Programs & Examples On #Grub

GENERAL GRUB SUPPORT IS OFF-TOPIC. Support questions may be asked on GRUB, the GNU GRand Unified Bootloader, is a boot loader used on x86 systems, typically used to boot Linux. Questions about using or configuring GRUB are rarely on-topic for Stack Overflow outside of unusual circumstances.

Register 32 bit COM DLL to 64 bit Windows 7

The problem is likely you try to register a 32-bit library with 64-bit version of regsvr32. See this KB article - you need to run regsvr32 from windows\SysWOW64 for 32-bit libraries.

How can I escape a double quote inside double quotes?

Add "\" before double quote to escape it, instead of \

#! /bin/csh -f

set dbtable = balabala

set dbload = "load data local infile "\""'gfpoint.csv'"\"" into table $dbtable FIELDS TERMINATED BY ',' ENCLOSED BY '"\""' LINES TERMINATED BY "\""'\n'"\"" IGNORE 1 LINES"

echo $dbload
# load data local infile "'gfpoint.csv'" into table balabala FIELDS TERMINATED BY ',' ENCLOSED BY '"' LINES TERMINATED BY "''" IGNORE 1 LINES

How to redirect stdout to both file and console with scripting?

from import Tee
from contextlib import closing

print('This is not in the output file.')        

with closing(Tee("outputfile.log", "w", channel="stdout")) as outputstream:
    print('This is written to the output file and the console.')
    # raise Exception('The file "outputfile.log" is closed anyway.')
print('This is not written to the output file.')   

# Output on console:
# This is not in the output file.
# This is written to the output file and the console.
# This is not written to the output file.

# Content of file outputfile.txt:
# This is written to the output file and the console.

The Tee class in does what you want, but it lacks the __enter__ and __exit__ methods needed to call it in the with-statement. Those are added by contextlib.closing.

How do I append one string to another in Python?

If you need to do many append operations to build a large string, you can use StringIO or cStringIO. The interface is like a file. ie: you write to append text to it.

If you're just appending two strings then just use +.

How to make a page redirect using JavaScript?

You can append the values in the query string for the next page to see and process. You can wrap them inside the link tags:

<a href="your_page.php?var1=value1&var2=value2">

You separate each of those values with the & sign.

Or you can create this on a button click like this:

<input type="button" onclick="document.location.href = 'your_page.php?var1=value1&var2=value2';">

Android, canvas: How do I clear (delete contents of) a canvas (= bitmaps), living in a surfaceView?

For me calling Canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR) or something similar would only work after I touch the screen. SO I would call the above line of code but the screen would only clear after I then touched the screen. So what worked for me was to call invalidate() followed by init() which is called at the time of creation to initialize the view.

private void init() {

    mPaint = new Paint();

    mCanvas = new Canvas();
    mPaths = new LinkedList<>();

} error in opening zip file

I faced the same problem. I had a zip archive which was not able to handle but WinRar unpacked it just fine. I found article on SDN about compressing and decompressing options in Java. I slightly modified one of example codes to produce method which was finally capable of handling the archive. Trick is in using ZipInputStream instead of ZipFile and in sequential reading of zip archive. This method is also capable of handling empty zip archive. I believe you can adjust the method to suit your needs as all zip classes have equivalent subclasses for .jar archives.

public void unzipFileIntoDirectory(File archive, File destinationDir) 
    throws Exception {
    final int BUFFER_SIZE = 1024;
    BufferedOutputStream dest = null;
    FileInputStream fis = new FileInputStream(archive);
    ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis));
    ZipEntry entry;
    File destFile;
    while ((entry = zis.getNextEntry()) != null) {
        destFile = FilesystemUtils.combineFileNames(destinationDir, entry.getName());
        if (entry.isDirectory()) {
        } else {
            int count;
            byte data[] = new byte[BUFFER_SIZE];
            FileOutputStream fos = new FileOutputStream(destFile);
            dest = new BufferedOutputStream(fos, BUFFER_SIZE);
            while ((count =, 0, BUFFER_SIZE)) != -1) {
                dest.write(data, 0, count);

scrollIntoView Scrolls just too far

Another solution is to use "offsetTop", like this:

var elementPosition = document.getElementById('id').offsetTop;

  top: elementPosition - 10, //add your necessary value
  behavior: "smooth"  //Smooth transition to roll

Owl Carousel, making custom navigation

You need to enable navigation and edit navigationText:

> Assuming this is version 1.3.2

Note: It appears the site for Owl 1.3 is now down, so here is a forked Codepen example.

  navigation: true,
  navigationText: ["<img src='myprevimage.png'>","<img src='mynextimage.png'>"]

> Assuming it's version 2:

  nav: true,
  navText: ["<img src='myprevimage.png'>","<img src='mynextimage.png'>"]

Personal suggestion: Use Slick over Owl

Personal suggestion update: Tiny slider is great too.

Select Multiple Fields from List in Linq

This is task for which anonymous types are very well suited. You can return objects of a type that is created automatically by the compiler, inferred from usage.

The syntax is of this form:

new { Property1 = value1, Property2 = value2, ... }

For your case, try something like the following:

var listObject = getData();
var catNames = listObject.Select(i =>
    new { CatName = i.category_name, Item1 = i.item1, Item2 = i.item2 })
    .Distinct().OrderByDescending(s => s).ToArray();

MySQL "incorrect string value" error when save unicode string in Django

If it's a new project, I'd just drop the database, and create a new one with a proper charset:


Utilizing multi core for tar+gzip/bzip compression/decompression

If you want to have more flexibility with filenames and compression options, you can use:

find /my/path/ -type f -name "*.sql" -o -name "*.log" -exec \
tar -P --transform='s@/my/path/@@g' -cf - {} + | \
pigz -9 -p 4 > myarchive.tar.gz

Step 1: find

find /my/path/ -type f -name "*.sql" -o -name "*.log" -exec

This command will look for the files you want to archive, in this case /my/path/*.sql and /my/path/*.log. Add as many -o -name "pattern" as you want.

-exec will execute the next command using the results of find: tar

Step 2: tar

tar -P --transform='s@/my/path/@@g' -cf - {} +

--transform is a simple string replacement parameter. It will strip the path of the files from the archive so the tarball's root becomes the current directory when extracting. Note that you can't use -C option to change directory as you'll lose benefits of find: all files of the directory would be included.

-P tells tar to use absolute paths, so it doesn't trigger the warning "Removing leading `/' from member names". Leading '/' with be removed by --transform anyway.

-cf - tells tar to use the tarball name we'll specify later

{} + uses everyfiles that find found previously

Step 3: pigz

pigz -9 -p 4

Use as many parameters as you want. In this case -9 is the compression level and -p 4 is the number of cores dedicated to compression. If you run this on a heavy loaded webserver, you probably don't want to use all available cores.

Step 4: archive name

> myarchive.tar.gz


Skipping Iterations in Python

For this specific use-case using try..except..else is the cleanest solution, the else clause will be executed if no exception was raised.

NOTE: The else clause must follow all except clauses

for i in iterator:
        # Do something.
        # Handle exception
        # Continue doing something

Git - What is the difference between push.default "matching" and "simple"

From GIT documentation: Git Docs

Below gives the full information. In short, simple will only push the current working branch and even then only if it also has the same name on the remote. This is a very good setting for beginners and will become the default in GIT 2.0

Whereas matching will push all branches locally that have the same name on the remote. (Without regard to your current working branch ). This means potentially many different branches will be pushed, including those that you might not even want to share.

In my personal usage, I generally use a different option: current which pushes the current working branch, (because I always branch for any changes). But for a beginner I'd suggest simple

Defines the action git push should take if no refspec is explicitly given. Different values are well-suited for specific workflows; for instance, in a purely central workflow (i.e. the fetch source is equal to the push destination), upstream is probably what you want. Possible values are:

nothing - do not push anything (error out) unless a refspec is explicitly given. This is primarily meant for people who want to avoid mistakes by always being explicit.

current - push the current branch to update a branch with the same name on the receiving end. Works in both central and non-central workflows.

upstream - push the current branch back to the branch whose changes are usually integrated into the current branch (which is called @{upstream}). This mode only makes sense if you are pushing to the same repository you would normally pull from (i.e. central workflow).

simple - in centralized workflow, work like upstream with an added safety to refuse to push if the upstream branch's name is different from the local one.

When pushing to a remote that is different from the remote you normally pull from, work as current. This is the safest option and is suited for beginners.

This mode will become the default in Git 2.0.

matching - push all branches having the same name on both ends. This makes the repository you are pushing to remember the set of branches that will be pushed out (e.g. if you always push maint and master there and no other branches, the repository you push to will have these two branches, and your local maint and master will be pushed there).

To use this mode effectively, you have to make sure all the branches you would push out are ready to be pushed out before running git push, as the whole point of this mode is to allow you to push all of the branches in one go. If you usually finish work on only one branch and push out the result, while other branches are unfinished, this mode is not for you. Also this mode is not suitable for pushing into a shared central repository, as other people may add new branches there, or update the tip of existing branches outside your control.

This is currently the default, but Git 2.0 will change the default to simple.

Set default value of an integer column SQLite

Use the SQLite keyword default


This link is useful:

Select Row number in postgres

SELECT tab.*,
    row_number() OVER () as rnum
  FROM tab;

Here's the relevant section in the docs.

P.S. This, in fact, fully matches the answer in the referenced question.

Redis: Show database size/size for keys

So my solution to my own problem: After playing around with redis-cli a bit longer I found out that DEBUG OBJECT <key> reveals something like the serializedlength of key, which was in fact something I was looking for...

For a whole database you need to aggregate all values for KEYS * which shouldn't be too difficult with a scripting language of your choice...

The bad thing is that doesn't really have a lot of information about DEBUG OBJECT.

Is it good practice to make the constructor throw an exception?

I've always considered throwing checked exceptions in the constructor to be bad practice, or at least something that should be avoided.

The reason for this is that you cannot do this :

private SomeObject foo = new SomeObject();

Instead you must do this :

private SomeObject foo;
public MyObject() {
    try {
        foo = new SomeObject()
    } Catch(PointlessCheckedException e) {
       throw new RuntimeException("ahhg",e);

At the point when I'm constructing SomeObject I know what it's parameters are so why should I be expected to wrap it in a try catch? Ahh you say but if I'm constructing an object from dynamic parameters I don't know if they're valid or not. Well, you could... validate the parameters before passing them to the constructor. That would be good practice. And if all you're concerned about is whether the parameters are valid then you can use IllegalArgumentException.

So instead of throwing checked exceptions just do

public SomeObject(final String param) {
    if (param==null) throw new NullPointerException("please stop");
    if (param.length()==0) throw new IllegalArgumentException("no really, please stop");

Of course there are cases where it might just be reasonable to throw a checked exception

public SomeObject() {
    if (todayIsWednesday) throw new YouKnowYouCannotDoThisOnAWednesday();

But how often is that likely?

Set value of input instead of sendKeys() - Selenium WebDriver nodejs

Try to set the element's value using the executeScript method of JavascriptExecutor:

WebDriver driver = new FirefoxDriver();
JavascriptExecutor jse = (JavascriptExecutor)driver;
jse.executeScript("document.getElementById('elementID').setAttribute('value', 'new value for element')");

How to read a single char from the console in Java (as the user types it)?

You need to knock your console into raw mode. There is no built-in platform-independent way of getting there. jCurses might be interesting, though.

On a Unix system, this might work:

String[] cmd = {"/bin/sh", "-c", "stty raw </dev/tty"};

For example, if you want to take into account the time between keystrokes, here's sample code to get there.

Converting from a string to boolean in Python?

This is the version I wrote. Combines several of the other solutions into one.

def to_bool(value):
    Converts 'something' to boolean. Raises exception if it gets a string it doesn't handle.
    Case is ignored for strings. These string values are handled:
      True: 'True', "1", "TRue", "yes", "y", "t"
      False: "", "0", "faLse", "no", "n", "f"
    Non-string values are passed to bool.
    if type(value) == type(''):
        if value.lower() in ("yes", "y", "true",  "t", "1"):
            return True
        if value.lower() in ("no",  "n", "false", "f", "0", ""):
            return False
        raise Exception('Invalid value for boolean conversion: ' + value)
    return bool(value)

If it gets a string it expects specific values, otherwise raises an Exception. If it doesn't get a string, just lets the bool constructor figure it out. Tested these cases:

test_cases = [
    ('true', True),
    ('t', True),
    ('yes', True),
    ('y', True),
    ('1', True),
    ('false', False),
    ('f', False),
    ('no', False),
    ('n', False),
    ('0', False),
    ('', False),
    (1, True),
    (0, False),
    (1.0, True),
    (0.0, False),
    ([], False),
    ({}, False),
    ((), False),
    ([1], True),
    ({1:2}, True),
    ((1,), True),
    (None, False),
    (object(), True),

What is the purpose of backbone.js?

Is an MVC design pattern on the client side, believe me.. It's gonna save you tons of code, not to mention a more clean and clear code, a more easy to maintain code. Could be a little tricky at first, but believe me it's a great library.

What is the difference between int, Int16, Int32 and Int64?

