Programs & Examples On #Region management

Remove columns from dataframe where ALL values are NA

janitor::remove_constant() does this very nicely.

CSS center content inside div

The problem is that you assigned a fixed width to your .wrap DIV. The DIV itself is centered (you can see that when you add a border to it) but the DIV is just too wide. In other words the content does not fill the whole width of the DIV.

To solve the problem you have to make sure, that the .wrap DIV is only as wide as it's content.

To achieve that you have to remove the floating in the content elements and set the display property of the block levels elements to inline:

#partners .wrap {
 display: inline;

.wrap { margin: 0 auto; position: relative;}

#partners h2 {
color: #A6A5A5;
font-weight: normal;
margin: 2px 15px 0 0;
display: inline;

#partners ul {
display: inline;

#partners li {display: inline}

ul { list-style-position: outside; list-style-type: none; }

How to convert An NSInteger to an int?

If you want to do this inline, just cast the NSUInteger or NSInteger to an int:

int i = -1;
NSUInteger row = 100;
i > row // true, since the signed int is implicitly converted to an unsigned int
i > (int)row // false

Bulk Insert Correctly Quoted CSV File in SQL Server

I had this same problem, and I didn't want to have to go the SSIS route, so I found a PowerShell script that is easy to run and handles the case of the quotes with the comma in that particular field:

Source Code and DLL for the PowerShell Script:

Here's a blog that explains the usage:

When should I use Kruskal as opposed to Prim (and vice versa)?

Kruskal can have better performance if the edges can be sorted in linear time, or are already sorted.

Prim's better if the number of edges to vertices is high.

How to Set Focus on JTextField?

It was not working for me when tried to use:


But - I found a solution ! Very primitive, but works.

Just jump to the field by java.awt.Robot using key "Tab". For example:

Robot robot = new Robot();

If you should press multiple times on "Tab" to get your Component you can use below method:



public static void pressTab(int amountOfClickes)
    SwingUtilities.invokeLater(new Runnable()
        public void run()
                Robot robot = new Robot();
                int i = amountOfClickes;
                while (i-- > 0)
            catch (AWTException e)
                System.out.println("Failed to use Robot, got exception: " + e.getMessage());

If your Component location is dynamic, you can run over the while loop without limitation, but add some focus listener on the component, to stop the loop once arrived to it.

Python time measure function

There is an easy tool for timing.

It can work like a decorator:

from pytimer import Timer
def matmul(a,b, times=100):
    for i in range(times):,b)        



It can also work like a plug-in timer with namespace control(helpful if you are inserting it to a function which has a lot of codes and may be called anywhere else).

timer = Timer()                                           
def any_function():                                       

    for i in range(10):                                   

        timer.reset()                                    ,1000)), np.zeros((1000,500)))
        timer.checkpoint('block1')                        ,1000)), np.zeros((1000,500))),1000)), np.zeros((1000,500)))
        timer.checkpoint('block2')                       ,1000)), np.zeros((1000,1000)))

    for j in range(20):                                  ,1000)), np.zeros((1000,500)))

for i in range(2):                                        


========Timing Summary of Default Timer========
========Timing Summary of Default Timer========

Hope it will help

Export from pandas to_excel without row names (index)?

You need to set index=False in to_excel in order for it to not write the index column out, this semantic is followed in other Pandas IO tools, see and

Razor HtmlHelper Extensions (or other namespaces for views) Not Found

Since the Beta, Razor uses a different config section for globally defining namespace imports. In your Views\Web.config file you should add the following:

  <sectionGroup name="system.web.webPages.razor" type="System.Web.WebPages.Razor.Configuration.RazorWebSectionGroup, System.Web.WebPages.Razor, Version=, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
    <section name="host" type="System.Web.WebPages.Razor.Configuration.HostSection, System.Web.WebPages.Razor, Version=, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />
    <section name="pages" type="System.Web.WebPages.Razor.Configuration.RazorPagesSection, System.Web.WebPages.Razor, Version=, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />

  <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
  <pages pageBaseType="System.Web.Mvc.WebViewPage">
      <add namespace="System.Web.Mvc" />
      <add namespace="System.Web.Mvc.Ajax" />
      <add namespace="System.Web.Mvc.Html" />
      <add namespace="System.Web.Routing" />
      <!-- Your namespace here -->

Use the MVC 3 upgrade tool to automatically ensure you have the right config values.

Note that you might need to close and reopen the file for the changes to be picked up by the editor.

Mysql database sync between two databases

Replication is not very hard to create.

Here's some good tutorials:

Here some simple rules you will have to keep in mind (there's more of course but that is the main concept):

  1. Setup 1 server (master) for writing data.
  2. Setup 1 or more servers (slaves) for reading data.

This way, you will avoid errors.

For example: If your script insert into the same tables on both master and slave, you will have duplicate primary key conflict.

You can view the "slave" as a "backup" server which hold the same information as the master but cannot add data directly, only follow what the master server instructions.

NOTE: Of course you can read from the master and you can write to the slave but make sure you don't write to the same tables (master to slave and slave to master).

I would recommend to monitor your servers to make sure everything is fine.

Let me know if you need additional help

C++ - Hold the console window open?

How about std::cin.get(); ?

Also, if you're using Visual Studio, you can run without debugging (CTRL-F5 by default) and it won't close the console at the end. If you run it with debugging, you could always put a breakpoint at the closing brace of main().

What is the best way to conditionally apply a class?

If you don't want to put CSS class names into Controller like I do, here is an old trick that I use since pre-v1 days. We can write an expression that evaluates directly to a class name selected, no custom directives are necessary:

ng:class="{true:'selected', false:''}[$index==selectedIndex]"

Please note the old syntax with colon.

There is also a new better way of applying classes conditionally, like:

ng-class="{selected: $index==selectedIndex}"

Angular now supports expressions that return an object. Each property (name) of this object is now considered as a class name and is applied depending on its value.

However these ways are not functionally equal. Here is an example:

ng-class="{admin:'enabled', moderator:'disabled', '':'hidden'}[user.role]"

We could therefore reuse existing CSS classes by basically mapping a model property to a class name and at the same time keep CSS classes out of Controller code.

Pie chart with jQuery

A few others that have not been mentioned:

For mini pies, lines and bars, Peity is brilliant, simple, tiny, fast, uses really elegant markup.

I'm not sure of it's relationship with Flot (given its name), but Flotr2 is pretty good, certainly does better pies than Flot.

Bluff produces nice-looking line graphs, but I had a bit of trouble with its pies.

Not what I was after, but another commercial product (much like Highcharts) is TeeChart.

Scanner is never closed

According to the Javadoc of Scanner, it closes the stream when you call it's close method. Generally speaking, the code that creates a resource is also responsible for closing it. was not instantiated by by your code, but by the VM. So in this case it's safe to not close the Scanner, ignore the warning and add a comment why you ignore it. The VM will take care of closing it if needed.

(Offtopic: instead of "amount", the word "number" would be more appropriate to use for a number of players. English is not my native language (I'm Dutch) and I used to make exactly the same mistake.)

phpmailer error "Could not instantiate mail function"

If you are sending file attachments and your code works for small attachments but fails for large attachments:

If you get the error "Could not instantiate mail function" error when you try to send large emails and your PHP error log contains the message "Cannot send message: Too big" then your mail transfer agent (sendmail, postfix, exim, etc) is refusing to deliver these emails.

The solution is to configure the MTA to allow larger attachments. But this is not always possible. The alternate solution is to use SMTP. You will need access to a SMTP server (and login credentials if your SMTP server requires authentication):

$mail             = new PHPMailer();
$mail->IsSMTP();                           // telling the class to use SMTP
$mail->SMTPAuth   = true;                  // enable SMTP authentication
$mail->Host       = ""; // set the SMTP server
$mail->Port       = 26;                    // set the SMTP port
$mail->Username   = "yourname@yourdomain"; // SMTP account username
$mail->Password   = "yourpassword";        // SMTP account password

PHPMailer defaults to using PHP mail() function which uses settings from php.ini which normally defaults to use sendmail (or something similar). In the above example we override the default behavior.

Random Number Between 2 Double Numbers

Use a static Random or the numbers tend to repeat in tight/fast loops due to the system clock seeding them.

public static class RandomNumbers
    private static Random random = new Random();
    // double between min and the max number
    public static double RandomDouble(int min, int max) 
        return (random.NextDouble() * (max - min)) + min;
    // double between 0 and the max number
    public static double RandomDouble(int max) 
        return (random.NextDouble() * max);
    // int between the min and the max number
    public static int RandomInt(int min, int max) 
        return random.Next(min, max + 1);
    // int between 0 and the max number
    public static int RandomInt(int max) 
        return random.Next(max + 1);

See also :

Creating and Naming Worksheet in Excel VBA

Are you using an error handler? If you're ignoring errors and try to name a sheet the same as an existing sheet or a name with invalid characters, it could be just skipping over that line. See the CleanSheetName function here

for a list of invalid characters that you may want to check for.


Other things to try: Fully qualified references, throwing in a Doevents, code cleaning. This code qualifies your Sheets reference to ThisWorkbook (you can change it to ActiveWorkbook if that suits). It also adds a thousand DoEvents (stupid overkill, but if something's taking a while to get done, this will allow it to - you may only need one DoEvents if this actually fixes anything).

Dim WS As Worksheet
Dim i As Long

With ThisWorkbook
    Set WS = .Worksheets.Add(After:=.Sheets(.Sheets.Count))
End With

For i = 1 To 1000
Next i

WS.Name = txtSheetName.Value

Finally, whenever I have a goofy VBA problem that just doesn't make sense, I use Rob Bovey's CodeCleaner. It's an add-in that exports all of your modules to text files then re-imports them. You can do it manually too. This process cleans out any corrupted p-code that's hanging around.

Force uninstall of Visual Studio

I was running in to the same issue, but have just managed a full uninstall by means of trusty old CMD:

D:\vs_ultimate.exe /uninstall /force

Where D: is the location of your installation media (mounted iso, etc).

You could also pass /passive (no user input required - just progress displayed) or /quiet to the above command line.

EDIT: Adding link below to MSDN article mentioning that this forcibly removes ALL installed components.

Also, to ensure link rot doesn't invalidate this, adding brief text below from original article.

Starting with Visual Studio 2013, you can forcibly remove almost all components. A few core components – like the .NET Framework and VC runtimes – are left behind because of their ubiquity, though you can remove those separately from Programs and Features if you really want.

Warning: This will remove all components regardless of whether other products require them. This may cause other products to function incorrectly or not function at all.

Good luck!

Authorize a non-admin developer in Xcode / Mac OS

Ned Deily's solution works perfectly fine, provided your user is allowed to sudo.

If he's not, you can su to an admin account, then use his dscl . append /Groups/_developer GroupMembership $user, where $user is the username.

However, I mistakenly thought it did not because I wrongly typed in the user's name in the command and it silently fails.

Therefore, after entering this command, you should proof-check it. This will check if $user is in $group, where the variables represent respectively the user name and the group name.

dsmemberutil checkmembership -U $user -G $group

This command will either print the message user is not a member of the group or user is a member of the group.

Detecting IE11 using CSS Capability/Feature Detection

To target IE10 and IE11 only (and not Edge):

@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {  
   /* add your IE10-IE11 css here */   

Bootstrap Modal immediately disappearing

in case anyone using codeigniter 3 bootstrap with datatable.

below is my fix in config/ci_boostrap.php

//lib.min.js has conflict with datatables.js and i removed it replace with jquery.js

Excel VBA Code: Compile Error in x64 Version ('PtrSafe' attribute required)

I think all you need to do for your function is just add PtrSafe: i.e. the first line of your first function should look like this:

Private Declare PtrSafe Function swe_azalt Lib "swedll32.dll" ......

Insert a new row into DataTable

// create table
var dt = new System.Data.DataTable("tableName");

// create fields
dt.Columns.Add("field1", typeof(int));
dt.Columns.Add("field2", typeof(string));
dt.Columns.Add("field3", typeof(DateTime));

// insert row values
dt.Rows.Add(new Object[]{

Converting Numpy Array to OpenCV Array

This is what worked for me...

import cv2
import numpy as np

#Created an image (really an ndarray) with three channels 
new_image = np.ndarray((3, num_rows, num_cols), dtype=int)

#Did manipulations for my project where my array values went way over 255
#Eventually returned numbers to between 0 and 255

#Converted the datatype to np.uint8
new_image = new_image.astype(np.uint8)

#Separated the channels in my new image
new_image_red, new_image_green, new_image_blue = new_image

#Stacked the channels
new_rgb = np.dstack([new_image_red, new_image_green, new_image_blue])

#Displayed the image
cv2.imshow("WindowNameHere", new_rgbrgb)

Increase bootstrap dropdown menu width

Usually the desire is to match the menu width to the width of the dropdown parent. This can be achieved easily like so:

.dropdown-menu {

HTML5 Canvas vs. SVG vs. div

While googling I find a good explanation about usage and compression of SVG and Canvas at

Hope it helps:

  • SVG, like HTML, uses retained rendering: When we want to draw a rectangle on the screen, we declaratively use a element in our DOM. The browser will then draw a rectangle, but it will also create an in-memory SVGRectElement object that represents the rectangle. This object is something that sticks around for us to manipulate – it is retained. We can assign different positions and sizes to it over time. We can also attach event listeners to make it interactive.
  • Canvas uses immediate rendering: When we draw a rectangle, the browser immediately renders a rectangle on the screen, but there is never going to be any "rectangle object" that represents it. There's just a bunch of pixels in the canvas buffer. We can't move the rectangle. We can only draw another rectangle. We can't respond to clicks or other events on the rectangle. We can only respond to events on the whole canvas.

So canvas is a more low-level, restrictive API than SVG. But there's a flipside to that, which is that with canvas you can do more with the same amount of resources. Because the browser does not have to create and maintain the in-memory object graph of all the things we have drawn, it needs less memory and computation resources to draw the same visual scene. If you have a very large and complex visualization to draw, Canvas may be your ticket.

cannot resolve symbol javafx.application in IntelliJ Idea IDE

This should be your perfect solution. Try and enjoy. If some command does not work properly that means if you get any error, try to solve it yourself. I have given you the main thing you need. If your application is in a different location, or your system architecture is different, solve it yourself. It's very easy to do it. Just follow my given solution.

Step 0:

sudo apt-get install openjdk-8-jre

Step: 1

sudo apt-get install openjfx

Step 2:

sudo cp /usr/share/java/openjfx/jre/lib/ext/* /usr/lib/jvm/java-1.8.0-openjdk-amd64/lib

Step 3:

sudo cp /usr/share/java/openjfx/lib/* /usr/lib/jvm/java-1.8.0-openjdk-amd64/lib

Step 4:

sudo chmod 777 -R /usr/lib/jvm/java-1.8.0-openjdk-amd64

now open a new project or rebuild your project. Good luck.

