Programs & Examples On #Dedicated hosting

AppSettings get value from .config file

  1. Open "Properties" on your project
  2. Go to "Settings" Tab
  3. Add "Name" and "Value"


        <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup ..." ... >
          <section name="XX....Properties.Settings" type="System.Configuration.ClientSettingsSection ..." ... />
          <setting name="name" serializeAs="String">
          <setting name="name2" serializeAs="String">

To get a value




How can I disable the bootstrap hover color for links?

a {background-color:transparent !important;}

How to create a zip archive with PowerShell?

In case you have WinRAR installed:

function ZipUsingRar([String] $directory, [String] $zipFileName)
  Write-Output "Performing operation ""Zip File"" on Target ""Item: $directory Destination:"
  Write-Output ($zipFileName + """")
  $pathToWinRar = "c:\Program Files\WinRAR\WinRar.exe";
  [Array]$arguments = "a", "-afzip", "-df", "-ep1", "$zipFileName", "$directory";
  & $pathToWinRar $arguments;

The meaning of the arguments: afzip creates zip archive, df deletes files, ep1 does not create full directory path within archive

How can I check if character in a string is a letter? (Python)

You can use str.isalpha().

For example:

s = 'a123b'

for char in s:
    print(char, char.isalpha())


a True
1 False
2 False
3 False
b True

Save attachments to a folder and rename them

I actually had solved this not long after posting but failed to post my solution. I honestly don't remember it. But, I had to re-visit the task when I was given a new project that faced the same challenge.

I used the ReceivedTime property of Outlook.MailItem to get the time-stamp, I was able to use this as a unique identifier for each file so they do not override one another.

Public Sub saveAttachtoDisk(itm As Outlook.MailItem)
    Dim objAtt As Outlook.Attachment
    Dim saveFolder As String
        saveFolder = "C:\PathToDirectory\"
    Dim dateFormat As String
        dateFormat = Format(itm.ReceivedTime, "yyyy-mm-dd Hmm ")
    For Each objAtt In itm.Attachments
        objAtt.SaveAsFile saveFolder & "\" & dateFormat & objAtt.DisplayName
End Sub

Thanks a ton for the other solutions, many of them go above an beyond :)

git - Your branch is ahead of 'origin/master' by 1 commit

If you just want to throw away the changes and revert to the last commit (the one you wanted to share):

git reset --hard HEAD~

You may want to check to make absolutely sure you want this (git log), because you'll loose all changes.

A safer alternative is to run

git reset --soft HEAD~ # reset to the last commit
git stash              # stash all the changes in the working tree 
git push               # push changes 
git stash pop          # get your changes back 

How do I convert a javascript object array to a string array of the object attribute I want?

Use the map() function native on JavaScript arrays:

var yourArray = [ {

var newArray = function( el ){ 

C# 'or' operator?

if (ActionsLogWriter.Close || ErrorDumpWriter.Close == true)
{    // Do stuff here

PHP regular expression - filter number only

Another way to get only the numbers in a regex string is as shown below:

$output = preg_replace("/\D+/", "", $input);

Logging levels - Logback - rule-of-thumb to assign log levels

I mostly build large scale, high availability type systems, so my answer is biased towards looking at it from a production support standpoint; that said, we assign roughly as follows:

  • error: the system is in distress, customers are probably being affected (or will soon be) and the fix probably requires human intervention. The "2AM rule" applies here- if you're on call, do you want to be woken up at 2AM if this condition happens? If yes, then log it as "error".

  • warn: an unexpected technical or business event happened, customers may be affected, but probably no immediate human intervention is required. On call people won't be called immediately, but support personnel will want to review these issues asap to understand what the impact is. Basically any issue that needs to be tracked but may not require immediate intervention.

  • info: things we want to see at high volume in case we need to forensically analyze an issue. System lifecycle events (system start, stop) go here. "Session" lifecycle events (login, logout, etc.) go here. Significant boundary events should be considered as well (e.g. database calls, remote API calls). Typical business exceptions can go here (e.g. login failed due to bad credentials). Any other event you think you'll need to see in production at high volume goes here.

  • debug: just about everything that doesn't make the "info" cut... any message that is helpful in tracking the flow through the system and isolating issues, especially during the development and QA phases. We use "debug" level logs for entry/exit of most non-trivial methods and marking interesting events and decision points inside methods.

  • trace: we don't use this often, but this would be for extremely detailed and potentially high volume logs that you don't typically want enabled even during normal development. Examples include dumping a full object hierarchy, logging some state during every iteration of a large loop, etc.

As or more important than choosing the right log levels is ensuring that the logs are meaningful and have the needed context. For example, you'll almost always want to include the thread ID in the logs so you can follow a single thread if needed. You may also want to employ a mechanism to associate business info (e.g. user ID) to the thread so it gets logged as well. In your log message, you'll want to include enough info to ensure the message can be actionable. A log like " FileNotFound exception caught" is not very helpful. A better message is "FileNotFound exception caught while attempting to open config file: /usr/local/app/somefile.txt. userId=12344."

There are also a number of good logging guides out there... for example, here's an edited snippet from JCL (Jakarta Commons Logging):

  • error - Other runtime errors or unexpected conditions. Expect these to be immediately visible on a status console.
  • warn - Use of deprecated APIs, poor use of API, 'almost' errors, other runtime situations that are undesirable or unexpected, but not necessarily "wrong". Expect these to be immediately visible on a status console.
  • info - Interesting runtime events (startup/shutdown). Expect these to be immediately visible on a console, so be conservative and keep to a minimum.
  • debug - detailed information on the flow through the system. Expect these to be written to logs only.
  • trace - more detailed information. Expect these to be written to logs only.

Get column from a two dimensional array

You can use the following array methods to obtain a column from a 2D array:

const array_column = (array, column) => => e[column]);


const array_column = (array, column) => array.reduce((a, c) => {
  return a;
}, []);


const array_column = (array, column) => {
  const result = [];

  array.forEach(e => {

  return result;

If your 2D array is a square (the same number of columns for each row), you can use the following method:

Array.prototype.flat() / .filter()

const array_column = (array, column) => array.flat().filter((e, i) => i % array.length === column);

How to draw rounded rectangle in Android UI?

<shape xmlns:android=""
    <solid android:color="@color/colorAccent" /> 
      android:topRightRadius="500dp" />

Now, in which element you want to use this shape just add: android:background="@drawable/custom_round_ui_shape"

Create a new XML in drawable named "custom_round_ui_shape"

How do I delete an item or object from an array using ng-click?

I usually write in such style :

<a class="btn" ng-click="remove($index)">Delete</a>

$scope.remove = function(index){
  $scope.[yourArray].splice(index, 1)

Hope this will help You have to use a dot(.) between $scope and [yourArray]

Basic calculator in Java

CompareStrings with equals(..) not with ==

if (operation.equals("+")
    System.out.println("your answer is" + (num1 + num2));
if (operation.equals("-"))
    System.out.println("your answer is" + (num1 - num2));
if (operation.equals("/"))
    System.out.println("your answer is" + (num1 / num2));
if (operation .equals( "*"))
    System.out.println("your answer is" + (num1 * num2));

And the ; after the conditions was an empty statement so the conditon had no effect at all.

If you use java 7 you can also replace the if statements with a switch.
In java <7 you can test, if operation has length 1 and than make a switch for the char [switch (operation.charAt(0))]

How to set ObjectId as a data type in mongoose

My solution on using ObjectId

// usermodel.js

const mongoose = require('mongoose')
const Schema = mongoose.Schema
const ObjectId = Schema.Types.ObjectId

let UserSchema = new Schema({
   username: {
     type: String
   events: [{
     type: ObjectId,
     ref: 'Event' // Reference to some EventSchema

UserSchema.set('autoIndex', true)

module.exports = mongoose.model('User', UserSchema)

Using mongoose's populate method

// controller.js

const mongoose = require('mongoose')
const User = require('./usermodel.js')

let query = User.findOne({ name: "Person" })

query.exec((err, user) => {
  if (err) {
  } = events
  // is now an array of events

Alternative to google finance api

I followed the top answer and started looking at yahoo finance. Their API can be accessed a number of different ways, but I found a nice reference for getting stock info as a CSV here:

Using that I wrote this script. I'm not really a ruby guy but this might help you hack something together. I haven't come up with variable names for all the fields yahoo offers yet, so you can fill those in if you need them.

Here's the usage


AllData = loadStockInfo(TICKERS_SP500, allParameters())

SpecificData = loadStockInfo("GOOG,CIK", "ask,dps")

loadStockInfo returns a hash, such that SpecificData["GOOG"]["name"] is "Google Inc."

Finally, the actual code to run that...

require 'net/http'

# Jack Franzen & Garin Bedian
# Based on

$parametersData = Hash[[

    ["symbol", ["s", "Symbol"]],
    ["ask", ["a", "Ask"]],
    ["divYield", ["y", "Dividend Yield"]],
    ["bid", ["b", "Bid"]],
    ["dps", ["d", "Dividend per Share"]],
    #["noname", ["b2", "Ask (Realtime)"]],
    #["noname", ["r1", "Dividend Pay Date"]],
    #["noname", ["b3", "Bid (Realtime)"]],
    #["noname", ["q", "Ex-Dividend Date"]],
    #["noname", ["p", "Previous Close"]],
    #["noname", ["o", "Open"]],
    #["noname", ["c1", "Change"]],
    #["noname", ["d1", "Last Trade Date"]],
    #["noname", ["c", "Change &amp; Percent Change"]],
    #["noname", ["d2", "Trade Date"]],
    #["noname", ["c6", "Change (Realtime)"]],
    #["noname", ["t1", "Last Trade Time"]],
    #["noname", ["k2", "Change Percent (Realtime)"]],
    #["noname", ["p2", "Change in Percent"]],
    #["noname", ["c8", "After Hours Change (Realtime)"]],
    #["noname", ["m5", "Change From 200 Day Moving Average"]],
    #["noname", ["c3", "Commission"]],
    #["noname", ["m6", "Percent Change From 200 Day Moving Average"]],
    #["noname", ["g", "Day’s Low"]],
    #["noname", ["m7", "Change From 50 Day Moving Average"]],
    #["noname", ["h", "Day’s High"]],
    #["noname", ["m8", "Percent Change From 50 Day Moving Average"]],
    #["noname", ["k1", "Last Trade (Realtime) With Time"]],
    #["noname", ["m3", "50 Day Moving Average"]],
    #["noname", ["l", "Last Trade (With Time)"]],
    #["noname", ["m4", "200 Day Moving Average"]],
    #["noname", ["l1", "Last Trade (Price Only)"]],
    #["noname", ["t8", "1 yr Target Price"]],
    #["noname", ["w1", "Day’s Value Change"]],
    #["noname", ["g1", "Holdings Gain Percent"]],
    #["noname", ["w4", "Day’s Value Change (Realtime)"]],
    #["noname", ["g3", "Annualized Gain"]],
    #["noname", ["p1", "Price Paid"]],
    #["noname", ["g4", "Holdings Gain"]],
    #["noname", ["m", "Day’s Range"]],
    #["noname", ["g5", "Holdings Gain Percent (Realtime)"]],
    #["noname", ["m2", "Day’s Range (Realtime)"]],
    #["noname", ["g6", "Holdings Gain (Realtime)"]],
    #["noname", ["k", "52 Week High"]],
    #["noname", ["v", "More Info"]],
    #["noname", ["j", "52 week Low"]],
    #["noname", ["j1", "Market Capitalization"]],
    #["noname", ["j5", "Change From 52 Week Low"]],
    #["noname", ["j3", "Market Cap (Realtime)"]],
    #["noname", ["k4", "Change From 52 week High"]],
    #["noname", ["f6", "Float Shares"]],
    #["noname", ["j6", "Percent Change From 52 week Low"]],
    ["name", ["n", "Company Name"]],
    #["noname", ["k5", "Percent Change From 52 week High"]],
    #["noname", ["n4", "Notes"]],
    #["noname", ["w", "52 week Range"]],
    #["noname", ["s1", "Shares Owned"]],
    #["noname", ["x", "Stock Exchange"]],
    #["noname", ["j2", "Shares Outstanding"]],
    #["noname", ["v", "Volume"]],
    #["noname", ["a5", "Ask Size"]],
    #["noname", ["b6", "Bid Size"]],
    #["noname", ["k3", "Last Trade Size"]],
    #["noname", ["t7", "Ticker Trend"]],
    #["noname", ["a2", "Average Daily Volume"]],
    #["noname", ["t6", "Trade Links"]],
    #["noname", ["i5", "Order Book (Realtime)"]],
    #["noname", ["l2", "High Limit"]],
    #["noname", ["e", "Earnings per Share"]],
    #["noname", ["l3", "Low Limit"]],
    #["noname", ["e7", "EPS Estimate Current Year"]],
    #["noname", ["v1", "Holdings Value"]],
    #["noname", ["e8", "EPS Estimate Next Year"]],
    #["noname", ["v7", "Holdings Value (Realtime)"]],
    #["noname", ["e9", "EPS Estimate Next Quarter"]],
    #["noname", ["s6", "evenue"]],
    #["noname", ["b4", "Book Value"]],
    #["noname", ["j4", "EBITDA"]],
    #["noname", ["p5", "Price / Sales"]],
    #["noname", ["p6", "Price / Book"]],
    #["noname", ["r", "P/E Ratio"]],
    #["noname", ["r2", "P/E Ratio (Realtime)"]],
    #["noname", ["r5", "PEG Ratio"]],
    #["noname", ["r6", "Price / EPS Estimate Current Year"]],
    #["noname", ["r7", "Price / EPS Estimate Next Year"]],
    #["noname", ["s7", "Short Ratio"]


def replaceCommas(data)
    s = ""
    inQuote = false
    data.split("").each do |a|
        if a=='"'
            inQuote = !inQuote
            s += '"'
        elsif !inQuote && a == ","
            s += "#"
            s += a
    return s

def allParameters()
    s = ""
    $parametersData.keys.each do |i|
        s  = s + i + ","
    return s

def prepareParameters(parametersText)
    pt = parametersText.split(",")
    if !pt.include? 'symbol'; pt.push("symbol"); end;
    if !pt.include? 'name'; pt.push("name"); end;
    p = []
    pt.each do |i|
        p.push([i, $parametersData[i][0]])
    return p

def prepareURL(tickers, parameters)
    urlParameters = ""
    parameters.each do |i|
        urlParameters += i[1]
    s = ""
    s = s + "s=" + tickers + "&"
    s = s + "f=" + urlParameters
    return URI(s)

def loadStockInfo(tickers, parametersRaw)
    parameters = prepareParameters(parametersRaw)
    url = prepareURL(tickers, parameters)
    data = Net::HTTP.get(url)
    data = replaceCommas(data)
    h = CSVtoObject(data, parameters)
    logStockObjects(h, true)

#parse csv
def printCodes(substring, length)

    a = data.index(substring)
    b = data.byteslice(a, 10)
    puts "printing codes of string: "
    puts b
    puts b.split('').map(&:ord).to_s

def CSVtoObject(data, parameters)
    rawData = []
    lineBreaks = data.split(10.chr)
    lineBreaks.each_index do |i|

    #puts "Found " + rawData.length.to_s + " Stocks"
    #puts "   w/ " + rawData[0].length.to_s + " Fields"

    h ="MainHash")
    rawData.each_index do |i|
        o ="StockObject"+i.to_s)
        #puts "parsing object" + rawData[i][0]
        rawData[i].each_index do |n|
            #puts "parsing parameter" + n.to_s + " " +parameters[n][0]
            o[ parameters[n][0] ] = rawData[i][n].gsub!(/^\"|\"?$/, '')
        h[o["symbol"]] = o;
    return h

def logStockObjects(h, concise)
    h.keys.each do |i|
        if concise
            puts "(" + h[i]["symbol"] + ")\t\t" + h[i]["name"]
            puts ""
            puts h[i]["name"]
            h[i].keys.each do |p|
                puts "    " + $parametersData[p][1] + " : " + h[i][p].to_s

Do I really need to encode '&' as '&amp;'?