Each type of integer has a different range of storage capacity

   Type      Capacity

   Int16 -- (-32,768 to +32,767)

   Int32 -- (-2,147,483,648 to +2,147,483,647)

   Int64 -- (-9,223,372,036,854,775,808 to +9,223,372,036,854,775,807)

As stated by James Sutherland in his answer:

int and Int32 are indeed synonymous; int will be a little more familiar looking, Int32 makes the 32-bitness more explicit to those reading your code. I would be inclined to use int where I just need 'an integer', Int32 where the size is important (cryptographic code, structures) so future maintainers will know it's safe to enlarge an int if appropriate, but should take care changing Int32 variables in the same way.

The resulting code will be identical: the difference is purely one of readability or code appearance.

How do I remove the space between inline/inline-block elements?

I found a pure CSS solution that worked for me very well in all browsers:

span {
    display: table-cell;

Best way to display data via JSON using jQuery

JQuery has an inbuilt json data type for Ajax and converts the data into a object. PHP% also has inbuilt json_encode function which converts an array into json formatted string. Saves a lot of parsing, decoding effort.

Disable and enable buttons in C#

Change this

button2.Enabled == true


button2.Enabled = true;

How to show Snackbar when Activity starts?

You can also define a super class for all your activities and find the view once in the parent activity.

for example :

public class AppActivity extends AppCompatActivity {

    protected View content;

    protected void onCreate(@Nullable Bundle savedInstanceState) {
        content = findViewById(;

and your snacks would look like this in every activity in your app:

Snackbar.make(content, "hello every body", Snackbar.LENGTH_SHORT).show();

It is better for performance you have to find the view once for every activity.

How do I handle a click anywhere in the page, even when a certain element stops the propagation?

If you make sure that this is the first event handler work, something like this might do the trick:

$('*').click(function(event) {
    if (this === { // only fire this handler on the original element

Note that, if you have lots of elements in your page, this will be Really Very Slow, and it won't work for anything added dynamically.

How to save Excel Workbook to Desktop regardless of user?

Not sure if this is still relevant, but I use this way

Public bEnableEvents As Boolean
Public bclickok As Boolean
Public booRestoreErrorChecking As Boolean   'put this at the top of the module

 Private Declare Function apiGetComputerName Lib "kernel32" Alias _
"GetComputerNameA" (ByVal lpBuffer As String, nSize As Long) As Long
Private Declare Function apiGetUserName Lib "advapi32.dll" Alias _
"GetUserNameA" (ByVal lpBuffer As String, nSize As Long) As Long

Function GetUserID() As String
' Returns the network login name
On Error Resume Next
Dim lngLen As Long, lngX As Long
Dim strUserName As String
strUserName = String$(254, 0)
lngLen = 255
lngX = apiGetUserName(strUserName, lngLen)
If lngX <> 0 Then
    GetUserID = Left$(strUserName, lngLen - 1)
    GetUserID = ""
End If
Exit Function
End Function

This next bit I save file as PDF, but can change to suit

Public Sub SaveToDesktop()
Dim LoginName As String
LoginName = UCase(GetUserID)

ChDir "C:\Users\" & LoginName & "\Desktop\"
Debug.Print LoginName
ActiveSheet.ExportAsFixedFormat Type:=xlTypePDF, Filename:= _
    "C:\Users\" & LoginName & "\Desktop\MyFileName.pdf", Quality:=xlQualityStandard, _
    IncludeDocProperties:=True, IgnorePrintAreas:=False, OpenAfterPublish:= _
End Sub

How can I access Oracle from Python?

Here's what worked for me. My Python and Oracle versions are slightly different from yours, but the same approach should apply. Just make sure the cx_Oracle binary installer version matches your Oracle client and Python versions.

My versions:

  • Python 2.7
  • Oracle Instant Client 11G R2
  • cx_Oracle 5.0.4 (Unicode, Python 2.7, Oracle 11G)
  • Windows XP SP3


  1. Download the Oracle Instant Client package. I used Unzip it to C:\your\path\to\instantclient_11_2
  2. Download and run the cx_Oracle binary installer. I used cx_Oracle-5.0.4-11g-unicode.win32-py2.7.msi. I installed it for all users and pointed it to the Python 2.7 location it found in the registry.
  3. Set the ORACLE_HOME and PATH environment variables via a batch script or whatever mechanism makes sense in your app context, so that they point to the Oracle Instant Client directory. See oracle_python.bat source below. I'm sure there must be a more elegant solution for this, but I wanted to limit my system-wide changes as much as possible. Make sure you put the targeted Oracle Instant Client directory at the beginning of the PATH (or at least ahead of any other Oracle client directories). Right now, I'm only doing command-line stuff so I just run oracle_python.bat in the shell before running any programs that require cx_Oracle.
  4. Run regedit and check to see if there's an NLS_LANG key set at \HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE. If so, rename the key (I changed it to NLS_LANG_OLD) or unset it. This key should only be used as the default NLS_LANG value for Oracle 7 client, so it's safe to remove it unless you happen to be using Oracle 7 client somewhere else. As always, be sure to backup your registry before making changes.
  5. Now, you should be able to import cx_Oracle in your Python program. See the source below. Note that I had to set the connection and SQL strings to Unicode for my version of cx_Oracle.

Source: oracle_python.bat

@echo off
set ORACLE_HOME=C:\your\path\to\instantclient_11_2


import cx_Oracle

conn_str = u'user/password@host:port/service'
conn = cx_Oracle.connect(conn_str)
c = conn.cursor()
c.execute(u'select your_col_1, your_col_2 from your_table')
for row in c:
    print row[0], "-", row[1]

Possible Issues:

  • "ORA-12705: Cannot access NLS data files or invalid environment specified" - I ran into this before I made the NLS_LANG registry change.
  • "TypeError: argument 1 must be unicode, not str" - if you need to set the connection string to Unicode.
  • "TypeError: expecting None or a string" - if you need to set the SQL string to Unicode.
  • "ImportError: DLL load failed: The specified procedure could not be found." - may indicate that cx_Oracle can't find the appropriate Oracle client DLL.

How to get domain URL and application name?

The application name come from getContextPath.

I find this graphic from Agile Software Craftsmanship HttpServletRequest Path Decoding sorts out all the different methods that are available:

enter image description here

Getting a POST variable

In addition to using Request.Form and Request.QueryString and depending on your specific scenario, it may also be useful to check the Page's IsPostBack property.

if (Page.IsPostBack)
  // HTTP Post
  // HTTP Get

jQuery hover and class selector

On a side note this is more efficient:

$(".menuItem").hover(function(){ = "#F00";
}, function() { = "#000";

Which .NET Dependency Injection frameworks are worth looking into?

I use Simple Injector:

Simple Injector is an easy, flexible and fast dependency injection library that uses best practice to guide your solutions toward the pit of success.

How to remove the first Item from a list?

You can use list.reverse() to reverse the list, then list.pop() to remove the last element, for example:

l = [0, 1, 2, 3, 4]
print l
[4, 3, 2, 1, 0]


How to set HTML5 required attribute in Javascript?

Short version

element.setAttribute("required", "");    //turns required on
element.required = true;                 //turns required on through reflected attribute
jQuery(element).attr('required', '');    //turns required on
$("#elementId").attr('required', '');    //turns required on

element.removeAttribute("required");     //turns required off
element.required = false;                //turns required off through reflected attribute
jQuery(element).removeAttr('required');  //turns required off
$("#elementId").removeAttr('required');  //turns required off

if (edName.hasAttribute("required")) { }  //check if required
if (edName.required) { }                 //check if required using reflected attribute

Long Version

Once T.J. Crowder managed to point out reflected properties, i learned that following syntax is wrong:

element.attributes["name"] = value; //bad! Overwrites the HtmlAttribute object = value;    //bad! Overwrites the HtmlAttribute object
value =;    //bad! Returns the HtmlAttribute object, not its value
value = element.attributes["name"]; //bad! Returns the HtmlAttribute object, not its value

You must go through element.getAttribute and element.setAttribute:

element.getAttribute("foo");         //correct
element.setAttribute("foo", "test"); //correct

This is because the attribute actually contains a special HtmlAttribute object:

element.attributes["foo"];           //returns HtmlAttribute object, not the value of the attribute;              //returns HtmlAttribute object, not the value of the attribute

By setting an attribute value to "true", you are mistakenly setting it to a String object, rather than the HtmlAttribute object it requires:

element.attributes["foo"] = "true";  //error because "true" is not a HtmlAttribute object
element.setAttribute("foo", "true"); //error because "true" is not an HtmlAttribute object

Conceptually the correct idea (expressed in a typed language), is:

HtmlAttribute attribute = new HtmlAttribute();
attribute.value = "";
element.attributes["required"] = attribute;

This is why:

  • getAttribute(name)
  • setAttribute(name, value)

exist. They do the work on assigning the value to the HtmlAttribute object inside.

On top of this, some attribute are reflected. This means that you can access them more nicely from Javascript:

//Set the required attribute
//element.setAttribute("required", ""); 
element.required = true;

//Check the attribute
//if (element.getAttribute("required")) {...}
if (element.required) {...}

//Remove the required attribute
element.required = false;

What you don't want to do is mistakenly use the .attributes collection:

element.attributes.required = true;     //WRONG!
if (element.attributes.required) {...}  //WRONG!
element.attributes.required = false;    //WRONG!

Testing Cases

This led to testing around the use of a required attribute, comparing the values returned through the attribute, and the reflected property


with results:

HTML                         .required        .getAttribute("required")
==========================   ===============  =========================
<input>                      false (Boolean)  null (Object)
<input required>             true  (Boolean)  "" (String)
<input required="">          true  (Boolean)  "" (String)
<input required="required">  true  (Boolean)  "required" (String)
<input required="true">      true  (Boolean)  "true" (String)
<input required="false">     true  (Boolean)  "false" (String)
<input required="0">         true  (Boolean)  "0" (String)

Trying to access the .attributes collection directly is wrong. It returns the object that represents the DOM attribute:

edName.attributes["required"] => [object Attr]
edName.attributes.required    => [object Attr]

This explains why you should never talk to the .attributes collect directly. You're not manipulating the values of the attributes, but the objects that represent the attributes themselves.

How to set required?

What's the correct way to set required on an attribute? You have two choices, either the reflected property, or through correctly setting the attribute:

element.setAttribute("required", "");         //Correct
edName.required = true;                       //Correct

Strictly speaking, any other value will "set" the attribute. But the definition of Boolean attributes dictate that it should only be set to the empty string "" to indicate true. The following methods all work to set the required Boolean attribute,

but do not use them:

element.setAttribute("required", "required"); //valid, but not preferred
element.setAttribute("required", "foo");      //works, but silly
element.setAttribute("required", "true");     //Works, but don't do it, because:
element.setAttribute("required", "false");    //also sets required boolean to true
element.setAttribute("required", false);      //also sets required boolean to true
element.setAttribute("required", 0);          //also sets required boolean to true

We already learned that trying to set the attribute directly is wrong:

edName.attributes["required"] = true;       //wrong
edName.attributes["required"] = "";         //wrong
edName.attributes["required"] = "required"; //wrong
edName.attributes.required = true;          //wrong
edName.attributes.required = "";            //wrong
edName.attributes.required = "required";    //wrong

How to clear required?

The trick when trying to remove the required attribute is that it's easy to accidentally turn it on:

edName.removeAttribute("required");     //Correct
edName.required = false;                //Correct

With the invalid ways:

edName.setAttribute("required", null);    //WRONG! Actually turns required on!
edName.setAttribute("required", "");      //WRONG! Actually turns required on!
edName.setAttribute("required", "false"); //WRONG! Actually turns required on!
edName.setAttribute("required", false);   //WRONG! Actually turns required on!
edName.setAttribute("required", 0);       //WRONG! Actually turns required on!

When using the reflected .required property, you can also use any "falsey" values to turn it off, and truthy values to turn it on. But just stick to true and false for clarity.

How to check for required?

Check for the presence of the attribute through the .hasAttribute("required") method:

if (edName.hasAttribute("required"))

You can also check it through the Boolean reflected .required property:

if (edName.required)

Cannot read property 'push' of undefined when combining arrays

In most cases you have to initialize the array,

let list: number[] = [];

Get absolute path to workspace directory in Jenkins Pipeline plugin

Since version 2.5 of the Pipeline Nodes and Processes Plugin (a component of the Pipeline plugin, installed by default), the WORKSPACE environment variable is available again. This version was released on 2016-09-23, so it should be available on all up-to-date Jenkins instances.


    // now you are on slave labeled with 'label'
    def workspace = WORKSPACE
    // ${workspace} will now contain an absolute path to job workspace on slave

    workspace = env.WORKSPACE
    // ${workspace} will still contain an absolute path to job workspace on slave

    // When using a GString at least later Jenkins versions could only handle the env.WORKSPACE variant:
    echo "Current workspace is ${env.WORKSPACE}"

    // the current Jenkins instances will support the short syntax, too:
    echo "Current workspace is $WORKSPACE"


ADB not recognising Nexus 4 under Windows 7

How to do it on Windows 8 (I think, it will work for Windows 7 too)

  1. Open Android SDK Manager and delete Google Usb Driver
  2. Open Control Panel -> Devices Manager -> Find your Nexus -> right click -> delete device
  3. Unplug your device
  4. Open Android SDK Manager and install Google Usb Driver
  5. Connect your device
  6. Open Control Panel -> Devices Manager -> Find your Nexus -> right click -> update drivers -> Manual update -> open android-sdk folder (enable checkbox for subfolders) -> install driver from Google Inc
  7. adb kill-server; adb start-server; adb devices should show your nexus

Do not forget, that Android 4.2 now want you to submit RSA key from your computer, look at your device screen.