How to make MySQL handle UTF-8 properly

The short answer: Use utf8mb4 in 4 places:

  • The bytes in your client are utf8, not latin1/cp1251/etc.
  • SET NAMES utf8mb4 or something equivalent when establishing the client's connection to MySQL
  • CHARACTER SET utf8mb4 on all tables/columns -- except columns that are strictly ascii/hex/country_code/zip_code/etc.
  • <meta charset charset=UTF-8> if you are outputting to HTML. (Yes the spelling is different here.)

More info ;
UTF8 all the way

The above links provide the "detailed canonical answer is required to address all the concerns". -- There is a space limit on this forum.


In addition to CHARACTER SET utf8mb4 containing "all" the world's characters, COLLATION utf8mb4_unicode_520_ci is arguable the 'best all-around' collation to use. (There are also Turkish, Spanish, etc, collations for those who want the nuances in those languages.)

Selecting multiple items in ListView

Step 1: setAdapter to your listview.

 listView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice, GENRES)); 

Step 2: set choice mode for listview .The second line of below code represents which checkbox should be checked.

listView.setItemChecked(2, true);


 private static  String[] GENRES = new String[] {
        "Action", "Adventure", "Animation", "Children", "Comedy", "Documentary", "Drama",
        "Foreign", "History", "Independent", "Romance", "Sci-Fi", "Television", "Thriller"

Step 3: Checked views are returned in SparseBooleanArray, so you might use the below code to get key or values.The below sample are simply displayed selected names in a single String.

    public void onItemClick(AdapterView<?> adapter, View arg1, int arg2, long arg3)

    SparseBooleanArray sp=getListView().getCheckedItemPositions();

    String str="";
    for(int i=0;i<sp.size();i++)
    Toast.makeText(this, ""+str, Toast.LENGTH_SHORT).show();


Custom method names in ASP.NET Web API

I am days into the MVC4 world.

For what its worth, I have a SitesAPIController, and I needed a custom method, that could be called like:


With different values for the last parameter to get record with different dispositions.

What Finally worked for me was:

The method in the SitesAPIController:

// GET api/SitesAPI/Disposition/1
public Site Disposition(int disposition)
    Site site = db.Sites.Where(s => s.Disposition == disposition).First();
    return site;

And this in the WebApiConfig.cs

// this was already there
    name: "DefaultApi",
    routeTemplate: "api/{controller}/{id}",
    defaults: new { id = RouteParameter.Optional }

// this i added
    name: "Action",
    routeTemplate: "api/{controller}/{action}/{disposition}"

For as long as I was naming the {disposition} as {id} i was encountering:

"Message": "No HTTP resource was found that matches the request URI 'http://localhost:9000/api/SitesAPI/Disposition/0'.",
"MessageDetail": "No action was found on the controller 'SitesAPI' that matches the request."

When I renamed it to {disposition} it started working. So apparently the parameter name is matched with the value in the placeholder.

Feel free to edit this answer to make it more accurate/explanatory.

Saving the PuTTY session logging

This is a bit confusing, but follow these steps to save the session.

  1. Category -> Session -> enter public IP in Host and 22 in port.
  2. Connection -> SSH -> Auth -> select the .ppk file
  3. Category -> Session -> enter a name in Saved Session -> Click Save

To open the session, double click on particular saved session.

Add Marker function with Google Maps API

function initialize() {
    var location = new google.maps.LatLng(44.5403, -78.5463);
    var mapCanvas = document.getElementById('map_canvas');
    var map_options = {
      center: location,
      zoom: 15,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    var map = new google.maps.Map(map_canvas, map_options);

    new google.maps.Marker({
        position: location,
        map: map
google.maps.event.addDomListener(window, 'load', initialize);

How do you migrate an IIS 7 site to another server?

I can't comment up thread due to lack of rep. Another commenter stated they couldn't migrate from a lower version to a higher version of IIS. This is true if you don't merge some files, but if you do you can as I just migrated my IIS 7.5 site to IIS 8.0 using the answer posted by chews.

When the export is created (II7.5), there are two key files (administration.config and applicationHost.config) which have references to resources on the IIS7.5 server. For example, a DLL will be referred with a public key and version specific to 7.5. These are NOT the same on the IIS8 server. The feature configuration may differ as well (I ensured mine were identical). There are some new features in 8 which will never exist in 7.5.

If you are brave enough to merge the two files - it will work. I had to uninstall IIS once because I messed it up, but got it the second time.

I used a merge tool (Beyond Compare) and without something equivalent it would be a huge PITA - but was pretty easy with a good diff tool (five minutes).

To do the merge, the 8.0 files need to be diffed against the exported 7.5 files BEFORE an import is attempted. For the most part, the 8.0 files need to overwrite the server specific stuff in the exported 7.5 files, while leaving the site/app pool specific stuff.

I found that administration.config was almost identical, sans the version info of many entries. This one was easy.

The applicationHost.config has a lot more differences. Some entries are ordered differently, but otherwise identical, so you will have to pick through each difference and figure it out.

I put my 7.5 export files in the System32\inetsrv\config\Export folder prior to merging.

I merged FROM folder System32\inetsrv\config to folder System32\inetsrv\config\Export for both files I mentioned above. I pushed over everything in the FROM files except site specific tags/elements (e.g. applicationPools, customMetadata, sites, authentication). Of special note, there were also many site specific "location" tag blocks that I had to keep, but the new server had its own "location" tag block with server specific defaults that has to be kept.

Lastly, do note that if you use service accounts, these cached passwords are junk and will have to be re-entered for your app pools. None of my sites worked initially, but all that was required was re-entering the passwords for all my app pools and I was up and running.

If someone who can comment mention this post down thread - it will probably help someone else like me who has many sites on one server with complicated configurations.



Spring Boot and multiple external configuration files

Spring boot 1.X and Spring Boot 2.X don't provide the same options and behavior about the Externalized Configuration.

The very good answer of M. Deinum refers to Spring Boot 1 specifities.
I will update for Spring Boot 2 here.

Environment properties sources and order

Spring Boot 2 uses a very particular PropertySource order that is designed to allow sensible overriding of values. Properties are considered in the following order:

  • Devtools global settings properties on your home directory (~/ when devtools is active).

  • @TestPropertySource annotations on your tests.

  • @SpringBootTest#properties annotation attribute on your tests. Command line arguments.

  • Properties from SPRING_APPLICATION_JSON (inline JSON embedded in an environment variable or system property).

  • ServletConfig init parameters.

  • ServletContext init parameters.

  • JNDI attributes from java:comp/env.

  • Java System properties (System.getProperties()).

  • OS environment variables.

  • A RandomValuePropertySource that has properties only in random.*.

  • Profile-specific application properties outside of your packaged jar (application-{profile}.properties and YAML variants).

  • Profile-specific application properties packaged inside your jar (application-{profile}.properties and YAML variants).

  • Application properties outside of your packaged jar ( and YAML variants).

  • Application properties packaged inside your jar ( and YAML variants).

  • @PropertySource annotations on your @Configuration classes. Default properties (specified by setting SpringApplication.setDefaultProperties).

To specify external properties files these options should interest you :

  • Profile-specific application properties outside of your packaged jar (application-{profile}.properties and YAML variants).

  • Application properties outside of your packaged jar ( and YAML variants).

  • @PropertySource annotations on your @Configuration classes. Default properties (specified by setting SpringApplication.setDefaultProperties).

You can use only one of these 3 options or combine them according to your requirements.
For example for very simple cases using only profile-specific properties is enough but in other cases you may want to use both profile-specific properties, default properties and @PropertySource.

Default locations for files

About files (and variant), by default Spring loads them and add their properties in the environment from these in the following order :

  • A /config subdirectory of the current directory

  • The current directory

  • A classpath /config package

  • The classpath root

The higher priorities are so literally :

How to use properties files with specific names ?

The default locations are not always enough : the default locations like the default filename ( may not suit. Besides, as in the OP question you may need to specify multiple configuration files other than (and variant).
So will not be enough.

In this case you should provide an explicit location by using the spring.config.location environment property (which is a comma-separated list of directory locations or file paths).
To be free about the filenames pattern favor the list of file paths over the list of directories.
For example do like that :

java -jar myproject.jar --spring.config.location=classpath:/,classpath:/

That way is the most verbose that just specifying the folder but it is also the way to specify very finely our configuration files and to document clearly the properties effectively used.

spring.config.location now replaces default locations instead of adding to them

With Spring Boot 1, the spring.config.location argument adds specified locations in the Spring environment.
But from Spring Boot 2, spring.config.location replaces the default locations used by Spring by the specified locations in the Spring environment as stated in the documentation.

When custom config locations are configured by using spring.config.location, they replace the default locations. For example, if spring.config.location is configured with the value classpath:/custom-config/,file:./custom-config/, the search order becomes the following:

  1. file:./custom-config/

  2. classpath:custom-config/

spring.config.location is now a way to make sure that any file has to be explicitly specified.
For uber JARs that are not supposed to package files, that is rather nice.

To keep the old behavior of spring.config.location while using Spring Boot 2 you can use the new spring.config.additional-location property instead of spring.config.location that still adds the locations as stated by the documentation :

Alternatively, when custom config locations are configured by using spring.config.additional-location, they are used in addition to the default locations.

In practice

So supposing that as in the OP question, you have 2 external properties file to specify and 1 properties file included in the uber jar.

To use only configuration files you specified :


To add configuration files to these in the default locations :


classpath:/ is in the last example not required as the default locations have that and that default locations are here not overwritten but extended.

Difference between VARCHAR and TEXT in MySQL

There is an important detail that has been omitted in the answer above.

MySQL imposes a limit of 65,535 bytes for the max size of each row. The size of a VARCHAR column is counted towards the maximum row size, while TEXT columns are assumed to be storing their data by reference so they only need 9-12 bytes. That means even if the "theoretical" max size of your VARCHAR field is 65,535 characters you won't be able to achieve that if you have more than one column in your table.

Also note that the actual number of bytes required by a VARCHAR field is dependent on the encoding of the column (and the content). MySQL counts the maximum possible bytes used toward the max row size, so if you use a multibyte encoding like utf8mb4 (which you almost certainly should) it will use up even more of your maximum row size.

Correction: Regardless of how MySQL computes the max row size, whether or not the VARCHAR/TEXT field data is ACTUALLY stored in the row or stored by reference depends on your underlying storage engine. For InnoDB the row format affects this behavior. (Thanks Bill-Karwin)

Reasons to use TEXT:

  • If you want to store a paragraph or more of text
  • If you don't need to index the column
  • If you have reached the row size limit for your table

Reasons to use VARCHAR:

  • If you want to store a few words or a sentence
  • If you want to index the (entire) column
  • If you want to use the column with foreign-key constraints

Ruby 'require' error: cannot load such file

Ruby 1.9 has removed the current directory from the load path, and so you will need to do a relative require on this file, as David Grayson says:

require_relative 'tokenizer'

There's no need to suffix it with .rb, as Ruby's smart enough to know that's what you mean anyway.

Why is printing "B" dramatically slower than printing "#"?

Yes the culprit is definitely word-wrapping. When I tested your two programs, NetBeans IDE 8.2 gave me the following result.

  1. First Matrix: O and # = 6.03 seconds
  2. Second Matrix: O and B = 50.97 seconds

Looking at your code closely you have used a line break at the end of first loop. But you didn't use any line break in second loop. So you are going to print a word with 1000 characters in the second loop. That causes a word-wrapping problem. If we use a non-word character " " after B, it takes only 5.35 seconds to compile the program. And If we use a line break in the second loop after passing 100 values or 50 values, it takes only 8.56 seconds and 7.05 seconds respectively.

Random r = new Random();
for (int i = 0; i < 1000; i++) {
    for (int j = 0; j < 1000; j++) {
        if(r.nextInt(4) == 0) {
        } else {
        if(j%100==0){               //Adding a line break in second loop      

Another advice is that to change settings of NetBeans IDE. First of all, go to NetBeans Tools and click Options. After that click Editor and go to Formatting tab. Then select Anywhere in Line Wrap Option. It will take almost 6.24% less time to compile the program.

NetBeans Editor Settings

How to sort the letters in a string alphabetically in Python

You can use reduce

>>> a = 'ZENOVW'
>>> reduce(lambda x,y: x+y, sorted(a))

How do I login and authenticate to Postgresql after a fresh install?

The main difference between logging in with a postgres user or any other user created by us, is that when using the postgres user it is NOT necessary to specify the host with -h and instead for another user if.

Login with postgres user

$ psql -U postgres 

Creation and login with another user

# CREATE ROLE usertest LOGIN PASSWORD 'pwtest';
# CREATE DATABASE dbtest WITH OWNER = usertest;
# SHOW port;
# \q

$ psql -h localhost -d dbtest -U usertest -p 5432



Creating a simple configuration file and parser in C++

libconfig is very easy, and what's better, it uses a pseudo json notation for better readability.

Easy to install on Ubuntu: sudo apt-get install libconfig++8-dev

and link: -lconfig++

Error: Main method not found in class Calculate, please define the main method as: public static void main(String[] args)

My suggestions :

  • Keep the program modular. Keep the Calculate class in a separate file and create a new class that calls the main method. This would make the code readable.
  • For setting the values in the number, use constructors. Do not use like the methods you have used above like :

    public void setNumber(double fnum, double snum){ this.fn = fnum; = snum; }

    Constructors exists to initialize the objects.This is their job and they are pretty good at it.

  • Getters for members of Calculate class seem in place. But setters are not. Getters and setters serves as one important block in the bridge of efficient programming with java. Put setters for fnum and snum as well

  • In the main class, create a Calculate object using the new operator and the constructor in place.

  • Call the getAnswer() method with the created Calculate object.

Rest of the code looks fine to me. Be modular. You could read your program in a much better way.

Here is my modular piece of code. Two files : &

public class Calculate {

private double fn;
private double sn;
private char op;

    public double getFn() {
        return fn;

    public void setFn(double fn) {
        this.fn = fn;

    public double getSn() {
        return sn;

    public void setSn(double sn) { = sn;

    public char getOp() {
        return op;

    public void setOp(char op) {
        this.op = op;

    public Calculate(double fn, double sn, char op) {
        this.fn = fn; = sn;
        this.op = op;

public void getAnswer(){
    double ans;
    switch (getOp()){
        case '+': 
            ans = add(getFn(), getSn());
        case '-': 
            ans = sub (getFn(), getSn());
        case '*': 
            ans = mul (getFn(), getSn());
        case '/': 
            ans = div (getFn(), getSn());
            System.out.println("Invalid choice of operator");
    public static double add(double x,double y){
        return x + y;
    public static double sub(double x, double y){
        return x - y;
    public static double mul(double x, double y){
        return x * y;
    public static double div(double x, double y){
        return x / y;

    public static void ansOutput(double x){
        System.out.println("----------- -------");
        System.out.printf("the answer is %.2f\n", x);

public class Main {
    public static void main(String args[])
        Calculate obj = new Calculate(1,2,'+');

Android 8: Cleartext HTTP traffic not permitted

If possible change your url's from HTTP to HTTPS;

It works out!!!

