Programs & Examples On #Unspecified behavior

Unpredictable, but valid, behavior of a program that an implementation is not required to document.

What is the strict aliasing rule?

As addendum to what Doug T. already wrote, here is a simple test case which probably triggers it with gcc :


#include <stdio.h>

void check(short *h,long *k)
    if (*h == 5)
        printf("strict aliasing problem\n");

int main(void)
    long      k[1];
    check((short *)k,k);
    return 0;

Compile with gcc -O2 -o check check.c . Usually (with most gcc versions I tried) this outputs "strict aliasing problem", because the compiler assumes that "h" cannot be the same address as "k" in the "check" function. Because of that the compiler optimizes the if (*h == 5) away and always calls the printf.

For those who are interested here is the x64 assembler code, produced by gcc 4.6.3, running on ubuntu 12.04.2 for x64:

movw    $5, (%rdi)
movq    $6, (%rsi)
movl    $.LC0, %edi
jmp puts

So the if condition is completely gone from the assembler code.

SVN checkout the contents of a folder, not the folder itself

Just add a . to it:

svn checkout file:///home/landonwinters/svn/waterproject/trunk .

That means: check out to current directory.

How to install MySQLdb (Python data access library to MySQL) on Mac OS X?

export PATH=$PATH:/usr/local/mysql/bin/

should fix the issue for you as the system is not able to find the mysql_config file.

Resize an Array while keeping current elements in Java?

Standard class java.util.ArrayList is resizable array, growing when new elements added.

Is Eclipse the best IDE for Java?

Don't forget that Eclipse Platform was started by IBM. There are few platforms out there.

  • IBM Websphere Application Developer (WSAD) and/or Rational Application Developer (RAD) which is a Eclipse-type IDE from IBM (actually, that's Eclipse with IBM specialized libraries/plugins).
  • MyEclipse (never used it but it's another Eclipse-type IDE)
  • Sun Microsystem's NetBeans. It's too Java-centric as it's designed to create applications purely in java (NetBeans runs in Java).
  • IntelliJ (to name but a few)
  • Oracle JDeveloper (I never really liked the directory structure layout JDeveloper creates).

The advantage with Eclipse is that it can be customized to your development pleasure, plugins can be written for Eclipse to conform to your needs (e.g. The Eclipse "Easy Explorer" plugin for browsing the directory of your source in Windows Explorer). Eclipse allows you to also incorporate other languages/SDK's, such as C++, Silverlight projects, Android Projects for development. You can also easily manage resources in Eclipse.

In my experience NetBeans are resource intensive. Oracle JDeveloper and IntelliJ aren't free though. Oh yes, If you have issues or bugs with Eclipse, Eclipse has the ability to restart and submit the crash to Eclipse servers.

Decoding UTF-8 strings in Python

You need to properly decode the source text. Most likely the source text is in UTF-8 format, not ASCII.

Because you do not provide any context or code for your question it is not possible to give a direct answer.

I suggest you study how unicode and character encoding is done in Python:

How to Cast Objects in PHP

PHP provides a very simple way of doing this by using:

(object) ['id'=>1,'name'=>'cat']

In your case you try this:

$dog = json_encode($dog);

$cat = (object) json_decode($dog)

More optimize method is:

$dog = (array)$dog;
$dog['newfield'] = 'xyz';
$dog = (object)$dog;

How should I import data from CSV into a Postgres table using pgAdmin 3?

You may have a table called 'test'

COPY test(gid, "name", the_geom)
FROM '/home/data/sample.csv'

Adding open/closed icon to Twitter Bootstrap collapsibles (accordions)

Another no-javascript solution that uses the collapse functionality itself:

/* Prevent block display and transition animation */, {
  display: inline; }
.expand-icon.collapsing {
  display: none; }

/* HTML Toggler with glyphicons */
<a data-toggle="collapse" href=".my-collapse">
 <span class="my-collapse collapse-icon collapse in">
  <span class="glyphicon glyphicon-collapse-up"></span>
 <span class="my-collapse expand-icon collapse">
  <span class="glyphicon glyphicon-expand"></span>   

Understanding the order() function

This could help you at some point.

a <- c(45,50,10,96)

What you get is

[1] 10 45 50 96

The code I wrote indicates you want "a" as a whole subset of "a" and you want it ordered from the lowest to highest value.

Xcode couldn't find any provisioning profiles matching


  1. Unique name (across all Apple Apps)
  2. Have to sign in while your phone is connected (mine had a large warning here)

Worked great without restart on Xcode 10


Remove all child elements of a DOM node in JavaScript


It's experimental without wide support, but when executed with no params will do what you're asking for, and it's more efficient than looping through each child and removing it. As mentioned already, replacing innerHTML with an empty string will require HTML parsing on the browser's part.

Documentation here.

Why do we use arrays instead of other data structures?

Not all programs do the same thing or run on the same hardware.

This is usually the answer why various language features exist. Arrays are a core computer science concept. Replacing arrays with lists/matrices/vectors/whatever advanced data structure would severely impact performance, and be downright impracticable in a number of systems. There are any number of cases where using one of these "advanced" data collection objects should be used because of the program in question.

In business programming (which most of us do), we can target hardware that is relatively powerful. Using a List in C# or Vector in Java is the right choice to make in these situations because these structures allow the developer to accomplish the goals faster, which in turn allows this type of software to be more featured.

When writing embedded software or an operating system an array may often be the better choice. While an array offers less functionality, it takes up less RAM, and the compiler can optimize code more efficiently for look-ups into arrays.

I am sure I am leaving out a number of the benefits for these cases, but I hope you get the point.

Hide the browse button on a input type=file

Came across this question and didn't feel like any of the answers were clean. Here is my solution:

  <span>Select file</span>
  <input type="file" style="display: none">

When you click the label the select file dialog will open. No js needed to make it happen.

You can style the label to look like a button.

Here is an example using w3css and font awesome:

<label class="w3-button w3-blue w3-round">
    <span><i class="fas fa-image"></i></span>
    <input type="file" style="display: none" >

Of course you need to add an event listener to the input to detect a file was chosen.

How to disable keypad popup when on edittext?

It issue can be sorted by using, No need to set editText inputType to any values, just add the below line, editText.setTextIsSelectable(true);

Is it better practice to use String.format over string Concatenation in Java?

I think we can go with MessageFormat.format as it should be good at both readability and also performance aspects.

I used the same program which one used by Icaro in his above answer and I enhanced it with appending code for using MessageFormat to explain the performance numbers.

  public static void main(String[] args) {
    long start = System.currentTimeMillis();
    for (int i = 0; i < 1000000; i++) {
      String s = "Hi " + i + "; Hi to you " + i * 2;
    long end = System.currentTimeMillis();
    System.out.println("Concatenation = " + ((end - start)) + " millisecond");

    start = System.currentTimeMillis();
    for (int i = 0; i < 1000000; i++) {
      String s = String.format("Hi %s; Hi to you %s", i, +i * 2);
    end = System.currentTimeMillis();
    System.out.println("Format = " + ((end - start)) + " millisecond");

    start = System.currentTimeMillis();
    for (int i = 0; i < 1000000; i++) {
      String s = MessageFormat.format("Hi %s; Hi to you %s", i, +i * 2);
    end = System.currentTimeMillis();
    System.out.println("MessageFormat = " + ((end - start)) + " millisecond");

Concatenation = 69 millisecond

Format = 1435 millisecond

MessageFormat = 200 millisecond


As per SonarLint Report, Printf-style format strings should be used correctly (squid:S3457)

Because printf-style format strings are interpreted at runtime, rather than validated by the compiler, they can contain errors that result in the wrong strings being created. This rule statically validates the correlation of printf-style format strings to their arguments when calling the format(...) methods of java.util.Formatter, java.lang.String,, MessageFormat, and classes and the printf(...) methods of or classes.

I replace the printf-style with the curly-brackets and I got something interesting results as below.

Concatenation = 69 millisecond
Format = 1107 millisecond
Format:curly-brackets = 416 millisecond
MessageFormat = 215 millisecond
MessageFormat:curly-brackets = 2517 millisecond

My Conclusion:
As I highlighted above, using String.format with curly-brackets should be a good choice to get benefits of good readability and also performance.

Using awk to print all columns from the nth to the last

Perl solution:

perl -lane 'splice @F,0,1; print join " ",@F' file

These command-line options are used:

  • -n loop around every line of the input file, do not automatically print every line

  • -l removes newlines before processing, and adds them back in afterwards

  • -a autosplit mode – split input lines into the @F array. Defaults to splitting on whitespace

  • -e execute the perl code

splice @F,0,1 cleanly removes column 0 from the @F array

join " ",@F joins the elements of the @F array, using a space in-between each element

Python solution:

python -c "import sys;[sys.stdout.write(' '.join(line.split()[1:]) + '\n') for line in sys.stdin]" < file

Opening a remote machine's Windows C drive

If it's not the Home edition of XP, you can use \\servername\c$

Mark Brackett's comment:

Note that you need to be an Administrator on the local machine, as the share permissions are locked down

Remove HTML tags from a String

Try this for javascript:

const strippedString = htmlString.replace(/(<([^>]+)>)/gi, "");

How to add a line break in an Android TextView?

This worked for me, maybe someone will find out this helpful:

TextView textField = (TextView) findViewById(;
textField.setText("First line of text" + System.getProperty("line.separator") + "Linija 2");

Installing NumPy via Anaconda in Windows

Anaconda folder basically resides in C:\Users\\Anaconda. Try setting the PATH to this folder.

Vue is not defined

jsBin demo

  1. You missed the order, first goes:

<script src=""></script>

and then:

    var demo = new Vue({
        el: '#demo',
        data: {
            message: 'Hello Vue.js!'
  1. And type="JavaScript" should be type="text/javascript" (or rather nothing at all)

Intellij JAVA_HOME variable

Bit counter-intuitive, but you must first setup a SDK for Java projects. On the bottom right of the IntelliJ welcome screen, select 'Configure > Project Defaults > Project Structure'.

The Project tab on the left will show that you have no SDK selected:

Therefore, you must click the 'New...' button on the right hand side of the dropdown and point it to your JDK. After that, you can go back to the import screen and it should be populated with your JAVA_HOME variable, providing you have this set.

Creating a node class in Java

Welcome to Java! This Nodes are like a blocks, they must be assembled to do amazing things! In this particular case, your nodes can represent a list, a linked list, You can see an example here:

public class ItemLinkedList {
    private ItemInfoNode head;
    private ItemInfoNode tail;
    private int size = 0;

    public int getSize() {
        return size;

    public void addBack(ItemInfo info) {
        if (head == null) {
            head = new ItemInfoNode(info, null, null);
            tail = head;
        } else {
            ItemInfoNode node = new ItemInfoNode(info, null, tail);
            this.tail = node;

    public void addFront(ItemInfo info) {
        if (head == null) {
            head = new ItemInfoNode(info, null, null);
            tail = head;
        } else {
            ItemInfoNode node = new ItemInfoNode(info, head, null);
            this.head.prev = node;
            this.head = node;

    public ItemInfo removeBack() {
        ItemInfo result = null;
        if (head != null) {
            result =;
            if (tail.prev != null) {
       = null;
                tail = tail.prev;
            } else {
                head = null;
                tail = null;
        return result;

    public ItemInfo removeFront() {
        ItemInfo result = null;
        if (head != null) {
            result =;
            if ( != null) {
       = null;
                head =;
            } else {
                head = null;
                tail = null;
        return result;

    public class ItemInfoNode {

        private ItemInfoNode next;
        private ItemInfoNode prev;
        private ItemInfo info;

        public ItemInfoNode(ItemInfo info, ItemInfoNode next, ItemInfoNode prev) {
   = info;
   = next;
            this.prev = prev;

        public void setInfo(ItemInfo info) {
   = info;

        public void setNext(ItemInfoNode node) {
            next = node;

        public void setPrev(ItemInfoNode node) {
            prev = node;

        public ItemInfo getInfo() {
            return info;

        public ItemInfoNode getNext() {
            return next;

        public ItemInfoNode getPrev() {
            return prev;


Declare ItemInfo as this:

public class ItemInfo {
    private String name;
    private String rfdNumber;
    private double price;
    private String originalPosition;

    public ItemInfo(){

    public ItemInfo(String name, String rfdNumber, double price, String originalPosition) { = name;
        this.rfdNumber = rfdNumber;
        this.price = price;
        this.originalPosition = originalPosition;

    public String getName() {
        return name;

    public void setName(String name) { = name;

    public String getRfdNumber() {
        return rfdNumber;

    public void setRfdNumber(String rfdNumber) {
        this.rfdNumber = rfdNumber;

    public double getPrice() {
        return price;

    public void setPrice(double price) {
        this.price = price;

    public String getOriginalPosition() {
        return originalPosition;

    public void setOriginalPosition(String originalPosition) {
        this.originalPosition = originalPosition;

Then, You can use your nodes inside the linked list like this:

public static void main(String[] args) {
    ItemLinkedList list = new ItemLinkedList();
    for (int i = 1; i <= 10; i++) {
        list.addBack(new ItemInfo("name-"+i, "rfd"+i, i, String.valueOf(i)));

    while (list.size() > 0){

CSS Input field text color of inputted text


input, select, textarea{
    color: #000;


input, select, textarea{
    color: #f00;

or color: #ff0000;

How to prevent scientific notation in R?

