id_rsa)
  2. Add the public key (~/.ssh/id_rsa.pub) to github account
  3. Try git clone. It works!


Initial status (public key not added to git hub account)

foo@bn18-251:~$ rm -rf test
foo@bn18-251:~$ ls
foo@bn18-251:~$ git clone [email protected]:devendra-d-chavan/test.git
Cloning into 'test'...
Permission denied (publickey).
fatal: The remote end hung up unexpectedly
foo@bn18-251:~$


Now, add the public key ~/.ssh/id_rsa.pub to the github account (I used cat ~/.ssh/id_rsa.pub)

foo@bn18-251:~$ ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/home/foo/.ssh/id_rsa): 
Created directory '/home/foo/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/foo/.ssh/id_rsa.
Your public key has been saved in /home/foo/.ssh/id_rsa.pub.
The key fingerprint is:
xxxxx
The key's randomart image is:
+--[ RSA 2048]----+
xxxxx
+-----------------+
foo@bn18-251:~$ cat ./.ssh/id_rsa.pub 
xxxxx
foo@bn18-251:~$ git clone [email protected]:devendra-d-chavan/test.git
Cloning into 'test'...
The authenticity of host 'github.com (207.97.227.239)' can't be established.
RSA key fingerprint is 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'github.com,207.97.227.239' (RSA) to the list of known hosts.
Enter passphrase for key '/home/foo/.ssh/id_rsa': 
warning: You appear to have cloned an empty repository.
foo@bn18-251:~$ ls
test
foo@bn18-251:~/test$ git status
# On branch master
#
# Initial commit
#
nothing to commit (create/copy files and use "git add" to track)

How do I determine the current operating system with Node.js

You are looking for the OS native module for Node.js:

v4: https://nodejs.org/dist/latest-v4.x/docs/api/os.html#os_os_platform

or v5 : https://nodejs.org/dist/latest-v5.x/docs/api/os.html#os_os_platform

os.platform()

Returns the operating system platform. Possible values are 'darwin', 'freebsd', 'linux', 'sunos' or 'win32'. Returns the value of process.platform.

Check existence of directory and create if doesn't exist

I had an issue with R 2.15.3 whereby while trying to create a tree structure recursively on a shared network drive I would get a permission error.

To get around this oddity I manually create the structure;

mkdirs <- function(fp) {
    if(!file.exists(fp)) {
        mkdirs(dirname(fp))
        dir.create(fp)
    }
} 

mkdirs("H:/foo/bar")

How do I setup the dotenv file in Node.js?

Take care that you also execute your Node script from the ROOT folder.

E.g. I was using a testing script in a subfolder called ./bin/test.js. Calling it like: node ./bin/test.js worked totally fine. Calling it from the subfolder like:

$ pwd
./bin
$ node ./test.js

causes dotenv to not find my ./.env file.

How to sort by column in descending order in Spark SQL?

You can also sort the column by importing the spark sql functions

import org.apache.spark.sql.functions._
df.orderBy(asc("col1"))

Or

import org.apache.spark.sql.functions._
df.sort(desc("col1"))

importing sqlContext.implicits._

import sqlContext.implicits._
df.orderBy($"col1".desc)

Or

import sqlContext.implicits._
df.sort($"col1".desc)

TypeError: 'int' object is not subscriptable

If you want to sum the digit of a number, one way to do it is using sum() + a generator expression:

sum(int(i) for i in str(155))

I modified a little your code using sum(), maybe you want to take a look at it:

birthday = raw_input("When is your birthday(mm/dd/yyyy)? ")
summ = sum(int(i) for i in birthday[0:2])
sumd = sum(int(i) for i in birthday[3:5])
sumy = sum(int(i) for i in birthday[6:10])
sumall = summ + sumd + sumy
print "The sum of your numbers is", sumall
sumln = sum(int(c) for c in str(sumall)))
print "Your lucky number is", sumln

JavaScript dictionary with names

You may be trying to use a JSON object:

var myMappings = { "name": "10%", "phone": "10%", "address": "50%", etc.. }

To access:

myMappings.name;
myMappings.phone;
etc..

Batch file to restart a service. Windows

net stop <your service> && net start <your service>

No net restart, unfortunately.

Multiple GitHub Accounts & SSH Config

A possibly simpler alternative to editing the ssh config file (as suggested in all other answers), is to configure an individual repository to use a different (e.g. non-default) ssh key.

Inside the repository for which you want to use a different key, run:

git config core.sshCommand 'ssh -i ~/.ssh/id_rsa_anotheraccount'

If your key is passhprase-protected and you don't want to type your password every time, you have to add it to the ssh-agent. Here's how to do it for ubuntu and here for macOS.

It should also be possible to scale this approach to multiple repositories using global git config and conditional includes (see example).

How can I create a Windows .exe (standalone executable) using Java/Eclipse?

Typical Java programs compile into .jar files, which can be executed like .exe files provided the target machine has Java installed and that Java is in its PATH. From Eclipse you use the Export menu item from the File menu.

Converting BigDecimal to Integer

Can you guarantee that the BigDecimal will never contain a value larger than Integer.MAX_VALUE?

If yes, then here's your code calling intValue:

Integer.valueOf(bdValue.intValue())

How to debug "ImagePullBackOff"?

Run docker login

Push the image to docker hub

Re-create pod

This solved the problem for me. Hope it helps.

Synchronously waiting for an async operation, and why does Wait() freeze the program here

Here is what I did

private void myEvent_Handler(object sender, SomeEvent e)
{
  // I dont know how many times this event will fire
  Task t = new Task(() =>
  {
    if (something == true) 
    {
        DoSomething(e);  
    }
  });
  t.RunSynchronously();
}

working great and not blocking UI thread

How to reload / refresh model data from the server programmatically?

Before I show you how to reload / refresh model data from the server programmatically? I have to explain for you the concept of Data Binding. This is an extremely powerful concept that will truly revolutionize the way you develop. So may be you have to read about this concept from this link or this seconde link in order to unterstand how AngularjS work.

now I'll show you a sample example that exaplain how can you update your model from server.

HTML Code:

<div ng-controller="PersonListCtrl">
    <ul>
        <li ng-repeat="person in persons">
            Name: {{person.name}}, Age {{person.age}}
        </li>
    </ul>
   <button ng-click="updateData()">Refresh Data</button>
</div>

So our controller named: PersonListCtrl and our Model named: persons. go to your Controller js in order to develop the function named: updateData() that will be invoked when we are need to update and refresh our Model persons.

Javascript Code:

app.controller('adsController', function($log,$scope,...){

.....

$scope.updateData = function(){
$http.get('/persons').success(function(data) {
       $scope.persons = data;// Update Model-- Line X
     });
}

});

Now I explain for you how it work: when user click on button Refresh Data, the server will call to function updateData() and inside this function we will invoke our web service by the function $http.get() and when we have the result from our ws we will affect it to our model (Line X).Dice that affects the results for our model, our View of this list will be changed with new Data.

How to convert string to date to string in Swift iOS?

See answer from Gary Makin. And you need change the format or data. Because the data that you have do not fit under the chosen format. For example this code works correct:

let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "MM-dd-yyyy"
let dateObj = dateFormatter.dateFromString("10 10 2001")
print("Dateobj: \(dateObj)")

convert array into DataFrame in Python

You can add parameter columns or use dict with key which is converted to column name:

np.random.seed(123)
e = np.random.normal(size=10)  
dataframe=pd.DataFrame(e, columns=['a']) 
print (dataframe)
          a
0 -1.085631
1  0.997345
2  0.282978
3 -1.506295
4 -0.578600
5  1.651437
6 -2.426679
7 -0.428913
8  1.265936
9 -0.866740

e_dataframe=pd.DataFrame({'a':e}) 
print (e_dataframe)
          a
0 -1.085631
1  0.997345
2  0.282978
3 -1.506295
4 -0.578600
5  1.651437
6 -2.426679
7 -0.428913
8  1.265936
9 -0.866740

Is an entity body allowed for an HTTP DELETE request?

It appears to me that RFC 2616 does not specify this.

From section 4.3:

The presence of a message-body in a request is signaled by the inclusion of a Content-Length or Transfer-Encoding header field in the request's message-headers. A message-body MUST NOT be included in a request if the specification of the request method (section 5.1.1) does not allow sending an entity-body in requests. A server SHOULD read and forward a message-body on any request; if the request method does not include defined semantics for an entity-body, then the message-body SHOULD be ignored when handling the request.

And section 9.7:

The DELETE method requests that the origin server delete the resource identified by the Request-URI. This method MAY be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation has been carried out, even if the status code returned from the origin server indicates that the action has been completed successfully. However, the server SHOULD NOT indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible location.

A successful response SHOULD be 200 (OK) if the response includes an entity describing the status, 202 (Accepted) if the action has not yet been enacted, or 204 (No Content) if the action has been enacted but the response does not include an entity.

If the request passes through a cache and the Request-URI identifies one or more currently cached entities, those entries SHOULD be treated as stale. Responses to this method are not cacheable.c

So it's not explicitly allowed or disallowed, and there's a chance that a proxy along the way might remove the message body (although it SHOULD read and forward it).

JavaScript: replace last occurrence of text in a string

Old fashioned and big code but efficient as possible:

function replaceLast(origin,text){
    textLenght = text.length;
    originLen = origin.length
    if(textLenght == 0)
        return origin;

    start = originLen-textLenght;
    if(start < 0){
        return origin;
    }
    if(start == 0){
        return "";
    }
    for(i = start; i >= 0; i--){
        k = 0;
        while(origin[i+k] == text[k]){
            k++
            if(k == textLenght)
                break;
        }
        if(k == textLenght)
            break;
    }
    //not founded
    if(k != textLenght)
        return origin;

    //founded and i starts on correct and i+k is the first char after
    end = origin.substring(i+k,originLen);
    if(i == 0)
        return end;
    else{
        start = origin.substring(0,i) 
        return (start + end);
    }
}

Apply function to each element of a list

Sometimes you need to apply a function to the members of a list in place. The following code worked for me:

>>> def func(a, i):
...     a[i] = a[i].lower()
>>> a = ['TEST', 'TEXT']
>>> list(map(lambda i:func(a, i), range(0, len(a))))
[None, None]
>>> print(a)
['test', 'text']

Please note, the output of map() is passed to the list constructor to ensure the list is converted in Python 3. The returned list filled with None values should be ignored, since our purpose was to convert list a in place

Display A Popup Only Once Per User

The best solution is to save a Boolean value in the database and then obtain that value and validate whether or not the modal was opened for that user, this value could be in the user table for example.

Button text toggle in jquery

If you're setting the button text by using the 'value' attribute you'll need to set

  • $(this).val()

instead of:

  • $(this).text()

Also in my situation it worked better to add the JQuery direct to the onclick event of the button:

onclick="$(this).val(function (i, text) { return text == 'PUSH ME' ? 'DON'T PUSH ME' : 'PUSH ME'; });"

What's the Use of '\r' escape sequence?

As amaud576875 said, the \r escape sequence signifies a carriage-return, similar to pressing the Enter key. However, I'm not sure how you get "o world"; you should (and I do) get "my first hello world" and then a new line. Depending on what operating system you're using (I'm using Mac) you might want to use a \n instead of a \r.

My httpd.conf is empty

It seems to me, that it is by design that this file is empty.

A similar question has been asked here: https://stackoverflow.com/questions/2567432/ubuntu-apache-httpd-conf-or-apache2-conf

So, you should have a look for /etc/apache2/apache2.conf

Search and replace a particular string in a file using Perl

Quick and dirty:

#!/usr/bin/perl -w

use strict;

open(FILE, "</tmp/yourfile.txt") || die "File not found";
my @lines = <FILE>;
close(FILE);

foreach(@lines) {
   $_ =~ s/<PREF>/ABCD/g;
}

open(FILE, ">/tmp/yourfile.txt") || die "File not found";
print FILE @lines;
close(FILE);

Perhaps it i a good idea not to write the result back to your original file; instead write it to a copy and check the result first.

How to post an array of complex objects with JSON, jQuery to ASP.NET MVC Controller?

Towards the second half of Create REST API using ASP.NET MVC that speaks both JSON and plain XML, to quote:

Now we need to accept JSON and XML payload, delivered via HTTP POST. Sometimes your client might want to upload a collection of objects in one shot for batch processing. So, they can upload objects using either JSON or XML format. There's no native support in ASP.NET MVC to automatically parse posted JSON or XML and automatically map to Action parameters. So, I wrote a filter that does it."

He then implements an action filter that maps the JSON to C# objects with code shown.

AngularJS Error: $injector:unpr Unknown Provider

@ user2310334 I just tried this, a VERY basic example:

HTML file

<!DOCTYPE html>
<html lang="en" ng-app="app">

<head>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.6/angular.min.js" type="text/javascript"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.6/angular-route.min.js" type="text/javascript"></script>
    <script src="./app.js" type="text/javascript"></script>
</head>

<body>
    <div ng-controller="MailDetailCtrl">
    </div>
</body>
</html>

The javascript file:

var myApp= angular.module('app', ['ngRoute']);

myApp.factory('mailService' , function () {
return {
    getData : function(){
      var employees = [{name: 'John Doe', id: '1'},
        {name: 'Mary Homes', id: '2'},
        {name: 'Chris Karl', id: '3'}
      ];

      return employees;
    }
  };

});


myApp.controller('MailDetailCtrl',['$scope', 'mailService', function($scope, mailService) {
  alert(mailService.getData()[0].name);
}]);

And it works. Try it.