ValueError: math domain error

You are trying to do a logarithm of something that is not positive.

Logarithms figure out the base after being given a number and the power it was raised to. log(0) means that something raised to the power of 2 is 0. An exponent can never result in 0*, which means that log(0) has no answer, thus throwing the math domain error

*Note: 0^0 can result in 0, but can also result in 1 at the same time. This problem is heavily argued over.

Reading images in python

import matplotlib.pyplot as plt
image = plt.imread('images/my_image4.jpg')

Using 'matplotlib.pyplot.imread' is recommended by warning messages in jupyter.

Pass parameter from a batch file to a PowerShell script

When a script is loaded, any parameters that are passed are automatically loaded into a special variables $args. You can reference that in your script without first declaring it.

As an example, create a file called test.ps1 and simply have the variable $args on a line by itself. Invoking the script like this, generates the following output:

PowerShell.exe -File test.ps1 a b c "Easy as one, two, three"
Easy as one, two, three

As a general recommendation, when invoking a script by calling PowerShell directly I would suggest using the -File option rather than implicitly invoking it with the & - it can make the command line a bit cleaner, particularly if you need to deal with nested quotes.

How to automatically close cmd window after batch file execution?

I had this, I added EXIT and initially it didn't work, I guess per requiring the called program exiting advice mentioned in another response here, however it now works without further ado - not sure what's caused this, but the point to note is that I'm calling a data file .html rather than the program that handles it browser.exe, I did not edit anything else but suffice it to say it's much neater just using a bat file to access the main access pages of those web documents and only having title.bat, contents.bat, index.bat in the root folder with the rest of the content in a subfolder.

i.e.: contents.bat reads

cd subfolder

It also looks better if I change the bat file icons for just those items to suit the context they are in too, but that's another matter, hiding the bat files in the subfolder and creating custom icon shortcuts to them in the root folder with the images called for the customisation also hidden.

How to iterate over arguments in a Bash script

Rewrite of a now-deleted answer by VonC.

Robert Gamble's succinct answer deals directly with the question. This one amplifies on some issues with filenames containing spaces.

See also: ${1:+"$@"} in /bin/sh

Basic thesis: "$@" is correct, and $* (unquoted) is almost always wrong. This is because "$@" works fine when arguments contain spaces, and works the same as $* when they don't. In some circumstances, "$*" is OK too, but "$@" usually (but not always) works in the same places. Unquoted, $@ and $* are equivalent (and almost always wrong).

So, what is the difference between $*, $@, "$*", and "$@"? They are all related to 'all the arguments to the shell', but they do different things. When unquoted, $* and $@ do the same thing. They treat each 'word' (sequence of non-whitespace) as a separate argument. The quoted forms are quite different, though: "$*" treats the argument list as a single space-separated string, whereas "$@" treats the arguments almost exactly as they were when specified on the command line. "$@" expands to nothing at all when there are no positional arguments; "$*" expands to an empty string — and yes, there's a difference, though it can be hard to perceive it. See more information below, after the introduction of the (non-standard) command al.

Secondary thesis: if you need to process arguments with spaces and then pass them on to other commands, then you sometimes need non-standard tools to assist. (Or you should use arrays, carefully: "${array[@]}" behaves analogously to "$@".)


    $ mkdir "my dir" anotherdir
    $ ls
    anotherdir      my dir
    $ cp /dev/null "my dir/my file"
    $ cp /dev/null "anotherdir/myfile"
    $ ls -Fltr
    total 0
    drwxr-xr-x   3 jleffler  staff  102 Nov  1 14:55 my dir/
    drwxr-xr-x   3 jleffler  staff  102 Nov  1 14:55 anotherdir/
    $ ls -Fltr *
    my dir:
    total 0
    -rw-r--r--   1 jleffler  staff  0 Nov  1 14:55 my file

    total 0
    -rw-r--r--   1 jleffler  staff  0 Nov  1 14:55 myfile
    $ ls -Fltr "./my dir" "./anotherdir"
    ./my dir:
    total 0
    -rw-r--r--   1 jleffler  staff  0 Nov  1 14:55 my file

    total 0
    -rw-r--r--   1 jleffler  staff  0 Nov  1 14:55 myfile
    $ var='"./my dir" "./anotherdir"' && echo $var
    "./my dir" "./anotherdir"
    $ ls -Fltr $var
    ls: "./anotherdir": No such file or directory
    ls: "./my: No such file or directory
    ls: dir": No such file or directory

Why doesn't that work? It doesn't work because the shell processes quotes before it expands variables. So, to get the shell to pay attention to the quotes embedded in $var, you have to use eval:

    $ eval ls -Fltr $var
    ./my dir:
    total 0
    -rw-r--r--   1 jleffler  staff  0 Nov  1 14:55 my file

    total 0
    -rw-r--r--   1 jleffler  staff  0 Nov  1 14:55 myfile

This gets really tricky when you have file names such as "He said, "Don't do this!"" (with quotes and double quotes and spaces).

    $ cp /dev/null "He said, \"Don't do this!\""
    $ ls
    He said, "Don't do this!"       anotherdir                      my dir
    $ ls -l
    total 0
    -rw-r--r--   1 jleffler  staff    0 Nov  1 15:54 He said, "Don't do this!"
    drwxr-xr-x   3 jleffler  staff  102 Nov  1 14:55 anotherdir
    drwxr-xr-x   3 jleffler  staff  102 Nov  1 14:55 my dir

The shells (all of them) do not make it particularly easy to handle such stuff, so (funnily enough) many Unix programs do not do a good job of handling them. On Unix, a filename (single component) can contain any characters except slash and NUL '\0'. However, the shells strongly encourage no spaces or newlines or tabs anywhere in a path names. It is also why standard Unix file names do not contain spaces, etc.

When dealing with file names that may contain spaces and other troublesome characters, you have to be extremely careful, and I found long ago that I needed a program that is not standard on Unix. I call it escape (version 1.1 was dated 1989-08-23T16:01:45Z).

Here is an example of escape in use - with the SCCS control system. It is a cover script that does both a delta (think check-in) and a get (think check-out). Various arguments, especially -y (the reason why you made the change) would contain blanks and newlines. Note that the script dates from 1992, so it uses back-ticks instead of $(cmd ...) notation and does not use #!/bin/sh on the first line.

:   "@(#)$Id:,v 1.8 1992/12/29 10:46:21 jl Exp $"
#   Delta and get files
#   Uses escape to allow for all weird combinations of quotes in arguments

case `basename $0 .sh` in
deledit)    eflag="-e";;

for arg in "$@"
    case "$arg" in
    -r*)    gargs="$gargs `escape \"$arg\"`"
            dargs="$dargs `escape \"$arg\"`"
    -e)     gargs="$gargs `escape \"$arg\"`"
    -*)     dargs="$dargs `escape \"$arg\"`"
    *)      gargs="$gargs `escape \"$arg\"`"
            dargs="$dargs `escape \"$arg\"`"

eval delta "$dargs" && eval get $eflag $sflag "$gargs"

(I would probably not use escape quite so thoroughly these days - it is not needed with the -e argument, for example - but overall, this is one of my simpler scripts using escape.)

The escape program simply outputs its arguments, rather like echo does, but it ensures that the arguments are protected for use with eval (one level of eval; I do have a program which did remote shell execution, and that needed to escape the output of escape).

    $ escape $var
    '"./my' 'dir"' '"./anotherdir"'
    $ escape "$var"
    '"./my dir" "./anotherdir"'
    $ escape x y z
    x y z

I have another program called al that lists its arguments one per line (and it is even more ancient: version 1.1 dated 1987-01-27T14:35:49). It is most useful when debugging scripts, as it can be plugged into a command line to see what arguments are actually passed to the command.

    $ echo "$var"
    "./my dir" "./anotherdir"
    $ al $var
    $ al "$var"
    "./my dir" "./anotherdir"

[Added: And now to show the difference between the various "$@" notations, here is one more example:

$ cat
set -x
al $@
al $*
al "$*"
al "$@"
$ sh     *      */*
+ al He said, '"Don'\''t' do 'this!"' anotherdir my dir anotherdir/myfile my dir/my file
+ al He said, '"Don'\''t' do 'this!"' anotherdir my dir anotherdir/myfile my dir/my file
+ al 'He said, "Don'\''t do this!" anotherdir my dir anotherdir/myfile my dir/my file'
He said, "Don't do this!" anotherdir my dir anotherdir/myfile my dir/my file
+ al 'He said, "Don'\''t do this!"' anotherdir 'my dir' anotherdir/myfile 'my dir/my file'
He said, "Don't do this!"
my dir
my dir/my file

Notice that nothing preserves the original blanks between the * and */* on the command line. Also, note that you can change the 'command line arguments' in the shell by using:

set -- -new -opt and "arg with space"

This sets 4 options, '-new', '-opt', 'and', and 'arg with space'.

Hmm, that's quite a long answer - perhaps exegesis is the better term. Source code for escape available on request (email to firstname dot lastname at gmail dot com). The source code for al is incredibly simple:

#include <stdio.h>
int main(int argc, char **argv)
    while (*++argv != 0)

That's all. It is equivalent to the script that Robert Gamble showed, and could be written as a shell function (but shell functions didn't exist in the local version of Bourne shell when I first wrote al).

Also note that you can write al as a simple shell script:

[ $# != 0 ] && printf "%s\n" "$@"

The conditional is needed so that it produces no output when passed no arguments. The printf command will produce a blank line with only the format string argument, but the C program produces nothing.

Preserve Line Breaks From TextArea When Writing To MySQL

i am using this two method steps for preserve same text which is in textarea to store in mysql and at a getting time i can also simply displaying plain text.....

step 1:

$textToStore = nl2br(htmlentities($status, ENT_QUOTES, 'UTF-8'));

In query enter $textToStore....

step 2:

write code for select query...and direct echo values....

It works

Why is "forEach not a function" for this object?

When I tried to access the result from

Object.keys(a).forEach(function (key){ console.log(a[key]); });

it was plain text result with no key-value pairs Here is an example

var fruits = {
    apple: "fruits/apple.png",
    banana: "fruits/banana.png",
    watermelon: "watermelon.jpg",
    grapes: "grapes.png",
    orange: "orange.jpg"

Now i want to get all links in a separated array , but with this code

    function linksOfPics(obJect){

the result of :



I figured out this one which solves what I'm looking for

["fruits/apple.png", "fruits/banana.png", "watermelon.jpg", "grapes.png", "orange.jpg"]

Any tools to generate an XSD schema from an XML instance document?

You can use an open source and cross-platform option: inst2xsd from Apache's XMLBeans. I find it very useful and easy.

Just download, unzip and play (it requires Java).

How to reject in async/await syntax?

It should probably also be mentioned that you can simply chain a catch() function after the call of your async operation because under the hood still a promise is returned.

await foo().catch(error => console.log(error));

This way you can avoid the try/catch syntax if you do not like it.

Java - How do I make a String array with values?

Another way to create an array with String apart from

String[] strings =  { "abc", "def", "hij", "xyz" };

is to use split. I find this more readable if there are lots of Strings.

String[] strings =  "abc,def,hij,xyz".split(",");

or the following is good if you are parsing lines of strings from another source.

String[] strings =  ("abc\n" +
                     "def\n" +
                     "hij\n" +

How do I put my website's logo to be the icon image in browser tabs?

<link rel="apple-touch-icon" sizes="114x114" href="${resource(dir: 'images', file: 

or you can use this one

<link rel="shortcut icon" sizes="114x114" href="${resource(dir: 'images', file: 'favicon.ico')}"

SQL how to check that two tables has exactly the same data?

I wrote this to compare the results of a pretty nasty view I ported from Oracle to SQL Server. It creates a pair of temp tables, #DataVariances and #SchemaVariances, with differences in (you guessed it) the data in the tables and the schema of the tables themselves.

It requires both tables have a primary key, but you could drop it into tempdb with an identity column if the source tables don't have one.

declare @TableA_ThreePartName nvarchar(max) = ''
declare @TableB_ThreePartName nvarchar(max) = ''
declare @KeyName nvarchar(max) = ''


    Script to compare two tables and return differneces in schema and data.

    Author: Devin Lamothe       2017-08-11

set nocount on

-- Split three part name into database/schema/table
declare @Database_A nvarchar(max) = (
    select  left(@TableA_ThreePartName,charindex('.',@TableA_ThreePartName) - 1))
declare @Table_A nvarchar(max) = (
    select  right(@TableA_ThreePartName,len(@TableA_ThreePartName) - charindex('.',@TableA_ThreePartName,len(@Database_A) + 2)))
declare @Schema_A nvarchar(max) = (
    select  replace(replace(@TableA_ThreePartName,@Database_A + '.',''),'.' + @Table_A,''))

declare @Database_B nvarchar(max) = (
    select  left(@TableB_ThreePartName,charindex('.',@TableB_ThreePartName) - 1))
declare @Table_B nvarchar(max) = (
    select  right(@TableB_ThreePartName,len(@TableB_ThreePartName) - charindex('.',@TableB_ThreePartName,len(@Database_B) + 2)))
declare @Schema_B nvarchar(max) = (
    select  replace(replace(@TableB_ThreePartName,@Database_B + '.',''),'.' + @Table_B,''))

-- Get schema for both tables
declare @GetTableADetails nvarchar(max) = '
    use [' + @Database_A +']
        select  COLUMN_NAME
             ,  DATA_TYPE
         where  TABLE_NAME = ''' + @Table_A + '''
           and  TABLE_SCHEMA = ''' + @Schema_A + '''
create table #Table_A_Details (
    ColumnName nvarchar(max)
,   DataType nvarchar(max)
insert into #Table_A_Details
exec (@GetTableADetails)

declare @GetTableBDetails nvarchar(max) = '
    use [' + @Database_B +']
        select  COLUMN_NAME
             ,  DATA_TYPE
         where  TABLE_NAME = ''' + @Table_B + '''
           and  TABLE_SCHEMA = ''' + @Schema_B + '''
create table #Table_B_Details (
    ColumnName nvarchar(max)
,   DataType nvarchar(max)
insert into #Table_B_Details
exec (@GetTableBDetails)

-- Get differences in table schema
            select  ROW_NUMBER() over (order by
                    ,   b.ColumnName) as RowKey
                 ,  a.ColumnName as A_ColumnName
                 ,  a.DataType as A_DataType
                 ,  b.ColumnName as B_ColumnName
                 ,  b.DataType as B_DataType
              into  #FieldList
              from  #Table_A_Details a
   full outer join  #Table_B_Details b
                on  a.ColumnName = b.ColumnName
             where  a.ColumnName is null
                or  b.ColumnName is null
                or  a.DataType <> b.DataType

        drop table  #Table_A_Details
        drop table  #Table_B_Details

            select  coalesce(A_ColumnName,B_ColumnName) as ColumnName
                 ,  A_DataType
                 ,  B_DataType
              into  #SchemaVariances
              from  #FieldList

-- Get differences in table data
declare @LastColumn int = (select max(RowKey) from #FieldList)
declare @RowNumber int = 1
declare @ThisField nvarchar(max)
declare @TestSql nvarchar(max)

create table #DataVariances (
    TableKey            nvarchar(max)
,   FieldName           nvarchar(max)
,   TableA_Value        nvarchar(max)
,   TableB_Value        nvarchar(max)

delete from #FieldList where A_DataType in ('varbinary','image') or B_DataType in ('varbinary','image') 

while @RowNumber <= @LastColumn begin
    set @TestSql = '
        select  coalesce(a.[' + @KeyName + '],b.[' + @KeyName + ']) as TableKey
             ,  ''' + @ThisField + ''' as FieldName
             ,  a.[' + @ThisField + '] as [TableA_Value]
             ,  b.[' + @ThisField + '] as [TableB_Value]
          from  [' + @Database_A + '].[' + @Schema_A + '].[' + @Table_A + '] a 
    inner join  [' + @Database_B + '].[' + @Schema_B + '].[' + @Table_B + '] b
            on  a.[' + @KeyName + '] = b.[' + @KeyName + ']
         where  ltrim(rtrim(a.[' + @ThisField + '])) <> ltrim(rtrim(b.[' + @ThisField + ']))
            or (a.[' + @ThisField + '] is null and  b.[' + @ThisField + '] is not null)
            or (a.[' + @ThisField + '] is not null and  b.[' + @ThisField + '] is null)

insert into #DataVariances
exec (@TestSql)

set @RowNumber = @RowNumber + 1
set @ThisField = (select coalesce(A_ColumnName,B_ColumnName) from #FieldList a where RowKey = @RowNumber)


drop table #FieldList

print 'Query complete.  Select from #DataVariances to verify data integrity or #SchemaVariances to verify schemas match.  Data types varbinary and image are not checked.'