To set the use of scientific notation in your entire R session, you can use the scipen option. From the documentation (?options):

‘scipen’: integer.  A penalty to be applied when deciding to print
          numeric values in fixed or exponential notation.  Positive
          values bias towards fixed and negative towards scientific
          notation: fixed notation will be preferred unless it is more
          than ‘scipen’ digits wider.

So in essence this value determines how likely it is that scientific notation will be triggered. So to prevent scientific notation, simply use a large positive value like 999:


What does the CSS rule "clear: both" do?

CSS float and clear

Sample Fiddle

Just try to remove clear:both property from the div with class sample and see how it follows floating divs.

Output in a table format in Java's System.out

Check this out. The author provides a simple but elegant solution which doesn't require any 3rd party library.

An example of the TableBuilder and sample output

What does the "map" method do in Ruby?

Using ruby 2.4 you can do the same thing using transform_values, this feature extracted from rails to ruby.

h = {a: 1, b: 2, c: 3}

h.transform_values { |v| v * 10 }
 #=> {a: 10, b: 20, c: 30}

How do I execute .js files locally in my browser?

Around 1:51 in the video, notice how she puts a <script> tag in there? The way it works is like this:

Create an html file (that's just a text file with a .html ending) somewhere on your computer. In the same folder that you put index.html, put a javascript file (that's just a textfile with a .js ending - let's call it game.js). Then, in your index.html file, put some html that includes the script tag with game.js, like Mary did in the video. index.html should look something like this:

        <script src="game.js"></script>

Now, double click on that file in finder, and it should open it up in your browser. To open up the console to see the output of your javascript code, hit Command-alt-j (those three buttons at the same time).

Good luck on your journey, hope it's as fun for you as it has been for me so far :)

select and echo a single field from mysql db using PHP

Read the manual, it covers it very well:

Usually you do something like this:

while ($row = mysql_fetch_assoc($result)) {
  echo $row['firstname'];
  echo $row['lastname'];
  echo $row['address'];
  echo $row['age'];

How is a tag different from a branch in Git? Which should I use, here?

The Git Parable explains how a typical DVCS gets created and why their creators did what they did. Also, you might want to take a look at Git for Computer Scientist; it explains what each type of object in Git does, including branches and tags.

How can I find a specific file from a Linux terminal?

Find from root path find / -name "index.html"

Find from current path find . -name "index.html"

how to delete all commit history in github?

If you are sure you want to remove all commit history, simply delete the .git directory in your project root (note that it's hidden). Then initialize a new repository in the same folder and link it to the GitHub repository:

git init
git remote add origin [email protected]:user/repo

now commit your current version of code

git add *
git commit -am 'message'

and finally force the update to GitHub:

git push -f origin master

However, I suggest backing up the history (the .git folder in the repository) before taking these steps!

Storing C++ template function definitions in a .CPP file

For others on this page wondering what the correct syntax is (as did I) for explicit template specialisation (or at least in VS2008), its the following...

In your .h file...

template<typename T>
class foo
    void bar(const T &t);

And in your .cpp file

template <class T>
void foo<T>::bar(const T &t)
{ }

// Explicit template instantiation
template class foo<int>;

VBA: Counting rows in a table (list object)

You can use:

Sub returnname(ByVal TableName As String)

MsgBox (Range("Table15").Rows.count)

End Sub

and call the function as below

Sub called()

returnname "Table15"

End Sub

Python: How to check if keys exists and retrieve value from Dictionary in descending priority

If we encapsulate that in a function we could use recursion and state clearly the purpose by naming the function properly (not sure if getAny is actually a good name):

def getAny(dic, keys, default=None):
    return (keys or default) and dic.get(keys[0], 
                                         getAny( dic, keys[1:], default=default))

or even better, without recursion and more clear:

def getAny(dic, keys, default=None):
    for k in keys: 
        if k in dic:
           return dic[k]
    return default

Then that could be used in a way similar to the dict.get method, like:

getAny(myDict, keySet)

and even have a default result in case of no keys found at all:

getAny(myDict, keySet, "not found")

The property 'value' does not exist on value of type 'HTMLElement'

If you are using react you can use the as operator.

let inputValue = (document.getElementById(elementId) as HTMLInputElement).value;

How to read pickle file?

The following is an example of how you might write and read a pickle file. Note that if you keep appending pickle data to the file, you will need to continue reading from the file until you find what you want or an exception is generated by reaching the end of the file. That is what the last function does.

import os
import pickle

PICKLE_FILE = 'pickle.dat'

def main():
    # append data to the pickle file
    add_to_pickle(PICKLE_FILE, 123)
    add_to_pickle(PICKLE_FILE, 'Hello')
    add_to_pickle(PICKLE_FILE, None)
    add_to_pickle(PICKLE_FILE, b'World')
    add_to_pickle(PICKLE_FILE, 456.789)
    # load & show all stored objects
    for item in read_from_pickle(PICKLE_FILE):

def add_to_pickle(path, item):
    with open(path, 'ab') as file:
        pickle.dump(item, file, pickle.HIGHEST_PROTOCOL)

def read_from_pickle(path):
    with open(path, 'rb') as file:
            while True:
                yield pickle.load(file)
        except EOFError:

if __name__ == '__main__':

Visual Studio 2017 - Git failed with a fatal error

I'm using GitKraken and Visual Studio 2017.

When GitKraken clones a repository, it leaves fetch address like "[email protected]:user/Repo.git", instead of "".

To fix that, go to Team Explorer ? Settings ? Repository Settings ? Remotes ? Edit, and change "git@" to "https://" and ":" to "/".

Visual Studio C# IntelliSense not automatically displaying

I hit this today after the following sequence:

  1. Added a new class to my project.
  2. Closed Visual Studio, but accidentally selected No when it asked if I wanted to save changes.
  3. Reopened Visual Studio, and found that it reopened the new file automatically but without my previous changes (as expected). However, IntelliSense was no longer working in the new file.

The problem was in addition to not saving changes to the new file, it didn't save changes to the project, so after reopening Visual Studio the file was not part of the project. The Show All Files command in Solution Explorer, or Add → Existing Item..., resolved the problem.

How do I get the browser scroll position in jQuery?

It's better to use $(window).scroll() rather than $('#Eframe').on("mousewheel")

$('#Eframe').on("mousewheel") will not trigger if people manually scroll using up and down arrows on the scroll bar or grabbing and dragging the scroll bar itself.

    var scrollPos = $(document).scrollTop();

If #Eframe is an element with overflow:scroll on it and you want it's scroll position. I think this should work (I haven't tested it though).

    var scrollPos = $('#Eframe').scrollTop();

hibernate could not get next sequence value

I seem to recall having to use @GeneratedValue(strategy = GenerationType.IDENTITY) to get Hibernate to use 'serial' columns on PostgreSQL.

What does the "undefined reference to varName" in C mean?

An initial reaction to this would be to ask and ensure that the two object files are being linked together. This is done at the compile stage by compiling both files at the same time:

gcc -o programName a.c b.c

Or if you want to compile separately, it would be:

gcc -c a.c
gcc -c b.c
gcc -o programName a.o b.o

Why is there no multiple inheritance in Java, but implementing multiple interfaces is allowed?

For the same reason C# doesn't allow multiple inheritence but allows you to implement multiple interfaces.

The lesson learned from C++ w/ multiple inheritence was that it lead to more issues than it was worth.

An interface is a contract of things your class has to implement. You don't gain any functionality from the interface. Inheritence allows you to inherit the functionality of a parent class (and in multiple-inheritence, that can get extremely confusing).

Allowing multiple interfaces allows you to use Design Patterns (like Adapter) to solve the same types of issues you can solve using multiple inheritence, but in a much more reliable and predictable manner.

Using column alias in WHERE clause of MySQL query produces an error

Maybe my answer is too late but this can help others.

You can enclose it with another select statement and use where clause to it.

SELECT * FROM (Select col1, col2,...) as t WHERE t.calcAlias > 0

calcAlias is the alias column that was calculated.

What does if __name__ == "__main__": do?

The reason for

if __name__ == "__main__":

is primarily to avoid the import lock problems that would arise from having code directly imported. You want main() to run if your file was directly invoked (that's the __name__ == "__main__" case), but if your code was imported then the importer has to enter your code from the true main module to avoid import lock problems.

A side-effect is that you automatically sign on to a methodology that supports multiple entry points. You can run your program using main() as the entry point, but you don't have to. While expects main(), other tools use alternate entry points. For example, to run your file as a gunicorn process, you define an app() function instead of a main(). Just as with, gunicorn imports your code so you don't want it do do anything while it's being imported (because of the import lock issue).

MySQL ON DUPLICATE KEY UPDATE for multiple rows insert in single query

I was looking for the same behavior using jdbi's BindBeanList and found the syntax is exactly the same as Peter Lang's answer above. In case anybody is running into this question, here's my code:

  @SqlUpdate("INSERT INTO table_one (col_one, col_two) VALUES <beans> ON DUPLICATE KEY UPDATE col_one=VALUES(col_one), col_two=VALUES(col_two)")
void insertBeans(@BindBeanList(value = "beans", propertyNames = {"colOne", "colTwo"}) List<Beans> beans);

One key detail to note is that the propertyName you specify within @BindBeanList annotation is not same as the column name you pass into the VALUES() call on update.

How do I assert an Iterable contains elements with a certain property?


                          hasItem(hasProperty("YourProperty", is("YourValue"))));

How to use __DATE__ and __TIME__ predefined macros in as two integers, then stringify?

If you can use a C++ compiler to build the object file that you want to contain your version string, then we can do exactly what you want! The only magic here is that C++ allows you to use expressions to statically initialize an array, while C doesn't. The expressions need to be fully computable at compile time, but these expressions are, so it's no problem.

We build up the version string one byte at a time, and get exactly what we want.

// source file version_num.h




#endif // VERSION_NUM_H

// source file build_defs.h

#ifndef BUILD_DEFS_H

#define BUILD_DEFS_H

// Example of __DATE__ string: "Jul 27 2012"
//                              01234567890

#define BUILD_YEAR_CH0 (__DATE__[ 7])
#define BUILD_YEAR_CH1 (__DATE__[ 8])
#define BUILD_YEAR_CH2 (__DATE__[ 9])
#define BUILD_YEAR_CH3 (__DATE__[10])

#define BUILD_MONTH_IS_JAN (__DATE__[0] == 'J' && __DATE__[1] == 'a' && __DATE__[2] == 'n')
#define BUILD_MONTH_IS_FEB (__DATE__[0] == 'F')
#define BUILD_MONTH_IS_MAR (__DATE__[0] == 'M' && __DATE__[1] == 'a' && __DATE__[2] == 'r')
#define BUILD_MONTH_IS_APR (__DATE__[0] == 'A' && __DATE__[1] == 'p')
#define BUILD_MONTH_IS_MAY (__DATE__[0] == 'M' && __DATE__[1] == 'a' && __DATE__[2] == 'y')
#define BUILD_MONTH_IS_JUN (__DATE__[0] == 'J' && __DATE__[1] == 'u' && __DATE__[2] == 'n')
#define BUILD_MONTH_IS_JUL (__DATE__[0] == 'J' && __DATE__[1] == 'u' && __DATE__[2] == 'l')
#define BUILD_MONTH_IS_AUG (__DATE__[0] == 'A' && __DATE__[1] == 'u')
#define BUILD_MONTH_IS_SEP (__DATE__[0] == 'S')
#define BUILD_MONTH_IS_OCT (__DATE__[0] == 'O')
#define BUILD_MONTH_IS_NOV (__DATE__[0] == 'N')
#define BUILD_MONTH_IS_DEC (__DATE__[0] == 'D')

#define BUILD_MONTH_CH0 \

#define BUILD_MONTH_CH1 \
    ( \
        (BUILD_MONTH_IS_JAN) ? '1' : \
        (BUILD_MONTH_IS_FEB) ? '2' : \
        (BUILD_MONTH_IS_MAR) ? '3' : \
        (BUILD_MONTH_IS_APR) ? '4' : \
        (BUILD_MONTH_IS_MAY) ? '5' : \
        (BUILD_MONTH_IS_JUN) ? '6' : \
        (BUILD_MONTH_IS_JUL) ? '7' : \
        (BUILD_MONTH_IS_AUG) ? '8' : \
        (BUILD_MONTH_IS_SEP) ? '9' : \
        (BUILD_MONTH_IS_OCT) ? '0' : \
        (BUILD_MONTH_IS_NOV) ? '1' : \
        (BUILD_MONTH_IS_DEC) ? '2' : \
        /* error default */    '?' \

#define BUILD_DAY_CH0 ((__DATE__[4] >= '0') ? (__DATE__[4]) : '0')
#define BUILD_DAY_CH1 (__DATE__[ 5])

// Example of __TIME__ string: "21:06:19"
//                              01234567

#define BUILD_HOUR_CH0 (__TIME__[0])
#define BUILD_HOUR_CH1 (__TIME__[1])

#define BUILD_MIN_CH0 (__TIME__[3])
#define BUILD_MIN_CH1 (__TIME__[4])

#define BUILD_SEC_CH0 (__TIME__[6])
#define BUILD_SEC_CH1 (__TIME__[7])


    ((VERSION_MAJOR / 100) + '0'), \
    (((VERSION_MAJOR % 100) / 10) + '0'), \
    ((VERSION_MAJOR % 10) + '0')

#elif VERSION_MAJOR > 10

    ((VERSION_MAJOR / 10) + '0'), \
    ((VERSION_MAJOR % 10) + '0')


    (VERSION_MAJOR + '0')



    ((VERSION_MINOR / 100) + '0'), \
    (((VERSION_MINOR % 100) / 10) + '0'), \
    ((VERSION_MINOR % 10) + '0')

#elif VERSION_MINOR > 10

    ((VERSION_MINOR / 10) + '0'), \
    ((VERSION_MINOR % 10) + '0')


    (VERSION_MINOR + '0')


#endif // BUILD_DEFS_H

// source file main.c

#include "version_num.h"
#include "build_defs.h"

// want something like: 1.4.1432.2234

const unsigned char completeVersion[] =
    '-', 'V', '-',

#include <stdio.h>

int main(int argc, char **argv)
    printf("%s\n", completeVersion);
    // prints something similar to: 1.4-V-2013-05-09T15:34:49

This isn't exactly the format you asked for, but I still don't fully understand how you want days and hours mapped to an integer. I think it's pretty clear how to make this produce any desired string.