Counting the number of elements with the values of x in a vector

This is a very fast solution for one-dimensional atomic vectors. It relies on match(), so it is compatible with NA:

x <- c("a", NA, "a", "c", "a", "b", NA, "c")

fn <- function(x) {
  u <- unique.default(x)
  out <- list(x = u, freq = .Internal(tabulate(match(x, u), length(u))))
  class(out) <- "data.frame"
  attr(out, "row.names") <- seq_along(u)
  out
}

fn(x)

#>      x freq
#> 1    a    3
#> 2 <NA>    2
#> 3    c    2
#> 4    b    1

You could also tweak the algorithm so that it doesn't run unique().

fn2 <- function(x) {
  y <- match(x, x)
  out <- list(x = x, freq = .Internal(tabulate(y, length(x)))[y])
  class(out) <- "data.frame"
  attr(out, "row.names") <- seq_along(x)
  out
}

fn2(x)

#>      x freq
#> 1    a    3
#> 2 <NA>    2
#> 3    a    3
#> 4    c    2
#> 5    a    3
#> 6    b    1
#> 7 <NA>    2
#> 8    c    2

In cases where that output is desirable, you probably don't even need it to re-return the original vector, and the second column is probably all you need. You can get that in one line with the pipe:

match(x, x) %>% `[`(tabulate(.), .)

#> [1] 3 2 3 2 3 1 2 2

How to calculate difference between two dates in oracle 11g SQL

You can use this:

SET FEEDBACK OFF;
SET SERVEROUTPUT ON;

DECLARE
  V_START_DATE  CHAR(17) := '28/03/16 17:20:00';
  V_END_DATE    CHAR(17) := '30/03/16 17:50:10';
  V_DATE_DIFF   VARCHAR2(17);

BEGIN

SELECT
  (TO_NUMBER( SUBSTR(NUMTODSINTERVAL(TO_DATE(V_END_DATE , 'DD/MM/YY HH24:MI:SS') - TO_DATE(V_START_DATE, 'DD/MM/YY HH24:MI:SS'), 'DAY'), 02, 9)) * 24) +
  (TO_NUMBER( SUBSTR(NUMTODSINTERVAL(TO_DATE(V_END_DATE , 'DD/MM/YY HH24:MI:SS') - TO_DATE(V_START_DATE, 'DD/MM/YY HH24:MI:SS'), 'DAY'), 12, 2)))  || 
              SUBSTR(NUMTODSINTERVAL(TO_DATE(V_END_DATE , 'DD/MM/YY HH24:MI:SS') - TO_DATE(V_START_DATE, 'DD/MM/YY HH24:MI:SS'), 'DAY'), 14, 6) AS "HH24:MI:SS"
  INTO V_DATE_DIFF
FROM 
  DUAL;

DBMS_OUTPUT.PUT_LINE(V_DATE_DIFF);
END;

How to find the location of the Scheduled Tasks folder

On newer versions of Windows (Windows 10 and Windows Server 2016) the tasks you create are located in C:\Windows\Tasks. They will have the extension .job

For example if you create the task "DoWork" it will create the task in

C:\Windows\Tasks\DoWork.job

How to Set/Update State of StatefulWidget from other StatefulWidget in Flutter?

I would like to extend Mohamed Elrashid answer, in case you require to pass a variable from the child widget to the parent widget

On child widget:

class ChildWidget extends StatefulWidget {
  final Function() notifyParent;
  ChildWidget({Key key, @required this.notifyParent}) : super(key: key);
}

On parent widget

void refresh(dynamic childValue) {
  setState(() {
    _parentVariable = childValue;
  });
}

On parent widget: pass the function above to the child widget

new ChildWidget( notifyParent: refresh ); 

On child widget: call the parent function with any variable from the the child widget

widget.notifyParent(childVariable);

How do I do multiple CASE WHEN conditions using SQL Server 2008?

Just use this one, You have to use more when they are classes.

SELECT   Url='',
         p.ArtNo,
         p.[Description],
         p.Specification,
         CASE 
         WHEN 1 = 1 or 1 = 1 
            THEN 1 
         WHEN 2 = 2
             THEN 2
         WHEN 3 = 3
              THEN 3
          ELSE 0 
        END as Qty,
        p.NetPrice,
        [Status] = 0
  FROM  Product p (NOLOCK)

Changing MongoDB data store directory

If installed via apt-get in Ubuntu 12.04, don't forget to chown -R mongodb:nogroup /path/to/new/directory. Also, change the configuration at /etc/mongodb.conf.

As a reminder, the mongodb-10gen package is now started via upstart, so the config script is in /etc/init/mongodb.conf

I just went through this, hope googlers find it useful :)

Is there a Social Security Number reserved for testing/examples?

There are multiple number groups and some particular numbers that will never be allocated:

Consider using one of these (the obviously invalid 000-00-0000 would be a good one IMO).

(Answer has been updated to provide source information beyond Wikipedia and remove information that is no longer accurate after the SSA made its randomization change in mid 2011.)

How does Go update third-party packages?

The above answeres have the following problems:

  1. They update everything including your app (in case you have uncommitted changes).
  2. They updated packages you may have already removed from your project but are already on your disk.

To avoid these, do the following:

  1. Delete the 3rd party folders that you want to update.
  2. go to your app folder and run go get -d

How to count how many values per level in a given factor?

Use the package plyr with lapply to get frequencies for every value (level) and every variable (factor) in your data frame.

library(plyr)
lapply(df, count)

How do I remove blank pages coming between two chapters in Appendix?

One thing I discovered is that using the \include command will often insert and extra blank page. Riffing on the previous trick with the \let command, I inserted \let\include\input near the beginning of the document, and that got rid of most of the excessive blank pages.

What is the purpose of Looper and how to use it?

A Looper has a synchronized MessageQueue that's used to process Messages placed on the queue.

It implements a Thread Specific Storage Pattern.

Only one Looper per Thread. Key methods include prepare(),loop() and quit().

prepare() initializes the current Thread as a Looper. prepare() is static method that uses the ThreadLocal class as shown below.

   public static void prepare(){
       ...
       sThreadLocal.set
       (new Looper());
   }
  1. prepare() must be called explicitly before running the event loop.
  2. loop() runs the event loop which waits for Messages to arrive on a specific Thread's messagequeue. Once the next Message is received,the loop() method dispatches the Message to its target handler
  3. quit() shuts down the event loop. It doesn't terminate the loop,but instead it enqueues a special message

Looper can be programmed in a Thread via several steps

  1. Extend Thread

  2. Call Looper.prepare() to initialize Thread as a Looper

  3. Create one or more Handler(s) to process the incoming messages

  4. Call Looper.loop() to process messages until the loop is told to quit().

Delete column from pandas DataFrame

The actual question posed, missed by most answers here is:

Why can't I use del df.column_name?

At first we need to understand the problem, which requires us to dive into python magic methods.

As Wes points out in his answer del df['column'] maps to the python magic method df.__delitem__('column') which is implemented in pandas to drop the column

However, as pointed out in the link above about python magic methods:

In fact, __del__ should almost never be used because of the precarious circumstances under which it is called; use it with caution!

You could argue that del df['column_name'] should not be used or encouraged, and thereby del df.column_name should not even be considered.

However, in theory, del df.column_name could be implemeted to work in pandas using the magic method __delattr__. This does however introduce certain problems, problems which the del df['column_name'] implementation already has, but in lesser degree.

Example Problem

What if I define a column in a dataframe called "dtypes" or "columns".

Then assume I want to delete these columns.

del df.dtypes would make the __delattr__ method confused as if it should delete the "dtypes" attribute or the "dtypes" column.

Architectural questions behind this problem

  1. Is a dataframe a collection of columns?
  2. Is a dataframe a collection of rows?
  3. Is a column an attribute of a dataframe?

Pandas answers:

  1. Yes, in all ways
  2. No, but if you want it to be, you can use the .ix, .loc or .iloc methods.
  3. Maybe, do you want to read data? Then yes, unless the name of the attribute is already taken by another attribute belonging to the dataframe. Do you want to modify data? Then no.

TLDR;

You cannot do del df.column_name because pandas has a quite wildly grown architecture that needs to be reconsidered in order for this kind of cognitive dissonance not to occur to its users.

Protip:

Don't use df.column_name, It may be pretty, but it causes cognitive dissonance

Zen of Python quotes that fits in here:

There are multiple ways of deleting a column.

There should be one-- and preferably only one --obvious way to do it.

Columns are sometimes attributes but sometimes not.

Special cases aren't special enough to break the rules.

Does del df.dtypes delete the dtypes attribute or the dtypes column?

In the face of ambiguity, refuse the temptation to guess.

Replace words in a string - Ruby

If you're dealing with natural language text and need to replace a word, not just part of a string, you have to add a pinch of regular expressions to your gsub as a plain text substitution can lead to disastrous results:

'mislocated cat, vindicating'.gsub('cat', 'dog')
=> "mislodoged dog, vindidoging"

Regular expressions have word boundaries, such as \b which matches start or end of a word. Thus,

'mislocated cat, vindicating'.gsub(/\bcat\b/, 'dog')
=> "mislocated dog, vindicating"

In Ruby, unlike some other languages like Javascript, word boundaries are UTF-8-compatible, so you can use it for languages with non-Latin or extended Latin alphabets:

'???? ? ??????, ??? ??????'.gsub(/\b????\b/, '?????')
=> "????? ? ??????, ??? ??????"

Format a JavaScript string using placeholders and an object of substitutions?

This allows you to do exactly that

NPM: https://www.npmjs.com/package/stringinject

GitHub: https://github.com/tjcafferkey/stringinject

By doing the following:

var str = stringInject("My username is {username} on {platform}", { username: "tjcafferkey", platform: "GitHub" });

// My username is tjcafferkey on Git

The static keyword and its various uses in C++

In order to clarify the question, I would rather categorize the usage of 'static' keyword in three different forms:

(A). variables

(B). functions

(C). member variables/functions of classes

the explanation follows below for each of the sub headings:

(A) 'static' keyword for variables

This one can be little tricky however if explained and understood properly, it's pretty straightforward.

To explain this, first it is really useful to know about the scope, duration and linkage of variables, without which things are always difficult to see through the murky concept of staic keyword

1. Scope : Determines where in the file, the variable is accessible. It can be of two types: (i) Local or Block Scope. (ii) Global Scope

2. Duration : Determines when a variable is created and destroyed. Again it's of two types: (i) Automatic Storage Duration (for variables having Local or Block scope). (ii) Static Storage Duration (for variables having Global Scope or local variables (in a function or a in a code block) with static specifier).

3. Linkage: Determines whether a variable can be accessed (or linked ) in another file. Again ( and luckily) it is of two types: (i) Internal Linkage (for variables having Block Scope and Global Scope/File Scope/Global Namespace scope) (ii) External Linkage (for variables having only for Global Scope/File Scope/Global Namespace Scope)

Let's refer an example below for better understanding of plain global and local variables (no local variables with static storage duration) :

//main file
#include <iostream>

int global_var1; //has global scope
const global_var2(1.618); //has global scope

int main()
{
//these variables are local to the block main.
//they have automatic duration, i.e, they are created when the main() is 
//  executed and destroyed, when main goes out of scope
 int local_var1(23);
 const double local_var2(3.14);

 {
/* this is yet another block, all variables declared within this block are 
 have local scope limited within this block. */
// all variables declared within this block too have automatic duration, i.e, 
/*they are created at the point of definition within this block,
 and destroyed as soon as this block ends */
   char block_char1;
   int local_var1(32) //NOTE: this has been re-declared within the block, 
//it shadows the local_var1 declared outside

 std::cout << local_var1 <<"\n"; //prints 32

  }//end of block
  //local_var1 declared inside goes out of scope

 std::cout << local_var1 << "\n"; //prints 23

 global_var1 = 29; //global_var1 has been declared outside main (global scope)
 std::cout << global_var1 << "\n"; //prints 29
 std::cout << global_var2 << "\n"; //prints 1.618

 return 0;
}  //local_var1, local_var2 go out of scope as main ends
//global_var1, global_var2 go out of scope as the program terminates 
//(in this case program ends with end of main, so both local and global
//variable go out of scope together

Now comes the concept of Linkage. When a global variable defined in one file is intended to be used in another file, the linkage of the variable plays an important role.

The Linkage of global variables is specified by the keywords: (i) static , and, (ii) extern

( Now you get the explanation )

static keyword can be applied to variables with local and global scope, and in both the cases, they mean different things. I will first explain the usage of 'static' keyword in variables with global scope ( where I also clarify the usage of keyword 'extern') and later the for those with local scope.

1. Static Keyword for variables with global scope

Global variables have static duration, meaning they don't go out of scope when a particular block of code (for e.g main() ) in which it is used ends . Depending upon the linkage, they can be either accessed only within the same file where they are declared (for static global variable), or outside the file even outside the file in which they are declared (extern type global variables)

In the case of a global variable having extern specifier, and if this variable is being accessed outside the file in which it has been initialized, it has to be forward declared in the file where it's being used, just like a function has to be forward declared if it's definition is in a file different from where it's being used.

In contrast, if the global variable has static keyword, it cannot be used in a file outside of which it has been declared.

