SyntaxFix

Programs & Examples On #Digital logic

Regex allow a string to only contain numbers 0 - 9 and limit length to 45

A combination of both attempts is probably what you need:

^[0-9]{1,45}$

Convert ArrayList to String array in Android

Use the method "toArray()"

ArrayList<String>  mStringList= new ArrayList<String>();
mStringList.add("ann");
mStringList.add("john");
Object[] mStringArray = mStringList.toArray();

for(int i = 0; i < mStringArray.length ; i++){
    Log.d("string is",(String)mStringArray[i]);
}

or you can do it like this: (mentioned in other answers)

ArrayList<String>  mStringList= new ArrayList<String>();
mStringList.add("ann");
mStringList.add("john");
String[] mStringArray = new String[mStringList.size()];
mStringArray = mStringList.toArray(mStringArray);

for(int i = 0; i < mStringArray.length ; i++){
    Log.d("string is",(String)mStringArray[i]);
}

http://developer.android.com/reference/java/util/ArrayList.html#toArray()

Split comma-separated input box values into array in jquery, and loop through it

 
var array = $('#searchKeywords').val().split(",");

then

$.each(array,function(i){
   alert(array[i]);
});

OR

for (i=0;i<array.length;i++){
     alert(array[i]);
}

What are static factory methods?

Java implementation contains utilities classes java.util.Arrays and java.util.Collections both of them contains static factory methods, examples of it and how to use :

Also java.lang.String class have such static factory methods:

  • String.format(...), String.valueOf(..), String.copyValueOf(...)

Update Rows in SSIS OLEDB Destination

Well, found a solution to my problem; Updating all rows using a SQL query and a SQL Task in SSIS Like Below. May help others if they face same challenge in future.

update Original 
set Original.Vaal= t.vaal 
from Original join (select * from staging1  union   select * from staging2) t 
on Original.id=t.id

Leader Not Available Kafka in Console Producer

i know this was posted long time back, i would like to share how i solved it.
since i have my office laptop ( VPN and proxy was configured ).
i checked the environment variable NO_PROXY 

> echo %NO_PROXY%

it returned with empty values
now i have set the NO_PROXY with localhost and 127.0.0.1 

> set NO_PROXY=127.0.0.1,localhost

if you want to append to existing values, then 

> set NO_PROXY=%NO_PROXY%,127.0.0.1,localhost

after this , i have restarted zookeeper and kafka
worked like a charm

Is it possible to run an .exe or .bat file on 'onclick' in HTML

It is possible when the page itself is opened via a file:/// path.

<button onclick="window.open('file:///C:/Windows/notepad.exe')">
    Launch notepad
</button>

However, the moment you put it on a webserver (even if you access it via http://localhost/), you will get an error:

Error: Access to 'file:///C:/Windows/notepad.exe' from script denied

The executable gets signed with invalid entitlements in Xcode

I faced same issue. For me solution was below steps.

  1. I went on developer account i uploaded push certificate in App Identifier.
  2. Regenerate provisioning profile

Conclusion: If there is any service enabled but it's not configured then eigther disabling or configuring that service might solve the problem

Cropping an UIImage

Follow Answer of @Arne. I Just fixing to Category function. put it in Category of UIImage.

-(UIImage*)cropImage:(CGRect)rect{

    UIGraphicsBeginImageContextWithOptions(rect.size, false, [self scale]);
    [self drawAtPoint:CGPointMake(-rect.origin.x, -rect.origin.y)];
    UIImage* cropped_image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return cropped_image;
}

Go To Definition: "Cannot navigate to the symbol under the caret."

Clean your cache symbols (Tools > Options > Debugging > Symbols > EmptySymbolCache). Open your solution in administrative mode.

this resolved my issue.

Python list iterator behavior and next(iterator)

I find the existing answers a little confusing, because they only indirectly indicate the essential mystifying thing in the code example: both* the "print i" and the "next(a)" are causing their results to be printed.

Since they're printing alternating elements of the original sequence, and it's unexpected that the "next(a)" statement is printing, it appears as if the "print i" statement is printing all the values.

In that light, it becomes more clear that assigning the result of "next(a)" to a variable inhibits the printing of its' result, so that just the alternate values that the "i" loop variable are printed. Similarly, making the "print" statement emit something more distinctive disambiguates it, as well.

(One of the existing answers refutes the others because that answer is having the example code evaluated as a block, so that the interpreter is not reporting the intermediate values for "next(a)".)

The beguiling thing in answering questions, in general, is being explicit about what is obvious once you know the answer. It can be elusive. Likewise critiquing answers once you understand them. It's interesting...

Get current URL with jQuery?

If you need the hash parameters present in the URL, window.location.href may be a better choice.

window.location.pathname
=> /search

window.location.href 
 => www.website.com/search#race_type=1

What is the best way to conditionally apply a class?

If you are using angular pre v1.1.5 (i.e. no ternary operator) and you still want an equivalent way to set a value in both conditions you can do something like this:

ng-class="{'class1':item.isReadOnly == false, 'class2':item.isReadOnly == true}"

Reference - What does this regex mean?

The Stack Overflow Regular Expressions FAQ

See also a lot of general hints and useful links at the tag details page.

Online tutorials

Quantifiers

Character Classes

Escape Sequences

Anchors

(Also see "Flavor-Specific Information ? Java ? The functions in Matcher")

Groups

Lookarounds

Modifiers

flag modifier flavors
c current position
e expression
g global most
i case-insensitive most
m multiline
m (non)multiline
o once
S study
s single line unsupported: (workaround) |
U ungreedy
u unicode most
x whitespace-extended most
y sticky ?

Other:

Common Tasks

Advanced Regex-Fu

Flavor-Specific Information

(Except for those marked with *, this section contains non-Stack Overflow links.)

General information

(Links marked with * are non-Stack Overflow links.)

Examples of regex that can cause regex engine to fail

Tools: Testers and Explainers

(This section contains non-Stack Overflow links.)

getting the reason why websockets closed with close code 1006

This may be your websocket URL you are using in device are not same(You are hitting different websocket URL from android/iphonedevice )

Convert String to Calendar Object in Java

tl;dr

The modern approach uses the java.time classes. 

YearMonth.from(
    ZonedDateTime.parse( 
        "Mon Mar 14 16:02:37 GMT 2011" , 
        DateTimeFormatter.ofPattern( "E MMM d HH:mm:ss z uuuu" )
     )
).toString()

2011-03

Avoid legacy date-time classes

The modern way is with java.time classes. The old date-time classes such as Calendar have proven to be poorly-designed, confusing, and troublesome.

Define a custom formatter to match your string input.

String input = "Mon Mar 14 16:02:37 GMT 2011";
DateTimeFormatter f = DateTimeFormatter.ofPattern( "E MMM d HH:mm:ss z uuuu" );

Parse as a ZonedDateTime.

ZonedDateTime zdt = ZonedDateTime.parse( input , f );

You are interested in the year and month. The java.time classes include YearMonth class for that purpose.

YearMonth ym = YearMonth.from( zdt );

You can interrogate for the year and month numbers if needed.

int year = ym.getYear();
int month = ym.getMonthValue();

But the toString method generates a string in standard ISO 8601 format.

String output = ym.toString();

Put this all together.

String input = "Mon Mar 14 16:02:37 GMT 2011";
DateTimeFormatter f = DateTimeFormatter.ofPattern( "E MMM d HH:mm:ss z uuuu" );
ZonedDateTime zdt = ZonedDateTime.parse( input , f );
YearMonth ym = YearMonth.from( zdt );
int year = ym.getYear();
int month = ym.getMonthValue();

Dump to console.

System.out.println( "input: " + input );
System.out.println( "zdt: " + zdt );
System.out.println( "ym: " + ym );

input: Mon Mar 14 16:02:37 GMT 2011

zdt: 2011-03-14T16:02:37Z[GMT]

ym: 2011-03

Live code

See this code running in IdeOne.com.

Conversion

If you must have a Calendar object, you can convert to a GregorianCalendar using new methods added to the old classes.

GregorianCalendar gc = GregorianCalendar.from( zdt );

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to java.time.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

  • Java SE 8 and SE 9 and later
    • Built-in.
    • Part of the standard Java API with a bundled implementation.
    • Java 9 adds some minor features and fixes.
  • Java SE 6 and SE 7
    • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
  • Android

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

How to get single value from this multi-dimensional PHP array

 
echo $myarray[0]->['email'];

Try this only if it you are passing the stdclass object

How to get the position of a character in Python?

If you want to find the first match.

Python has a in-built string method that does the work: index().

string.index(value, start, end)

Where:

  • Value: (Required) The value to search for.
  • start: (Optional) Where to start the search. Default is 0.
  • end: (Optional) Where to end the search. Default is to the end of the string.
def character_index():
    string = "Hello World! This is an example sentence with no meaning."
    match = "i"
    return string.index(match)
        
print(character_index())
> 15

If you want to find all the matches.

Let's say you need all the indexes where the character match is and not just the first one.

The pythonic way would be to use enumerate().

def character_indexes():
    string = "Hello World! This is an example sentence with no meaning."
    match = "i"

    indexes_of_match = []

    for index, character in enumerate(string):
        if character == match:
            indexes_of_match.append(index)
    return indexes_of_match

print(character_indexes())
# [15, 18, 42, 53]

Or even better with a list comprehension:

def character_indexes_comprehension():
    string = "Hello World! This is an example sentence with no meaning."
    match = "i"

    return [index for index, character in enumerate(string) if character == match]


print(character_indexes_comprehension())
# [15, 18, 42, 53]

Meaning of end='' in the statement print("\t",end='')?

See the documentation for the print function: print()

The content of end is printed after the thing you want to print. By default it contains a newline ("\n") but it can be changed to something else, like an empty string.

explode string in jquery

The split function separates each part of text with the separator you provide, and you provided "|". So the result would be an array containing "Shimla", "1" and "http://vinspro.org/travel/ind/". You could manipulate that to get the third one, "http://vinspro.org/travel/ind/", and here's an example:

var str="Shimla|1|http://vinspro.org/travel/ind/";
var n = str.split('|');
alert(n[2]);

As mentioned in other answers, this code would differ depending on if it was a string ($(str).split('|');), a textbox input ($(str).val().split('|');), or a DOM element ($(str).text().split('|');).

You could also just use plain JavaScript to get all the stuff after 9 characters, which would be "http://vinspro.org/travel/ind/". Here's an example:

var str="Shimla|1|http://vinspro.org/travel/ind/";
var n=str.substr(9);
alert(n);

Is the 'as' keyword required in Oracle to define an alias?

There is no difference between both, AS is just a more explicit way of mentioning the alias which is good because some dependent libraries depends on this small keyword. e.g. JDBC 4.0. Depend on use of it, different behaviour can be observed.

See this. I would always suggest to use the full form of semantic to avoid such issues.

MySQL: Grant **all** privileges on database

This will be helpful for some people:

From MySQL command line:

CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'password';

Sadly, at this point newuser has no permissions to do anything with the databases. In fact, if newuser even tries to login (with the password, password), they will not be able to reach the MySQL shell.

Therefore, the first thing to do is to provide the user with access to the information they will need.

GRANT ALL PRIVILEGES ON * . * TO 'newuser'@'localhost';

The asterisks in this command refer to the database and table (respectively) that they can access—this specific command allows to the user to read, edit, execute and perform all tasks across all the databases and tables.

Once you have finalized the permissions that you want to set up for your new users, always be sure to reload all the privileges.

FLUSH PRIVILEGES;

Your changes will now be in effect.

For more information: http://dev.mysql.com/doc/refman/5.6/en/grant.html

If you are not comfortable with the command line then you can use a client like MySQL workbench, Navicat or SQLyog

How to create empty folder in java?

Looks file you use the .mkdirs() method on a File object: http://www.roseindia.net/java/beginners/java-create-directory.shtml

// Create a directory; all non-existent ancestor directories are
// automatically created
success = (new File("../potentially/long/pathname/without/all/dirs")).mkdirs();
if (!success) {
    // Directory creation failed
}

Android MediaPlayer Stop and Play

According to the MediaPlayer life cycle, which you can view in the Android API guide, I think that you have to call reset() instead of stop(), and after that prepare again the media player (use only one) to play the sound from the beginning. Take also into account that the sound may have finished. So I would also recommend to implement setOnCompletionListener() to make sure that if you try to play again the sound it doesn't fail.

How to disable a input in angular2

I think I figured out the problem, this input field is part of a reactive form (?), since you have included formControlName. This means that what you are trying to do by disabling the input field with is_edit is not working, e.g your attempt [disabled]="is_edit", which would in other cases work. With your form you need to do something like this:

toggle() {
  let control = this.myForm.get('name')
  control.disabled ? control.enable() : control.disable();
}

and lose the is_edit altogether.

if you want the input field to be disabled as default, you need to set the form control as: 

name: [{value: '', disabled:true}]

Here's a plunker

Send mail via CMD console

Unless you want to talk to an SMTP server directly via telnet you'd use commandline mailers like blat:

blat -to [email protected] -f [email protected] -s "mail subject" ^
  -server smtp.example.net -body "message text"

or bmail:

bmail -s smtp.example.net -t [email protected] -f [email protected] -h ^
  -a "mail subject" -b "message text"

You could also write your own mailer in VBScript or PowerShell.

OpenCV get pixel channel value from Mat image

The pixels array is stored in the "data" attribute of cv::Mat. Let's suppose that we have a Mat matrix where each pixel has 3 bytes (CV_8UC3).

For this example, let's draw a RED pixel at position 100x50.

Mat foo;
int x=100, y=50;

Solution 1:

Create a macro function that obtains the pixel from the array.

#define PIXEL(frame, W, x, y) (frame+(y)*3*(W)+(x)*3)
//...
unsigned char * p = PIXEL(foo.data, foo.rols, x, y);
p[0] = 0;   // B
p[1] = 0;   // G
p[2] = 255; // R

Solution 2:

Get's the pixel using the method ptr.

unsigned char * p = foo.ptr(y, x); // Y first, X after
p[0] = 0;   // B
p[1] = 0;   // G
p[2] = 255; // R

How to add a Hint in spinner in XML

You can set the spinner prompt:

spinner.setPrompt("Select gender...");

How to handle iframe in Selenium WebDriver using java

Selenium Web Driver Handling Frames
It is impossible to click iframe directly through XPath since it is an iframe. First we have to switch to the frame and then we can click using xpath.

driver.switchTo().frame() has multiple overloads.

  1. driver.switchTo().frame(name_or_id)
    Here your iframe doesn't have id or name, so not for you.