How do I set a conditional breakpoint in gdb, when char* x points to a string whose value equals "hello"?

You can use strcmp:

break x:20 if strcmp(y, "hello") == 0

20 is line number, x can be any filename and y can be any variable.

To show error message without alert box in Java Script

web masters or web programmers, please insert

<!DOCTYPE html>

at the start of your page. Second you should enclose your attributes with quotes like

type="text" id="fname"

input element should not contain end element, just close it like:


input element dont have innerHTML, it has value sor your javascript line should be:

document.getElementById("fname").value = "this is invalid name";

Please write in organized way and make sure it is convenient to standards.

how to set the background image fit to browser using html

add this css in your stylesheet

        background:url(Desert.jpg) no-repeat center center fixed;
        background-size: cover;
        -webkit-background-size: cover;
        -moz-background-size: cover;
        -o-background-size: cover;
        margin: 0;
        padding: 0;


Colors in JavaScript console

// log in color 
// consolelog({"color":"red","background-color":"blue"},1,2,3)

// consolelog({"color":"red"},1,2,3)
// consolelog(1,2,3)
function consolelog()
    var vars=(,1)||[""])
    var message=vars.join(" ")
    var colors = 
                    "background-color"  :"yellow",
                    "color"             :"red"
                    "background-color"  :"red",
                    "color"             :"yellow"
                    "background-color"  :"yellow",
                    "color"             :"black"
            success : "green", 
            info    : "dodgerblue"  

    var givenstyle=style[0];
    var colortouse= colors[givenstyle] || givenstyle;
    if(typeof colortouse=="object")
        colortouse= printobject(colortouse)
    function printobject(o){
        var str='';

        for(var p in o){
            if(typeof o[p] == 'string'){
                str+= p + ': ' + o[p]+'; \n';
            str+= p + ': { \n' + print(o[p]) + '}';

        return str;
        console.log("%c" + message, colortouse);

Cannot use string offset as an array in php

The error occurs when:

$a = array(); 
$a['text1'] = array();
$a['text1']['text2'] = 'sometext';


echo $a['text1']['text2'];     //Error!!


$b = $a['text1'];
echo $b['text2'];    // prints: sometext


Electron: jQuery is not defined

Just came across this same problem

npm install jquery --save

<script>window.$ = window.jQuery = require('jquery');</script>

worked for me

Subprocess changing directory

To run your_command as a subprocess in a different directory, pass cwd parameter, as suggested in @wim's answer:

import subprocess

subprocess.check_call(['your_command', 'arg 1', 'arg 2'], cwd=working_dir)

A child process can't change its parent's working directory (normally). Running cd .. in a child shell process using subprocess won't change your parent Python script's working directory i.e., the code example in @glglgl's answer is wrong. cd is a shell builtin (not a separate executable), it can change the directory only in the same process.


The syntax:

   ALTER TABLE `table1` CHANGE `itemId` `itemId` INT( 11 ) NOT NULL AUTO_INCREMENT 

But the table needs a defined key (ex primary key on itemId).

what does numpy ndarray shape do?

array([[1, 2, 3],
[4, 5, 6],
[7, 8, 9]])

enter image description here

Pushing empty commits to remote

You won't face any terrible consequence, just the history will look kind of confusing.

You could change the commit message by doing

git commit --amend
git push --force-with-lease # (as opposed to --force, it doesn't overwrite others' work)

BUT this will override the remote history with yours, meaning that if anybody pulled that repo in the meanwhile, this person is going to be very mad at you...

Just do it if you are the only person accessing the repo.

How do I catch an Ajax query post error?

You have to log the responseText:

    type: 'POST',
    url: 'status.ajax.php',
    data: {
    deviceId: id
 function (data) {
  //your code
.fail(function (data) {
      console.log( "Ajax failed: " + data['responseText'] );

What is http multipart request?

A HTTP multipart request is a HTTP request that HTTP clients construct to send files and data over to a HTTP Server. It is commonly used by browsers and HTTP clients to upload files to the server.

java.lang.NoClassDefFoundError:failed resolution of :Lorg/apache/http/ProtocolVersion

This link android-9.0-changes-28-->Apache HTTP client deprecation explains reason for adding the following to your AndroidManifest.xml:

<uses-library android:name="org.apache.http.legacy" android:required="false"/>

With Android 6.0, we removed support for the Apache HTTP client. Beginning with Android 9, that library is removed from the bootclasspath and is not available to apps by default.

How can I retrieve Id of inserted entity using Entity framework?

There are two strategies:

  1. Use Database-generated ID (int or GUID)


    You should perform SaveChanges() to get the ID for just saved entities.


    Can use int identity.

  2. Use client generated ID - GUID only.

    Pros: Minification of SaveChanges operations. Able to insert a big graph of new objects per one operation.


    Allowed only for GUID

How do I execute a file in Cygwin?

Thomas wrote:

Apparently, gcc doesn't behave like the one described in The C Programming language

It does in general. For your program to run on Windows it needs to end in .exe, "the C Programming language" was not written with Windows programmers in mind. As you've seen, cygwin emulates many, but not all, features of a POSIX environment.

Dynamically access object property using variable

I came across a case where I thought I wanted to pass the "address" of an object property as data to another function and populate the object (with AJAX), do lookup from address array, and display in that other function. I couldn't use dot notation without doing string acrobatics so I thought an array might be nice to pass instead. I ended-up doing something different anyway, but seemed related to this post.

Here's a sample of a language file object like the one I wanted data from:

const locs = {
  "audioPlayer": {
    "controls": {
      "start": "start",
      "stop": "stop"
    "heading": "Use controls to start and stop audio."

I wanted to be able to pass an array such as: ["audioPlayer", "controls", "stop"] to access the language text, "stop" in this case.

I created this little function that looks-up the "least specific" (first) address parameter, and reassigns the returned object to itself. Then it is ready to look-up the next-most-specific address parameter if one exists.

function getText(selectionArray, obj) {
  selectionArray.forEach(key => {
    obj = obj[key];
  return obj;


/* returns 'stop' */
console.log(getText(["audioPlayer", "controls", "stop"], locs)); 

/* returns 'use controls to start and stop audio.' */
console.log(getText(["audioPlayer", "heading"], locs)); 

What can cause intermittent ORA-12519 (TNS: no appropriate handler found) errors

I also had the same problem, I searched for the answers many places. I got many similar answers to change the number of process/service handlers. But I thought, what if I forgot to reset it back?

Then I tried using Thread.sleep() method after each of my connection.close();.

I don't know how, but it's working at least for me.

If any one wants to try it out and figure out how it's working then please go ahead. I would also like to know it as I am a beginner in programming world.

Compare dates in MySQL

this is what it worked for me:

select * from table
where column
BETWEEN STR_TO_DATE('29/01/15', '%d/%m/%Y')
 AND STR_TO_DATE('07/10/15', '%d/%m/%Y')

Please, note that I had to change STR_TO_DATE(column, '%d/%m/%Y') from previous solutions, as it was taking ages to load

Display all post meta keys and meta values of the same post ID in wordpress

WordPress have the function get_metadata this get all meta of object (Post, term, user...)

Just use

get_metadata( 'post', 15 );

Using Java with Microsoft Visual Studio 2012

IntegraStudio enables syntax coloring, building, debugging and finding definition and references (F12 and ALT-F12) for Java projects in Visual Studio.

JTable - Selected Row click event

Here's how I did it:

table.getSelectionModel().addListSelectionListener(new ListSelectionListener(){
        public void valueChanged(ListSelectionEvent event) {
            // do some actions here, for example
            // print first column value from selected row
            System.out.println(table.getValueAt(table.getSelectedRow(), 0).toString());

This code reacts on mouse click and item selection from keyboard.

jQuery UI Dialog Box - does not open after being closed

I solved it.

I used destroy instead close function (it doesn't make any sense), but it worked.

$(document).ready(function() {
    $('#terms').dialog({resizable: false,
        modal: true,
        width: 400,
        height: 450,
        overlay: { backgroundColor: "#000", opacity: 0.5 },
        buttons:{ "Close": function() { $(this).dialog('**destroy**'); } },
        close: function(ev, ui) { $(this).close(); },
$('#form1 input#calendarTEST').datepicker({ dateFormat: 'MM d, yy' });

Should I use <i> tag for icons instead of <span>?

Quentin's answer clearly states that i tag should not be used to define icons.

But, Holly suggested that span has no meaning in itself and voted in favor of i instead of span tag.

Few suggested to use img as it's semantic and contains alt tag. But, we should not also use img because even empty src sends a request to server. Read here

I think, the correct way would be,

<span class="icon-fb" role="img" aria-label="facebook"></span>

This solves the issue of no alt tag in span and makes it accessible to vision-impaired users. It's semantic and not misusing ( hacking ) any tag.

Visual Studio Code always asking for git credentials

Use an SSH key without a passphrase.

Maybe this is obvious to some (wasn't to me). It also doesn't solve the issue if you absolutely require a passphrase, but this was a decent compromise in my situation on Mac.

How add spaces between Slick carousel item

@Dishan TD's answer works nice, but I'm getting better results using only margin-left.

And to make this clearer to everyone else, you have to pay attention to the both opposite numbers: 27 and -27

  /* the slides */
  .slick-slide {

  /* the parent */
  .slick-list {

Peak signal detection in realtime timeseries data

Following on from @Jean-Paul's proposed solution, I have implemented his algorithm in C#

public class ZScoreOutput
    public List<double> input;
    public List<int> signals;
    public List<double> avgFilter;
    public List<double> filtered_stddev;

public static class ZScore
    public static ZScoreOutput StartAlgo(List<double> input, int lag, double threshold, double influence)
        // init variables!
        int[] signals = new int[input.Count];
        double[] filteredY = new List<double>(input).ToArray();
        double[] avgFilter = new double[input.Count];
        double[] stdFilter = new double[input.Count];

        var initialWindow = new List<double>(filteredY).Skip(0).Take(lag).ToList();

        avgFilter[lag - 1] = Mean(initialWindow);
        stdFilter[lag - 1] = StdDev(initialWindow);

        for (int i = lag; i < input.Count; i++)
            if (Math.Abs(input[i] - avgFilter[i - 1]) > threshold * stdFilter[i - 1])
                signals[i] = (input[i] > avgFilter[i - 1]) ? 1 : -1;
                filteredY[i] = influence * input[i] + (1 - influence) * filteredY[i - 1];
                signals[i] = 0;
                filteredY[i] = input[i];

            // Update rolling average and deviation
            var slidingWindow = new List<double>(filteredY).Skip(i - lag).Take(lag+1).ToList();

            var tmpMean = Mean(slidingWindow);
            var tmpStdDev = StdDev(slidingWindow);

            avgFilter[i] = Mean(slidingWindow);
            stdFilter[i] = StdDev(slidingWindow);

        // Copy to convenience class 
        var result = new ZScoreOutput();
        result.input = input;
        result.avgFilter       = new List<double>(avgFilter);
        result.signals         = new List<int>(signals);
        result.filtered_stddev = new List<double>(stdFilter);

        return result;

    private static double Mean(List<double> list)
        // Simple helper function! 
        return list.Average();

    private static double StdDev(List<double> values)
        double ret = 0;
        if (values.Count() > 0)
            double avg = values.Average();
            double sum = values.Sum(d => Math.Pow(d - avg, 2));
            ret = Math.Sqrt((sum) / (values.Count() - 1));
        return ret;

Example usage:

var input = new List<double> {1.0, 1.0, 1.1, 1.0, 0.9, 1.0, 1.0, 1.1, 1.0, 0.9, 1.0,
    1.1, 1.0, 1.0, 0.9, 1.0, 1.0, 1.1, 1.0, 1.0, 1.0, 1.0, 1.1, 0.9, 1.0, 1.1, 1.0, 1.0, 0.9,
    1.0, 1.1, 1.0, 1.0, 1.1, 1.0, 0.8, 0.9, 1.0, 1.2, 0.9, 1.0, 1.0, 1.1, 1.2, 1.0, 1.5, 1.0,
    3.0, 2.0, 5.0, 3.0, 2.0, 1.0, 1.0, 1.0, 0.9, 1.0, 1.0, 3.0, 2.6, 4.0, 3.0, 3.2, 2.0, 1.0,
    1.0, 0.8, 4.0, 4.0, 2.0, 2.5, 1.0, 1.0, 1.0};

int lag = 30;
double threshold = 5.0;
double influence = 0.0;

var output = ZScore.StartAlgo(input, lag, threshold, influence);

How do I install ASP.NET MVC 5 in Visual Studio 2012?