(see example below for clarification)

eg:

//main2.cpp
 static int global_var3 = 23;  /*static global variable, cannot be                            
                                accessed in anyother file */
 extern double global_var4 = 71; /*can be accessed outside this file                  linked to main2.cpp */
 int main() { return 0; }

main3.cpp

//main3.cpp
#include <iostream>

int main()
{
   extern int gloabl_var4; /*this variable refers to the gloabal_var4
                            defined in the main2.cpp file */
  std::cout << global_var4 << "\n"; //prints 71;

  return 0;
}

now any variable in c++ can be either a const or a non-const and for each 'const-ness' we get two case of default c++ linkage, in case none is specified:

(i) If a global variable is non-const, its linkage is extern by default, i.e, the non-const global variable can be accessed in another .cpp file by forward declaration using the extern keyword (in other words, non const global variables have external linkage ( with static duration of course)). Also usage of extern keyword in the original file where it has been defined is redundant. In this case to make a non-const global variable inaccessible to external file, use the specifier 'static' before the type of the variable.

(ii) If a global variable is const, its linkage is static by default, i.e a const global variable cannot be accessed in a file other than where it is defined, (in other words, const global variables have internal linkage (with static duration of course)). Also usage of static keyword to prevent a const global variable from being accessed in another file is redundant. Here, to make a const global variable have an external linkage, use the specifier 'extern' before the type of the variable

Here's a summary for global scope variables with various linkages

//globalVariables1.cpp 

// defining uninitialized vairbles
int globalVar1; //  uninitialized global variable with external linkage 
static int globalVar2; // uninitialized global variable with internal linkage
const int globalVar3; // error, since const variables must be initialized upon declaration
const int globalVar4 = 23; //correct, but with static linkage (cannot be accessed outside the file where it has been declared*/
extern const double globalVar5 = 1.57; //this const variable ca be accessed outside the file where it has been declared

Next we investigate how the above global variables behave when accessed in a different file.

//using_globalVariables1.cpp (eg for the usage of global variables above)

// Forward declaration via extern keyword:
 extern int globalVar1; // correct since globalVar1 is not a const or static
 extern int globalVar2; //incorrect since globalVar2 has internal linkage
 extern const int globalVar4; /* incorrect since globalVar4 has no extern 
                         specifier, limited to internal linkage by
                         default (static specifier for const variables) */
 extern const double globalVar5; /*correct since in the previous file, it 
                           has extern specifier, no need to initialize the
                       const variable here, since it has already been
                       legitimately defined perviously */

2. Static Keyword for variables with Local Scope

Updates (August 2019) on static keyword for variables in local scope

This further can be subdivided in two categories :

(i) static keyword for variables within a function block, and (ii) static keyword for variables within a unnamed local block.

(i) static keyword for variables within a function block.

Earlier, I mentioned that variables with local scope have automatic duration, i.e they come to exist when the block is entered ( be it a normal block, be it a function block) and cease to exist when the block ends, long story short, variables with local scope have automatic duration and automatic duration variables (and objects) have no linkage meaning they are not visible outside the code block.

If static specifier is applied to a local variable within a function block, it changes the duration of the variable from automatic to static and its life time is the entire duration of the program which means it has a fixed memory location and its value is initialized only once prior to program start up as mentioned in cpp reference(initialization should not be confused with assignment)

lets take a look at an example.

//localVarDemo1.cpp    
 int localNextID()
{
  int tempID = 1;  //tempID created here
  return tempID++; //copy of tempID returned and tempID incremented to 2
} //tempID destroyed here, hence value of tempID lost

int newNextID()
{
  static int newID = 0;//newID has static duration, with internal linkage
  return newID++; //copy of newID returned and newID incremented by 1
}  //newID doesn't get destroyed here :-)


int main()
{
  int employeeID1 = localNextID();  //employeeID1 = 1
  int employeeID2 = localNextID();  // employeeID2 = 1 again (not desired)
  int employeeID3 = newNextID(); //employeeID3 = 0;
  int employeeID4 = newNextID(); //employeeID4 = 1;
  int employeeID5 = newNextID(); //employeeID5 = 2;
  return 0;
}

Looking at the above criterion for static local variables and static global variables, one might be tempted to ask, what the difference between them could be. While global variables are accessible at any point in within the code (in same as well as different translation unit depending upon the const-ness and extern-ness), a static variable defined within a function block is not directly accessible. The variable has to be returned by the function value or reference. Lets demonstrate this by an example:

//localVarDemo2.cpp 

//static storage duration with global scope 
//note this variable can be accessed from outside the file
//in a different compilation unit by using `extern` specifier
//which might not be desirable for certain use case.
static int globalId = 0;

int newNextID()
{
  static int newID = 0;//newID has static duration, with internal linkage
  return newID++; //copy of newID returned and newID incremented by 1
}  //newID doesn't get destroyed here


int main()
{
    //since globalId is accessible we use it directly
  const int globalEmployee1Id = globalId++; //globalEmployeeId1 = 0;
  const int globalEmployee2Id = globalId++; //globalEmployeeId1 = 1;

  //const int employeeID1 = newID++; //this will lead to compilation error since newID++ is not accessible direcly. 
  int employeeID2 = newNextID(); //employeeID3 = 0;
  int employeeID2 = newNextID(); //employeeID3 = 1;

  return 0;
}

More explaination about choice of static global and static local variable could be found on this stackoverflow thread

(ii) static keyword for variables within a unnamed local block.

static variables within a local block (not a function block) cannot be accessed outside the block once the local block goes out of scope. No caveats to this rule.

    //localVarDemo3.cpp 
    int main()
    {

      {
          const static int static_local_scoped_variable {99};
      }//static_local_scoped_variable goes out of scope

      //the line below causes compilation error
      //do_something is an arbitrary function
      do_something(static_local_scoped_variable);
      return 0;
    }

C++11 introduced the keyword constexpr which guarantees the evaluation of an expression at compile time and allows compiler to optimize the code. Now if the value of a static const variable within a scope is known at compile time, the code is optimized in a manner similar to the one with constexpr. Here's a small example

I recommend readers also to look up the difference between constexprand static const for variables in this stackoverflow thread. this concludes my explanation for the static keyword applied to variables.

B. 'static' keyword used for functions

in terms of functions, the static keyword has a straightforward meaning. Here, it refers to linkage of the function Normally all functions declared within a cpp file have external linkage by default, i.e a function defined in one file can be used in another cpp file by forward declaration.

using a static keyword before the function declaration limits its linkage to internal , i.e a static function cannot be used within a file outside of its definition.

C. Staitc Keyword used for member variables and functions of classes

1. 'static' keyword for member variables of classes

I start directly with an example here

#include <iostream>

class DesignNumber
{
  private:

      static int m_designNum;  //design number
      int m_iteration;     // number of iterations performed for the design

  public:
    DesignNumber() {     }  //default constructor

   int  getItrNum() //get the iteration number of design
   {
      m_iteration = m_designNum++;
      return m_iteration;
   }
     static int m_anyNumber;  //public static variable
};
int DesignNumber::m_designNum = 0; // starting with design id = 0
                     // note : no need of static keyword here
                     //causes compiler error if static keyword used
int DesignNumber::m_anyNumber = 99; /* initialization of inclass public 
                                    static member  */
enter code here

int main()
{
   DesignNumber firstDesign, secondDesign, thirdDesign;
   std::cout << firstDesign.getItrNum() << "\n";  //prints 0
   std::cout << secondDesign.getItrNum() << "\n"; //prints 1
   std::cout << thirdDesign.getItrNum() << "\n";  //prints 2

   std::cout << DesignNumber::m_anyNumber++ << "\n";  /* no object
                                        associated with m_anyNumber */
   std::cout << DesignNumber::m_anyNumber++ << "\n"; //prints 100
   std::cout << DesignNumber::m_anyNumber++ << "\n"; //prints 101

   return 0;
}

In this example, the static variable m_designNum retains its value and this single private member variable (because it's static) is shared b/w all the variables of the object type DesignNumber

Also like other member variables, static member variables of a class are not associated with any class object, which is demonstrated by the printing of anyNumber in the main function

const vs non-const static member variables in class

(i) non-const class static member variables In the previous example the static members (both public and private) were non constants. ISO standard forbids non-const static members to be initialized in the class. Hence as in previous example, they must be initalized after the class definition, with the caveat that the static keyword needs to be omitted

(ii) const-static member variables of class this is straightforward and goes with the convention of other const member variable initialization, i.e the const static member variables of a class can be initialized at the point of declaration and they can be initialized at the end of the class declaration with one caveat that the keyword const needs to be added to the static member when being initialized after the class definition.

I would however, recommend to initialize the const static member variables at the point of declaration. This goes with the standard C++ convention and makes the code look cleaner

for more examples on static member variables in a class look up the following link from learncpp.com http://www.learncpp.com/cpp-tutorial/811-static-member-variables/

2. 'static' keyword for member function of classes

Just like member variables of classes can ,be static, so can member functions of classes. Normal member functions of classes are always associated with a object of the class type. In contrast, static member functions of a class are not associated with any object of the class, i.e they have no *this pointer.

Secondly since the static member functions of the class have no *this pointer, they can be called using the class name and scope resolution operator in the main function (ClassName::functionName(); )

Thirdly static member functions of a class can only access static member variables of a class, since non-static member variables of a class must belong to a class object.

for more examples on static member functions in a class look up the following link from learncpp.com

http://www.learncpp.com/cpp-tutorial/812-static-member-functions/

PHP Multidimensional Array Searching (Find key by specific value)

Try this

function recursive_array_search($needle,$haystack) {
        foreach($haystack as $key=>$value) {
            $current_key=$key;
            if($needle==$value['uid'] OR (is_array($value) && recursive_array_search($needle,$value) !== false)) {
                return $current_key;
            }
        }
        return false;
    }

How to disable logging on the standard error stream in Python?

You could also:

handlers = app.logger.handlers
# detach console handler
app.logger.handlers = []
# attach
app.logger.handlers = handlers

Right query to get the current number of connections in a PostgreSQL DB

They definitely may give different results. The better one is

select count(*) from pg_stat_activity;

It's because it includes connections to WAL sender processes which are treated as regular connections and count towards max_connections.

See max_wal_senders

How to read integer values from text file

I would use nearly the same way but with list as buffer for read integers:

static Object[] readFile(String fileName) {
    Scanner scanner = new Scanner(new File(fileName));
    List<Integer> tall = new ArrayList<Integer>();
    while (scanner.hasNextInt()) {
        tall.add(scanner.nextInt());
    }

    return tall.toArray();
}

Segmentation Fault - C

Catastrophically bad:

int main(void){
      char *s;
      int ln;
      puts("Enter String");
      // scanf("%s", s);
      gets(s);
      ln = strlen(s); // remove this line to end seg fault
      char *dyn_s = (char*) malloc (strlen(s)+1); //strlen(s) is used here as well but doesn't change outcome
      dyn_s = s;
      dyn_s[strlen(s)] = '\0';
      puts(dyn_s);
      return 0;
    }

Better:

#include <stdio.h>
#define BUF_SIZE 80

int 
main(int argc, char *argv[])
{
      char s[BUF_SIZE];
      int ln;
      puts("Enter String");
      // scanf("%s", s);
      gets(s);
      ln = strlen(s); // remove this line to end seg fault
      char *dyn_s = (char*) malloc (strlen(s)+1); //strlen(s) is used here as well but doesn't change outcome
      dyn_s = s;
      dyn_s[strlen(s)] = '\0';
      puts(dyn_s);
      return 0;
    }

Best:

#include <stdio.h>
#define BUF_SIZE 80

int 
main(int argc, char *argv[])
{
      char s[BUF_SIZE];
      int ln;
      puts("Enter String");
      fgets(s, BUF_SIZE, stdin); // Use fgets (our "cin"): NEVER "gets()"

      int ln = strlen(s); 
      char *dyn_s = (char*) malloc (ln+1);
      strcpy (dyn_s, s);
      puts(dyn_s);
      return 0;
    }

Replacing all non-alphanumeric characters with empty strings

Java's regular expressions don't require you to put a forward-slash (/) or any other delimiter around the regex, as opposed to other languages like Perl, for example.

Array or List in Java. Which is faster?

Array is faster - all memory is pre-allocated in advance.

How do I pass a URL with multiple parameters into a URL?

I see you're having issues with the social share links. I had a similar issue at some point and found this question, but I don't see a complete answer for it. I hope my javascript resolution from below will help:

I had default sharing links that needed to be modified so that the URL that's being shared will have additional UTM parameters concatenated.

My example will be for the Facebook social share link, but it works for all the possible social sharing network links:

The URL that needed to be shared was:

https://mywebsitesite.com/blog/post-name

The default sharing link looked like:

$facebook_default = "https://www.facebook.com/sharer.php?u=https%3A%2F%2mywebsitesite.com%2Fblog%2Fpost-name%2F&t=hello"

I first DECODED it:

console.log( decodeURIComponent($facebook_default) );
=>
https://www.facebook.com/sharer.php?u=https://mywebsitesite.com/blog/post-name/&t=hello

Then I replaced the URL with the encoded new URL (with the UTM parameters concatenated):

console.log( decodeURIComponent($facebook_default).replace( window.location.href, encodeURIComponent(window.location.href+'?utm_medium=social&utm_source=facebook')) );

=>

https://www.facebook.com/sharer.php?u=https%3A%2F%mywebsitesite.com%2Fblog%2Fpost-name%2F%3Futm_medium%3Dsocial%26utm_source%3Dfacebook&t=2018

That's it!

Complete solution:

$facebook_default = $('a.facebook_default_link').attr('href');

$('a.facebook_default_link').attr( 'href', decodeURIComponent($facebook_default).replace( window.location.href, encodeURIComponent(window.location.href+'?utm_medium=social&utm_source=facebook')) );

What are the differences and similarities between ffmpeg, libav, and avconv?