  2. driver.switchTo().frame(index)
    This is the last option to choose, because using index is not stable enough as you could imagine. If this is your only iframe in the page, try driver.switchTo().frame(0)

  3. driver.switchTo().frame(iframe_element)
    The most common one. You locate your iframe like other elements, then pass it into the method.

driver.switchTo().defaultContent(); [parentFrame, defaultContent, frame]

// Based on index position:
int frameIndex = 0;
List<WebElement> listFrames = driver.findElements(By.tagName("iframe"));
System.out.println("list frames   "+listFrames.size());
driver.switchTo().frame(listFrames.get( frameIndex ));

// XPath|CssPath Element:
WebElement frameCSSPath = driver.findElement(By.cssSelector("iframe[title='Fill Quote']"));
WebElement frameXPath = driver.findElement(By.xpath(".//iframe[1]"));
WebElement frameTag = driver.findElement(By.tagName("iframe"));

driver.switchTo().frame( frameCSSPath ); // frameXPath, frameTag


driver.switchTo().frame("relative=up"); // focus to parent frame.
driver.switchTo().defaultContent(); // move to the most parent or main frame

// For alert's
Alert alert = driver.switchTo().alert(); // Switch to alert pop-up
alert.accept();
alert.dismiss();

XML Test:

<html>
    <IFame id='1'>...       parentFrame() « context remains unchanged. <IFame1>
    |
     -> <IFrame id='2'>...  parentFrame() « Change focus to the parent context. <IFame1>
</html>

</html>
<frameset cols="50%,50%">
    <Fame id='11'>...     defaultContent() « driver focus to top window/first frame. <html>
    |
     -> <Frame id='22'>... defaultContent() « driver focus to top window/first frame. <Fame11> 
                           frame("relative=up") « focus to parent frame. <Fame11>
</frameset>
</html>

Conversion of RC to Web-Driver Java commands. link.

<frame> is an HTML element which defines a particular area in which another HTML document can be displayed. A frame should be used within a <frameset>. « Deprecated. Not for use in new websites.

Run a command shell in jenkins

As far as I know, Windows will not support shell scripts out of the box. You can install Cygwin or Git for Windows, go to Manage Jenkins > Configure System Shell and point it to the location of sh.exe file found in their installation. For example:

C:\Program Files\Git\bin\sh.exe

There is another option I've discovered. This one is better because it allowed me to use shell in pipeline scripts with simple sh "something".

Add the folder to system PATH. Right click on Computer, click properties > advanced system settings > environmental variables, add C:\Program Files\Git\bin\ to your system Path property.

IMPORTANT note: for some reason I had to add it to the system wide Path, adding to user Path didn't work, even though Jenkins was running on this user.

An important note (thanks bugfixr!):

This works. It should be noted that you will need to restart Jenkins in order for it to pick up the new PATH variable. I just went to my services and restated it from there.

Disclaimer: the names may differ slightly as I'm not using English Windows.

How to set dialog to show in full screen?

EDIT Until such time as StackOverflow allows us to version our answers, this is an answer that works for Android 3 and below. Please don't downvote it because it's not working for you now, because it definitely works with older Android versions.

You should only need to add one line to your onCreateDialog() method:

@Override
protected Dialog onCreateDialog(int id) {
    //all other dialog stuff (which dialog to display)

    //this line is what you need:
    dialog.getWindow().setFlags(LayoutParams.FLAG_FULLSCREEN, LayoutParams.FLAG_FULLSCREEN);

    return dialog;
}

Jquery check if element is visible in viewport

Check if element is visible in viewport using jquery:

First determine the top and bottom positions of the element. Then determine the position of the viewport's bottom (relative to the top of your page) by adding the scroll position to the viewport height.

If the bottom position of the viewport is greater than the element's top position AND the top position of the viewport is less than the element's bottom position, the element is in the viewport (at least partially). In simpler terms, when any part of the element is between the top and bottom bounds of your viewport, the element is visible on your screen.

Now you can write an if/else statement, where the if statement only runs when the above condition is met.

The code below executes what was explained above:

// this function runs every time you are scrolling

$(window).scroll(function() {
    var top_of_element = $("#element").offset().top;
    var bottom_of_element = $("#element").offset().top + $("#element").outerHeight();
    var bottom_of_screen = $(window).scrollTop() + $(window).innerHeight();
    var top_of_screen = $(window).scrollTop();

    if ((bottom_of_screen > top_of_element) && (top_of_screen < bottom_of_element)){
        // the element is visible, do something
    } else {
        // the element is not visible, do something else
    }
});

This answer is a summary of what Chris Bier and Andy were discussing below. I hope it helps anyone else who comes across this question while doing research like I did. I also used an answer to the following question to formulate my answer: Show Div when scroll position.

How to do 3 table JOIN in UPDATE query?

For PostgreSQL example:

UPDATE TableA AS a
SET param_from_table_a=FALSE -- param FROM TableA
FROM TableB AS b
WHERE b.id=a.param_id AND a.amount <> 0;

check output from CalledProcessError

According to the Python os module documentation os.popen has been deprecated since Python 2.6.

I think the solution for modern Python is to use check_output() from the subprocess module.

From the subprocess Python documentation:

subprocess.check_output(args, *, stdin=None, stderr=None, shell=False, universal_newlines=False) Run command with arguments and return its output as a byte string.

If the return code was non-zero it raises a CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute and any output in the output attribute.

If you run through the following code in Python 2.7 (or later):

import subprocess

try:
    print subprocess.check_output(["ping", "-n", "2", "-w", "2", "1.1.1.1"])
except subprocess.CalledProcessError, e:
    print "Ping stdout output:\n", e.output

You should see an output that looks something like this:

Ping stdout output:

Pinging 1.1.1.1 with 32 bytes of data:
Request timed out.
Request timed out.

Ping statistics for 1.1.1.1:
Packets: Sent = 2, Received = 0, Lost = 2 (100% loss),

The e.output string can be parsed to suit the OPs needs.

If you want the returncode or other attributes, they are in CalledProccessError as can be seen by stepping through with pdb

(Pdb)!dir(e)   

['__class__', '__delattr__', '__dict__', '__doc__', '__format__',
 '__getattribute__', '__getitem__', '__getslice__', '__hash__', '__init__',
 '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
 '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', 
 '__unicode__', '__weakref__', 'args', 'cmd', 'message', 'output', 'returncode']

How to pass the button value into my onclick event function?

You can pass the value to the function using this.value, where this points to the button

<input type="button" value="mybutton1" onclick="dosomething(this.value)">

And then access that value in the function 

function dosomething(val){
  console.log(val);
}

SQL ORDER BY date problem

Unsure what dbms you're using however I'd do it this way in Microsoft SQL:

select      [date]
from        tbemp 
order by    cast([date] as datetime) asc

Java program to find the largest & smallest number in n numbers without using arrays

 
import java.util.Scanner;

public class LargestSmallestNumbers {

    private static Scanner input;

    public static void main(String[] args) {
       int count,items;
       int newnum =0 ;
       int highest=0;
       int lowest =0;

       input = new Scanner(System.in);
       System.out.println("How many numbers you want to enter?");
       items = input.nextInt();

       System.out.println("Enter "+items+" numbers: ");


       for (count=0; count<items; count++){
           newnum = input.nextInt();               
           if (highest<newnum)
               highest=newnum;

           if (lowest==0)
               lowest=newnum;

           else if (newnum<=lowest)
               lowest=newnum;
           }

       System.out.println("The highest number is "+highest);
       System.out.println("The lowest number is "+lowest);
    }
}

How to build a 'release' APK in Android Studio?

Click \Build\Select Build Variant... in Android Studio. And choose release.

How do I get the logfile from an Android device?

First make sure adb command is executable by setting PATH to android sdk platform-tools:

export PATH=/Users/espireinfolabs/Desktop/soft/android-sdk-mac_x86/platform-tools:$PATH

then run:

adb shell logcat > log.txt

OR first move to adb platform-tools:

cd /Users/user/Android/Tools/android-sdk-macosx/platform-tools

then run

./adb shell logcat > log.txt

How to do ToString for a possibly null object?

I disagree with that this:

String s = myObj == null ? "" : myObj.ToString();

is a hack in any way. I think it's a good example of clear code. It's absolutely obvious what you want to achieve and that you're expecting null.

UPDATE:

I see now that you were not saying that this was a hack. But it's implied in the question that you think this way is not the way to go. In my mind it's definitely the clearest solution.

Responsively change div size keeping aspect ratio

Bumming off Chris's idea, another option is to use pseudo elements so you don't need to use an absolutely positioned internal element.

<style>
.square {
    /* width within the parent.
       can be any percentage. */
    width: 100%;
}
.square:before {
    content: "";
    float: left;

    /* essentially the aspect ratio. 100% means the
       div will remain 100% as tall as it is wide, or
       square in other words.  */
    padding-bottom: 100%;
}
/* this is a clearfix. you can use whatever
   clearfix you usually use, add
   overflow:hidden to the parent element,
   or simply float the parent container. */
.square:after {
    content: "";
    display: table;
    clear: both;
}
</style>
<div class="square">
  <h1>Square</h1>
  <p>This div will maintain its aspect ratio.</p>
</div>

I've put together a demo here: http://codepen.io/tcmulder/pen/iqnDr

EDIT:

Now, bumming off of Isaac's idea, it's easier in modern browsers to simply use vw units to force aspect ratio (although I wouldn't also use vh as he does or the aspect ratio will change based on window height).

So, this simplifies things:

<style>
.square {
    /* width within the parent (could use vw instead of course) */
    width: 50%;
    /* set aspect ratio */
    height: 50vw;
}
</style>
<div class="square">
  <h1>Square</h1>
  <p>This div will maintain its aspect ratio.</p>
</div>

I've put together a modified demo here: https://codepen.io/tcmulder/pen/MdojRG?editors=1100

You could also set max-height, max-width, and/or min-height, min-width if you don't want it to grow ridiculously big or small, since it's based on the browser's width now and not the container and will grow/shrink indefinitely.

Note you can also scale the content inside the element if you set the font size to a vw measurement and all the innards to em measurements, and here's a demo for that: https://codepen.io/tcmulder/pen/VBJqLV?editors=1100

how to create virtual host on XAMPP

Write these codes end of the C:\xampp\apache\conf\extra\httpd-vhosts.conf file,

DocumentRoot "D:/xampp/htdocs/foldername"
ServerName www.siteurl.com
ServerAlias www.siteurl.com
ErrorLog "logs/dummy-host.example.com-error.log"
CustomLog "logs/dummy-host.example.com-access.log" common

between the virtual host tag.

and edit the file System32/Drivers/etc/hosts use notepad as administrator

add bottom of the file

127.0.0.1    www.siteurl.com

Why "net use * /delete" does not work but waits for confirmation in my PowerShell script?

With PowerShell 5.1 in Windows 10 you can use:

Get-SmbMapping | Remove-SmbMapping -Confirm:$false

How to calculate time difference in java?

Just like any other language; convert your time periods to a unix timestamp (ie, seconds since the Unix epoch) and then simply subtract. Then, the resulting seconds should be used as a new unix timestamp and read formatted in whatever format you want.

Ah, give the above poster (genesiss) his due credit, code's always handy ;) Though, you now have an explanation as well :)

Getting "Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?" when installing lxml through pip

I tried install a lib that depends lxml and nothing works. I see a message when build was started: "Building without Cython", so after install cython with apt-get install cython, lxml was installed.

How to skip "are you sure Y/N" when deleting files in batch files

You have the following options on Windows command line:

net use [DeviceName [/home[{Password | *}] [/delete:{yes | no}]]

Try like:

net use H: /delete /y

How to find a parent with a known class in jQuery?

You can use parents() to get all parents with the given selector.

Description: Get the ancestors of each element in the current set of matched elements, optionally filtered by a selector.

But parent() will get just the first parent of the element.

Description: Get the parent of each element in the current set of matched elements, optionally filtered by a selector.

jQuery parent() vs. parents()

And there is .parentsUntil() which I think will be the best.

Description: Get the ancestors of each element in the current set of matched elements, up to but not including the element matched by the selector.

How do I declare and initialize an array in Java?

There are various ways in which you can declare an array in Java:

float floatArray[]; // Initialize later
int[] integerArray = new int[10];
String[] array = new String[] {"a", "b"};

You can find more information in the Sun tutorial site and the JavaDoc.

How to create a batch file to run cmd as administrator

Make a text using notepad or any text editor of you choice. Open notepad, write this short command "cmd.exe" without the quote aand save it as cmd.bat.

Click cmd.bat and choose "run as administrator".

NumPy array is not JSON serializable

Use the json.dumps default kwarg:

default should be a function that gets called for objects that can’t otherwise be serialized. ... or raise a TypeError

In the default function check if the object is from the module numpy, if so either use ndarray.tolist for a ndarray or use .item for any other numpy specific type.

import numpy as np

def default(obj):
    if type(obj).__module__ == np.__name__:
        if isinstance(obj, np.ndarray):
            return obj.tolist()
        else:
            return obj.item()
    raise TypeError('Unknown type:', type(obj))

dumped = json.dumps(data, default=default)

Check if returned value is not null and if so assign it, in one line, with one method call

If you're not on java 1.8 yet and you don't mind to use commons-lang you can use org.apache.commons.lang3.ObjectUtils#defaultIfNull

Your code would be:

dinner = ObjectUtils.defaultIfNull(cage.getChicken(),getFreeRangeChicken())

How do I dynamically set HTML5 data- attributes using react?

You should not wrap JavaScript expressions in quotes.

<option data-img-src={this.props.imageUrl} value="1">{this.props.title}</option>

Take a look at the JavaScript Expressions docs for more info.

How to get the path of a running JAR file?

If you are really looking for a simple way to get the folder in which your JAR is located you should implement this format of the solution It is easier than what are you are going to find (it is hard to find and many solutions are no longer supported, many others provide the path of the file instead of the actual directory) and this is proven working on version 1.12.

new File(".").getCanonicalPath()

Gathering the Input from other answers this is a simple one too:

String localPath=new File(getClass().getProtectionDomain().getCodeSource().getLocation().toURI()).getParentFile().getPath()+"\\";

Both will return a String with this format:

"C:\Users\User\Desktop\Folder\"

In a simple and concise line.

In Android, how do I set margins in dp programmatically?

Created a Kotlin Extension function for those of you who might find it handy.

Make sure to pass in pixels not dp. Happy coding :)

fun View.addLayoutMargins(left: Int? = null, top: Int? = null,
                      right: Int? = null, bottom: Int? = null) {
    this.layoutParams = ViewGroup.MarginLayoutParams(this.layoutParams)
            .apply {
                left?.let { leftMargin = it }
                top?.let { topMargin = it }
                right?.let { rightMargin = it }
                bottom?.let { bottomMargin = it }
            }
}

How to effectively work with multiple files in Vim

Many answers here! What I use without reinventing the wheel - the most famous plugins (that are not going to die any time soon and are used by many people) to be ultra fast and geeky.