Update (March 2020): The W3C validator no longer complains about escaping URLs.

I was checking why Image URL's need escaping, hence tried it in The explanation is pretty nice. It highlights that even URL's need to be escaped. [PS:I guess it will unescaped when its consumed since URL's need &. Can anyone clarify?]

<img alt="" src="foo?bar=qut&qux=fop" />

An entity reference was found in the document, but there is no reference by that name defined. Often this is caused by misspelling the reference name, unencoded ampersands, or by leaving off the trailing semicolon (;). The most common cause of this error is unencoded ampersands in URLs as described by the WDG in "Ampersands in URLs". Entity references start with an ampersand (&) and end with a semicolon (;). If you want to use a literal ampersand in your document you must encode it as "&" (even inside URLs!). Be careful to end entity references with a semicolon or your entity reference may get interpreted in connection with the following text. Also keep in mind that named entity references are case-sensitive; &Aelig; and æ are different characters. If this error appears in some markup generated by PHP's session handling code, this article has explanations and solutions to your problem.

How to clean up R memory (without the need to restart my PC)?

An example under Linux (Fedora 16) shows that memory is freed when R is closed:

$ free -m                                                                                                                                                                                                                                    
             total       used       free     shared    buffers     cached                                                                                                                                                                    
Mem:          3829       2854        974          0        344       1440                                                                                                                                                                    
-/+ buffers/cache:       1069       2759                                                                                                                                                                                                     
Swap:         4095         85       4010     

2854 megabytes is used. Next I open an R session and create a large matrix of random numbers:

m = matrix(runif(10e7), 10000, 1000)

when the matrix is created, 3714 MB is used:

$ free -m                                                                                                                                                                                                                                    
             total       used       free     shared    buffers     cached                                                                                                                                                                    
Mem:          3829       3714        115          0        344       1442                                                                                                                                                                    
-/+ buffers/cache:       1927       1902                                                                                                                                                                                                     
Swap:         4095         85       4010     

After closing the R session, I nicely get back the memory I used (2856 MB free):

$ free -m                                                                                                                                                                                                                                    
             total       used       free     shared    buffers     cached                                                                                                                                                                    
Mem:          3829       2856        972          0        344       1442                                                                                                                                                                    
-/+ buffers/cache:       1069       2759                                                                                                                                                                                                     
Swap:         4095         85       4010   

Ofcourse you use Windows, but you could repeat this excercise in Windows and report how the available memory develops before and after you create this large dataset in R.

Populating a ComboBox using C#

Define a class

public class Language
     public string Name { get; set; }
     public string Value { get; set; }


//Build a list
var dataSource = new List<Language>();
dataSource.Add(new Language() { Name = "blah", Value = "blah" });
dataSource.Add(new Language() { Name = "blah", Value = "blah" });
dataSource.Add(new Language() { Name = "blah", Value = "blah" });

//Setup data binding
this.comboBox1.DataSource = dataSource;
this.comboBox1.DisplayMember = "Name";
this.comboBox1.ValueMember = "Value";

// make it readonly
this.comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;

How to redirect output to a file and stdout

The command you want is named tee:

foo | tee output.file

For example, if you only care about stdout:

ls -a | tee output.file

If you want to include stderr, do:

program [arguments...] 2>&1 | tee outfile

2>&1 redirects channel 2 (stderr/standard error) into channel 1 (stdout/standard output), such that both is written as stdout. It is also directed to the given output file as of the tee command.

Furthermore, if you want to append to the log file, use tee -a as:

program [arguments...] 2>&1 | tee -a outfile

Easiest way to compare arrays in C#

elementwise compare ? what about

public void Linq78a()
 int[] numbers1 = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 bool bb = numbers.Zip(numbers1, (a, b) => (a == b)).Any(p => !p);
 if (!bb) Console.WriteLine("Lists are equal (bb)");
   else Console.WriteLine("Lists are not equal (bb)");

Replace the (a==b) condition by anything you'd like to compare in a and b.

(this combines two examples from MSDN developer Linq samples)

How does @synchronized lock/unlock in Objective-C?

The Objective-C language level synchronization uses the mutex, just like NSLock does. Semantically there are some small technical differences, but it is basically correct to think of them as two separate interfaces implemented on top of a common (more primitive) entity.

In particular with a NSLock you have an explicit lock whereas with @synchronized you have an implicit lock associated with the object you are using to synchronize. The benefit of the language level locking is the compiler understands it so it can deal with scoping issues, but mechanically they behave basically the same.

You can think of @synchronized as a compiler rewrite:

- (NSString *)myString {
  @synchronized(self) {
    return [[myString retain] autorelease];

is transformed into:

- (NSString *)myString {
  NSString *retval = nil;
  pthread_mutex_t *self_mutex = LOOK_UP_MUTEX(self);
  retval = [[myString retain] autorelease];
  return retval;

That is not exactly correct because the actual transform is more complex and uses recursive locks, but it should get the point across.

git pull from master into the development branch

Situation: Working in my local branch, but I love to keep-up updates in the development branch named dev.

Solution: Usually, I prefer to do :

git fetch
git rebase origin/dev

Haversine Formula in Python (Bearing and Distance between two GPS points)

The bearing calculation is incorrect, you need to swap the inputs to atan2.

    bearing = atan2(sin(long2-long1)*cos(lat2), cos(lat1)*sin(lat2)-sin(lat1)*cos(lat2)*cos(long2-long1))
    bearing = degrees(bearing)
    bearing = (bearing + 360) % 360

This will give you the correct bearing.

Bootstrap: Position of dropdown menu relative to navbar item

Boostrap has a class for that called navbar-right. So your code will look as follows:

<ul class="nav navbar-right">
    <li class="dropdown">
      <a class="dropdown-toggle" href="#" data-toggle="dropdown">Link</a>
      <ul class="dropdown-menu">

Install Application programmatically on Android

The solutions provided to this question are all applicable to targetSdkVersion s of 23 and below. For Android N, i.e. API level 24, and above, however, they do not work and crash with the following Exception:

android.os.FileUriExposedException: file:///storage/emulated/0/... exposed beyond app through Intent.getData()

This is due to the fact that starting from Android 24, the Uri for addressing the downloaded file has changed. For instance, an installation file named appName.apk stored on the primary external filesystem of the app with package name com.example.test would be as


for API 23 and below, whereas something like


for API 24 and above.

More details on this can be found here and I am not going to go through it.

To answer the question for targetSdkVersion of 24 and above, one has to follow these steps: Add the following to the AndroidManifest.xml:


2. Add the following paths.xml file to the xml folder on res in src, main:

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="">

The pathName is that shown in the exemplary content uri example above and pathValue is the actual path on the system. It would be a good idea to put a "." (without quotes) for pathValue in the above if you do not want to add any extra subdirectory.

  1. Write the following code to install the apk with the name appName.apk on the primary external filesystem:

    File directory = context.getExternalFilesDir(null);
    File file = new File(directory, fileName);
    Uri fileUri = Uri.fromFile(file);
    if (Build.VERSION.SDK_INT >= 24) {
        fileUri = FileProvider.getUriForFile(context, context.getPackageName(),
    Intent intent = new Intent(Intent.ACTION_VIEW, fileUri);
    intent.putExtra(Intent.EXTRA_NOT_UNKNOWN_SOURCE, true);
    intent.setDataAndType(fileUri, "application/" + ".package-archive");

No permission is also necessary when writing to your own app's private directory on the external filesystem.

I have written an AutoUpdate library here in which I have used the above.

Pandas unstack problems: ValueError: Index contains duplicate entries, cannot reshape

Here's an example DataFrame which show this, it has duplicate values with the same index. The question is, do you want to aggregate these or keep them as multiple rows?

In [11]: df
   0  1  2      3
0  1  2  a  16.86
1  1  2  a  17.18
2  1  4  a  17.03
3  2  5  b  17.28

In [12]: df.pivot_table(values=3, index=[0, 1], columns=2, aggfunc='mean')  # desired?
2        a      b
0 1
1 2  17.02    NaN
  4  17.03    NaN
2 5    NaN  17.28

In [13]: df1 = df.set_index([0, 1, 2])

In [14]: df1
0 1 2
1 2 a  16.86
    a  17.18
  4 a  17.03
2 5 b  17.28

In [15]: df1.unstack(2)
ValueError: Index contains duplicate entries, cannot reshape

One solution is to reset_index (and get back to df) and use pivot_table.

In [16]: df1.reset_index().pivot_table(values=3, index=[0, 1], columns=2, aggfunc='mean')
2        a      b
0 1
1 2  17.02    NaN
  4  17.03    NaN
2 5    NaN  17.28

Another option (if you don't want to aggregate) is to append a dummy level, unstack it, then drop the dummy level...

Add Foreign Key relationship between two Databases

In my experience, the best way to handle this when the primary authoritative source of information for two tables which are related has to be in two separate databases is to sync a copy of the table from the primary location to the secondary location (using T-SQL or SSIS with appropriate error checking - you cannot truncate and repopulate a table while it has a foreign key reference, so there are a few ways to skin the cat on the table updating).

Then add a traditional FK relationship in the second location to the table which is effectively a read-only copy.

You can use a trigger or scheduled job in the primary location to keep the copy updated.

MySQL integer field is returned as string in PHP

When you select data from a MySQL database using PHP the datatype will always be converted to a string. You can convert it back to an integer using the following code:

$id = (int) $row['userid'];

Or by using the function intval():

$id = intval($row['userid']);

C# using Sendkey function to send a key to another application

If notepad is already started, you should write:

// import the function in your class
[DllImport ("User32.dll")]
static extern int SetForegroundWindow(IntPtr point);


Process p = Process.GetProcessesByName("notepad").FirstOrDefault();
if (p != null)
    IntPtr h = p.MainWindowHandle;

GetProcessesByName returns an array of processes, so you should get the first one (or find the one you want).

If you want to start notepad and send the key, you should write:

Process p = Process.Start("notepad.exe");
IntPtr h = p.MainWindowHandle;

The only situation in which the code may not work is when notepad is started as Administrator and your application is not.

Stop Visual Studio from launching a new browser window when starting debug?

In Visual Studio 2019, I resolved the same issue as below:

Go to your Visual Studio options Tools >>> Options >>> Project and Solutions >>> Web Projects then finally untick option >>> Stop debugger browser window is closed, close browser when debugging stops

Step 1:

enter image description here

Step 2: untick option >>> Stop debugger browser window is closed, close browser when debugging stops

enter image description here

Step 3:

Then finally click on >>> OK button, these are all the steps to resolve the issue.

Way to get all alphabetic chars in an array in PHP?

To get both upper and lower case merge the two ranges:

$alphas = array_merge(range('A', 'Z'), range('a', 'z'));

ASP.NET Core Dependency Injection error: Unable to resolve service for type while attempting to activate

Add services.AddSingleton(); in your ConfigureServices method of Startup.cs file of your project.

public void ConfigureServices(IServiceCollection services)
        // To register interface with its concrite type
        services.AddSingleton<IEmployee, EmployeesMockup>();

For More details please visit this URL :

for All methods (i.e. AddSingleton vs AddScoped vs AddTransient) Please visit this URL:

How do I raise the same Exception with a custom message in Python?

This only works with Python 3. You can modify the exception's original arguments and add your own arguments.

An exception remembers the args it was created with. I presume this is so that you can modify the exception.

In the function reraise we prepend the exception's original arguments with any new arguments that we want (like a message). Finally we re-raise the exception while preserving the trace-back history.

def reraise(e, *args):
  '''re-raise an exception with extra arguments
  :param e: The exception to reraise
  :param args: Extra args to add to the exception

  # e.args is a tuple of arguments that the exception with instantiated with.
  e.args = args + e.args

  # Recreate the expection and preserve the traceback info so thta we can see 
  # where this exception originated.
  raise e.with_traceback(e.__traceback__)   

def bad():
  raise ValueError('bad')

def very():
  except Exception as e:
    reraise(e, 'very')

def very_very():
  except Exception as e:
    reraise(e, 'very')



Traceback (most recent call last):
  File "", line 35, in <module>
  File "", line 30, in very_very
    reraise(e, 'very')
  File "", line 15, in reraise
    raise e.with_traceback(e.__traceback__)
  File "", line 28, in very_very
  File "", line 24, in very
    reraise(e, 'very')
  File "", line 15, in reraise
    raise e.with_traceback(e.__traceback__)
  File "", line 22, in very
  File "", line 18, in bad
    raise ValueError('bad')
ValueError: ('very', 'very', 'bad')

Why doesn't TFS get latest get the latest?