Confusing messages

These messages are rather misleading and understandably a source of confusion. Older Ubuntu versions used Libav which is a fork of the FFmpeg project. FFmpeg returned in Ubuntu 15.04 "Vivid Vervet".

The fork was basically a non-amicable result of conflicting personalities and development styles within the FFmpeg community. It is worth noting that the maintainer for Debian/Ubuntu switched from FFmpeg to Libav on his own accord due to being involved with the Libav fork.

The real ffmpeg vs the fake one

For a while both Libav and FFmpeg separately developed their own version of ffmpeg.

Libav then renamed their bizarro ffmpeg to avconv to distance themselves from the FFmpeg project. During the transition period the "not developed anymore" message was displayed to tell users to start using avconv instead of their counterfeit version of ffmpeg. This confused users into thinking that FFmpeg (the project) is dead, which is not true. A bad choice of words, but I can't imagine Libav not expecting such a response by general users.

This message was removed upstream when the fake "ffmpeg" was finally removed from the Libav source, but, depending on your version, it can still show up in Ubuntu because the Libav source Ubuntu uses is from the ffmpeg-to-avconv transition period.

In June 2012, the message was re-worded for the package libav - 4:0.8.3-0ubuntu0.12.04.1. Unfortunately the new "deprecated" message has caused additional user confusion.

Starting with Ubuntu 15.04 "Vivid Vervet", FFmpeg's ffmpeg is back in the repositories again.

libav vs Libav

To further complicate matters, Libav chose a name that was historically used by FFmpeg to refer to its libraries (libavcodec, libavformat, etc). For example the libav-user mailing list, for questions and discussions about using the FFmpeg libraries, is unrelated to the Libav project.

How to tell the difference

If you are using avconv then you are using Libav. If you are using ffmpeg you could be using FFmpeg or Libav. Refer to the first line in the console output to tell the difference: the copyright notice will either mention FFmpeg or Libav.

Secondly, the version numbering schemes differ. Each of the FFmpeg or Libav libraries contains a version.h header which shows a version number. FFmpeg will end in three digits, such as 57.67.100, and Libav will end in one digit such as 57.67.0. You can also view the library version numbers by running ffmpeg or avconv and viewing the console output.

If you want to use the real ffmpeg

Ubuntu 15.04 "Vivid Vervet" or newer

The real ffmpeg is in the repository, so you can install it with:

apt-get install ffmpeg

For older Ubuntu versions

Your options are:

These methods are non-intrusive, reversible, and will not interfere with the system or any repository packages.

Another possible option is to upgrade to Ubuntu 15.04 "Vivid Vervet" or newer and just use ffmpeg from the repository.

Also see

For an interesting blog article on the situation, as well as a discussion about the main technical differences between the projects, see The FFmpeg/Libav situation.

JPA COUNT with composite primary key query not working

Use count(d.ertek) or count(d.id) instead of count(d). This can be happen when you have composite primary key at your entity.

Error 1022 - Can't write; duplicate key in table

From the two linksResolved Successfully and Naming Convention, I easily solved this same problem which I faced. i.e., for the foreign key name, give as fk_colName_TableName. This naming convention is non-ambiguous and also makes every ForeignKey in your DB Model unique and you will never get this error.

Error 1022: Can't write; duplicate key in table

PHP 7 simpleXML

For Alpine (in docker), you can use apk add php7-simplexml.

If that doesn't work for you, you can run apk add --no-cache php7-simplexml. This is in case you aren't updating the package index first.

Stripping everything but alphanumeric chars from a string in Python

How about:

def ExtractAlphanumeric(InputString):
    from string import ascii_letters, digits
    return "".join([ch for ch in InputString if ch in (ascii_letters + digits)])

This works by using list comprehension to produce a list of the characters in InputString if they are present in the combined ascii_letters and digits strings. It then joins the list together into a string.

INSTALL_FAILED_NO_MATCHING_ABIS when install apk

Just in case, this might help someone like me. I had this same issue in Unity 3D. I was attempting to use the emulators from Android Studio. So I enabled Target Architecture->x86 Architecture(although deprecated) in Player Settings and it worked!

DateTimePicker time picker in 24 hour but displaying in 12hr?

'DD/MM/YYYY hh:mm A' => 12 hours 'DD/MM/YYYY HH:mm A' => 24 hours

MySQL: Selecting multiple fields into multiple variables in a stored procedure

Alternatively to Martin's answer, you could also add the INTO part at the end of the query to make the query more readable:

SELECT Id, dateCreated FROM products INTO iId, dCreate

Finding index of character in Swift String

extension String {

    // MARK: - sub String
    func substringToIndex(index:Int) -> String {
        return self.substringToIndex(advance(self.startIndex, index))
    }
    func substringFromIndex(index:Int) -> String {
        return self.substringFromIndex(advance(self.startIndex, index))
    }
    func substringWithRange(range:Range<Int>) -> String {
        let start = advance(self.startIndex, range.startIndex)
        let end = advance(self.startIndex, range.endIndex)
        return self.substringWithRange(start..<end)
    }

    subscript(index:Int) -> Character{
        return self[advance(self.startIndex, index)]
    }
    subscript(range:Range<Int>) -> String {
        let start = advance(self.startIndex, range.startIndex)
            let end = advance(self.startIndex, range.endIndex)
            return self[start..<end]
    }


    // MARK: - replace
    func replaceCharactersInRange(range:Range<Int>, withString: String!) -> String {
        var result:NSMutableString = NSMutableString(string: self)
        result.replaceCharactersInRange(NSRange(range), withString: withString)
        return result
    }
}

Hide Command Window of .BAT file that Executes Another .EXE File

I used this to start a cmd file from C#:

Process proc = new Process();
proc.StartInfo.WorkingDirectory = "myWorkingDirectory";
proc.StartInfo.FileName = "myFileName.cmd";
proc.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
proc.Start();
proc.WaitForExit();

annotation to make a private method public only for test classes

As much as I know there is no annotation like this. The best way is to use reflection as some of the others suggested. Look at this post:
How do I test a class that has private methods, fields or inner classes?

You should only watch out on testing the exception outcome of the method. For example: if u expect an IllegalArgumentException, but instead you'll get "null" (Class:java.lang.reflect.InvocationTargetException).
A colegue of mine proposed using the powermock framework for these situations, but I haven't tested it yet, so no idea what exactly it can do. Although I have used the Mockito framework that it is based upon and thats a good framework too (but I think doesn't solve the private method exception issue).

It's a great idea though having the @PublicForTests annotation.

Cheers!

How to sum the values of a JavaScript object?

It can be as simple as that:

const sumValues = obj => Object.values(obj).reduce((a, b) => a + b);

Quoting MDN:

The Object.values() method returns an array of a given object's own enumerable property values, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).

from Object.values() on MDN

The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

from Array.prototype.reduce() on MDN

You can use this function like that:

sumValues({a: 4, b: 6, c: -5, d: 0}); // gives 5

Note that this code uses some ECMAScript features which are not supported by some older browsers (like IE). You might need to use Babel to compile your code.

Module is not available, misspelled or forgot to load (but I didn't)

I found this question when I got the same error for a different reason.

My issue was that my Gulp hadn't picked up on the fact that I had declared a new module and I needed to manually re-run Gulp.

Which icon sizes should my Windows application's icon include?

TL;DR. In Visual Studio 2019, when you add an Icon resource to a Win32 (desktop) application you get an auto-generated icon file that has the formats below. I assume that the #1 developer tool for Windows does this right. Thus, a Windows compatible should have the following formats:

| Resolution | Color depth | Format |
|:-----------|------------:|:------:|
| 256x256    |      32-bit |  PNG   |
| 64x64      |      32-bit |  BMP   |
| 48x48      |      32-bit |  BMP   |
| 32x32      |      32-bit |  BMP   |
| 16x16      |      32-bit |  BMP   |
| 48x48      |       8-bit |  BMP   |
| 32x32      |       8-bit |  BMP   |
| 16x16      |       8-bit |  BMP   |

What is the difference between print and puts?

The API docs give some good hints:

print() ? nil

print(obj, ...) ? nil

Writes the given object(s) to ios. Returns nil.

The stream must be opened for writing. Each given object that isn't a string will be converted by calling its to_s method. When called without arguments, prints the contents of $_.

If the output field separator ($,) is not nil, it is inserted between objects. If the output record separator ($\) is not nil, it is appended to the output.

...

puts(obj, ...) ? nil

Writes the given object(s) to ios. Writes a newline after any that do not already end with a newline sequence. Returns nil.

The stream must be opened for writing. If called with an array argument, writes each element on a new line. Each given object that isn't a string or array will be converted by calling its to_s method. If called without arguments, outputs a single newline.

Experimenting a little with the points given above, the differences seem to be:

  • Called with multiple arguments, print separates them by the 'output field separator' $, (which defaults to nothing) while puts separates them by newlines. puts also puts a newline after the final argument, while print does not.

    2.1.3 :001 > print 'hello', 'world'
    helloworld => nil 
    2.1.3 :002 > puts 'hello', 'world'
    hello
    world
     => nil
    2.1.3 :003 > $, = 'fanodd'
     => "fanodd" 
    2.1.3 :004 > print 'hello', 'world'
    hellofanoddworld => nil 
    2.1.3 :005 > puts 'hello', 'world'
    hello
    world
     => nil
  • puts automatically unpacks arrays, while print does not:

    2.1.3 :001 > print [1, [2, 3]], [4]
    [1, [2, 3]][4] => nil 
    2.1.3 :002 > puts [1, [2, 3]], [4]
    1
    2
    3
    4
     => nil
  • print with no arguments prints $_ (the last thing read by gets), while puts prints a newline:

    2.1.3 :001 > gets
    hello world
     => "hello world\n" 
    2.1.3 :002 > puts
    
     => nil 
    2.1.3 :003 > print
    hello world
     => nil
  • print writes the output record separator $\ after whatever it prints, while puts ignores this variable:

    mark@lunchbox:~$ irb
    2.1.3 :001 > $\ = 'MOOOOOOO!'
     => "MOOOOOOO!" 
    2.1.3 :002 > puts "Oink! Baa! Cluck! "
    Oink! Baa! Cluck! 
     => nil 
    2.1.3 :003 > print "Oink! Baa! Cluck! "
    Oink! Baa! Cluck! MOOOOOOO! => nil

Difference between sh and bash

/bin/sh may or may not invoke the same program as /bin/bash.

sh supports at least the features required by POSIX (assuming a correct implementation). It may support extensions as well.

bash, the "Bourne Again Shell", implements the features required for sh plus bash-specific extensions. The full set of extensions is too long to describe here, and it varies with new releases. The differences are documented in the bash manual. Type info bash and read the "Bash Features" section (section 6 in the current version), or read the current documentation online.

java howto ArrayList push, pop, shift, and unshift

maybe you want to take a look java.util.Stack class. it has push, pop methods. and implemented List interface.

for shift/unshift, you can reference @Jon's answer.

however, something of ArrayList you may want to care about , arrayList is not synchronized. but Stack is. (sub-class of Vector). If you have thread-safe requirement, Stack may be better than ArrayList.

PHP error: "The zip extension and unzip command are both missing, skipping."

I had PHP7.2 on a Ubuntu 16.04 server and it solved my problem:

sudo apt-get install zip unzip php-zip

Update

Tried this for Ubuntu 18.04 and worked as well.

How to Create an excel dropdown list that displays text with a numeric hidden value

There are two types of drop down lists available (I am not sure since which version).

ActiveX Drop Down
You can set the column widths, so your hidden column can be set to 0.

Form Drop Down
You could set the drop down range to a hidden sheet and reference the cell adjacent to the selected item. This would also work with the ActiveX type control.

How to use a RELATIVE path with AuthUserFile in htaccess?

or if you develop on localhost (only for apache 2.4+):

<If "%{REMOTE_ADDR} != '127.0.0.1'">
</If>

Equation for testing if a point is inside a circle

Here is the simple java code for solving this problem:

and the math behind it : https://math.stackexchange.com/questions/198764/how-to-know-if-a-point-is-inside-a-circle

boolean insideCircle(int[] point, int[] center, int radius) {
    return (float)Math.sqrt((int)Math.pow(point[0]-center[0],2)+(int)Math.pow(point[1]-center[1],2)) <= radius;
}

How to convert a string to character array in c (or) how to extract a single char form string?

In C, there's no (real, distinct type of) strings. Every C "string" is an array of chars, zero terminated.

Therefore, to extract a character c at index i from string your_string, just use

char c = your_string[i];

Index is base 0 (first character is your_string[0], second is your_string[1]...).

How can I remove "\r\n" from a string in C#? Can I use a regular expression?

Here is the perfect method:

Please note that Environment.NewLine works on on Microsoft platforms.

In addition to the above, you need to add \r and \n in a separate function!

Here is the code which will support whether you type on Linux, Windows, or Mac:

var stringTest = "\r Test\nThe Quick\r\n brown fox";

Console.WriteLine("Original is:");
Console.WriteLine(stringTest);
Console.WriteLine("-------------");

stringTest = stringTest.Trim().Replace("\r", string.Empty);
stringTest = stringTest.Trim().Replace("\n", string.Empty);
stringTest = stringTest.Replace(Environment.NewLine, string.Empty);

Console.WriteLine("Output is : ");
Console.WriteLine(stringTest);
Console.ReadLine();

100% width background image with an 'auto' height

Tim S. was much closer to a "correct" answer then the currently accepted one. If you want to have a 100% width, variable height background image done with CSS, instead of using cover (which will allow the image to extend out from the sides) or contain (which does not allow the image to extend out at all), just set the CSS like so:

body {
    background-image: url(img.jpg);
    background-position: center top;
    background-size: 100% auto;
}

This will set your background image to 100% width and allow the height to overflow. Now you can use media queries to swap out that image instead of relying on JavaScript.