  • ctrlpvim/ctrlp.vim - to find file by name fuzzy search by its location or just its name
  • jlanzarotta/bufexplorer - to browse opened buffers (when you do not remember how many files you opened and modified recently and you do not remember where they are, probably because you searched for them with Ag)
  • rking/ag.vim to search the files with respect to gitignore
  • scrooloose/nerdtree to see the directory structure, lookaround, add/delete/modify files

EDIT: Recently I have been using dyng/ctrlsf.vim to search with contextual view (like Sublime search) and I switched the engine from ag to ripgrep. The performance is outstanding.

EDIT2: Along with CtrlSF you can use mg979/vim-visual-multi, make changes to multiple files at once and then at the end save them in one go.

Declaring a custom android UI element using XML

It seems that Google has updated its developer page and added various trainings there.

One of them deals with the creation of custom views and can be found here

MySQL: When is Flush Privileges in MySQL really needed?

Privileges assigned through GRANT option do not need FLUSH PRIVILEGES to take effect - MySQL server will notice these changes and reload the grant tables immediately.

From MySQL documentation:

If you modify the grant tables directly using statements such as INSERT, UPDATE, or DELETE, your changes have no effect on privilege checking until you either restart the server or tell it to reload the tables. If you change the grant tables directly but forget to reload them, your changes have no effect until you restart the server. This may leave you wondering why your changes seem to make no difference!

To tell the server to reload the grant tables, perform a flush-privileges operation. This can be done by issuing a FLUSH PRIVILEGES statement or by executing a mysqladmin flush-privileges or mysqladmin reload command.

If you modify the grant tables indirectly using account-management statements such as GRANT, REVOKE, SET PASSWORD, or RENAME USER, the server notices these changes and loads the grant tables into memory again immediately.

How to create named and latest tag in Docker?

ID=$(docker build -t creack/node .) doesn't work for me since ID will contain the output from the build.

SO I'm using this small BASH script:

#!/bin/bash

set -o pipefail

IMAGE=...your image name...
VERSION=...the version...

docker build -t ${IMAGE}:${VERSION} . | tee build.log || exit 1
ID=$(tail -1 build.log | awk '{print $3;}')
docker tag $ID ${IMAGE}:latest

docker images | grep ${IMAGE}

docker run --rm ${IMAGE}:latest /opt/java7/bin/java -version

Google Play Services Library update and missing symbol @integer/google_play_services_version

To anyone using gradle: don't include the project source, but instead download it using SDK Manager and add this line to dependencies:

compile 'com.google.android.gms:play-services:4.0.30'

What encoding/code page is cmd.exe using?

Type

chcp

to see your current code page (as Dewfy already said).

Use

nlsinfo

to see all installed code pages and find out what your code page number means.

You need to have Windows Server 2003 Resource kit installed (works on Windows XP) to use nlsinfo.

How to get public directory?

I know this is a little late, but if someone else comes across this looking, you can now use public_path(); in Laravel 4, it has been added to the helper.php file in the support folder see here.

Remove duplicates from an array of objects in JavaScript

If you are using Lodash library you can use the below function as well. It should remove duplicate objects.

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
_.uniqWith(objects, _.isEqual);

no operator "<<" matches these operands

If you want to use std::string reliably, you must #include <string>.

How do you Change a Package's Log Level using Log4j?

Which app server are you using? Each one puts its logging config in a different place, though most nowadays use Commons-Logging as a wrapper around either Log4J or java.util.logging.

Using Tomcat as an example, this document explains your options for configuring logging using either option. In either case you need to find or create a config file that defines the log level for each package and each place the logging system will output log info (typically console, file, or db).

In the case of log4j this would be the log4j.properties file, and if you follow the directions in the link above your file will start out looking like:

log4j.rootLogger=DEBUG, R 
log4j.appender.R=org.apache.log4j.RollingFileAppender 
log4j.appender.R.File=${catalina.home}/logs/tomcat.log 
log4j.appender.R.MaxFileSize=10MB 
log4j.appender.R.MaxBackupIndex=10 
log4j.appender.R.layout=org.apache.log4j.PatternLayout 
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n

Simplest would be to change the line:

log4j.rootLogger=DEBUG, R

To something like:

log4j.rootLogger=WARN, R

But if you still want your own DEBUG level output from your own classes add a line that says:

log4j.category.com.mypackage=DEBUG

Reading up a bit on Log4J and Commons-Logging will help you understand all this.

Downloading video from YouTube

Gonna give another answer, since the libraries mentioned haven't been actively developed anymore.

Consider using YoutubeExplode. It has a very rich and consistent API and allows you to do a lot of other things with youtube videos beside downloading them.

ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: 'undefined'

*NgIf can create problem here , so either use display none css or easier way is to Use [hidden]="!condition"

Android Studio: Application Installation Failed

This happens when your app is using any library and there is also an app installed in your device that is using the same library. Go to gradle and type:

android{
defaultConfig.applicationId="your package"
}

this will resolve your problem.

clear table jquery

Having a table like this (with a header and a body)

<table id="myTableId">
    <thead>
    </thead>
    <tbody>
   </tbody>
</table>

remove every tr having a parent called tbody inside the #tableId

$('#tableId tbody > tr').remove();

and in reverse if you want to add to your table

$('#tableId tbody').append("<tr><td></td>....</tr>");

Javascript Append Child AFTER Element

after is now a JavaScript method

MDN Documentation

Quoting MDN

The ChildNode.after() method inserts a set of Node or DOMString objects in the children list of this ChildNode's parent, just after this ChildNode. DOMString objects are inserted as equivalent Text nodes.

The browser support is Chrome(54+), Firefox(49+) and Opera(39+). It doesn't support IE and Edge.

Snippet

_x000D_
_x000D_ 
var elm=document.getElementById('div1');
var elm1 = document.createElement('p');
var elm2 = elm1.cloneNode();
elm.append(elm1,elm2);

//added 2 paragraphs
elm1.after("This is sample text");
//added a text content
elm1.after(document.createElement("span"));
//added an element
console.log(elm.innerHTML);
_x000D_ 
<div id="div1"></div>
_x000D_
_x000D_
_x000D_

In the snippet, I used another term append too

Chrome - ERR_CACHE_MISS

This is an issue distinct to Chrome, but there are two paths you can take to fix it.

I noticed the error once I added this specific header to my PHP script.

header('Content-Type: application/json');

The error appears to be related to PHP sessions when sending response headers. So according to chromium bug report 424599, this was fixed and you can just update to a newer version of Chrome. But if for some reason you can't or don't want to update, the workaround would be to remove these response headers from your PHP script if possible (that's what I did because it wasn't required).

Executing a stored procedure within a stored procedure

Here is an example of one of our stored procedures that executes multiple stored procedures within it:

ALTER PROCEDURE [dbo].[AssetLibrary_AssetDelete]
(
    @AssetID AS uniqueidentifier
)
AS

SET NOCOUNT ON

SET TRANSACTION ISOLATION LEVEL READ COMMITTED

EXEC AssetLibrary_AssetDeleteAttributes @AssetID
EXEC AssetLibrary_AssetDeleteComponents @AssetID
EXEC AssetLibrary_AssetDeleteAgreements @AssetID
EXEC AssetLibrary_AssetDeleteMaintenance @AssetID

DELETE FROM
    AssetLibrary_Asset
WHERE
    AssetLibrary_Asset.AssetID = @AssetID

RETURN (@@ERROR)

How to remove certain characters from a string in C++?

remove_if() has already been mentioned. But, with C++0x, you can specify the predicate for it with a lambda instead.

Below is an example of that with 3 different ways of doing the filtering. "copy" versions of the functions are included too for cases when you're working with a const or don't want to modify the original.

#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>
using namespace std;

string& remove_chars(string& s, const string& chars) {
    s.erase(remove_if(s.begin(), s.end(), [&chars](const char& c) {
        return chars.find(c) != string::npos;
    }), s.end());
    return s;
}
string remove_chars_copy(string s, const string& chars) {
    return remove_chars(s, chars);
}

string& remove_nondigit(string& s) {
    s.erase(remove_if(s.begin(), s.end(), [](const char& c) {
        return !isdigit(c);
    }), s.end());
    return s;
}
string remove_nondigit_copy(string s) {
    return remove_nondigit(s);
}

string& remove_chars_if_not(string& s, const string& allowed) {
    s.erase(remove_if(s.begin(), s.end(), [&allowed](const char& c) {
        return allowed.find(c) == string::npos;
    }), s.end());
    return s;
}
string remove_chars_if_not_copy(string s, const string& allowed) {
    return remove_chars_if_not(s, allowed);
}

int main() {
    const string test1("(555) 555-5555");
    string test2(test1);
    string test3(test1);
    string test4(test1);
    cout << remove_chars_copy(test1, "()- ") << endl;
    cout << remove_chars(test2, "()- ") << endl;
    cout << remove_nondigit_copy(test1) << endl;
    cout << remove_nondigit(test3) << endl;
    cout << remove_chars_if_not_copy(test1, "0123456789") << endl;
    cout << remove_chars_if_not(test4, "0123456789") << endl;
}

Python: Remove division decimal

 
>>> int(2.0)

You will get the answer as 2

pretty-print JSON using JavaScript

Here is how you can print without using native function.

function pretty(ob, lvl = 0) {

  let temp = [];

  if(typeof ob === "object"){
    for(let x in ob) {
      if(ob.hasOwnProperty(x)) {
        temp.push( getTabs(lvl+1) + x + ":" + pretty(ob[x], lvl+1) );
      }
    }
    return "{\n"+ temp.join(",\n") +"\n" + getTabs(lvl) + "}";
  }
  else {
    return ob;
  }

}

function getTabs(n) {
  let c = 0, res = "";
  while(c++ < n)
    res+="\t";
  return res;
}

let obj = {a: {b: 2}, x: {y: 3}};
console.log(pretty(obj));

/*
  {
    a: {
      b: 2
    },
    x: {
      y: 3
    }
  }
*/

How to use support FileProvider for sharing content to other apps?

If you get an image from camera none of these solutions work for Android 4.4. In this case it's better to check versions.

Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
if (intent.resolveActivity(getContext().getPackageManager()) != null) {
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
        uri = Uri.fromFile(file);
    } else {
        uri = FileProvider.getUriForFile(getContext(), getContext().getPackageName() + ".provider", file);
    }
    intent.putExtra(MediaStore.EXTRA_OUTPUT, uri);
    startActivityForResult(intent, CAMERA_REQUEST);
}

Failed to run sdkmanager --list with Java 9

As some people have mentioned before, this very well could be a simpler problem having to do with one java installation taking precedence over the other.

In my case it was java 8 being overshadowed by a default newer java.

I installed java 8:

sudo apt-get install openjdk-8-jdk

Then I updated the installed java to be the new default:

sudo update-alternatives --config java

Whereby I selected java 8's id number.

After doing these (pretty simple) steps, I could just run sdkmanager without error.

Hope this helps someone!

Identifier is undefined

From the update 2 and after narrowing down the problem scope, we can easily find that there is a brace missing at the end of the function addWord. The compiler will never explicitly identify such a syntax error. instead, it will assume that the missing function definition located in some other object file. The linker will complain about it and hence directly will be categorized under one of the broad the error phrases which is identifier is undefined. Reasonably, because with the current syntax the next function definition (in this case is ac_search) will be included under the addWord scope. Hence, it is not a global function anymore. And that is why compiler will not see this function outside addWord and will throw this error message stating that there is no such a function. A very good elaboration about the compiler and the linker can be found in this article

Validate IPv4 address in Java

Pretty simple with Regular Expression (but note this is much less efficient and much harder to read than worpet's answer that uses an Apache Commons Utility)

private static final Pattern PATTERN = Pattern.compile(
        "^(([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.){3}([01]?\\d\\d?|2[0-4]\\d|25[0-5])$");

public static boolean validate(final String ip) {
    return PATTERN.matcher(ip).matches();
}

Based on post Mkyong

Android Volley - BasicNetwork.performRequest: Unexpected response code 400

Just to update all, after some deliberations, I have decided to use Async Http Client instead to solve my earlier problem. The library allows a cleaner approach (to me) to manipulate HTTP responses especially in cases where JSON objects are returned in all scenarios/HTTP statuses.

protected void getLogin() {

    EditText username = (EditText) findViewById(R.id.username); 
    EditText password = (EditText) findViewById(R.id.password); 

    RequestParams params = new RequestParams();
    params.put("username", username.getText().toString());
    params.put("password", password.getText().toString());

    RestClient.post(getHost() + "api/v1/auth/login", params,
            new JsonHttpResponseHandler() {

        @Override
        public void onSuccess(int statusCode, Header[] headers,
                JSONObject response) {

            try {

                //process JSONObject obj 
                Log.w("myapp","success status code..." + statusCode);

            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        @Override
        public void onFailure(int statusCode, Header[] headers,
                Throwable throwable, JSONObject errorResponse) {
            Log.w("myapp", "failure status code..." + statusCode);


            try {
                //process JSONObject obj
                Log.w("myapp", "error ..."  + errorResponse.getString("message").toString());
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    });
}

Java abstract interface

Well 'Abstract Interface' is a Lexical construct: http://en.wikipedia.org/wiki/Lexical_analysis.

It is required by the compiler, you could also write interface.

Well don't get too much into Lexical construct of the language as they might have put it there to resolve some compilation ambiguity which is termed as special cases during compiling process or for some backward compatibility, try to focus on core Lexical construct.

The essence of `interface is to capture some abstract concept (idea/thought/higher order thinking etc) whose implementation may vary ... that is, there may be multiple implementation.

An Interface is a pure abstract data type that represents the features of the Object it is capturing or representing.

Features can be represented by space or by time. When they are represented by space (memory storage) it means that your concrete class will implement a field and method/methods that will operate on that field or by time which means that the task of implementing the feature is purely computational (requires more cpu clocks for processing) so you have a trade off between space and time for feature implementation.

If your concrete class does not implement all features it again becomes abstract because you have a implementation of your thought or idea or abstractness but it is not complete , you specify it by abstract class.

A concrete class will be a class/set of classes which will fully capture the abstractness you are trying to capture class XYZ.

So the Pattern is 

Interface--->Abstract class/Abstract classes(depends)-->Concrete class

How can I convert byte size into a human-readable format in Java?

Use an Android built-in class

For Android, there is a class, Formatter. Just one line of code and you are done.

android.text.format.Formatter.formatShortFileSize(activityContext, bytes);

It is like formatFileSize(), but trying to generate shorter numbers (showing fewer decimals).

android.text.format.Formatter.formatFileSize(activityContext, bytes);

It formats a content size to be in the form of bytes, kilobytes, megabytes, etc.