How to remove all MySQL tables from the command-line without DROP database permissions?

Try this.

This works even for tables with constraints (foreign key relationships). Alternatively you can just drop the database and recreate, but you may not have the necessary permissions to do that.

mysqldump -u[USERNAME] -p[PASSWORD] \
  --add-drop-table --no-data [DATABASE] | \
  grep -e '^DROP \| FOREIGN_KEY_CHECKS' | \

In order to overcome foreign key check effects, add show table at the end of the generated script and run many times until the show table command results in an empty set.

Decoding JSON String in Java

This is the JSON String we want to decode :

   "stats": { 
       "sdr": "aa:bb:cc:dd:ee:ff", 
       "rcv": "aa:bb:cc:dd:ee:ff", 
       "time": "UTC in millis", 
       "type": 1, 
       "subt": 1, 
       "argv": [
          {"1": 2}, 
          {"2": 3}

I store this string under the variable name "sJSON" Now, this is how to decode it :)

// Creating a JSONObject from a String 
JSONObject nodeRoot  = new JSONObject(sJSON); 

// Creating a sub-JSONObject from another JSONObject
JSONObject nodeStats = nodeRoot.getJSONObject("stats");

// Getting the value of a attribute in a JSONObject
String sSDR = nodeStats.getString("sdr");

List all kafka topics

Kafka is a distributed system and needs Zookeeper. you have to start zookeeper too. Follow "Quick Start" here :

Create Excel files from C# without office

Try EPPlus if you use Excel 2007. Supports ranges, cellstyling, charts, shapes, pictures and a lot of other stuff

Generating a random & unique 8 character string using MySQL

This problem consists of two very different sub-problems:

  • the string must be seemingly random
  • the string must be unique

While randomness is quite easily achieved, the uniqueness without a retry loop is not. This brings us to concentrate on the uniqueness first. Non-random uniqueness can trivially be achieved with AUTO_INCREMENT. So using a uniqueness-preserving, pseudo-random transformation would be fine:

  • Hash has been suggested by @paul
  • AES-encrypt fits also
  • But there is a nice one: RAND(N) itself!

A sequence of random numbers created by the same seed is guaranteed to be

  • reproducible
  • different for the first 8 iterations
  • if the seed is an INT32

So we use @AndreyVolk's or @GordonLinoff's approach, but with a seeded RAND:

e.g. Assumin id is an AUTO_INCREMENT column:

INSERT INTO vehicles VALUES (blah); -- leaving out the number plate
UPDATE vehicles SET numberplate=concat(
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed:=round(rand(@lid)*4294967296))*36+1, 1),
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed:=round(rand(@seed)*4294967296))*36+1, 1),
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed:=round(rand(@seed)*4294967296))*36+1, 1),
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed:=round(rand(@seed)*4294967296))*36+1, 1),
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed:=round(rand(@seed)*4294967296))*36+1, 1),
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed:=round(rand(@seed)*4294967296))*36+1, 1),
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed:=round(rand(@seed)*4294967296))*36+1, 1),
  substring('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', rand(@seed)*36+1, 1)
WHERE id=@lid;

Getting the parent of a directory in Bash

This would go up to the parent folder

cd ../

Why declare unicode by string in python?

That doesn't set the format of the string; it sets the format of the file. Even with that header, "hello" is a byte string, not a Unicode string. To make it Unicode, you're going to have to use u"hello" everywhere. The header is just a hint of what format to use when reading the .py file.

java.lang.ClassNotFoundException on working app

The Class Not Found Error shows that your class files are missing. Please go to Properties > Java Build Path and add your package containing your java files to the Source tab if found missing. Then build your project. This will create the missing .class files.

How to create EditText accepts Alphabets only in android?

Add this line with your EditText tag.


Your EditText tag should look like:

        android:layout_height="wrap_content" />

Java way to check if a string is palindrome

I'm new to java and I'm taking up your question as a challenge to improve my knowledge as well so please forgive me if this does not answer your question well:

import java.util.ArrayList;
import java.util.List;

public class PalindromeRecursiveBoolean {

    public static boolean isPalindrome(String str) {

        str = str.toUpperCase();
        char[] strChars = str.toCharArray();

        List<Character> word = new ArrayList<>();
        for (char c : strChars) {

        while (true) {
            if ((word.size() == 1) || (word.size() == 0)) {
                return true;
            if (word.get(0) == word.get(word.size() - 1)) {
                word.remove(word.size() - 1);
            } else {
                return false;


  1. If the string is made of no letters or just one letter, it is a palindrome.
  2. Otherwise, compare the first and last letters of the string.
    • If the first and last letters differ, then the string is not a palindrome
    • Otherwise, the first and last letters are the same. Strip them from the string, and determine whether the string that remains is a palindrome. Take the answer for this smaller string and use it as the answer for the original string then repeat from 1.

The only string manipulation is changing the string to uppercase so that you can enter something like 'XScsX'

WMI "installed" query different from add/remove programs list?

You can get it in one line with powershell and batch file :

@echo off
Powershell /command "Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\* | Select-Object DisplayName, DisplayVersion, Publisher, InstallDate | Format-List"

Unable to find a @SpringBootConfiguration when doing a JpaTest

In my case the packages were different between the Application and Test classes

public class ProducerApplication {


package com.example.abc_etc;
public class ProducerApplicationTest {

After making them agree the tests ran correctly.

Delete forked repo from GitHub

Just delete the forked repo from your GitHub account.

  • If I go to admin panel on GitHub there's a delete option. If I delete it as the option above, will it make any effect in the original one or not?

It wont make any changes in the original one; cos, its your repo now.

Android runOnUiThread explanation

If you already have the data "for (Parcelable currentHeadline : allHeadlines)," then why are you doing that in a separate thread?

You should poll the data in a separate thread, and when it's finished gathering it, then call your populateTables method on the UI thread:

private void populateTable() {
    runOnUiThread(new Runnable(){
        public void run() {
            //If there are stories, add them to the table
            for (Parcelable currentHeadline : allHeadlines) {
            try {
            } catch (final Exception ex) {
                Log.i("---","Exception in thread");

Simple way to read single record from MySQL

Warning! Your SQL isn't a good idea, because it will select all rows (no WHERE clause assumes "WHERE 1"!) and clog your application if you have a large number of rows. (What's the point of selecting 1,000 rows when 1 will do?) So instead, when selecting only one row, make sure you specify the LIMIT clause:

$sql = "SELECT id FROM games LIMIT 1";  // Select ONLY one, instead of all
$result = $db->query($sql);
$row = $result->fetch_assoc();
echo 'Game ID: '.$row['id'];

This difference requires MySQL to select only the first matching record, so ordering the table is important or you ought to use a WHERE clause. However, it's a whole lot less memory and time to find that one record, than to get every record and output row number one.

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

const path = require('path');

if (path.sep === "\\") {
} else {
console.log("Not Windows");

Git on Bitbucket: Always asked for password, even after uploading my public SSH key

As explained here, if you clone with SSH url, you don't need to enter username / password each time you push / pull. Check above answer by @manojlds

But if you want to clone with HTTPS and want to avoid entering username / password each time, you can store credentials into cache with below command:

git config --global credential.helper 'cache --timeout 3600'

where 3600 (seconds) means 1 hour, you may change it as per your requirement.

Remove element by id

This is the best function to remove an element without script error:

function Remove(EId)

Note to EObj=document.getElementById(EId).

This is ONE equal sign not ==.

if element EId exists then the function removes it, otherwise it returns false, not error.

Timestamp conversion in Oracle for YYYY-MM-DD HH:MM:SS format

VALUES(TO_DATE('2012-03-28 11:10:00','yyyy/mm/dd hh24:mi:ss'));!4/22115/1

What's the difference between git reset --mixed, --soft, and --hard?

All the other answers are great, but I find it best to understand them by breaking down files into three categories: unstaged, staged, commit:

  • --hard should be easy to understand, it restores everything
  • --mixed (default) :
    1. unstaged files: don't change
    2. staged files: move to unstaged
    3. commit files: move to unstaged
  • --soft:
    1. unstaged files: don't change
    2. staged files: dont' change
    3. commit files: move to staged

In summary:

  • --soft option will move everything (except unstaged files) into staging area
  • --mixed option will move everything into unstaged area

regex match any whitespace

The reason I used a + instead of a '*' is because a plus is defined as one or more of the preceding element, where an asterisk is zero or more. In this case we want a delimiter that's a little more concrete, so "one or more" spaces.


will match:

wordA wordB     wordC
worda wordb wordc
wordA   wordb   wordC

The words, in this expression, will have to be specific, and also in order (a, b, then c)

Python module for converting PDF to text

I have used pdftohtml with the -xml argument, read the result with subprocess.Popen(), that will give you x coord, y coord, width, height, and font, of every snippet of text in the pdf. I think this is what 'evince' probably uses too because the same error messages spew out.

If you need to process columnar data, it gets slightly more complicated as you have to invent an algorithm that suits your pdf file. The problem is that the programs that make PDF files don't really necessarily lay out the text in any logical format. You can try simple sorting algorithms and it works sometimes, but there can be little 'stragglers' and 'strays', pieces of text that don't get put in the order you thought they would. So you have to get creative.

It took me about 5 hours to figure out one for the pdf's I was working on. But it works pretty good now. Good luck.

How to create a custom scrollbar on a div (Facebook style)

Facebook uses a very clever technique I described in context of my scrollbar plugin jsFancyScroll:

The scrolled content is actually scrolled natively by the browser scrolling mechanisms while the native scrollbar is hidden by using overflow definitions and the custom scrollbar is kept in sync by bi-directional event listening.

Feel free to use my plugin for your project: :)

I highly recommend it over plugins such as TinyScrollbar that come with terrible performance issues!

What is the Java equivalent for LINQ?

JaQu is the LINQ equivalent for Java. Although it was developed for the H2 database, it should work for any database since it uses JDBC.

Does Index of Array Exist

You can check the length of the array to see if item 25 is valid in the sense of being in the array, then you could use

if (array.Length > 25)
   if (array[25] != null)

to see if the array item itself has been set.

Why does a base64 encoded string have an = sign at the end

The equals sign (=) is used as padding in certain forms of base64 encoding. The Wikipedia article on base64 has all the details.

Make ABC Ordered List Items Have Bold Style

a bit of a cheat, but it works:


<ol type="A" style="font-weight: bold;">
  <li><span>More text</span></li>


li span { font-weight: normal; }

How to permanently export a variable in Linux?

A particular example: I have Java 7 and Java 6 installed, I need to run some builds with 6, others with 7. Therefore I need to dynamically alter JAVA_HOME so that maven picks up what I want for each build. I did the following:

  • created script which simply does export JAVA_HOME=... path to j6 install...
  • then, as suggested by one of the comments above, whenever I need J6 for a build, I run source in that respective command terminal. By default, my JAVA_HOME is set to J7.

Hope this helps.

Convert a String representation of a Dictionary to a dictionary?

To summarize:

import ast, yaml, json, timeit

descs=['short string','long string']

for  desc,string in zip(descs,strings):
    for  func in funcs:
        print(func.__module__+' '+func.__name__+':')
        %timeit func(string)        


*** short string ***

json loads:
4.47 µs ± 33.4 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
builtins eval:
24.1 µs ± 163 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
ast literal_eval:
30.4 µs ± 299 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
yaml load:
504 µs ± 1.29 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

*** long string ***

json loads:
29.6 µs ± 230 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
builtins eval:
219 µs ± 3.92 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
ast literal_eval:
331 µs ± 1.89 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
yaml load:
9.02 ms ± 92.2 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

Conclusion: prefer json.loads

How to perform runtime type checking in Dart?

Just to clarify a bit the difference between is and runtimeType. As someone said already (and this was tested with Dart V2+) the following code:

class Foo { 
  Type get runtimeType => String;
main() {
  var foo = new Foo();
  if (foo is Foo) {
    print("it's a foo!");
  print("type is ${foo.runtimeType}");


will output:

it's a foo! 
type is String

Which is wrong. Now, I can't see the reason why one should do such a thing...

Transfer data between databases with PostgreSQL

From: hxxp://dbaspot.c om/postgresql/348627-pg_dump-t-give-where-condition.html (NOTE: the link is now broken)

# create temp table with the data
psql mydb
CREATE TABLE temp1 (LIKE mytable);
INSERT INTO temp1 SELECT * FROM mytable WHERE myconditions;

# export the data to a sql file
pg_dump --data-only --column-inserts -t temp1 mtdb > out.sql
psql mydb

# import temp1 rows in another database
cat out.sql | psql -d [other_db]
psql other_db
INSERT INTO mytable (SELECT * FROM temp1);

Another method useful in remotes

  # export a table csv and import in another database
  psql-remote> COPY elements TO '/tmp/elements.csv' DELIMITER ',' CSV HEADER;
  $ scp /tmp/elements.csv
  psql-local> COPY elements FROM '/tmp/elements.csv' DELIMITER ',' CSV;

mongodb service is not starting up

Removing the .lock file and reinstalling did not solve the issue on my machine (Ubuntu 19.10). The problem was that after unexpected shutdown, the MongoDB sock does not belong to the MongoDB group and user anymore.

So, I follow the steps below:

  1. cd /tmp
  2. ls *.sock
  3. Change the user:group permission:

    chown mongodb:mongodb <YOUR_SOCK>
  4. sudo systemctl start mongod

  5. sudo systemctl status mongod

PostgreSQL Exception Handling

Just want to add my two cents on this old post:

In my opinion, almost all of relational database engines include a commit transaction execution automatically after execute a DDL command even when you have autocommit=false, So you don't need to start a transaction to avoid a potential truncated object creation because It is completely unnecessary.

XSLT equivalent for JSON

It may be possible to use XSLT with JSON. Verson 3 of XPath(3.1) XSLT(3.0) and XQuery(3.1) supports JSON in some way. This seems to be available in the commercial version of Saxon, and might at some point be included in the HE version.


What I would expect from an alternative solution:

I would want to be able input JSON to fetch a matching set of data, and output JSON or TEXT.

Access arbitrary properties and evaluate the values

Support for conditional logic

I would want the transformation scripts to be external from the tool, text based, and preferably a commonly used language.

Potential alternative?

I wonder if SQL could be a suitable alternative.

It would be nice if the alternative tool could handle JSON and XML

I have not yet tried to convert the XSLT scripts I use to SQL, or fully evaluated this option yet, but I hope to look into it more soon. Just some thoughts so far.

Read file line by line in PowerShell

The almighty switch works well here:

three' > file

$regex = '^t'

switch -regex -file file { 
  $regex { "line is $_" } 


line is two
line is three

Importing a CSV file into a sqlite3 database table using Python

import csv, sqlite3

con = sqlite3.connect(":memory:") # change to 'sqlite:///your_filename.db'
cur = con.cursor()
cur.execute("CREATE TABLE t (col1, col2);") # use your column names here

with open('data.csv','r') as fin: # `with` statement available in 2.5+
    # csv.DictReader uses first line in file for column headings by default
    dr = csv.DictReader(fin) # comma is default delimiter
    to_db = [(i['col1'], i['col2']) for i in dr]

cur.executemany("INSERT INTO t (col1, col2) VALUES (?, ?);", to_db)

how to change the default positioning of modal in bootstrap?

If you need to change the bottom position of the modal, you need to modify the max-height of the modal-body:

.modal-body {
  max-height: 75vh;

As other answers have said, you can adjust the right and top on the modal-dialog :

.modal-dialog {
  top: 10vh;
  right: 5vw;
  • "vh" means "% of view height"
  • "vw" means "% of view width"

Split code over multiple lines in an R script

You are not breaking code over multiple lines, but rather a single identifier. There is a difference.

For your issue, try

R> setwd(paste("~/a/very/long/path/here",
               "/and/then/some/more", sep=""))

which also illustrates that it is perfectly fine to break code across multiple lines.

How to configure static content cache per folder and extension in IIS7?

You can do it on a per file basis. Use the path attribute to include the filename

<?xml version="1.0" encoding="UTF-8"?>
    <location path="YourFileNameHere.xml">
                <clientCache cacheControlMode="DisableCache" />

How to unit test abstract classes: extend with stubs?

This is the pattern I usually follow when setting up a harness for testing an abstract class:

public abstract class MyBase{
  public abstract void VoidMethod(object param1);
  public abstract object MethodWithReturn(object param1);

And the version I use under test:

public class MyBaseHarness : MyBase{
  public Action<object> VoidMethodFunction;
  public override void VoidMethod(object param1){
  public Func<object, object> MethodWithReturnFunction;
  public override object MethodWithReturn(object param1){
    return MethodWihtReturnFunction(param1);

If the abstract methods are called when I don't expect it, the tests fail. When arranging the tests, I can easily stub out the abstract methods with lambdas that perform asserts, throw exceptions, return different values, etc.

Dump all documents of Elasticsearch

For your case Elasticdump is the perfect answer.
First, you need to download the mapping and then the index

# Install the elasticdump 
npm install elasticdump -g

# Dump the mapping 
elasticdump --input=http://<your_es_server_ip>:9200/index --output=es_mapping.json --type=mapping

# Dump the data
elasticdump --input=http://<your_es_server_ip>:9200/index --output=es_index.json --type=data    

If you want to dump the data on any server I advise you to install esdump through docker. You can get more info from this website Blog Link

What version of javac built my jar?

You check in Manifest file of jar example:

Manifest-Version: 1.0 Created-By: 1.6.0 (IBM Corporation)

List of macOS text editors and code editors

TextMate not for "advanced programmers". That does not make sense, TextMate contains everything an "advanced programmer" would want. It allows them to define a bundle that allows them to quickly set up the way they want their source code formatted, or one that follows the project guidelines, quick easy access to create entire structures and classes based on typing part of a construct and hitting tab.

TextMate is my tool of choice, it is fast, lightweight and yet contains all of the features I would want in a tool to program with. While it is not tightly integrated in Xcode, that is not a problem for me as I don't write software for Mac OS X. I write software for FreeBSD.

Pass a javascript variable value into input type hidden value

if you already have that hidden input :

function product(a, b) {
   return a * b;
function setInputValue(input_id, val) {
    document.getElementById(input_id).setAttribute('value', val);

if not, you can create one, add it to the body and then set it's value :

function addInput(val) {
    var input = document.createElement('input');
    input.setAttribute('type', 'hidden');
    input.setAttribute('value', val);

And then you can use(depending on the case) :

addInput(product(2, 3)); // if you want to create the input
// or
setInputValue('input_id', product(2, 3)); 

Correct set of dependencies for using Jackson mapper

No, you can simply use com.fasterxml.jackson.databind.ObjectMapper. Most likely you forgot to fix your import-statements, delete all references to codehaus and you're golden.

Align contents inside a div

text-align aligns text and other inline content. It doesn't align block element children.

To do that, you want to give the element you want aligned a width, with ‘auto’ left and right margins. This is the standards-compliant way that works everywhere except IE5.x.

<div style="width: 50%; margin: 0 auto;">Hello</div>

For this to work in IE6, you need to make sure Standards Mode is on by using a suitable DOCTYPE.

If you really need to support IE5/Quirks Mode, which these days you shouldn't really, it is possible to combine the two different approaches to centering:

<div style="text-align: center">
    <div style="width: 50%; margin: 0 auto; text-align: left">Hello</div>

(Obviously, styles are best put inside a stylesheet, but the inline version is illustrative.)

How to randomly select rows in SQL?

In order to shuffle the SQL result set, you need to use a database-specific function call.

Note that sorting a large result set using a RANDOM function might turn out to be very slow, so make sure you do that on small result sets.

If you have to shuffle a large result set and limit it afterward, then it's better to use something like the Oracle SAMPLE(N) or the TABLESAMPLE in SQL Server or PostgreSQL instead of a random function in the ORDER BY clause.

So, assuming we have the following database table:

Song database table

And the following rows in the song table:

| id | artist                          | title                              |
| 1  | Miyagi & ???????? ft. ??? ????? | I Got Love                         |
| 2  | HAIM                            | Don't Save Me (Cyril Hahn Remix)   |
| 3  | 2Pac ft. DMX                    | Rise Of A Champion (GalilHD Remix) |
| 4  | Ed Sheeran & Passenger          | No Diggity (Kygo Remix)            |
| 5  | JP Cooper ft. Mali-Koa          | All This Love                      |


On Oracle, you need to use the DBMS_RANDOM.VALUE function, as illustrated by the following example:

    artist||' - '||title AS song
FROM song

When running the aforementioned SQL query on Oracle, we are going to get the following result set:

| song                                              |
| JP Cooper ft. Mali-Koa - All This Love            |
| 2Pac ft. DMX - Rise Of A Champion (GalilHD Remix) |
| HAIM - Don't Save Me (Cyril Hahn Remix)           |
| Ed Sheeran & Passenger - No Diggity (Kygo Remix)  |
| Miyagi & ???????? ft. ??? ????? - I Got Love      |

Notice that the songs are being listed in random order, thanks to the DBMS_RANDOM.VALUE function call used by the ORDER BY clause.

SQL Server

On SQL Server, you need to use the NEWID function, as illustrated by the following example:

    CONCAT(CONCAT(artist, ' - '), title) AS song
FROM song

When running the aforementioned SQL query on SQL Server, we are going to get the following result set:

| song                                              |
| Miyagi & ???????? ft. ??? ????? - I Got Love      |
| JP Cooper ft. Mali-Koa - All This Love            |
| HAIM - Don't Save Me (Cyril Hahn Remix)           |
| Ed Sheeran & Passenger - No Diggity (Kygo Remix)  |
| 2Pac ft. DMX - Rise Of A Champion (GalilHD Remix) |

Notice that the songs are being listed in random order, thanks to the NEWID function call used by the ORDER BY clause.


On PostgreSQL, you need to use the random function, as illustrated by the following example:

    artist||' - '||title AS song
FROM song
ORDER BY random()

When running the aforementioned SQL query on PostgreSQL, we are going to get the following result set:

| song                                              |
| 2Pac ft. DMX - Rise Of A Champion (GalilHD Remix) |
| JP Cooper ft. Mali-Koa - All This Love            |
| Ed Sheeran & Passenger - No Diggity (Kygo Remix)  |
| HAIM - Don't Save Me (Cyril Hahn Remix)           |
| Miyagi & ???????? ft. ??? ????? - I Got Love      |

Notice that the songs are being listed in random order, thanks to the random function call used by the ORDER BY clause.


On MySQL, you need to use the RAND function, as illustrated by the following example:

  CONCAT(CONCAT(artist, ' - '), title) AS song
FROM song

When running the aforementioned SQL query on MySQL, we are going to get the following result set:

| song                                              |
| HAIM - Don't Save Me (Cyril Hahn Remix)           |
| Ed Sheeran & Passenger - No Diggity (Kygo Remix)  |
| Miyagi & ???????? ft. ??? ????? - I Got Love      |
| 2Pac ft. DMX - Rise Of A Champion (GalilHD Remix) |
| JP Cooper ft. Mali-Koa - All This Love            |

Notice that the songs are being listed in random order, thanks to the RAND function call used by the ORDER BY clause.

1067 error on attempt to start MySQL

Also check if all dirs which you wrote in the my.ini exists.

My problem was that tmpdir doeesn`t exist so MySQL daemon falls with error 1067.

port= 3306
tmpdir = "C:/tmp"

In this case C:/tmp must exists.

Installing Pandas on Mac OSX

Not an innovative way but below two steps might save a ton of time and energy.

  1. Updating (Installing Command Line Tool) Code.

This can be done by openinig XCode -> Menu -> Preference -> Components -> Command Line Tool

  1. Removing all but Python 2.7

I did installed different instances of python at different time and removing all but 2.7 was helpful in my case. Note : You may have to install modules after doing it. So get ready with pip/easy_install/ports.

Uninstall can be done with super easy steps mentioned in following link.

How to uninstall Python 2.7 on a Mac OS X 10.6.4?

What Regex would capture everything from ' mark to the end of a line?

/(\w*\(Hex\): w*)(.*?)(?= |$)/gm

I'm sure this one works, it will capture de hexa serial in the badly structured text multilined bellow

     Space Reservation: disabled
         Serial Number: wCVt1]IlvQWv
   Serial Number (Hex): 77435674315d496c76515776
               Comment: new comment

I'm a eternal newbie in regex but I'll try explain this one

(\w*(Hex): w*) : Find text in line where string contains "Hex: "

(.*?) This is the second captured text and means everything after

(?= |$) create a limit that is the space between = and the |

So with the second group, you will have the value

Convert float to string with precision & number of decimal digits specified?

Here a solution using only std. However, note that this only rounds down.

    float number = 3.14159;
    std::string num_text = std::to_string(number);
    std::string rounded = num_text.substr(0, num_text.find(".")+3);

For rounded it yields:


The code converts the whole float to string, but cuts all characters 2 chars after the "."

Convert an object to an XML string

    public static string Serialize(object dataToSerialize)
        if(dataToSerialize==null) return null;

        using (StringWriter stringwriter = new System.IO.StringWriter())
            var serializer = new XmlSerializer(dataToSerialize.GetType());
            serializer.Serialize(stringwriter, dataToSerialize);
            return stringwriter.ToString();

    public static T Deserialize<T>(string xmlText)
        if(String.IsNullOrWhiteSpace(xmlText)) return default(T);

        using (StringReader stringReader = new System.IO.StringReader(xmlText))
            var serializer = new XmlSerializer(typeof(T));
            return (T)serializer.Deserialize(stringReader);

Non-static method requires a target

I've found this issue to be prevalent in Entity Framework when we instantiate an Entity manually rather than through DBContext which will resolve all the Navigation Properties. If there are Foreign Key references (Navigation Properties) between tables and you use those references in your lambda (e.g. ProductDetail.Products.ID) then that "Products" context remains null if you manually created the Entity.

What is the difference between <html lang="en"> and <html lang="en-US">?

You can use any country code, yes, but that doesn't mean a browser or other software will recognize it or do anything differently because of it. For example, a screen reader might deal with "en-US" and "en-GB" the same if they only support an American accent in English. Another piece of software that has two distinct voices, though, could adjust according to the country code.

Tar a directory, but don't store full absolute paths in the archive

Low reputation (too many years of lurking, sigh) so I can't yet comment inline, but I found the answer from @laktak to be the only one that worked as intended on Ubuntu 18.04 -- using tar -cjf site1.tar.bz2 -C /var/www/site1 . on my machine resulted in all the files I wanted being under ./ inside the tar.bz2 file, which is probably ok but there is some risk of inconsistent behavior across OSs when un-tarring.

NSURLErrorDomain error codes description

IN SWIFT 3. Here are the NSURLErrorDomain error codes description in a Swift 3 enum: (copied from answer above and converted what i can).

enum NSURLError: Int {
    case unknown = -1
    case cancelled = -999
    case badURL = -1000
    case timedOut = -1001
    case unsupportedURL = -1002
    case cannotFindHost = -1003
    case cannotConnectToHost = -1004
    case connectionLost = -1005
    case lookupFailed = -1006
    case HTTPTooManyRedirects = -1007
    case resourceUnavailable = -1008
    case notConnectedToInternet = -1009
    case redirectToNonExistentLocation = -1010
    case badServerResponse = -1011
    case userCancelledAuthentication = -1012
    case userAuthenticationRequired = -1013
    case zeroByteResource = -1014
    case cannotDecodeRawData = -1015
    case cannotDecodeContentData = -1016
    case cannotParseResponse = -1017
    //case NSURLErrorAppTransportSecurityRequiresSecureConnection NS_ENUM_AVAILABLE(10_11, 9_0) = -1022
    case fileDoesNotExist = -1100
    case fileIsDirectory = -1101
    case noPermissionsToReadFile = -1102
    //case NSURLErrorDataLengthExceedsMaximum NS_ENUM_AVAILABLE(10_5, 2_0) =   -1103

    // SSL errors
    case secureConnectionFailed = -1200
    case serverCertificateHasBadDate = -1201
    case serverCertificateUntrusted = -1202
    case serverCertificateHasUnknownRoot = -1203
    case serverCertificateNotYetValid = -1204
    case clientCertificateRejected = -1205
    case clientCertificateRequired = -1206
    case cannotLoadFromNetwork = -2000

    // Download and file I/O errors
    case cannotCreateFile = -3000
    case cannotOpenFile = -3001
    case cannotCloseFile = -3002
    case cannotWriteToFile = -3003
    case cannotRemoveFile = -3004
    case cannotMoveFile = -3005
    case downloadDecodingFailedMidStream = -3006
    case downloadDecodingFailedToComplete = -3007

     case NSURLErrorInternationalRoamingOff NS_ENUM_AVAILABLE(10_7, 3_0) =         -1018
     case NSURLErrorCallIsActive NS_ENUM_AVAILABLE(10_7, 3_0) =                    -1019
     case NSURLErrorDataNotAllowed NS_ENUM_AVAILABLE(10_7, 3_0) =                  -1020
     case NSURLErrorRequestBodyStreamExhausted NS_ENUM_AVAILABLE(10_7, 3_0) =      -1021

     case NSURLErrorBackgroundSessionRequiresSharedContainer NS_ENUM_AVAILABLE(10_10, 8_0) = -995
     case NSURLErrorBackgroundSessionInUseByAnotherProcess NS_ENUM_AVAILABLE(10_10, 8_0) = -996
     case NSURLErrorBackgroundSessionWasDisconnected NS_ENUM_AVAILABLE(10_10, 8_0)= -997

Direct link to URLError.Code in the Swift github repository, which contains the up to date list of error codes being used (github link).

Split string on whitespace in Python

The str.split() method without an argument splits on whitespace:

>>> "many   fancy word \nhello    \thi".split()
['many', 'fancy', 'word', 'hello', 'hi']

How to convert a Binary String to a base 10 integer in Java

int foo = Integer.parseInt("1001", 2);

works just fine if you are dealing with positive numbers but if you need to deal with signed numbers you may need to sign extend your string then convert to an Int

public class bit_fun {
    public static void main(String[] args) {
        int x= (int)Long.parseLong("FFFFFFFF", 16);
        System.out.println("x =" +x);       

        x= (int)Long.parseLong(signExtend("1"), 2);
        System.out.println("x =" +x);

        x= (int)Long.parseLong(signExtend("0"), 2);
        System.out.println("x =" +x);

        x= (int)Long.parseLong(signExtend("1000"), 2);
        System.out.println("x =" +x);

        x= (int)Long.parseLong(signExtend("01000"), 2);
        System.out.println("x =" +x);

    private static String signExtend(String str){
        //TODO add bounds checking
        int n=32-str.length();
        char[] sign_ext = new char[n];
        Arrays.fill(sign_ext, str.charAt(0));

        return new String(sign_ext)+str;

x =-1
x =-1
x =0
x =-8
x =8 

I hope that helps!

How to get the selected date of a MonthCalendar control in C#

I just noticed that if you do:


you will get only the date (e.g. 1/25/2014) from a MonthCalendar control.

It's opposite to:


//The OUTPUT will be (e.g. 1/25/2014 12:00:00 AM)

Because these MonthCalendar properties are of type DateTime. See the msdn and the methods available to convert to a String representation. Also this may help to convert from a String to a DateTime object where applicable.

Change the icon of the exe file generated from Visual Studio 2010

Check the project properties. It's configurable there if you are using another .net windows application for example

Can we cast a generic object to a custom object type in javascript?

This is not exactly an answer, rather sharing my findings, and hopefully getting some critical argument for/against it, as specifically I am not aware how efficient it is.

I recently had a need to do this for my project. I did this using Object.assign, more precisely it is done something like this:Object.assign(new Person(...), anObjectLikePerson).

Here is link to my JSFiddle, and also the main part of the code:

function Person(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;

  this.getFullName = function() {
    return this.lastName + ' ' + this.firstName;

var persons = [{
  lastName: "Freeman",
  firstName: "Gordon"
}, {
  lastName: "Smith",
  firstName: "John"

var stronglyTypedPersons = [];
for (var i = 0; i < persons.length; i++) {
  stronglyTypedPersons.push(Object.assign(new Person("", ""), persons[i]));

Commenting code in Notepad++

In your n++ editor, you can go to Setting > Shortcut mapper and find all shortcut information as well as you can edit them :)

How to enable named/bind/DNS full logging?

I usually expand each log out into it's own channel and then to a separate log file, certainly makes things easier when you are trying to debug specific issues. So my logging section looks like the following:

logging {
    channel default_file {
        file "/var/log/named/default.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel general_file {
        file "/var/log/named/general.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel database_file {
        file "/var/log/named/database.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel security_file {
        file "/var/log/named/security.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel config_file {
        file "/var/log/named/config.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel resolver_file {
        file "/var/log/named/resolver.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel xfer-in_file {
        file "/var/log/named/xfer-in.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel xfer-out_file {
        file "/var/log/named/xfer-out.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel notify_file {
        file "/var/log/named/notify.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel client_file {
        file "/var/log/named/client.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel unmatched_file {
        file "/var/log/named/unmatched.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel queries_file {
        file "/var/log/named/queries.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel network_file {
        file "/var/log/named/network.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel update_file {
        file "/var/log/named/update.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel dispatch_file {
        file "/var/log/named/dispatch.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel dnssec_file {
        file "/var/log/named/dnssec.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;
    channel lame-servers_file {
        file "/var/log/named/lame-servers.log" versions 3 size 5m;
        severity dynamic;
        print-time yes;

    category default { default_file; };
    category general { general_file; };
    category database { database_file; };
    category security { security_file; };
    category config { config_file; };
    category resolver { resolver_file; };
    category xfer-in { xfer-in_file; };
    category xfer-out { xfer-out_file; };
    category notify { notify_file; };
    category client { client_file; };
    category unmatched { unmatched_file; };
    category queries { queries_file; };
    category network { network_file; };
    category update { update_file; };
    category dispatch { dispatch_file; };
    category dnssec { dnssec_file; };
    category lame-servers { lame-servers_file; };

Hope this helps.

JQuery/Javascript: check if var exists

To test for existence there are two methods.

a. "property" in object

This method checks the prototype chain for existence of the property.

b. object.hasOwnProperty( "property" )

This method does not go up the prototype chain to check existence of the property, it must exist in the object you are calling the method on.

var x; // variable declared in global scope and now exists

"x" in window; // true
window.hasOwnProperty( "x" ); //true

If we were testing using the following expression then it would return false

typeof x !== 'undefined'; // false

How to install APK from PC?

  1. Connect Android device to PC via USB cable and turn on USB storage.
  2. Copy .apk file to attached device's storage.
  3. Turn off USB storage and disconnect it from PC.
  4. Check the option Settings ? Applications ? Unknown sources OR Settings > Security > Unknown Sources.
  5. Open FileManager app and click on the copied .apk file. If you can't fine the apk file try searching or allowing hidden files. It will ask you whether to install this app or not. Click Yes or OK.

This procedure works even if ADB is not available.

node.js - how to write an array to file

A simple solution is to use writeFile :

     somepath,{ return v.join(', ') }).join('\n'),
     function (err) { console.log(err ? 'Error :'+err : 'ok') }

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

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

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

Maybe this suffices your needs:

mat$id <- rownames(mat) 

How to get base url in CodeIgniter 2.*

I know this is very late, but is useful for newbies. We can atuload url helper and it will be available throughout the application. For this in application\config\autoload.php modify as follows -

$autoload['helper'] = array('url'); 

C#: Looping through lines of multiline string

Here's a quick code snippet that will find the first non-empty line in a string:

string line1;
while (
    ((line1 = sr.ReadLine()) != null) &&
    ((line1 = line1.Trim()).Length == 0)
{ /* Do nothing - just trying to find first non-empty line*/ }

if(line1 == null){ /* Error - no non-empty lines in string */ }

Find a string between 2 known values

A Regex approach using lazy match and back-reference:

foreach (Match match in Regex.Matches(

git stash blunder: git stash pop and ended up with merge conflicts

I had a similar thing happen to me. I didn't want to stage the files just yet so I added them with git add and then just did git reset. This basically just added and then unstaged my changes but cleared the unmerged paths.

The provided URI scheme 'https' is invalid; expected 'http'. Parameter name: via

Adding this as an answer, just since you can't do much fancy formatting in comments.
I had the same issue, except I was creating and binding my web service client entirely in code.
Reason is the DLL was being uploaded into a system, which prohibited the use of config files.

Here is the code as it needed to be updated to communicate over SSL...

Public Function GetWebserviceClient() As WebWorker.workerSoapClient
    Dim binding = New BasicHttpBinding()
    binding.Name = "WebWorkerSoap"
    binding.CloseTimeout = TimeSpan.FromMinutes(1)
    binding.OpenTimeout = TimeSpan.FromMinutes(1)
    binding.ReceiveTimeout = TimeSpan.FromMinutes(10)
    binding.SendTimeout = TimeSpan.FromMinutes(1)

    binding.Security.Mode = BasicHttpSecurityMode.Transport

    Dim endpoint = New EndpointAddress("https://myurl/worker.asmx")

    Return New WebWorker.workerSoapClient(binding, endpoint)
End Function

How to trim a file extension from a String in JavaScript?

x.length-4 only accounts for extensions of 3 characters. What if you have filename.jpegor


To answer... sure, if you always have an extension of .jpg, x.length-4 would work just fine.

However, if you don't know the length of your extension, any of a number of solutions are better/more robust.

x = x.replace(/\..+$/, '');


x = x.substring(0, x.lastIndexOf('.'));


x = x.replace(/(.*)\.(.*?)$/, "$1");

OR (with the assumption filename only has one dot)

parts = x.match(/[^\.]+/);
x = parts[0];

OR (also with only one dot)

parts = x.split(".");
x = parts[0];

How to resize the jQuery DatePicker control

The Jacob Tsui solution works perfect for me:

    showButtonPanel: true,
    dateFormat: "mm/dd/yy",
    beforeShow: function(){ 
        $(".ui-datepicker").css('font-size', 12)

Resource u'tokenizers/punkt/english.pickle' not found

I got the solution:

import nltk

once the NLTK Downloader starts

d) Download l) List u) Update c) Config h) Help q) Quit

Downloader> d

Download which package (l=list; x=cancel)? Identifier> punkt

PHP - remove all non-numeric characters from a string

You can use preg_replace in this case;

$res = preg_replace("/[^0-9]/", "", "Every 6 Months" );

$res return 6 in this case.

If want also to include decimal separator or thousand separator check this example:

$res = preg_replace("/[^0-9.]/", "", "$ 123.099");

$res returns "123.099" in this case

Include period as decimal separator or thousand separator: "/[^0-9.]/"

Include coma as decimal separator or thousand separator: "/[^0-9,]/"

Include period and coma as decimal separator and thousand separator: "/[^0-9,.]/"

XAMPP - MySQL shutdown unexpectedly

If the answers mentioned above are not working, you can try deleting all the files in data, except for the folder

Goto: C:\xampp\mysql\data

enter image description here

After that: Goto: C:\xampp\mysql\bin

then open with notepad my.ini , Its look like this.

enter image description here

Then delete or put into comment the port 3306 and change it to 8111 then run xamp with administrator and its work well.

How to get text of an element in Selenium WebDriver, without including child element text?

def get_true_text(tag):
    children = tag.find_elements_by_xpath('*')
    original_text = tag.text
    for child in children:
        original_text = original_text.replace(child.text, '', 1)
    return original_text

file_get_contents behind a proxy?

Depending on how the proxy login works stream_context_set_default might help you.

$context  = stream_context_set_default(
      'header'=>'Authorization: Basic ' . base64_encode('username'.':'.'userpass')
$result = file_get_contents('http://..../...');

RESTful Authentication via Spring

You might consider Digest Access Authentication. Essentially the protocol is as follows:

  1. Request is made from client
  2. Server responds with a unique nonce string
  3. Client supplies a username and password (and some other values) md5 hashed with the nonce; this hash is known as HA1
  4. Server is then able to verify client's identity and serve up the requested materials
  5. Communication with the nonce can continue until the server supplies a new nonce (a counter is used to eliminate replay attacks)

All of this communication is made through headers, which, as jmort253 points out, is generally more secure than communicating sensitive material in the url parameters.

Digest Access Authentication is supported by Spring Security. Notice that, although the docs say that you must have access to your client's plain-text password, you can successfully authenticate if you have the HA1 hash for your client.

Get name of property as a string

There's a well-known hack to extract it from lambda expression (this is from the PropertyObserver class, by Josh Smith, in his MVVM foundation):

    private static string GetPropertyName<TPropertySource>
        (Expression<Func<TPropertySource, object>> expression)
        var lambda = expression as LambdaExpression;
        MemberExpression memberExpression;
        if (lambda.Body is UnaryExpression)
            var unaryExpression = lambda.Body as UnaryExpression;
            memberExpression = unaryExpression.Operand as MemberExpression;
            memberExpression = lambda.Body as MemberExpression;

        Debug.Assert(memberExpression != null, 
           "Please provide a lambda expression like 'n => n.PropertyName'");

        if (memberExpression != null)
            var propertyInfo = memberExpression.Member as PropertyInfo;

            return propertyInfo.Name;

        return null;

Sorry, this was missing some context. This was part of a larger class where TPropertySource is the class containing the property. You could make the function generic in TPropertySource to extract it from the class. I recommend taking a look at the full code from the MVVM Foundation.

Member '<method>' cannot be accessed with an instance reference

In C#, unlike VB.NET and Java, you can't access static members with instance syntax. You should do:


to refer to that property or remove the static modifier from Property1 (which is what you probably want to do). For a conceptual idea about what static is, see my other answer.

jQuery - add additional parameters on submit (NOT ajax)

You don't need to bind the submit event on the click of the submit button just bind the submit event and it will capture the submit event no mater how it gets triggered.

Think what you are wanting is to submit the sortable like you would via ajax. Try doing something like this:

var form = $('#event').submit(function () {
    $.each($('#attendance').sortable('toArray'),function(i, value){

Get google map link with latitude/longitude

The suggested answer no longer works after 2014. Now you have to use Google Maps Embed API for loading into iframe.

Here is the link for the question and solution.

If you are using Angular like me you won't be able to load the google maps in iframe because of XSS security issue. For that you need to sanitise the URL with Pipe from angular.

Here is the link to do so.

All the suggestions are tested and works 100% as of today.

How to create json by JavaScript for loop?

Your question is pretty hard to decode, but I'll try taking a stab at it.

You say:

I want to create a json object having two fields uniqueIDofSelect and optionValue in javascript.

And then you say:

I need output like


Well, this example output doesn't have the field named uniqueIDofSelect, it only has optionValue.

Anyway, you are asking for array of objects...

Then in the comment to michaels answer you say:

It creates json object array. but I need only one json object.

So you don't want an array of objects?

What do you want then?

Please make up your mind.

How do I decompile a .NET EXE into readable C# source code?

Reflector and the File Disassembler add-in from Denis Bauer. It actually produces source projects from assemblies, where Reflector on its own only displays the disassembled source.

ADDED: My latest favourite is JetBrains' dotPeek.

How to overcome "'aclocal-1.15' is missing on your system" warning?

2017 - High Sierra

It is really hard to get autoconf 1.15 working on Mac. We hired an expert to get it working. Everything worked beautifully.

Later I happened to upgrade a Mac to High Sierra.

The Docker pipeline stopped working!

Even though autoconf 1.15 is working fine on the Mac.

How to fix,

Short answer, I simply trashed the local repo, and checked out the repo again.

This suggestion is noted in the mix on this QA page and elsewhere.

It then worked fine!

It likely has something to do with the aclocal.m4 and similar files. (But who knows really). I endlessly massaged those files ... but nothing.

For some unknown reason if you just scratch your repo and get the repo again: everything works!

I tried for hours every combo of touching/deleting etc etc the files in question, but no. Just check out the repo from scratch!

Netbeans - class does not have a main method

While this may be an old question, the problem is still occurring these days, and the exact question is still not answered properly.

It is important to note that some projects have multiple classes with a main method.

In my case, I could run the project via the main class, but I could not run a particular other class that had a main method. The only thing that helped me was refactoring the class and renaming it. I've tried:

  • restart NetBeans
  • re-open the project
  • clear NetBeans cache
  • delete the file and create a new one with same name and contents
  • delete the file and create a new one with same name but very simple contents with only main method and print out message
  • rename the class (refactor) so a temp name and back
  • delete the project and create a new one with the same sources

The only thing that let me run this class is renaming it permanently. I think this must be some kind of a NetBeans bug.

Edit: Another thing that did help was completely uninstall Netbeans, wipe cache and any configuration files. It so happened that a newer Netbeans version was available so I installed it. But the old one would have probably worked too.

How do you clear a slice in Go?

It all depends on what is your definition of 'clear'. One of the valid ones certainly is:

slice = slice[:0]

But there's a catch. If slice elements are of type T:

var slice []T

then enforcing len(slice) to be zero, by the above "trick", doesn't make any element of


eligible for garbage collection. This might be the optimal approach in some scenarios. But it might also be a cause of "memory leaks" - memory not used, but potentially reachable (after re-slicing of 'slice') and thus not garbage "collectable".

Accessing Google Spreadsheets with C# using Google Data API

The most upvoted answer from @Kelly is no longer valid as @wescpy says. However after 2020-03-03 it will not work at all since the library used uses Google Sheets v3 API.

The Google Sheets v3 API will be shut down on March 3, 2020

This was announced 2019-09-10 by Google:

New code sample for Google Sheets v4 API:

Go to

and generate credentials.json. Then install Google.Apis.Sheets.v4 NuGet and try the following sample:

Note that I got the error Unable to parse range: Class Data!A2:E with the example code but with my spreadsheet. Changing to Sheet1!A2:E worked however since my sheet was named that. Also worked with only A2:E.

using Google.Apis.Auth.OAuth2;
using Google.Apis.Sheets.v4;
using Google.Apis.Sheets.v4.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;

namespace SheetsQuickstart
    class Program
        // If modifying these scopes, delete your previously saved credentials
        // at ~/.credentials/
        static string[] Scopes = { SheetsService.Scope.SpreadsheetsReadonly };
        static string ApplicationName = "Google Sheets API .NET Quickstart";

        static void Main(string[] args)
            UserCredential credential;

            using (var stream =
                new FileStream("credentials.json", FileMode.Open, FileAccess.Read))
                // The file token.json stores the user's access and refresh tokens, and is created
                // automatically when the authorization flow completes for the first time.
                string credPath = "token.json";
                credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                    new FileDataStore(credPath, true)).Result;
                Console.WriteLine("Credential file saved to: " + credPath);

            // Create Google Sheets API service.
            var service = new SheetsService(new BaseClientService.Initializer()
                HttpClientInitializer = credential,
                ApplicationName = ApplicationName,

            // Define request parameters.
            String spreadsheetId = "1BxiMVs0XRA5nFMdKvBdBZjgmUUqptlbs74OgvE2upms";
            String range = "Class Data!A2:E";
            SpreadsheetsResource.ValuesResource.GetRequest request =
                    service.Spreadsheets.Values.Get(spreadsheetId, range);

            // Prints the names and majors of students in a sample spreadsheet:
            ValueRange response = request.Execute();
            IList<IList<Object>> values = response.Values;
            if (values != null && values.Count > 0)
                Console.WriteLine("Name, Major");
                foreach (var row in values)
                    // Print columns A and E, which correspond to indices 0 and 4.
                    Console.WriteLine("{0}, {1}", row[0], row[4]);
                Console.WriteLine("No data found.");

OWIN Security - How to Implement OAuth2 Refresh Tokens

I don't think that you should be using an array to maintain tokens. Neither you need a guid as a token.

You can easily use context.SerializeTicket().

See my below code.

public class RefreshTokenProvider : IAuthenticationTokenProvider
    public async Task CreateAsync(AuthenticationTokenCreateContext context)

    public async Task ReceiveAsync(AuthenticationTokenReceiveContext context)

    public void Create(AuthenticationTokenCreateContext context)
        object inputs;
        context.OwinContext.Environment.TryGetValue("Microsoft.Owin.Form#collection", out inputs);

        var grantType = ((FormCollection)inputs)?.GetValues("grant_type");

        var grant = grantType.FirstOrDefault();

        if (grant == null || grant.Equals("refresh_token")) return;

        context.Ticket.Properties.ExpiresUtc = DateTime.UtcNow.AddDays(Constants.RefreshTokenExpiryInDays);


    public void Receive(AuthenticationTokenReceiveContext context)

        if (context.Ticket == null)
            context.Response.StatusCode = 400;
            context.Response.ContentType = "application/json";
            context.Response.ReasonPhrase = "invalid token";

        if (context.Ticket.Properties.ExpiresUtc <= DateTime.UtcNow)
            context.Response.StatusCode = 401;
            context.Response.ContentType = "application/json";
            context.Response.ReasonPhrase = "unauthorized";

        context.Ticket.Properties.ExpiresUtc = DateTime.UtcNow.AddDays(Constants.RefreshTokenExpiryInDays);

How to delete a whole folder and content?

public static void deleteDirectory( File dir )

    if ( dir.isDirectory() )
        String [] children = dir.list();
        for ( int i = 0 ; i < children.length ; i ++ )
         File child =    new File( dir , children[i] );
             deleteDirectory( child );


How to download a file from a website in C#

Also you can use DownloadFileAsync method in WebClient class. It downloads to a local file the resource with the specified URI. Also this method does not block the calling thread.


    webClient.DownloadFileAsync(new Uri(""), "test.jpg");

For more information:

invalid_grant trying to get oAuth token from google

There is a undocumented timeout between when you first redirect the user to the google authentication page (and get back a code), and when you take the returned code and post it to the token url. It works fine for me with the actual google supplied client_id as opposed to an "undocumented email address". I just needed to start the process again.

How to get a specific output iterating a hash in Ruby?

The most basic way to iterate over a hash is as follows:

hash.each do |key, value|
  puts key
  puts value

How to get files in a relative path in C#

As others have said, you can/should prepend the string with @ (though you could also just escape the backslashes), but what they glossed over (that is, didn't bring it up despite making a change related to it) was the fact that, as I recently discovered, using \ at the beginning of a pathname, without . to represent the current directory, refers to the root of the current directory tree.

C:\foo\bar>cd \


C:\foo\bar>cd .\

(Using . by itself has the same effect as using .\ by itself, from my experience. I don't know if there are any specific cases where they somehow would not mean the same thing.)

You could also just leave off the leading .\ , if you want.

C:\foo>cd bar

In fact, if you really wanted to, you don't even need to use backslashes. Forwardslashes work perfectly well! (Though a single / doesn't alias to the current drive root as \ does.)

C:\>cd foo/bar

You could even alternate them.

C:\>cd foo/bar\baz

...I've really gone off-topic here, though, so feel free to ignore all this if you aren't interested.

How to use OKHTTP to make a post request?

As per the docs, OkHttp version 3 replaced FormEncodingBuilder with FormBody and FormBody.Builder(), so the old examples won't work anymore.

Form and Multipart bodies are now modeled. We've replaced the opaque FormEncodingBuilder with the more powerful FormBody and FormBody.Builder combo.

Similarly we've upgraded MultipartBuilder into MultipartBody, MultipartBody.Part, and MultipartBody.Builder.

So if you're using OkHttp 3.x try the following example:

OkHttpClient client = new OkHttpClient();

RequestBody formBody = new FormBody.Builder()
        .add("message", "Your message")
Request request = new Request.Builder()

try {
    Response response = client.newCall(request).execute();

    // Do something with the response.
} catch (IOException e) {

Getting full URL of action in ASP.NET MVC

This what you need to do.

@Url.Action(action,controller, null, Request.Url.Scheme)

How to filter Pandas dataframe using 'in' and 'not in' like in SQL

I wanted to filter out dfbc rows that had a BUSINESS_ID that was also in the BUSINESS_ID of dfProfilesBusIds

dfbc = dfbc[~dfbc['BUSINESS_ID'].isin(dfProfilesBusIds['BUSINESS_ID'])]

What does "if (" mean?

I'm presuming you're using Java 6 and that the ResultSet that you're using is a java.sql.ResultSet.

The JavaDoc for the method states:

Moves the cursor froward one row from its current position. A ResultSet cursor is initially positioned before the first row; the first call to the method next makes the first row the current row; the second call makes the second row the current row, and so on.

When a call to the next method returns false, the cursor is positioned after the last row. Any invocation of a ResultSet method which requires a current row will result in a SQLException being thrown.

So, if({ //do something } means "If the result set still has results, move to the next result and do something".

As BalusC pointed out, you need to replace

ResultSet rs = stmt.executeQuery(sql);


ResultSet rs = stmt.executeQuery();

Because you've already set the SQL to use in the statement with your previous line

PreparedStatement stmt = conn.prepareStatement(sql);

If you weren't using the PreparedStatement, then ResultSet rs = stmt.executeQuery(sql); would work.

How to parse float with two decimal places in javascript?

You can use toFixed() to do that

var twoPlacedFloat = parseFloat(yourString).toFixed(2)

Getting the first index of an object

There is no way to get the first element, seeing as "hashes" (objects) in JavaScript have unordered properties. Your best bet is to store the keys in an array:

var keys = ["foo", "bar", "baz"];

Then use that to get the proper value:


You must add a reference to assembly 'netstandard, Version=

I was facing this problem when trying to add a .NETStandard dependency to a .NET4.6.1 library, and compiling it in Linux with Mono 4.6.2 (the version that comes with Ubuntu 16.04).

I finally solved it today; the solution requires to do both of these things:

  1. Change <TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion> to <TargetFrameworkVersion>v4.7.1</TargetFrameworkVersion> in the .csproj file.
  2. Upgrade your mono to a newer version. I believe 5.x should work, but to be sure, you can just install Ubuntu 20.04 (which at the time of writing is only in preview), which includes Mono

AngularJS - add HTML element to dom in directive without jQuery

Why not to try simple (but powerful) html() method:

iElement.html('<svg width="600" height="100" class="svg"></svg>');

Or append as an alternative:

iElement.append('<svg width="600" height="100" class="svg"></svg>');

And , of course , more cleaner way:

 var svg = angular.element('<svg width="600" height="100" class="svg"></svg>');


Reset all the items in a form

You can reset all controls of a certain type. Something like

foreach(TextBox tb in this.Controls.OfType<TextBox>().ToArray())

But you can't reset all controls at once

Access Form - Syntax error (missing operator) in query expression

Try making the field names legal by removing spaces. It's a long shot but it has actually helped me before.

How to list files inside a folder with SQL Server

If you want you can achieve this using a CLR Function/Assembly.

  1. Create a SQL Server CLR Assembly Project.
  2. Go to properties and ensure the permission level on the Connection is setup to external
  3. Add A Sql Function to the Assembly.

Here's an example which will allow you to select form your result set like a table.

public partial class UserDefinedFunctions
    [SqlFunction(DataAccess = DataAccessKind.Read,
        FillRowMethodName = "GetFiles_FillRow", TableDefinition = "FilePath nvarchar(4000)")]
    public static IEnumerable GetFiles(SqlString path)
        return System.IO.Directory.GetFiles(path.ToString()).Select(s => new SqlString(s));

    public static void GetFiles_FillRow(object obj,out SqlString filePath)
        filePath = (SqlString)obj;

And your SQL query.

use MyDb

select * From GetFiles('C:\Temp\');

Be aware though, your database needs to have CLR Assembly functionaliy enabled using the following SQL Command.

sp_configure 'clr enabled', 1

CLR Assemblies (like XP_CMDShell) are disabled by default so if the reason for not using XP Cmd Shell is because you don't have permission, then you may be stuck with this option as well... just FYI.

How to use auto-layout to move other views when a view is hidden?

I think this is the most simple answer. Please verify that it works:

        StackFullView.layer.isHidden = true
        Task_TopSpaceSections.constant = 0.   //your constraint of top view

check here

"A referral was returned from the server" exception when accessing AD from C#

Probably the path you supplied was not correct. Check that.

I would recomment the article Howto: (Almost) Everything In Active Directory via C# which really helped me in the past in dealing with AD.

Is Android using NTP to sync time?

i wanted to ask if Android Devices uses the network time protocol (ntp) to synchronize the time.

For general time synchronization, devices with telephony capability, where the wireless provider provides NITZ information, will use NITZ. My understanding is that NTP is used in other circumstances: NITZ-free wireless providers, WiFi-only, etc.

Your cited blog post suggests another circumstance: on-demand time synchronization in support of GPS. That is certainly conceivable, though I do not know whether it is used or not.

rotate image with css

The trouble looks like the image isn't square and the browser adjusts as such. After rotation ensure the dimensions are retained by changing the image margin.

.imagetest img {
  transform: rotate(270deg);
  margin: 10px 0px;

The amount will depend on the difference in height x width of the image. You may also need to add display:inline-block; or display:block to get it to recognize the margin parameter.

OpenSSL: PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: TRUSTED CERTIFICATE

My situation was a little different. The solution was to strip the .pem from everything outside of the CERTIFICATE and PRIVATE KEY sections and to invert the order which they appeared. After converting from pfx to pem file, the certificate looked like this:

Bag Attributes
localKeyID: ...
Bag Attributes
more garbage...