EDIT: I just realized (3 months later) that you probably don't want the image to overflow; you seem to want the container element to resize based on it's background-image (to preserve it's aspect ratio), which is not possible with CSS as far as I know.

Hopefully soon you'll be able to use the new srcset attribute on the img element. If you want to use img elements now, the currently accepted answer is probably best.

However, you can create a responsive background-image element with a constant aspect ratio using purely CSS. To do this, you set the height to 0 and set the padding-bottom to a percentage of the element's own width, like so:

.foo {
    height: 0;
    padding: 0; /* remove any pre-existing padding, just in case */
    padding-bottom: 75%; /* for a 4:3 aspect ratio */
    background-image: url(foo.png);
    background-position: center center;
    background-size: 100%;
    background-repeat: no-repeat;
}

In order to use different aspect ratios, divide the height of the original image by it's own width, and multiply by 100 to get the percentage value. This works because padding percentage is always calculated based on width, even if it's vertical padding.

Hide scroll bar, but while still being able to scroll

The following SASS styling should make your scrollbar transparent on most browsers (Firefox is not supported):

.hide-scrollbar {
  scrollbar-width: thin;
  scrollbar-color: transparent transparent;

  &::-webkit-scrollbar {
    width: 1px;
  }

  &::-webkit-scrollbar-track {
    background: transparent;
  }

  &::-webkit-scrollbar-thumb {
    background-color: transparent;
  }
}

Jquery mouseenter() vs mouseover()

This example demonstrates the difference between the mousemove, mouseenter and mouseover events:

https://jsfiddle.net/z8g613yd/

HTML:

<div onmousemove="myMoveFunction()">
    <p>onmousemove: <br> <span id="demo">Mouse over me!</span></p>
</div>

<div onmouseenter="myEnterFunction()">
    <p>onmouseenter: <br> <span id="demo2">Mouse over me!</span></p>
</div>

<div onmouseover="myOverFunction()">
    <p>onmouseover: <br> <span id="demo3">Mouse over me!</span></p>
</div>

CSS:

div {
    width: 200px;
    height: 100px;
    border: 1px solid black;
    margin: 10px;
    float: left;
    padding: 30px;
    text-align: center;
    background-color: lightgray;
}

p {
    background-color: white;
    height: 50px;
}

p span {
    background-color: #86fcd4;
    padding: 0 20px;
}

JS:

var x = 0;
var y = 0;
var z = 0;

function myMoveFunction() {
    document.getElementById("demo").innerHTML = z += 1;
}

function myEnterFunction() {
    document.getElementById("demo2").innerHTML = x += 1;
}

function myOverFunction() {
    document.getElementById("demo3").innerHTML = y += 1;
}
  • onmousemove : occurs every time the mouse pointer is moved over the div element.
  • onmouseenter : only occurs when the mouse pointer enters the div element.
  • onmouseover : occurs when the mouse pointer enters the div element, and its child elements (p and span).

Quick way to retrieve user information Active Directory

Well, if you know where your user lives in the AD hierarchy (e.g. quite possibly in the "Users" container, if it's a small network), you could also bind to the user account directly, instead of searching for it.

DirectoryEntry deUser = new DirectoryEntry("LDAP://cn=John Doe,cn=Users,dc=yourdomain,dc=com");

if (deUser != null)
{
  ... do something with your user
}

And if you're on .NET 3.5 already, you could even use the vastly expanded System.DirectorySrevices.AccountManagement namespace with strongly typed classes for each of the most common AD objects:

// bind to your domain
PrincipalContext pc = new PrincipalContext(ContextType.Domain, "LDAP://dc=yourdomain,dc=com");

// find the user by identity (or many other ways)
UserPrincipal user = UserPrincipal.FindByIdentity(pc, "cn=John Doe");

There's loads of information out there on System.DirectoryServices.AccountManagement - check out this excellent article on MSDN by Joe Kaplan and Ethan Wilansky on the topic.

Showing all session data at once?

here is code:

<?php echo '<pre>' . print_r($_SESSION, TRUE) . '</pre>'; ?>

PostgreSQL: how to convert from Unix epoch to date?

/* Current time */
 select now(); 

/* Epoch from current time;
   Epoch is number of seconds since 1970-01-01 00:00:00+00 */
 select extract(epoch from now()); 

/* Get back time from epoch */
 -- Option 1 - use to_timestamp function
 select to_timestamp( extract(epoch from now()));
 -- Option 2 - add seconds to 'epoch'
 select timestamp with time zone 'epoch' 
         + extract(epoch from now()) * interval '1 second';

/* Cast timestamp to date */
 -- Based on Option 1
 select to_timestamp(extract(epoch from now()))::date;
 -- Based on Option 2
 select (timestamp with time zone 'epoch' 
          + extract(epoch from now()) * interval '1 second')::date; 

 /* For column epoch_ms */
 select to_timestamp(extract(epoch epoch_ms))::date;

PostgreSQL Docs

SSH Private Key Permissions using Git GUI or ssh-keygen are too open

For *nix systems, the obvious fix is chmod 600 id_rsa ofc, but on windows 7 I had to hit my head against the wall for a while, but then I found the magic solution:

go to My Computer / Right Click / Properties / Advanced System Settings / Environment Variables and DELETE the variable (possibly from both system and user environment):

CYGWIN

Basically, its a flaw in mingw32 used by git windows binary, seeing all files 644 and all folders 755 always. Removing the environment variable does not change that behaviour, but it appearantly tells ssh.exe to ignore the problem. If you do set proper permissions to your id_rsa through explorers security settings (there really is no need to have any other user in there than your own, not "everyone", not "administrators", not "system". none. just you), you'll still be secure.

Now, why mingw32, a different system than cygwin, would make any use of the CYGWIN environment variable, is beyond me. Looks like a bug to me.

How to create and show common dialog (Error, Warning, Confirmation) in JavaFX 2.0?

This works since java 8u40:

Alert alert = new Alert(AlertType.INFORMATION, "Content here", ButtonType.OK);
alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
alert.show();

How to convert list data into json in java

Try like below with Gson Library.

Earlier Conversion List format were:

[Product [Id=1, City=Bengalore, Category=TV, Brand=Samsung, Name=Samsung LED, Type=LED, Size=32 inches, Price=33500.5, Stock=17.0], Product [Id=2, City=Bengalore, Category=TV, Brand=Samsung, Name=Samsung LED, Type=LED, Size=42 inches, Price=41850.0, Stock=9.0]]

and here the conversion source begins.

//** Note I have created the method toString() in Product class.

//Creating and initializing a java.util.List of Product objects
List<Product> productList = (List<Product>)productRepository.findAll();

//Creating a blank List of Gson library JsonObject
List<JsonObject> entities = new ArrayList<JsonObject>();

//Simply printing productList size
System.out.println("Size of productList is : " + productList.size());

//Creating a Iterator for productList
Iterator<Product> iterator = productList.iterator();

//Run while loop till Product Object exists.
while(iterator.hasNext()){

    //Creating a fresh Gson Object
    Gson gs = new Gson();

    //Converting our Product Object to JsonElement 
    //Object by passing the Product Object String value (iterator.next())
    JsonElement element = gs.fromJson (gs.toJson(iterator.next()), JsonElement.class);

    //Creating JsonObject from JsonElement
    JsonObject jsonObject = element.getAsJsonObject();

    //Collecting the JsonObject to List
    entities.add(jsonObject);

}

//Do what you want to do with Array of JsonObject
System.out.println(entities);

Converted Json Result is :

[{"Id":1,"City":"Bengalore","Category":"TV","Brand":"Samsung","Name":"Samsung LED","Type":"LED","Size":"32 inches","Price":33500.5,"Stock":17.0}, {"Id":2,"City":"Bengalore","Category":"TV","Brand":"Samsung","Name":"Samsung LED","Type":"LED","Size":"42 inches","Price":41850.0,"Stock":9.0}]

Hope this would help many guys!

Tensorflow image reading & display

After speaking with you in the comments, I believe that you can just do this using numpy/scipy. The ideas is to read the image in the numpy 3d-array and feed it into the variable.

from scipy import misc
import tensorflow as tf

img = misc.imread('01.png')
print img.shape    # (32, 32, 3)

img_tf = tf.Variable(img)
print img_tf.get_shape().as_list()  # [32, 32, 3]

Then you can run your graph:

init = tf.initialize_all_variables()
sess = tf.Session()
sess.run(init)
im = sess.run(img_tf)

and verify that it is the same:

import matplotlib.pyplot as plt
fig = plt.figure()
fig.add_subplot(1,2,1)
plt.imshow(im)
fig.add_subplot(1,2,2)
plt.imshow(img)
plt.show()

enter image description here

P.S. you mentioned: Since it's supposed to parallelize reading, it seems useful to know.. To which I can say that rarely in data-analysis reading of the data is the bottleneck. Most of your time you will spend training your model.

How to delete a row from GridView?

You are deleting the row from the gridview but you are then going and calling databind again which is just refreshing the gridview to the same state that the original datasource is in.

Either remove it from the datasource and then databind, or databind and remove it from the gridview without redatabinding.

Copy and paste content from one file to another file in vi

  1. Make sure you have the Vim version compiled with clipboard support
    • :echo has('clipboard') should return 1
    • if it returns 0 (for example Mac OS X, at least v10.11 (El Capitan), v10.9 (Mavericks) and v10.8 (Mountain Lion) - comes with a Vim version lacking clipboard support), you have to install a Vim version with clipboard support, say via brew install vim (don't forget to relaunch your terminal(s) after the installation)
  2. Enter a visual mode (V - multiline, v - plain, or Ctrlv - block-visual)
  3. Select line(s) you wish to copy
  4. "*y - to copy selected
  5. "*p - to paste copied

P.S:

  • you can replace steps 2-5 with the instructions from the answer by JayG, if you need to copy and paste a single line
  • to ease selecting lines, you can add set mouse+=a to your .vimrc - it will allow you to select lines in Vim using the mouse, while not selecting extraneous elements (like line numbers, etc.) NOTICE: it will block the ability to copy mouse-selected text to the system clipboard from Vim.

Error in setting JAVA_HOME

Follow the instruction in here.

JAVA_HOMEshould be like this

JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07

How to tune Tomcat 5.5 JVM Memory settings without using the configuration program

Create a setenv.(sh|bat) file in the tomcat/bin directory with the environment variables that you want modified.

The catalina script checks if the setenv script exists and runs it to set the environment variables. This way you can change the parameters to only one instance of tomcat and is easier to copy it to another instance.

Probably your configuration app has created the setenv script and thats why tomcat is ignoring the environment variables.

Bash foreach loop

cat `cat filenames.txt`

will do the trick

Regular expression for checking if capital letters are found consecutively in a string?

^([A-Z][a-z]+)+$

This looks for sequences of an uppercase letter followed by one or more lowercase letters. Consecutive uppercase letters will not match, as only one is allowed at a time, and it must be followed by a lowercase one.

How to get table list in database, using MS SQL 2008?

This should give you a list of all the tables in your database

SELECT Distinct TABLE_NAME FROM information_schema.TABLES

So you can use it similar to your database check.

If NOT EXISTS(SELECT Distinct TABLE_NAME FROM information_schema.TABLES Where TABLE_NAME = 'Your_Table')
BEGIN
    --CREATE TABLE Your_Table
END
GO

Content Security Policy "data" not working for base64 Images in Chrome 28

According to the grammar in the CSP spec, you need to specify schemes as scheme:, not just scheme. So, you need to change the image source directive to:

img-src 'self' data:;

What data type to use in MySQL to store images?

Perfect answer for your question can be found on MYSQL site itself.refer their manual(without using PHP)

http://forums.mysql.com/read.php?20,17671,27914

According to them use LONGBLOB datatype. with that you can only store images less than 1MB only by default,although it can be changed by editing server config file.i would also recommend using MySQL workBench for ease of database management

The module was expected to contain an assembly manifest

Check if the manifest is a valid xml file. I had the same problem by doing a DOS copy command at the end of the build, and it turns out that for some reason I can not understand "copy" was adding a strange character (->) at the end of the manifest files. The problem was solved by adding "/b" switch to force binary copy.

Difference between Date(dateString) and new Date(dateString)

I recently ran into this as well and this was a helpful post. I took the above Topera a step further and this works for me in both chrome and firefox:

var temp = new Date(  Date("2010-08-17 12:09:36")   );
alert(temp);

the internal call to Date() returns a string that new Date() can parse.

.aspx vs .ashx MAIN difference

.aspx is a rendered page. If you need a view, use an .aspx page. If all you need is backend functionality but will be staying on the same view, use an .ashx page.

javascript - Create Simple Dynamic Array

var arr = [];
while(mynumber--) {
    arr[mynumber] = String(mynumber+1);
}

Python iterating through object attributes

UPDATED

For python 3, you should use items() instead of iteritems()

PYTHON 2

for attr, value in k.__dict__.iteritems():
        print attr, value

PYTHON 3

for attr, value in k.__dict__.items():
        print(attr, value)

This will print

'names', [a list with names]
'tweet', [a list with tweet]

C# Switch-case string starting with

If you knew that the length of conditions you would care about would all be the same length then you could:

switch(mystring.substring(0, Math.Min(3, mystring.Length))
{
  case "abc":
    //do something
    break;
  case "xyz":
    //do something else
    break;
  default:
    //do a different thing
    break;
}

The Math.Min(3, mystring.Length) is there so that a string of less than 3 characters won't throw an exception on the sub-string operation.