Go with right click: Advanced > Get Specific Version. Select "Letest Version" and now, important, mark two checks: enter image description here

The checks are:
Overwrite writeable files that are not checked

Overwrite all files even if the local version matches the specified version

Making an svg image object clickable with onclick, avoiding absolute positioning

Click on SVG's <g> element in <object> with click event. Works 100%. Take a look on the nested javascript in <svg>. Don't forget to insert window.parent.location.href= if you want to redirect the parent page.

What does 'synchronized' mean?

Synchronized simply means that multiple threads if associated with single object can prevent dirty read and write if synchronized block is used on particular object. To give you more clarity , lets take an example :

class MyRunnable implements Runnable {
    int var = 10;
    public void run() {

    public void call() {
        synchronized (this) {
            for (int i = 0; i < 4; i++) {
                System.out.println("Current Thread " + Thread.currentThread().getName() + " var value "+var);

public class MutlipleThreadsRunnable {
    public static void main(String[] args) {
        MyRunnable runnable1 = new MyRunnable();
        MyRunnable runnable2 = new MyRunnable();
        Thread t1 = new Thread(runnable1);
        t1.setName("Thread -1");
        Thread t2 = new Thread(runnable2);
        t2.setName("Thread -2");
        Thread t3 = new Thread(runnable1);
        t3.setName("Thread -3");

We've created two MyRunnable class objects , runnable1 being shared with thread 1 and thread 3 & runnable2 being shared with thread 2 only. Now when t1 and t3 starts without synchronized being used , PFB output which suggest that both threads 1 and 3 simultaneously affecting var value where for thread 2 , var has its own memory.

Without Synchronized keyword

    Current Thread Thread -1 var value 11
    Current Thread Thread -2 var value 11
    Current Thread Thread -2 var value 12
    Current Thread Thread -2 var value 13
    Current Thread Thread -2 var value 14
    Current Thread Thread -1 var value 12
    Current Thread Thread -3 var value 13
    Current Thread Thread -3 var value 15
    Current Thread Thread -1 var value 14
    Current Thread Thread -1 var value 17
    Current Thread Thread -3 var value 16
    Current Thread Thread -3 var value 18

Using Synchronzied, thread 3 waiting for thread 1 to complete in all scenarios. There are two locks acquired , one on runnable1 shared by thread 1 and thread 3 and another on runnable2 shared by thread 2 only.

Current Thread Thread -1 var value 11
Current Thread Thread -2 var value 11
Current Thread Thread -1 var value 12
Current Thread Thread -2 var value 12
Current Thread Thread -1 var value 13
Current Thread Thread -2 var value 13
Current Thread Thread -1 var value 14
Current Thread Thread -2 var value 14
Current Thread Thread -3 var value 15
Current Thread Thread -3 var value 16
Current Thread Thread -3 var value 17
Current Thread Thread -3 var value 18

Open a new tab on button click in AngularJS

You can do this all within your controller by using the $window service here. $window is a wrapper around the global browser object window.

To make this work inject $window into you controller as follows

.controller('exampleCtrl', ['$scope', '$window',
    function($scope, $window) {
        $scope.redirectToGoogle = function(){
            $'', '_blank');

this works well when redirecting to dynamic routes

Delete all the records

I can see the that the others answers shown above are right, but I'll make your life easy.

I even created an example for you. I added some rows and want delete them.

You have to right click on the table and as shown in the figure Script Table a> Delete to> New query Editor widows:

enter image description here

Then another window will open with a script. Delete the line of "where", because you want to delete all rows. Then click Execute.

enter image description here

To make sure you did it right right click over the table and click in "Select Top 1000 rows". Then you can see that the query is empty.

wget can't download - 404 error

You will also get a 404 error if you are using ipv6 and the server only accepts ipv4.

To use ipv4, make a request adding -4:

wget -4

writing a batch file that opens a chrome URL

"c:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --app=""

"c:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --app=""

How to find the Center Coordinate of Rectangle?

Center x = x + 1/2 of width

Center y = y + 1/2 of height 

If you know the width and height already then you only need one set of coordinates.

How to change background color in the Notepad++ text editor?

There seems to have been an update some time in the past 3 years which changes the location of where to place themes in order to get them working.

Previosuly, themes were located in the Notepad++ installation folder. Now they are located in AppData:


My answer is an update to @Amit-IO's answer about manually copying the themes.

  1. In Explorer, browse to: %AppData%\Notepad++.
  2. If a folder called themes does not exist, create it.
  3. Download your favourite theme from wherever (see Amit-IO's answer for a good list) and save it to %AppData%\Notepad++\themes.
  4. Restart Notepad++ and then use Settings -> Style Configurator. The new theme(s) will appear in the list.

How do I get a consistent byte representation of strings in C# without manually specifying an encoding?

It depends on the encoding of your string (ASCII, UTF-8, ...).

For example:

byte[] b1 = System.Text.Encoding.UTF8.GetBytes (myString);
byte[] b2 = System.Text.Encoding.ASCII.GetBytes (myString);

A small sample why encoding matters:

string pi = "\u03a0";
byte[] ascii = System.Text.Encoding.ASCII.GetBytes (pi);
byte[] utf8 = System.Text.Encoding.UTF8.GetBytes (pi);

Console.WriteLine (ascii.Length); //Will print 1
Console.WriteLine (utf8.Length); //Will print 2
Console.WriteLine (System.Text.Encoding.ASCII.GetString (ascii)); //Will print '?'

ASCII simply isn't equipped to deal with special characters.

Internally, the .NET framework uses UTF-16 to represent strings, so if you simply want to get the exact bytes that .NET uses, use System.Text.Encoding.Unicode.GetBytes (...).

See Character Encoding in the .NET Framework (MSDN) for more information.

How to put labels over geom_bar for each bar in R with ggplot2

Try this:

ggplot(data=dat, aes(x=Types, y=Number, fill=sample)) + 
     geom_bar(position = 'dodge', stat='identity') +
     geom_text(aes(label=Number), position=position_dodge(width=0.9), vjust=-0.25)

ggplot output

error opening trace file: No such file or directory (2)

Write all your code below this 2 lines:-


It worked for me without re-installing again.

How to properly add cross-site request forgery (CSRF) token using PHP

CSRF protection





<input type="hidden" name="token" value="{{ form_token() }}" />


<meta name="csrf-token" content="{{ csrf_token() }}">


    headers: {
        'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')


use Illuminate\Http\Request;

Route::get('/token', function (Request $request) {
    $token = $request->session()->token();

    $token = csrf_token();

    // ...




namespace App\Http\Middleware;

use Illuminate\Foundation\Http\Middleware\VerifyCsrfToken as Middleware;

class VerifyCsrfToken extends Middleware
     * The URIs that should be excluded from CSRF verification.
     * @var array
    protected $except = [

PostgreSQL: role is not permitted to log in

try to run

sudo su - postgres
ALTER ROLE 'dbname'

How to use RANK() in SQL Server

You have to use DENSE_RANK rather than RANK. The only difference is that it doesn't leave gaps. You also shouldn't partition by contender_num, otherwise you're ranking each contender in a separate group, so each is 1st-ranked in their segregated groups!

SELECT contendernum,totals, DENSE_RANK() OVER (ORDER BY totals desc) AS xRank FROM
SELECT ContenderNum ,SUM(Criteria1+Criteria2+Criteria3+Criteria4) AS totals
FROM dbo.Cat1GroupImpersonation
 GROUP BY ContenderNum
) AS a
order by contendernum

A hint for using StackOverflow, please post DDL and sample data so people can help you using less of their own time!

create table Cat1GroupImpersonation (
contendernum int,
criteria1 int,
criteria2 int,
criteria3 int,
criteria4 int);

insert Cat1GroupImpersonation select
1,196,0,0,0 union all select
2,181,0,0,0 union all select
3,192,0,0,0 union all select
4,181,0,0,0 union all select

How can I wrap or break long text/word in a fixed width span?

You can use the CSS property word-wrap:break-word;, which will break words if they are too long for your span width.

span { _x000D_

How to reload the current state?

I had multiple nested views and the goal was to reload only one with content. I tried different approaches but the only thing that worked for me is:

//to reload
$stateParams.reload = !$stateParams.reload; //flip value of reload param
$state.go($state.current, $stateParams);

//state config
  .state('app.dashboard', {
    url: '/',
    templateUrl: 'app/components/dashboard/dashboard.tmpl.html',
    controller: 'DashboardController',
    controllerAs: 'vm',
    params: {reload: false} //add reload param to a view you want to reload

In this case only needed view would be reloaded and caching would still work.

What does -> mean in C++?

It's to access a member function or member variable of an object through a pointer, as opposed to a regular variable or reference.

For example: with a regular variable or reference, you use the . operator to access member functions or member variables.

std::string s = "abc";
std::cout << s.length() << std::endl;

But if you're working with a pointer, you need to use the -> operator:

std::string* s = new std::string("abc");
std::cout << s->length() << std::endl;

It can also be overloaded to perform a specific function for a certain object type. Smart pointers like shared_ptr and unique_ptr, as well as STL container iterators, overload this operator to mimic native pointer semantics.

For example:

std::map<int, int>::iterator it = mymap.begin(), end = mymap.end();
for (; it != end; ++it)
    std::cout << it->first << std::endl;

Use of document.getElementById in JavaScript


 var x = document.getElementById("age");

Here x is the element with id="age".

Now look at the following line

var age = document.getElementById("age").value;

this means you are getting the value of the element which has id="age"

Display fullscreen mode on Tkinter

I think this is what you're looking for:

Tk.attributes("-fullscreen", True)  # substitute `Tk` for whatever your `Tk()` object is called

You can use wm_attributes instead of attributes, too.

Then just bind the escape key and add this to the handler:

Tk.attributes("-fullscreen", False)

An answer to another question alluded to this (with wm_attributes). So, that's how I found out. But, no one just directly went out and said it was the answer for some reason. So, I figured it was worth posting.

Here's a working example (tested on Xubuntu 14.04) that uses F11 to toggle fullscreen on and off and where escape will turn it off only:

import sys
if sys.version_info[0] == 2:  # Just checking your Python version to import Tkinter properly.
    from Tkinter import *
    from tkinter import *

class Fullscreen_Window:

    def __init__(self): = Tk()'-zoomed', True)  # This just maximizes it so we can see the window. It's nothing to do with fullscreen.
        self.frame = Frame(
        self.state = False"<F11>", self.toggle_fullscreen)"<Escape>", self.end_fullscreen)

    def toggle_fullscreen(self, event=None):
        self.state = not self.state  # Just toggling the boolean"-fullscreen", self.state)
        return "break"

    def end_fullscreen(self, event=None):
        self.state = False"-fullscreen", False)
        return "break"

if __name__ == '__main__':
    w = Fullscreen_Window()

If you want to hide a menu, too, there are only two ways I've found to do that. One is to destroy it. The other is to make a blank menu to switch between.  # self.blank_menu is a Menu object

Then switch it back to your menu when you want it to show up again.  # is your menu.

Create mysql table directly from CSV file using the CSV Storage engine?

If you're ok with using Python, Pandas worked great for me (csvsql hanged forever for my case). Something like:

from sqlalchemy import create_engine
import pandas as pd

df = pd.read_csv('/PATH/TO/FILE.csv')
# Optional, set your indexes to get Primary Keys
df = df.set_index(['COL A', 'COL B'])

engine = create_engine('mysql://user:pass@host/db', echo=False)

df.to_sql(table_name, dwh_engine, index=False)

Also this doesn't solve the "using CSV engine" part which was part of the question but might me useful as well.

How to open a workbook specifying its path

You can also open a required file through a prompt, This helps when you want to select file from different path and different file.

Sub openwb()
Dim wkbk As Workbook
Dim NewFile As Variant

NewFile = Application.GetOpenFilename("microsoft excel files (*.xlsm*), *.xlsm*")

If NewFile <> False Then
Set wkbk = Workbooks.Open(NewFile)
End If
End Sub

Remove warning messages in PHP

in Core Php to hide warning message set error_reporting(0) at top of common include file or individual file.

In Wordpress hide Warnings and Notices add following code in wp-config.php file

ini_set('error_reporting', E_ALL );
define('WP_DEBUG', false);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);

How can I determine the type of an HTML element in JavaScript?

You can use generic code inspection via instanceof:

var e = document.getElementById('#my-element');
if (e instanceof HTMLInputElement) {}         // <input>
elseif (e instanceof HTMLSelectElement) {}    // <select>
elseif (e instanceof HTMLTextAreaElement) {}  // <textarea>
elseif (  ... ) {}                            // any interface

Look here for a complete list of interfaces.

How to create an object property from a variable value in JavaScript?

The following demonstrates an alternative approach for returning a key pair object using the form of (a, b). The first example uses the string 'key' as the property name, and 'val' as the value.

Example #1:

(function(o,a,b){return o[a]=b,o})({},'key','val');

Example: #2:

var obj = { foo: 'bar' };
(function(o,a,b){return o[a]=b,o})(obj,'key','val');

As shown in the second example, this can modify existing objects, too (if property is already defined in the object, value will be overwritten).

Result #1: { key: 'val' }

Result #2: { foo: 'bar', key: 'val' }

How to get the error message from the error code returned by GetLastError()?

Updated (11/2017) to take into consideration some comments.

Easy example:

wchar_t buf[256];
               buf, (sizeof(buf) / sizeof(wchar_t)), NULL);

Can I create view with parameter in MySQL?

Actually if you create func:

create function p1() returns INTEGER DETERMINISTIC NO SQL return @p1;

and view:

create view h_parm as
select * from sw_hardware_big where unit_id = p1() ;

Then you can call a view with a parameter:

select s.* from (select @p1:=12 p) parm , h_parm s;

I hope it helps.

How to convert a normal Git repository to a bare one?

Oneliner for doing all of the above operations:

for i in `ls -A .`; do if [ $i != ".git" ]; then rm -rf $i; fi; done; mv .git/* .; rm -rf .git; git config --bool core.bare true

(don't blame me if something blows up and you didn't have backups :P)

Java dynamic array sizes?

No you can't change the size of an array once created. You either have to allocate it bigger than you think you'll need or accept the overhead of having to reallocate it needs to grow in size. When it does you'll have to allocate a new one and copy the data from the old to the new:

int[] oldItems = new int[10];
for (int i = 0; i < 10; i++) {
    oldItems[i] = i + 10;
int[] newItems = new int[20];
System.arraycopy(oldItems, 0, newItems, 0, 10);
oldItems = newItems;

If you find yourself in this situation, I'd highly recommend using the Java Collections instead. In particular ArrayList essentially wraps an array and takes care of the logic for growing the array as required:

List<XClass> myclass = new ArrayList<XClass>();
myclass.add(new XClass());
myclass.add(new XClass());

Generally an ArrayList is a preferable solution to an array anyway for several reasons. For one thing, arrays are mutable. If you have a class that does this:

class Myclass {
    private int[] items;

    public int[] getItems() {
        return items;

you've created a problem as a caller can change your private data member, which leads to all sorts of defensive copying. Compare this to the List version:

class Myclass {
    private List<Integer> items;

    public List<Integer> getItems() {
        return Collections.unmodifiableList(items);

Best way to alphanumeric check in JavaScript

In a tight loop, it's probably better to avoid regex and hardcode your characters:

const CHARS = new Set("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
function isAlphanumeric(char) {
    return CHARS.has(char);

Form Validation With Bootstrap (jQuery)

enter image description here

Here is a very simple and lightweight plugin for validation with Boostrap, you can use it if you like:

Get selected value in dropdown list using JavaScript

Just use

  • $('#SelectBoxId option:selected').text(); for getting the text as listed

  • $('#SelectBoxId').val(); for getting the selected index value

jQuery Determine if a matched class has a given id

update: sorry misunderstood the question, removed .has() answer.

another alternative way, create .hasId() plugin

// the plugin_x000D_
$.fn.hasId = function(id) {_x000D_
  return this.attr('id') == id;_x000D_
// select first class_x000D_
$('.mydiv').hasId('foo') ?_x000D_
  console.log('yes') : console.log('no');_x000D_
// select second class_x000D_
// $('.mydiv').eq(1).hasId('foo')_x000D_
// or_x000D_
$('.mydiv:eq(1)').hasId('foo') ?_x000D_
  console.log('yes') : console.log('no');
<script src=""></script>_x000D_
<div class="mydiv" id="foo"></div>_x000D_
<div class="mydiv"></div>

Cannot hide status bar in iOS7

For Swift 2.0+ IOS 9

override func prefersStatusBarHidden() -> Bool {
return true

Openstreetmap: embedding map in webpage (like Google Maps)

You can use OpenLayers (js API for maps).

There's an example on their page showing how to embed OSM tiles.

Edit: New Link to OpenLayers examples

How to align checkboxes and their labels consistently cross-browsers

For consistency with form fields across browsers we use : box-sizing: border-box

button, checkbox, input, radio, textarea, submit, reset, search, any-form-field {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;

Angular 4: no component factory found,did you add it to @NgModule.entryComponents?

if you use routing in your application

make sure Add new components into the routing path

for example :

    const appRoutes: Routes = [
  { path: '', component: LoginComponent },
  { path: 'home', component: HomeComponent },
  { path: 'fundList',      component: FundListComponent },

How to use BigInteger?

java.math.BigInteger is an immutable class so we can not assign new object in the location of already assigned object. But you can create new object to assign new value like:

sum = sum.add(BigInteger.valueOf(i));

git - remote add origin vs remote set-url origin

git remote add => ADDS a new remote.

git remote set-url => UPDATES existing remote.

  1. The remote name that comes after add is a new remote name that did not exist prior to that command.
  2. The remote name that comes after set-url should already exist as a remote name to your repository.

git remote add myupstream someurl => myupstream remote name did not exist now creating it with this command.

git remote set-url upstream someurl => upstream remote name already exist i'm just changing it's url.

git remote add myupstream => **ADD** If you don't already have upstream
git remote set-url upstream # => **UPDATE** url for upstream

How to add a hook to the application context initialization event?

Since Spring 4.2 you can use @EventListener (documentation)

class MyClassWithEventListeners {

    void contextRefreshedEvent() {
        System.out.println("a context refreshed event happened");

Remove duplicate values from JS array

The top answers have complexity of O(n²), but this can be done with just O(n) by using an object as a hash:

function getDistinctArray(arr) {
    var dups = {};
    return arr.filter(function(el) {
        var hash = el.valueOf();
        var isDup = dups[hash];
        dups[hash] = true;
        return !isDup;

This will work for strings, numbers, and dates. If your array contains objects, the above solution won't work because when coerced to a string, they will all have a value of "[object Object]" (or something similar) and that isn't suitable as a lookup value. You can get an O(n) implementation for objects by setting a flag on the object itself:

function getDistinctObjArray(arr) {
    var distinctArr = arr.filter(function(el) {
        var isDup = el.inArray;
        el.inArray = true;
        return !isDup;
    distinctArr.forEach(function(el) {
        delete el.inArray;
    return distinctArr;

2019 edit: Modern versions of JavaScript make this a much easier problem to solve. Using Set will work, regardless of whether your array contains objects, strings, numbers, or any other type.

function getDistinctArray(arr) {
    return [ Set(arr)];

The implementation is so simple, defining a function is no longer warranted.

Convert interface{} to int

I wrote a library that can help with type convertions

js := jonson.New([]interface{}{55.6, 70.8, 10.4, 1, "48", "-90"})

js.SliceMap(func(jsn *jonson.JSON, index int) *jonson.JSON {
    return jsn
}).SliceMap(func(jsn *jonson.JSON, index int) *jonson.JSON {
    if jsn.GetUnsafeInt() > 50{
    return jsn
}) // ["55","70",10,1,48,-90]

How do I install a pip package globally instead of locally?

Maybe --force-reinstall would work, otherwise --ignore-installed should do the trick.

The APK file does not exist on disk

The problem for me was that somehow it could really not find the apk, while the apk exists.

The APK file /Users/Paul/AndroidStudioProjects/android-tv-launcher/ui/build/outputs/apk/nameofapk.apk does not exist on disk.
Error while Installing APK

All I had to do, was right click on the apk-copy relative path, and just

adb install -r <paste of relative path>

And the apk was installed and good to go. This issue happened on OSX for me.

babel-loader jsx SyntaxError: Unexpected token

I ran into a similar issue when migrating from babel 5 to babel 6.

I was just running babel to compile the src to lib folder babel src --out-dir lib

I will share my setup for babel 6:

Ensure you have the following babel 6 devDependencies installed

"babel-core": "^6.7.6",
"babel-loader": "^6.2.4",
"babel-preset-es2015": "^6.6.0",
"babel-preset-react": "^6.5.0",
"babel-preset-stage-0": "^6.5.0"

Add your .babelrc file to the project:

  "presets": ["es2015", "stage-0", "react"]

Get current time in seconds since the Epoch on Linux, Bash

Pure bash solution

Since bash 5.0 (released on 7 Jan 2019) you can use the built-in variable EPOCHSECONDS.


There is also EPOCHREALTIME which includes fractions of seconds.


EPOCHREALTIME can be converted to micro-seconds (µs) by removing the decimal point. This might be of interest when using bash's built-in arithmetic (( expression )) which can only handle integers.

$ echo ${EPOCHREALTIME/./}

In all examples from above the printed time values are equal for better readability. In reality the time values would differ since each command takes a small amount of time to be executed.

jQuery click / toggle between two functions

I used this to create a toggle effect between two functions.

var x = false;
$(element).on('click', function(){
 if (!x){
  x = true;
 else {
  x = false;

Maven dependency for Servlet 3.0 API?

Just for newcomers.


Python subprocess/Popen with a modified environment

With Python 3.5 you could do it this way:

import os
import subprocess

my_env = {**os.environ, 'PATH': '/usr/sbin:/sbin:' + os.environ['PATH']}

subprocess.Popen(my_command, env=my_env)

Here we end up with a copy of os.environ and overridden PATH value.

It was made possible by PEP 448 (Additional Unpacking Generalizations).

Another example. If you have a default environment (i.e. os.environ), and a dict you want to override defaults with, you can express it like this:

my_env = {**os.environ, **dict_with_env_variables}

URL encoding in Android

You don't encode the entire URL, only parts of it that come from "unreliable sources".

  • Java:

    String query = URLEncoder.encode("apples oranges", "utf-8");
    String url = "" + query;
  • Kotlin:

    val query: String = URLEncoder.encode("apples oranges", "utf-8")
    val url = "$query"

Alternatively, you can use Strings.urlEncode(String str) of DroidParts that doesn't throw checked exceptions.

Or use something like

String uri = Uri.parse("http://...")
                .appendQueryParameter("key", "val")

How to simulate a click by using x,y coordinates in JavaScript?

Yes, you can simulate a mouse click by creating an event and dispatching it:

function click(x,y){
    var ev = document.createEvent("MouseEvent");
    var el = document.elementFromPoint(x,y);
        true /* bubble */, true /* cancelable */,
        window, null,
        x, y, 0, 0, /* coordinates */
        false, false, false, false, /* modifier keys */
        0 /*left*/, null

Beware of using the click method on an element -- it is widely implemented but not standard and will fail in e.g. PhantomJS. I assume jQuery's implemention of .click() does the right thing but have not confirmed.

How to force HTTPS using a web.config file

The excellent NWebsec library can upgrade your requests from HTTP to HTTPS using its upgrade-insecure-requests tag within the Web.config:

      <content-Security-Policy enabled="true">
        <upgrade-insecure-requests enabled="true"  />

Cross origin requests are only supported for HTTP but it's not cross-domain

It works best this way. Make sure that both files are on the server. When calling the html page, make use of the web address like: http:://localhost/myhtmlfile.html, and not, C::///users/myhtmlfile.html. Make usre as well that the url passed to the json is a web address as denoted below:

                    source: function(query, process){
                            url: 'http://localhost:2222/bootstrap/source.php',
                            type: 'POST',
                            data: 'query=' +query,
                            dataType: 'JSON',
                            async: true,
                            success: function(data){

Composer: Command Not Found

First I did alias setup on bash / zsh profile.

alias composer="php /usr/local/bin/composer.phar"

Then I moved composer.phar to /usr/local/bin/

cd /usr/local/bin
mv composer.phar composer

Then made composer executable by running

sudo chmod +x composer

Referencing value in a closed Excel workbook using INDIRECT?


Here's a dinosaur method for you on Office 2010.

Write the full address you want using concatenate (the "&" method of combining text).

Do this for all the addresses you need. It should look like:

="="&"'\FULL NETWORK ADDRESS including [Spreadsheet Name]"&W3&"'!$w4"

The W3 is a dynamic reference to what sheet I am using, the W4 is the cell I want to get from the sheet.

Once you have this, start up a macro recording session. Copy the cell and paste it into another. I pasted it into a merged cell and it gave me the classic "Same size" error. But one thing it did was paste the resulting text from my concatenate (including that extra "=").

Copy over however many you did this for. Then, go into each pasted cell, select he text and just hit enter. It updates it to an active direct reference.

Once you have finished, put the cursor somewhere nice and stop the macro. Assign it to a button and you are done.

It is a bit of a PITA to do this the first time, but once you have done it, you have just made the square peg fit that daamned round hole.

Python list sort in descending order

In one line, using a lambda:

timestamps.sort(key=lambda x: time.strptime(x, '%Y-%m-%d %H:%M:%S')[0:6], reverse=True)

Passing a function to list.sort:

def foo(x):
    return time.strptime(x, '%Y-%m-%d %H:%M:%S')[0:6]

timestamps.sort(key=foo, reverse=True)

postgresql - replace all instances of a string within text field

The Regular Expression Way

If you need stricter replacement matching, PostgreSQL's regexp_replace function can match using POSIX regular expression patterns. It has the syntax regexp_replace(source, pattern, replacement [, flags ]).

I will use flags i and g for case-insensitive and global matching, respectively. I will also use \m and \M to match the beginning and the end of a word, respectively.

There are usually quite a few gotchas when performing regex replacment. Let's see how easy it is to replace a cat with a dog.

SELECT regexp_replace('Cat bobcat cat cats catfish', 'cat', 'dog');
-->                    Cat bobdog cat cats catfish

SELECT regexp_replace('Cat bobcat cat cats catfish', 'cat', 'dog', 'i');
-->                    dog bobcat cat cats catfish

SELECT regexp_replace('Cat bobcat cat cats catfish', 'cat', 'dog', 'g');
-->                    Cat bobdog dog dogs dogfish

SELECT regexp_replace('Cat bobcat cat cats catfish', 'cat', 'dog', 'gi');
-->                    dog bobdog dog dogs dogfish

SELECT regexp_replace('Cat bobcat cat cats catfish', '\mcat', 'dog', 'gi');
-->                    dog bobcat dog dogs dogfish

SELECT regexp_replace('Cat bobcat cat cats catfish', 'cat\M', 'dog', 'gi');
-->                    dog bobdog dog cats catfish

SELECT regexp_replace('Cat bobcat cat cats catfish', '\mcat\M', 'dog', 'gi');
-->                    dog bobcat dog cats catfish

SELECT regexp_replace('Cat bobcat cat cats catfish', '\mcat(s?)\M', 'dog\1', 'gi');
-->                    dog bobcat dog dogs catfish

Even after all of that, there is at least one unresolved condition. For example, sentences that begin with "Cat" will be replaced with lower-case "dog" which break sentence capitalization.

Check out the current PostgreSQL pattern matching docs for all the details.

Update entire column with replacement text

Given my examples, maybe the safest option would be:

UPDATE table SET field = regexp_replace(field, '\mcat\M', 'dog', 'gi');

How do I pass a variable to the layout using Laravel' Blade templating?

class PagesController extends BaseController {
    protected $layout = 'layouts.master';

    public function index()
        $this->layout->title = "Home page";
        $this->layout->content = View::make('pages/index');

At the Blade Template file, REMEMBER to use @ in front the variable.

<title>{{ $title or '' }}</title>

Stop MySQL service windows

Easy way to shutdown mySQL server for Windows7 :

My Computer > Manage > Services and Application > Services > select "MySQL 56"(the name depends upon the version of MySQL installed.) three options are present at left top corner. Stop the Service pause the Service Restart the Service

choose Stop the service > to stop the server

Again to start you can come to the same location or we can chose tools options on mySQL GUI Server > Startup/Shutdown > Choose to Startup or Shutdown

PS: some times it is not possible to stop the server from the GUI even though the options are provided. so is the reason the above alternative method is provided.

share the ans. to improve. thanks

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException Error

NullPointerExceptions are among the easier exceptions to diagnose, frequently. Whenever you get an exception in Java and you see the stack trace ( that's what your second quote-block is called, by the way ), you read from top to bottom. Often, you will see exceptions that start in Java library code or in native implementations methods, for diagnosis you can just skip past those until you see a code file that you wrote.