Step 1: Install update

OK, so that gets you to be able to start from a blank ASP.NET MVC project, but a lot of people want the FULL INTERNET APPLICATION as shipped with Visual Studio 2013.

So I have a step 2:

If you follow that tutorial on my website I follow it up with a full install of Foundation 5 and a cool Hybrid OffCanvas/Top-Bar navigation.

TypeError: a bytes-like object is required, not 'str' in python and CSV

You are using Python 2 methodology instead of Python 3.





and you will get a file with the following output:

1,Andhra Pradesh,13,49378776
2,Arunachal Pradesh,16,1382611

In Python 3 csv takes the input in text mode, whereas in Python 2 it took it in binary mode.

Edited to Add

Here is the code I ran:

html = urllib.request.urlopen(url).read()
soup = BeautifulSoup(html)
table=soup.find('table', attrs={'class':'tableizer-table'})
for row in table.findAll('tr')[1:]:
    for cell in row.findAll('td'):
outfile = open('./immates.csv','w')
writer.writerow(['SNo', 'States', 'Dist', 'Population'])

Logging in Scala

Using slf4j and a wrapper is nice but the use of it's built in interpolation breaks down when you have more than two values to interpolate, since then you need to create an Array of values to interpolate.

A more Scala like solution is to use a thunk or cluster to delay the concatenation of the error message. A good example of this is Lift's logger

Log.scala Slf4jLog.scala

Which looks like this:

class Log4JLogger(val logger: Logger) extends LiftLogger {
  override def trace(msg: => AnyRef) = if (isTraceEnabled) logger.trace(msg)

Note that msg is a call-by-name and won't be evaluated unless isTraceEnabled is true so there's no cost in generating a nice message string. This works around the slf4j's interpolation mechanism which requires parsing the error message. With this model, you can interpolate any number of values into the error message.

If you have a separate trait that mixes this Log4JLogger into your class, then you can do

trace("The foobar from " + a + " doesn't match the foobar from " +
      b + " and you should reset the baz from " + c")

instead of

info("The foobar from {0} doesn't match the foobar from {1} and you should reset the baz from {c},
     Array(a, b, c))

The APR based Apache Tomcat Native library was not found on the java.library.path

not found on the java.library.path: /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib

The native lib is expected in one of the following locations


and not in


The files in tomcat/lib are all jar file and are added by tomcat to the classpath so that they are available to your application.

The native lib is needed by tomcat to perform better on the platform it is installed on and thus cannot be a jar, for linux it could be a .so file, for windows it could be a .dll file.

Just download the native library for your platform and place it in the one of the locations tomcat is expecting it to be.

Note that you are not required to have this lib for development/test purposes. Tomcat runs just fine without it.

org.apache.catalina.startup.Catalina start INFO: Server startup in 2882 ms


The output you are getting is very normal, it's just some logging outputs from tomcat, the line right above indicates that the server correctly started and is ready for operating.

If you are troubling with running your servlet then after the run on sever command eclipse opens a browser window (embeded (default) or external, depends on your config). If nothing shows on the browser, then check the url bar of the browser to see whether your servlet was requested or not.

It should be something like that



Try to call your servlet using the following url


Also each web project has a web.xml, you can find it in your project under WebContent\WEB-INF.

It is better to configure your servlets there using servlet-name servlet-class and url-mapping. It could look like that:

    <display-name>File counter - My first servlet</display-name>


In eclipse dynamic web project the default context name is the same as your project name.


will work too.

invalid target release: 1.7

This probably works for a lot of things but it's not enough for Maven and certainly not for the maven compiler plugin.

Check Mike's answer to his own question here: stackoverflow question 24705877

This solved the issue for me both command line AND within eclipse.

Also, @LinGao answer to stackoverflow question 2503658 and the use of the $JAVACMD variable might help but I haven't tested it myself.

Pod install is staying on "Setting up CocoaPods Master repo"

You will have to remove the repo and re-setup it...

pod repo remove master
pod setup

Wait one second in running program

Wait function using timers, no UI locks.

public void wait(int milliseconds)
    var timer1 = new System.Windows.Forms.Timer();
    if (milliseconds == 0 || milliseconds < 0) return;

    // Console.WriteLine("start wait timer");
    timer1.Interval = milliseconds;
    timer1.Enabled  = true;

    timer1.Tick += (s, e) =>
        timer1.Enabled = false;
        // Console.WriteLine("stop wait timer");

    while (timer1.Enabled)

Usage: just placing this inside your code that needs to wait:

wait(1000); //wait one second

Adding attributes to an XML node

You can use the Class XmlAttribute.


XmlAttribute attr = xmlDoc.CreateAttribute("userName");
attr.Value = "Tushar";


What is the difference between the kernel space and the user space?

CPU rings are the most clear distinction

In x86 protected mode, the CPU is always in one of 4 rings. The Linux kernel only uses 0 and 3:

  • 0 for kernel
  • 3 for users

This is the most hard and fast definition of kernel vs userland.

Why Linux does not use rings 1 and 2: CPU Privilege Rings: Why rings 1 and 2 aren't used?

How is the current ring determined?

The current ring is selected by a combination of:

  • global descriptor table: a in-memory table of GDT entries, and each entry has a field Privl which encodes the ring.

    The LGDT instruction sets the address to the current descriptor table.

    See also:

  • the segment registers CS, DS, etc., which point to the index of an entry in the GDT.

    For example, CS = 0 means the first entry of the GDT is currently active for the executing code.

What can each ring do?

The CPU chip is physically built so that:

  • ring 0 can do anything

  • ring 3 cannot run several instructions and write to several registers, most notably:

    • cannot change its own ring! Otherwise, it could set itself to ring 0 and rings would be useless.

      In other words, cannot modify the current segment descriptor, which determines the current ring.

    • cannot modify the page tables: How does x86 paging work?

      In other words, cannot modify the CR3 register, and paging itself prevents modification of the page tables.

      This prevents one process from seeing the memory of other processes for security / ease of programming reasons.

    • cannot register interrupt handlers. Those are configured by writing to memory locations, which is also prevented by paging.

      Handlers run in ring 0, and would break the security model.

      In other words, cannot use the LGDT and LIDT instructions.

    • cannot do IO instructions like in and out, and thus have arbitrary hardware accesses.

      Otherwise, for example, file permissions would be useless if any program could directly read from disk.

      More precisely thanks to Michael Petch: it is actually possible for the OS to allow IO instructions on ring 3, this is actually controlled by the Task state segment.

      What is not possible is for ring 3 to give itself permission to do so if it didn't have it in the first place.

      Linux always disallows it. See also: Why doesn't Linux use the hardware context switch via the TSS?

How do programs and operating systems transition between rings?

  • when the CPU is turned on, it starts running the initial program in ring 0 (well kind of, but it is a good approximation). You can think this initial program as being the kernel (but it is normally a bootloader that then calls the kernel still in ring 0).

  • when a userland process wants the kernel to do something for it like write to a file, it uses an instruction that generates an interrupt such as int 0x80 or syscall to signal the kernel. x86-64 Linux syscall hello world example:

        .ascii "hello world\n"
        hello_world_len = . - hello_world
    .global _start
        /* write */
        mov $1, %rax
        mov $1, %rdi
        mov $hello_world, %rsi
        mov $hello_world_len, %rdx
        /* exit */
        mov $60, %rax
        mov $0, %rdi

    compile and run:

    as -o hello_world.o hello_world.S
    ld -o hello_world.out hello_world.o

    GitHub upstream.

    When this happens, the CPU calls an interrupt callback handler which the kernel registered at boot time. Here is a concrete baremetal example that registers a handler and uses it.

    This handler runs in ring 0, which decides if the kernel will allow this action, do the action, and restart the userland program in ring 3. x86_64

  • when the exec system call is used (or when the kernel will start /init), the kernel prepares the registers and memory of the new userland process, then it jumps to the entry point and switches the CPU to ring 3

  • If the program tries to do something naughty like write to a forbidden register or memory address (because of paging), the CPU also calls some kernel callback handler in ring 0.

    But since the userland was naughty, the kernel might kill the process this time, or give it a warning with a signal.

  • When the kernel boots, it setups a hardware clock with some fixed frequency, which generates interrupts periodically.

    This hardware clock generates interrupts that run ring 0, and allow it to schedule which userland processes to wake up.

    This way, scheduling can happen even if the processes are not making any system calls.

What is the point of having multiple rings?

There are two major advantages of separating kernel and userland:

  • it is easier to make programs as you are more certain one won't interfere with the other. E.g., one userland process does not have to worry about overwriting the memory of another program because of paging, nor about putting hardware in an invalid state for another process.
  • it is more secure. E.g. file permissions and memory separation could prevent a hacking app from reading your bank data. This supposes, of course, that you trust the kernel.

How to play around with it?

I've created a bare metal setup that should be a good way to manipulate rings directly:

I didn't have the patience to make a userland example unfortunately, but I did go as far as paging setup, so userland should be feasible. I'd love to see a pull request.

Alternatively, Linux kernel modules run in ring 0, so you can use them to try out privileged operations, e.g. read the control registers: How to access the control registers cr0,cr2,cr3 from a program? Getting segmentation fault

Here is a convenient QEMU + Buildroot setup to try it out without killing your host.

The downside of kernel modules is that other kthreads are running and could interfere with your experiments. But in theory you can take over all interrupt handlers with your kernel module and own the system, that would be an interesting project actually.

Negative rings

While negative rings are not actually referenced in the Intel manual, there are actually CPU modes which have further capabilities than ring 0 itself, and so are a good fit for the "negative ring" name.

One example is the hypervisor mode used in virtualization.

For further details see:


In ARM, the rings are called Exception Levels instead, but the main ideas remain the same.

There exist 4 exception levels in ARMv8, commonly used as:

  • EL0: userland

  • EL1: kernel ("supervisor" in ARM terminology).

    Entered with the svc instruction (SuperVisor Call), previously known as swi before unified assembly, which is the instruction used to make Linux system calls. Hello world ARMv8 example:


    .global _start
        /* write */
        mov x0, 1
        ldr x1, =msg
        ldr x2, =len
        mov x8, 64
        svc 0
        /* exit */
        mov x0, 0
        mov x8, 93
        svc 0
        .ascii "hello syscall v8\n"
    len = . - msg

    GitHub upstream.

    Test it out with QEMU on Ubuntu 16.04:

    sudo apt-get install qemu-user gcc-arm-linux-gnueabihf
    arm-linux-gnueabihf-as -o hello.o hello.S
    arm-linux-gnueabihf-ld -o hello hello.o
    qemu-arm hello

    Here is a concrete baremetal example that registers an SVC handler and does an SVC call.

  • EL2: hypervisors, for example Xen.

    Entered with the hvc instruction (HyperVisor Call).

    A hypervisor is to an OS, what an OS is to userland.

    For example, Xen allows you to run multiple OSes such as Linux or Windows on the same system at the same time, and it isolates the OSes from one another for security and ease of debug, just like Linux does for userland programs.

    Hypervisors are a key part of today's cloud infrastructure: they allow multiple servers to run on a single hardware, keeping hardware usage always close to 100% and saving a lot of money.

    AWS for example used Xen until 2017 when its move to KVM made the news.

  • EL3: yet another level. TODO example.

    Entered with the smc instruction (Secure Mode Call)

The ARMv8 Architecture Reference Model DDI 0487C.a - Chapter D1 - The AArch64 System Level Programmer's Model - Figure D1-1 illustrates this beautifully:

enter image description here

The ARM situation changed a bit with the advent of ARMv8.1 Virtualization Host Extensions (VHE). This extension allows the kernel to run in EL2 efficiently:

enter image description here

VHE was created because in-Linux-kernel virtualization solutions such as KVM have gained ground over Xen (see e.g. AWS' move to KVM mentioned above), because most clients only need Linux VMs, and as you can imagine, being all in a single project, KVM is simpler and potentially more efficient than Xen. So now the host Linux kernel acts as the hypervisor in those cases.

Note how ARM, maybe due to the benefit of hindsight, has a better naming convention for the privilege levels than x86, without the need for negative levels: 0 being the lower and 3 highest. Higher levels tend to be created more often than lower ones.

The current EL can be queried with the MRS instruction: what is the current execution mode/exception level, etc?

ARM does not require all exception levels to be present to allow for implementations that don't need the feature to save chip area. ARMv8 "Exception levels" says:

An implementation might not include all of the Exception levels. All implementations must include EL0 and EL1. EL2 and EL3 are optional.

QEMU for example defaults to EL1, but EL2 and EL3 can be enabled with command line options: qemu-system-aarch64 entering el1 when emulating a53 power up

Code snippets tested on Ubuntu 18.10.

XMLHttpRequest blocked by CORS Policy

I believe sideshowbarker 's answer here has all the info you need to fix this. If your problem is just No 'Access-Control-Allow-Origin' header is present on the response you're getting, you can set up a CORS proxy to get around this. Way more info on it in the linked answer

Selecting a Linux I/O Scheduler

The Linux Kernel does not automatically change the IO Scheduler at run-time. By this I mean, the Linux kernel, as of today, is not able to automatically choose an "optimal" scheduler depending on the type of secondary storage devise. During start-up, or during run-time, it is possible to change the IO scheduler manually.