To enable developers options on Android 4.2: Open Settings -> About phone -> Tap on Build Number 7 times.

Convert absolute path into relative path given a current directory using Bash

It is built in to Perl since 2001, so it works on nearly every system you can imagine, even VMS.

perl -e 'use File::Spec; print File::Spec->abs2rel(@ARGV) . "\n"' FILE BASE

Also, the solution is easy to understand.

So for your example:

perl -e 'use File::Spec; print File::Spec->abs2rel(@ARGV) . "\n"' $absolute $current

...would work fine.

How to parse XML using vba

You can use a XPath Query:

Dim objDom As Object        '// DOMDocument
Dim xmlStr As String, _
    xPath As String

xmlStr = _
    "<PointN xsi:type='typens:PointN' " & _
    "xmlns:xsi='' " & _
    "xmlns:xs=''> " & _
    "    <X>24.365</X> " & _
    "    <Y>78.63</Y> " & _

Set objDom = CreateObject("Msxml2.DOMDocument.3.0")     '// Using MSXML 3.0

'/* Load XML */
objDom.LoadXML xmlStr

' * XPath Query
' */        

'/* Get X */
xPath = "/PointN/X"
Debug.Print objDom.SelectSingleNode(xPath).text

'/* Get Y */
xPath = "/PointN/Y"
Debug.Print objDom.SelectSingleNode(xPath).text

Download history stock prices automatically from yahoo finance in python

It's trivial when you know how:

import yfinance as yf
df ='CVS', '2015-01-01')

If you wish to plot it:

import finplot as fplt

enter image description here

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

To check for DIRECTORIES you should not use something like:

if exist c:\windows\

To work properly use:

if exist c:\windows\\.

note the "." at the end.

How to convert a string to an integer in JavaScript?

To convert a String into Integer, I recommend using parseFloat and NOT parseInt. Here's why:

Using parseFloat:

parseFloat('2.34cms')  //Output: 2.34
parseFloat('12.5')     //Output: 12.5
parseFloat('012.3')    //Output: 12.3

Using parseInt:

parseInt('2.34cms')  //Output: 2
parseInt('12.5')     //Output: 12
parseInt('012.3')    //Output: 12

So if you have noticed parseInt discards the values after the decimals, whereas parseFloat lets you work with floating point numbers and hence more suitable if you want to retain the values after decimals. Use parseInt if and only if you are sure that you want the integer value.

How to execute cmd commands via Java

As i also faced the same problem and because some people here commented that the solution wasn't working for them, here's the link to the post where a working solution has been found.

Also see the "Update" in the best answer for using Cygwin terminal

Can you "compile" PHP code and upload a binary-ish file, which will just be run by the byte code interpreter?

There is also

which aims

  • To encode entire script in a proprietary PHP application
  • To encode some classes and/or functions in a proprietary PHP application
  • To enable the production of php-gtk applications that could be used on client desktops, without the need for a php.exe.
  • To do the feasibility study for a PHP to C converter

The extension is available from PECL.

iOS 8 Snapshotting a view that has not been rendered results in an empty snapshot

I got the same bug,getting bellow message in console while opening camera.

'Snapshotting a view that has not been rendered results in an empty snapshot. Ensure your view has been rendered at least once before snapshotting or snapshot after screen updates.'

For me problem was with the Bundle display name in Info.plist was empty some how,i put my app name there and now it working fine.i did't received any camera permission alert because of empty Bundle display blocked the view from rendering.

the problem was't with view but by presenting it without a can check it on settings-->privacy-->Camera,if your app not listed there problem might be same.

Replacement for "rename" in dplyr

The next version of dplyr will support an improved version of select that also incorporates renaming:

> mtcars2 <- select( mtcars, disp2 = disp )
> head( mtcars2 )
Mazda RX4         160
Mazda RX4 Wag     160
Datsun 710        108
Hornet 4 Drive    258
Hornet Sportabout 360
Valiant           225
> changes( mtcars, mtcars2 )
Changed variables:
      old         new
disp  0x105500400
disp2             0x105500400

Changed attributes:
      old         new
names 0x106d2cf50 0x106d28a98

What special characters must be escaped in regular expressions?

Which characters you must and which you mustn't escape indeed depends on the regex flavor you're working with.

For PCRE, and most other so-called Perl-compatible flavors, escape these outside character classes:


and these inside character classes:


For POSIX extended regexes (ERE), escape these outside character classes (same as PCRE):


Escaping any other characters is an error with POSIX ERE.

Inside character classes, the backslash is a literal character in POSIX regular expressions. You cannot use it to escape anything. You have to use "clever placement" if you want to include character class metacharacters as literals. Put the ^ anywhere except at the start, the ] at the start, and the - at the start or the end of the character class to match these literally, e.g.:


In POSIX basic regular expressions (BRE), these are metacharacters that you need to escape to suppress their meaning:


Escaping parentheses and curly brackets in BREs gives them the special meaning their unescaped versions have in EREs. Some implementations (e.g. GNU) also give special meaning to other characters when escaped, such as \? and +. Escaping a character other than .^$*(){} is normally an error with BREs.

Inside character classes, BREs follow the same rule as EREs.

If all this makes your head spin, grab a copy of RegexBuddy. On the Create tab, click Insert Token, and then Literal. RegexBuddy will add escapes as needed.

What does $_ mean in PowerShell?

According to this website, it's a reference to this, mostly in loops.

$_ (dollar underscore) 'THIS' token. Typically refers to the item inside a foreach loop. Task: Print all items in a collection. Solution. ... | foreach { Write-Host $_ }

Redirect echo output in shell script to logfile

You can add this line on top of your script:

# redirect stdout/stderr to a file
exec &> logfile.txt

OR else to redirect only stdout use:

exec > logfile.txt

Javascript checkbox onChange

The following solution makes use of jquery. Let's assume you have a checkbox with id of checkboxId.

const checkbox = $("#checkboxId");

checkbox.change(function(event) {
    var checkbox =;
    if (checkbox.checked) {
        //Checkbox has been checked
    } else {
        //Checkbox has been unchecked

Bold & Non-Bold Text In A Single UILabel?

Use the below code. I hope it help for you.

NSString *needToChangeStr=@"BOOK";
NSString *display_string=[NSString stringWithFormat:@"This is %@",book];

NSMutableAttributedString *attri_str=[[NSMutableAttributedString alloc]initWithString:display_string];

int begin=[display_string length]-[needToChangeStr length];
int end=[needToChangeStr length];

[attri_str addAttribute:NSFontAttributeName value:[UIFont fontWithName:@"HelveticaNeue-Bold" size:30] range:NSMakeRange(begin, end)];

Dialogs / AlertDialogs: How to "block execution" while dialog is up (.NET-style)


There are radical differences between mobile and desktop environment, as well as between the way in which applications were developed to a handful of years ago and today:

a) mobile devices need to conserve energy. Part of the value they offer. So you need to save resources. Threads are an expensive resource. Halt the progress of a thread is an unacceptable waste of this resource.

b) Nowadays the user is much more demanding. To assist them, we believe that it deserves to have full working CPU and the smallest possible expenditure of energy. Its application is not alone on the device, there is an unknow number of another apps running at same time and your app is not necessarily the most urgent.

c) system-level locks are not an option: a mobile device works with a number of events and services in the background and it is not right for any of them can be locked by an application.

Think about the user receiving a phone call while your "system lock" is working...

Based on the above facts, the answer to the proposed question are:

  • There is a viable way to build a dialog that blocks the main thread until a response from the user?

No. Workarounds do user experience get worse and it may make the mistake of blaming the system itself. This is unfair and penalizes the platform and all its developers.

  • Is there a way to block the entire system with a dialogue?

No. This is strictly forbidden on the platform. No application can interfere with the operation of the system or other applications.

  • I need to refactor my application, or rethink my way of programming to suit me on the Android mobile system architecture.

Yes. Including this aspect.

How do I find the install time and date of Windows?

Very simple way from PowerShell:

(Get-CimInstance -Class Win32_OperatingSystem).InstallDate

Extracted from:

golang why don't we have a set datastructure

One reason is that it is easy to create a set from map:

s := map[int]bool{5: true, 2: true}
_, ok := s[6] // check for existence
s[8] = true // add element 
delete(s, 2) // remove element


s_union := map[int]bool{}
for k, _ := range s1{
    s_union[k] = true
for k, _ := range s2{
    s_union[k] = true


s_intersection := map[int]bool{}
for k,_ := range s1 { 
  if s2[k] {
    s_intersection[k] = true

It is not really that hard to implement all other set operations.

How to list all dates between two dates

Create a stored procedure that does something like the following:

declare @startDate date;
declare @endDate date;

select @startDate = '20150528';
select @endDate = '20150531';

with dateRange as
  select dt = dateadd(dd, 1, @startDate)
  where dateadd(dd, 1, @startDate) < @endDate
  union all
  select dateadd(dd, 1, dt)
  from dateRange
  where dateadd(dd, 1, dt) < @endDate
select *
from dateRange

SQL Fiddle with demo.

Or better still create a calendar table and just select from that.

How to read a file without newlines?

another example:

Reading file one row at the time. Removing unwanted chars with from end of the string str.rstrip(chars)

with open(filename, 'r') as fileobj:
    for row in fileobj:
        print( row.rstrip('\n') )

see also str.strip([chars]) and str.lstrip([chars])

(python >= 2.0)

Permission denied error on Github Push

In could able to resolve this issue with giving username and password in below url.

Please replace username and password with your Github credentials:

git remote set-url origin https://<username>:<password><username>/FirstRepository.git

Detect if a browser in a mobile device (iOS/Android phone/tablet) is used

Don't detect mobile devices, go for stationary ones instead.

Nowadays (2016) there is a way to detect dots per inch/cm/px that seems to work in most modern browsers (see I needed a method to distinguish between a relatively small screen, orientation didn't matter, and a stationary computer monitor.

Because many mobile browsers don't support this, one can write the general css code for all cases and use this exception for large screens:

@media (max-resolution: 1dppx) {
    /* ... */

Both Windows XP and 7 have the default setting of 1 dot per pixel (or 96dpi). I don't know about other operating systems, but this works really well for my needs.

Edit: dppx doesn't seem to work in Internet Explorer.. use (96)dpi instead.

jQuery - Dynamically Create Button and Attach Event Handler

Your problem is that you're converting the button into an HTML snippet when you add it to the table, but that snippet is not the same object as the one that has the click handler on it.

$("#myButton").click(function () {
    var test = $('<button>Test</button>').click(function () {

    $("#nodeAttributeHeader").css('display', 'table-row'); // NB: changed

    var tr = $('<tr>').insertBefore('#addNodeTable tr:last');
    var td = $('<td>').append(test).appendTo(tr);

Remove the newline character in a list read from a file

Here are various optimisations and applications of proper Python style to make your code a lot neater. I've put in some optional code using the csv module, which is more desirable than parsing it manually. I've also put in a bit of namedtuple goodness, but I don't use the attributes that then provides. Names of the parts of the namedtuple are inaccurate, you'll need to correct them.

import csv
from collections import namedtuple
from time import localtime, strftime

# Method one, reading the file into lists manually (less desirable)
with open('grades.dat') as files:
    grades = [[e.strip() for e in s.split(',')] for s in files]

# Method two, using csv and namedtuple
StudentRecord = namedtuple('StudentRecord', 'id, lastname, firstname, something, homework1, homework2, homework3, homework4, homework5, homework6, homework7, exam1, exam2, exam3')
grades = map(StudentRecord._make, csv.reader(open('grades.dat')))
# Now you could have, student.lastname, etc.
# Skipping the namedtuple, you could do grades = map(tuple, csv.reader(open('grades.dat')))

request = open('requests.dat', 'w')
cont = 'y'

while cont.lower() == 'y':
    answer = raw_input('Please enter the Student I.D. of whom you are looking: ')
    for student in grades:
        if answer == student[0]:
            print '%s, %s      %s      %s' % (student[1], student[2], student[0], student[3])
            time = strftime('%a, %b %d %Y %H:%M:%S', localtime())
            print time
            print 'Exams - %s, %s, %s' % student[11:14]
            print 'Homework - %s, %s, %s, %s, %s, %s, %s' % student[4:11]
            total = sum(int(x) for x in student[4:14])
            print 'Total points earned - %d' % total
            grade = total / 5.5
            if grade >= 90:
                letter = 'an A'
            elif grade >= 80:
                letter = 'a B'
            elif grade >= 70:
                letter = 'a C'
            elif grade >= 60:
                letter = 'a D'
                letter = 'an F'

            if letter = 'an A':
                print 'Grade: %s, that is equal to %s.' % (grade, letter)
                print 'Grade: %.2f, that is equal to %s.' % (grade, letter)

            request.write('%s %s, %s %s\n' % (student[0], student[1], student[2], time))

    cont = raw_input('Would you like to search again? ')

print 'Goodbye.'