PHP Parse error: syntax error, unexpected '?' in helpers.php 233

If I had to guess, I'd say you installed the PPA 7.1.8 as CLI only (php7-cli). You're getting your version info from that, but your libapache2-mod-php package is still 14.04 main which is 5.6. Check your phpinfo in your browser to confirm the version. You might also consider migrating to Ubuntu 16.04 to get PHP 7.0 in main.

Sequence contains no matching element

Well, I'd expect it's this line that's throwing the exception:

var documentRow = _dsACL.Documents.First(o => o.ID == id)

First() will throw an exception if it can't find any matching elements. Given that you're testing for null immediately afterwards, it sounds like you want FirstOrDefault(), which returns the default value for the element type (which is null for reference types) if no matching items are found:

var documentRow = _dsACL.Documents.FirstOrDefault(o => o.ID == id)

Other options to consider in some situations are Single() (when you believe there's exactly one matching element) and SingleOrDefault() (when you believe there's exactly one or zero matching elements). I suspect that FirstOrDefault is the best option in this particular case, but it's worth knowing about the others anyway.

On the other hand, it looks like you might actually be better off with a join here in the first place. If you didn't care that it would do all matches (rather than just the first) you could use:

var query = from target in _lstAcl.Documents
            join source in _dsAcl.Document
            where source.ID.ToString() equals target.ID
            select new { source, target };
foreach (var pair in query)
{
    target.Read = source.Read;
    target.ReadRule = source.ReadRule;
    // etc
}

That's simpler and more efficient IMO.

Even if you do decide to keep the loop, I have a couple of suggestions:

  • Get rid of the outer if. You don't need it, as if Count is zero the for loop body will never execute

  • Use exclusive upper bounds in for loops - they're more idiomatic in C#:

    for (i = 0; i < _lstAcl.Documents.Count; i++)

  • Eliminate common subexpressions:

    var target = _lstAcl.Documents[i];
// Now use target for the rest of the loop body

  • Where possible use foreach instead of for to start with:

    foreach (var target in _lstAcl.Documents)

How can I remove specific rules from iptables?

The best solution that works for me without any problems looks this way:
1. Add temporary rule with some comment:

comment=$(cat /proc/sys/kernel/random/uuid | sed 's/\-//g')
iptables -A ..... -m comment --comment "${comment}" -j REQUIRED_ACTION

2. When the rule added and you wish to remove it (or everything with this comment), do:

iptables-save | grep -v "${comment}" | iptables-restore

So, you'll 100% delete all rules that match the $comment and leave other lines untouched. This solution works for last 2 months with about 100 changes of rules per day - no issues.Hope, it helps

Rename multiple files in a directory in Python

This sort of stuff is perfectly fitted for IPython, which has shell integration.

In [1] files = !ls
In [2] for f in files:
           newname = process_filename(f)
           mv $f $newname

Note: to store this in a script, use the .ipy extension, and prefix all shell commands with !.

See also: http://ipython.org/ipython-doc/stable/interactive/shell.html

How to make a query with group_concat in sql server

 
Select
      A.maskid
    , A.maskname
    , A.schoolid
    , B.schoolname
    , STUFF((
          SELECT ',' + T.maskdetail
          FROM dbo.maskdetails T
          WHERE A.maskid = T.maskid
          FOR XML PATH('')), 1, 1, '') as maskdetail 
FROM dbo.tblmask A
JOIN dbo.school B ON B.ID = A.schoolid
Group by  A.maskid
    , A.maskname
    , A.schoolid
    , B.schoolname

Vertical align in bootstrap table

SCSS

.table-vcenter {
    td,
    th {
        vertical-align: middle;
    }
}

use

<table class="table table-vcenter">
</table>

Convert NSDate to NSString

swift 4 answer

static let dateformat: String = "yyyy-MM-dd'T'HH:mm:ss"
public static func stringTodate(strDate : String) -> Date
{

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = dateformat
    let date = dateFormatter.date(from: strDate)
    return date!
}
public static func dateToString(inputdate : Date) -> String
{

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = dateformat
    return formatter.string(from: inputdate)

}

What is the difference between buffer and cache memory in Linux?

I think this page will help understanding the difference between buffer and cache deeply. http://www.tldp.org/LDP/sag/html/buffer-cache.html

Reading from a disk is very slow compared to accessing (real) memory. In addition, it is common to read the same part of a disk several times during relatively short periods of time. For example, one might first read an e-mail message, then read the letter into an editor when replying to it, then make the mail program read it again when copying it to a folder. Or, consider how often the command ls might be run on a system with many users. By reading the information from disk only once and then keeping it in memory until no longer needed, one can speed up all but the first read. This is called disk buffering, and the memory used for the purpose is called the buffer cache.

Since memory is, unfortunately, a finite, nay, scarce resource, the buffer cache usually cannot be big enough (it can't hold all the data one ever wants to use). When the cache fills up, the data that has been unused for the longest time is discarded and the memory thus freed is used for the new data.

Disk buffering works for writes as well. On the one hand, data that is written is often soon read again (e.g., a source code file is saved to a file, then read by the compiler), so putting data that is written in the cache is a good idea. On the other hand, by only putting the data into the cache, not writing it to disk at once, the program that writes runs quicker. The writes can then be done in the background, without slowing down the other programs.

How to utilize date add function in Google spreadsheet?

You can just add the number to the cell with the date.

so if A1: 12/3/2012 and A2: =A1+7 then A2 would display 12/10/2012

How to remove "Server name" items from history of SQL Server Management Studio

As of SQL Server 2012 you no longer have to go through the hassle of deleting the bin file (which causes other side effects). You should be able to press the delete key within the MRU list of the Server Name dropdown in the Connect to Server dialog. This is documented in this Connect item and this blog post.

Note that if you have multiple entries for a single server name (e.g. one with Windows and one with SQL Auth), you won't be able to tell which one you're deleting.

LISTAGG in Oracle to return distinct values

select col1, listaggr(col2,',') within group(Order by col2) from table group by col1 meaning aggregate the strings (col2) into list keeping the order n then afterwards deal with the duplicates as group by col1 meaning merge col1 duplicates in 1 group. perhaps this looks clean and simple as it should be and if in case you want col3 as well just you need to add one more listagg() that is select col1, listaggr(col2,',') within group(Order by col2),listaggr(col3,',') within group(order by col3) from table group by col1

Redirecting unauthorized controller in ASP.NET MVC

I had the same issue. Rather than figure out the MVC code, I opted for a cheap hack that seems to work. In my Global.asax class:

member x.Application_EndRequest() =
  if x.Response.StatusCode = 401 then 
      let redir = "?redirectUrl=" + Uri.EscapeDataString x.Request.Url.PathAndQuery
      if x.Request.Url.LocalPath.ToLowerInvariant().Contains("admin") then
          x.Response.Redirect("/Login/Admin/" + redir)
      else
          x.Response.Redirect("/Login/Login/" + redir)

How to import an Oracle database from dmp file and log file?

All this peace of code put into *.bat file and run all at once:

My code for creating user in oracle. crate_drop_user.sql file

drop user "USER" cascade;
DROP TABLESPACE "USER";

CREATE TABLESPACE USER DATAFILE 'D:\ORA_DATA\ORA10\USER.ORA' SIZE 10M REUSE 
    AUTOEXTEND 
    ON NEXT  5M  EXTENT MANAGEMENT LOCAL 
    SEGMENT SPACE MANAGEMENT  AUTO
/ 

CREATE  TEMPORARY TABLESPACE "USER_TEMP" TEMPFILE 
    'D:\ORA_DATA\ORA10\USER_TEMP.ORA' SIZE 10M REUSE AUTOEXTEND
    ON NEXT  5M  EXTENT MANAGEMENT LOCAL 
    UNIFORM SIZE 1M    
/

CREATE USER "USER"  PROFILE "DEFAULT" 
    IDENTIFIED BY "user_password" DEFAULT TABLESPACE "USER" 
    TEMPORARY TABLESPACE "USER_TEMP" 
/    

alter user USER quota unlimited on "USER";

GRANT CREATE PROCEDURE TO "USER";
GRANT CREATE PUBLIC SYNONYM TO "USER";
GRANT CREATE SEQUENCE TO "USER";
GRANT CREATE SNAPSHOT TO "USER";
GRANT CREATE SYNONYM TO "USER";
GRANT CREATE TABLE TO "USER";
GRANT CREATE TRIGGER TO "USER";
GRANT CREATE VIEW TO "USER";
GRANT "CONNECT" TO "USER";
GRANT SELECT ANY DICTIONARY to "USER";
GRANT CREATE TYPE TO "USER";

create file import.bat and put this lines in it:

SQLPLUS SYSTEM/systempassword@ORA_alias @"crate_drop_user.SQL"
IMP SYSTEM/systempassword@ORA_alias FILE=user.DMP FROMUSER=user TOUSER=user GRANTS=Y log =user.log

Be carefull if you will import from one user to another. For example if you have user named user1 and you will import to user2 you may lost all grants , so you have to recreate it.

Good luck, Ivan

Can "list_display" in a Django ModelAdmin display attributes of ForeignKey fields?

I just posted a snippet that makes admin.ModelAdmin support '__' syntax:

http://djangosnippets.org/snippets/2887/

So you can do:

class PersonAdmin(RelatedFieldAdmin):
    list_display = ['book__author',]

This is basically just doing the same thing described in the other answers, but it automatically takes care of (1) setting admin_order_field (2) setting short_description and (3) modifying the queryset to avoid a database hit for each row.

Cannot connect to repo with TortoiseSVN

I've found that replacing the first part of the URL with IP address numbers instead of words worked for me.

For example use:

http://111.11.11.111/svn/Directory

instead of:

http://www.url.com/svn/Directory

Why is "npm install" really slow?

Problem: NPM does not perform well if you do not keep it up to date. However, bleeding edge versions have been broken for me in the past.

Solution: As Kraang mentioned, use node version manager nvm, with its --lts flag

Install it:

curl -o- https://raw.githubusercontent.com/creationix/nvm/master/install.sh | bash

Then use this often to upgrade to the latest "long-term support" version of NPM:

nvm install --lts

Big caveat: you'll likely have to reinstall all packages when you get a new npm version.

Efficient way to update all rows in a table

What is the database version? Check out virtual columns in 11g:

Adding Columns with a Default Value http://www.oracle.com/technology/pub/articles/oracle-database-11g-top-features/11g-schemamanagement.html

How should I call 3 functions in order to execute them one after the other?

If method 1 has to be executed after method 2, 3, 4. The following code snippet can be the solution for this using Deferred object in JavaScript.

_x000D_
_x000D_ 
function method1(){_x000D_
  var dfd = new $.Deferred();_x000D_
     setTimeout(function(){_x000D_
     console.log("Inside Method - 1"); _x000D_
     method2(dfd);  _x000D_
    }, 5000);_x000D_
  return dfd.promise();_x000D_
}_x000D_
_x000D_
function method2(dfd){_x000D_
  setTimeout(function(){_x000D_
   console.log("Inside Method - 2"); _x000D_
   method3(dfd); _x000D_
  }, 3000);_x000D_
}_x000D_
_x000D_
function method3(dfd){_x000D_
  setTimeout(function(){_x000D_
   console.log("Inside Method - 3");  _x000D_
   dfd.resolve();_x000D_
  }, 3000);_x000D_
}_x000D_
_x000D_
function method4(){   _x000D_
   console.log("Inside Method - 4");  _x000D_
}_x000D_
_x000D_
var call = method1();_x000D_
_x000D_
$.when(call).then(function(cb){_x000D_
  method4();_x000D_
});
_x000D_ 
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
_x000D_
_x000D_
_x000D_

Using R to list all files with a specified extension

 
files <- list.files(pattern = "\\.dbf$")

$ at the end means that this is end of string. "dbf$" will work too, but adding \\. (. is special character in regular expressions so you need to escape it) ensure that you match only files with extension .dbf (in case you have e.g. .adbf files).

Error message 'java.net.SocketException: socket failed: EACCES (Permission denied)'

try it.

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />

Android Canvas.drawText

Worked this out, turns out that android.R.color.black is not the same as Color.BLACK. Changed the code to:

Paint paint = new Paint(); 
paint.setColor(Color.WHITE); 
paint.setStyle(Style.FILL); 
canvas.drawPaint(paint); 

paint.setColor(Color.BLACK); 
paint.setTextSize(20); 
canvas.drawText("Some Text", 10, 25, paint);

and it all works fine now!!

Use Device Login on Smart TV / Console

They change it again. At this moment documentation does not fit actual situation.

Commonly all works as expected with one small difference. Login from Devices config now moves to Products -> Facebook Login.

So you need to:

  • get your App id from headline,
  • get Client Token from app Settings -> Advanced. There is also Native or desktop app? question/config. I turn it on.
  • Add product (just click on Add product and then Get started on Facebook login. Move back to your app config, click to newly added Facebook login and you'll see your Login from Devices config.

How can I convert bigint (UNIX timestamp) to datetime in SQL Server?

I had to face this problem, too. Unfortunately, none of the answers (here and in dozens of other pages) has been satisfactory to me, as I still cannot reach dates beyond the year 2038 due to 32 bit integer casts somewhere.

A solution that did work for me in the end was to use float variables, so I could have at least a max date of 2262-04-11T23:47:16.854775849. Still, this doesn't cover the entire datetime domain, but it is sufficient for my needs and may help others encountering the same problem.