There are extensions of this technique to match e.g. a bunch of 2-char strings and a bunch of 3-char strings, where some 2-char comparisons matching are then followed by 3-char comparisons. Unless you've a very large number of such strings though, it quickly becomes less efficient than simple if-else chaining for both the running code and the person who has to maintain it.

Edit: Added since you've now stated they will be of different lengths. You could do the pattern I mentioned of checking the first X chars and then the next Y chars and so on, but unless there's a pattern where most of the strings are the same length this will be both inefficient and horrible to maintain (a classic case of premature pessimisation).

The command pattern is mentioned in another answer, so I won't give details of that, as is that where you map string patterns to IDs, but they are option.

I would not change from if-else chains to command or mapping patterns to gain the efficiency switch sometimes has over if-else, as you lose more in the comparisons for the command or obtaining the ID pattern. I would though do so if it made code clearer.

A chain of if-else's can work pretty well, either with string comparisons or with regular expressions (the latter if you have comparisons more complicated than the prefix-matches so far, which would probably be simpler and faster, I'm mentioning reg-ex's just because they do sometimes work well with more general cases of this sort of pattern).

If you go for if-elses, try to consider which cases are going to happen most often, and make those tests happen before those for less-common cases (though of course if "starts with abcd" is a case to look for it would have to be checked before "starts with abc").

"Primary Filegroup is Full" in SQL Server 2008 Standard for no apparent reason

Anton,

As a best practice one should n't create user objects in the primary filegroup. When you have bandwidth, create a new file group and move the user objects and leave the system objects in primary.

The following queries will help you identify the space used in each file and the top tables that have highest number of rows and if there are any heaps. Its a good starting point to investigate this issue.

SELECT  
ds.name as filegroupname
, df.name AS 'FileName' 
, physical_name AS 'PhysicalName'
, size/128 AS 'TotalSizeinMB'
, size/128.0 - CAST(FILEPROPERTY(df.name, 'SpaceUsed') AS int)/128.0 AS 'AvailableSpaceInMB' 
, CAST(FILEPROPERTY(df.name, 'SpaceUsed') AS int)/128.0 AS 'ActualSpaceUsedInMB'
, (CAST(FILEPROPERTY(df.name, 'SpaceUsed') AS int)/128.0)/(size/128)*100. as '%SpaceUsed'
FROM sys.database_files df LEFT OUTER JOIN sys.data_spaces ds  
    ON df.data_space_id = ds.data_space_id;

EXEC xp_fixeddrives
select  t.name as TableName,  
    i.name as IndexName, 
    p.rows as Rows
from sys.filegroups fg (nolock) join sys.database_files df (nolock)
    on fg.data_space_id = df.data_space_id join sys.indexes i (nolock) 
    on df.data_space_id = i.data_space_id join sys.tables t (nolock)
    on i.object_id = t.object_id join sys.partitions p (nolock)
on t.object_id = p.object_id and i.index_id = p.index_id  
where fg.name = 'PRIMARY' and t.type = 'U'  
order by rows desc
select  t.name as TableName,  
    i.name as IndexName, 
    p.rows as Rows
from sys.filegroups fg (nolock) join sys.database_files df (nolock)
    on fg.data_space_id = df.data_space_id join sys.indexes i (nolock) 
    on df.data_space_id = i.data_space_id join sys.tables t (nolock)
    on i.object_id = t.object_id join sys.partitions p (nolock)
on t.object_id = p.object_id and i.index_id = p.index_id  
where fg.name = 'PRIMARY' and t.type = 'U' and i.index_id = 0 
order by rows desc

log4j configuration via JVM argument(s)?

Late to the party as since 2015, Log4J 1.x has reached EOL.

Log4J 2.x onwards the JVM option should be -Dlog4j.configurationFile=<filename>


P.S. <filename> could be a file relative to the class path without the file: as suggested in the other answers.

How to unmerge a Git merge?

If you haven't committed the merge, then use:

git merge --abort

'const string' vs. 'static readonly string' in C#

const

public const string MyStr;

is a compile time constant (you can use it as the default parameter for a method parameter for example), and it will not be obfuscated if you use such technology

static readonly

public static readonly string MyStr;

is runtime constant. It means that it is evaluated when the application is launched and not before. This is why it can't be used as the default parameter for a method (compilation error) for example. The value stored in it can be obfuscated.

EntityType 'IdentityUserLogin' has no key defined. Define the key for this EntityType

My issue was similar - I had a new table i was creating that ahd to tie in to the identity users. After reading the above answers, realized it had to do with IsdentityUser and the inherited properites. I already had Identity set up as its own Context, so to avoid inherently tying the two together, rather than using the related user table as a true EF property, I set up a non-mapped property with the query to get the related entities. (DataManager is set up to retrieve the current context in which OtherEntity exists.)

    [Table("UserOtherEntity")]
        public partial class UserOtherEntity
        {
            public Guid UserOtherEntityId { get; set; }
            [Required]
            [StringLength(128)]
            public string UserId { get; set; }
            [Required]
            public Guid OtherEntityId { get; set; }
            public virtual OtherEntity OtherEntity { get; set; }
        }

    public partial class UserOtherEntity : DataManager
        {
            public static IEnumerable<OtherEntity> GetOtherEntitiesByUserId(string userId)
            {
                return Connect2Context.UserOtherEntities.Where(ue => ue.UserId == userId).Select(ue => ue.OtherEntity);
            }
        }

public partial class ApplicationUser : IdentityUser
    {
        public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
        {
            // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
            var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
            // Add custom user claims here
            return userIdentity;
        }

        [NotMapped]
        public IEnumerable<OtherEntity> OtherEntities
        {
            get
            {
                return UserOtherEntities.GetOtherEntitiesByUserId(this.Id);
            }
        }
    }

Install python 2.6 in CentOS

No, that's it. You might want to make sure you have all optional library headers installed too so you don't have to recompile it later. They are listed in the documentation I think.

Also, you can install it even in the standard path if you do make altinstall. That way it won't override your current default "python".

How to find the path of the local git repository when I am possibly in a subdirectory

git rev-parse --show-toplevel

could be enough if executed within a git repo.
From git rev-parse man page:

--show-toplevel

Show the absolute path of the top-level directory.

For older versions (before 1.7.x), the other options are listed in "Is there a way to get the git root directory in one command?":

git rev-parse --git-dir

That would give the path of the .git directory.


The OP mentions:

git rev-parse --show-prefix

which returns the local path under the git repo root. (empty if you are at the git repo root)


Note: for simply checking if one is in a git repo, I find the following command quite expressive:

git rev-parse --is-inside-work-tree

And yes, if you need to check if you are in a .git git-dir folder:

git rev-parse --is-inside-git-dir

How do I rename a file using VBScript?

I see only one reason your code to not work, missed quote after file name string:

VBScript:

FSO.GetFile("MyFile.txt[missed_quote_here]).Name = "Hello.txt"

Split bash string by newline characters

Another way:

x=$'Some\nstring'
readarray -t y <<<"$x"

Or, if you don't have bash 4, the bash 3.2 equivalent:

IFS=$'\n' read -rd '' -a y <<<"$x"

You can also do it the way you were initially trying to use:

y=(${x//$'\n'/ })

This, however, will not function correctly if your string already contains spaces, such as 'line 1\nline 2'. To make it work, you need to restrict the word separator before parsing it:

IFS=$'\n' y=(${x//$'\n'/ })

...and then, since you are changing the separator, you don't need to convert the \n to space anymore, so you can simplify it to:

IFS=$'\n' y=($x)

This approach will function unless $x contains a matching globbing pattern (such as "*") - in which case it will be replaced by the matched file name(s). The read/readarray methods require newer bash versions, but work in all cases.

How to detect reliably Mac OS X, iOS, Linux, Windows in C preprocessor?

There are predefined macros that are used by most compilers, you can find the list here. GCC compiler predefined macros can be found here. Here is an example for gcc:

#if defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(__NT__)
   //define something for Windows (32-bit and 64-bit, this part is common)
   #ifdef _WIN64
      //define something for Windows (64-bit only)
   #else
      //define something for Windows (32-bit only)
   #endif
#elif __APPLE__
    #include <TargetConditionals.h>
    #if TARGET_IPHONE_SIMULATOR
         // iOS Simulator
    #elif TARGET_OS_IPHONE
        // iOS device
    #elif TARGET_OS_MAC
        // Other kinds of Mac OS
    #else
    #   error "Unknown Apple platform"
    #endif
#elif __linux__
    // linux
#elif __unix__ // all unices not caught above
    // Unix
#elif defined(_POSIX_VERSION)
    // POSIX
#else
#   error "Unknown compiler"
#endif

The defined macros depend on the compiler that you are going to use.

The _WIN64 #ifdef can be nested into the _WIN32 #ifdef because _WIN32 is even defined when targeting the Windows x64 version. This prevents code duplication if some header includes are common to both (also WIN32 without underscore allows IDE to highlight the right partition of code).

Merging 2 branches together in GIT

Case: If you need to ignore the merge commit created by default, follow these steps.

Say, a new feature branch is checked out from master having 2 commits already,

  • "Added A" , "Added B"

Checkout a new feature_branch

  • "Added C" , "Added D"

Feature branch then adds two commits-->

  • "Added E", "Added F"

enter image description here

Now if you want to merge feature_branch changes to master, Do git merge feature_branch sitting on the master.

This will add all commits into master branch (4 in master + 2 in feature_branch = total 6) + an extra merge commit something like 'Merge branch 'feature_branch'' as the master is diverged.

If you really need to ignore these commits (those made in FB) and add the whole changes made in feature_branch as a single commit like 'Integrated feature branch changes into master', Run git merge feature_merge --no-commit.

With --no-commit, it perform the merge and stop just before creating a merge commit, We will have all the added changes in feature branch now in master and get a chance to create a new commit as our own.

Read here for more : https://git-scm.com/docs/git-merge

How to convert date in to yyyy-MM-dd Format?

Modern answer: Use LocalDate from java.time, the modern Java date and time API, and its toString method:

    LocalDate date = LocalDate.of(2012, Month.DECEMBER, 1); // get from somewhere
    String formattedDate = date.toString();
    System.out.println(formattedDate);

This prints

2012-12-01

A date (whether we’re talking java.util.Date or java.time.LocalDate) doesn’t have a format in it. All it’s got is a toString method that produces some format, and you cannot change the toString method. Fortunately, LocalDate.toString produces exactly the format you asked for.

The Date class is long outdated, and the SimpleDateFormat class that you tried to use, is notoriously troublesome. I recommend you forget about those classes and use java.time instead. The modern API is so much nicer to work with.

Except: it happens that you get a Date from a legacy API that you cannot change or don’t want to change just now. The best thing you can do with it is convert it to java.time.Instant and do any further operations from there:

    Date oldfashoinedDate = // get from somewhere
    LocalDate date = oldfashoinedDate.toInstant()
            .atZone(ZoneId.of("Asia/Beirut"))
            .toLocalDate();

Please substitute your desired time zone if it didn’t happen to be Asia/Beirut. Then proceed as above.

Link: Oracle tutorial: Date Time, explaining how to use java.time.

How to convert CSV file to multiline JSON?

As slight improvement to @MONTYHS answer, iterating through a tup of fieldnames:

import csv
import json

csvfilename = 'filename.csv'
jsonfilename = csvfilename.split('.')[0] + '.json'
csvfile = open(csvfilename, 'r')
jsonfile = open(jsonfilename, 'w')
reader = csv.DictReader(csvfile)

fieldnames = ('FirstName', 'LastName', 'IDNumber', 'Message')

output = []

for each in reader:
  row = {}
  for field in fieldnames:
    row[field] = each[field]
output.append(row)

json.dump(output, jsonfile, indent=2, sort_keys=True)

Is it a good practice to use try-except-else in Python?

Is it a good practice to use try-except-else in python?

The answer to this is that it is context dependent. If you do this:

d = dict()
try:
    item = d['item']
except KeyError:
    item = 'default'

It demonstrates that you don't know Python very well. This functionality is encapsulated in the dict.get method:

item = d.get('item', 'default')

The try/except block is a much more visually cluttered and verbose way of writing what can be efficiently executing in a single line with an atomic method. There are other cases where this is true.

However, that does not mean that we should avoid all exception handling. In some cases it is preferred to avoid race conditions. Don't check if a file exists, just attempt to open it, and catch the appropriate IOError. For the sake of simplicity and readability, try to encapsulate this or factor it out as apropos.

Read the Zen of Python, understanding that there are principles that are in tension, and be wary of dogma that relies too heavily on any one of the statements in it.

View more than one project/solution in Visual Studio

After a long research and different experiments the easiest way "FOR MAC USERS" is to create a script:

open -a "Visual Studio" \
"path to first sln" \
"path to second sln" \
...

:D

jquery select element by xpath

If you are debugging or similar - In chrome developer tools, you can simply use

$x('/html/.//div[@id="text"]')

What are the differences among grep, awk & sed?

I just want to mention a thing, there are many tools can do text processing, e.g. sort, cut, split, join, paste, comm, uniq, column, rev, tac, tr, nl, pr, head, tail.....

they are very handy but you have to learn their options etc.