Trigger validation of all fields in Angular Form submit

Note: I know this is a hack, but it was useful for Angular 1.2 and earlier that didn't provide a simple mechanism.

The validation kicks in on the change event, so some things like changing the values programmatically won't trigger it. But triggering the change event will trigger the validation. For example, with jQuery:

$('#formField1, #formField2').trigger('change');

How to set up Spark on Windows?

Steps to install Spark in local mode:

  1. Install Java 7 or later. To test java installation is complete, open command prompt type java and hit enter. If you receive a message 'Java' is not recognized as an internal or external command. You need to configure your environment variables, JAVA_HOME and PATH to point to the path of jdk.

  2. Download and install Scala.

    Set SCALA_HOME in Control Panel\System and Security\System goto "Adv System settings" and add %SCALA_HOME%\bin in PATH variable in environment variables.

  3. Install Python 2.6 or later from Python Download link.

  4. Download SBT. Install it and set SBT_HOME as an environment variable with value as <<SBT PATH>>.

  5. Download winutils.exe from HortonWorks repo or git repo. Since we don't have a local Hadoop installation on Windows we have to download winutils.exe and place it in a bin directory under a created Hadoop home directory. Set HADOOP_HOME = <<Hadoop home directory>> in environment variable.

  6. We will be using a pre-built Spark package, so choose a Spark pre-built package for Hadoop Spark download. Download and extract it.

    Set SPARK_HOME and add %SPARK_HOME%\bin in PATH variable in environment variables.

  7. Run command: spark-shell

  8. Open http://localhost:4040/ in a browser to see the SparkContext web UI.

C# : Converting Base Class to Child Class

In OOP, you can't cast an instance of a parent class into a child class. You can only cast a child instance into a parent that it inherits from.

Angular2 Material Dialog css, dialog size

You can inspect the dialog element with dev tools and see what classes are applied on mdDialog.

For example, .md-dialog-container is the main classe of the MDDialog and has padding: 24px

you can create a custom CSS to overwrite whatever you want

.md-dialog-container {
      background-color: #000;
      width: 250px;
      height: 250px

In my opinion this is not a good option and probably goes against Material guide but since it doesn't have all features it has in it's previous version, you should do what you think is best for you.

Add Bootstrap Glyphicon to Input Box

You should be able to do this with existing bootstrap classes and a little custom styling.

    <div class="input-prepend">
        <span class="add-on">
            <i class="icon-user"></i>
        <input class="span2" id="prependedInput" type="text" placeholder="Username" style="background-color: #eeeeee;border-left: #eeeeee;">

Edit The icon is referenced via the icon-user class. This answer was written at the time of Bootstrap version 2. You can see the reference on the following page:

How to return a string value from a Bash function

The way you have it is the only way to do this without breaking scope. Bash doesn't have a concept of return types, just exit codes and file descriptors (stdin/out/err, etc)

How do I compare two DateTime objects in PHP 5.2.8?

You can also compare epoch seconds :

$d1->format('U') < $d2->format('U')

Source : (quite interesting article about DateTime)

How to force a html5 form validation without submitting it via jQuery

According to the question html5 validity should be validate able using jQuery at first and in most of the answer this is not happening and the reason for this is as following:

while validating using html5 form's default function

checkValidity();// returns true/false

we need to understand that jQuery returns object array, while selecting like this


therefore, you need to specify the first index to make checkValidity() function work


here is the complete solution:

<button type="button" name="button" onclick="saveData()">Save</button>

function saveData()
          type: "POST",
          url: "save.php",
          data: data,
          success: function(resp){console.log("Response: "+resp);}

How to compile without warnings being treated as errors?

Sure, find where -Werror is set and remove that flag. Then warnings will be only warnings.

How to change the type of a field?

db.coll.find().forEach(function(data) {

Open multiple Projects/Folders in Visual Studio Code

You can install the Open Folder Context Menus for VS Code extension from Chris Dias

  • Restart Visual Studio Code
  • Right click a folder and select "Open New Workbench Here"

Open New Workbench Here

converting a javascript string to a html object

You cannot do it with just method, unless you use some javascript framework like jquery which supports it ..

string s = '<div id="myDiv"></div>'
var htmlObject = $(s); // jquery call

but still, it would not be found by the getElementById because for that to work the element must be in the DOM... just creating in the memory does not insert it in the dom.

You would need to use append or appendTo or after etc.. to put it in the dom first..

Of'course all these can be done through regular javascript but it would take more steps to accomplish the same thing... and the logic is the same in both cases..

Removing space from dataframe columns in pandas

  • To remove white spaces:

1) To remove white space everywhere:

df.columns = df.columns.str.replace(' ', '')

2) To remove white space at the beginning of string:

df.columns = df.columns.str.lstrip()

3) To remove white space at the end of string:

df.columns = df.columns.str.rstrip()

4) To remove white space at both ends:

df.columns = df.columns.str.strip()
  • To replace white spaces with other characters (underscore for instance):

5) To replace white space everywhere

df.columns = df.columns.str.replace(' ', '_')

6) To replace white space at the beginning:

df.columns = df.columns.str.replace('^ +', '_')

7) To replace white space at the end:

df.columns = df.columns.str.replace(' +$', '_')

8) To replace white space at both ends:

df.columns = df.columns.str.replace('^ +| +$', '_')

All above applies to a specific column as well, assume you have a column named col, then just do:

df[col] = df[col].str.strip()  # or .replace as above

How to turn off Wifi via ADB?

The following method doesn't require root and should work anywhere (according to docs, even on Android Q+, if you keep targetSdkVersion = 28).

  1. Make a blank app.

  2. Create a ContentProvider:

    class ApiProvider : ContentProvider() {
        private val wifiManager: WifiManager? by lazy(LazyThreadSafetyMode.NONE) {
            requireContext().getSystemService(WIFI_SERVICE) as WifiManager?
        private fun requireContext() = checkNotNull(context)
        private val matcher = UriMatcher(UriMatcher.NO_MATCH).apply {
            addURI("wifi", "enable", 0)
            addURI("wifi", "disable", 1)
        override fun query(uri: Uri, projection: Array<out String>?, selection: String?, selectionArgs: Array<out String>?, sortOrder: String?): Cursor? {
            when (matcher.match(uri)) {
                0 -> {
                    withClearCallingIdentity {
                        wifiManager?.isWifiEnabled = true
                1 -> {
                    withClearCallingIdentity {
                        wifiManager?.isWifiEnabled = false
            return null
        private fun enforceAdb() {
            val callingUid = Binder.getCallingUid()
            if (callingUid != 2000 && callingUid != 0) {
                throw SecurityException("Only shell or root allowed.")
        private inline fun <T> withClearCallingIdentity(block: () -> T): T {
            val token = Binder.clearCallingIdentity()
            try {
                return block()
            } finally {
        override fun onCreate(): Boolean = true
        override fun insert(uri: Uri, values: ContentValues?): Uri? = null
        override fun update(uri: Uri, values: ContentValues?, selection: String?, selectionArgs: Array<out String>?): Int = 0
        override fun delete(uri: Uri, selection: String?, selectionArgs: Array<out String>?): Int = 0
        override fun getType(uri: Uri): String? = null
  3. Declare it in AndroidManifest.xml along with necessary permission:

    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
            android:exported="true" />
  4. Build the app and install it.

  5. Call from ADB:

    adb shell content query --uri content://wifi/enable
    adb shell content query --uri content://wifi/disable
  6. Make a batch script/shell function/shell alias with a short name that calls these commands.

Depending on your device you may need additional permissions.

css background image in a different folder from css

you can use this

body{ background-image: url('../img/bg.png'); }

I tried this on my project where I need to set the background image of a div so I used this and it worked!

How to fix "unable to write 'random state' " in openssl

Or this in windows powershell


Python - round up to the nearest ten

Here is one way to do it:

>>> n = 46
>>> (n + 9) // 10 * 10

Get the position of a div/span tag

For anyone needing just top or left position, slight modifications to @Nickf's readable code does the trick.

function getTopPos(el) {
    for (var topPos = 0;
        el != null;
        topPos += el.offsetTop, el = el.offsetParent);
    return topPos;


function getLeftPos(el) {
    for (var leftPos = 0;
        el != null;
        leftPos += el.offsetLeft, el = el.offsetParent);
    return leftPos;

In Ruby, how do I skip a loop in a .each loop, similar to 'continue'

Use next:

(1..10).each do |a|
  next if a.even?
  puts a



For additional coolness check out also redo and retry.

Works also for friends like times, upto, downto, each_with_index, select, map and other iterators (and more generally blocks).

For more info see

How to modify STYLE attribute of element with known ID using JQuery

Use the CSS function from jQuery to set styles to your items :

$('#buttonId').css({ "background-color": 'brown'});

In Python, how do you convert a `datetime` object to seconds?

Starting from Python 3.3 this becomes super easy with the datetime.timestamp() method. This of course will only be useful if you need the number of seconds from 1970-01-01 UTC.

from datetime import datetime
dt =  # Get timezone naive now
seconds = dt.timestamp()

The return value will be a float representing even fractions of a second. If the datetime is timezone naive (as in the example above), it will be assumed that the datetime object represents the local time, i.e. It will be the number of seconds from current time at your location to 1970-01-01 UTC.

How to style child components from parent component's CSS file?

You should not write CSS rules for a child component elements in a parent component, since an Angular component is a self-contained entity which should explicitly declare what is available for the outside world. If child layout changes in the future, your styles for that child component elements scattered across other components' SCSS files could easily break, thus making your styling very fragile. That's what ViewEncapsulation is for in the case of CSS. Otherwise, it would be the same if you could assign values to private fields of some class from any other class in Object Oriented Programming.

Therefore, what you should do is to define a set of classes you could apply to the child host element and implement how the child responds to them.

Technically, it could be done as follows:

// child.component.html:
<span class="label-1"></span>

// child.component.scss:
:host.child-color-black {
    .label-1 {
        color: black;

:host.child-color-blue {
    .label-1 {
        color: blue ;

// parent.component.html:
<child class="child-color-black"></child>
<child class="child-color-blue"></child>

In other words, you use :host pseudo-selector provided by Angular + set of CSS classes to define possible child styles in child component itself. You then have the ability to trigger those styles from outside by applying pre-defined classes to the <child> host element.

Garbage collector in Android

I would say no, because the Developer docs on RAM usage state:


An explicit GC, such as when you call gc() (which you should avoid calling and instead trust the GC to run when needed).


I've highlighted the relevant part in bold.

Have a look at the YouTube series, Android Performance Patterns - it will show you tips on managing your app's memory usage (such as using Android's ArrayMaps and SparseArrays instead of HashMaps).

How to use group by with union in t-sql

You need to alias the subquery. Thus, your statement should be:

From    (
        Select id, time
        From dbo.tablea
        Union All
        Select id, time
        From dbo.tableb
        ) As Z
Group By

mingw-w64 threads: posix vs win32

Note that it is now possible to use some of C++11 std::thread in the win32 threading mode. These header-only adapters worked out of the box for me:

From the revision history it looks like there is some recent attempt to make this a part of the mingw64 runtime.

Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

mAddTaskButton is null because you never initialize it with:

mAddTaskButton = (Button) findViewById(;

before you call mAddTaskButton.setOnClickListener().

Do I need <class> elements in persistence.xml?

Not sure if you're doing something similar to what I am doing, but Im generating a load of source java from an XSD using JAXB in a seperate component using Maven. Lets say this artifact is called "base-model"

I wanted to import this artifact containing the java source and run hibernate over all classes in my "base-model" artifact jar and not specify each explicitly. Im adding "base-model" as a dependency for my hibernate component but the trouble is the tag in persistence.xml only allows you to specify absolute paths.

The way I got round it is to copy my "base-model" jar dependency explictly to my target dir and also strip the version of it. So whereas if I build my "base-model" artifact it generate "base-model-1.0-SNAPSHOT.jar", the copy-resources step copies it as "base-model.jar".

So in your pom for the hibernate component:

            <!-- We want to copy across all our artifacts containing java code
        generated from our scheams. We copy them across and strip the version
        so that our persistence.xml can reference them directly in the tag
        <jar-file>target/dependency/${artifactId}.jar</jar-file> -->

Then I call the hibernate plugin in the next phase "process-classes":

            <!-- Generate the schema DDL -->


and finally in my persistence.xml I can explicitly set the location of the jar thus:


and add the property:

<property name="hibernate.archive.autodetection" value="class, hbm"/>

How to put a symbol above another in LaTeX?

Use \overset{above}{main} in math mode. In your case, \overset{a}{\#}.

How do I print my Java object without getting "SomeType@2f92e0f4"?


All Java objects have a toString() method, which is invoked when you try to print the object.

System.out.println(myObject);  // invokes myObject.toString()

This method is defined in the Object class (the superclass of all Java objects). The Object.toString() method returns a fairly ugly looking string, composed of the name of the class, an @ symbol and the hashcode of the object in hexadecimal. The code for this looks like:

// Code of Object.toString()
public String toString() {
    return getClass().getName() + "@" + Integer.toHexString(hashCode());

A result such as can therefore be explained as:

  • - the name of the class, i.e. the class is MyType in the package
  • @ - joins the string together
  • 2f92e0f4 the hashcode of the object.