Then you like at the line indicated and look at each of the objects ( instantiated classes ) on that line -- one of them was not created and you tried to use it. You can start by looking up in your code to see if you called the constructor on that object. If you didn't, then that's your problem, you need to instantiate that object by calling new Classname( arguments ). Another frequent cause of NullPointerExceptions is accidentally declaring an object with local scope when there is an instance variable with the same name.

In your case, the exception occurred in your constructor for Workshop on line 75. <init> means the constructor for a class. If you look on that line in your code, you'll see the line


There are fairly clearly two objects on this line: denimjeansButton and this. this is synonymous with the class instance you are currently in and you're in the constructor, so it can't be this. denimjeansButton is your culprit. You never instantiated that object. Either remove the reference to the instance variable denimjeansButton or instantiate it.

How can I use "." as the delimiter with String.split() in java

Have you tried escaping the dot? like this:

String[] words = line.split("\\.");

Ansible: How to delete files and folders inside a directory?

There is an issue open with respect to this.

For now, the solution works for me: create a empty folder locally and synchronize it with the remote one.

Here is a sample playbook:

- name: "Empty directory"
  hosts: *
    - name: "Create an empty directory (locally)"
        module: file
        state: directory
        path: "/tmp/empty"

    - name: Empty remote directory
        src: /tmp/empty/
        dest: /home/mydata/web/
        delete: yes
        recursive: yes

My eclipse won't open, i download the bundle pack it keeps saying error log

Make sure you have the prerequisite, a JVM ( installed.

This will be a JRE and JDK package.

There are a number of sources which includes:

"Notice: Undefined variable", "Notice: Undefined index", and "Notice: Undefined offset" using PHP

In PHP you need fist to define the variable after that you can use it.
We can check variable is defined or not in very efficient way!.

//If you only want to check variable has value and value has true and false value.
//But variable must be defined first.



//If you want to check variable is define or undefine
//Isset() does not check that variable has true or false value
//But it check null value of variable


Simple Explanation

//It will work with :- true,false,NULL
$defineVarialbe = false;
    echo "true";
    echo "false";

//It will check variable is define or not and variable has null value.
    echo "true";
    echo "false";

Changing file permission in Python

No need to remember flags. Remember that you can always do:["chmod", "a-w", "file/path])

Not portable but easy to write and remember:

  • u - user
  • g - group
  • o - other
  • a - all
  • + or - (add or remove permission)
  • r - read
  • w - write
  • x - execute

Refer man chmod for additional options and more detailed explanation.

The entitlements specified...profile. (0xE8008016). Error iOS 4.2

Just came across this issue myself, the problem was that I had a Entitlements.plist file in the project as part of an ad hoc distribution, and its get-task-allow (ie. 'can be debugged') property was set to NO - setting this to YES fixed the issue and allowed the app to run from Xcode4 on the device in development.

Naturally need to set it back to NO for ad hoc distributions, but just thought I'd mention it in case anyone else comes across the same problem.

Update Angular model after setting input value with jQuery

I've written this little plugin for jQuery which will make all calls to .val(value) update the angular element if present:

(function($, ng) {
  'use strict';

  var $val = $.fn.val; // save original jQuery function

  // override jQuery function
  $.fn.val = function (value) {
    // if getter, just return original
    if (!arguments.length) {
      return $;

    // get result of original function
    var result = $, value);

    // trigger angular input (this[0] is the DOM object)

    // return the original result
    return result; 
})(window.jQuery, window.angular);

Just pop this script in after jQuery and angular.js and val(value) updates should now play nice.

Minified version:

!function(n,t){"use strict";var r=n.fn.val;n.fn.val=function(n){if(!arguments.length)return;var,n);return t.element(this[0]).triggerHandler("input"),e}}(window.jQuery,window.angular);


// the function_x000D_
(function($, ng) {_x000D_
  'use strict';_x000D_
  var $val = $.fn.val;_x000D_
  $.fn.val = function (value) {_x000D_
    if (!arguments.length) {_x000D_
      return $;_x000D_
    var result = $, value);_x000D_
    return result;_x000D_
})(window.jQuery, window.angular);_x000D_
(function(ng){ _x000D_
  ng.module('example', [])_x000D_
    .controller('ExampleController', function($scope) {_x000D_
      $scope.output = "output";_x000D_
      $scope.change = function() {_x000D_
        $scope.output = "" + $scope.input;_x000D_
(function($){  _x000D_
  $(function() {_x000D_
    var button = $('#button');_x000D_
    if (button.length)_x000D_
      console.log('hello, button');_x000D_
    _x000D_ {_x000D_
      var input = $('#input');_x000D_
      var value = parseInt(input.val());_x000D_
      value = isNaN(value) ? 0 : value;_x000D_
      input.val(value + 1);_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<div ng-app="example" ng-controller="ExampleController">_x000D_
  <input type="number" id="input" ng-model="input" ng-change="change()" />_x000D_
  <button id="button">+</button>_x000D_

WPF: ItemsControl with scrollbar (ScrollViewer)

Put your ScrollViewer in a DockPanel and set the DockPanel MaxHeight property

<DockPanel MaxHeight="700">
  <ScrollViewer VerticalScrollBarVisibility="Auto">
   <ItemsControl ItemSource ="{Binding ...}">

Hive load CSV with commas in quoted fields

Add a backward slash in FIELDS TERMINATED BY '\;'

For Example:

CREATE  TABLE demo_table_1_csv
COMMENT 'my_csv_table 1'
LOCATION 'your_hdfs_path'
select a.tran_uuid,a.cust_id,a.risk_flag,a.lookback_start_date,a.lookback_end_date,b.scn_name,b.alerted_risk_category,
CASE WHEN (b.activity_id is not null ) THEN 1 ELSE 0 END as Alert_Flag 
FROM scn1_rcc1_agg as a LEFT OUTER JOIN scenario_activity_alert as b ON a.tran_uuid = b.activity_id;

I have tested it, and it worked.

Access Tomcat Manager App from different host

To access the tomcat manager from different machine you have to follow bellow steps:

1. Update conf/tomcat-users.xml file with user and some roles:

<role rolename="manager-gui"/>
 <role rolename="manager-script"/>
 <role rolename="manager-jmx"/>
 <role rolename="manager-status"/>
 <user username="admin" password="admin" roles="manager-gui,manager-script,manager-jmx,manager-status"/>

Here admin user is assigning roles="manager-gui,manager-script,manager-jmx,manager-status".

Here tomcat user and password is : admin

2. Update webapps/manager/META-INF/context.xml file (Allowing IP address):

Default configuration:

<Context antiResourceLocking="false" privileged="true" >
  <Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />
  <Manager sessionAttributeValueClassNameFilter="java\.lang\.(?:Boolean|Integer|Long|Number|String)|org\.apache\.catalina\.filters\.CsrfPreventionFilter\$LruCache(?:\$1)?|java\.util\.(?:Linked)?HashMap"/>

Here in Valve it is allowing only local machine IP start with 127.\d+.\d+.\d+ .

2.a : Allow specefic IP:

<Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1|YOUR.IP.ADDRESS.HERE" />

Here you just replace |YOUR.IP.ADDRESS.HERE with your IP address

2.b : Allow all IP:

<Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow=".*" />

Here using allow=".*" you are allowing all IP.

Thanks :)

Prevent Default on Form Submit jQuery

Your Code is Fine just you need to place it inside the ready function.

$(document).ready( function() {

How can I shrink the drawable on a button?

I made a custom button class to achieve this.

public class CustomButton extends {

    private Drawable mDrawable;

    public CustomButton(Context context, AttributeSet attrs) {
        super(context, attrs);

        TypedArray a = context.getTheme().obtainStyledAttributes(
                0, 0);

        try {
            float mWidth = a.getDimension(R.styleable.CustomButton_drawable_width, 0);
            float mHeight = a.getDimension(R.styleable.CustomButton_drawable_width, 0);

            Drawable[] drawables = this.getCompoundDrawables();
            Drawable[] resizedDrawable = new Drawable[4];

            for (int i = 0; i < drawables.length; i++) {
                if (drawables[i] != null) {
                    mDrawable = drawables[i];
                resizedDrawable[i] = getResizedDrawable(drawables[i], mWidth, mHeight);

            this.setCompoundDrawables(resizedDrawable[0], resizedDrawable[1], resizedDrawable[2], resizedDrawable[3]);
        } finally {

    public Drawable getmDrawable() {
        return mDrawable;

    private Drawable getResizedDrawable(Drawable drawable, float mWidth, float mHeight) {
        if (drawable == null) {
            return null;

        try {
            Bitmap bitmap;

            bitmap = Bitmap.createBitmap((int)mWidth, (int)mHeight, Bitmap.Config.ARGB_8888);

            Canvas canvas = new Canvas(bitmap);
            drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
            return drawable;
        } catch (OutOfMemoryError e) {
            // Handle the error
            return null;


<?xml version="1.0" encoding="utf-8"?>
    <declare-styleable name="CustomButton">
        <attr name="drawable_width" format="dimension" />
        <attr name="drawable_height" format="dimension" />

Usage in xml

<RelativeLayout xmlns:android=""

            custom:drawable_width="10dp" />


LINQ: Select an object and change some properties without creating a new object

We often run into this where we want to include a the index value and first and last indicators in a list without creating a new object. This allows you to know the position of the item in your list, enumeration, etc. without having to modify the existing class and then knowing whether you're at the first item in the list or the last.

foreach (Item item in this.Items
    .Select((x, i) => {
    x.ListIndex = i;
    x.IsFirst = i == 0;
    x.IsLast = i == this.Items.Count-1;
    return x;

You can simply extend any class by using:

public abstract class IteratorExtender {
    public int ListIndex { get; set; }
    public bool IsFirst { get; set; } 
    public bool IsLast { get; set; } 

public class Item : IteratorExtender {}

Using number as "index" (JSON)

When a Javascript object property's name doesn't begin with either an underscore or a letter, you cant use the dot notation (like Game.status[0].0), and you must use the alternative notation, which is Game.status[0][0].

One different note, do you really need it to be an object inside the status array? If you're using the object like an array, why not use a real array instead?

Git: How to find a deleted file in the project commit history?

Get a list of the deleted files and copy the full path of the deleted file

git log --diff-filter=D --summary | grep delete

Execute the next command to find commit id of that commit and copy the commit id

git log --all -- FILEPATH

Show diff of deleted file


Remember, you can write output to a file using > like

git show COMMIT_ID -- FILE_PATH > deleted.diff

How do I implement Toastr JS?

Toastr is a very nice component, and you can show messages with theses commands:

// for success - green box
toastr.success('Success messages');

// for errors - red box
toastr.error('errors messages');

// for warning - orange box
toastr.warning('warning messages');

// for info - blue box'info messages');

If you want to provide a title on the toastr message, just add a second argument:

// for info - blue box
toastr.success('The process has been saved.', 'Success');

you also can change the default behaviour using something like this:

toastr.options.timeOut = 3000; // 3s

See more on the github of the project.


A sample of use:

$(document).ready(function() {

    // show when page load'Page Loaded!');

    $('#linkButton').click(function() {
       // show when the button is clicked
       toastr.success('Click Button');



and a html:

<a id='linkButton'>Show Message</a>

Flushing buffers in C

Flushing the output buffers:

printf("Buffered, will be flushed");
fflush(stdout); // Prints to screen or whatever your standard out is


fprintf(fd, "Buffered, will be flushed");
fflush(fd);  //Prints to a file

Can be a very helpful technique. Why would you want to flush an output buffer? Usually when I do it, it's because the code is crashing and I'm trying to debug something. The standard buffer will not print everytime you call printf() it waits until it's full then dumps a bunch at once. So if you're trying to check if you're making it to a function call before a crash, it's helpful to printf something like "got here!", and sometimes the buffer hasn't been flushed before the crash happens and you can't tell how far you've really gotten.

Another time that it's helpful, is in multi-process or multi-thread code. Again, the buffer doesn't always flush on a call to a printf(), so if you want to know the true order of execution of multiple processes you should fflush the buffer after every print.

I make a habit to do it, it saves me a lot of headache in debugging. The only downside I can think of to doing so is that printf() is an expensive operation (which is why it doesn't by default flush the buffer).

As far as flushing the input buffer (stdin), you should not do that. Flushing stdin is undefined behavior according to the C11 standard § part 2:

If stream points to an output stream ... the fflush function causes any unwritten data for that stream ... to be written to the file; otherwise, the behavior is undefined.

On some systems, Linux being one as you can see in the man page for fflush(), there's a defined behavior but it's system dependent so your code will not be portable.

Now if you're worried about garbage "stuck" in the input buffer you can use fpurge() on that. See here for more on fflush() and fpurge()

upstream sent too big header while reading response header from upstream

upstream sent too big header while reading response header from upstream is nginx's generic way of saying "I don't like what I'm seeing"

  1. Your upstream server thread crashed
  2. The upstream server sent an invalid header back
  3. The Notice/Warnings sent back from STDERR overflowed their buffer and both it and STDOUT were closed

3: Look at the error logs above the message, is it streaming with logged lines preceding the message? PHP message: PHP Notice: Undefined index: Example snippet from a loop my log file:

2015/11/23 10:30:02 [error] 32451#0: *580927 FastCGI sent in stderr: "PHP message: PHP Notice:  Undefined index: Firstname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Lastname in /srv/www/classes/data_convert.php on line 1090
... // 20 lines of same
PHP message: PHP Notice:  Undefined index: Firstname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Lastname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undef
2015/11/23 10:30:02 [error] 32451#0: *580927 FastCGI sent in stderr: "ta_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Firstname

you can see in the 3rd line from the bottom that the buffer limit was hit, broke, and the next thread wrote in over it. Nginx then closed the connection and returned 502 to the client.

2: log all the headers sent per request, review them and make sure they conform to standards (nginx does not permit anything older than 24 hours to delete/expire a cookie, sending invalid content length because error messages were buffered before the content counted...). getallheaders function call can usually help out in abstracted code situations php get all headers

examples include:

//expire cookie
setcookie ( 'bookmark', '', strtotime('2012-01-01 00:00:00') );
// nginx will refuse this header response, too far past to accept

and this:

header('Content-type: image/jpg');

<?php   //a space was injected into the output above this line
header('Content-length: ' . filesize('image.jpg') );
echo file_get_contents('image.jpg');
// error! the response is now 1-byte longer than header!!