The default scheduler is chosen at start-up based on the contents in the file located at /linux-2.6 /block/Kconfig.iosched. However, it is possible to change the IO scheduler during run-time by echoing a valid scheduler name into the file located at /sys/block/[DEV]/queue/scheduler. For example, echo deadline > /sys/block/hda/queue/scheduler

How to split a large text file into smaller files with equal number of lines?

you can also use awk

awk -vc=1 'NR%200000==0{++c}{print $0 > c".txt"}' largefile

What is the difference between precision and scale?

precision: Its the total number of digits before or after the radix point. EX: 123.456 here precision is 6.

Scale: Its the total number of digits after the radix point. EX: 123.456 here Scaleis 3

Assigning multiple styles on an HTML element

You needed to do it like this:

<h2 style="text-align: center;font-family: Tahoma">TITLE</h2>

Hope it helped.

What are all the common ways to read a file in Ruby?

return last n lines from your_file.log or .txt

path = File.join(Rails.root, 'your_folder','your_file.log')

last_100_lines = `tail -n 100 #{path}`

Comparing two hashmaps for equal values and same key sets?

Compare every key in mapB against the counterpart in mapA. Then check if there is any key in mapA not existing in mapB

public boolean mapsAreEqual(Map<String, String> mapA, Map<String, String> mapB) {

        for (String k : mapB.keySet())
            if (!mapA.get(k).equals(mapB.get(k))) {
                return false;
        for (String y : mapA.keySet())
            if (!mapB.containsKey(y)) {
                return false;
    } catch (NullPointerException np) {
        return false;
    return true;

Detect if page has finished loading

there are two ways to do this in jquery depending what you are looking for..

using jquery you can do

  • //this will wait for the text assets to be loaded before calling this (the dom.. css.. js)

  • //this will wait for all the images and text assets to finish loading before executing


Add another class to a div

Well you just need to use document.getElementById('hello').setAttribute('class', 'someclass');.

Also innerHTML can lead to unexpected results! Consider the following;

var myParag = document.createElement('p');

if(under certain age)
    myParag.text="Good Bye";
    createCookie('age', 'not13', 0);
    return false;
    return true;


Convert a character digit to the corresponding integer in C

As per other replies, this is fine:

char c = '5';
int x = c - '0';

Also, for error checking, you may wish to check isdigit(c) is true first. Note that you cannot completely portably do the same for letters, for example:

char c = 'b';
int x = c - 'a'; // x is now not necessarily 1

The standard guarantees that the char values for the digits '0' to '9' are contiguous, but makes no guarantees for other characters like letters of the alphabet.

Memory address of an object in C#

Here's a simple way I came up with that doesn't involve unsafe code or pinning the object. Also works in reverse (object from address):

public static class AddressHelper
    private static object mutualObject;
    private static ObjectReinterpreter reinterpreter;

    static AddressHelper()
        AddressHelper.mutualObject = new object();
        AddressHelper.reinterpreter = new ObjectReinterpreter();
        AddressHelper.reinterpreter.AsObject = new ObjectWrapper();

    public static IntPtr GetAddress(object obj)
        lock (AddressHelper.mutualObject)
            AddressHelper.reinterpreter.AsObject.Object = obj;
            IntPtr address = AddressHelper.reinterpreter.AsIntPtr.Value;
            AddressHelper.reinterpreter.AsObject.Object = null;
            return address;

    public static T GetInstance<T>(IntPtr address)
        lock (AddressHelper.mutualObject)
            AddressHelper.reinterpreter.AsIntPtr.Value = address;
            return (T)AddressHelper.reinterpreter.AsObject.Object;

    // I bet you thought C# was type-safe.
    private struct ObjectReinterpreter
        [FieldOffset(0)] public ObjectWrapper AsObject;
        [FieldOffset(0)] public IntPtrWrapper AsIntPtr;

    private class ObjectWrapper
        public object Object;

    private class IntPtrWrapper
        public IntPtr Value;

Regular expression for not allowing spaces in the input field

This will help to find the spaces in the beginning, middle and ending:

var regexp = /\s/g

No suitable records were found verify your bundle identifier is correct

If you use Application Loader, then check if you are logged to the correct account. It was my case and it can happen if you manage account for various clients.

enter image description here

remove table row with specific id

ID attributes cannot start with a number and they should be unique. In any case, you can use :eq() to select a specific row using a 0-based integer:

// Remove the third row
$("#test tr:eq(2)").remove();

Alternatively, rewrite your HTML so that it's valid:

<table id="test">
 <tr id=test1><td>bla</td></tr>
 <tr id=test2><td>bla</td></tr>
 <tr id=test3><td>bla</td></tr>
 <tr id=test4><td>bla</td></tr>

And remove it referencing just the id:


How to redirect to Login page when Session is expired in Java web application?

You need to implement the HttpSessionListener interface, server will notify session time outs.

like this;

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class ApplicationSessionListener implements HttpSessionListener {

public void sessionCreated(HttpSessionEvent event) {
   System.out.println("Session Created");

public void sessionDestroyed(HttpSessionEvent event) {
   //write your logic
   System.out.println("Session Destroyed");

Check this example for better understanding

The type or namespace name 'System' could not be found

Try to

  1. Clean Solution
  2. Rebuild Solution

WPF Button with Image

You want to do something like this instead:

        <Image Source="Pictures/apple.jpg" />
        <TextBlock>Disconnect from Server</TextBlock>

What is a 'NoneType' object?

In the error message, instead of telling you that you can't concatenate two objects by showing their values (a string and None in this example), the Python interpreter tells you this by showing the types of the objects that you tried to concatenate. The type of every string is str while the type of the single None instance is called NoneType.

You normally do not need to concern yourself with NoneType, but in this example it is necessary to know that type(None) == NoneType.

How can I indent multiple lines in Xcode?

If you want to remap the standard Xcode's ?+[ to TAB, you can do the following:

  1. Install a program called "Karabiner".

  2. Go to Preferences ~> "Misc and Uninstall"

  3. In "Custom Setting" section click on the "Open private.xml" button

  4. Open the file and replace its content with the following code:

    <?xml version="1.0"?> 
            <name>Tab instead of Command+[</name>
                KeyCode::TAB, ModifierFlag::NONE,
                KeyCode::BRACKET_RIGHT, ModifierFlag::COMMAND_L | ModifierFlag::NONE
  5. Go to Preferences ~> "Change Key" ~> click on "Reload XML" button

  6. Put a tick in the checkbox which is called "Tab instead of Command+["

  7. Enjoy

enter image description here

PS: Please note that this setting works globally on your machine, not just in Xcode. However, I am sure that google might help you to find a solution how to customize it even further, applying the changes only to Xcode.

How to get multiline input from user

In Python 3.x the raw_input() of Python 2.x has been replaced by input() function. However in both the cases you cannot input multi-line strings, for that purpose you would need to get input from the user line by line and then .join() them using \n, or you can also take various lines and concatenate them using + operator separated by \n

To get multi-line input from the user you can go like:

no_of_lines = 5
lines = ""
for i in xrange(no_of_lines):



lines = []
while True:
    line = input()
    if line:
text = '\n'.join(lines)

How to get object size in memory?

Unmanaged object:

  • Marshal.SizeOf(object yourObj);

Value Types:

  • sizeof(object val)

Managed object:

Are there any worse sorting algorithms than Bogosort (a.k.a Monkey Sort)?

This page is a interesting read on the topic:

My personal favorite is Tom Duff's sillysort:

 * The time complexity of this thing is O(n^(a log n))
 * for some constant a. This is a multiply and surrender
 * algorithm: one that continues multiplying subproblems
 * as long as possible until their solution can no longer
 * be postponed.
void sillysort(int a[], int i, int j){
        int t, m;
                sillysort(a, i, m);
                sillysort(a, m+1, j);
                if(a[m]>a[j]){ t=a[m]; a[m]=a[j]; a[j]=t; }

How to force maven update?

In my case first I did was:

mvn clean install -U

Still it was showing same error then I closed project and again reopened it. Finally worked.

How to hide command output in Bash

A process normally has two outputs to screen: stdout (standard out), and stderr (standard error).

Normally informational messages go to sdout, and errors and alerts go to stderr.

You can turn off stdout for a command by doing

MyCommand >/dev/null

and turn off stderr by doing:

MyCommand 2>/dev/null

If you want both off, you can do:

MyCommand 2>&1 >/dev/null

The 2>&1 says send stderr to the same place as stdout.

python list by value not by reference

Also, you can do:

b = list(a)

This will work for any sequence, even those that don't support indexers and slices...

How to cast/convert pointer to reference in C++


You don't need to cast it because it's the same Object type, you just need to dereference it.

How to initialize a dict with keys from a list and empty value in Python?

nobody cared to give a dict-comprehension solution ?

>>> keys = [1,2,3,5,6,7]
>>> {key: None for key in keys}
{1: None, 2: None, 3: None, 5: None, 6: None, 7: None}

what does "error : a nonstatic member reference must be relative to a specific object" mean?

EncodeAndSend is not a static function, which means it can be called on an instance of the class CPMSifDlg. You cannot write this:

 CPMSifDlg::EncodeAndSend(/*...*/);  //wrong - EncodeAndSend is not static

It should rather be called as:

 CPMSifDlg dlg; //create instance, assuming it has default constructor!
 dlg.EncodeAndSend(/*...*/);   //correct 

How to format a number as percentage in R?

I did some benchmarking for speed on these answers and was surprised to see percent in the scales package so touted, given its sluggishness. I imagine the advantage is its automatic detector for for proper formatting, but if you know what your data looks like it seems clear to be avoided.

Here are the results from trying to format a list of 100,000 percentages in (0,1) to a percentage in 2 digits:

x = runif(1e5)
microbenchmark(times = 100L, andrie1(), andrie2(), richie(), krlmlr())
# Unit: milliseconds
#   expr       min        lq      mean    median        uq       max
# 1 andrie1()  91.08811  95.51952  99.54368  97.39548 102.75665 126.54918 #paste(round())
# 2 andrie2()  43.75678  45.56284  49.20919  47.42042  51.23483  69.10444 #sprintf()
# 3  richie()  79.35606  82.30379  87.29905  84.47743  90.38425 112.22889 #paste(formatC())
# 4  krlmlr() 243.19699 267.74435 304.16202 280.28878 311.41978 534.55904 #scales::percent()

So sprintf emerges as a clear winner when we want to add a percent sign. On the other hand, if we only want to multiply the number and round (go from proportion to percent without "%", then round() is fastest:

# Unit: milliseconds
#        expr      min        lq      mean    median        uq       max
# 1 andrie1()  4.43576  4.514349  4.583014  4.547911  4.640199  4.939159 # round()
# 2 andrie2() 42.26545 42.462963 43.229595 42.960719 43.642912 47.344517 # sprintf()
# 3  richie() 64.99420 65.872592 67.480730 66.731730 67.950658 96.722691 # formatC()

Xcode error "Could not find Developer Disk Image"

Just my two cents for iOS 10 (under NDA, but for people that can use it legally...)

  • Copying full folder (as other people said) works
  • Symbolic link seems not.

This was tested using Xcode 7.3 (std from Store) AND iPhone 6Plus with 10.0 (14A5261v).

jQuery show/hide options from one select drop down, when option on other select dropdown is slected

// find the first select and bind a click handler
$('#column_select').bind('click', function(){
    // retrieve the selected value
    var value = $(this).val(),
        // build a regular expression that does a head-match
        expression = new RegExp('^' + value),
        // find the second select
        $select = $('#layout_select);

    // hide all children (<option>s) of the second select,
    // check each element's value agains the regular expression built from the first select's value
    // show elements that match the expression
      return !!$(this).val().match(expression);

(this is far from perfect, but should get you there…)

How to set Navigation Drawer to be opened from right to left

Take a look at this: slide ExpandableListView at DrawerLayout form right to left

I assume you have the ActionBarDrawerToggle implemented, the trick is to override the onOptionsItemSelected(MenuItem item) method inside the ActionBarDrawerToggle object with this:

    public boolean onOptionsItemSelected(MenuItem item) {
        if (item != null && item.getItemId() == {
            if (mDrawer.isDrawerOpen(Gravity.RIGHT)) {
            } else {
            return true;
        return false;

make sure and call this from onOptionsItemSelected(MenuItem item) in the Activity:

public boolean onOptionsItemSelected(MenuItem item) {

if(mDrawerToggle.onOptionsItemSelected(item)) {
    return true;

return super.onOptionsItemSelected(item);

This will allow you to use the the home button functionality. To move the button to the right side of the action bar you will have to implement a custom action item, and maybe some other stuff to get it to work like you want.

How to open SharePoint files in Chrome/Firefox

Installing the Chrome extension IE Tab did the job for me.

It has the ability to auto-detect URLs so whenever I browse to our SharePoint it emulates Internet Explorer. Finally I can open Office documents directly from Chrome.

You can install IETab for FireFox too.

Query to check index on a table

On Oracle:

  • Determine all indexes on table:

    SELECT index_name 
     FROM user_indexes
     WHERE table_name = :table
  • Determine columns indexes and columns on index:

    SELECT index_name
         , column_position
         , column_name
      FROM user_ind_columns
     WHERE table_name = :table
     ORDER BY index_name, column_order


Create ArrayList from array

new ArrayList<>(Arrays.asList(array));

CSS: 100% font size - 100% of what?

As to my understanding it help your content adjust with different values of font family and font sizes.Thus making your content scalable. As to the issue of inhering font size we can always override by giving a specific font size for the element.

How to handle query parameters in angular 2

Angular2 v2.1.0 (stable):

The ActivatedRoute provides an observable one can subscribe.

     private route: ActivatedRoute
  ) { }

  this.route.params.subscribe(params => {
     let value = params[key];

This triggers everytime the route gets updated, as well: /home/files/123 -> /home/files/321

What is the difference between __dirname and ./ in node.js?