The name of array classes look a little different, which is explained well in the Javadocs for Class.getName(). For instance, [Ljava.lang.String means:

  • [ - an single-dimensional array (as opposed to [[ or [[[ etc.)
  • L - the array contains a class or interface
  • java.lang.String - the type of objects in the array

Customizing the Output

To print something different when you call System.out.println(myObject), you must override the toString() method in your own class. Here's a simple example:

public class Person {

  private String name;
  // constructors and other methods omitted
  public String toString() {
    return name;

Now if we print a Person, we see their name rather than

Bear in mind that toString() is just one way for an object to be converted to a string. Typically this output should fully describe your object in a clear and concise manner. A better toString() for our Person class might be:

public String toString() {
  return getClass().getSimpleName() + "[name=" + name + "]";

Which would print, e.g., Person[name=Henry]. That's a really useful piece of data for debugging/testing.

If you want to focus on just one aspect of your object or include a lot of jazzy formatting, you might be better to define a separate method instead, e.g. String toElegantReport() {...}.

Auto-generating the Output

Many IDEs offer support for auto-generating a toString() method, based on the fields in the class. See docs for Eclipse and IntelliJ, for example.

Several popular Java libraries offer this feature as well. Some examples include:

Printing groups of objects

So you've created a nice toString() for your class. What happens if that class is placed into an array or a collection?


If you have an array of objects, you can call Arrays.toString() to produce a simple representation of the contents of the array. For instance, consider this array of Person objects:

Person[] people = { new Person("Fred"), new Person("Mike") };

// Prints: [Fred, Mike]

Note: this is a call to a static method called toString() in the Arrays class, which is different to what we've been discussing above.

If you have a multi-dimensional array, you can use Arrays.deepToString() to achieve the same sort of output.


Most collections will produce a pretty output based on calling .toString() on every element.

List<Person> people = new ArrayList<>();
people.add(new Person("Alice"));
people.add(new Person("Bob"));    

// Prints [Alice, Bob]

So you just need to ensure your list elements define a nice toString() as discussed above.

How to get < span > value?

var test = document.getElementById( 'test' );

// To get the text only, you can use "textContent"
console.log( test.textContent ); // "1 2 3 4"

textContent is the standard way. innerText is the property to use for legacy IE. If you want something as cross browser as possible, recursively use nodeValue.

Annotation-specified bean name conflicts with existing, non-compatible bean def

Explanation internal working on this error

You are getting this error because after instantiation the container is trying to assign same object to both classes as class name is same irrespective of different packages......thats why error says non compatible bean definition of same name ..

Actually how it works internally is--->>>>.

pkg test1; …. @RestController class Test{}

pkg test2; …. @RestController class Test{}

First container will get class Test and @RestController indicates it to instantiate as…test = new Test(); and it won’t instantiate twice After instantiating container will provide a reference variable test(same as class name) to both the classes and while it provide test reference To second class it gets non compatible bean definition of same name ……


Assign a refrence name to both rest controller so that container won’t instantiate with default name and instantiate saperately for both classes irrespective Of same name

For example——>>>

pkg test1; …. @RestController(“test1”) class Test{}

pkg test2; …. @RestController(“test2”) class Test{}

Note:The same will work with @Controller,@Service,@Repository etc..

Note: if you are creating reference variable at class level then you can also annotate it with @Qualifier("specific refrence name") for example @Autowired @Qualifier("test1") Test test;

Python CSV error: line contains NULL byte

Instead of csv reader I use read file and split function for string:

lines = open(input_file,'rb') 

for line_all in lines:

    line=line_all.replace('\x00', '').split(";")

What do .c and .h file extensions mean to C?

The .c files are source files which will be compiled. The .h files are used to expose the API of a program to either other part of that program or other program is you are creating a library.

For example, the program PizzaDelivery could have 1 .c file with the main program, and 1 .c file with utility functions. Now, for the main part of the program to be able to use the utility functions, you need to expose the API, via function prototype, into a .h file, this .h file being included by the main .c file.

List of phone number country codes

There is a fairly well maintained repo on github that has a CSV (with semicolon delimiters), XML, and JSON source of countries, country codes, and other information.

Set space between divs

Float them both the same way and add the margin of 40px. If you have 2 elements floating opposite ways you will have much less control and the containing element will determine how far apart they are.

    float: left;
    margin-right: 40px;
   float: left;

Django: Redirect to previous page after login

In registration/login.html (nested within templates folder) if you insert the following line, the page will render like Django's original admin login page:

{% include "admin/login.html" %}

Note: The file should contain above lines only.

python mpl_toolkits installation issue

I can't comment due to the lack of reputation, but if you are on arch linux, you should be able to find the corresponding libraries on the arch repositories directly. For example for mpl_toolkits.basemap:

pacman -S python-basemap

How to create a timer using tkinter?

from tkinter import *
import time
def clock():
    if t!='':
        label1.config(text=t,font='times 25')

How to print GETDATE() in SQL Server with milliseconds in time?

Create a function with return format yyyy-mm-hh hh:mi:ss.sss

create function fn_retornaFecha (@i_fecha datetime)
returns varchar(23)
@w_fecha varchar(23),
@w_anio  varchar(4),
@w_mes   varchar(2),
@w_dia   varchar(2),
@w_hh    varchar(2),
@w_nn    varchar(2),
@w_ss    varchar(2),
@w_sss   varchar(3)

select @w_fecha = null

if ltrim(rtrim(@i_fecha)) is not null 
   @w_anio = replicate('0',4-char_length( convert(varchar(4), year(@i_fecha)) )) + convert(varchar(4), year(@i_fecha)),
   @w_mes  = replicate('0',2-char_length( convert(varchar(2),month(@i_fecha)) )) + convert(varchar(2),month(@i_fecha)),
   @w_dia  = replicate('0',2-char_length( convert(varchar(2),  day(@i_fecha)) )) + convert(varchar(2),  day(@i_fecha))  ,
   @w_hh   = replicate('0',2-char_length( convert(varchar(2),datepart( hh, @i_fecha ) ) )) + convert(varchar(2),datepart( hh, @i_fecha ) ),
   @w_nn   = replicate('0',2-char_length( convert(varchar(2),datepart( mi, @i_fecha ) ) )) + convert(varchar(2),datepart( mi, @i_fecha ) ),
   @w_ss   = replicate('0',2-char_length( convert(varchar(2),datepart( ss, @i_fecha ) ) )) + convert(varchar(2),datepart( ss, @i_fecha ) ),
   @w_sss  = convert(varchar(3),datepart( ms, @i_fecha ) ) + replicate('0',3-DATALENGTH( convert(varchar(3),datepart( ms, @i_fecha ) )  ))

   select @w_fecha = @w_anio + '-' + @w_mes + '-' + @w_dia + ' ' + @w_hh + ':' + @w_nn + ':' + @w_ss + '.' + @w_sss

return @w_fecha



select fn_retornaFecha(getdate())

and the result is: 2016-12-21 10:12:50.123

dismissModalViewControllerAnimated deprecated

Now in iOS 6 and above, you can use:

[[Picker presentingViewController] dismissViewControllerAnimated:YES completion:nil];

Instead of:

[[Picker parentViewControl] dismissModalViewControllerAnimated:YES];

...And you can use:

[self presentViewController:picker animated:YES completion:nil];

Instead of

[self presentModalViewController:picker animated:YES];    

How to read numbers from file in Python?

To me this kind of seemingly simple problem is what Python is all about. Especially if you're coming from a language like C++, where simple text parsing can be a pain in the butt, you'll really appreciate the functionally unit-wise solution that python can give you. I'd keep it really simple with a couple of built-in functions and some generator expressions.

You'll need open(name, mode), myfile.readlines(), mystring.split(), int(myval), and then you'll probably want to use a couple of generators to put them all together in a pythonic way.

# This opens a handle to your file, in 'r' read mode
file_handle = open('mynumbers.txt', 'r')
# Read in all the lines of your file into a list of lines
lines_list = file_handle.readlines()
# Extract dimensions from first line. Cast values to integers from strings.
cols, rows = (int(val) for val in lines_list[0].split())
# Do a double-nested list comprehension to get the rest of the data into your matrix
my_data = [[int(val) for val in line.split()] for line in lines_list[1:]]

Look up generator expressions here. They can really simplify your code into discrete functional units! Imagine doing the same thing in 4 lines in C++... It would be a monster. Especially the list generators, when I was I C++ guy I always wished I had something like that, and I'd often end up building custom functions to construct each kind of array I wanted.

How do I replace NA values with zeros in an R dataframe?

For a single vector:

x <- c(1,2,NA,4,5)
x[] <- 0

For a data.frame, make a function out of the above, then apply it to the columns.

Please provide a reproducible example next time as detailed here:

How to make a great R reproducible example?

How do I configure git to ignore some files locally?

Update: Consider using git update-index --skip-worktree [<file>...] instead, thanks @danShumway! See Borealid's explanation on the difference of the two options.

Old answer:

If you need to ignore local changes to tracked files (we have that with local modifications to config files), use git update-index --assume-unchanged [<file>...].

How to convert an Stream into a byte[] in C#?

Byte[] Content = new BinaryReader(file.InputStream).ReadBytes(file.ContentLength);

configure Git to accept a particular self-signed server certificate for a particular https remote

OSX User adjustments.

Following the steps of the Accepted answer worked for me with a small addition when configuring on OSX.

I put the cert.pem file in a directory under my OSX logged in user and thus caused me to adjust the location for the trusted certificate.

Configure git to trust this certificate:

$ git config --global http.sslCAInfo $HOME/git-certs/cert.pem

<ng-container> vs <template>

Imo use cases for ng-container are simple replacements for which a custom template/component would be overkill. In the API doc they mention the following

use a ng-container to group multiple root nodes

and I guess that's what it is all about: grouping stuff.

Be aware that the ng-container directive falls away instead of a template where its directive wraps the actual content.

Select multiple columns from a table, but group by one

Your Data

DECLARE @OrderDetails TABLE 
(ProductID INT,ProductName VARCHAR(10), OrderQuantity INT)



 Select ProductID, ProductName, Sum(OrderQuantity) AS Total
 from @OrderDetails 
 Group By ProductID, ProductName  ORDER BY ProductID


¦ ProductID ¦ ProductName ¦ Total ¦
¦      1001 ¦ abc         ¦    12 ¦
¦      1002 ¦ abc         ¦    23 ¦
¦      2002 ¦ xyz         ¦     8 ¦
¦      3004 ¦ ytp         ¦    15 ¦
¦      4001 ¦ aze         ¦    19 ¦

How to resize Image in Android?

resized = Bitmap.createScaledBitmap(yourImageBitmap,(int)(yourImageBitmap.getWidth()*0.9), (int)(yourBitmap.getHeight()*0.9), true);

Perform curl request in javascript?

Yes, use getJSONP. It's the only way to make cross domain/server async calls. (*Or it will be in the near future). Something like

$.getJSON('your-api-url/validate.php?'+$(this).serialize+'callback=?', function(data){

The callback parameter will be filled in automatically by the browser, so don't worry.

On the server side ('validate.php') you would have something like this

//if condition is met
echo $_GET['callback'] . '(' . "{'message' : 'success', 'userID':'69', 'serial' : 'XYZ99UAUGDVD&orwhatever'}". ')';
else echo json_encode(array('error'=>'failed'));

nginx missing sites-available directory

Well, I think nginx by itself doesn't have that in its setup, because the Ubuntu-maintained package does it as a convention to imitate Debian's apache setup. You could create it yourself if you wanted to emulate the same setup.

Create /etc/nginx/sites-available and /etc/nginx/sites-enabled and then edit the http block inside /etc/nginx/nginx.conf and add this line

include /etc/nginx/sites-enabled/*;

Of course, all the files will be inside sites-available, and you'd create a symlink for them inside sites-enabled for those you want enabled.

What EXACTLY is meant by "de-referencing a NULL pointer"?

A NULL pointer points to memory that doesn't exist, and will raise Segmentation fault. There's an easier way to de-reference a NULL pointer, take a look.

int main(int argc, char const *argv[])
    *(int *)0 = 0; // Segmentation fault (core dumped)
    return 0;

Since 0 is never a valid pointer value, a fault occurs.

SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=NULL}

How do I read a text file of about 2 GB?

I use UltraEdit to edit large files. The maximum size I open with UltraEdit was about 2.5 GB. Also UltraEdit has a good hex editor in comparison to Notepad++.

PHP: if !empty & empty

Here's a compact way to do something different in all four cases:

if(empty($youtube)) {
    if(empty($link)) {
        # both empty
    } else {
        # only $youtube not empty
} else {
    if(empty($link)) {
        # only $link empty
    } else {
        # both not empty

If you want to use an expression instead, you can use ?: instead:

echo empty($youtube) ? ( empty($link) ? 'both empty' : 'only $youtube not empty' )
                     : ( empty($link) ? 'only $link empty' : 'both not empty' );

Malformed String ValueError ast.literal_eval() with String representation of Tuple

From the documentation for ast.literal_eval():

Safely evaluate an expression node or a string containing a Python expression. The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dicts, booleans, and None.

Decimal isn't on the list of things allowed by ast.literal_eval().