1: verify, or make a script log, to ensure your thread is reaching the correct end point and not exiting before completion.

What do *args and **kwargs mean?

Putting *args and/or **kwargs as the last items in your function definition’s argument list allows that function to accept an arbitrary number of arguments and/or keyword arguments.

For example, if you wanted to write a function that returned the sum of all its arguments, no matter how many you supply, you could write it like this:

def my_sum(*args):
    return sum(args)

It’s probably more commonly used in object-oriented programming, when you’re overriding a function, and want to call the original function with whatever arguments the user passes in.

You don’t actually have to call them args and kwargs, that’s just a convention. It’s the * and ** that do the magic.

The official Python documentation has a more in-depth look.

Regular Expression for password validation

Update to Justin answer above. if you want to use it using Data Annotation in MVC you can do as follow

[RegularExpression(@"^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^\da-zA-Z]).{8,15}$", ErrorMessage = "Password must be between 6 and 20 characters and contain one uppercase letter, one lowercase letter, one digit and one special character.")]

How to retrieve SQL result column value using column name in Python?

selecting values from particular column:

import pymysql
db = pymysql.connect("localhost","root","root","school")
sql="""select Total from student"""
    #query execution
    #fetch all rows 
    rs = cursor.fetchall()
    #iterate through rows
    for i in rs:
        #converting set to list
        #taking the first element from the list and append it to the list

How to define an enumerated type (enum) in C?

I tried with gcc and come up with for my need I was forced to use the last alternative, to compile with out error.

typedef enum state {a = 0, b = 1, c = 2} state;

typedef enum state {a = 0, b = 1, c = 2} state;

typedef enum state old; // New type, alias of the state type.
typedef enum state new; // New type, alias of the state type.

new now     = a;
old before  = b;

printf("State   now = %d \n", now);
printf("Sate before = %d \n\n", before);

Is there an equivalent of 'which' on the Windows command line?

Not in stock Windows but it is provided by Services for Unix and there are several simple batch scripts floating around that accomplish the same thing such this this one.

How to find nth occurrence of character in a string?


Match anything followed by / two times, then again. The third one is the one you want

The Matcher state can be used to tell where the last / is

Why won't my PHP app send a 404 error?

That is correct behaviour, it's up to you to create the contents for the 404 page.
The 404 header is used by spiders and download-managers to determine if the file exists.
(A page with a 404 header won't be indexed by google or other search-engines)

Normal users however don't look at http-headers and use the page as a normal page.

What does value & 0xff do in Java?


The hex literal 0xFF is an equal int(255). Java represents int as 32 bits. It look like this in binary:

00000000 00000000 00000000 11111111

When you do a bit wise AND with this value(255) on any number, it is going to mask(make ZEROs) all but the lowest 8 bits of the number (will be as-is).

... 01100100 00000101 & ...00000000 11111111 = 00000000 00000101

& is something like % but not really.

And why 0xff? this in ((power of 2) - 1). All ((power of 2) - 1) (e.g 7, 255...) will behave something like % operator.

In binary, 0 is, all zeros, and 255 looks like this:

00000000 00000000 00000000 11111111

And -1 looks like this

11111111 11111111 11111111 11111111

When you do a bitwise AND of 0xFF and any value from 0 to 255, the result is the exact same as the value. And if any value higher than 255 still the result will be within 0-255.

However, if you do:

-1 & 0xFF

you get

00000000 00000000 00000000 11111111, which does NOT equal the original value of -1 (11111111 is 255 in decimal).

Few more bit manipulation: (Not related to the question)

X >> 1 = X/2
X << 1 = 2X

Check any particular bit is set(1) or not (0) then

 int thirdBitTobeChecked =   1 << 2   (...0000100)
 int onWhichThisHasTobeTested = 5     (.......101)

 int isBitSet = onWhichThisHasTobeTested  & thirdBitTobeChecked;
 if(isBitSet > 0) {
  //Third Bit is set to 1 

Set(1) a particular bit

 int thirdBitTobeSet =   1 << 2    (...0000100)
 int onWhichThisHasTobeSet = 2     (.......010)
 onWhichThisHasTobeSet |= thirdBitTobeSet;

ReSet(0) a particular bit

int thirdBitTobeReSet =   ~(1 << 2)  ; //(...1111011)
int onWhichThisHasTobeReSet = 6      ;//(.....000110)
onWhichThisHasTobeReSet &= thirdBitTobeReSet;


Just note that if you perform XOR operation twice, will results the same value.

byte toBeEncrypted = 0010 0110
byte salt          = 0100 1011

byte encryptedVal  =  toBeEncrypted ^ salt == 0110 1101
byte decryptedVal  =  encryptedVal  ^ salt == 0010 0110 == toBeEncrypted :)

One more logic with XOR is

if     A (XOR) B == C (salt)
then   C (XOR) B == A
       C (XOR) A == B

The above is useful to swap two variables without temp like below

a = a ^ b; b = a ^ b; a = a ^ b;


a ^= b ^= a ^= b;

Elasticsearch difference between MUST and SHOULD bool query

As said in the documentation:

Must: The clause (query) must appear in matching documents.

Should: The clause (query) should appear in the matching document. In a boolean query with no must clauses, one or more should clauses must match a document. The minimum number of should clauses to match can be set using the minimum_should_match parameter.

In other words, results will have to be matched by all the queries present in the must clause ( or match at least one of the should clauses if there is no must clause.

Since you want your results to satisfy all the queries, you should use must.

You can indeed use filters inside a boolean query.

vi/vim editor, copy a block (not usual action)

Their Documentation says:

Cut and paste:

  1. Position the cursor where you want to begin cutting.
  2. Press v to select characters (or uppercase V to select whole lines).
  3. Move the cursor to the end of what you want to cut.
  4. Press d to cut (or y to copy).
  5. Move to where you would like to paste.
  6. Press P to paste before the cursor, or p to paste after.

Copy and paste is performed with the same steps except for step 4 where you would press y instead of d:

d = delete = cut

y = yank = copy

What is the purpose of "&&" in a shell command?

command_1 && command_2: execute command_2 only when command_1 is executed successfully.

command_1 || command_2: execute command_2 only when command_1 is not successful executed.

Feels similar as how an 'if' condition is executed in a mainstream programming language, like, in if (condition_1 && condition_2){...} condition_2 will be omitted if condition_1 is false and in if (condition_1 || condition_2){...} condition_2 will be omitted if condition_1 is true. See, it's the same trick you use for coding :)

How to draw border around a UILabel?

Swift version:

myLabel.layer.borderWidth = 0.5
myLabel.layer.borderColor = UIColor.greenColor().CGColor

For Swift 3:

myLabel.layer.borderWidth = 0.5
myLabel.layer.borderColor =

is it possible to update UIButton title/text programmatically?

I kept having problems with this, the only solution was to add an image and label as subviews to the uibutton. Then I discovered that the main problem was that I was using a UIButton with title: Attributed. When I changed it to Plain, just setting the titleLabel.text did the trick!

Storing image in database directly or as base64 data?

  • Pro base64: the encoded representation you handle is a pretty safe string. It contains neither control chars nor quotes. The latter point helps against SQL injection attempts. I wouldn't expect any problem to just add the value to a "hand coded" SQL query string.

  • Pro BLOB: the database manager software knows what type of data it has to expect. It can optimize for that. If you'd store base64 in a TEXT field it might try to build some index or other data structure for it, which would be really nice and useful for "real" text data but pointless and a waste of time and space for image data. And it is the smaller, as in number of bytes, representation.

How to change the Spyder editor background to dark?

In Spyder 4.1, you can change background color from: Tools > Preferences > Appearance > Syntax highlighting scheme

Java Try Catch Finally blocks without Catch

Regardless of exception thrown or not in try block - finally block will be executed. Exception would not be caught.

MYSQL order by both Ascending and Descending sorting

I don't understand what the meaning of ordering with the same column ASC and DESC in the same ORDER BY, but this how you can do it: naam DESC, naam ASC like so:

ORDER BY `product_category_id` DESC,`naam` DESC, `naam` ASC

MySQL parameterized queries

The linked docs give the following example:

   cursor.execute ("""
         UPDATE animal SET name = %s
         WHERE name = %s
       """, ("snake", "turtle"))
   print "Number of rows updated: %d" % cursor.rowcount

So you just need to adapt this to your own code - example:

cursor.execute ("""
            INSERT INTO Songs (SongName, SongArtist, SongAlbum, SongGenre, SongLength, SongLocation)
                (%s, %s, %s, %s, %s, %s)

        """, (var1, var2, var3, var4, var5, var6))

(If SongLength is numeric, you may need to use %d instead of %s).

Run Batch File On Start-up

Another option would be to run the batch file as a service, and set the startup of the service to "Automatic" or "Automatic (Delayed Start)". Check this question for more information on how to do it, personally I like NSSM the most.

Best way to resolve file path too long exception

From my experience, won't recommend my below answer for any public facing Web applications.

If you need it for your inhouse tools or for Testing, I would recommend to share it on your own machine.

-Right click on the root path you need to access
-Choose Properties
-Click on Share button and add your chosen users who can access it

This will then create a shared directory like \\{PCName}\{YourSharedRootDirectory} This could be definitely much less than your full path I hope, for me I could reduce to 30 characters from about 290 characters. :)

How to add new line in Markdown presentation?

I was using Markwon for markdown parsing in Android. The following worked great:

"My first line  \nMy second line  \nMy third line  \nMy last line"

...two spaces followed by \n at the end of each line.

Difference between <context:annotation-config> and <context:component-scan>

<context:component-scan /> implicitly enables <context:annotation-config/>

try with <context:component-scan base-package="..." annotation-config="false"/> , in your configuration @Service, @Repository, @Component works fine, but @Autowired,@Resource and @Inject doesn't work.

This means AutowiredAnnotationBeanPostProcessor will not be enabled and Spring container will not process the Autowiring annotations.

How do I compile with -Xlint:unchecked?

I know it sounds weird, but I'm pretty sure this is your problem:

Somewhere in you're using a generic collection without specifying the type. For example if you're using an ArrayList somewhere, you are doing this:

List list = new ArrayList();

When you should be doing this:

List<String> list = new ArrayList<String>();

Can iterators be reset in Python?

list(generator()) returns all remaining values for a generator and effectively resets it if it is not looped.

how to drop database in sqlite?

to delete your app database try this:


this will delete the database file

What do the icons in Eclipse mean?

This is a fairly comprehensive list from the Eclipse documentation. If anyone knows of another list — maybe with more details, or just the most common icons — feel free to add it.

Latest: JDT Icons

2019-06: JDT Icons

2019-03: JDT Icons

2018-12: JDT Icons

2018-09: JDT Icons

Photon: JDT Icons

Oxygen: JDT Icons

Neon: JDT Icons

Mars: JDT Icons

Luna: JDT Icons

Kepler: JDT Icons

Juno: JDT Icons

Indigo: JDT Icons

Helios: JDT Icons

There are also some CDT icons at the bottom of this help page.

If you're a Subversion user, the icons you're looking for may actually belong to Subclipse; see this excellent answer for more on those.

JavaScript Uncaught ReferenceError: jQuery is not defined; Uncaught ReferenceError: $ is not defined

You have an error in you script tag construction, this:

<script language="JavaScript" type="text/javascript" script src=""></script>

Should look like this:

<script language="JavaScript" type="text/javascript" src="//"></script>

You have a 'script' word lost in the middle of your script tag. Also you should remove the http:// to let the browser decide whether to use HTTP or HTTPS.


But your main error is that you are including jQuery UI (ONLY) you must include jQuery first! jQuery UI and jQuery are used together, not in separate. jQuery UI depends on jQuery. You should put this line before jQuery UI:

<script src=""></script>

Copy table without copying data





Remove a symlink to a directory

Assuming it actually is a symlink,

$ rm -d symlink

It should figure it out, but since it can't we enable the latent code that was intended for another case that no longer exists but happens to do the right thing here.

How can I query for null values in entity framework?

It appears that Linq2Sql has this "problem" as well. It appears that there is a valid reason for this behavior due to whether ANSI NULLs are ON or OFF but it boggles the mind why a straight "== null" will in fact work as you'd expect.

Java 11 package javax.xml.bind does not exist

According to the release-notes, Java 11 removed the Java EE modules:

java.xml.bind (JAXB) - REMOVED
  • Java 8 - OK
  • Java 9 - DEPRECATED
  • Java 10 - DEPRECATED
  • Java 11 - REMOVED

See JEP 320 for more info.

You can fix the issue by using alternate versions of the Java EE technologies. Simply add Maven dependencies that contain the classes you need:


Jakarta EE 8 update (Mar 2020)

Instead of using old JAXB modules you can fix the issue by using Jakarta XML Binding from Jakarta EE 8:


Jakarta EE 9 update (Nov 2020)

Use latest release of Eclipse Implementation of JAXB 3.0.0:


Note: Jakarta EE 9 adopts new API package namespace jakarta.xml.bind.*, so update import statements:

javax.xml.bind -> jakarta.xml.bind

how to count the spaces in a java string?

please check the following code, it can help

 public class CountSpace {

    public static void main(String[] args) {

        String word = "S N PRASAD RAO";
        String data[];int k=0;
        for(int i=0;i<data.length;i++){
            if(data[i].equals(" ")){



Convert java.time.LocalDate into java.util.Date type

public static Date convertToTimeZone(Date date, String tzFrom, String tzTo) {
    return Date.from(LocalDateTime.ofInstant(date.toInstant(), ZoneId.of(tzTo)).atZone(ZoneId.of(tzFrom)).toInstant());

JavaScript hashmap equivalent

According to ECMAScript 2015 (ES6), standard JavaScript has a Map implementation. More about which could be found here.

Basic usage:

var myMap = new Map();
var keyString = "a string",
    keyObj = {},
    keyFunc = function () {};

// Setting the values
myMap.set(keyString, "value associated with 'a string'");
myMap.set(keyObj, "value associated with keyObj");
myMap.set(keyFunc, "value associated with keyFunc");

myMap.size; // 3

// Getting the values
myMap.get(keyString);    // "value associated with 'a string'"
myMap.get(keyObj);       // "value associated with keyObj"
myMap.get(keyFunc);      // "value associated with keyFunc"

How do I read a string entered by the user in C?

I found an easy and nice solution:

char*string_acquire(char*s,int size,FILE*stream){
    int i;
    if(s[i]!='\n') while(getchar()!='\n');
    if(s[i]=='\n') s[i]='\0';
    return s;

it's based on fgets but free from '\n' and stdin extra characters (to replace fflush(stdin) that doesn't works on all OS, useful if you have to acquire strings after this).

How to create a BKS (BouncyCastle) format Java Keystore that contains a client certificate chain

Use this manual This guide really helped me. It is important to observe a sequence of certificates in the store. For example: import the lowermost Intermediate CA certificate first and then all the way up to the Root CA certificate.

AngularJs - ng-model in a SELECT

try the following code :

In your controller :

 function myCtrl ($scope) {
      $scope.units = [
         {'id': 10, 'label': 'test1'},
         {'id': 27, 'label': 'test2'},
         {'id': 39, 'label': 'test3'},

   $ $scope.units[0]; // Set by default the value "test1"

In your page :

 <select ng-model="data" ng-options="opt as opt.label for opt in units ">

Working Fiddle

how to read xml file from url using php

$url = ''; $xml = simpleXML_load_file($url,"SimpleXMLElement",LIBXML_NOCDATA);

$url can be php file, as long as the file generate xml format data as output.

How can I position my div at the bottom of its container?

If you do not know the height of child block:

#parent {_x000D_
.child {_x000D_
<div id="parent">_x000D_
    <div class="child">child_x000D_
    </div> _x000D_

If you know the height of the child block add the child block then add padding-top/margin-top:

#parent {_x000D_
.child {_x000D_
<div id="parent">_x000D_
    <div class="child">child_x000D_
    </div> _x000D_

Is a Java hashmap search really O(1)?

Remember that o(1) does not mean that each lookup only examines a single item - it means that the average number of items checked remains constant w.r.t. the number of items in the container. So if it takes on average 4 comparisons to find an item in a container with 100 items, it should also take an average of 4 comparisons to find an item in a container with 10000 items, and for any other number of items (there's always a bit of variance, especially around the points at which the hash table rehashes, and when there's a very small number of items).

So collisions don't prevent the container from having o(1) operations, as long as the average number of keys per bucket remains within a fixed bound.

Where are environment variables stored in the Windows Registry?


reg query "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment"
reg query HKEY_CURRENT_USER\Environment


Get-Item "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\Environment"
Get-Item HKCU:\Environment

Powershell/.NET: (see EnvironmentVariableTarget Enum)


Javascript Date: next month

Instead, try:

var now = new Date();
current = new Date(now.getFullYear(), now.getMonth()+1, 1);

Passing variable from Form to Module in VBA

Siddharth's answer is nice, but relies on globally-scoped variables. There's a better, more OOP-friendly way.

A UserForm is a class module like any other - the only difference is that it has a hidden VB_PredeclaredId attribute set to True, which makes VB create a global-scope object variable named after the class - that's how you can write UserForm1.Show without creating a new instance of the class.

Step away from this, and treat your form as an object instead - expose Property Get members and abstract away the form's controls - the calling code doesn't care about controls anyway:

Option Explicit
Private cancelling As Boolean

Public Property Get UserId() As String
    UserId = txtUserId.Text
End Property

Public Property Get Password() As String
    Password = txtPassword.Text
End Property

Public Property Get IsCancelled() As Boolean
    IsCancelled = cancelling
End Property

Private Sub OkButton_Click()
End Sub

Private Sub CancelButton_Click()
    cancelling = True
End Sub

Private Sub UserForm_QueryClose(Cancel As Integer, CloseMode As Integer)
    If CloseMode = VbQueryClose.vbFormControlMenu Then
        cancelling = True
        Cancel = True
    End If
End Sub

Now the calling code can do this (assuming the UserForm was named LoginPrompt):

With New LoginPrompt
    .Show vbModal
    If .IsCancelled Then Exit Sub
    DoSomething .UserId, .Password
End With

Where DoSomething would be some procedure that requires the two string parameters:

Private Sub DoSomething(ByVal uid As String, ByVal pwd As String)
    'work with the parameter values, regardless of where they came from
End Sub

Jenkins / Hudson environment variables

On Ubuntu I just edit /etc/default/jenkins and add source /etc/profile at the end and it works to me.

New line in Sql Query

You could do Char(13) and Char(10). Cr and Lf.

Char() works in SQL Server, I don't know about other databases.

Android appcompat v7:23

Original answer:

I too tried to change the support library to "23". When I changed the targetSdkVersion to 23, Android Studio reported the following error:

This support library should not use a lower version (22) than the targetSdkVersion (23)

I simply changed:

compile ''


compile ''

Although this fixed my issue, you should not use dynamic versions. After a few hours the new support repository was available and it is currently 23.0.1.

Pro tip:

You can use double quotes and create a ${supportLibVersion} variable for simplicity. Example:

ext {
    supportLibVersion = '23.1.1'

compile "${supportLibVersion}"
compile "${supportLibVersion}"
compile "${supportLibVersion}"
compile "${supportLibVersion}"
compile "${supportLibVersion}"


How to get certain commit from GitHub project

write this to see your commits

git log --oneline

copy the name of the commit you want to go back to. then write:

git checkout "name of the commit"

when you do this, the files of that commit will be replaced with your current files. then you can do whatever you want to these and once you're done, you can write the following command to extract the current files into another newly created branch so whatever you make doesn't have any danger for the previous branch that you extracted a commit from

git checkout -b "name of a branch to extract the files to"

right now, you have the content of a specified commit, into another branch .

Change the mouse cursor on mouse over to anchor-like style

If you want to do this in jQuery instead of CSS, you basically follow the same process.

Assuming you have some <div id="target"></div>, you can use the following code:

$("#target").hover(function() {
}, function() {

and that should do it.

How to git ignore subfolders / subdirectories?

To ignore all subdirectories you can simply use:


This works as of version 1.8.2 of git.

Define global variable with webpack

Use DefinePlugin.

The DefinePlugin allows you to create global constants which can be configured at compile time.

new webpack.DefinePlugin(definitions)


plugins: [
  new webpack.DefinePlugin({
    PRODUCTION: JSON.stringify(true)


console.log(`Environment is in production: ${PRODUCTION}`);

Is there a native jQuery function to switch elements?

Many of these answers are simply wrong for the general case, others are unnecessarily complicated if they in fact even work. The jQuery .before and .after methods do most of what you want to do, but you need a 3rd element the way many swap algorithms work. It's pretty simple - make a temporary DOM element as a placeholder while you move things around. There is no need to look at parents or siblings, and certainly no need to clone...

$.fn.swapWith = function(that) {
  var $this = this;
  var $that = $(that);

  // create temporary placeholder
  var $temp = $("<div>");

  // 3-step swap

  return $this;

1) put the temporary div temp before this

2) move this before that

3) move that after temp

3b) remove temp

Then simply



Detecting when the 'back' button is pressed on a navbar

You should check out the UINavigationBarDelegate Protocol. In this case you might want to use the navigationBar:shouldPopItem: method.

vba listbox multicolumn add

Simplified example (with counter):

With Me.lstbox
    .ColumnCount = 2
    .ColumnWidths = "60;60"
    .List(i, 0) = Company_ID
    .List(i, 1) = Company_name 
    i = i + 1

end with

Make sure to start the counter with 0, not 1 to fill up a listbox.

Using String Format to show decimal up to 2 places or simple integer

If none of the other answers work for you, it may be because you are binding the ContentProperty of a control in the OnLoad function, which means this won't work:

private void UserControl_Load(object sender, RoutedEventArgs e)
  Bind.SetBindingElement(labelName, String.Format("{0:0.00}", PropertyName), Label.ContentProperty) 

The solution is simple: there is a ContentStringFormat property in the xaml. So when you create the label do this:

//if you want the decimal places definite
<Label Content="0" Name="labelName" ContentStringFormat="0.00"/>


//if you want the decimal places to be optional
<Label Content="0" Name="labelName" ContentStringFormat="0.##"/>

how to initialize a char array?

char * msg = new char[65546]();

It's known as value-initialisation, and was introduced in C++03. If you happen to find yourself trapped in a previous decade, then you'll need to use std::fill() (or memset() if you want to pretend it's C).

Note that this won't work for any value other than zero. I think C++0x will offer a way to do that, but I'm a bit behind the times so I can't comment on that.

UPDATE: it seems my ruminations on the past and future of the language aren't entirely accurate; see the comments for corrections.

Is it possible to capture the stdout from the sh DSL command in the pipeline

A short version would be:

echo sh(script: 'ls -al', returnStdout: true).result

SQL ORDER BY multiple columns

Sorting in an ORDER BY is done by the first column, and then by each additional column in the specified statement.

For instance, consider the following data:

Column1    Column2
=======    =======
1          Smith
2          Jones
1          Anderson
3          Andrews

The query

SELECT Column1, Column2 FROM thedata ORDER BY Column1, Column2

would first sort by all of the values in Column1

and then sort the columns by Column2 to produce this:

Column1    Column2
=======    =======
1          Anderson
1          Smith
2          Jones
3          Andrews

In other words, the data is first sorted in Column1 order, and then each subset (Column1 rows that have 1 as their value) are sorted in order of the second column.

The difference between the two statements you posted is that the rows in the first one would be sorted first by prod_price (price order, from lowest to highest), and then by order of name (meaning that if two items have the same price, the one with the lower alpha value for name would be listed first), while the second would sort in name order only (meaning that prices would appear in order based on the prod_name without regard for price).

ORA-01036: illegal variable name/number when running query through C#

I was having the same problem in an application that I was maintaining, among all the adjustments to prepare the environment, I also spent almost an hour banging my head with this error "ORA-01036: illegal variable name / number" until I found out that the application connection was pointed to an outdated database, so the application passed two more parameters to the outdated database procedure causing the error.

Best way to format integer as string with leading zeros?

One-liner alternative to the built-in zfill.

This function takes x and converts it to a string, and adds zeros in the beginning only and only if the length is too short:

def zfill_alternative(x,len=4): return ( (('0'*len)+str(x))[-l:] if len(str(x))<len else str(x) )

To sum it up - build-in: zfill is good enough, but if someone is curious on how to implement this by hand, here is one more example.

Drawable-hdpi, Drawable-mdpi, Drawable-ldpi Android

I got one good solution. Here I have attached it as the image below. So try it. It may be helpful to you...!

Enter image description here

What is the size of column of int(11) in mysql in bytes?

In MySQL integer int(11) has size is 4 bytes which equals 32 bit.

Signed value is : -2^(32-1) to 0 to 2^(32-1)-1 = -2147483648 to 0 to 2147483647

Unsigned values is : 0 to 2^32-1 = 0 to 4294967295

sql delete statement where date is greater than 30 days

To delete records from a table that have a datetime value in Date_column older than 30 days use this query:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < GETDATE() - 30

...or this:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < DATEADD(dd,-30,GETDATE())

To delete records from a table that have a datetime value in Date_column older than 12 hours:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < DATEADD(hh,-12,GETDATE())

To delete records from a table that have a datetime value in Date_column older than 15 minutes:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < DATEADD(mi,-15,GETDATE())


How can I disable a button on a jQuery UI dialog?

You can also use the not now documented disabled attribute:

    buttons: [
        text: "Confirm",
        disabled: true,
        id: "my-button-1"
        text: "Cancel",
        id: "my-button-2",
        click: function(){            


To enable after dialog has opened, use:

$("#my-button-1").attr('disabled', false);


Check if two unordered lists are equal

What about getting the string representation of the lists and comparing them ?

>>> l1 = ['one', 'two', 'three']
>>> l2 = ['one', 'two', 'three']
>>> l3 = ['one', 'three', 'two']
>>> print str(l1) == str(l2)
>>> print str(l1) == str(l3)

Xcode 9 Swift Language Version (SWIFT_VERSION)

I just got this after creating a new Objective-C project in Xcode 10, after I added a Core Data model file to the project.

I found two ways to fix this:

  1. The Easy Way: Open the Core Data model's File Inspector (??-1) and change the language from Swift to Objective-C

Change Core Data model language

  1. Longer and more dangerous method

The model contains a "contents" file with this line:

<model type="" documentVersion="1.0" lastSavedToolsVersion="14460.32" systemVersion="17G5019" minimumToolsVersion="Automatic" sourceLanguage="Swift" userDefinedModelVersionIdentifier="">

In there is a sourceLanguage="Swift" entry. Change it to sourceLanguage="Objective-C" and the error goes away.

To find the "contents" file, right click on the .xcdatamodeld in Xcode and do "Show in Finder". Right-click on the actual (Finder) file and do "Show Package Contents"

Also: Changing the model's language will stop Xcode from generating managed object subclass files in Swift.

How to measure elapsed time

Even better!

long tStart = System.nanoTime();
long tEnd = System.nanoTime();
long tRes = tEnd - tStart; // time in nanoseconds

Read the documentation about nanoTime()!

Check file uploaded is in csv format

You can't always rely on MIME type..

According to:

text/comma-separated-values, text/csv, application/csv, application/excel, application/, application/vnd.msexcel, text/anytext

There are various MIME types for CSV.

Your probably best of checking extension, again not very reliable, but for your application it may be fine.

$info = pathinfo($_FILES['uploadedfile']['tmp_name']);

if($info['extension'] == 'csv'){
 // Good to go

Code untested.

Autoplay an audio with HTML5 embed tag while the player is invisible

"Sensitive" era

Modern browsers today seem to block (by default) these autoplay features. They are somewhat treated as pop-ops. Very intrusive. So yeah, users now have the complete control on when the sounds are played. [1,2,3]

HTML5 era

<audio controls autoplay loop hidden>
    <source src="audio.mp3" type="audio/mpeg">

Early days of HTML

<embed src="audio.mp3" style="visibility:hidden" />


  1. Jer Noble, New <video> Policies for iOS, WebKit, link
  2. Allow or block media autoplay in Firefox, FireFox Help, link
  3. Mounir Lamouri, Unified autoplay, Chromium Blog, link
  4. Embedded content, World Wide Web Consortium, link

How do I get the current year using SQL on Oracle?