-- date variables
declare @ts bigint; -- 64 bit time stamp, 100ns precision
declare @d datetime2(7) = GETUTCDATE(); -- 'now'
-- select @d = '2262-04-11T23:47:16.854775849'; -- this would be the max date

-- constants:
declare @epoch datetime2(7) = cast('1970-01-01T00:00:00' as datetime2(7));
declare @epochdiff int = 25567; -- = days between 1900-01-01 and 1970-01-01
declare @ticksofday bigint = 864000000000; -- = (24*60*60*1000*1000*10)

-- helper variables:
declare @datepart float;
declare @timepart float;
declare @restored datetime2(7);

-- algorithm:
select @ts = DATEDIFF_BIG(NANOSECOND, @epoch, @d) / 100; -- 'now' in ticks according to unix epoch
select @timepart = (@ts % @ticksofday) / @ticksofday; -- extract time part and scale it to fractional part (i. e. 1 hour is 1/24th of a day)
select @datepart = (@ts - @timepart) / @ticksofday; -- extract date part and scale it to fractional part
select @restored = cast(@epochdiff + @datepart + @timepart as datetime); -- rebuild parts to a datetime value

-- query original datetime, intermediate timestamp and restored datetime for comparison
select
  @d original,
  @ts unix64,
  @restored restored
;

-- example result for max date:
-- +-----------------------------+-------------------+-----------------------------+
-- | original                    | unix64            | restored                    |
-- +-----------------------------+-------------------+-----------------------------+
-- | 2262-04-11 23:47:16.8547758 | 92233720368547758 | 2262-04-11 23:47:16.8533333 |
-- +-----------------------------+-------------------+-----------------------------+

There are some points to consider:

  • 100ns precision is the requirement in my case, however this seems to be the standard resolution for 64 bit unix timestamps. If you use any other resolution, you have to adjust @ticksofday and the first line of the algorithm accordingly.
  • I'm using other systems that have their problems with time zones etc. and I found the best solution for me would be always using UTC. For your needs, this may differ.
  • 1900-01-01 is the origin date for datetime2, just as is the epoch 1970-01-01 for unix timestamps.
  • floats helped me to solve the year-2038-problem and integer overflows and such, but keep in mind that floating point numbers are not very performant and may slow down processing of a big amount of timestamps. Also, floats may lead to loss of precision due to roundoff errors, as you can see in the comparison of the example results for the max date above (here, the error is about 1.4425ms).
  • In the last line of the algorithm there is a cast to datetime. Unfortunately, there is no explicit cast from numeric values to datetime2 allowed, but it is allowed to cast numerics to datetime explicitly and this, in turn, is cast implicitly to datetime2. This may be correct, for now, but may change in future versions of SQL Server: Either there will be a dateadd_big() function or the explicit cast to datetime2 will be allowed or the explicit cast to datetime will be disallowed, so this may either break or there may come an easier way some day.

Manifest merger failed : uses-sdk:minSdkVersion 14

You have to configure all the supports and appcompat libraries with version 19.+

If the recommendation of leave the support library with the 19.+ version doesn't works you can try the next tip in your AndroidManifest file.

First add this code:

xmlns:tools="http://schemas.android.com/tools"

And then, at the application level (not inside application!) 

<uses-sdk tools:node="replace" />

How to remove "rows" with a NA value?

 
dat <- data.frame(x1 = c(1,2,3, NA, 5), x2 = c(100, NA, 300, 400, 500))

na.omit(dat)
  x1  x2
1  1 100
3  3 300
5  5 500

Difference between margin and padding?

Padding allows the developer to maintain space between the text and it's enclosing element. Margin is the space that the element maintains with another element of the parent DOM.

See example:

<head>
<meta http-equiv="Content-Type" content="text/html; charset=UT-8">
    <title>Pseudo Elements</title>
    <style type="text/css">
        body{font-family:Arial; font-size:16px; background-color:#f8e6ae; color:#888;}
        .page
        {
            background-color: #fff;
            padding: 10px 30px 50px 50px;
            margin:30px 100px 30px 300px;
        }
    </style>
</head>
<body>
    <div class="page">
        Notice the distance between the top and this text. Then compare it with the distance between the bottom border and the this text. 
    </div>
</body>

How to make a form close when pressing the escape key?

 
Button cancelBTN = new Button();
cancelBTN.Size = new Size(0, 0);
cancelBTN.TabStop = false;
this.Controls.Add(cancelBTN);
this.CancelButton = cancelBTN;

List an Array of Strings in alphabetical order

Here is code that works:

import java.util.Arrays;
import java.util.Collections;

public class Test
{
    public static void main(String[] args)
    {
        orderedGuests1(new String[] { "c", "a", "b" });
        orderedGuests2(new String[] { "c", "a", "b" });
    }

    public static void orderedGuests1(String[] hotel)
    {
        Arrays.sort(hotel);
        System.out.println(Arrays.toString(hotel));
    }

    public static void orderedGuests2(String[] hotel)
    {
        Collections.sort(Arrays.asList(hotel));
        System.out.println(Arrays.toString(hotel));
    }

}

Create an empty data.frame

You can do it without specifying column types

df = data.frame(matrix(vector(), 0, 3,
                dimnames=list(c(), c("Date", "File", "User"))),
                stringsAsFactors=F)

Calculating Distance between two Latitude and Longitude GeoCoordinates

And here, for those still not satisfied (like me), the original code from .NET-Frameworks GeoCoordinate class, refactored into a standalone method:

public double GetDistance(double longitude, double latitude, double otherLongitude, double otherLatitude)
{
    var d1 = latitude * (Math.PI / 180.0);
    var num1 = longitude * (Math.PI / 180.0);
    var d2 = otherLatitude * (Math.PI / 180.0);
    var num2 = otherLongitude * (Math.PI / 180.0) - num1;
    var d3 = Math.Pow(Math.Sin((d2 - d1) / 2.0), 2.0) + Math.Cos(d1) * Math.Cos(d2) * Math.Pow(Math.Sin(num2 / 2.0), 2.0);
    
    return 6376500.0 * (2.0 * Math.Atan2(Math.Sqrt(d3), Math.Sqrt(1.0 - d3)));
}

How do I convert an array object to a string in PowerShell?

I found that piping the array to the Out-String cmdlet works well too.

For example:

PS C:\> $a  | out-string

This
Is
a
cat

It depends on your end goal as to which method is the best to use.

Bash conditionals: how to "and" expressions? (if [ ! -z $VAR && -e $VAR ])

I found an answer now. Thanks for your suggestions!

for e in ./*.cutoff.txt; do
if grep -q -E 'COX1|Cu-oxidase' $e
then
    echo xyz >$e.match.txt
else
    echo
fi

if grep -q -E 'AMO' $e
then
    echo abc >$e.match.txt
else
    echo
fi; done

Any comments on that? It seems inefficient to grep twice, but it works...

How to represent the double quotes character (") in regex?

you need to use backslash before ". like \"

From the doc here you can see that

A character preceded by a backslash ( \ ) is an escape sequence and has special meaning to the compiler.

and " (double quote) is a escacpe sequence

When an escape sequence is encountered in a print statement, the compiler interprets it accordingly. For example, if you want to put quotes within quotes you must use the escape sequence, \", on the interior quotes. To print the sentence

She said "Hello!" to me.

you would write

System.out.println("She said \"Hello!\" to me.");

Initialize class fields in constructor or at declaration?

In Java, an initializer with the declaration means the field is always initialized the same way, regardless of which constructor is used (if you have more than one) or the parameters of your constructors (if they have arguments), although a constructor might subsequently change the value (if it is not final). So using an initializer with a declaration suggests to a reader that the initialized value is the value that the field has in all cases, regardless of which constructor is used and regardless of the parameters passed to any constructor. Therefore use an initializer with the declaration only if, and always if, the value for all constructed objects is the same.

How and where are Annotations used in Java?

Annotations in Java, provide a mean to describe classes, fields and methods. Essentially, they are a form of metadata added to a Java source file, they can't affect the semantics of a program directly. However, annotations can be read at run-time using Reflection & this process is known as Introspection. Then it could be used to modify classes, fields or methods.

This feature, is often exploited by Libraries & SDKs (hibernate, JUnit, Spring Framework) to simplify or reduce the amount of code that a programmer would unless do in orer to work with these Libraries or SDKs.Therefore, it's fair to say Annotations and Reflection work hand-in hand in Java.

We also get to limit the availability of an annotation to either compile-time or runtime.Below is a simple example on creating a custom annotation

Driver.java

package io.hamzeen;

import java.lang.annotation.Annotation;

public class Driver {

    public static void main(String[] args) {
        Class<TestAlpha> obj = TestAlpha.class;
        if (obj.isAnnotationPresent(IssueInfo.class)) {

            Annotation annotation = obj.getAnnotation(IssueInfo.class);
            IssueInfo testerInfo = (IssueInfo) annotation;

            System.out.printf("%nType: %s", testerInfo.type());
            System.out.printf("%nReporter: %s", testerInfo.reporter());
            System.out.printf("%nCreated On: %s%n%n",
                    testerInfo.created());
        }
    }
}

TestAlpha.java

package io.hamzeen;

import io.hamzeen.IssueInfo;
import io.hamzeen.IssueInfo.Type;

@IssueInfo(type = Type.IMPROVEMENT, reporter = "Hamzeen. H.")
public class TestAlpha {

}

IssueInfo.java

package io.hamzeen;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * @author Hamzeen. H.
 * @created 10/01/2015
 * 
 * IssueInfo annotation definition
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface IssueInfo {

    public enum Type {
        BUG, IMPROVEMENT, FEATURE
    }

    Type type() default Type.BUG;

    String reporter() default "Vimesh";

    String created() default "10/01/2015";
}

What is the purpose of flush() in Java streams?

When you write data to a stream, it is not written immediately, and it is buffered. So use flush() when you need to be sure that all your data from buffer is written.

We need to be sure that all the writes are completed before we close the stream, and that is why flush() is called in file/buffered writer's close().

But if you have a requirement that all your writes be saved anytime before you close the stream, use flush().

How to make an HTML back link?

For going back to previous page using Anchor Tag <a>, below are 2 working methods and out of them 1st one is faster and have one great advantage in going back to previous page.

I have tried both methods.

1)

<a href="#" onclick="location.href = document.referrer; return false;">Go Back</a>

Above method (1) works great if you have clicked on a link and opened link in a New Tab in current browser window.

2)

<a href="javascript:history.back()">Go Back</a>

Above method (2) only works ok if you have clicked on a link and opened link in a Current Tab in current browser window.

It will not work if you have open link in New Tab. Here history.back() will not work if link is opened in New Tab of web browser.

Different ways of adding to Dictionary

One is assigning a value while the other is adding to the Dictionary a new Key and Value.

How to initialize all the elements of an array to any specific value in java

There's also

int[] array = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1};

How to resolve Error : Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation

You can't show dialog box ON SERVER from ASP.NET application, well of course tehnically you can do that but it makes no sense since your user is using browser and it can't see messages raised on server. You have to understand how web sites work, server side code (ASP.NET in your case) produces html, javascript etc on server and then browser loads that content and displays it to the user, so in order to present modal message box to the user you have to use Javascript, for example alert function.

Here is the example for asp.net :

https://www.madskristensen.net/blog/javascript-alertshow(e2809dmessagee2809d)-from-aspnet-code-behind/

How do you parse and process HTML/XML in PHP?

You could try using something like HTML Tidy to cleanup any "broken" HTML and convert the HTML to XHTML, which you can then parse with a XML parser.

Calling a javascript function recursively

Using Named Function Expressions:

You can give a function expression a name that is actually private and is only visible from inside of the function ifself:

var factorial = function myself (n) {
    if (n <= 1) {
        return 1;
    }
    return n * myself(n-1);
}
typeof myself === 'undefined'

Here myself is visible only inside of the function itself.

You can use this private name to call the function recursively.

See 13. Function Definition of the ECMAScript 5 spec:

The Identifier in a FunctionExpression can be referenced from inside the FunctionExpression's FunctionBody to allow the function to call itself recursively. However, unlike in a FunctionDeclaration, the Identifier in a FunctionExpression cannot be referenced from and does not affect the scope enclosing the FunctionExpression.

Please note that Internet Explorer up to version 8 doesn't behave correctly as the name is actually visible in the enclosing variable environment, and it references a duplicate of the actual function (see patrick dw's comment below).

Using arguments.callee:

Alternatively you could use arguments.callee to refer to the current function:

var factorial = function (n) {
    if (n <= 1) {
        return 1;
    }
    return n * arguments.callee(n-1);
}

The 5th edition of ECMAScript forbids use of arguments.callee() in strict mode, however:

(From MDN): In normal code arguments.callee refers to the enclosing function. This use case is weak: simply name the enclosing function! Moreover, arguments.callee substantially hinders optimizations like inlining functions, because it must be made possible to provide a reference to the un-inlined function if arguments.callee is accessed. arguments.callee for strict mode functions is a non-deletable property which throws when set or retrieved.

How can I get Docker Linux container information from within the container itself?

I've found that in 17.09 there is a simplest way to do it within docker container:

$ cat /proc/self/cgroup | head -n 1 | cut -d '/' -f3
4de1c09d3f1979147cd5672571b69abec03d606afcc7bdc54ddb2b69dec3861c

Or like it has already been told, a shorter version with

$ cat /etc/hostname
4de1c09d3f19

Or simply:

$ hostname
4de1c09d3f19

Purpose of #!/usr/bin/python3 shebang

  1. And this line is how.

  2. It is ignored.

  3. It will fail to run, and should be changed to point to the proper location. Or env should be used.

  4. It will fail to run, and probably fail to run under a different version regardless.

Maven error "Failure to transfer..."

Give correct maven setting.xml path in eclipse.

  • Windows --> Preference --> Maven --> User Settings

Enter correct setting.xml path in user settings text box

Difference between volatile and synchronized in Java

It's important to understand that there are two aspects to thread safety.

  1. execution control, and
  2. memory visibility

The first has to do with controlling when code executes (including the order in which instructions are executed) and whether it can execute concurrently, and the second to do with when the effects in memory of what has been done are visible to other threads. Because each CPU has several levels of cache between it and main memory, threads running on different CPUs or cores can see "memory" differently at any given moment in time because threads are permitted to obtain and work on private copies of main memory.

Using synchronized prevents any other thread from obtaining the monitor (or lock) for the same object, thereby preventing all code blocks protected by synchronization on the same object from executing concurrently. Synchronization also creates a "happens-before" memory barrier, causing a memory visibility constraint such that anything done up to the point some thread releases a lock appears to another thread subsequently acquiring the same lock to have happened before it acquired the lock. In practical terms, on current hardware, this typically causes flushing of the CPU caches when a monitor is acquired and writes to main memory when it is released, both of which are (relatively) expensive.

Using volatile, on the other hand, forces all accesses (read or write) to the volatile variable to occur to main memory, effectively keeping the volatile variable out of CPU caches. This can be useful for some actions where it is simply required that visibility of the variable be correct and order of accesses is not important. Using volatile also changes treatment of long and double to require accesses to them to be atomic; on some (older) hardware this might require locks, though not on modern 64 bit hardware. Under the new (JSR-133) memory model for Java 5+, the semantics of volatile have been strengthened to be almost as strong as synchronized with respect to memory visibility and instruction ordering (see http://www.cs.umd.edu/users/pugh/java/memoryModel/jsr-133-faq.html#volatile). For the purposes of visibility, each access to a volatile field acts like half a synchronization.

Under the new memory model, it is still true that volatile variables cannot be reordered with each other. The difference is that it is now no longer so easy to reorder normal field accesses around them. Writing to a volatile field has the same memory effect as a monitor release, and reading from a volatile field has the same memory effect as a monitor acquire. In effect, because the new memory model places stricter constraints on reordering of volatile field accesses with other field accesses, volatile or not, anything that was visible to thread A when it writes to volatile field f becomes visible to thread B when it reads f.

-- JSR 133 (Java Memory Model) FAQ

So, now both forms of memory barrier (under the current JMM) cause an instruction re-ordering barrier which prevents the compiler or run-time from re-ordering instructions across the barrier. In the old JMM, volatile did not prevent re-ordering. This can be important, because apart from memory barriers the only limitation imposed is that, for any particular thread, the net effect of the code is the same as it would be if the instructions were executed in precisely the order in which they appear in the source.

One use of volatile is for a shared but immutable object is recreated on the fly, with many other threads taking a reference to the object at a particular point in their execution cycle. One needs the other threads to begin using the recreated object once it is published, but does not need the additional overhead of full synchronization and it's attendant contention and cache flushing.

// Declaration
public class SharedLocation {
    static public SomeObject someObject=new SomeObject(); // default object
    }

// Publishing code
// Note: do not simply use SharedLocation.someObject.xxx(), since although
//       someObject will be internally consistent for xxx(), a subsequent 
//       call to yyy() might be inconsistent with xxx() if the object was 
//       replaced in between calls.
SharedLocation.someObject=new SomeObject(...); // new object is published

// Using code
private String getError() {
    SomeObject myCopy=SharedLocation.someObject; // gets current copy
    ...
    int cod=myCopy.getErrorCode();
    String txt=myCopy.getErrorText();
    return (cod+" - "+txt);
    }
// And so on, with myCopy always in a consistent state within and across calls
// Eventually we will return to the code that gets the current SomeObject.

Speaking to your read-update-write question, specifically. Consider the following unsafe code:

public void updateCounter() {
    if(counter==1000) { counter=0; }
    else              { counter++; }
    }

Now, with the updateCounter() method unsynchronized, two threads may enter it at the same time. Among the many permutations of what could happen, one is that thread-1 does the test for counter==1000 and finds it true and is then suspended. Then thread-2 does the same test and also sees it true and is suspended. Then thread-1 resumes and sets counter to 0. Then thread-2 resumes and again sets counter to 0 because it missed the update from thread-1. This can also happen even if thread switching does not occur as I have described, but simply because two different cached copies of counter were present in two different CPU cores and the threads each ran on a separate core. For that matter, one thread could have counter at one value and the other could have counter at some entirely different value just because of caching.

What's important in this example is that the variable counter was read from main memory into cache, updated in cache and only written back to main memory at some indeterminate point later when a memory barrier occurred or when the cache memory was needed for something else. Making the counter volatile is insufficient for thread-safety of this code, because the test for the maximum and the assignments are discrete operations, including the increment which is a set of non-atomic read+increment+write machine instructions, something like: 

MOV EAX,counter
INC EAX
MOV counter,EAX

Volatile variables are useful only when all operations performed on them are "atomic", such as my example where a reference to a fully formed object is only read or written (and, indeed, typically it's only written from a single point). Another example would be a volatile array reference backing a copy-on-write list, provided the array was only read by first taking a local copy of the reference to it.

Python : Trying to POST form using requests

I was having problems here (i.e. sending form-data whilst uploading a file) until I used the following:

files = {'file': (filename, open(filepath, 'rb'), 'text/xml'),
         'Content-Disposition': 'form-data; name="file"; filename="' + filename + '"',
         'Content-Type': 'text/xml'}

That's the input that ended up working for me. In Chrome Dev Tools -> Network tab, I clicked the request I was interested in. In the Headers tab, there's a Form Data section, and it showed both the Content-Disposition and the Content-Type headers being set there.

I did NOT need to set headers in the actual requests.post() command for this to succeed (including them actually caused it to fail)

How do I check if a string contains another string in Swift?

string.containsString is only available in 10.10 Yosemite (and probably iOS8). Also bridging it to ObjectiveC crashes in 10.9. You're trying to pass a NSString to NSCFString. I don't know the difference, but I can say 10.9 barfs when it executes this code in a OS X 10.9 app.

Here are the differences in Swift with 10.9 and 10.10: https://developer.apple.com/library/prerelease/mac/documentation/General/Reference/APIDiffsMacOSX10_10SeedDiff/index.html containsString is only available in 10.10

Range of String above works great on 10.9. I am finding developing on 10.9 is super stable with Xcode beta2. I don't use playgrounds through or the command line version of playgrounds. I'm finding if the proper frameworks are imported the autocomplete is very helpful.

How to access data/data folder in Android device?

If you are using Android Studio 3.0 or later version then follow these steps.

  1. Click View > Tool Windows > Device File Explorer.
  2. Expand /data/data/[package-name] nodes.

You can only expand packages which runs in debug mode on non-rooted device.

Steps followed in Android Studio 3.0

Where value in column containing comma delimited values

 
SELECT * FROM TABLE_NAME WHERE
        (
            LOCATE(',DOG,', CONCAT(',',COLUMN,','))>0 OR
            LOCATE(',CAT,', CONCAT(',',COLUMN,','))>0
        );

Provide password to ssh command inside bash script, Without the usage of public keys and Expect

Install sshpass, then launch the command:

sshpass -p "yourpassword" ssh -o StrictHostKeyChecking=no yourusername@hostname

Using ChildActionOnly in MVC

FYI, [ChildActionOnly] is not available in ASP.NET MVC Core. see some info here

How to create an empty matrix in R?

To get rid of the first column of NAs, you can do it with negative indexing (which removes indices from the R data set). For example:

output = matrix(1:6, 2, 3) # gives you a 2 x 3 matrix filled with the numbers 1 to 6

# output = 
#           [,1] [,2] [,3]
#     [1,]    1    3    5
#     [2,]    2    4    6

output = output[,-1] # this removes column 1 for all rows

# output = 
#           [,1] [,2]
#     [1,]    3    5
#     [2,]    4    6

So you can just add output = output[,-1]after the for loop in your original code.

Manipulate a url string by adding GET parameters

 
 public function addGetParamToUrl($url, $params)
{
    foreach ($params as $param) {
         if (strpos($url, "?"))
        {
            $url .= "&" .http_build_query($param); 
        }
        else
        {
            $url .= "?" .http_build_query($param); 
        }
    }
    return $url;
}

Deserialize JSON to ArrayList<POJO> using Jackson

Another way is to use an array as a type, e.g.:

ObjectMapper objectMapper = new ObjectMapper();
MyPojo[] pojos = objectMapper.readValue(json, MyPojo[].class);

This way you avoid all the hassle with the Type object, and if you really need a list you can always convert the array to a list by:

List<MyPojo> pojoList = Arrays.asList(pojos);

IMHO this is much more readable.

And to make it be an actual list (that can be modified, see limitations of Arrays.asList()) then just do the following:

List<MyPojo> mcList = new ArrayList<>(Arrays.asList(pojos));

Difference of two date time in sql server

 
SELECT DATEDIFF (MyUnits, '2010-01-22 15:29:55.090', '2010-01-22 15:30:09.153')

Substitute "MyUnits" based on DATEDIFF on MSDN

How do I make text bold in HTML?

The Markup Way:

<strong>I'm Bold!</strong> and <b>I'm Bold Too!</b>

The Styling Way:

.bold {
  font-weight:bold;
}

<span class="bold">I'm Bold!</span>

From: http://www.december.com/html/x1/

<b>

This element encloses text which should be rendered by the browser as boldface. Because the meaning of the B element defines the appearance of the content it encloses, this element is considered a "physical" markup element. As such, it doesn't convey the meaning of a semantic markup element such as strong.

<strong>

Description This element brackets text which should be strongly emphasized. Stronger than the em element.

How to set corner radius of imageView?

try this

self.mainImageView.layer.cornerRadius = CGRectGetWidth(self.mainImageView.frame)/4.0
self.mainImageView.clipsToBounds = true

AngularJs directive not updating another directive's scope

Just wondering why you are using 2 directives?

It seems like, in this case it would be more straightforward to have a controller as the parent - handle adding the data from your service to its $scope, and pass the model you need from there into your warrantyDirective.

Or for that matter, you could use 0 directives to achieve the same result. (ie. move all functionality out of the separate directives and into a single controller).

It doesn't look like you're doing any explicit DOM transformation here, so in this case, perhaps using 2 directives is overcomplicating things.

Alternatively, have a look at the Angular documentation for directives: http://docs.angularjs.org/guide/directive The very last example at the bottom of the page explains how to wire up dependent directives.

What is the difference between an int and an Integer in Java and C#?

Well, in Java an int is a primitive while an Integer is an Object. Meaning, if you made a new Integer:

Integer i = new Integer(6);

You could call some method on i:

String s = i.toString();//sets s the string representation of i

Whereas with an int:

int i = 6;

You cannot call any methods on it, because it is simply a primitive. So:

String s = i.toString();//will not work!!!

would produce an error, because int is not an object.

int is one of the few primitives in Java (along with char and some others). I'm not 100% sure, but I'm thinking that the Integer object more or less just has an int property and a whole bunch of methods to interact with that property (like the toString() method for example). So Integer is a fancy way to work with an int (Just as perhaps String is a fancy way to work with a group of chars).

I know that Java isn't C, but since I've never programmed in C this is the closest I could come to the answer. Hope this helps!

Integer object javadoc

Integer Ojbect vs. int primitive comparison

"Use of undeclared type" in Swift, even though type is internal, and exists in same module

Cleaning the project solved my problem.

Steps: Product -> Clean(or Shift + Cmd + K)

Laravel: How do I parse this json data in view blade?

It's pretty easy. First of all send to the view decoded variable (see Laravel Views):

view('your-view')->with('leads', json_decode($leads, true));

Then just use common blade constructions (see Laravel Templating):

@foreach($leads['member'] as $member)
    Member ID: {{ $member['id'] }}
    Firstname: {{ $member['firstName'] }}
    Lastname: {{ $member['lastName'] }}
    Phone: {{ $member['phoneNumber'] }}

    Owner ID: {{ $member['owner']['id'] }}
    Firstname: {{ $member['owner']['firstName'] }} 
    Lastname: {{ $member['owner']['lastName'] }}
@endforeach

How to execute a query in ms-access in VBA code?

How about something like this...

Dim rs As RecordSet
Set rs = Currentdb.OpenRecordSet("SELECT PictureLocation, ID FROM MyAccessTable;")

Do While Not rs.EOF
   Debug.Print rs("PictureLocation") & " - " & rs("ID")
   rs.MoveNext
Loop

Linq select object from list depending on objects attribute

Of course!

Use FirstOrDefault() to select the first object which matches the condition:

Answer answer = Answers.FirstOrDefault(a => a.Correct);

Otherwise use Where() to select a subset of your list:

var answers = Answers.Where(a => a.Correct);

How to reset (clear) form through JavaScript?

You can clear the whole form using onclick function.Here is the code for it.

 <button type="reset" value="reset" type="reset" class="btnreset" onclick="window.location.reload()">Reset</button>

window.location.reload() function will refresh your page and all data will clear.

What does the error "arguments imply differing number of rows: x, y" mean?

Your data.frame mat is rectangular (n_rows!= n_cols).

Therefore, you cannot make a data.frame out of the column- and rownames, because each column in a data.frame must be the same length.

Maybe this suffices your needs:

require(reshape2)
mat$id <- rownames(mat) 
melt(mat)

Removing All Items From A ComboBox?

You need to remove each one individually unfortunately:

       For i = 1 To ListBox1.ListCount

           'Remove an item from the ListBox using ListBox1.RemoveItem 
       Next i

Update - I don't know why my answer did not include the full solution:

For i = ListBox1.ListCount - 1 to 0 Step - 1 
        ListBox1.RemoveItem i 
Next i

EnterKey to press button in VBA Userform

You could also use the TextBox's On Key Press event handler:

'Keycode for "Enter" is 13
Private Sub TextBox1_KeyDown(KeyCode As Integer, Shift As Integer)
    If KeyCode = 13 Then
         Logincode_Click
    End If
End Sub

Textbox1 is an example. Make sure you choose the textbox you want to refer to and also Logincode_Click is an example sub which you call (run) with this code. Make sure you refer to your preferred sub

Getting the last element of a split string array

There's a one-liner for everything. :)

var output = input.split(/[, ]+/).pop();

How do I kill background processes / jobs when my shell script exits?

This works for me (improved thanks to the commenters):

trap "trap - SIGTERM && kill -- -$$" SIGINT SIGTERM EXIT

  • kill -- -$$ sends a SIGTERM to the whole process group, thus killing also descendants.

  • Specifying signal EXIT is useful when using set -e (more details here).

Create Directory When Writing To File In Node.js

My advise is: try not to rely on dependencies when you can easily do it with few lines of codes

Here's what you're trying to achieve in 14 lines of code:

fs.isDir = function(dpath) {
    try {
        return fs.lstatSync(dpath).isDirectory();
    } catch(e) {
        return false;
    }
};
fs.mkdirp = function(dirname) {
    dirname = path.normalize(dirname).split(path.sep);
    dirname.forEach((sdir,index)=>{
        var pathInQuestion = dirname.slice(0,index+1).join(path.sep);
        if((!fs.isDir(pathInQuestion)) && pathInQuestion) fs.mkdirSync(pathInQuestion);
    });
};

php artisan migrate throwing [PDO Exception] Could not find driver - Using Laravel

just replaced: ;extension=pdo_mysql to extension=pdo_mysql in php.ini file.

BeautifulSoup: extract text from anchor tag

All the above answers really help me to construct my answer, because of this I voted for all the answers that other users put it out: But I finally put together my own answer to exact problem I was dealing with:

As question clearly defined I had to access some of the siblings and its children in a dom structure: This solution will iterate over the images in the dom structure and construct image name using product title and save the image to the local directory. 

import urlparse
from urllib2 import urlopen
from urllib import urlretrieve
from BeautifulSoup import BeautifulSoup as bs
import requests

def getImages(url):
    #Download the images
    r = requests.get(url)
    html = r.text
    soup = bs(html)
    output_folder = '~/amazon'
    #extracting the images that in div(s)
    for div in soup.findAll('div', attrs={'class':'image'}):
        modified_file_name = None
        try:
            #getting the data div using findNext
            nextDiv =  div.findNext('div', attrs={'class':'data'})
            #use findNext again on previous object to get to the anchor tag
            fileName = nextDiv.findNext('a').text
            modified_file_name = fileName.replace(' ','-') + '.jpg'
        except TypeError:
            print 'skip'
        imageUrl = div.find('img')['src']
        outputPath = os.path.join(output_folder, modified_file_name)
        urlretrieve(imageUrl, outputPath)

if __name__=='__main__':
    url = r'http://www.amazon.com/s/ref=sr_pg_1?rh=n%3A172282%2Ck%3Adigital+camera&keywords=digital+camera&ie=UTF8&qid=1343600585'
    getImages(url)

XPath OR operator for different nodes

If you want to select only one of two nodes with union operator, you can use this solution: (//bookstore/book/title | //bookstore/city/zipcode/title)[1]

Adding a default value in dropdownlist after binding with database

design

<asp:DropDownList ID="ddlArea" DataSourceID="ldsArea" runat="server" ondatabound="ddlArea_DataBound" />

codebehind

protected void ddlArea_DataBound(object sender, EventArgs e)
{
    ddlArea.Items.Insert(0, new ListItem("--Select--", "0"));
}

Select method in List<t> Collection

Try this:

using System.Data.Linq;
var result = from i in list
             where i.age > 45
             select i;

Using lambda expression please use this Statement:

var result = list.where(i => i.age > 45);

Custom sort function in ng-repeat

Actually the orderBy filter can take as a parameter not only a string but also a function. From the orderBy documentation: https://docs.angularjs.org/api/ng/filter/orderBy):

function: Getter function. The result of this function will be sorted using the <, =, > operator.

So, you could write your own function. For example, if you would like to compare cards based on a sum of opt1 and opt2 (I'm making this up, the point is that you can have any arbitrary function) you would write in your controller:

$scope.myValueFunction = function(card) {
   return card.values.opt1 + card.values.opt2;
};

and then, in your template:

ng-repeat="card in cards | orderBy:myValueFunction"

Here is the working jsFiddle

The other thing worth noting is that orderBy is just one example of AngularJS filters so if you need a very specific ordering behaviour you could write your own filter (although orderBy should be enough for most uses cases).

MySQL LIKE IN()?

Paul Dixon's answer worked brilliantly for me. To add to this, here are some things I observed for those interested in using REGEXP:

To Accomplish multiple LIKE filters with Wildcards:

 SELECT * FROM fiberbox WHERE field LIKE '%1740 %'
                           OR field LIKE '%1938 %'
                           OR field LIKE '%1940 %';

Use REGEXP Alternative:

 SELECT * FROM fiberbox WHERE field REGEXP '1740 |1938 |1940 ';

Values within REGEXP quotes and between the | (OR) operator are treated as wildcards. Typically, REGEXP will require wildcard expressions such as (.*)1740 (.*) to work as %1740 %.

If you need more control over placement of the wildcard, use some of these variants:

To Accomplish LIKE with Controlled Wildcard Placement:

SELECT * FROM fiberbox WHERE field LIKE '1740 %'
                          OR field LIKE '%1938 '
                          OR field LIKE '%1940 % test';

Use:

SELECT * FROM fiberbox WHERE field REGEXP '^1740 |1938 $|1940 (.*) test';

  • Placing ^ in front of the value indicates start of the line.

  • Placing $ after the value indicates end of line.

  • Placing (.*) behaves much like the % wildcard.

  • The . indicates any single character, except line breaks. Placing . inside () with * (.*) adds a repeating pattern indicating any number of characters till end of line.

There are more efficient ways to narrow down specific matches, but that requires more review of Regular Expressions. NOTE: Not all regex patterns appear to work in MySQL statements. You'll need to test your patterns and see what works.

Finally, To Accomplish Multiple LIKE and NOT LIKE filters:

SELECT * FROM fiberbox WHERE field LIKE '%1740 %'
                          OR field LIKE '%1938 %'
                          OR field NOT LIKE '%1940 %'
                          OR field NOT LIKE 'test %'
                          OR field = '9999';

Use REGEXP Alternative:

SELECT * FROM fiberbox WHERE field REGEXP '1740 |1938 |^9999$'
                          OR field NOT REGEXP '1940 |^test ';

OR Mixed Alternative:

SELECT * FROM fiberbox WHERE field REGEXP '1740 |1938 '
                          OR field NOT REGEXP '1940 |^test '
                          OR field NOT LIKE 'test %'
                          OR field = '9999';

Notice I separated the NOT set in a separate WHERE filter. I experimented with using negating patterns, forward looking patterns, and so on. However, these expressions did not appear to yield the desired results. In the first example above, I use ^9999$ to indicate exact match. This allows you to add specific matches with wildcard matches in the same expression. However, you can also mix these types of statements as you can see in the second example listed.

Regarding performance, I ran some minor tests against an existing table and found no differences between my variations. However, I imagine performance could be an issue with bigger databases, larger fields, greater record counts, and more complex filters.

As always, use logic above as it makes sense.

If you want to learn more about regular expressions, I recommend www.regular-expressions.info as a good reference site.

Git: cannot checkout branch - error: pathspec '...' did not match any file(s) known to git

Alright, there are too many answers already. But in my case, I faced this issue while I was working on Eclipse and using git-bash to switch between branches/checkouts. Once I closed the eclipse and relaunched the git-bash to checkout branch everything worked well.

So my suggestion for you to double check if your repository is not being used by another application.

mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists

When I used the code mysqld_safe --skip-grant-tables & but I get the error:

mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists.

$ systemctl stop  mysql.service
$ ps -eaf|grep mysql
$ mysqld_safe --skip-grant-tables &

I solved:

$ mkdir -p /var/run/mysqld
$ chown mysql:mysql /var/run/mysqld

Now I use the same code mysqld_safe --skip-grant-tables & and get

mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

If I use $ mysql -u root I'll get :

Server version: 5.7.18-0ubuntu0.16.04.1 (Ubuntu)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

Now time to change password:

mysql> use mysql
mysql> describe user;

Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A

Database changed

mysql> FLUSH PRIVILEGES;
mysql> SET PASSWORD FOR root@'localhost' = PASSWORD('newpwd');

or If you have a mysql root account that can connect from everywhere, you should also do:

UPDATE mysql.user SET Password=PASSWORD('newpwd') WHERE User='root';

Alternate Method:

   USE mysql
   UPDATE user SET Password = PASSWORD('newpwd')
   WHERE Host = 'localhost' AND User = 'root';

And if you have a root account that can access from everywhere:

 USE mysql
 UPDATE user SET Password = PASSWORD('newpwd')
 WHERE Host = '%' AND User = 'root';`enter code here

now need to quit from mysql and stop/start

FLUSH PRIVILEGES;
sudo /etc/init.d/mysql stop
sudo /etc/init.d/mysql start

now again ` mysql -u root -p' and use the new password to get

mysql>

SQL Server 2008 R2 can't connect to local database in Management Studio

Lots of the above helped for me, plus the accepted answer, but since I was on an EC2 instance, I had no idea what my instance name was. Finally, I opened SQLServer Configuration Manager and in the Name column, use whatever is there as your connection server, so in my case, .\EC2SQLEXPRESS and worked great!

enter image description here

Passing parameters to JavaScript files

might be very simple

for example 

<script src="js/myscript.js?id=123"></script>
<script>
    var queryString = $("script[src*='js/myscript.js']").attr('src').split('?')[1];
</script>

You can then convert query string into json like below

var json = $.parseJSON('{"' 
            + queryString.replace(/&/g, '","').replace(/=/g, '":"') 
            + '"}');

and then can use like 

console.log(json.id);

grant remote access of MySQL database from any IP address

You can slove the problem of MariaDB via this command:

Note:

GRANT ALL ON *.* to root@'%' IDENTIFIED BY 'mysql root password';

% is a wildcard. In this case, it refers to all IP addresses.

How do I remove whitespace from the end of a string in Python?

You can use strip() or split() to control the spaces values as in the following:

words = "   first  second   "

# Remove end spaces
def remove_end_spaces(string):
    return "".join(string.rstrip())


# Remove the first and end spaces
def remove_first_end_spaces(string):
    return "".join(string.rstrip().lstrip())


# Remove all spaces
def remove_all_spaces(string):
    return "".join(string.split())


# Show results
print(words)
print(remove_end_spaces(words))
print(remove_first_end_spaces(words))
print(remove_all_spaces(words))

Is there a way to ignore a single FindBugs warning?

The FindBugs initial approach involves XML configuration files aka filters. This is really less convenient than the PMD solution but FindBugs works on bytecode, not on the source code, so comments are obviously not an option. Example:

<Match>
   <Class name="com.mycompany.Foo" />
   <Method name="bar" />
   <Bug pattern="DLS_DEAD_STORE_OF_CLASS_LITERAL" />
</Match>

However, to solve this issue, FindBugs later introduced another solution based on annotations (see SuppressFBWarnings) that you can use at the class or at the method level (more convenient than XML in my opinion). Example (maybe not the best one but, well, it's just an example):

@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(
    value="HE_EQUALS_USE_HASHCODE", 
    justification="I know what I'm doing")

Note that since FindBugs 3.0.0 SuppressWarnings has been deprecated in favor of @SuppressFBWarnings because of the name clash with Java's SuppressWarnings.

make sounds (beep) with c++

The ASCII bell character might be what you are looking for. Number 7 in this table.

What "wmic bios get serialnumber" actually retrieves?

 
wmic bios get serialnumber

if run from a command line (start-run should also do the trick) prints out on screen the Serial Number of the product,
(for example in a toshiba laptop it would print out the serial number of the laptop.
with this serial number you can then identify your laptop model if you need ,from the makers service website-usually..:):)

I had to do exactly that.:):)

API Gateway CORS: no 'Access-Control-Allow-Origin' header

In Python you can do it as in the code below:

{ "statusCode" : 200,
'headers': 
    {'Content-Type': 'application/json',
    'Access-Control-Allow-Origin': "*"
     },
"body": json.dumps(
    {
    "temperature" : tempArray,
    "time": timeArray
    })
 }

How to efficiently build a tree from a flat structure?

It's not exactly the same as what the asker looked for, but I had difficulty wrapping my head around the ambiguously phrased answers provided here, and I still think this answer fits under the title.

My answer is for mapping a flat structure to a directly-on-object tree where all you have is a ParentID on each object. ParentID is null or 0 if it is a root. Opposite of the asker, I assume all valid ParentID's point to something else in the list:

var rootNodes = new List<DTIntranetMenuItem>();
var dictIntranetMenuItems = new Dictionary<long, DTIntranetMenuItem>();

//Convert the flat database items to the DTO's,
//that has a list of children instead of a ParentID.
foreach (var efIntranetMenuItem in flatIntranetMenuItems) //List<tblIntranetMenuItem>
{
    //Automapper (nuget)
    DTIntranetMenuItem intranetMenuItem =
                                   Mapper.Map<DTIntranetMenuItem>(efIntranetMenuItem);
    intranetMenuItem.Children = new List<DTIntranetMenuItem>();
    dictIntranetMenuItems.Add(efIntranetMenuItem.ID, intranetMenuItem);
}

foreach (var efIntranetMenuItem in flatIntranetMenuItems)
{
    //Getting the equivalent object of the converted ones
    DTIntranetMenuItem intranetMenuItem = dictIntranetMenuItems[efIntranetMenuItem.ID];

    if (efIntranetMenuItem.ParentID == null || efIntranetMenuItem.ParentID <= 0)
    {
        rootNodes.Add(intranetMenuItem);
    }
    else
    {
        var parent = dictIntranetMenuItems[efIntranetMenuItem.ParentID.Value];
        parent.Children.Add(intranetMenuItem);
        //intranetMenuItem.Parent = parent;
    }
}
return rootNodes;

Cannot set some HTTP headers when using System.Net.WebRequest

WebRequest being abstract (and since any inheriting class must override the Headers property).. which concrete WebRequest are you using ? In other words, how do you get that WebRequest object to beign with ?

ehr.. mnour answer made me realize that the error message you were getting is actually spot on: it's telling you that the header you are trying to add already exist and you should then modify its value using the appropriate property (the indexer, for instance), instead of trying to add it again. That's probably all you were looking for.

Other classes inheriting from WebRequest might have even better properties wrapping certain headers; See this post for instance.

How do I import a .dmp file into Oracle?

 
imp system/system-password@SID file=directory-you-selected\FILE.dmp log=log-dir\oracle_load.log fromuser=infodba touser=infodba commit=Y

JQuery post JSON object to a server

To send json to the server, you first have to create json

function sendData() {
    $.ajax({
        url: '/helloworld',
        type: 'POST',
        contentType: 'application/json',
        data: JSON.stringify({
            name:"Bob",
            ...
        }),
        dataType: 'json'
    });
}

This is how you would structure the ajax request to send the json as a post var.

function sendData() {
    $.ajax({
        url: '/helloworld',
        type: 'POST',
        data: { json: JSON.stringify({
            name:"Bob",
            ...
        })},
        dataType: 'json'
    });
}

The json will now be in the json post var.

Add IIS 7 AppPool Identities as SQL Server Logons

I figured it out through trial and error... the real chink in the armor was a little known setting in IIS in the Configuration Editor for the website in

Section: system.webServer/security/authentication/windowsAuthentication

From: ApplicationHost.config <locationpath='ServerName/SiteName' />

called useAppPoolCredentials (which is set to False by default. Set this to True and life becomes great again!!! Hope this saves pain for the next guy....

enter image description here

Git says remote ref does not exist when I delete remote branch

For me this worked $ ? git branch -D -r origin/mybranch

Details

$ ? git branch -a | grep mybranch remotes/origin/mybranch

$ ? git branch -r | grep mybranch origin/mybranch

$ ? git branch develop * feature/pre-deployment

$ ? git push origin --delete mybranch error: unable to delete 'mybranch': remote ref does not exist error: failed to push some refs to '[email protected]:config/myrepo.git'

$ ? git branch -D -r origin/mybranch Deleted remote branch origin/mybranch (was 62c7421).

$ ? git branch -a | grep mybranch

$ ? git branch -r | grep mybranch

Server.UrlEncode vs. HttpUtility.UrlEncode

I had significant headaches with these methods before, I recommend you avoid any variant of UrlEncode, and instead use Uri.EscapeDataString - at least that one has a comprehensible behavior.

Let's see...

HttpUtility.UrlEncode(" ") == "+" //breaks ASP.NET when used in paths, non-
                                  //standard, undocumented.
Uri.EscapeUriString("a?b=e") == "a?b=e" // makes sense, but rarely what you
                                        // want, since you still need to
                                        // escape special characters yourself

But my personal favorite has got to be HttpUtility.UrlPathEncode - this thing is really incomprehensible. It encodes:

  • " " ==> "%20"
  • "100% true" ==> "100%%20true" (ok, your url is broken now)
  • "test A.aspx#anchor B" ==> "test%20A.aspx#anchor%20B"
  • "test A.aspx?hmm#anchor B" ==> "test%20A.aspx?hmm#anchor B" (note the difference with the previous escape sequence!)

It also has the lovelily specific MSDN documentation "Encodes the path portion of a URL string for reliable HTTP transmission from the Web server to a client." - without actually explaining what it does. You are less likely to shoot yourself in the foot with an Uzi...

In short, stick to Uri.EscapeDataString.

What are pipe and tap methods in Angular tutorial?