How do you get a query string on Flask?

The full URL is available as request.url, and the query string is available as request.query_string.decode().

Here's an example:

from flask import request

def adhoc_test():

    return request.query_string

To access an individual known param passed in the query string, you can use request.args.get('param'). This is the "right" way to do it, as far as I know.

ETA: Before you go further, you should ask yourself why you want the query string. I've never had to pull in the raw string - Flask has mechanisms for accessing it in an abstracted way. You should use those unless you have a compelling reason not to.

Why does Path.Combine not properly concatenate filenames that start with Path.DirectorySeparatorChar?

This is kind of a philosophical question (which perhaps only Microsoft can truly answer), since it's doing exactly what the documentation says.


"If path2 contains an absolute path, this method returns path2."

Here's the actual Combine method from the .NET source. You can see that it calls CombineNoChecks, which then calls IsPathRooted on path2 and returns that path if so:

public static String Combine(String path1, String path2) {
    if (path1==null || path2==null)
        throw new ArgumentNullException((path1==null) ? "path1" : "path2");

    return CombineNoChecks(path1, path2);

internal static string CombineNoChecks(string path1, string path2)
    if (path2.Length == 0)
        return path1;

    if (path1.Length == 0)
        return path2;

    if (IsPathRooted(path2))
        return path2;

    char ch = path1[path1.Length - 1];
    if (ch != DirectorySeparatorChar && ch != AltDirectorySeparatorChar &&
            ch != VolumeSeparatorChar) 
        return path1 + DirectorySeparatorCharAsString + path2;
    return path1 + path2;

I don't know what the rationale is. I guess the solution is to strip off (or Trim) DirectorySeparatorChar from the beginning of the second path; maybe write your own Combine method that does that and then calls Path.Combine().

How to deal with "data of class uneval" error from ggplot2?

when you add a new data set to a geom you need to use the data= argument. Or put the arguments in the proper order mapping=..., data=.... Take a look at the arguments for ?geom_line.


p + geom_line(data=df.last, aes(HrEnd, MWh, group=factor(Date)), color="red") 


p + geom_line(aes(HrEnd, MWh, group=factor(Date)), df.last, color="red") 

Rendering JSON in controller

What exactly do you want to know? ActiveRecord has methods that serialize records into JSON. For instance, open up your rails console and enter ModelName.all.to_json and you will see JSON output. render :json essentially calls to_json and returns the result to the browser with the correct headers. This is useful for AJAX calls in JavaScript where you want to return JavaScript objects to use. Additionally, you can use the callback option to specify the name of the callback you would like to call via JSONP.

For instance, lets say we have a User model that looks like this: {name: 'Max', email:' [email protected]'}

We also have a controller that looks like this:

class UsersController < ApplicationController
    def show
        @user = User.find(params[:id])
        render json: @user

Now, if we do an AJAX call using jQuery like this:

    type: "GET",
    url: "/users/5",
    dataType: "json",
    success: function(data){
        alert( // Will alert Max

As you can see, we managed to get the User with id 5 from our rails app and use it in our JavaScript code because it was returned as a JSON object. The callback option just calls a JavaScript function of the named passed with the JSON object as the first and only argument.

To give an example of the callback option, take a look at the following:

class UsersController < ApplicationController
    def show
        @user = User.find(params[:id])
        render json: @user, callback: "testFunction"

Now we can crate a JSONP request as follows:

function testFunction(data) {
    alert(; // Will alert Max

var script = document.createElement("script");
script.src = "/users/5";


The motivation for using such a callback is typically to circumvent the browser protections that limit cross origin resource sharing (CORS). JSONP isn't used that much anymore, however, because other techniques exist for circumventing CORS that are safer and easier.

Clearing content of text file using C#

Another short version:

System.IO.File.WriteAllBytes(path, new byte[0]);

fill an array in C#

you could write an extension method

public static void Fill<T>(this T[] array, T value)
  for(int i = 0; i < array.Length; i++) 
     array[i] = value;

Android - styling seek bar

My answer is inspired from Andras Balázs Lajtha answer it allow to work without xml file

seekBar.getProgressDrawable().setColorFilter(Color.RED, PorterDuff.Mode.SRC_IN);
seekBar.getThumb().setColorFilter(Color.RED, PorterDuff.Mode.SRC_IN);

How to rename a single column in a data.frame?

This can also be done using Hadley's plyr package, and the rename function.

df <- data.frame(foo=rnorm(1000)) 
df <- rename(df,c('foo'='samples'))

You can rename by the name (without knowing the position) and perform multiple renames at once. After doing a merge, for example, you might end up with:

  letterid id.x id.y
1       70    2    1
2      116    6    5
3      116    6    4
4      116    6    3
5      766   14    9
6      766   14   13

Which you can then rename in one step using:

letters <- rename(letters,c("id.x" = "source", "id.y" = "target"))

  letterid source target
1       70      2      1
2      116      6      5
3      116      6      4
4      116      6      3
5      766     14      9
6      766     14     13

jQuery delete confirmation box

Try this my friend

  // Confirmation Message On Delete Button._x000D_
  $('.close').click(function() {_x000D_
    return confirm('Are You Sure ?')_x000D_
<script src=""></script>_x000D_
<td class='close'></td>

How to make MySQL handle UTF-8 properly

To make this 'permanent', in my.cnf:

character-set-server = utf8

To check, go to the client and show some variables:

SHOW VARIABLES LIKE 'character_set%';

Verify that they're all utf8, except ..._filesystem, which should be binary and ..._dir, that points somewhere in the MySQL installation.

File to byte[] in Java

Using the same approach as the community wiki answer, but cleaner and compiling out of the box (preferred approach if you don't want to import Apache Commons libs, e.g. on Android):

public static byte[] getFileBytes(File file) throws IOException {
    ByteArrayOutputStream ous = null;
    InputStream ios = null;
    try {
        byte[] buffer = new byte[4096];
        ous = new ByteArrayOutputStream();
        ios = new FileInputStream(file);
        int read = 0;
        while ((read = != -1)
            ous.write(buffer, 0, read);
    } finally {
        try {
            if (ous != null)
        } catch (IOException e) {
            // swallow, since not that important
        try {
            if (ios != null)
        } catch (IOException e) {
            // swallow, since not that important
    return ous.toByteArray();

Swing/Java: How to use the getText and setText string properly

the getText method returns a String, while the setText receives a String, so you can write it like label1.setText(nameField.getText()); in your listener.

Detect encoding and make everything UTF-8

I know this is an older question, but I figure a useful answer never hurts. I was having issues with my encoding between a desktop application, SQLite, and GET/POST variables. Some would be in UTF-8, some would be in ASCII, and basically everything would get screwed up when foreign characters got involved.

Here is my solution. It scrubs your GET/POST/REQUEST (I omitted cookies, but you could add them if desired) on each page load before processing. It works well in a header. PHP will throw warnings if it can't detect the source encoding automatically, so these warnings are suppressed with @'s.

//Convert everything in our vars to UTF-8 for playing nice with the database...
//Use some auto detection here to help us not double-encode...
//Suppress possible warnings with @'s for when encoding cannot be detected
    $process = array(&$_GET, &$_POST, &$_REQUEST);
    while (list($key, $val) = each($process)) {
        foreach ($val as $k => $v) {
            if (is_array($v)) {
                $process[$key][@mb_convert_encoding($k,'UTF-8','auto')] = $v;
                $process[] = &$process[$key][@mb_convert_encoding($k,'UTF-8','auto')];
            } else {
                $process[$key][@mb_convert_encoding($k,'UTF-8','auto')] = @mb_convert_encoding($v,'UTF-8','auto');
catch(Exception $ex){}

How to identify all stored procedures referring a particular table

The following works on SQL2008 and above. Provides a list of both stored procedures and functions.

select distinct [Table Name] = o.Name, [Found In] = sp.Name, sp.type_desc
  from sys.objects o inner join sys.sql_expression_dependencies  sd on o.object_id = sd.referenced_id
                inner join sys.objects sp on sd.referencing_id = sp.object_id
                    and sp.type in ('P', 'FN')
  where = 'YourTableName'
  order by sp.Name

How to extract numbers from string in c?

here after a simple solution using sscanf:


char str[256]="ab234cid*(s349*(20kd";
char tmp[256];

int main()

    int x;
    while (sscanf(str,"%[^0123456789]%s",tmp,str)>1||sscanf(str,"%d%s",&x,str))
        if (tmp[0]=='\0')


Center a 'div' in the middle of the screen, even when the page is scrolled up or down?

I just found a new trick to center a box in the middle of the screen even if you don't have fixed dimensions. Let's say you would like a box 60% width / 60% height. The way to make it centered is by creating 2 boxes: a "container" box that position left: 50% top :50%, and a "text" box inside with reverse position left: -50%; top :-50%;

It works and it's cross browser compatible.

Check out the code below, you probably get a better explanation:

jQuery('.close a, .bg', '#message').on('click', function() {_x000D_
  return false;_x000D_
html, body {_x000D_
  min-height: 100%;_x000D_
#message {_x000D_
  height: 100%;_x000D_
  left: 0;_x000D_
  position: fixed;_x000D_
  top: 0;_x000D_
  width: 100%;_x000D_
#message .container {_x000D_
  height: 60%;_x000D_
  left: 50%;_x000D_
  position: absolute;_x000D_
  top: 50%;_x000D_
  z-index: 10;_x000D_
  width: 60%;_x000D_
#message .container .text {_x000D_
  background: #fff;_x000D_
  height: 100%;_x000D_
  left: -50%;_x000D_
  position: absolute;_x000D_
  top: -50%;_x000D_
  width: 100%;_x000D_
#message .bg {_x000D_
  background: rgba(0, 0, 0, 0.5);_x000D_
  height: 100%;_x000D_
  left: 0;_x000D_
  position: absolute;_x000D_
  top: 0;_x000D_
  width: 100%;_x000D_
  z-index: 9;_x000D_
<script src=""></script>_x000D_
<div id="message">_x000D_
  <div class="container">_x000D_
    <div class="text">_x000D_
      <p>The message</p>_x000D_
      <p class="close"><a href="#">Close Window</a></p>_x000D_
  <div class="bg"></div>_x000D_

Configure apache to listen on port other than 80

It was a firewall issue. There was a hardware firewall that was blocking access to almost all ports. (Turning off software firewall / SELinux bla bla had no effect)

Then I scanned the open ports and used the port that was open.

If you are facing the same problem, Run the following command

sudo nmap -T Aggressive -A -v -p 1-65000

It will scan for all the open ports on your system. Any port that is open can be accessed from outside.


How get total sum from input box values using Javascript?


Qty1 : <input onblur="findTotal()" type="text" name="qty" id="qty1"/><br>
Qty2 : <input onblur="findTotal()" type="text" name="qty" id="qty2"/><br>
Qty3 : <input onblur="findTotal()" type="text" name="qty" id="qty3"/><br>
Qty4 : <input onblur="findTotal()" type="text" name="qty" id="qty4"/><br>
Qty5 : <input onblur="findTotal()" type="text" name="qty" id="qty5"/><br>
Qty6 : <input onblur="findTotal()" type="text" name="qty" id="qty6"/><br>
Qty7 : <input onblur="findTotal()" type="text" name="qty" id="qty7"/><br>
Qty8 : <input onblur="findTotal()" type="text" name="qty" id="qty8"/><br>
Total : <input type="text" name="total" id="total"/>

    <script type="text/javascript">
function findTotal(){
    var arr = document.getElementsByName('qty');
    var tot=0;
    for(var i=0;i<arr.length;i++){
            tot += parseInt(arr[i].value);
    document.getElementById('total').value = tot;


How to change the data type of a column without dropping the column with query?

ALTER TABLE YourTableNameHere ALTER COLUMN YourColumnNameHere VARCHAR(20)

Inserting values into tables Oracle SQL

INTO    Employee 
        (emp_id, emp_name, emp_address, emp_state, emp_position, emp_manager)
SELECT  '001', 'John Doe', '1 River Walk, Green Street', state_id, position_id, manager_id
FROM    dual
JOIN    state s
ON      s.state_name = 'New York'
JOIN    positions p
ON      p.position_name = 'Sales Executive'
JOIN    manager m
ON      m.manager_name = 'Barry Green'

Note that but a single spelling mistake (or an extra space) will result in a non-match and nothing will be inserted.

AngularJS - ng-if check string empty value

You don't need to explicitly use qualifiers like == '' or != ''. Like in JavaScript, an empty string will be evaluated as false.

Your views will be much cleaner and readable as well.

<script src=""></script>_x000D_
<div ng-app init="item = {photo: ''}">_x000D_
   <div ng-if=""> show if photo is not empty</div>_x000D_
   <div ng-if="!"> show if photo is empty</div>_x000D_
   <input type=text ng-model="" placeholder="photo" />_x000D_

Updated to remove bug in Angular

How does ApplicationContextAware work in Spring?

When spring instantiates beans, it looks for a couple of interfaces like ApplicationContextAware and InitializingBean. If they are found, the methods are invoked. E.g. (very simplified)

Class<?> beanClass = beanDefinition.getClass();
Object bean = beanClass.newInstance();
if (bean instanceof ApplicationContextAware) {
    ((ApplicationContextAware) bean).setApplicationContext(ctx);

Note that in newer version it may be better to use annotations, rather than implementing spring-specific interfaces. Now you can simply use:

@Inject // or @Autowired
private ApplicationContext ctx;

What are the complexity guarantees of the standard containers?

I found the nice resource Standard C++ Containers. Probably this is what you all looking for.



vector<T> v;              Make an empty vector.                                     O(1)
vector<T> v(n);           Make a vector with N elements.                            O(n)
vector<T> v(n, value);    Make a vector with N elements, initialized to value.      O(n)
vector<T> v(begin, end);  Make a vector and copy the elements from begin to end.    O(n)


v[i]          Return (or set) the I'th element.                        O(1)       Return (or set) the I'th element, with bounds checking.  O(1)
v.size()      Return current number of elements.                       O(1)
v.empty()     Return true if vector is empty.                          O(1)
v.begin()     Return random access iterator to start.                  O(1)
v.end()       Return random access iterator to end.                    O(1)
v.front()     Return the first element.                                O(1)
v.back()      Return the last element.                                 O(1)
v.capacity()  Return maximum number of elements.                       O(1)


v.push_back(value)         Add value to end.                                                O(1) (amortized)
v.insert(iterator, value)  Insert value at the position indexed by iterator.                O(n)
v.pop_back()               Remove value from end.                                           O(1)
v.assign(begin, end)       Clear the container and copy in the elements from begin to end.  O(n)
v.erase(iterator)          Erase value indexed by iterator.                                 O(n)
v.erase(begin, end)        Erase the elements from begin to end.                            O(n)

For other containers, refer to the page.

jQuery - how to write 'if not equal to' (opposite of ==)

== => !=

=== => !==

Equal and its opposite

OperationalError, no such column. Django

In my case, in I was querying from the table in which new ForeignKey field was added. So comment out then run makemigrations and migrate command as usual. Finally uncomment

How to overwrite the output directory in spark

since, source, mode) is deprecated, (

use df.write.format(source).mode("overwrite").save(path)
where df.write is DataFrameWriter

'source' can be ("com.databricks.spark.avro" | "parquet" | "json")

How do I write JSON data to a file?

You forgot the actual JSON part - data is a dictionary and not yet JSON-encoded. Write it like this for maximum compatibility (Python 2 and 3):

import json
with open('data.json', 'w') as f:
    json.dump(data, f)

On a modern system (i.e. Python 3 and UTF-8 support), you can write a nicer file with

import json
with open('data.json', 'w', encoding='utf-8') as f:
    json.dump(data, f, ensure_ascii=False, indent=4)

How to insert multiple rows from array using CodeIgniter framework?

You could always use mysql's LOAD DATA:

LOAD DATA LOCAL INFILE '/full/path/to/file/foo.csv' INTO TABLE `footable` FIELDS TERMINATED BY ',' LINES TERMINATED BY '\r\n' 

to do bulk inserts rather than using a bunch of INSERT statements.

Correct way of using log4net (logger naming)

Disadvantage of second approach is big repository with created loggers. This loggers do the same if root is defined and class loggers are not defined. Standard scenario on production system is using few loggers dedicated to group of class. Sorry for my English.

IntelliJ show JavaDocs tooltip on mouse over

The easiest way, at least for me, was:

  • Ctrl+Shift+A
  • Type: show document
  • Show quick documentation on mouse move (set it to ON)

How to define a Sql Server connection string to use in VB.NET?

Standard Security:

Server=myServerAddress;Database=myDataBase;User Id=myUsername;Password=myPassword;

Trusted Connection:


will be glad if it helps.


Button Width Match Parent

This one worked for me

width: MediaQuery.of(context).size.width-100,

Node.js: How to read a stream into a buffer?

You can convert your readable stream to a buffer and integrate it in your code in an asynchronous way like this.

async streamToBuffer (stream) {
    return new Promise((resolve, reject) => {
      const data = [];

      stream.on('data', (chunk) => {

      stream.on('end', () => {

      stream.on('error', (err) => {

the usage would be as simple as:

 // usage
  const myStream // your stream
  const buffer = await streamToBuffer(myStream) // this is a buffer

std::wstring VS std::string

Applications that are not satisfied with only 256 different characters have the options of either using wide characters (more than 8 bits) or a variable-length encoding (a multibyte encoding in C++ terminology) such as UTF-8. Wide characters generally require more space than a variable-length encoding, but are faster to process. Multi-language applications that process large amounts of text usually use wide characters when processing the text, but convert it to UTF-8 when storing it to disk.

The only difference between a string and a wstring is the data type of the characters they store. A string stores chars whose size is guaranteed to be at least 8 bits, so you can use strings for processing e.g. ASCII, ISO-8859-15, or UTF-8 text. The standard says nothing about the character set or encoding.

Practically every compiler uses a character set whose first 128 characters correspond with ASCII. This is also the case with compilers that use UTF-8 encoding. The important thing to be aware of when using strings in UTF-8 or some other variable-length encoding, is that the indices and lengths are measured in bytes, not characters.

The data type of a wstring is wchar_t, whose size is not defined in the standard, except that it has to be at least as large as a char, usually 16 bits or 32 bits. wstring can be used for processing text in the implementation defined wide-character encoding. Because the encoding is not defined in the standard, it is not straightforward to convert between strings and wstrings. One cannot assume wstrings to have a fixed-length encoding either.

If you don't need multi-language support, you might be fine with using only regular strings. On the other hand, if you're writing a graphical application, it is often the case that the API supports only wide characters. Then you probably want to use the same wide characters when processing the text. Keep in mind that UTF-16 is a variable-length encoding, meaning that you cannot assume length() to return the number of characters. If the API uses a fixed-length encoding, such as UCS-2, processing becomes easy. Converting between wide characters and UTF-8 is difficult to do in a portable way, but then again, your user interface API probably supports the conversion.

How to encode Doctrine entities to JSON in Symfony 2.0 AJAX application?

Another option is to use the JMSSerializerBundle. In your controller you then do

$serializer = $this->container->get('serializer');
$reports = $serializer->serialize($doctrineobject, 'json');
return new Response($reports); // should be $reports as $doctrineobject is not serialized

You can configure how the serialization is done by using annotations in the entity class. See the documentation in the link above. For example, here's how you would exclude linked entities:

* Iddp\RorBundle\Entity\Report
* @ORM\Table()
* @ORM\Entity(repositoryClass="Iddp\RorBundle\Entity\ReportRepository")
* @ExclusionPolicy("None")
* @ORM\ManyToOne(targetEntity="Client", inversedBy="reports")
* @ORM\JoinColumn(name="client_id", referencedColumnName="id")
* @Exclude
protected $client;

Upgrade python in a virtualenv

I just want to clarify, because some of the answers refer to venv and others refer to virtualenv.

Use of the -p or --python flag is supported on virtualenv, but not on venv. If you have more than one Python version and you want to specify which one to create the venv with, do it on the command line, like this:

malikarumi@Tetuoan2:~/Projects$ python3.6 -m venv {path to pre-existing dir you want venv in}

You can of course upgrade with venv as others have pointed out, but that assumes you have already upgraded the Python that was used to create that venv in the first place. You can't upgrade to a Python version you don't already have on your system somewhere, so make sure to get the version you want, first, then make all the venvs you want from it.

How do I copy the contents of one stream to another?

The basic questions that differentiate implementations of "CopyStream" are:

  • size of the reading buffer
  • size of the writes
  • Can we use more than one thread (writing while we are reading).

The answers to these questions result in vastly different implementations of CopyStream and are dependent on what kind of streams you have and what you are trying to optimize. The "best" implementation would even need to know what specific hardware the streams were reading and writing to.

Prevent Caching in ASP.NET MVC for specific actions using an attribute

Output Caching in MVC

[OutputCache(NoStore = true, Duration = 0, Location="None", VaryByParam = "*")]

[OutputCache(NoStore = true, Duration = 0, VaryByParam = "None")]

Jackson - How to process (deserialize) nested JSON?

Here is a rough but more declarative solution. I haven't been able to get it down to a single annotation, but this seems to work well. Also not sure about performance on large data sets.

Given this JSON:

    "list": [
            "wrapper": {
                "name": "Jack"
            "wrapper": {
                "name": "Jane"

And these model objects:

public class RootObject {
    @JsonDeserialize(contentUsing = SkipWrapperObjectDeserializer.class)
    public InnerObject[] innerObjects;


public class InnerObject {
    public String name;

Where the Jackson voodoo is implemented like:

public @interface SkipWrapperObject {
    String value();


public class SkipWrapperObjectDeserializer extends JsonDeserializer<Object> implements
        ContextualDeserializer {
    private Class<?> wrappedType;
    private String wrapperKey;

    public JsonDeserializer<?> createContextual(DeserializationContext ctxt,
            BeanProperty property) throws JsonMappingException {
        SkipWrapperObject skipWrapperObject = property
        wrapperKey = skipWrapperObject.value();
        JavaType collectionType = property.getType();
        JavaType collectedType = collectionType.containedType(0);
        wrappedType = collectedType.getRawClass();
        return this;

    public Object deserialize(JsonParser parser, DeserializationContext ctxt)
            throws IOException, JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        ObjectNode objectNode = mapper.readTree(parser);
        JsonNode wrapped = objectNode.get(wrapperKey);
        Object mapped = mapIntoObject(wrapped);
        return mapped;

    private Object mapIntoObject(JsonNode node) throws IOException,
            JsonProcessingException {
        JsonParser parser = node.traverse();
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(parser, wrappedType);

Hope this is useful to someone!

How to change facebook login button with my custom image

I got it working with a call to something as simple as

function fb_login() {
  FB.login( function() {}, { scope: 'email,public_profile' } );

I don't know if facebook will ever be able to block this circumvention, but for now I can use whatever HTML or image I want to call fb_login and it works fine.

Reference: Facebook API Docs

Get DateTime.Now with milliseconds precision

The trouble with DateTime.UtcNow and DateTime.Now is that, depending on the computer and operating system, it may only be accurate to between 10 and 15 milliseconds. However, on windows computers one can use by using the low level function GetSystemTimePreciseAsFileTime to get microsecond accuracy, see the function GetTimeStamp() below.

    [System.Security.SuppressUnmanagedCodeSecurity, System.Runtime.InteropServices.DllImport("kernel32.dll")]
    static extern void GetSystemTimePreciseAsFileTime(out FileTime pFileTime);

    public struct FileTime  {
        public const long FILETIME_TO_DATETIMETICKS = 504911232000000000;   // 146097 = days in 400 year Gregorian calendar cycle. 504911232000000000 = 4 * 146097 * 86400 * 1E7
        public uint TimeLow;    // least significant digits
        public uint TimeHigh;   // most sifnificant digits
        public long TimeStamp_FileTimeTicks { get { return TimeHigh * 4294967296 + TimeLow; } }     // ticks since 1-Jan-1601 (1 tick = 100 nanosecs). 4294967296 = 2^32
        public DateTime dateTime { get { return new DateTime(TimeStamp_FileTimeTicks + FILETIME_TO_DATETIMETICKS); } }

    public static DateTime GetTimeStamp() { 
        FileTime ft; GetSystemTimePreciseAsFileTime(out ft);
        return ft.dateTime;

Reference to a non-shared member requires an object reference occurs when calling public sub

You either have to make the method Shared or use an instance of the class General:

Dim gen = New General()



Public Shared Sub updateDynamics(dynID As Int32)
    ' ... '
End Sub


What is the syntax for Typescript arrow functions with generics?

This works for me

const Generic = <T> (value: T) => {
    return value;

java.lang.RuntimeException: Unable to start activity ComponentInfo

After trying few answers they are either not related to my project or , I have tried cleaning and rebuilding ( But it didn't work for me directly. I have compared it with older version of code, in which i observed some library files(jars and aars in External Libraries directory) are missing. Tried Invalidate Cache and Restart worked, which created all the libraries and working fine.

SQLite3 database or disk is full / the database disk image is malformed

To avoid getting "database or disk is full" in the first place, try this if you have lots of RAM:

sqlite> pragma temp_store = 2;

That tells SQLite to put temp files in memory. (The "database or disk is full" message does not mean either that the database is full or that the disk is full! It means the temp directory is full.) I have 256G of RAM but only 2G of /tmp, so this works great for me. The more RAM you have, the bigger db files you can work with.

If you haven't got a lot of ram, try this:

sqlite> pragma temp_store = 1;
sqlite> pragma temp_store_directory = '/directory/with/lots/of/space';

temp_store_directory is deprecated (which is silly, since temp_store is not deprecated and requires temp_store_directory), so be wary of using this in code.

Combine two or more columns in a dataframe into a new column with a new name

As already mentioned in comments by Uwe and UseR, a general solution in the tidyverse format would be to use the command unite:


n = c(2, 3, 5) 
s = c("aa", "bb", "cc") 

df = data.frame(n, s, b) %>% 
  unite(x, c(n, s), sep = " ", remove = FALSE)

Multiple aggregations of the same column using pandas GroupBy.agg()

You can simply pass the functions as a list:

In [20]: df.groupby("dummy").agg({"returns": [np.mean, np.sum]})
           mean       sum
1      0.036901  0.369012

or as a dictionary:

In [21]: df.groupby('dummy').agg({'returns':
                                  {'Mean': np.mean, 'Sum': np.sum}})
           Mean       Sum
1      0.036901  0.369012

How do I measure a time interval in C?