The gist

In Node.js, __dirname is always the directory in which the currently executing script resides (see this). So if you typed __dirname into /d1/d2/myscript.js, the value would be /d1/d2.

By contrast, . gives you the directory from which you ran the node command in your terminal window (i.e. your working directory) when you use libraries like path and fs. Technically, it starts out as your working directory but can be changed using process.chdir().

The exception is when you use . with require(). The path inside require is always relative to the file containing the call to require.

For example...

Let's say your directory structure is


and pathtest.js contains

var path = require("path");
console.log(". = %s", path.resolve("."));
console.log("__dirname = %s", path.resolve(__dirname));

and you do

cd /dir1/dir2
node pathtest.js

you get

. = /dir1/dir2
__dirname = /dir1/dir2

Your working directory is /dir1/dir2 so that's what . resolves to. Since pathtest.js is located in /dir1/dir2 that's what __dirname resolves to as well.

However, if you run the script from /dir1

cd /dir1
node dir2/pathtest.js

you get

. = /dir1
__dirname = /dir1/dir2

In that case, your working directory was /dir1 so that's what . resolved to, but __dirname still resolves to /dir1/dir2.

Using . inside require...

If inside dir2/pathtest.js you have a require call into include a file inside dir1 you would always do


because the path inside require is always relative to the file in which you are calling it. It has nothing to do with your working directory.

Ignore Typescript Errors "property does not exist on value of type"

Had a problem in Angular2, I was using the local storage to save something and it would not let me.


I had -> error -> Property 'city' does not exist on type 'Storage'.

How to fix it:



(localStorage as any).city

How can I declare enums using java

public enum NewEnum {

   private String s;

   private NewEnum(String s) {
      this.s = s);

    public String getS() {
        return this.s;

Tooltip on image

Using javascript, you can set tooltips for all the images on the page.

<!DOCTYPE html>
    <img src="" alt="Food">
    <img src="" alt="Pizza">
     //image objects
     var imageEls = document.getElementsByTagName("img");
     for(var i=0;i<imageEls.length;i++){
        //imageEls[i].title="Title of your choice";

How to check if a particular service is running on Ubuntu

Maybe what you want is the ps command;

ps -ef

will show you all processes running. Then if you have an idea of what you're looking for use grep to filter;

ps -ef | grep postgres

Build .NET Core console application to output an EXE

UPDATE for .NET 5!

The below applies on/after NOV2020 when .NET 5 is officially out.

(see quick terminology section below, not just the How-to's)

How-To (CLI)


  • Download latest version of the .net 5 SDK. Link


  1. Open a terminal (e.g: bash, command prompt, powershell) and in the same directory as your .csproj file enter the below command:
dotnet publish --output "{any directory}" --runtime {runtime} --configuration {Debug|Release} -p:PublishSingleFile={true|false} -p:PublishTrimmed={true|false} --self-contained {true|false}


dotnet publish --output "c:/temp/myapp" --runtime win-x64 --configuration Release -p:PublishSingleFile=true -p:PublishTrimmed=true --self-contained true

How-To (GUI)


  • If reading pre NOV2020: Latest version of Visual Studio Preview*
  • If reading NOV2020+: Latest version of Visual Studio*

*In above 2 cases, the latest .net5 SDK will be automatically installed on your PC.


  1. Right-Click on Project, and click Publish
    enter image description here

  2. Click Start and choose Folder target, click next and choose Folder Choose Folder Target

  3. Enter any folder location, and click Finish

  4. Click on Edit
    enter image description here

  5. Choose a Target Runtime and tick on Produce Single File and save.* enter image description here

  6. Click Publish

  7. Open a terminal in the location you published your app, and run the .exe. Example: enter image description here

A little bit of terminology

Target Runtime
See the list of RID's

Deployment Mode

  • Framework Dependent means a small .exe file produced but app assumed .Net 5 is installed on the host machine
  • Self contained means a bigger .exe file because the .exe includes the framework but then you can run .exe on any machine, no need for .Net 5 to be pre-installed. NOTE: WHEN USING SELF CONTAINED, ADDITIONAL DEPENDENCIES (.dll's) WILL BE PRODUCED, NOT JUST THE .EXE

Enable ReadyToRun compilation
TLDR: it's .Net5's equivalent of Ahead of Time Compilation (AOT). Pre-compiled to native code, app would usually boot up faster. App more performant (or not!), depending on many factors. More info here

Trim unused assemblies
When set to true, dotnet will generate a very lean and small .exe and only include what it needs. Be careful here. Example: when using reflection in your app you probably don't want to set this flag to true.

Microsoft Doc

Previous Post

UPDATE (31-OCT-2019)

For anyone that wants to do this via a GUI and:

  • Is using Visual Studio 2019
  • Has .NET Core 3.0 installed (included in latest version of Visual Studio 2019)
  • Wants to generate a single file

Enter image description here

Enter image description here

Enter image description here

Enter image description here

Enter image description here

Enter image description here

Enter image description here

enter image description here

Enter image description here


Notice the large file size for such a small application

Enter image description here

You can add the "PublishTrimmed" property. The application will only include components that are used by the application. Caution: don't do this if you are using reflection

Enter image description here

Publish again

Enter image description here

Python String and Integer concatenation

Concatenation of a string and integer is simple: just use


MySQL error code: 1175 during UPDATE in MySQL Workbench


# your code SQL here


Convert List(of object) to List(of string)

No - if you want to convert ALL elements of a list, you'll have to touch ALL elements of that list one way or another.

You can specify / write the iteration in different ways (foreach()......, or .ConvertAll() or whatever), but in the end, one way or another, some code is going to iterate over each and every element and convert it.


How to load/reference a file as a File instance from the classpath

Try getting hold of a URL for your classpath resource:

URL url = this.getClass().getResource("/com/path/to/file.txt")

Then create a file using the constructor that accepts a URI:

File file = new File(url.toURI());

How to use Tomcat 8 in Eclipse?

Alternatively we can use eclipse update site (Help -> Install New Features -> Add Site (urls below) -> Select desired Features).

For Luna:

For Kepler:

For Helios:

For older version:

How does HTTP_USER_AGENT work?

Visit that page, it'll give you a good explanation of each element of your user agent.


MozillaProductSlice. Claims to be a Mozilla based user agent, which is only true for Gecko browsers like Firefox and Netscape. For all other user agents it means 'Mozilla-compatible'. In modern browsers, this is only used for historical reasons. It has no real meaning anymore

How to convert UTF8 string to byte array?

JavaScript Strings are stored in UTF-16. To get UTF-8, you'll have to convert the String yourself.

One way is to mix encodeURIComponent(), which will output UTF-8 bytes URL-encoded, with unescape, as mentioned on ecmanaut.

var utf8 = unescape(encodeURIComponent(str));

var arr = [];
for (var i = 0; i < utf8.length; i++) {

Count a list of cells with the same background color

Yes VBA is the way to go.

But, if you don't need to have a cell with formula that auto-counts/updates the number of cells with a particular colour, an alternative is simply to use the 'Find and Replace' function and format the cell to have the appropriate colour fill.

Hitting 'Find All' will give you the total number of cells found at the bottom left of the dialogue box.

enter image description here

This becomes especially useful if your search range is massive. The VBA script will be very slow but the 'Find and Replace' function will still be very quick.

How to get textLabel of selected row in swift?

Maintain an array which stores data in the cellforindexPath method itself :-

[arryname objectAtIndex:indexPath.row];

Using same code in the didselectaAtIndexPath method too.. Good luck :)

What does "<html xmlns="">" do?

Its an XML namespace. It is required when you use XHTML 1.0 or 1.1 doctypes or application/xhtml+xml mimetypes.

You should be using HTML5 doctype, then you don't need it for text/html. Better start from template like this :

<!DOCTYPE html>
        <meta charset=utf-8 />
        <title>domcument title</title>
        <link rel="stylesheet" href="/stylesheet.css" type="text/css" />
            <!-- your html content -->
            <script src="/script.js"></script>

When you have put your Doctype straight - do and validate you html and your css .
That usually will sove you layout issues.

Is there a way to retrieve the view definition from a SQL Server using plain ADO?

This example:Views Collection, CommandText Property Example (VB) Shows how to use ADOX to maintain VIEWS by changing COMMAND related to VIEW. But instead using it like this:

 Set cmd = cat.Views("AllCustomers").Command  

' Update the CommandText of the command.  
cmd.CommandText = _  
"Select CustomerId, CompanyName, ContactName From Customers"  

just try to use this way:

Set CommandText = cat.Views("AllCustomers").Command.CommandText

how to view the contents of a .pem certificate

Use the -printcert command like this:

keytool -printcert -file certificate.pem

Angular exception: Can't bind to 'ngForIn' since it isn't a known native property


Use let...of instead of !!

If you're new to Angular (>2.x) and possibly migrating from Angular1.x, most likely you're confusing in with of. As andreas has mentioned in the comments below for ... of iterates over values of an object while for ... in iterates over properties in an object. This is a new feature introduced in ES2015.

Simply replace:

<!-- Iterate over properties (incorrect in our case here) -->
<div *ngFor="let talk in talks">


<!-- Iterate over values (correct way to use here) -->
<div *ngFor="let talk of talks">

So, you must replace in with of inside ngFor directive to get the values.

if else condition in blade file (laravel 5.3)

No curly braces required you can directly write

@if($user->status =='waiting')         
      <td><a href="#" class="viewPopLink btn btn-default1" role="button" data-id="{{ $user->travel_id }}" data-toggle="modal" data-target="#myModal">Approve/Reject<a></td>         
      <td>{{ $user->status }}</td>        

How to add additional fields to form before submit?

Yes.You can try with some hidden params.

  $("#form").submit( function(eventObj) {
      $("<input />").attr("type", "hidden")
          .attr("name", "something")
          .attr("value", "something")
      return true;

How to remove frame from matplotlib (pyplot.figure vs matplotlib.figure ) (frameon=False Problematic in matplotlib)

Building up on @peeol's excellent answer, you can also remove the frame by doing

for spine in plt.gca().spines.values():

To give an example (the entire code sample can be found at the end of this post), let's say you have a bar plot like this,

enter image description here

you can remove the frame with the commands above and then either keep the x- and ytick labels (plot not shown) or remove them as well doing

plt.tick_params(top='off', bottom='off', left='off', right='off', labelleft='off', labelbottom='on')

In this case, one can then label the bars directly; the final plot could look like this (code can be found below):

enter image description here

Here is the entire code that is necessary to generate the plots:

import matplotlib.pyplot as plt
import numpy as np


xvals = list('ABCDE')
yvals = np.array(range(1, 6))

position = np.arange(len(xvals))

mybars =, yvals, align='center', linewidth=0)
plt.xticks(position, xvals)

plt.title('My great data')

# get rid of the frame
for spine in plt.gca().spines.values():

# remove all the ticks and directly label each bar with respective value
plt.tick_params(top='off', bottom='off', left='off', right='off', labelleft='off', labelbottom='on')


# direct label each bar with Y axis values
for bari in mybars:
    height = bari.get_height()
    plt.gca().text(bari.get_x() + bari.get_width()/2, bari.get_height()-0.2, str(int(height)),
                 ha='center', color='white', fontsize=15)

How to get a list of installed Jenkins plugins with name and version pair

There are lots of way to fetch this information but I am writing two ways as below : -

1. Get the jenkins cli.

The jenkins CLI will allow us to interact with our jenkins server from the command line. We can get it with a simple curl call.

curl 'localhost:8080/jnlpJars/jenkins-cli.jar' > jenkins-cli.jar

2. Create a groovy script. OR from jenkins script console

We need to create a groovy script to parse the information we receive from the jenkins API. This will output each plugin with its version. Save the following as plugins.groovy.

def plugins = jenkins.model.Jenkins.instance.getPluginManager().getPlugins() plugins.each {println "${it.getShortName()}: ${it.getVersion()}"}

IE9 jQuery AJAX with CORS returns "Access is denied"

Try to use jquery-transport-xdr jQuery plugin for CORS requests in IE8/9.

Python loop that also accesses previous and next values

Using generators, it is quite simple:

signal = ['?Signal value?']
def pniter( iter, signal=signal ):
    iA = iB = signal
    for iC in iter:
        if iB is signal:
            iB = iC
            yield iA, iB, iC
        iA = iB
        iB = iC
    iC = signal
    yield iA, iB, iC

if __name__ == '__main__':
    print('test 1:')
    for a, b, c in pniter( range( 10 )):
        print( a, b, c )
    print('\ntest 2:')
    for a, b, c in pniter([ 20, 30, 40, 50, 60, 70, 80 ]):
        print( a, b, c )
    print('\ntest 3:')
    cam = { 1: 30, 2: 40, 10: 9, -5: 36 }
    for a, b, c in pniter( cam ):
        print( a, b, c )
    for a, b, c in pniter( cam ):
        print( a, a if a is signal else cam[ a ], b, b if b is signal else cam[ b ], c, c if c is signal else cam[ c ])
    print('\ntest 4:')
    for a, b, c in pniter([ 20, 30, None, 50, 60, 70, 80 ]):
        print( a, b, c )
    print('\ntest 5:')
    for a, b, c in pniter([ 20, 30, None, 50, 60, 70, 80 ], ['sig']):
        print( a, b, c )
    print('\ntest 6:')
    for a, b, c in pniter([ 20, ['?Signal value?'], None, '?Signal value?', 60, 70, 80 ], signal ):
        print( a, b, c )

Note that tests that include None and the same value as the signal value still work, because the check for the signal value uses "is" and the signal is a value that Python doesn't intern. Any singleton marker value can be used as a signal, though, which might simplify user code in some circumstances.