You are right, the documentation lacks of those methods. However when I dug into rxjs repository, I found nice comments about tap (too long to paste here) and pipe operators:

  /**
   * Used to stitch together functional operators into a chain.
   * @method pipe
   * @return {Observable} the Observable result of all of the operators having
   * been called in the order they were passed in.
   *
   * @example
   *
   * import { map, filter, scan } from 'rxjs/operators';
   *
   * Rx.Observable.interval(1000)
   *   .pipe(
   *     filter(x => x % 2 === 0),
   *     map(x => x + x),
   *     scan((acc, x) => acc + x)
   *   )
   *   .subscribe(x => console.log(x))
   */

In brief:

Pipe: Used to stitch together functional operators into a chain. Before we could just do observable.filter().map().scan(), but since every RxJS operator is a standalone function rather than an Observable's method, we need pipe() to make a chain of those operators (see example above).

Tap: Can perform side effects with observed data but does not modify the stream in any way. Formerly called do(). You can think of it as if observable was an array over time, then tap() would be an equivalent to Array.forEach().

Highcharts - how to have a chart with dynamic height?

I had the same problem and I fixed it with:

<div id="container" style="width: 100%; height: 100%; position:absolute"></div>

The chart fits perfect to the browser even if I resize it. You can change the percentage according to your needs.

Passing string to a function in C - with or without pointers?

The accepted convention of passing C-strings to functions is to use a pointer:

void function(char* name)

When the function modifies the string you should also pass in the length:

void function(char* name, size_t name_length)

Your first example: 

char *functionname(char *string name[256])

passes an array of pointers to strings which is not what you need at all.

Your second example:

char functionname(char string[256])

passes an array of chars. The size of the array here doesn't matter and the parameter will decay to a pointer anyway, so this is equivalent to:

char functionname(char *string)

See also this question for more details on array arguments in C.

How to compare binary files to check if they are the same?

For finding flash memory defects, I had to write this script which shows all 1K blocks which contain differences (not only the first one as cmp -b does)

#!/bin/sh

f1=testinput.dat
f2=testoutput.dat

size=$(stat -c%s $f1)
i=0
while [ $i -lt $size ]; do
  if ! r="`cmp -n 1024 -i $i -b $f1 $f2`"; then
    printf "%8x: %s\n" $i "$r"
  fi
  i=$(expr $i + 1024)
done

Output:

   2d400: testinput.dat testoutput.dat differ: byte 3, line 1 is 200 M-^@ 240 M- 
   2dc00: testinput.dat testoutput.dat differ: byte 8, line 1 is 327 M-W 127 W
   4d000: testinput.dat testoutput.dat differ: byte 37, line 1 is 270 M-8 260 M-0
   4d400: testinput.dat testoutput.dat differ: byte 19, line 1 is  46 &  44 $

Disclaimer: I hacked the script in 5 min. It doesn't support command line arguments nor does it support spaces in file names

Correct way to quit a Qt program?

if you need to close your application from main() you can use this code

int main(int argc, char *argv[]){
QApplication app(argc, argv);
...
if(!QSslSocket::supportsSsl()) return app.exit(0);
...
return app.exec();
}

The program will terminated if OpenSSL is not installed

How to remove special characters from a string?

That depends on what you define as special characters, but try replaceAll(...):

String result = yourString.replaceAll("[-+.^:,]","");

Note that the ^ character must not be the first one in the list, since you'd then either have to escape it or it would mean "any but these characters".

Another note: the - character needs to be the first or last one on the list, otherwise you'd have to escape it or it would define a range ( e.g. :-, would mean "all characters in the range : to ,).

So, in order to keep consistency and not depend on character positioning, you might want to escape all those characters that have a special meaning in regular expressions (the following list is not complete, so be aware of other characters like (, {, $ etc.):

String result = yourString.replaceAll("[\\-\\+\\.\\^:,]","");


If you want to get rid of all punctuation and symbols, try this regex: \p{P}\p{S} (keep in mind that in Java strings you'd have to escape back slashes: "\\p{P}\\p{S}").

A third way could be something like this, if you can exactly define what should be left in your string:

String  result = yourString.replaceAll("[^\\w\\s]","");

This means: replace everything that is not a word character (a-z in any case, 0-9 or _) or whitespace.

Edit: please note that there are a couple of other patterns that might prove helpful. However, I can't explain them all, so have a look at the reference section of regular-expressions.info.

Here's less restrictive alternative to the "define allowed characters" approach, as suggested by Ray:

String  result = yourString.replaceAll("[^\\p{L}\\p{Z}]","");

The regex matches everything that is not a letter in any language and not a separator (whitespace, linebreak etc.). Note that you can't use [\P{L}\P{Z}] (upper case P means not having that property), since that would mean "everything that is not a letter or not whitespace", which almost matches everything, since letters are not whitespace and vice versa.

Additional information on Unicode

Some unicode characters seem to cause problems due to different possible ways to encode them (as a single code point or a combination of code points). Please refer to regular-expressions.info for more information.

Converting BigDecimal to Integer

TL;DR

Use one of these for universal conversion needs

//Java 7 or below
bigDecimal.setScale(0, RoundingMode.DOWN).intValueExact()
//Java 8    
bigDecimal.toBigInteger().intValueExact()

Reasoning

The answer depends on what the requirements are and how you answer these question.

  • Will the BigDecimal potentially have a non-zero fractional part?
  • Will the BigDecimal potentially not fit into the Integer range?
  • Would you like non-zero fractional parts rounded or truncated?
  • How would you like non-zero fractional parts rounded?

If you answered no to the first 2 questions, you could just use BigDecimal.intValueExact() as others have suggested and let it blow up when something unexpected happens.

If you are not absolutely 100% confident about question number 2, then intValue() is always the wrong answer.

Making it better

Let's use the following assumptions based on the other answers.

  • We are okay with losing precision and truncating the value because that's what intValueExact() and auto-boxing do
  • We want an exception thrown when the BigDecimal is larger than the Integer range because anything else would be crazy unless you have a very specific need for the wrap around that happens when you drop the high-order bits.

Given those params, intValueExact() throws an exception when we don't want it to if our fractional part is non-zero. On the other hand, intValue() doesn't throw an exception when it should if our BigDecimal is too large.

To get the best of both worlds, round off the BigDecimal first, then convert. This also has the benefit of giving you more control over the rounding process.

Spock Groovy Test

void 'test BigDecimal rounding'() {
    given:
    BigDecimal decimal = new BigDecimal(Integer.MAX_VALUE - 1.99)
    BigDecimal hugeDecimal = new BigDecimal(Integer.MAX_VALUE + 1.99)
    BigDecimal reallyHuge = new BigDecimal("10000000000000000000000000000000000000000000000")
    String decimalAsBigIntString = decimal.toBigInteger().toString()
    String hugeDecimalAsBigIntString = hugeDecimal.toBigInteger().toString()
    String reallyHugeAsBigIntString = reallyHuge.toBigInteger().toString()

    expect: 'decimals that can be truncated within Integer range to do so without exception'
    //GOOD: Truncates without exception
    '' + decimal.intValue() == decimalAsBigIntString
    //BAD: Throws ArithmeticException 'Non-zero decimal digits' because we lose information
    // decimal.intValueExact() == decimalAsBigIntString
    //GOOD: Truncates without exception
    '' + decimal.setScale(0, RoundingMode.DOWN).intValueExact() == decimalAsBigIntString

    and: 'truncated decimal that cannot be truncated within Integer range throw conversionOverflow exception'
    //BAD: hugeDecimal.intValue() is -2147483648 instead of 2147483648
    //'' + hugeDecimal.intValue() == hugeDecimalAsBigIntString
    //BAD: Throws ArithmeticException 'Non-zero decimal digits' because we lose information
    //'' + hugeDecimal.intValueExact() == hugeDecimalAsBigIntString
    //GOOD: Throws conversionOverflow ArithmeticException because to large
    //'' + hugeDecimal.setScale(0, RoundingMode.DOWN).intValueExact() == hugeDecimalAsBigIntString

    and: 'truncated decimal that cannot be truncated within Integer range throw conversionOverflow exception'
    //BAD: hugeDecimal.intValue() is 0
    //'' + reallyHuge.intValue() == reallyHugeAsBigIntString
    //GOOD: Throws conversionOverflow ArithmeticException because to large
    //'' + reallyHuge.intValueExact() == reallyHugeAsBigIntString
    //GOOD: Throws conversionOverflow ArithmeticException because to large
    //'' + reallyHuge.setScale(0, RoundingMode.DOWN).intValueExact() == reallyHugeAsBigIntString

    and: 'if using Java 8, BigInteger has intValueExact() just like BigDecimal'
    //decimal.toBigInteger().intValueExact() == decimal.setScale(0, RoundingMode.DOWN).intValueExact()
}

Node.js connect only works on localhost

Binding to 0.0.0.0 is half the battle. There is an ip firewall (different from the one in system preferences) that blocks TCP ports. Hence port must be unblocked there as well by doing:

sudo ipfw add <PORT NUMBER> allow tcp from any to any

How to count number of records per day?

 
SELECT count(*), dateadded FROM Responses
WHERE DateAdded >=dateadd(day,datediff(day,0,GetDate())- 7,0)
group by dateadded

RETURN

This will give you a count of records for each dateadded value. Don't make the mistake of adding more columns to the select, expecting to get just one count per day. The group by clause will give you a row for every unique instance of the columns listed.

Blocking device rotation on mobile web pages

_x000D_
_x000D_ 
#rotate-device {_x000D_
    width: 100%;_x000D_
    height: 100%;_x000D_
    position: fixed;_x000D_
    z-index: 9999;_x000D_
    top: 0;_x000D_
    left: 0;_x000D_
    background-color: #000;_x000D_
    background-image: url(/path to img/rotate.png);_x000D_
    background-size: 100px 100px;_x000D_
    background-position: center;_x000D_
    background-repeat: no-repeat;_x000D_
    display: none;_x000D_
}_x000D_
_x000D_
@media only screen and (max-device-width: 667px) and (min-device-width: 320px) and (orientation: landscape){_x000D_
 #rotate-device {_x000D_
  display: block;_x000D_
 }_x000D_
}
_x000D_ 
<div id="rotate-device"></div>
_x000D_
_x000D_
_x000D_

Microsoft Web API: How do you do a Server.MapPath?

As an aside to those that stumble along across this, one nice way to run test level on using the HostingEnvironment call, is if accessing say a UNC share: \example\ that is mapped to ~/example/ you could execute this to get around IIS-Express issues: 

#if DEBUG
    var fs = new FileStream(@"\\example\file",FileMode.Open, FileAccess.Read);
#else
    var fs = new FileStream(HostingEnvironment.MapPath("~/example/file"), FileMode.Open, FileAccess.Read);
#endif

I find that helpful in case you have rights to locally test on a file, but need the env mapping once in production.

How to limit the maximum value of a numeric field in a Django model?

I had this very same problem; here was my solution:

SCORE_CHOICES = zip( range(1,n), range(1,n) )
score = models.IntegerField(choices=SCORE_CHOICES, blank=True)

How do I 'git diff' on a certain directory?

If you're comparing different branches, you need to use -- to separate a Git revision from a filesystem path. For example, with two local branches, master and bryan-working:

$ git diff master -- AFolderOfCode/ bryan-working -- AFolderOfCode/

Or from a local branch to a remote:

$ git diff master -- AFolderOfCode/ origin/master -- AFolderOfCode/

what is reverse() in Django

reverse() | Django documentation

Let's suppose that in your urls.py you have defined this:

url(r'^foo$', some_view, name='url_name'),

In a template you can then refer to this url as:

<!-- django <= 1.4 -->
<a href="{% url url_name %}">link which calls some_view</a>

<!-- django >= 1.5 or with {% load url from future %} in your template -->
<a href="{% url 'url_name' %}">link which calls some_view</a>

This will be rendered as:

<a href="/foo/">link which calls some_view</a>

Now say you want to do something similar in your views.py - e.g. you are handling some other url (not /foo/) in some other view (not some_view) and you want to redirect the user to /foo/ (often the case on successful form submission).

You could just do:

return HttpResponseRedirect('/foo/')

But what if you want to change the url in future? You'd have to update your urls.py and all references to it in your code. This violates DRY (Don't Repeat Yourself), the whole idea of editing one place only, which is something to strive for.

Instead, you can say:

from django.urls import reverse
return HttpResponseRedirect(reverse('url_name'))

This looks through all urls defined in your project for the url defined with the name url_name and returns the actual url /foo/.

This means that you refer to the url only by its name attribute - if you want to change the url itself or the view it refers to you can do this by editing one place only - urls.py.

How to keep form values after post

If you are looking to just repopulate the fields with the values that were posted in them, then just echo the post value back into the field, like so:

<input type="text" name="myField1" value="<?php echo isset($_POST['myField1']) ? $_POST['myField1'] : '' ?>" />

Can a table have two foreign keys?

Yes, MySQL allows this. You can have multiple foreign keys on the same table.

Get more details here FOREIGN KEY Constraints

How to find a user's home directory on linux or unix?

Can you parse /etc/passwd?

e.g.:

 cat /etc/passwd | awk -F: '{printf "User %s Home %s\n",  $1, $6}'

Formatting html email for Outlook

I used VML(Vector Markup Language) based formatting in my email template. In VML Based you have write your code within comment I took help from this site.

https://litmus.com/blog/a-guide-to-bulletproof-buttons-in-email-design#supporttable

Is there a constraint that restricts my generic method to numeric types?

If all you want is use one numeric type, you could consider creating something similar to an alias in C++ with using.

So instead of having the very generic

T ComputeSomething<T>(T value1, T value2) where T : INumeric { ... }

you could have

using MyNumType = System.Double;
T ComputeSomething<MyNumType>(MyNumType value1, MyNumType value2) { ... }

That might allow you to easily go from double to int or others if needed, but you wouldn't be able to use ComputeSomething with double and int in the same program.

But why not replace all double to int then? Because your method may want to use a double whether the input is double or int. The alias allows you to know exactly which variable uses the dynamic type.

Python math module

In

from math import sqrt

Using sqrt(4) works perfectly well. You need to only use math.sqrt(4) when you just use "import math".

How to revert the last migration?

You can revert by migrating to the previous migration.

For example, if your last two migrations are:

  • 0010_previous_migration
  • 0011_migration_to_revert

Then you would do:

./manage.py migrate my_app 0010_previous_migration

You can then delete migration 0011_migration_to_revert.

If you're using Django 1.8+, you can show the names of all the migrations with

./manage.py showmigrations my_app

To reverse all migrations for an app, you can run:

./manage.py migrate my_app zero

How to find out whether a file is at its `eof`?

The Python read functions will return an empty string if they reach EOF

java.net.UnknownHostException: Unable to resolve host "<url>": No address associated with hostname and End of input at character 0 of

I encountered this error when running my Android app on my home WiFi, then trying to run it on different WiFi without closing my simulator.

Simply closing the simulator and re-launching the app worked for me!