Using the time.h library, try something like this:

long start_time, end_time, elapsed;

start_time = clock();
// Do something
end_time = clock();

elapsed = (end_time - start_time) / CLOCKS_PER_SEC * 1000;

How to get request URL in Spring Boot RestController

If you don't want any dependency on Spring's HATEOAS or javax.* namespace, use ServletUriComponentsBuilder to get URI of current request:

import org.springframework.web.util.UriComponentsBuilder;


How to find the 'sizeof' (a pointer pointing to an array)?

No, you can't. The compiler doesn't know what the pointer is pointing to. There are tricks, like ending the array with a known out-of-band value and then counting the size up until that value, but that's not using sizeof().

Another trick is the one mentioned by Zan, which is to stash the size somewhere. For example, if you're dynamically allocating the array, allocate a block one int bigger than the one you need, stash the size in the first int, and return ptr+1 as the pointer to the array. When you need the size, decrement the pointer and peek at the stashed value. Just remember to free the whole block starting from the beginning, and not just the array.

Abort a git cherry-pick?

I found the answer is git reset --merge - it clears the conflicted cherry-pick attempt.

How to select all instances of selected region in Sublime Text

Even though there are multiple answers, there is an issue using this approach. It selects all the text that matches, not only the whole words like variables.

As per "Sublime Text: Select all instances of a variable and edit variable name" and the answer in "Sublime Text: Select all instances of a variable and edit variable name", we have to start with a empty selection. That is, start using the shortcut Alt+F3 which would help selecting only the whole words.

What can lead to "IOError: [Errno 9] Bad file descriptor" during os.system()?

You get this error message if a Python file was closed from "the outside", i.e. not from the file object's close() method:

>>> f = open(".bashrc")
>>> os.close(f.fileno())
>>> del f
close failed in file object destructor:
IOError: [Errno 9] Bad file descriptor

The line del f deletes the last reference to the file object, causing its destructor file.__del__ to be called. The internal state of the file object indicates the file is still open since f.close() was never called, so the destructor tries to close the file. The OS subsequently throws an error because of the attempt to close a file that's not open.

Since the implementation of os.system() does not create any Python file objects, it does not seem likely that the system() call is the origin of the error. Maybe you could show a bit more code?

How to set a class attribute to a Symfony2 form input

Like this:

{{ form_widget(form.description, { 'attr': {'class': 'form-control', 'rows': '5', 'style': 'resize:none;'} }) }}

How can I create a blank/hardcoded column in a sql query?

    0 as placeholder -- for column having 0 value    

--OR '' as Placeholder -- for blank column    
--OR NULL as Placeholder -- for column having null value

Does Visual Studio have code coverage for unit tests?

For anyone that is looking for an easy solution in Visual Studio Community 2019, Fine Code Coverage is simple but it works well.

It cannot give accurate numbers on the precise coverage, but it will tell which lines are being covered with green/red gutters.

How do I get LaTeX to hyphenate a word that contains a dash?

multi-disciplinary will not be hyphenated, as explained by kennytm. But multi-\-disciplinary has the same hyphenation opportunities that multidisciplinary has.

I admit that I don't know why this works. It is different from the behaviour described here (emphasis mine):

The command \- inserts a discretionary hyphen into a word. This also becomes the only point where hyphenation is allowed in this word.

Can not change UILabel text color

// This is wrong 
categoryTitle.textColor = [UIColor colorWithRed:188 green:149 blue:88 alpha:1.0];

// This should be  
categoryTitle.textColor = [UIColor colorWithRed:188/255 green:149/255 blue:88/255 alpha:1.0];

// In the documentation, the limit of the parameters are mentioned.

colorWithRed:green:blue:alpha: documentation link

How to copy directories with spaces in the name

There is a bug in robocopy in interpreting the source name. If you include a back slash at the end of the path to describe a folder it keeps including the string for the source into the rest of the line. ie

robocopy "C:\back up\" %destination% /e Nothing here will go to the destination string

robocopy "C:\back up" %destination% /e but this works

I may be wrong but I think both should work!

How do I disable right click on my web page?

I know I am late, but I want to create some assumptions and explainations for the answer I am going to provide.

Can I disable right-click

Can I disable right click on my web page without using Javascript?

Yes, by using JavaScript you can disable any event that happens and you can do that mostly only by javaScript. How, all you need is:

  1. A working hardware

  2. A website or somewhere from which you can learn about the keycodes. Because you're gonna need them.

Now lets say you wanna block the enter key press here is the code:

function prevententer () {
 if(event.keyCode == 13) {
  return false;

For the right click use this:

event.button == 2

in the place of event.keyCode. And you'll block it.

I want to ask this because most browsers allow users to disable it by Javascript.

You're right, browsers allow you to use JavaScript and javascript does the whole job for you. You donot need to setup anything, just need the script attribute in the head.

Why you should not disable it?

The main and the fast answer to that would be, users won't like it. Everyone needs freedom, no-one I mean no-one wants to be blocked or disabled, a few minutes ago I was at a site, which had blocked me from right clicking and I felt why? Do you need to secure your source code? Then here ctrl+shift+J I have opened the Console and now I can go to HTML-code tab. Go ahead and stop me. This won't add any of the security layer to your app.

There are alot of userful menus in the Right Click, like Copy, Paste, Search Google for 'text' (In Chrome) and many more. So user would like to get ease of access instead of remembering alot of keyboard shortcuts. Anyone can still copy the context, save the image or do whatever he wants.

Browsers use Mouse Navigation: Some browsers such as Opera uses mouse navigation, so if you disable it, user would definitely hate your User Interface and the scripts.

So that was the basic, I was going to write some more about saving the source code hehehe but, let it be the answer to your question.

Reference to the keycodes:

Key and mouse button code: (would be appreciated by the users too).

Why not to disable right click:

Stick button to right side of div

Use position property

style="position: absolute;right:0;top:0"

How to show image using ImageView in Android

shoud be @drawable/image where image could have any extension like: image.png, image.xml, image.gif. Android will automatically create a reference in R class with its name, so you cannot have in any drawable folder image.png and image.gif.

Calculating a directory's size using Python?

If you are in Windows OS you can do:

install the module pywin32 by launching:

pip install pywin32

and then coding the following:

import win32com.client as com

def get_folder_size(path):
       fso = com.Dispatch("Scripting.FileSystemObject")
       folder = fso.GetFolder(path)
       size = str(round(folder.Size / 1048576))
       print("Size: " + size + " MB")
   except Exception as e:
       print("Error --> " + str(e))

Difference between Visibility.Collapsed and Visibility.Hidden

Even though a bit old thread, for those who still looking for the differences:

Aside from layout (space) taken in Hidden and not taken in Collapsed, there is another difference.

If we have custom controls inside this 'Collapsed' main control, the next time we set it to Visible, it will "load" all custom controls. It will not pre-load when window is started.

As for 'Hidden', it will load all custom controls + main control which we set as hidden when the "window" is started.

Android Log.v(), Log.d(), Log.i(), Log.w(), Log.e() - When to use each one?

The Android Studio website has recently (I think) provided some advice what kind of messages to expect from different log levels that may be useful along with Kurtis' answer:

  • Verbose - Show all log messages (the default).
  • Debug - Show debug log messages that are useful during development only, as well as the message levels lower in this list.
  • Info - Show expected log messages for regular usage, as well as the message levels lower in this list.
  • Warn - Show possible issues that are not yet errors, as well as the message levels lower in this list.
  • Error - Show issues that have caused errors, as well as the message level lower in this list.
  • Assert - Show issues that the developer expects should never happen.

Round to 2 decimal places

double formattedNumber = Double.parseDouble(new DecimalFormat("#.##").format(unformattedNumber));

worked for me :)

Creating an instance of class

  1. Allocates some dynamic memory from the free store, and creates an object in that memory using its default constructor. You never delete it, so the memory is leaked.
  2. Does exactly the same as 1; in the case of user-defined types, the parentheses are optional.
  3. Allocates some automatic memory, and creates an object in that memory using its default constructor. The memory is released automatically when the object goes out of scope.
  4. Similar to 3. Notionally, the named object foo4 is initialised by default-constructing, copying and destroying a temporary object; usually, this is elided giving the same result as 3.
  5. Allocates a dynamic object, then initialises a second by copying the first. Both objects are leaked; and there's no way to delete the first since you don't keep a pointer to it.
  6. Does exactly the same as 5.
  7. Does not compile. Foo foo5 is a declaration, not an expression; function (and constructor) arguments must be expressions.
  8. Creates a temporary object, and initialises a dynamic object by copying it. Only the dynamic object is leaked; the temporary is destroyed automatically at the end of the full expression. Note that you can create the temporary with just Foo() rather than the equivalent Foo::Foo() (or indeed Foo::Foo::Foo::Foo::Foo())

When do I use each?

  1. Don't, unless you like unnecessary decorations on your code.
  2. When you want to create an object that outlives the current scope. Remember to delete it when you've finished with it, and learn how to use smart pointers to control the lifetime more conveniently.
  3. When you want an object that only exists in the current scope.
  4. Don't, unless you think 3 looks boring and what to add some unnecessary decoration.
  5. Don't, because it leaks memory with no chance of recovery.
  6. Don't, because it leaks memory with no chance of recovery.
  7. Don't, because it won't compile
  8. When you want to create a dynamic Bar from a temporary Foo.

Adding extra zeros in front of a number using jQuery?

Assuming you have those values stored in some strings, try this:

function pad (str, max) {
  str = str.toString();
  return str.length < max ? pad("0" + str, max) : str;

pad("3", 3);    // => "003"
pad("123", 3);  // => "123"
pad("1234", 3); // => "1234"

var test = "MR 2";
var parts = test.split(" ");
parts[1] = pad(parts[1], 3);
parts.join(" "); // => "MR 002"

Downloading a large file using curl

when curl is used to download a large file then CURLOPT_TIMEOUT is the main option you have to set for.

CURLOPT_RETURNTRANSFER has to be true in case you are getting file like pdf/csv/image etc.

You may find the further detail over here(correct url) Curl Doc

From that page:

curl_setopt($request, CURLOPT_TIMEOUT, 300); //set timeout to 5 mins

curl_setopt($request, CURLOPT_RETURNTRANSFER, true); // true to get the output as string otherwise false

How can I run dos2unix on an entire directory?

for FILE in /var/www/html/files/*
 /usr/bin/dos2unix FILE

box-shadow on bootstrap 3 container

You should give the container an id and use that in your custom css file (which should be linked after the bootstrap css):

#container { box-shadow: values }

Using Chrome's Element Inspector in Print Preview Mode?

Since Chrome 32 you have the CSS media option in the Screen section of the drawer Emulation tab.

Just enable it, select print as the target media type, and - behold - your page is rendered [almost] the way it will be printed.

Use Esc to bring up the drawer if it's not visible.

How to check if all of the following items are in a list?

An example of how to do this using a lambda expression would be:

issublist = lambda x, y: 0 in [_ in x for _ in y]

How do I refresh the page in ASP.NET? (Let it reload itself by code)

There are various method to refresh the page in like...

Java Script

 function reloadPage()

Code Behind


Meta Tag

<meta http-equiv="refresh" content="600"></meta>

Page Redirection

Response.Redirect("~/default.aspx"); // Or whatever your page url

Is there an eval() function in Java?

With Java 9, we get access to jshell, so one can write something like this:

import jdk.jshell.JShell;
import java.lang.StringBuilder;

public class Eval {
    public static void main(String[] args) throws IOException {
        try(JShell js = JShell.create(); BufferedReader br = new BufferedReader(new InputStreamReader( {

            js.onSnippetEvent(snip -> {
                if (snip.status() == jdk.jshell.Snippet.Status.VALID) {
                    System.out.println("? " + snip.value());

            System.out.print("> ");
            for (String line = br.readLine(); line != null; line = br.readLine()) {
                System.out.print("> ");

Sample run:

> 1 + 2 / 4 * 3
? 1
> 32 * 121
? 3872
> 4 * 5
? 20
> 121 * 51
? 6171

Slightly op, but that's what Java currently has to offer

how to pass command line arguments to main method dynamically

We can pass string value to main method as argument without using commandline argument concept in java through Netbean

 package MainClass;
 import java.util.Scanner;
 public class CmdLineArgDemo {

 Scanner readData = new Scanner(;   
 System.out.println("Enter any string :");
 String str = readData.nextLine();
 String [] str1 = str.split(" ");
 // System.out.println(str1.length);

   public static void main(String [] args){
      for(int i = 0 ; i<args.length;i++) {
        System.out.print(args[i]+" ");


Enter any string : 
Coders invent Digital World 
Coders invent Digital World

Round a floating-point number down to the nearest integer?

Don't know if you solved this, but I just stumble upon this question. If you want to get rid of decimal points, you could use int(x) and it will eliminate all decimal digits. Theres no need to use round(x).

android.view.InflateException: Binary XML file line #12: Error inflating class <unknown>

I encountered the same bug and found the root reason is:

Use Application Context to inflate view.

Inflating with Activity Context fixed the bug.