A lazy way (not the best way) to learn text processing might be: only learn grep , sed and awk. with this three tools, you can solve almost 99% of text processing problems and don't need to memorize above different cmds and options. :)

AND, if you 've learned and used the three, you knew the difference. Actually, the difference here means which tool is good at solving what kind of problem.

a more lazy way might be learning a script language (python, perl or ruby) and do every text processing with it.

How to prevent ENTER keypress to submit a web form?

Another approach is to append the submit input button to the form only when it is supposed to be submited and replace it by a simple div during the form filling

In jQuery, how do I select an element by its name attribute?

another way

$('input:radio[name=theme]').filter(":checked").val()

How to check if String value is Boolean type in Java?

Apache commons-lang3 has BooleanUtils with a method toBooleanObject:

BooleanUtils.toBooleanObject(String str)

// where: 

BooleanUtils.toBooleanObject(null)    = null
BooleanUtils.toBooleanObject("true")  = Boolean.TRUE
BooleanUtils.toBooleanObject("false") = Boolean.FALSE
BooleanUtils.toBooleanObject("on")    = Boolean.TRUE
BooleanUtils.toBooleanObject("ON")    = Boolean.TRUE
BooleanUtils.toBooleanObject("off")   = Boolean.FALSE
BooleanUtils.toBooleanObject("oFf")   = Boolean.FALSE
BooleanUtils.toBooleanObject("blue")  = null

How to escape double quotes in JSON

To escape backslashes that cause problems for JSON data I use this function.

//escape backslash to avoid errors
var escapeJSON = function(str) {
    return str.replace(/\\/g,'\\');
};

Disabled form fields not submitting data

Use the CSS pointer-events:none on fields you want to "disable" (possibly together with a greyed background) which allows the POST action, like:

<input type="text" class="disable">

.disable{
pointer-events:none;
background:grey;
}

Ref: https://developer.mozilla.org/en-US/docs/Web/CSS/pointer-events

AngularJS - Any way for $http.post to send request parameters instead of JSON?

   .controller('pieChartController', ['$scope', '$http', '$httpParamSerializerJQLike', function($scope, $http, $httpParamSerializerJQLike) {
        var data = {
                TimeStamp : "2016-04-25 12:50:00"
        };
        $http({
            method: 'POST',
            url: 'serverutilizationreport',
            headers: {'Content-Type': 'application/x-www-form-urlencoded'},
            data: $httpParamSerializerJQLike(data),
        }).success(function () {});
    }
  ]);

How to download a branch with git?

We can download a specified branch by using following magical command:

git clone -b < branch name > <remote_repo url> 

Is it possible to change the location of packages for NuGet?

In addition to Shane Kms answer, if you've activated Nuget Package Restore, you edit the NuGet.config located in the .nuget-folder as follows:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <repositoryPath>..\..\ExtLibs\Packages</repositoryPath>
</configuration>

Notice the extra "..\", as it backtracks from the .nuget-folder and not the solution folder.

How to block calls in android

In android-N, this feature is included in it. check Number-blocking update for android N

Android N now supports number-blocking in the platform and provides a framework API to let service providers maintain a blocked-number list. The default SMS app, the default phone app, and provider apps can read from and write to the blocked-number list. The list is not accessible to other app.

advantage of are:

  1. Numbers blocked on calls are also blocked on texts
  2. Blocked numbers can persist across resets and devices through the Backup & Restore feature
  3. Multiple apps can use the same blocked numbers list

For more information, see android.provider.BlockedNumberContract

Update an existing project.

To compile your app against the Android N platform, you need to use the Java 8 Developer Kit (JDK 8), and in order to use some tools with Android Studio 2.1, you need to install the Java 8 Runtime Environment (JRE 8).

Open the build.gradle file for your module and update the values as follows:

android {
  compileSdkVersion 'android-N'
  buildToolsVersion 24.0.0 rc1
  ...

  defaultConfig {
     minSdkVersion 'N'
     targetSdkVersion 'N'
     ...
  }
  ...
}

How to make a countdown timer in Android?

public class Scan extends AppCompatActivity {
int minute;
long min;
TextView tv_timer;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_scan2);
    tv_timer=findViewById(R.id.tv_timer);
    minute=Integer.parseInt("Your time in string form like 10");
    min= minute*60*1000;
    counter(min);
}
private void counter(long min) {
    CountDownTimer timer = new CountDownTimer(min, 1000) {
        public void onTick(long millisUntilFinished) {
            int seconds = (int) (millisUntilFinished / 1000) % 60;
            int minutes = (int) ((millisUntilFinished / (1000 * 60)) % 60);
            int hours = (int) ((millisUntilFinished / (1000 * 60 * 60)) % 24);
            tv_timer.setText(String.format("%d:%d:%d", hours, minutes, seconds));
        }
        public void onFinish() {
            Toast.makeText(getApplicationContext(), "Your time has been completed",
                    Toast.LENGTH_LONG).show();
        }
    };
    timer.start();
}

}

Retrieve Button value with jQuery

if you want to get the value attribute (buttonValue) then I'd use:

<script type="text/javascript">
    $(document).ready(function() {
        $('.my_button').click(function() {
            alert($(this).attr('value'));
        });
    });
</script>

Python Pip install Error: Unable to find vcvarsall.bat. Tried all solutions

After doing a lot of things, I upgraded pip, setuptools and virtualenv.

  1. python -m pip install -U pip
  2. pip install -U setuptools
  3. pip install -U virtualenv

I did steps 1, 2 in my virtual environment as well as globally. Next, I installed the package through pip and it worked.

jQuery UI " $("#datepicker").datepicker is not a function"

Have you tried using $("#<%= txtDateElementId.ClientID %>").datepicker(); instead of $("#txtDateElementId").datepicker(); when selecting an element by ID using JQuery.

Python mysqldb: Library not loaded: libmysqlclient.18.dylib

I had this issue and it took me for a while to figure out how to fix that.

My case is slightly different. My MySQL server is of version 5.1.x. And somehow I upgraded my MySQL-python from 1.2.3 to 1.2.5. And I kept getting this issue since then event I added the following soft link.

libmysqlclient.18.dylib -> /usr/local/mysql/lib/libmysqlclient.18.dylib

It turns out that for MySQL 5.1.x there is no libmysqlclient.18.dylib, but only libmysqlclient.16.dylib. You can fix this issue either by downgrade your MySQL-python to 1.2.3 or upgrade your MySQL server to 5.6.x (I haven't tried 5.5.x.)

I downgraded the library to 1.2.3 since upgrading MySQL is not an option for me.

Python equivalent for HashMap

You need a dict:

my_dict = {'cheese': 'cake'}

Example code (from the docs):

>>> a = dict(one=1, two=2, three=3)
>>> b = {'one': 1, 'two': 2, 'three': 3}
>>> c = dict(zip(['one', 'two', 'three'], [1, 2, 3]))
>>> d = dict([('two', 2), ('one', 1), ('three', 3)])
>>> e = dict({'three': 3, 'one': 1, 'two': 2})
>>> a == b == c == d == e
True

You can read more about dictionaries here.

Where is Developer Command Prompt for VS2013?

Visual studio command prompt is nothing but the regular command prompt where few environment variables are set by default. This variables are set in the batch script : C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Tools\VsDevCmd.bat . So basically to get a visual studio command prompt for a particular version, just open regular command prompt and run this batch script : C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Tools\VsDevCmd.bat (Change the visual studio version based on your installed version). Voila you have got the visual studio command prompt. You can write a script to run the batch file and open cmd.exe.

How to get content body from a httpclient call?

The way you are using await/async is poor at best, and it makes it hard to follow. You are mixing await with Task'1.Result, which is just confusing. However, it looks like you are looking at a final task result, rather than the contents.

I've rewritten your function and function call, which should fix your issue:

async Task<string> GetResponseString(string text)
{
    var httpClient = new HttpClient();

    var parameters = new Dictionary<string, string>();
    parameters["text"] = text;

    var response = await httpClient.PostAsync(BaseUri, new FormUrlEncodedContent(parameters));
    var contents = await response.Content.ReadAsStringAsync();

    return contents;
}

And your final function call:

Task<string> result = GetResponseString(text);
var finalResult = result.Result;

Or even better:

var finalResult = await GetResponseString(text);

What is the difference between Bootstrap .container and .container-fluid classes?

Both .container and .container-fluid are responsive (i.e. they change the layout based on the screen width), but in different ways (I know, the naming doesn't make it sound that way).

Short Answer:

.container is jumpy / choppy resizing, and

.container-fluid is continuous / fine resizing at width: 100%.

From a functionality perspective:

.container-fluid continuously resizes as you change the width of your window/browser by any amount, leaving no extra empty space on the sides ever, unlike how .container does. (Hence the naming: "fluid" as opposed to "digital", "discrete", "chunked", or "quantized").

.container resizes in chunks at several certain widths. In other words, it will be different specific aka "fixed" widths different ranges of screen widths.

Semantics: "fixed width"

You can see how naming confusion can arise. Technically, we can say .container is "fixed width", but it is fixed only in the sense that it doesn't resize at every granular width. It's actually not "fixed" in the sense that it's always stays at a specific pixel width, since it actually can change size.

From a fundamental perspective:

.container-fluid has the CSS property width: 100%;, so it continually readjusts at every screen width granularity.

.container-fluid {
  width: 100%;
}

.container has something like "width = 800px" (or em, rem etc.), a specific pixel width value at different screen widths. This of course is what causes the element width to abruptly jump to a different width when the screen width crosses a screen width threshold. And that threshold is governed by CSS3 media queries, which allow you to apply different styles for different conditions, such as screen width ranges.

@media screen and (max-width: 400px){
  .container {
    width: 123px;
  }
}
@media screen and (min-width: 401px) and (max-width: 800px){

  .container {
    width: 456px;
  }
}
@media screen and (min-width: 801px){
  .container {
    width: 789px;
  }
}

Beyond

You can make any fixed widths element responsive via media queries, not just .container elements, since media queries is exactly how .container is implemented by bootstrap in the background (see JKillian's answer for the code).

regex string replace

Just change + to -:

str = str.replace(/[^a-z0-9-]/g, "");

You can read it as:

  1. [^ ]: match NOT from the set
  2. [^a-z0-9-]: match if not a-z, 0-9 or -
  3. / /g: do global match

More information:

How to create a pivot query in sql server without aggregate function

SELECT *
FROM
(
SELECT [Period], [Account], [Value]
FROM TableName
) AS source
PIVOT
(
    MAX([Value])
    FOR [Period] IN ([2000], [2001], [2002])
) as pvt

Another way,

SELECT ACCOUNT,
      MAX(CASE WHEN Period = '2000' THEN Value ELSE NULL END) [2000],
      MAX(CASE WHEN Period = '2001' THEN Value ELSE NULL END) [2001],
      MAX(CASE WHEN Period = '2002' THEN Value ELSE NULL END) [2002]
FROM tableName
GROUP BY Account

How to automatically reload a page after a given period of inactivity

Using LocalStorage to keep track of the last time of activity, we can write the reload function as follows

function reloadPage(expiryDurationMins) {
    const lastInteraction = window.localStorage.getItem('lastinteraction')
    if (!lastInteraction) return // no interaction recorded since page load
    const inactiveDurationMins = (Date.now() - Number(lastInteraction)) / 60000
    const pageExpired = inactiveDurationMins >= expiryDurationMins
    if (pageExpired) window.location.reload()
}

Then we create an arrow function which saves the last time of interaction in milliseconds(String)

const saveLastInteraction = () => window.localStorage.setItem('last', Date.now().toString())

We will need to listen to the beforeunload event in the browser to clear our lastinteraction record so we don't get stuck in an infinite reload loop.

window.addEventListener('beforeunload', () => window.localStorage.removeItem('lastinteraction'))

The user activity events we will need to monitor would be mousemove and keypress. We store the last interaction time when the user moves the mouse or presses a key on the keyboard

window.addEventListener('mousemove', saveLastInteraction)
window.addEventListener('keypress', saveLastInteraction)

To set up our final listener, we will use the load event. On page load, we use the setInterval function to check if the page has expired after a certain period.

const expiryDurationMins = 1

window.addEventListener('load', setInterval.bind(null, reloadPage.bind(null, expiryDurationMins), 1000))

wildcard * in CSS for classes

What you need is called attribute selector. An example, using your html structure, is the following:

div[class^="tocolor-"], div[class*=" tocolor-"] {
    color:red 
}

In the place of div you can add any element or remove it altogether, and in the place of class you can add any attribute of the specified element.

[class^="tocolor-"] — starts with "tocolor-".
[class*=" tocolor-"] — contains the substring "tocolor-" occurring directly after a space character.

Demo: http://jsfiddle.net/K3693/1/

More information on CSS attribute selectors, you can find here and here. And from MDN Docs MDN Docs

How can I link to a specific glibc version?

In my opinion, the laziest solution (especially if you don't rely on latest bleeding edge C/C++ features, or latest compiler features) wasn't mentioned yet, so here it is:

Just build on the system with the oldest GLIBC you still want to support.

This is actually pretty easy to do nowadays with technologies like chroot, or KVM/Virtualbox, or docker, even if you don't really want to use such an old distro directly on any pc. In detail, to make a maximum portable binary of your software I recommend following these steps:

  1. Just pick your poison of sandbox/virtualization/... whatever, and use it to get yourself a virtual older Ubuntu LTS and compile with the gcc/g++ it has in there by default. That automatically limits your GLIBC to the one available in that environment.