Since we are doing this one to death - you don't have to specify a year:

select * from demo
where  somedate between to_date('01/01 00:00:00', 'DD/MM HH24:MI:SS')
                and     to_date('31/12 23:59:59', 'DD/MM HH24:MI:SS');

However the accepted answer by FerranB makes more sense if you want to specify all date values that fall within the current year.

Multi-line bash commands in makefile

The ONESHELL directive allows to write multiple line recipes to be executed in the same shell invocation.

all: foo

SOURCE_FILES = $(shell find . -name '*.c')

    for F in $^; do
    gcc "$${FILES[@]}" -o $@

There is a drawback though : special prefix characters (‘@’, ‘-’, and ‘+’) are interpreted differently.

When is assembly faster than C?

In my job, there are three reasons for me to know and use assembly. In order of importance:

  1. Debugging - I often get library code that has bugs or incomplete documentation. I figure out what it's doing by stepping in at the assembly level. I have to do this about once a week. I also use it as a tool to debug problems in which my eyes don't spot the idiomatic error in C/C++/C#. Looking at the assembly gets past that.

  2. Optimizing - the compiler does fairly well in optimizing, but I play in a different ballpark than most. I write image processing code that usually starts with code that looks like this:

    for (int y=0; y < imageHeight; y++) {
        for (int x=0; x < imageWidth; x++) {
           // do something

    the "do something part" typically happens on the order of several million times (ie, between 3 and 30). By scraping cycles in that "do something" phase, the performance gains are hugely magnified. I don't usually start there - I usually start by writing the code to work first, then do my best to refactor the C to be naturally better (better algorithm, less load in the loop etc). I usually need to read assembly to see what's going on and rarely need to write it. I do this maybe every two or three months.

  3. doing something the language won't let me. These include - getting the processor architecture and specific processor features, accessing flags not in the CPU (man, I really wish C gave you access to the carry flag), etc. I do this maybe once a year or two years.

How to return the output of stored procedure into a variable in sql server

That depends on the nature of the information you want to return.

If it is a single integer value, you can use the return statement

 create proc myproc
     return 1
 declare @i int
 exec @i = myproc

If you have a non integer value, or a number of scalar values, you can use output parameters

create proc myproc
  @a int output,
  @b varchar(50) output
  select @a = 1, @b='hello'
declare @i int, @j varchar(50)
exec myproc @i output, @j output

If you want to return a dataset, you can use insert exec

create proc myproc
     select name from sysobjects

declare @t table (name varchar(100))
insert @t (name)
exec myproc

You can even return a cursor but that's just horrid so I shan't give an example :)

How can I make a list of installed packages in a certain virtualenv?

In Python3

pip list

Empty venv is

Package    Version
---------- ------- 
pip        19.2.3 
setuptools 41.2.0

To start a new environment

python3 -m venv your_foldername_here


cd your_foldername_here
source bin/activate



You can also stand in the folder and give the virtual environment a name/folder (python3 -m venv name_of_venv).

Venv is a subset of virtualenv that is shipped with Python after 3.3.

Add newline to VBA or Visual Basic 6

Visual Basic has built-in constants for newlines:

vbCr = Chr$(13) = CR (carriage-return character) - used by Mac OS and Apple II family

vbLf = Chr$(10) = LF (line-feed character) - used by Linux and Mac OS X

vbCrLf = Chr$(13) & Chr$(10) = CRLF (carriage-return followed by line-feed) - used by Windows

vbNewLine = the same as vbCrLf

Create Generic method constraining T to an Enum

If it's ok to use direct casting afterwards, I guess you can use the System.Enum base class in your method, wherever necessary. You just need to replace the type parameters carefully. So the method implementation would be like:

public static class EnumUtils
    public static Enum GetEnumFromString(string value, Enum defaultValue)
        if (string.IsNullOrEmpty(value)) return defaultValue;
        foreach (Enum item in Enum.GetValues(defaultValue.GetType()))
            if (item.ToString().ToLower().Equals(value.Trim().ToLower())) return item;
        return defaultValue;

Then you can use it like:

var parsedOutput = (YourEnum)EnumUtils.GetEnumFromString(someString, YourEnum.DefaultValue);

Passing a dictionary to a function as keyword parameters

Here ya go - works just any other iterable:

d = {'param' : 'test'}

def f(dictionary):
    for key in dictionary:
        print key


Countdown timer using Moment js

Here are some other solutions. No need to use additional plugins.

Snippets down below uses .subtract API and requires moment 2.1.0+

Snippets are also available in here

Formatting with the .format API:

const duration = moment.duration(9, 's');

const intervalId = setInterval(() => {
  duration.subtract(1, "s");

  const inMilliseconds = duration.asMilliseconds();

  // "mm:ss:SS" will include milliseconds

  if (inMilliseconds !== 0) return;

  console.warn("Times up!");
}, 1000);
<script src=""></script>

Manuel formatting by .hours, .minutes and .seconds API in a template string

const duration = moment.duration(9, 's');

const intervalId = setInterval(() => {
  duration.subtract(1, "s");

  // `:${duration.milliseconds()}` to add milliseconds

  if (duration.asMilliseconds() !== 0) return;

  console.warn("Times up!");
}, 1000);
<script src=""></script>

The name 'ConfigurationManager' does not exist in the current context

Adding this answer, as none of the suggested solutions works for me.

  1. Right-click on references tab to add reference.
  2. Click on Assemblies tab
  3. Search for 'System.Configuration'
  4. Click OK.

Check if a row exists using old mysql_* API

If you just want to compare only one row with $lactureName then use following

function checkLectureStatus($lectureName)
 $con = connectvar();
 mysql_select_db("mydatabase", $con);
 $result = mysql_query("SELECT * FROM preditors_assigned WHERE lecture_name='$lectureName'");
  if(mysql_num_rows($result) > 0)
         return "Assigned";
        return "Available";

DataGridView - Focus a specific cell

Set the Current Cell like:

DataGridView1.CurrentCell = DataGridView1.Rows[rowindex].Cells[columnindex]


DataGridView1.CurrentCell = DataGridView1.Item("ColumnName", 5)

and you can directly focus with Editing by:


How to convert a List<String> into a comma separated string without iterating List explicitly

With Java 8:

String csv = String.join(",", ids);

With Java 7-, there is a dirty way (note: it works only if you don't insert strings which contain ", " in your list) - obviously, List#toString will perform a loop to create idList but it does not appear in your code:

List<String> ids = new ArrayList<String>();
String idList = ids.toString();
String csv = idList.substring(1, idList.length() - 1).replace(", ", ",");

How do you create a daemon in Python?

Here's my basic 'Howdy World' Python daemon that I start with, when I'm developing a new daemon application.

import time
from daemon import runner

class App():
    def __init__(self):
        self.stdin_path = '/dev/null'
        self.stdout_path = '/dev/tty'
        self.stderr_path = '/dev/tty'
        self.pidfile_path =  '/tmp/'
        self.pidfile_timeout = 5
    def run(self):
        while True:
            print("Howdy!  Gig'em!  Whoop!")

app = App()
daemon_runner = runner.DaemonRunner(app)

Note that you'll need the python-daemon library. You can install it by:

pip install python-daemon

Then just start it with ./ start, and stop it with ./ stop.

Using Apache httpclient for https

I put together this test app to reproduce the issue using the HTTP testing framework from the Apache HttpClient package:

ClassLoader cl = HCTest.class.getClassLoader();
URL url = cl.getResource("test.keystore");
KeyStore keystore  = KeyStore.getInstance("jks");
char[] pwd = "nopassword".toCharArray();
keystore.load(url.openStream(), pwd);

TrustManagerFactory tmf = TrustManagerFactory.getInstance(
TrustManager[] tm = tmf.getTrustManagers();

KeyManagerFactory kmfactory = KeyManagerFactory.getInstance(
kmfactory.init(keystore, pwd);
KeyManager[] km = kmfactory.getKeyManagers();

SSLContext sslcontext = SSLContext.getInstance("TLS");
sslcontext.init(km, tm, null);

LocalTestServer localServer = new LocalTestServer(sslcontext);

try {

    DefaultHttpClient httpclient = new DefaultHttpClient();
    TrustStrategy trustStrategy = new TrustStrategy() {

        public boolean isTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            for (X509Certificate cert: chain) {
            return false;


    SSLSocketFactory sslsf = new SSLSocketFactory("TLS", null, null, keystore, null,
            trustStrategy, new AllowAllHostnameVerifier());
    Scheme https = new Scheme("https", 443, sslsf);

    InetSocketAddress address = localServer.getServiceAddress();
    HttpHost target1 = new HttpHost(address.getHostName(), address.getPort(), "https");
    HttpGet httpget1 = new HttpGet("/random/100");
    HttpResponse response1 = httpclient.execute(target1, httpget1);
    HttpEntity entity1 = response1.getEntity();
    HttpHost target2 = new HttpHost("", 443, "https");
    HttpGet httpget2 = new HttpGet("/");
    HttpResponse response2 = httpclient.execute(target2, httpget2);
    HttpEntity entity2 = response2.getEntity();
} finally {

Even though, Sun's JSSE implementation appears to always read the trust material from the default trust store for some reason, it does not seem to get added to the SSL context and to impact the process of trust verification during the SSL handshake.

Here's the output of the test app. As you can see, the first request succeeds whereas the second fails as the connection to is rejected as untrusted.

  Version: V1
  Subject: CN=Simple Test Http Server, OU=Jakarta HttpClient Project, O=Apache Software Foundation, L=Unknown, ST=Unknown, C=Unknown
  Signature Algorithm: SHA1withDSA, OID = 1.2.840.10040.4.3

  Key:  Sun DSA Public Key
    p:     fd7f5381 1d751229 52df4a9c 2eece4e7 f611b752 3cef4400 c31e3f80 b6512669
    455d4022 51fb593d 8d58fabf c5f5ba30 f6cb9b55 6cd7813b 801d346f f26660b7
    6b9950a5 a49f9fe8 047b1022 c24fbba9 d7feb7c6 1bf83b57 e7c6a8a6 150f04fb
    83f6d3c5 1ec30235 54135a16 9132f675 f3ae2b61 d72aeff2 2203199d d14801c7
    q:     9760508f 15230bcc b292b982 a2eb840b f0581cf5
    g:     f7e1a085 d69b3dde cbbcab5c 36b857b9 7994afbb fa3aea82 f9574c0b 3d078267
    5159578e bad4594f e6710710 8180b449 167123e8 4c281613 b7cf0932 8cc8a6e1
    3c167a8b 547c8d28 e0a3ae1e 2bb3a675 916ea37f 0bfa2135 62f1fb62 7a01243b
    cca4f1be a8519089 a883dfe1 5ae59f06 928b665e 807b5525 64014c3b fecf492a

    f0cc639f 702fd3b1 03fa8fa6 676c3756 ea505448 23cd1147 fdfa2d7f 662f7c59
    a02ddc1a fd76673e 25210344 cebbc0e7 6250fff1 a814a59f 30ff5c7e c4f186d8
    f0fd346c 29ea270d b054c040 c74a9fc0 55a7020f eacf9f66 a0d86d04 4f4d23de
    7f1d681f 45c4c674 5762b71b 808ded17 05b74baf 8de3c4ab 2ef662e3 053af09e

  Validity: [From: Sat Dec 11 14:48:35 CET 2004,
               To: Tue Dec 09 14:48:35 CET 2014]
  Issuer: CN=Simple Test Http Server, OU=Jakarta HttpClient Project, O=Apache Software Foundation, L=Unknown, ST=Unknown, C=Unknown
  SerialNumber: [    41bafab3]

  Algorithm: [SHA1withDSA]
0000: 30 2D 02 15 00 85 BE 6B   D0 91 EF 34 72 05 FF 1A  0-.....k...4r...
0010: DB F6 DE BF 92 53 9B 14   27 02 14 37 8D E8 CB AC  .....S..'..7....
0020: 4E 6C 93 F2 1F 7D 20 A1   2D 6F 80 5F 58 AE 33     Nl.... .-o._X.3

HTTP/1.1 200 OK
  Version: V3
  Subject:, OU=" Production Security Services", O="VeriSign, Inc.", STREET=487 East Middlefield Road, L=Mountain View, ST=California, OID., C=US, SERIALNUMBER=2497886, OID."V1.0, Clause 5.(b)", OID., OID.
  Signature Algorithm: SHA1withRSA, OID = 1.2.840.113549.1.1.5

  Key:  Sun RSA public key, 2048 bits
  modulus: 20699622354183393041832954221256409980425015218949582822286196083815087464214375375678538878841956356687753084333860738385445545061253653910861690581771234068858443439641948884498053425403458465980515883570440998475638309355278206558031134532548167239684215445939526428677429035048018486881592078320341210422026566944903775926801017506416629554190534665876551381066249522794321313235316733139718653035476771717662585319643139144923795822646805045585537550376512087897918635167815735560529881178122744633480557211052246428978388768010050150525266771462988042507883304193993556759733514505590387262811565107773578140271
  public exponent: 65537
  Validity: [From: Wed May 26 02:00:00 CEST 2010,
               To: Sat May 26 01:59:59 CEST 2012]
  Issuer: CN=VeriSign Class 3 Extended Validation SSL SGC CA, OU=Terms of use at (c)06, OU=VeriSign Trust Network, O="VeriSign, Inc.", C=US
  SerialNumber: [    53d2bef9 24a7245e 83ca01e4 6caa2477]

Certificate Extensions: 10
[1]: ObjectId: Criticality=false
AuthorityInfoAccess [
   accessLocation: URIName:, accessMethod:
   accessLocation: URIName:]


Exception in thread "main" peer not authenticated
    at org.apache.http.conn.ssl.AbstractVerifier.verify(
    at org.apache.http.conn.ssl.SSLSocketFactory.createLayeredSocket(

How can I search (case-insensitive) in a column using LIKE wildcard?

SELECT name 
       FROM gallery 
       WHERE CONVERT(name USING utf8) LIKE _utf8 '%$q%' 
       GROUP BY name COLLATE utf8_general_ci LIMIT 5 

Mongoose, Select a specific field with find

DB Data

    "_id": "70001",
    "name": "peter"
    "_id": "70002",
    "name": "john"
    "_id": "70003",
    "name": "joseph"


  "_id": 0,
  "name": 1


    "name": "peter"
    "name": "john"
    "name": "joseph"

Working sample playground