What is a practical use for a closure in JavaScript?

I wrote an article a while back about how closures can be used to simplify event-handling code. It compares ASP.NET event handling to client-side jQuery.

How to add Active Directory user group as login in SQL Server

You can use T-SQL:

use master

I use this as a part of restore from production server to testing machine:

USE master
RESTORE DATABASE yourDbName FROM DISK = 'd:\DropBox\backup\myDB.bak'

You will need to use localized name of services in case of German or French Windows, see How to create a SQL Server login for a service account on a non-English Windows?

How can I specify my .keystore file with Spring Boot and Tomcat?

It turns out that there is a way to do this, although I'm not sure I've found the 'proper' way since this required hours of reading source code from multiple projects. In other words, this might be a lot of dumb work (but it works).

First, there is no way to get at the server.xml in the embedded Tomcat, either to augment it or replace it. This must be done programmatically.

Second, the 'require_https' setting doesn't help since you can't set cert info that way. It does set up forwarding from http to https, but it doesn't give you a way to make https work so the forwarding isnt helpful. However, use it with the stuff below, which does make https work.

To begin, you need to provide an EmbeddedServletContainerFactory as explained in the Embedded Servlet Container Support docs. The docs are for Java but the Groovy would look pretty much the same. Note that I haven't been able to get it to recognize the @Value annotation used in their example but its not needed. For groovy, simply put this in a new .groovy file and include that file on the command line when you launch spring boot.

Now, the instructions say that you can customize the TomcatEmbeddedServletContainerFactory class that you created in that code so that you can alter web.xml behavior, and this is true, but for our purposes its important to know that you can also use it to tailor server.xml behavior. Indeed, reading the source for the class and comparing it with the Embedded Tomcat docs, you see that this is the only place to do that. The interesting function is TomcatEmbeddedServletContainerFactory.addConnectorCustomizers(), which may not look like much from the Javadocs but actually gives you the Embedded Tomcat object to customize yourself. Simply pass your own implementation of TomcatConnectorCustomizer and set the things you want on the given Connector in the void customize(Connector con) function. Now, there are about a billion things you can do with the Connector and I couldn't find useful docs for it but the createConnector() function in this this guys personal Spring-embedded-Tomcat project is a very practical guide. My implementation ended up looking like this:

package com.deepdownstudios.server

import org.springframework.boot.context.embedded.tomcat.TomcatConnectorCustomizer
import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory
import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory
import org.apache.catalina.connector.Connector;
import org.apache.coyote.http11.Http11NioProtocol;
import org.springframework.boot.*
import org.springframework.stereotype.*

class MyConfiguration {

public EmbeddedServletContainerFactory servletContainer() {
final int port = 8443;
final String keystoreFile = "/path/to/keystore"
final String keystorePass = "keystore-password"
final String keystoreType = "pkcs12"
final String keystoreProvider = "SunJSSE"
final String keystoreAlias = "tomcat"

TomcatEmbeddedServletContainerFactory factory = 
        new TomcatEmbeddedServletContainerFactory(this.port);
factory.addConnectorCustomizers( new TomcatConnectorCustomizer() {
    void    customize(Connector con) {
        Http11NioProtocol proto = (Http11NioProtocol) con.getProtocolHandler();
        proto.setProperty("keystoreProvider", keystoreProvider);
return factory;

The Autowiring will pick up this implementation an run with it. Once I fixed my busted keystore file (make sure you call keytool with -storetype pkcs12, not -storepass pkcs12 as reported elsewhere), this worked. Also, it would be far better to provide the parameters (port, password, etc) as configuration settings for testing and such... I'm sure its possible if you can get the @Value annotation to work with Groovy.

Detect if an element is visible with jQuery

You're looking for:


Although you should probably change your selector to use jQuery considering you're using it in other places anyway:

if($('#testElement').is(':visible')) {
    // Code

It is important to note that if any one of a target element's parent elements are hidden, then .is(':visible') on the child will return false (which makes sense).

jQuery 3

:visible has had a reputation for being quite a slow selector as it has to traverse up the DOM tree inspecting a bunch of elements. There's good news for jQuery 3, however, as this post explains (Ctrl + F for :visible):

Thanks to some detective work by Paul Irish at Google, we identified some cases where we could skip a bunch of extra work when custom selectors like :visible are used many times in the same document. That particular case is up to 17 times faster now!

Keep in mind that even with this improvement, selectors like :visible and :hidden can be expensive because they depend on the browser to determine whether elements are actually displaying on the page. That may require, in the worst case, a complete recalculation of CSS styles and page layout! While we don’t discourage their use in most cases, we recommend testing your pages to determine if these selectors are causing performance issues.

Expanding even further to your specific use case, there is a built in jQuery function called $.fadeToggle():

function toggleTestElement() {

Send Email to multiple Recipients with MailMessage?

I've tested this using the following powershell script and using (,) between the addresses. It worked for me!

$EmailFrom = "<[email protected]>";
$EmailPassword = "<password>";
$EmailTo = "<[email protected]>,<[email protected]>";
$SMTPServer = "<>";
$SMTPPort = <port>;
$SMTPClient = New-Object Net.Mail.SmtpClient($SmtpServer,$SMTPPort);
$SMTPClient.EnableSsl = $true;
$SMTPClient.Credentials = New-Object System.Net.NetworkCredential($EmailFrom, $EmailPassword);
$Subject = "Notification from XYZ";
$Body = "this is a notification from XYZ Notifications..";
$SMTPClient.Send($EmailFrom, $EmailTo, $Subject, $Body);

Removing "bullets" from unordered list <ul>

In my case

li {
  list-style-type : none;

It doesn't show the bullet but leaved some space for the bullet.

I use

li {
  list-style-type : '';

It works perfectly.

Cannot connect to the Docker daemon on macOS

on OSX assure you have launched the Docker application before issuing

docker ps

or docker build ... etc ... yes it seems strange and somewhat misleading that issuing

docker --version

gives version even though the docker daemon is not running ... ditto for those other version cmds ... I just encountered exactly the same symptoms ... this behavior on OSX is different from on linux

MySQL Delete all rows from table and reset ID to zero

if you want to use truncate use this:

TRUNCATE table $table_name; 

Print PDF directly from JavaScript

Here is a function to print a PDF from an iframe.

You just need to pass the URL of the PDF to the function. It will create an iframe and trigger print once the PDF is load.

Note that the function doesn't destroy the iframe. Instead, it reuses it each time the function is call. It's hard to destroy the iframe because it is needed until the printing is done, and the print method doesn't has callback support (as far as I know).

printPdf = function (url) {
  var iframe = this._printIframe;
  if (!this._printIframe) {
    iframe = this._printIframe = document.createElement('iframe');
    document.body.appendChild(iframe); = 'none';
    iframe.onload = function() {
      setTimeout(function() {
      }, 1);

  iframe.src = url;

Javascript Regex: How to put a variable inside a regular expression?

Here's an pretty useless function that return values wrapped by specific characters. :)


function getValsWrappedIn(str,c1,c2){
    var rg = new RegExp("(?<=\\"+c1+")(.*?)(?=\\"+c2+")","g"); 
    return str.match(rg);

var exampleStr = "Something (5) or some time (19) or maybe a (thingy)";
var results =  getValsWrappedIn(exampleStr,"(",")")

// Will return array ["5","19","thingy"]

Generic type conversion FROM string


TypeDescriptor is class having method GetConvertor which accept a Type object and then you can call ConvertFrom method to convert the value for that specified object.

How can I turn a List of Lists into a List in Java 8?

You can use the flatCollect() pattern from Eclipse Collections.

MutableList<List<Object>> list = Lists.mutable.empty();
MutableList<Object> flat = list.flatCollect(each -> each);

If you can't change list from List:

List<List<Object>> list = new ArrayList<>();
List<Object> flat = ListAdapter.adapt(list).flatCollect(each -> each);

Note: I am a contributor to Eclipse Collections.

nginx: send all requests to a single html page

This worked for me:

location / {
    alias /path/to/my/indexfile/;
    try_files $uri /index.html;

This allowed me to create a catch-all URL for a javascript single-page app. All static files like css, fonts, and javascript built by npm run build will be found if they are in the same directory as index.html.

If the static files were in another directory, for some reason, you'd also need something like:

# Static pages generated by "npm run build"
location ~ ^/css/|^/fonts/|^/semantic/|^/static/ {
    alias /path/to/my/staticfiles/;

IF EXIST C:\directory\ goto a else goto b problems windows XP batch files

If you want to rule out any problems with the else part, try removing the else and place the command on a new line. Like this:

IF EXIST D:\RPS_BACKUP\backups_temp\ goto tempexists
goto tempexistscontinue  

Unsupported operand type(s) for +: 'int' and 'str'


str_list = " ".join([str(ele) for ele in numlist])

this statement will give you each element of your list in string format

print("The list now looks like [{0}]".format(str_list))


change print(numlist.pop(2)+" has been removed") to

print("{0} has been removed".format(numlist.pop(2)))

as well.

Loading basic HTML in Node.js

This would probably be some what better since you will be streaming the file(s) rather than loading it all into memory like fs.readFile.

var http = require('http');
var fs = require('fs');
var path = require('path');
var ext = /[\w\d_-]+\.[\w\d]+$/;

http.createServer(function(req, res){
    if (req.url === '/') {
        res.writeHead(200, {'Content-Type': 'text/html'});
    } else if (ext.test(req.url)) {
        fs.exists(path.join(__dirname, req.url), function (exists) {
            if (exists) {
                res.writeHead(200, {'Content-Type': 'text/html'});
            } else {
                res.writeHead(404, {'Content-Type': 'text/html'});
    } else {
        //  add a RESTful service

Getting the Username from the HKEY_USERS values

Done it, by a bit of creative programming,

  1. Enum the Keys in HKEY_USERS for those funny number keys...

  2. Enum the keys in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList\

and you will find the same numbers.... Now in those keys look at the String value: ProfileImagePath = "SomeValue" where the values are either:

"%systemroot%\system32\config\systemprofile"... not interested in this one... as its not a directory path...

%SystemDrive%\Documents and Settings\LocalService - "Local Services" %SystemDrive%\Documents and Settings\NetworkService "NETWORK SERVICE"


%SystemDrive%\Documents and Settings\USER_NAME, which translates directly to the "USERNAME" values in most un-tampered systems, ie. where the user has not changed the their user name after a few weeks or altered the paths explicitly...

MySql Error: 1364 Field 'display_name' doesn't have default value

All of these answers are a good way, but I don't think you want to always go to your DB and modify the default value that you have set to NULL.

I suggest you go to the app/User.php and modify the protected $fillable so it will take your new fields in the data array used to register.

Let's say you add a new input field called "first_name", your $fillable should be something like this :

protected $fillable = [ 'first_name', 'email', 'password',]; 

This did it for me. Good luck!

How do I create a local database inside of Microsoft SQL Server 2014?

Warning! SQL Server 14 Express, SQL Server Management Studio, and SQL 2014 LocalDB are separate downloads, make sure you actually installed SQL Server and not just the Management Studio! SQL Server 14 express with LocalDB download link

Youtube video about entire process.
Writeup with pictures about installing SQL Server

How to select a local server:

When you are asked to connect to a 'database server' right when you open up SQL Server Management Studio do this:

1) Make sure you have Server Type: Database

2) Make sure you have Authentication: Windows Authentication (no username & password)

3) For the server name field look to the right and select the drop down arrow, click 'browse for more'

4) New window pops up 'Browse for Servers', make sure to pick 'Local Servers' tab and under 'Database Engine' you will have the local server you set up during installation of SQL Server 14

How do I create a local database inside of Microsoft SQL Server 2014?

1) After you have connected to a server, bring up the Object Explorer toolbar under 'View' (Should open by default)

2) Now simply right click on 'Databases' and then 'Create new Database' to be taken through the database creation tools!

How do I create and access the global variables in Groovy?

Could not figure out what you want, but you need something like this ? :

?def a = { b -> b = 1 }
?bValue = a()
println b // prints 1

Now bValue contains the value of b which is a variable in the closure a. Now you can do anything with bValue Let me know if i have misunderstood your question

Postgres password authentication fails

I came across this question, and the answers here didn't work for me; i couldn't figure out why i can't login and got the above error.

It turns out that postgresql saves usernames lowercase, but during authentication it uses both upper- and lowercase.


will create a user with the username 'mynewuser' and password 'passWord'.

This means you have to authenticate with 'mynewuser', and not with 'myNewUser'. For a newbie in pgsql like me, this was confusing. I hope it helps others who run into this problem.

Connect Android to WiFi Enterprise network EAP(PEAP)

Finally, I've defeated my CiSCO EAP-FAST corporate wifi network, and all our Android devices are now able to connect to it.

The walk-around I've performed in order to gain access to this kind of networks from an Android device are easiest than you can imagine.

There's a Wifi Config Editor in the Google Play Store you can use to "activate" the secondary CISCO Protocols when you are setting up a EAP wifi connection.

Its name is Wifi Config Advanced Editor.

  • First, you have to setup your wireless network manually as close as you can to your "official" corporate wifi parameters.