  2. Avoid depending on external libs outside of foundational ones: like, you should dynamically link ground-level system stuff like glibc, libGL, libxcb/X11/wayland things, libasound/libpulseaudio, possibly GTK+ if you use that, but otherwise preferrably statically link external libs/ship them along if you can. Especially mostly self-contained libs like image loaders, multimedia decoders, etc can cause less breakage on other distros (breakage can be caused e.g. if only present somewhere in a different major version) if you statically ship them.

With that approach you get an old-GLIBC-compatible binary without any manual symbol tweaks, without doing a fully static binary (that may break for more complex programs because glibc hates that, and which may cause licensing issues for you), and without setting up any custom toolchain, any custom glibc copy, or whatever.

How to solve PHP error 'Notice: Array to string conversion in...'

<?php
ob_start();
var_dump($_POST['C']);
$result = ob_get_clean();
?>

if you want to capture the result in a variable

Removing display of row names from data frame

Yes I know it is over half a year later and a tad late, BUT

row.names(df) <- NULL

does work. For me at least :-)

And if you have important information in row.names like dates for example, what I do is just :

df$Dates <- as.Date(row.names(df))

This will add a new column on the end but if you want it at the beginning of your data frame

df <- df[,c(7,1,2,3,4,5,6,...)]

Hope this helps those from Google :)

How to add Certificate Authority file in CentOS 7

Find *.pem file and place it to the anchors sub-directory or just simply link the *.pem file to there.

yum install -y ca-certificates
update-ca-trust force-enable
sudo ln -s /etc/ssl/your-cert.pem /etc/pki/ca-trust/source/anchors/your-cert.pem
update-ca-trust

Linux cmd to search for a class file among jars irrespective of jar path

Just go to the directory which contains jars and insert below command:

find *.jar | xargs grep className.class

Hope this helps!

Get element type with jQuery

also you can use:

$("#elementId").get(0).tagName

TypeError: 'undefined' is not an object

I'm not sure how you could just check if something isn't undefined and at the same time get an error that it is undefined. What browser are you using?

You could check in the following way (extra = and making length a truthy evaluation)

if (typeof(sub.from) !== 'undefined' && sub.from.length) {

[update]

I see that you reset sub and thereby reset sub.from but fail to re check if sub.from exist:

for (var i = 0; i < sub.from.length; i++) {//<== assuming sub.from.exist
            mainid = sub.from[i]['id'];
            var sub = afcHelper_Submissions[mainid]; // <== re setting sub

My guess is that the error is not on the if statement but on the for(i... statement. In Firebug you can break automatically on an error and I guess it'll break on that line (not on the if statement).

I ran into a merge conflict. How can I abort the merge?

I found the following worked for me (revert a single file to pre-merge state):

git reset *currentBranchIntoWhichYouMerged* -- *fileToBeReset*

Android ClassNotFoundException: Didn't find class on path

In my case it was proguard minification process that removed some important classes from my production apk.

The solution was to edit the proguard-rules.pro file and add the following:

-keep class com.someimportant3rdpartypackage.** { *; }

Android: Rotate image in imageview by an angle

I think the best method :)

int angle = 0;
imageView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            angle = angle + 90;
            imageView.setRotation(angle);
        }
    });

Overlaying a DIV On Top Of HTML 5 Video

There you go , i hope this helps

http://jsfiddle.net/kNMnr/

here is the CSS also

#video_box{
    float:left;
}
#video_overlays {
position:absolute;
float:left;
    width:640px;
    min-height:370px;
    background-color:#000;
    z-index:300000;
}

Loading another html page from javascript

You can include a .js file which has the script to set the

window.location.href = url;

Where url would be the url you wish to load.

Adding placeholder attribute using Jquery

you just need to put this

($('#{{ form.email.id_for_label }}').attr("placeholder","Work email address"));

($('#{{ form.password1.id_for_label }}').attr("placeholder","Password"));

How can I multiply all items in a list together with Python?

Numpy has the prod() function that returns the product of a list, or in this case since it's numpy, it's the product of an array over a given axis:

import numpy
a = [1,2,3,4,5,6]
b = numpy.prod(a)

...or else you can just import numpy.prod():

from numpy import prod
a = [1,2,3,4,5,6]
b = prod(a)

Maven Jacoco Configuration - Exclude classes/packages from report not working

Here is the working sample in pom.xml file.

    <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <version>${jacoco.version}</version>


        <executions>
            <execution>
                <id>prepare-agent</id>
                <goals>
                    <goal>prepare-agent</goal>
                </goals>
            </execution>
            <execution>
                <id>post-unit-test</id>
                <phase>test</phase>
                <goals>
                    <goal>report</goal>
                </goals>

            </execution>

            <execution>
                <id>default-check</id>
                <goals>
                    <goal>check</goal>
                </goals>

            </execution>
        </executions>
        <configuration>
            <dataFile>target/jacoco.exec</dataFile>
            <!-- Sets the output directory for the code coverage report. -->
            <outputDirectory>target/jacoco-ut</outputDirectory>
            <rules>
                <rule implementation="org.jacoco.maven.RuleConfiguration">
                    <element>PACKAGE</element>
                    <limits>
                        <limit implementation="org.jacoco.report.check.Limit">
                            <counter>COMPLEXITY</counter>
                            <value>COVEREDRATIO</value>
                            <minimum>0.00</minimum>
                        </limit>
                    </limits>
                </rule>
            </rules>
            <excludes>
                <exclude>com/pfj/fleet/dao/model/**/*</exclude>
            </excludes>
            <systemPropertyVariables>

                <jacoco-agent.destfile>target/jacoco.exec</jacoco-agent.destfile>
            </systemPropertyVariables>
        </configuration>
    </plugin>

Android Studio doesn't see device

It's my first time running Android project today through Android Studio since its 2.x version, and I have the same problem. However, this is with the Flutter plugin. I have a workaround for people with similar setup.

My setup:

  • macOS Mojave on MacBook with Type-C-to-USB dongle
  • Android 6.0
  • Android Studio 3.4.1: Android SDK 9.+, 6.0
  • On Mac, ANDROID_HOME is defined, PATH includes all the required tool paths

Observation

  • adb devices gives the correct device info;
  • flutter devices shows correct device info with more details;
  • Android Studio's Connection Assistant shows Android as detected USB device;
  • Toolbar shows <no devices>;
  • AVD manager shows no such a device.

My workaround

  • Open Terminal and cd to my project root;
  • Run flutter run and the app is correctly deployed and runs fine;

After that, my observation

  • Toolbar shows my device name; I can then run everything from toolbar directly, including Hot Reload;
  • USB config on my device automatically switches to PTP from the default MTP;
  • AVD Manager still does not show my device. Shame!

But at least I'm no longer blocked.

Reference:

Setting CSS pseudo-class rules from JavaScript

One option you could consider is using CSS variables. The idea is that you set the property you want to change to a CSS variable. Then, within your JS, change that variable's value.

See example below

_x000D_
_x000D_
function changeColor(newColor) {
  document.documentElement.style.setProperty("--anchor-hover-color", newColor);
  // ^^^^^^^^^^^-- select the root 
}
_x000D_
:root {
  --anchor-hover-color: red;
}

a:hover { 
  color: var(--anchor-hover-color); 
}
_x000D_
<a href="#">Hover over me</a>

<button onclick="changeColor('lime')">Change to lime</button>
<button onclick="changeColor('red')">Change to red</button>
_x000D_
_x000D_
_x000D_

How to make a div 100% height of the browser window

There are a couple of CSS 3 measurement units called:

Viewport-Percentage (or Viewport-Relative) Lengths

What are Viewport-Percentage Lengths?

From the linked W3 Candidate Recommendation above:

The viewport-percentage lengths are relative to the size of the initial containing block. When the height or width of the initial containing block is changed, they are scaled accordingly.

These units are vh (viewport height), vw (viewport width), vmin (viewport minimum length) and vmax (viewport maximum length).

How can this be used to make a divider fill the height of the browser?

For this question, we can make use of vh: 1vh is equal to 1% of the viewport's height. That is to say, 100vh is equal to the height of the browser window, regardless of where the element is situated in the DOM tree:

HTML

<div></div>

CSS

div {
    height: 100vh;
}

This is literally all that's needed. Here is a JSFiddle example of this in use.

What browsers support these new units?

This is currently supported on all up-to-date major browsers apart from Opera Mini. Check out Can I use... for further support.

How can this be used with multiple columns?

In the case of the question at hand, featuring a left and a right divider, here is a JSFiddle example showing a two-column layout involving both vh and vw.

How is 100vh different to 100%?

Take this layout for example:

<body style="height:100%">
    <div style="height:200px">
        <p style="height:100%; display:block;">Hello, world!</p>
    </div>
</body>

The p tag here is set to 100% height, but because its containing div has 200 pixels height, 100% of 200 pixels becomes 200 pixels, not 100% of the body height. Using 100vh instead means that the p tag will be 100% height of the body regardless of the div height. Take a look at this accompanying JSFiddle to easily see the difference!

SQL Server procedure declare a list

Alternative to @Peter Monks.

If the number in the 'in' statement is small and fixed.

DECLARE @var1 varchar(30), @var2 varchar(30), @var3  varchar(30);

SET @var1 = 'james';
SET @var2 = 'same';
SET @var3 = 'dogcat';

Select * FROM Database Where x in (@var1,@var2,@var3);

What is the behavior difference between return-path, reply-to and from?

I had to add a Return-Path header in emails send by a Redmine instance. I agree with greatwolf only the sender can determine a correct (non default) Return-Path. The case is the following : E-mails are send with the default email address : [email protected] But we want that the real user initiating the action receives the bounce emails, because he will be the one knowing how to fix wrong recipients emails (and not the application adminstrators that have other cats to whip :-) ). We use this and it works perfectly well with exim on the application server and zimbra as the final company mail server.

How to center a navigation bar with CSS or HTML?

If you have your navigation <ul> with class #nav Then you need to put that <ul> item within a div container. Make your div container the 100% width. and set the text-align: element to center in the div container. Then in your <ul> set that class to have 3 particular elements: text-align:center; position: relative; and display: inline-block;

that should center it.

How to do a FULL OUTER JOIN in MySQL?

You can just convert a full outer join, e.g.

SELECT fields
FROM firsttable
FULL OUTER JOIN secondtable ON joincondition

into:

SELECT fields
FROM firsttable
LEFT JOIN secondtable ON joincondition
UNION ALL
SELECT fields (replacing any fields from firsttable with NULL)
FROM secondtable
WHERE NOT EXISTS (SELECT 1 FROM firsttable WHERE joincondition)

Or if you have at least one column, say foo, in firsttable that is NOT NULL, you can do:

SELECT fields
FROM firsttable
LEFT JOIN secondtable ON joincondition
UNION ALL
SELECT fields
FROM firsttable
RIGHT JOIN secondtable ON joincondition
WHERE firsttable.foo IS NULL

top align in html table?

<TABLE COLS="3" border="0" cellspacing="0" cellpadding="0">
    <TR style="vertical-align:top">
        <TD>
            <!-- The log text-box -->
            <div style="height:800px; width:240px; border:1px solid #ccc; font:16px/26px Georgia, Garamond, Serif; overflow:auto;">
                Log:
            </div>
        </TD>
        <TD>
            <!-- The 2nd column -->
        </TD>
        <TD>
            <!-- The 3rd column -->
        </TD>
    </TR>
</TABLE>

How to display an IFRAME inside a jQuery UI dialog

Although this is a old post, I have spent 3 hours to fix my issue and I think this might help someone in future.

Here is my jquery-dialog hack to show html content inside an <iframe> :

let modalProperties = {autoOpen: true, width: 900, height: 600, modal: true, title: 'Modal Title'};
let modalHtmlContent = '<div>My Content First div</div><div>My Content Second div</div>';

// create wrapper iframe
let wrapperIframe = $('<iframe src="" frameborder="0" style="width:100%; height:100%;"></iframe>');

// create jquery dialog by a 'div' with 'iframe' appended
$("<div></div>").append(wrapperIframe).dialog(modalProperties);

// insert html content to iframe 'body'
let wrapperIframeDocument = wrapperIframe[0].contentDocument;
let wrapperIframeBody = $('body', wrapperIframeDocument);
wrapperIframeBody.html(modalHtmlContent);

jsfiddle demo

Android studio - Failed to find target android-18

This will also happen if you have written compileSdkVersion = 22 e.g. (as used in the "new new" Android build system) instead of compileSdkVersion 22.

Python "SyntaxError: Non-ASCII character '\xe2' in file"

I my case \xe2 was a which should be replaced by '.

In general I recommend to convert UTF-8 to ASCII using e.g. https://onlineasciitools.com/convert-utf8-to-ascii

However if you want to keep UTF-8 you can use

#-*- mode: python -*-
# -*- coding: utf-8 -*-

How to solve : SQL Error: ORA-00604: error occurred at recursive SQL level 1

I noticed following line from error.

exact fetch returns more than requested number of rows

That means Oracle was expecting one row but It was getting multiple rows. And, only dual table has that characteristic, which returns only one row.

Later I recall, I have done few changes in dual table and when I executed dual table. Then found multiple rows.

So, I truncated dual table and inserted only row which X value. And, everything working fine.

Split string into individual words Java

As a more general solution (but ASCII only!), to include any other separators between words (like commas and semicolons), I suggest:

String s = "I want to walk my dog, cat, and tarantula; maybe even my tortoise.";
String[] words = s.split("\\W+");

The regex means that the delimiters will be anything that is not a word [\W], in groups of at least one [+]. Because [+] is greedy, it will take for instance ';' and ' ' together as one delimiter.

How to make <div> fill <td> height

This questions is already answered here. Just put height: 100% in both the div and the container td.