After correcting the file, it was just:


How to determine if OpenSSL and mod_ssl are installed on Apache2

Enable mod_ssl in httpd.conf and restart the apache. You will see the openssl information in error.log as below

[Fri Mar 23 15:13:38.448268 2018] [mpm_worker:notice] [pid 8891:tid 1] AH00292: Apache/2.4.29 (Unix) OpenSSL/1.0.2n configured -- resuming normal operations_x000D_
[Fri Mar 23 15:13:38.448502 2018] [core:notice] [pid 8891:tid 1] AH00094: Command line: '/opt/apps/apache64/2.4.29/bin/httpd'

Concatenate text files with Windows command line, dropping leading lines

I know you said that you couldn't install any software, but I'm not sure how tight that restriction is. Anyway, I had the same issue (trying to concatenate two files with presumably the same headers) and I thought I'd provide an alternative answer for others who arrive at this page, since it worked just great for me.

After trying a whole bunch of commands in windows and being severely frustrated, and also trying all sorts of graphical editors that promised to be able to open large files, but then couldn't, I finally got back to my Linux roots and opened my Cygwin prompt. Two commands:

cp file1.csv out.csv
tail -n+2 file2.csv >> out.csv

For file1.csv 800MB and file2.csv 400MB, those two commands took under 5 seconds on my machine. In a Cygwin prompt, no less. I thought Linux commands were supposed to be slow in Cygwin but that approach took far less effort and was way easier than any windows approach I could find.

"Could not get any response" response when using postman with subdomain

In my case, I forgot to set the value of the variable in the "CURRENT VALUE" field.

HTML: Image won't display?

If you put <img src="iwojimaflag.jpg"/> in html code then place iwojimaflag.jpg and html file in same folder.

If you put <img src="images/iwojimaflag.jpg"/> then you must create "images" folder and put image iwojimaflag.jpg in that folder.

How to tell if a string contains a certain character in JavaScript?

Demonstration: The include() method finds the “contains” character in whole string, it will return a true.

var string = "This is a and this tutorial contains javascript include() method examples."_x000D_
//The output of this_x000D_

SQL select statements with multiple tables

You need to join the two tables:

select, p.first, p.middle, p.last, p.age, as address_id, a.street,, a.state,
from Person p inner join Address a on = a.person_id
where = '97229';

This will select all of the columns from both tables. You could of course limit that by choosing different columns in the select clause.

Responsive Bootstrap Jumbotron Background Image

You could try this:

Simply place the code in a style tag in the head of the html file

        .jumbotron {_x000D_
            background: url("") center center / cover no-repeat;_x000D_

or put it in a separate css file as shown below

        .jumbotron {_x000D_
            background: url("") center center / cover no-repeat;_x000D_

use center center to center the image horizontally and vertically. use cover to make the image fill out the jumbotron space and finally no-repeat so that the image is not repeated.

MySQL set current date in a DATETIME field on insert

    SET NEW.created_date = NOW();

Sending mail attachment using Java

This worked for me.

Here I assume my attachment is of a PDF type format.

Comments are made to understand it clearly.

public class MailAttachmentTester {
    public static void main(String[] args) {
        // Recipient's email ID needs to be mentioned.
        String to = "[email protected]";
        // Sender's email ID needs to be mentioned
        String from = "[email protected]";
        final String username = "[email protected]";//change accordingly
        final String password = "test";//change accordingly
        // Assuming you are sending email through
        Properties props = new Properties();
        props.put("", "");
        props.put("mail.smtp.socketFactory.port", "465");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", "465");
        // Get the Session object.
        Session session = Session.getInstance(props,
                new javax.mail.Authenticator() {
                    protected PasswordAuthentication getPasswordAuthentication() {
                        return new PasswordAuthentication(username, password);
        try {
            // Create a default MimeMessage object.
            Message message = new MimeMessage(session);
            // Set From: header field of the header.
            message.setFrom(new InternetAddress(from));
            // Set To: header field of the header.
            // Set Subject: header field
            // Create the message part
            BodyPart messageBodyPart = new MimeBodyPart();
            // Now set the actual message
            messageBodyPart.setText("Please find the attachment below");
            // Create a multipar message
            Multipart multipart = new MimeMultipart();
            // Set text message part
            // Part two is attachment
            messageBodyPart = new MimeBodyPart();
            String filename = "D:/test.PDF";
            DataSource source = new FileDataSource(filename);
            messageBodyPart.setDataHandler(new DataHandler(source));
            // Send the complete message parts
            // Send message
            System.out.println("Email Sent Successfully !!");
        } catch (MessagingException e) {
            throw new RuntimeException(e);


Get and Set Screen Resolution

For retrieving the screen resolution, you're going to want to use the System.Windows.Forms.Screen class. The Screen.AllScreens property can be used to access a collection of all of the displays on the system, or you can use the Screen.PrimaryScreen property to access the primary display.

The Screen class has a property called Bounds, which you can use to determine the resolution of the current instance of the class. For example, to determine the resolution of the current screen:

Rectangle resolution = Screen.PrimaryScreen.Bounds;

For changing the resolution, things get a little more complicated. This article (or this one) provides a detailed implementation and explanation. Hope this helps.

Fastest way to check a string is alphanumeric in Java

I've written the tests that compare using regular expressions (as per other answers) against not using regular expressions. Tests done on a quad core OSX10.8 machine running Java 1.6

Interestingly using regular expressions turns out to be about 5-10 times slower than manually iterating over a string. Furthermore the isAlphanumeric2() function is marginally faster than isAlphanumeric(). One supports the case where extended Unicode numbers are allowed, and the other is for when only standard ASCII numbers are allowed.

public class QuickTest extends TestCase {

    private final int reps = 1000000;

    public void testRegexp() {
        for(int i = 0; i < reps; i++)

public void testIsAlphanumeric() {
    for(int i = 0; i < reps; i++)

public void testIsAlphanumeric2() {
    for(int i = 0; i < reps; i++)

    public boolean isAlphanumeric(String str) {
        for (int i=0; i<str.length(); i++) {
            char c = str.charAt(i);
            if (!Character.isLetterOrDigit(c))
                return false;

        return true;

    public boolean isAlphanumeric2(String str) {
        for (int i=0; i<str.length(); i++) {
            char c = str.charAt(i);
            if (c < 0x30 || (c >= 0x3a && c <= 0x40) || (c > 0x5a && c <= 0x60) || c > 0x7a)
                return false;
        return true;


Logical XOR operator in C++?

There is another way to do XOR:

bool XOR(bool a, bool b)
    return (a + b) % 2;

Which obviously can be demonstrated to work via:

#include <iostream>

bool XOR(bool a, bool b)
    return (a + b) % 2;

int main()
    using namespace std;
    cout << "XOR(true, true):\t" << XOR(true, true) << endl
         << "XOR(true, false):\t" << XOR(true, false) << endl
         << "XOR(false, true):\t" << XOR(false, true) << endl
         << "XOR(false, false):\t" << XOR(false, false) << endl
         << "XOR(0, 0):\t\t" << XOR(0, 0) << endl
         << "XOR(1, 0):\t\t" << XOR(1, 0) << endl
         << "XOR(5, 0):\t\t" << XOR(5, 0) << endl
         << "XOR(20, 0):\t\t" << XOR(20, 0) << endl
         << "XOR(6, 6):\t\t" << XOR(5, 5) << endl
         << "XOR(5, 6):\t\t" << XOR(5, 6) << endl
         << "XOR(1, 1):\t\t" << XOR(1, 1) << endl;
    return 0;

SSRS Expression for IF, THEN ELSE

You should be able to use

IIF(Fields!ExitReason.Value = 7, 1, 0)

Getting started with OpenCV 2.4 and MinGW on Windows 7

This isn't working for me. I spent few days following every single tutorial I found on net and finally i compiled my own binaries. Everyting is described here: OpenVC 2.4.5, eclipse CDT Juno, MinGW error 0xc0000005

After many trials and errors I decided to follow this tutorial and to compile my own binaries as it seems that too many people are complaining that precompiled binaries are NOT working for them. Eclipse CDT Juno was already installed.

My procedure was as follows:

  1. Download and install MinGW and add to the system PATH with c:/mingw/bin
  2. Download cmake from and install it
  3. Download OpenCV2.4.5 Windows version
  4. Install/unzip Opencv to C:\OpenCV245PC\ (README,index.rst and CMakeLists.txt are there with all subfolders)
  5. Run CMake GUI tool, then
  6. Choose C:\OpenCV245PC\ as source
  7. Choose the destination, C:\OpenCV245MinGW\x86 where to build the binaries
  8. Press Configure button, choose MinGW Makefiles as the generator. There are some red highlights in the window, choose options as you need.
  9. Press the Configure button again. Configuring is now done.
  10. Press the Generate button.
  11. Exit the program when the generating is done.
  12. Exit the Cmake program.
  13. Run the command line mode (cmd.exe) and go to the destination directory C:\OpenCV245MinGW\x86
  14. Type "mingw32-make". You will see a progress of building binaries. If the command is not found, you must make sure that the system PATH is added with c:/mingw/bin. The build continues according the chosen options to a completion.
  15. In Windows system PATH (My Computer > Right button click > Properties > Advanced > Environment Variables > Path) add the destination's bin directory, C:\OpenCV245MinGW\x86\bin
  17. Go to the Eclipse CDT IDE, create a C++ program using the sample OpenCV code (You can use code from top of this topic).
  18. Go to Project > Properties > C/C++ Build > Settings > GCC C++ Compiler > Includes, and add the source OpenCV folder "C:\OpenCV245PC\build\include"
  19. Go to Project > Properties > C/C++ Build > Settings > MinGW C++ Linker > Libraries, and add to the Libraries (-l) ONE BY ONE (this could vary from project to project, you can add all of them if you like or some of them just the ones that you need for your project): opencv_calib3d245 opencv_contrib245 opencv_core245 opencv_features2d245 opencv_flann245 opencv_gpu245 opencv_highgui245 opencv_imgproc245 opencv_legacy245 opencv_ml245 opencv_nonfree245 opencv_objdetect245 opencv_photo245 opencv_stitching245 opencv_video245 opencv_videostab245
  20. Add the built OpenCV library folder, "C:\OpenCV245MinGW\x86\lib" to Library search path (-L).

You can use this code to test your setup:

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

int main()

Mat img = imread("c:/lenna.png", CV_LOAD_IMAGE_COLOR);

namedWindow("MyWindow", CV_WINDOW_AUTOSIZE);
imshow("MyWindow", img);

return 0;

Don't forget to put image to the C:/ (or wherever you might find suitable, just be sure that eclipse have read acess.

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";_x000D_
const substring = "oo";_x000D_

includes doesn’t have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:

var string = "foo";_x000D_
var substring = "oo";_x000D_
console.log(string.indexOf(substring) !== -1);

How to check if a windows form is already open, and close it if it is?

Form only once

If your goal is to diallow multiple instaces of a form, consider following ...

public class MyForm : Form
    private static MyForm alreadyOpened = null;

    public MyForm()
        // If the form already exists, and has not been closed
        if (alreadyOpened != null && !alreadyOpened.IsDisposed)
            alreadyOpened.Focus();            // Bring the old one to top
            Shown += (s, e) => this.Close();  // and destroy the new one.

        // Otherwise store this one as reference
        alreadyOpened = this;  

        // Initialization

RegEx for Javascript to allow only alphanumeric

If you wanted to return a replaced result, then this would work:

var a = 'Test123*** TEST';
var b = a.replace(/[^a-z0-9]/gi,'');

This would return:


Note that the gi is necessary because it means global (not just on the first match), and case-insensitive, which is why I have a-z instead of a-zA-Z. And the ^ inside the brackets means "anything not in these brackets".

WARNING: Alphanumeric is great if that's exactly what you want. But if you're using this in an international market on like a person's name or geographical area, then you need to account for unicode characters, which this won't do. For instance, if you have a name like "Âlvarö", it would make it "lvar".

How to add icons to React Native app

I would use a service to scale the icon correctly. seems good. Use a image on the larger size as scaling up a smaller image can lead to the larger icons being pixelated. That site will give you sizes for both iOS and Android.

From there its just a matter of setting the icon like you would a regular native app.

Set icon for Android application

Unsupported major.minor version 52.0 in my app

You need to go into your SDK installation directory, and make sure that the /build-tools sub-directory matches the buildToolsVersion in your app's build.gradle file: enter image description here

How to filter a dictionary according to an arbitrary condition function?

>>> points = {'a': (3, 4), 'c': (5, 5), 'b': (1, 2), 'd': (3, 3)}
>>> dict(filter(lambda x: (x[1][0], x[1][1]) < (5, 5), points.items()))

{'a': (3, 4), 'b': (1, 2), 'd': (3, 3)}

R - Markdown avoiding package loading messages

This is an old question, but here's another way to do it.

You can modify the R code itself instead of the chunk options, by wrapping the source call in suppressPackageStartupMessages(), suppressMessages(), and/or suppressWarnings(). E.g:

```{r echo=FALSE}

You can also put those functions around your library() calls inside the "source.R" script.

How to get the excel file name / path in VBA

If you mean VBA, then you can use FullName, for example:

strFileFullName = ThisWorkbook.FullName

(updated as considered by the comments: the former used ActiveWorkbook.FullName could more likely be wrong, if other office files may be open(ed) and active. But in case you stored the macro in another file, as mentioned by user @user7296559 here, and really want the file name of the macro-using file, ActiveWorkbook could be the correct choice, if it is guaranteed to be active at execution time.)

Implementing a HashMap in C

The best approach depends on the expected key distribution and number of collisions. If relatively few collisions are expected, it really doesn't matter which method is used. If lots of collisions are expected, then which to use depends on the cost of rehashing or probing vs. manipulating the extensible bucket data structure.

But here is source code example of An Hashmap Implementation in C

How to convert SQL Server's timestamp column to datetime format

After impelemtation of conversion to integer CONVERT(BIGINT, [timestamp]) as Timestamp I've got the result like

446701117 446701118 446701119 446701120 446701121 446701122 446701123 446701124 446701125 446701126

Yes, this is not a date and time, It's serial numbers

Bootstrap Carousel Full Screen

This is how I did it. This makes the images in the slideshow take up the full screen if it´s aspect ratio allows it, othervice it scales down.

.carousel {
    height: 100vh;
    width: 100%;
.carousel .carousel-inner {

To allways get a full screen slideshow, no matter screen aspect ratio, you can also use object-fit: (doesn´t work in IE or Edge)

.carousel .carousel-inner img {
    object-fit: cover;

jQuery check if it is clicked or not

This is the one that i've tried & it works pretty well for me

$('.mybutton').on('click', function() {
       if (!$(this).data('clicked')) {
           //do your stuff here if the button is not clicked
           $(this).data('clicked', true);
       } else {
           //do your stuff here if the button is clicked
           $(this).data('clicked', false);


for more reference check this link JQuery toggle click

SQL Server - find nth occurrence in a string


How to launch an EXE from Web page (

if the applications are C#, you can use ClickOnce deployment, which is a good option if you can't guarentee the user will have the app, however you'll have to re-build the apps with deployment options and grab some boilerplate code from each project.

You can also use Javascript.

Or you can register an application to handle a new web protocol you can define. This could also be an "app selection" protocol, so each time an app is clicked it would link to a page on your new protocol, all handling of this protocol is then passed to your "selection app" which uses arguments to find and launch an app on the clients PC.