  • Save it.

  • Go to the WCE and edit the parameters of the network you have created in the previous step.

  • There are 3 or 4 series of settings you should activate in order to force the Android device to use them as a way to connect (the main site I think you want to visit is Enterprise Configuration, but don't forget to check all the parameters to change them if needed.
    As a suggestion, even if you have a WPA2 EAP-FAST Cipher, try LEAP in your setup. It worked for me as a charm.

  • When you finished to edit the config, go to the main Android wifi controller, and force to connect to this network.

  • Do not Edit the network again with the Android wifi interface.

I have tested it on Samsung Galaxy 1 and 2, Note mobile devices, and on a Lenovo Thinkpad Tablet.

How to check if a given directory exists in Ruby


Dir[] returns an array, so it will never be nil. If you want to do it your way, you could do


which will return true if it wasn't found.

Taskkill /f doesn't kill a process

The taskkill and powershell (kill) methods didn't work for me; it still said "Access Denied".

I had better luck with this:

wmic process where "name='myprocessname.exe'" delete

How to send Basic Auth with axios

An example (axios_example.js) using Axios in Node.js:

const axios = require('axios');
const express = require('express');
const app = express();
const port = process.env.PORT || 5000;

app.get('/search', function(req, res) {
    let query = req.query.queryStr;
    let url = `${query}`;

        auth: {
            username: 'xxxxxxxxxxxxx',
            password: 'xxxxxxxxxxxxx'
    .then(function (response) {
    .catch(function (error) {

var server = app.listen(port);

Be sure in your project directory you do:

npm init
npm install express
npm install axios
node axios_example.js

You can then test the Node.js REST API using your browser at: http://localhost:5000/search?queryStr=xxxxxxxxx


Rails DB Migration - How To Drop a Table?

ActiveRecord::Base.connection.drop_table :table_name

Can local storage ever be considered secure?

As an exploration of this topic, I have a presentation titled "Securing TodoMVC Using the Web Cryptography API" (video, code).

It uses the Web Cryptography API to store the todo list encrypted in localStorage by password protecting the application and using a password derived key for encryption. If you forget or lose the password, there is no recovery. (Disclaimer - it was a POC and not intended for production use.)

As the other answers state, this is still susceptible to XSS or malware installed on the client computer. However, any sensitive data would also be in memory when the data is stored on the server and the application is in use. I suggest that offline support may be the compelling use case.

In the end, encrypting localStorage probably only protects the data from attackers that have read only access to the system or its backups. It adds a small amount of defense in depth for OWASP Top 10 item A6-Sensitive Data Exposure, and allows you to answer "Is any of this data stored in clear text long term?" correctly.

standard size for html newsletter template

Short answer: 400-800 pixels.

What I have read is that HTML newsletter width should be as narrow as possible without being too narrow. For instance, 400-500 pixels for a one column layout is a lower limit. Any less may look too weird.

Today's widescreen monitors allow for more horizontal pixels and most web email clients will either be of the two-column variety (Gmail) or 3-pane layout where the content window bellow the inbox list (Hotmail and Yahoo). In either case, you can be okay with 800 pixels if you're targeting the 1280 wide audience. An older or less technical audience may have older, square monitors.

There is the problem of Outlook having a three-column layout. That limits the width of your email even more. With them, you may want to go even narrower.

I just recently created a template that required an ad banner that is 730 pixels wide. It was near in the wide range, but not so much that most people could not double-click the email an open a new window in Outlook (the web email users should be okay for the most part).

Hope this advice helps.

Reading int values from SqlDataReader

based on Sam Holder's answer, you could make an extension method for that

namespace adonet.extensions
  public static class AdonetExt
    public static int GetInt32(this SqlDataReader reader, string columnName)
      return reader.GetInt32(reader.GetOrdinal(columnName));

and use it like this

using adonet.extensions;


int farmsize = reader.GetInt32("farmsize");

assuming there is no GetInt32(string) already in SqlDataReader - if there is any, just use some other method name instead

Check a collection size with JSTL

As suggested by @Joel and @Mark Chorley in earlier comments:

${empty companies}

This checks for null and empty lists/collections/arrays. It doesn't get you the length but it satisfies the example in the OP. If you can get away with it this is just cleaner than importing a tag library and its crusty syntax like gt.

ViewDidAppear is not called when opening app from background

Swift 4.2. version

Register with the NotificationCenter in viewDidLoad to be notified when the app returns from background

NotificationCenter.default.addObserver(self, selector: #selector(doSomething), name: UIApplication.willEnterForegroundNotification, object: nil)

Implement the method that should be called.

@objc private func doSomething() {
    // Do whatever you want, for example update your view.

You can remove the observer once the ViewController is destroyed. This is only required below iOS9 and macOS 10.11

deinit {

How do I style appcompat-v7 Toolbar like Theme.AppCompat.Light.DarkActionBar?

Ok after having sunk way to much time into this problem this is the way I managed to get the appearance I was hoping for. I'm making it a separate answer so I can get everything in one place.

It's a combination of factors.

Firstly, don't try to get the toolbars to play nice through just themes. It seems to be impossible.

So apply themes explicitly to your Toolbars like in oRRs answer


<?xml version="1.0" encoding="utf-8"?>
    app:popupTheme="@style/Dark.Overlay.LightPopup" />

However this is the magic sauce. In order to actually get the background colors I was hoping for you have to override the background attribute in your Toolbar themes


    I expected android:colorBackground to be what I was looking for but
    it seems you have to override android:background
<style name="Dark.Overlay" parent="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
    <item name="android:background">?attr/colorPrimary</item>

<style name="Dark.Overlay.LightPopup" parent="ThemeOverlay.AppCompat.Light">
    <item name="android:background">@color/material_grey_200</item>

then just include your toolbar layout in your other layouts

<include android:id="@+id/mytoolbar" layout="@layout/toolbar" />

and you're good to go.

Hope this helps someone else so you don't have to spend as much time on this as I have.

(if anyone can figure out how to make this work using just themes, ie not having to apply the themes explicitly in the layout files I'll gladly support their answer instead)


So apparently posting a more complete answer was a downvote magnet so I'll just accept the imcomplete answer above but leave this answer here in case someone actually needs it. Feel free to keep downvoting if it makes you happy though.

The system cannot find the file specified in java

When you run a jar, your Main class itself becomes args[0] and your filename comes immediately after.

I had the same issue: I could locate my file when provided the absolute path from eclipse (because I was referring to the file as args[0]). Yet when I run the same from jar, it was trying to locate my main class - which is when I got the idea that I should be reading my file from args[1].

Limiting the number of characters per line with CSS

That's not possible with CSS, you will have to use the Javascript for that. Although you can set the width of the p to as much as 30 characters and next letters will automatically come down but again this won't be that accurate and will vary if the characters are in capital.

fatal: bad default revision 'HEAD'

This seems to occur when .git/HEAD refers to a branch which does not exist. I ran into this error in a repo that had nothing in .git/refs/heads. I have no idea how the repo got into that state, I inherited from someone that left the company.

RequestDispatcher.forward() vs HttpServletResponse.sendRedirect()

Request Dispatcher is an Interface which is used to dispatch the request or response from web resource to the another web resource. It contains mainly two methods.

  1. request.forward(req,res): This method is used forward the request from one web resource to another resource. i.e from one servlet to another servlet or from one web application to another web appliacation.

  2. response.include(req,res): This method is used include the response of one servlet to another servlet

NOTE: BY using Request Dispatcher we can forward or include the request or responses with in the same server.

request.sendRedirect(): BY using this we can forward or include the request or responses across the different servers. In this the client gets a intimation while redirecting the page but in the above process the client will not get intimation

What does %>% mean in R

Use ?'%*%' to get the documentation.

%*% is matrix multiplication. For matrix multiplication, you need an m x n matrix times an n x p matrix.

How to change the DataTable Column Name?

Rename the Column by doing the following:

dataTable.Columns["ColumnName"].ColumnName = "newColumnName";

Is it possible to declare a variable in Gradle usable in Java?

rciovati's answer is entirely correct I just wanted to add one more tidbit that you can also create variables for every build type within the default config portion of your build.gradle. This would look like this:

android {
    defaultConfig {
        buildConfigField "String", "APP_NAME", "\"APP_NAME\""

This will allow you to have access to through


Just wanted to make a note of this scenario as well if you want a common config.

Timeout function if it takes too long to finish

The process for timing out an operations is described in the documentation for signal.

The basic idea is to use signal handlers to set an alarm for some time interval and raise an exception once that timer expires.

Note that this will only work on UNIX.

Here's an implementation that creates a decorator (save the following code as

from functools import wraps
import errno
import os
import signal

class TimeoutError(Exception):

def timeout(seconds=10, error_message=os.strerror(errno.ETIME)):
    def decorator(func):
        def _handle_timeout(signum, frame):
            raise TimeoutError(error_message)

        def wrapper(*args, **kwargs):
            signal.signal(signal.SIGALRM, _handle_timeout)
                result = func(*args, **kwargs)
            return result

        return wraps(func)(wrapper)

    return decorator

This creates a decorator called @timeout that can be applied to any long running functions.

So, in your application code, you can use the decorator like so:

from timeout import timeout

# Timeout a long running function with the default expiry of 10 seconds.
def long_running_function1():

# Timeout after 5 seconds
def long_running_function2():

# Timeout after 30 seconds, with the error "Connection timed out"
@timeout(30, os.strerror(errno.ETIMEDOUT))
def long_running_function3():

How to watch for array changes?

Not sure if this covers absolutely everything, but I use something like this (especially when debugging) to detect when an array has an element added:

var array = [1,2,3,4];
array = new Proxy(array, {
    set: function(target, key, value) {
        if (Number.isInteger(Number(key)) || key === 'length') {
            debugger; //or other code
        target[key] = value;
        return true;

Python datetime - setting fixed hour and minute after using strptime to get day,month,year

Use datetime.replace:

from datetime import datetime
dt = datetime.strptime('26 Sep 2012', '%d %b %Y')
newdatetime = dt.replace(hour=11, minute=59)

How to log cron jobs?

On Ubuntu you can enable a cron.log file to contain just the CRON entries.

Uncomment the line that mentions cron in /etc/rsyslog.d/50-default.conf file:

#  Default rules for rsyslog.

#                       For more information see rsyslog.conf(5) and /etc/rsyslog.conf

# First some standard log files.  Log by facility.
auth,authpriv.*                 /var/log/auth.log
*.*;auth,authpriv.none          -/var/log/syslog
#cron.*                          /var/log/cron.log

Save and close the file and then restart the rsyslog service:

sudo systemctl restart rsyslog

You can now see cron log entries in its own file:

sudo tail -f /var/log/cron.log

Sample outputs:

Jul 18 07:05:01 machine-host-name CRON[13638]: (root) CMD (command -v debian-sa1 > /dev/null && debian-sa1 1 1)

However, you will not see more information about what scripts were actually run inside /etc/cron.daily or /etc/cron.hourly, unless those scripts direct output to the cron.log (or perhaps to some other log file).

If you want to verify if a crontab is running and not have to search for it in cron.log or syslog, create a crontab that redirects output to a log file of your choice - something like:

# For more information see the manual pages of crontab(5) and cron(8)
# m h  dom mon dow   command
30 2 * * 1 /usr/local/sbin/certbot-auto renew >> /var/log/le-renew.log 2>&1

Steps taken from:

Programmatically get height of navigation bar

If you want to get the navigationBar height only, it's simple:

extension UIViewController{
   var navigationBarHeight: CGFloat {
       return self.navigationController?.navigationBar.frame.height ?? 0.0

However, if you need the height of top notch of iPhone you don't need to get the navigationBar height and add to it the statusBar height, you can simply call safeAreaInsets that's why exist.

SQL Server: Is it possible to insert into two tables at the same time?

Before being able to do a multitable insert in Oracle, you could use a trick involving an insert into a view that had an INSTEAD OF trigger defined on it to perform the inserts. Can this be done in SQL Server?

Create dataframe from a matrix

I've found the following "cheat" to work very neatly and error-free

> dimnames <- list(time=c(0, 0.5, 1), name=c("C_0", "C_1"))
> mat <- matrix(data, ncol=2, nrow=3, dimnames=dimnames)
> head(mat, 2) #this returns the number of rows indicated in a data frame format
> df <- data.frame(head(mat, 2)) #"data.frame" might not be necessary

Et voila!

Chrome: console.log, console.debug are not working

In my case was webpack having the UglifyPlugin running with drop_console: true set

Android Studio update -Error:Could not run build action using Gradle distribution

I had same issue. I have tried many things but nothing worked Until I try following:

  1. Close Android Studio
  2. Delete any directory matching gradle-[version]-all within C:\Users\<username>\.gradle\wrapper\dists\. If you encounter a "File in use" error (or similar), terminate any running Java executables.
  3. Open Android Studio as Administrator.
  4. Try to sync project files.
  5. If the above does not work, try restarting your computer and/or delete the project's .gradle directory.
  6. Open the problem project and trigger a Gradle sync.

Creating a Zoom Effect on an image on hover using CSS?

.aku { 
    transition: all .2s ease-in-out; 

.aku:hover {
    transform: scale(1.1); 

Icons missing in jQuery UI

I saw in console that whenever I open my datepicker that I get 404 Not found error for this image file ui-bg_glass_75_e6e6e6_1x400.png

I downloaded the image from github and put it in my local under jquery-ui folder. Now the problem is solved.

Other image files found here: