Programs & Examples On #Lnk2001

error LNK2038: mismatch detected for '_MSC_VER': value '1600' doesn't match value '1700' in CppFile1.obj

for each project in your solution make sure that

Properties > Config. Properties > General > Platform Toolset

is one for all of them, v100 for visual studio 2010, v110 for visual studio 2012

you also may be working on v100 from visual studio 2012

error LNK2001: unresolved external symbol (C++)

That means that the definition of your function is not present in your program. You forgot to add that one.cpp to your program.

What "to add" means in this case depends on your build environment and its terminology. In MSVC (since you are apparently use MSVC) you'd have to add one.cpp to the project.

In more practical terms, applicable to all typical build methodologies, when you link you program, the object file created form one.cpp is missing.

Unresolved external symbol in object files

I had the same link errors, but from a test project which was referencing another dll. Found out that after adding _declspec(dllexport) in front of each function which was specified in the error message, the link was working well.

Reading a file line by line in Go

In Go 1.1 and newer the most simple way to do this is with a bufio.Scanner. Here is a simple example that reads lines from a file:

package main

import (

func main() {
    file, err := os.Open("/path/to/file.txt")
    if err != nil {
    defer file.Close()

    scanner := bufio.NewScanner(file)
    for scanner.Scan() {

    if err := scanner.Err(); err != nil {

This is the cleanest way to read from a Reader line by line.

There is one caveat: Scanner does not deal well with lines longer than 65536 characters. If that is an issue for you then then you should probably roll your own on top of Reader.Read().

How do I target only Internet Explorer 10 for certain situations like Internet Explorer-specific CSS or Internet Explorer-specific JavaScript code?

I've written a small, vanilla JavaScript plugin called Layout Engine, which allows you to feature detect IE 10 (and every other browser), in a simple way that cannot be faked, unlike user agent sniffing.

It adds the rendering engine name as a class on the html tag and returns a JavaScript object containing the vendor and version (where appropriate)

Check out my blog post: and get the code on GitHub:

selecting an entire row based on a variable excel vba

Saw this answer on another site and it works for me as well!

Posted by Shawn on October 14, 2001 1:24 PM

var1 = 1

var2 = 5

Rows(var1 & ":" & var2).Select

That worked for me, looks like you just have to keep the variables outside the quotes and add the and statement (&)


MySQL Select Query - Get only first 10 characters of a value

Have a look at either Left or Substring if you need to chop it up even more.

Google and the MySQL docs are a good place to start - you'll usually not get such a warm response if you've not even tried to help yourself before asking a question.

How can I link a photo in a Facebook album to a URL

Unfortunately, no. This feature is not available for facebook albums.

Creating a Plot Window of a Particular Size

This will depend on the device you're using. If you're using a pdf device, you can do this:

pdf( "mygraph.pdf", width = 11, height = 8 )
plot( x, y )

You can then divide up the space in the pdf using the mfrow parameter like this:

par( mfrow = c(2,2) )

That makes a pdf with four panels available for plotting. Unfortunately, some of the devices take different units than others. For example, I think that X11 uses pixels, while I'm certain that pdf uses inches. If you'd just like to create several devices and plot different things to them, you can use, dev.list(), and

Other devices that might be useful include:

There's a list of all of the devices here.

git: fatal unable to auto-detect email address

Problem solved after I run those commands with sudo

How do I get the selected element by name and then get the selected value from a dropdown using jQuery?

Try this:

$('select[name="' + name + '"] option:selected').val();

This will get the selected value of your menu.

spring autowiring with unique beans: Spring expected single matching bean but found 2

For me it was case of having two beans implementing the same interface. One was a fake ban for the sake of unit test which was conflicting with original bean. If we use


, it still references with suggestionService. So I removed @component and only used


which solved the problem

Difference between os.getenv and os.environ.get

In addition to the answers above:

$ python3 -m timeit -s 'import os' 'os.environ.get("TERM_PROGRAM")'
200000 loops, best of 5: 1.65 usec per loop

$ python3 -m timeit -s 'import os' 'os.getenv("TERM_PROGRAM")'
200000 loops, best of 5: 1.83 usec per loop

Check that an email address is valid on iOS

Good cocoa function:

-(BOOL) NSStringIsValidEmail:(NSString *)checkString
   BOOL stricterFilter = NO; // Discussion
   NSString *stricterFilterString = @"^[A-Z0-9a-z\\._%+-]+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2,4}$";
   NSString *laxString = @"^.+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2}[A-Za-z]*$";
   NSString *emailRegex = stricterFilter ? stricterFilterString : laxString;
   NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
   return [emailTest evaluateWithObject:checkString];

Discussion on Lax vs. Strict -

And because categories are just better, you could also add an interface:

@interface NSString (emailValidation) 
  - (BOOL)isValidEmail;


@implementation NSString (emailValidation)
  BOOL stricterFilter = NO; // Discussion
  NSString *stricterFilterString = @"^[A-Z0-9a-z\\._%+-]+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2,4}$";
  NSString *laxString = @"^.+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2}[A-Za-z]*$";
  NSString *emailRegex = stricterFilter ? stricterFilterString : laxString;
  NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
  return [emailTest evaluateWithObject:self];

And then utilize:

if([@"[email protected]" isValidEmail]) { /* True */ }
if([@"InvalidEmail@notreallyemailbecausenosuffix" isValidEmail]) { /* False */ }

Python dictionary replace values

If you iterate over a dictionary you get the keys, so assuming your dictionary is in a variable called data and you have some function find_definition() which gets the definition, you can do something like the following:

for word in data:
    data[word] = find_definition(word)

Two decimal places using printf( )

Try using a format like %d.%02d

int iAmount = 10050;
printf("The number with fake decimal point is %d.%02d", iAmount/100, iAmount%100);

Another approach is to type cast it to double before printing it using %f like this:

printf("The number with fake decimal point is %0.2f", (double)(iAmount)/100);

My 2 cents :)

How to fix JSP compiler warning: one JAR was scanned for TLDs yet contained no TLDs?

The above solution did not work for me. Instead I simply removed the hash(#) from the last line of the file, to make it work.

# To see debug messages in TldLocationsCache, uncomment the following line:
org.apache.jasper.compiler.TldLocationsCache.level = FINE

The next step is to add the jars that Tomcat 7 is looking for in files just after the following line


What are the advantages and disadvantages of recursion?

To start:


  • It is the unique way of implementing a variable number of nested loops (and the only elegant way of implementing a big constant number of nested loops).


  • Recursive methods will often throw a StackOverflowException when processing big sets. Recursive loops don't have this problem though.


You have wrong database design and you should take a time to read something about database normalization (wikipedia / stackoverflow).

I assume your table looks somewhat like this

| group_id | user_ids | name   |
| 1        | 1,4,6    | group1 |
| 2        | 4,5,1    | group2 |    

so in your table of user groups, each row represents one group and in user_ids column you have set of user ids assigned to that group.

Normalized version of this table would look like this

| id       | name   |
| 1        | group1 |
| 2        | group2 |    

| group_id | user_id |
| 1        | 1       |
| 1        | 4       |
| 1        | 6       |
| 2        | 4       |
| ...      

Then you can easily select all users with assigned group, or all users in group, or all groups of user, or whatever you can think of. Also, your sql query will work:

/* Your query to select assignments */
SELECT * FROM `group_user_assignment` WHERE user_id IN (1,2,3,4);

/* Select only some users */
SELECT * FROM `group_user_assignment` t1
JOIN `group` t2 ON = t1.group_id
WHERE user_id IN (1,4);

/* Select all groups of user */
SELECT * FROM `group_user_assignment` t1
JOIN `group` t2 ON = t1.group_id
WHERE t1.`user_id` = 1;

/* Select all users of group */
SELECT * FROM `group_user_assignment` t1
JOIN `group` t2 ON = t1.group_id
WHERE t1.`group_id` = 1;

/* Count number of groups user is in */
SELECT COUNT(*) AS `groups_count` FROM `group_user_assignment` WHERE `user_id` = 1;

/* Count number of users in group */
SELECT COUNT(*) AS `users_count` FROM `group_user_assignment` WHERE `group_id` = 1;

This way it will be also easier to update database, when you would like to add new assignment, you just simply insert new row in group_user_assignment, when you want to remove assignment you just delete row in group_user_assignment.

In your database design, to update assignments, you would have to get your assignment set from database, process it and update and then write back to database.

Here is sqlFiddle to play with.

Set a:hover based on class

Set a:hover based on class you can simply try:

a.main-nav-item:hover { }

Warning: X may be used uninitialized in this function

You get the warning because you did not assign a value to one, which is a pointer. This is undefined behavior.

You should declare it like this:

Vector* one = malloc(sizeof(Vector));

or like this:

Vector one;

in which case you need to replace -> operator with . like this:

one.a = 12;
one.b = 13;
one.c = -11;

Finally, in C99 and later you can use designated initializers:

Vector one = {
   .a = 12
,  .b = 13
,  .c = -11

Get a DataTable Columns DataType

What you want to use is this property:


The DataType property will set to one of the following:


DataColumn.DataType Property MSDN Reference

Git error: src refspec master does not match any error: failed to push some refs

One classic root cause for this message is:

  • when the repo has been initialized (git init lis4368/assignments),
  • but no commit has ever been made

Ie, if you don't have added and committed at least once, there won't be a local master branch to push to.

Try first to create a commit:

  • either by adding (git add .) then git commit -m "first commit"
    (assuming you have the right files in place to add to the index)
  • or by create a first empty commit: git commit --allow-empty -m "Initial empty commit"

And then try git push -u origin master again.

See "Why do I need to explicitly push a new branch?" for more.

Python: Checking if a 'Dictionary' is empty doesn't seem to work

test_dict = {}
if not test_dict.keys():
    print "Dict is Empty"

Find and replace entire mysql database

Simple Soltion

UPDATE `table_name`
 SET `field_name` = replace(same_field_name, 'unwanted_text', 'wanted_text')

Socket accept - "Too many open files"

Use lsof -u `whoami` | wc -l to find how many open files the user has

How to calculate the inverse of the normal cumulative distribution function in python?

NORMSINV (mentioned in a comment) is the inverse of the CDF of the standard normal distribution. Using scipy, you can compute this with the ppf method of the scipy.stats.norm object. The acronym ppf stands for percent point function, which is another name for the quantile function.

In [20]: from scipy.stats import norm

In [21]: norm.ppf(0.95)
Out[21]: 1.6448536269514722

Check that it is the inverse of the CDF:

In [34]: norm.cdf(norm.ppf(0.95))
Out[34]: 0.94999999999999996

By default, norm.ppf uses mean=0 and stddev=1, which is the "standard" normal distribution. You can use a different mean and standard deviation by specifying the loc and scale arguments, respectively.

In [35]: norm.ppf(0.95, loc=10, scale=2)
Out[35]: 13.289707253902945

If you look at the source code for scipy.stats.norm, you'll find that the ppf method ultimately calls scipy.special.ndtri. So to compute the inverse of the CDF of the standard normal distribution, you could use that function directly:

In [43]: from scipy.special import ndtri

In [44]: ndtri(0.95)
Out[44]: 1.6448536269514722

How to read connection string in .NET Core?

You can do this with the GetConnectionString extension-method:

string conString = Microsoft
   .GetConnectionString(this.Configuration, "DefaultConnection");


or with a structured-class for DI:

public class SmtpConfig
    public string Server { get; set; }
    public string User { get; set; }
    public string Pass { get; set; }
    public int Port { get; set; }


public IConfigurationRoot Configuration { get; }

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
    // services.Configure<SmtpConfig>(Configuration.GetSection("Smtp"));
    Microsoft.Extensions.DependencyInjection.OptionsConfigurationServiceCollectionExtensions.Configure<SmtpConfig>(services, Configuration.GetSection("Smtp"));

And then in the home-controller:

public class HomeController : Controller

    public SmtpConfig SmtpConfig { get; }
    public HomeController(Microsoft.Extensions.Options.IOptions<SmtpConfig> smtpConfig)
        SmtpConfig = smtpConfig.Value;
    } //Action Controller

    public IActionResult Index()
        return View();

with this in appsettings.json:

"ConnectionStrings": {
"DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=aspnet-WebApplica71d622;Trusted_Connection=True;MultipleActiveResultSets=true"

"Smtp": {
    "Server": "",
    "User": "[email protected]",
    "Pass": "123456789",
    "Port": "25"

Error in plot.window(...) : need finite 'xlim' values

I had the same problem. My solution was to make all vectors numeric.

Tomcat 7 "SEVERE: A child container failed during start"

This same issue occurred for me and stack trace

SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[/XXXXSearch]]
    at java.util.concurrent.FutureTask.get(
    at org.apache.catalina.core.ContainerBase.startInternal(
    at org.apache.catalina.core.StandardHost.startInternal(
    at org.apache.catalina.util.LifecycleBase.start(
    at org.apache.catalina.core.ContainerBase$
    at org.apache.catalina.core.ContainerBase$
    at java.util.concurrent.ThreadPoolExecutor.runWorker(
    at java.util.concurrent.ThreadPoolExecutor$
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[/XXXXSearch]]
    at org.apache.catalina.util.LifecycleBase.start(
    ... 6 more
Caused by: java.lang.IllegalStateException: Unable to complete the scan for annotations for web application [/XXXXSearch]. Possible root causes include a too low setting for -Xss and illegal cyclic inheritance dependencies
    at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(
    at org.apache.catalina.startup.ContextConfig.processAnnotationsJar(
    at org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(
    at org.apache.catalina.startup.ContextConfig.processAnnotations(
    at org.apache.catalina.startup.ContextConfig.webConfig(
    at org.apache.catalina.startup.ContextConfig.configureStart(
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(
    at org.apache.catalina.core.StandardContext.startInternal(
    at org.apache.catalina.util.LifecycleBase.start(
    ... 6 more
Caused by: java.lang.StackOverflowError
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(
    at org.apache.catalina.startup.ContextConfig.populateSCIsForCacheEntry(

In my analysis what i found was, this issue is occurred when illegal cyclic inheritance dependencies caused for Tomcat startup annotation processing.

But my project had lot of dependency JARs, and couldn't found which one is responsible for this.

After trying so many unhappy approaches What i did was , I have updated my tomcat plugin to following and ran the same scenario,


Then i was able to find which JAR is caused to this issue ,

Aug 23, 2017 2:32:12 PM org.apache.catalina.startup.ContextConfig processAnnotationsJar
SEVERE: Unable to process Jar entry [cryptix/test/TestLOKI91.class] from Jar [jar:file:/C:/Users/Tharinda/.m2/repository/cryptix/cryptix/1.2.2/cryptix-1.2.2.jar!/] for annotations
    at org.apache.tomcat.util.bcel.classfile.FastDataInputStream.readUnsignedShort(
    at org.apache.tomcat.util.bcel.classfile.ClassParser.readAttributes(
    at org.apache.tomcat.util.bcel.classfile.ClassParser.parse(
    at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(
    at org.apache.catalina.startup.ContextConfig.processAnnotationsJar(
    at org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(
    at org.apache.catalina.startup.ContextConfig.processAnnotations(
    at org.apache.catalina.startup.ContextConfig.webConfig(
    at org.apache.catalina.startup.ContextConfig.configureStart(
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(
    at org.apache.catalina.core.StandardContext.startInternal(
    at org.apache.catalina.util.LifecycleBase.start(
    at org.apache.catalina.core.ContainerBase$
    at org.apache.catalina.core.ContainerBase$
    at java.util.concurrent.ThreadPoolExecutor.runWorker(
    at java.util.concurrent.ThreadPoolExecutor$

Then just solving the issue with cryptix-1.2.2.jar solved this problem.

I strongly recommend to move tomcat8-maven-plugin which seems stable and less buggy at the moment.

Find Java classes implementing an interface

You could also use the Extensible Component Scanner (extcos: and search all classes implementing an interface like so:

Set<Class<? extends MyInterface>> classes = new HashSet<Class<? extends MyInterface>>();

ComponentScanner scanner = new ComponentScanner();
scanner.getClasses(new ComponentQuery() {
    protected void query() {
        from("my.package1", "my.package2").

This works for classes on the file system, within jars and even for those on the JBoss virtual file system. It's further designed to work within standalone applications as well as within any web or application container.

Runnable with a parameter?

You have two options:

  1. Define a named class. Pass your parameter to the constructor of the named class.

  2. Have your anonymous class close over your "parameter". Be sure to mark it as final.

Is JavaScript's "new" keyword considered harmful?

Javascript being dynamic language there a zillion ways to mess up where another language would stop you.

Avoiding a fundamental language feature such as new on the basis that you might mess up is a bit like removing your shiny new shoes before walking through a minefield just in case you might get your shoes muddy.

I use a convention where function names begin with a lower case letter and 'functions' that are actually class definitions begin with a upper case letter. The result is a really quite compelling visual clue that the 'syntax' is wrong:-

var o = MyClass();  // this is clearly wrong.

On top of this good naming habits help. After all functions do things and therefore there should be a verb in its name whereas classes represent objects and are nouns and adjectives with no verb.

var o = chair() // Executing chair is daft.
var o = createChair() // makes sense.

Its interesting how SO's syntax colouring has interpretted the code above.

Count all values in a matrix greater than a value

This is very straightforward with boolean arrays:

p31 = numpy.asarray(o31)
za = (p31 < 200).sum() # p31<200 is a boolean array, so `sum` counts the number of True elements

Output a NULL cell value in Excel

As you've indicated, you can't output NULL in an excel formula. I think this has to do with the fact that the formula itself causes the cell to not be able to be NULL. "" is the next best thing, but sometimes it's useful to use 0.


Based on your comment, you might want to check out this link.

It goes in depth on the graphing issues and what the various values represent, and how to manipulate their output on a chart.

I'm not familiar with VSTO I'm afraid. So I won't be much help there. But if you are really placing formulas in the cell, then there really is no way. ISBLANK() only tests to see if a cell is blank or not, it doesn't have a way to make it blank. It's possible to write code in VBA (and VSTO I imagine) that would run on a worksheet_change event and update the various values instead of using formulas. But that would be cumbersome and performance would take a hit.

Align printf output in Java

A simple solution that springs to mind is to have a String block of spaces:

String indent = "                  "; // 20 spaces.

When printing out a string, compute the actual indent and add it to the end:

String output = "Newspaper";
output += indent.substring(0, indent.length - output.length);

This will mediate the number of spaces to the string, and put them all in the same column.

BigDecimal to string

The BigDecimal can not be a double. you can use Int number. if you want to display exactly own number, you can use the String constructor of BigDecimal .

like this:

BigDecimal bd1 = new BigDecimal("10.0001");

now, you can display bd1 as 10.0001

So simple. GOOD LUCK.

Adding data attribute to DOM

Using .data() will only add data to the jQuery object for that element. In order to add the information to the element itself you need to access that element using jQuery's .attr or native .setAttribute

$('div').attr('data-info', 1);

In order to access an element with the attribute set, you can simply select based on that attribute as you note in your post ($('div[data-info="1"]')), but when you use .data() you cannot. In order to select based on the .data() setting, you would need to use jQuery's filter function.

jsFiddle Demo

$('div').data('info', 1);_x000D_
   return $(this).data('info') == 1; _x000D_
<script src=""></script>_x000D_

Is there a way to define a min and max value for EditText in Android?

There is a small error in Pratik's code. For instance, if a value is 10 and you add a 1 at the beginning to make 110, the filter function would treat the new value as 101.

See below for a fix to this:

public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
    try {
        // Removes string that is to be replaced from destination
        // and adds the new string in.
        String newVal = dest.subSequence(0, dstart)
                // Note that below "toString()" is the only required:
                + source.subSequence(start, end).toString()
                + dest.subSequence(dend, dest.length());
        int input = Integer.parseInt(newVal);
        if (isInRange(min, max, input))
            return null;
    } catch (NumberFormatException nfe) { }
    return "";

SharePoint : How can I programmatically add items to a custom list instance

I had a similar problem and was able to solve it by following the below approach (similar to other answers but needed credentials too),

1- add Microsoft.SharePointOnline.CSOM by tools->NuGet Package Manager->Manage NuGet Packages for solution->Browse-> select and install

2- Add "using Microsoft.SharePoint.Client; "

then the below code

        string siteUrl = "";
        SecureString passWord = new SecureString();

        var password = "Your password here";
        var securePassword = new SecureString();
        foreach (char c in password)
        ClientContext clientContext = new ClientContext(siteUrl);
        clientContext.Credentials = new SharePointOnlineCredentials("[email protected]", securePassword);/*passWord*/
        List oList = clientContext.Web.Lists.GetByTitle("The name of your list here");
        ListItemCreationInformation itemCreateInfo = new ListItemCreationInformation();
        ListItem oListItem = oList.AddItem(itemCreateInfo);
        oListItem["PK"] = "1";
        oListItem["Precinct"] = "Mangere";
        oListItem["Title"] = "Innovation";
        oListItem["Project_x005F_x0020_Name"] = "test from C#";
        oListItem["Project_x005F_x0020_ID"] = "ID_123_from C#";
        oListItem["Project_x005F_x0020_start_x005F_x0020_date"] = "2020-05-01 01:01:01";


Remember that your fields may be different with what you see, for example in my list I see "Project Name", while the actual value is "Project_x005F_x0020_ID". How to get these values (i.e. internal filed values)?

A few approaches:

1- Use MS flow and see them

2- or

3- Use a C# reader and read your sharepoint list

The rest of operations (update/delete):

How to set ssh timeout?

Well, you could use nohup to run whatever you are running on 'non-blocking mode'. So you can just keep checking if whatever it was supposed to run, ran, otherwise exit.

nohup ./ &

echo "Script ended on Feb 15, 2011, 9:20AM" > /tmp/done.txt

So in the second one you just check if the file exists.

MongoDB Show all contents from all collections

Before writing below queries first get into your cmd or PowerShell

mongo             //To get into MongoDB shell
use <Your_dbName>      //For Creating or making use of existing db

To List All Collection Names use any one from below options :-

show collections  //output every collection
show tables
db.getCollectionNames() //shows all collections as a list

To show all collections content or data use below listed code which had been posted by Bruno_Ferreira.

var collections = db.getCollectionNames();
for(var i = 0; i< collections.length; i++) {    
   print('Collection: ' + collections[i]); // print the name of each collection
   db.getCollection(collections[i]).find().forEach(printjson); //and then print     the json of each of its elements

How to check whether a select box is empty using JQuery/Javascript

Another correct way to get selected value would be using this selector:


Best for you!

How to make a shape with left-top round rounded corner and left-bottom rounded corner?

It looks like a bug

Finally I have to write something like this:

 <stroke android:width="3dp"

 <padding android:left="1dp"

 <corners android:radius="1dp"
  android:bottomRightRadius="2dp" android:bottomLeftRadius="0dp" 
  android:topLeftRadius="2dp" android:topRightRadius="0dp"/> 

I have to specify android:bottomRightRadius="2dp" for left-bottom rounded corner (another bug here).

How to get all files under a specific directory in MATLAB?

You can use regexp or strcmp to eliminate . and .. Or you could use the isdir field if you only want files in the directory, not folders.

list=dir(pwd);  %get info of files/folders in current directory
isfile=~[list.isdir]; %determine index of files vs folders
filenames={list(isfile).name}; %create cell array of file names

or combine the last two lines:


For a list of folders in the directory excluding . and ..


From this point, you should be able to throw the code in a nested for loop, and continue searching each subfolder until your dirnames returns an empty cell for each subdirectory.

"Failed to install the following Android SDK packages as some licences have not been accepted" error

This works for me:

yes | ./sdkmanager "platforms;android-28"

yes | ./sdkmanager "build-tools;28.0.3"

yes | ./sdkmanager --licenses

When should I use UNSIGNED and SIGNED INT in MySQL?

Use UNSIGNED for non-negative integers.

jQuery preventDefault() not triggered

Try this one:

   $("div.subtab_left li.notebook a").click(function(e) {
    return false;   

How to set selected value on select using selectpicker plugin from bootstrap

You can set the selected value by calling the val method on the element.

$('.selectpicker').selectpicker('val', 'Mustard');
$('.selectpicker').selectpicker('val', ['Mustard','Relish']);

This will select all items in a multi-select.


details are available on site :

How do malloc() and free() work?

Memory protection has page-granularity and would require kernel interaction

Your example code essentially asks why the example program doesn't trap, and the answer is that memory protection is a kernel feature and applies only to entire pages, whereas the memory allocator is a library feature and it manages .. without enforcement .. arbitrary sized blocks which are often much smaller than pages.

Memory can only be removed from your program in units of pages, and even that is unlikely to be observed.

calloc(3) and malloc(3) do interact with the kernel to get memory, if necessary. But most implementations of free(3) do not return memory to the kernel1, they just add it to a free list that calloc() and malloc() will consult later in order to reuse the released blocks.

Even if a free() wanted to return memory to the system, it would need at least one contiguous memory page in order to get the kernel to actually protect the region, so releasing a small block would only lead to a protection change if it was the last small block in a page.

So your block is there, sitting on the free list. You can almost always access it and nearby memory just as if it were still allocated. C compiles straight to machine code and without special debugging arrangements there are no sanity checks on loads and stores. Now, if you try and access a free block, the behavior is undefined by the standard in order to not make unreasonable demands on library implementators. If you try and access freed memory or meory outside an allocated block, there are various things that can go wrong:

  • Sometimes allocators maintain separate blocks of memory, sometimes they use a header they allocate just before or after (a "footer", I guess) your block, but they just might want to use memory within the block for the purpose of keeping the free list linked together. If so, your reading the block is OK, but its contents may change, and writing to the block would be likely to cause the allocator to misbehave or crash.
  • Naturally, your block may be allocated in the future, and then it is likely to be overwritten by your code or a library routine, or with zeroes by calloc().
  • If the block is reallocated, it may also have its size changed, in which case yet more links or initialization will be written in various places.
  • Obviously you may reference so far out of range that you cross a boundary of one of your program's kernel-known segments, and in this one case you will trap.

Theory of Operation

So, working backwards from your example to the overall theory, malloc(3) gets memory from the kernel when it needs it, and typically in units of pages. These pages are divided or consolidated as the program requires. Malloc and free cooperate to maintain a directory. They coalesce adjacent free blocks when possible in order to be able to provide large blocks. The directory may or may not involve using the memory in freed blocks to form a linked list. (The alternative is a bit more shared-memory and paging-friendly, and it involves allocating memory specifically for the directory.) Malloc and free have little if any ability to enforce access to individual blocks even when special and optional debugging code is compiled into the program.

1. The fact that very few implementations of free() attempt to return memory to the system is not necessarily due to the implementors slacking off. Interacting with the kernel is much slower than simply executing library code, and the benefit would be small. Most programs have a steady-state or increasing memory footprint, so the time spent analyzing the heap looking for returnable memory would be completely wasted. Other reasons include the fact that internal fragmentation makes page-aligned blocks unlikely to exist, and it's likely that returning a block would fragment blocks to either side. Finally, the few programs that do return large amounts of memory are likely to bypass malloc() and simply allocate and free pages anyway.

'adb' is not recognized as an internal or external command, operable program or batch file

just open Android studio and press "Tools" on Top navigation bar

tools->SDK Manager

Where you can get SDK location

Open SDK folder -> platform-tools

Eclipse: All my projects disappeared from Project Explorer

File > Switch Workspace> 'MyWorkSpace'

Eclipse restarts and if you are as lucky as me, the projects are mapped correctly.

In my case I have the developer environment on a shared server with about 10-15 users that may accidentally change things that affects other users.

Tip of the day: Don't do that...

Difference between == and ===

Swift 4: Another example using Unit Tests which only works with ===

Note: Test below fails with ==, works with ===

func test_inputTextFields_Delegate_is_ViewControllerUnderTest() {

        //instantiate viewControllerUnderTest from Main storyboard
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        viewControllerUnderTest = storyboard.instantiateViewController(withIdentifier: "StoryBoardIdentifier") as! ViewControllerUnderTest 
        let _ = viewControllerUnderTest.view

        XCTAssertTrue(viewControllerUnderTest.inputTextField.delegate === viewControllerUnderTest) 

And the class being

class ViewControllerUnderTest: UIViewController, UITextFieldDelegate {
    @IBOutlet weak var inputTextField: UITextField!

    override func viewDidLoad() {
        inputTextField.delegate = self

The error in Unit Tests if you use == is, Binary operator '==' cannot be applied to operands of type 'UITextFieldDelegate?' and 'ViewControllerUnderTest!'

Selecting specific rows and columns from NumPy array


 >>> a[[0,1,3]][:,[0,2]]
array([[ 0,  2],
   [ 4,  6],
   [12, 14]])


>>> a[[0,1,3],::2]
array([[ 0,  2],
   [ 4,  6],
   [12, 14]])

IE6/IE7 css border on select element

IE < 8 does not render the dropdown list itself it just uses the windows control which cannot be styled this way. Beginning from IE 8 this has changed and the styling is now applied. Of course, its market share is rather negligible yet.

Reset all changes after last commit in git

How can I undo every change made to my directory after the last commit, including deleting added files, resetting modified files, and adding back deleted files?

  1. You can undo changes to tracked files with:

    git reset HEAD --hard
  2. You can remove untracked files with:

    git clean -f
  3. You can remove untracked files and directories with:

    git clean -fd

    but you can't undo change to untracked files.

  4. You can remove ignored and untracked files and directories

    git clean -fdx

    but you can't undo change to ignored files.

You can also set clean.requireForce to false:

git config --global --add clean.requireForce false

to avoid using -f (--force) when you use git clean.

Uninstall all installed gems, in OSX?

If you like doing it using ruby:

ruby -e "`gem list`.split(/$/).each { |line| puts `gem uninstall -Iax #{line.split(' ')[0]}` unless line.strip.empty? }"


Open Source Javascript PDF viewer

Well it's not even close to the full spec, but there is a JavaScript and Canvas based PDF viewer out there.

Does Python SciPy need BLAS?

Try using

sudo apt-get install python3-scipy

What should be the sizeof(int) on a 64-bit machine?

Size of a pointer should be 8 byte on any 64-bit C/C++ compiler, but not necessarily size of int.

Set the Value of a Hidden field using JQuery

If you have a hidden field like this

  <asp:HiddenField ID="HiddenField1" runat="server" Value='<%# Eval("VertragNr") %>'/>

Now you can use your value like this


Error - trustAnchors parameter must be non-empty

On Ubuntu 18.04 I needed to use OpenJDK 1.7 for the maintenance of an old project. I downloaded the binary package. But when I executed my script on it I got the same error.

The solution was to remove the cacerts file of the downloaded JDK in the jre/lib/security folder and then to create it as symlink to the systems cacerts file in /etc/ssl/certs/java/:

sudo ln -s /etc/ssl/certs/java/cacerts /path/to/downloaded/java/jre/lib/security/cacerts

Differences in string compare methods in C#

As Ed said, CompareTo is used for sorting.

There is a difference, however, between .Equals and ==.

== resolves to essentially the following code:

if(object.ReferenceEquals(left, null) && 
   object.ReferenceEquals(right, null))
    return true;
if(object.ReferenceEquals(left, null))
    return right.Equals(left);
return left.Equals(right);

The simple reason is the following will throw an exception:

string a = null;
string b = "foo";

bool equal = a.Equals(b);

And the following will not:

string a = null;
string b = "foo";

bool equal = a == b;

How do I check if a directory exists? "is_dir", "file_exists" or both?

I had the same doubt, but see the PHP docu:

You will see that is_dir() has both properties.

Return Values is_dir Returns TRUE if the filename exists and is a directory, FALSE otherwise.

$lookup on ObjectId's in an array

Aggregating with $lookup and subsequent $group is pretty cumbersome, so if (and that's a medium if) you're using node & Mongoose or a supporting library with some hints in the schema, you could use a .populate() to fetch those documents:

var mongoose = require("mongoose"),
    Schema = mongoose.Schema;

var productSchema = Schema({ ... });

var orderSchema = Schema({
  _id     : Number,
  products: [ { type: Schema.Types.ObjectId, ref: "Product" } ]

var Product = mongoose.model("Product", productSchema);
var Order   = mongoose.model("Order", orderSchema);



What is the purpose of "pip install --user ..."?

Why not just put an executable somewhere in my $PATH

~/.local/bin directory is theoretically expected to be in your $PATH.

According to these people it's a bug not adding it in the $PATH when using systemd.

This answer explains it more extensively.

But even if your distro includes the ~/.local/bin directory to the $PATH, it might be in the following form (inside ~/.profile):

if [ -d "$HOME/.local/bin" ] ; then

which would require you to logout and login again, if the directory was not there before.

How to copy and edit files in Android shell?

The most common answer to that is simple: Bundle few apps (busybox?) with your APK (assuming you want to use it within an application). As far as I know, the /data partition is not mounted noexec, and even if you don't want to deploy a fully-fledged APK, you could modify ConnectBot sources to build an APK with a set of command line tools included.

For command line tools, I recommend using crosstool-ng and building a set of statically-linked tools (linked against uClibc). They might be big, but they'll definitely work.

How do you run a crontab in Cygwin on Windows?

The correct syntax to install cron in cygwin as Windows service is to pass -n as argument and not -D:

cygrunsrv --install cron --path /usr/sbin/cron --args -n

-D returns usage error when starting cron in cygwin:


$cygrunsrv --install cron --path /usr/sbin/cron --args -D

$cygrunsrv --start cron

cygrunsrv: Error starting a service: QueryServiceStatus: Win32 error 1062:

The service has not been started.

$cat /var/log/cron.log

cron: unknown option -- D

usage: /usr/sbin/cron [-n] [-x [ext,sch,proc,parc,load,misc,test,bit]]


Below page has a good explanation.

Installing & Configuring the Cygwin Cron Service in Windows:

P.S. I had to run Cygwin64 Terminal on my Windows 10 PC as administrator in order to install cron as Windows service.

How to perform Join between multiple tables in LINQ lambda

take look at this sample code from my project

public static IList<Letter> GetDepartmentLettersLinq(int departmentId)
    IEnumerable<Letter> allDepartmentLetters =
        from allLetter in LetterService.GetAllLetters()
        join allUser in UserService.GetAllUsers() on allLetter.EmployeeID equals allUser.ID into usersGroup
        from user in usersGroup.DefaultIfEmpty()// here is the tricky part
        join allDepartment in DepartmentService.GetAllDepartments() on user.DepartmentID equals allDepartment.ID
        where allDepartment.ID == departmentId
        select allLetter;

    return allDepartmentLetters.ToArray();

in this code I joined 3 tables and I spited join condition from where clause

note: the Services classes are just warped(encapsulate) the database operations

How can I set the default timezone in node.js?

You can take moment timezone. It lets you set your location and also takes care of daylight saving time.

Best way to do a split pane in HTML

Hmm, I came across this property in CSS 3. This might be easier to use.

CSS resize Property

How to use BigInteger?

Actually you can use,

BigInteger sum= new BigInteger("12345");

for creating object for BigInteger class.But the problem here is,you cannot give a variable in the double quotes.So we have to use the valueOf() method and we have to store the answer in that sum again.So we will write,

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

How to map and remove nil values in Ruby

Try using reduce or inject.

[1, 2, 3].reduce([]) { |memo, i|
  if i % 2 == 0
    memo << i


I agree with the accepted answer that we shouldn't map and compact, but not for the same reasons.

I feel deep inside that map then compact is equivalent to select then map. Consider: map is a one-to-one function. If you are mapping from some set of values, and you map, then you want one value in the output set for each value in the input set. If you are having to select before-hand, then you probably don't want a map on the set. If you are having to select afterwards (or compact) then you probably don't want a map on the set. In either case you are iterating twice over the entire set, when a reduce only needs to go once.

Also, in English, you are trying to "reduce a set of integers into a set of even integers".

Check if xdebug is working

you can run this small php code


Copy the whole output page, paste it in this link. Then analyze. It will show if Xdebug is installed or not. And it will give instructions to complete the installation.

How do I check out an SVN project into Eclipse as a Java project?

If it wasn't checked in as a Java Project, you can add the java nature as shown here.

How do I sort a Set to a List in Java?

@Jeremy Stein I wanted to implement same code. As well I wanted to sort the set to list, So instead of using Set I converted set values into List and sort that list by it's one the variable. This code helped me,;

Rename all files in directory from $filename_h to $filename_half?

Another approach can be manually using batch rename option

Right click on the file -> File Custom Commands -> Batch Rename and you can replace h. with half.

This will work for linux based gui using WinSCP etc

jQuery '.each' and attaching '.click' event

No need to use .each. click already binds to all div occurrences.

$('div').click(function(e) {

See Demo

Note: use hard binding such as .click to make sure dynamically loaded elements don't get bound.

Update statement using with clause

You can always do something like this:

update  mytable t
set     SomeColumn = c.ComputedValue
from    (select *, 42 as ComputedValue from mytable where id = 1) c
where = 

You can now also use with statement inside update

update  mytable t
set     SomeColumn = c.ComputedValue
from    (with abc as (select *, 43 as ComputedValue_new from mytable where id = 1
         select *, 42 as ComputedValue, abc.ComputedValue_new  from mytable n1
           inner join abc on c
where = 

How to count number of unique values of a field in a tab-delimited text file?

# COLUMN is integer column number
# INPUT_FILE is input file name

cut -f ${COLUMN} < ${INPUT_FILE} | sort -u | wc -l

How to store date/time and timestamps in UTC time zone with JPA and Hibernate

There are several timezones in operation here:

  1. Java's Date classes (util and sql), which have implicit timezones of UTC
  2. The timezone your JVM is running in, and
  3. the default timezone of your database server.

All of these can be different. Hibernate/JPA has a severe design deficiency in that a user cannot easily ensure that timezone information is preserved in the database server (which allows reconstruction of correct times and dates in the JVM).

Without the ability to (easily) store timezone using JPA/Hibernate then information is lost and once information is lost it becomes expensive to construct it (if at all possible).

I would argue that it is better to always store timezone information (should be the default) and users should then have the optional ability to optimize the timezone away (although it only really affects display, there is still an implicit timezone in any date).

Sorry, this post doesn't provide a work-around (that's been answered elsewhere) but it is a rationalization of why always storing timezone information around is important. Unfortunately it seems many Computer Scientists and programming practitioners argue against the need for timezones simply because they don't appreciate the "loss of information" perspective and how that makes things like internationalization very difficult - which is very important these days with web sites accessible by clients and people in your organization as they move around the world.

Postgres ERROR: could not open file for reading: Permission denied

You must grant the pg_read_server_files permission to the user if you are not using postgres superuser.


GRANT pg_read_server_files TO my_user WITH ADMIN OPTION;

How to create a new instance from a class object in Python

Just call the "type" built in using three parameters, like this:

ClassName = type("ClassName", (Base1, Base2,...), classdictionary)

update as stated in the comment bellow this is not the answer to this question at all. I will keep it undeleted, since there are hints some people get here trying to dynamically create classes - which is what the line above does.

To create an object of a class one has a reference too, as put in the accepted answer, one just have to call the class:

instance = ClassObject()

The mechanism for instantiation is thus:

Python does not use the new keyword some languages use - instead it's data model explains the mechanism used to create an instantance of a class when it is called with the same syntax as any other callable:

Its class' __call__ method is invoked (in the case of a class, its class is the "metaclass" - which is usually the built-in type). The normal behavior of this call is to invoke the (pseudo) static __new__ method on the class being instantiated, followed by its __init__. The __new__ method is responsible for allocating memory and such, and normally is done by the __new__ of object which is the class hierarchy root.

So calling ClassObject() invokes (which normally will be type.__call__) this __call__ method will receive ClassObject itself as the first parameter - a Pure Python implementation would be like this: (the cPython version is of course, done in C, and with lots of extra code for cornercases and optimizations)

class type:
    def __call__(cls, *args, **kw):
          constructor = getattr(cls, "__new__")
          instance = constructor(cls) if constructor is object.__new__ else constructor(cls, *args, **kw)
          instance.__init__(cls, *args, **kw)
          return instance

(I don't recall seeing on the docs the exact justification (or mechanism) for suppressing extra parameters to the root __new__ and passing it to other classes - but it is what happen "in real life" - if object.__new__ is called with any extra parameters it raises a type error - however, any custom implementation of a __new__ will get the extra parameters normally)

python-dev installation error: ImportError: No module named apt_pkg

Make sure you have a working python-apt package. You could try and remove and install that package again to fix the problem with not being located.

apt-get install python-apt

Getting net::ERR_UNKNOWN_URL_SCHEME while calling telephone number from HTML page in Android

I had this issue occurring with mailto: and tel: links inside an iframe (in Chrome, not a webview). Clicking the links would show the grey "page not found" page and inspecting the page showed it had a ERR_UNKNOWN_URL_SCHEME error.

Adding target="_blank", as suggested by this discussion of the issue fixed the problem for me.

SVN Commit specific files

try this script..

for f in `svn st|grep -v ^\?|sed s/.\ *//`; 
     do LIST="${LIST} $f $NULL on"; 
dialog --checklist "Select files to commit" 30 60 30 $LIST 2>/tmp/svnlist.txt
svn ci `cat /tmp/svnlist.txt|sed 's/"//g'`

Auto height of div

As stated earlier by Jamie Dixon, a floated <div> is taken out of normal flow. All content that is still within normal flow will ignore it completely and not make space for it.

Try putting a different colored border border:solid 1px orange; around each of your <div> elements to see what they're doing. You might start by removing the floats and putting some dummy text inside the div. Then style them one at a time to get the desired layout.

JavaScript get element by name

Method document.getElementsByName returns an array of elements. You should select first, for example.


Why does "return list.sort()" return None, not the list?

Python has two kinds of sorts: a sort method (or "member function") and a sort function. The sort method operates on the contents of the object named -- think of it as an action that the object is taking to re-order itself. The sort function is an operation over the data represented by an object and returns a new object with the same contents in a sorted order.

Given a list of integers named l the list itself will be reordered if we call l.sort():

>>> l = [1, 5, 2341, 467, 213, 123]
>>> l.sort()
>>> l
[1, 5, 123, 213, 467, 2341]

This method has no return value. But what if we try to assign the result of l.sort()?

>>> l = [1, 5, 2341, 467, 213, 123]
>>> r = l.sort()
>>> print(r)

r now equals actually nothing. This is one of those weird, somewhat annoying details that a programmer is likely to forget about after a period of absence from Python (which is why I am writing this, so I don't forget again).

The function sorted(), on the other hand, will not do anything to the contents of l, but will return a new, sorted list with the same contents as l:

>>> l = [1, 5, 2341, 467, 213, 123]
>>> r = sorted(l)
>>> l
[1, 5, 2341, 467, 213, 123]
>>> r
[1, 5, 123, 213, 467, 2341]

Be aware that the returned value is not a deep copy, so be cautious about side-effecty operations over elements contained within the list as usual:

>>> spam = [8, 2, 4, 7]
>>> eggs = [3, 1, 4, 5]
>>> l = [spam, eggs]
>>> r = sorted(l)
>>> l
[[8, 2, 4, 7], [3, 1, 4, 5]]
>>> r
[[3, 1, 4, 5], [8, 2, 4, 7]]
>>> spam.sort()
>>> eggs.sort()
>>> l
[[2, 4, 7, 8], [1, 3, 4, 5]]
>>> r
[[1, 3, 4, 5], [2, 4, 7, 8]]

Get Context in a Service

Service extends ContextWrapper which extends Context. Hence the Service is a Context. Use 'this' keyword in the service.

How to find MAC address of an Android device programmatically

Recent update from

Don't work with MAC addresses MAC addresses are globally unique, not user-resettable, and survive factory resets. For these reasons, it's generally not recommended to use MAC address for any form of user identification. Devices running Android 10 (API level 29) and higher report randomized MAC addresses to all apps that aren't device owner apps.

Between Android 6.0 (API level 23) and Android 9 (API level 28), local device MAC addresses, such as Wi-Fi and Bluetooth, aren't available via third-party APIs. The WifiInfo.getMacAddress() method and the BluetoothAdapter.getDefaultAdapter().getAddress() method both return 02:00:00:00:00:00.

Additionally, between Android 6.0 and Android 9, you must hold the following permissions to access MAC addresses of nearby external devices available via Bluetooth and Wi-Fi scans:

Method/Property Permissions Required



Display curl output in readable JSON format in Unix shell script

I am guessing that you want to prettify the JSON output. That could be achieved using python:

curl http://localhost:8880/test.json | python -mjson.tool > out.json

Can I load a .NET assembly at runtime and instantiate a type knowing only the name?

Yes. You need to use Assembly.LoadFrom to load the assembly into memory, then you can use Activator.CreateInstance to create an instance of your preferred type. You'll need to look the type up first using reflection. Here is a simple example:

Assembly assembly = Assembly.LoadFrom("MyNice.dll");

Type type = assembly.GetType("MyType");

object instanceOfMyType = Activator.CreateInstance(type);


When you have the assembly file name and the type name, you can use Activator.CreateInstance(assemblyName, typeName) to ask the .NET type resolution to resolve that into a type. You could wrap that with a try/catch so that if it fails, you can perform a search of directories where you may specifically store additional assemblies that otherwise might not be searched. This would use the preceding method at that point.

What is the difference between Dim, Global, Public, and Private as Modular Field Access Modifiers?

Dim and Private work the same, though the common convention is to use Private at the module level, and Dim at the Sub/Function level. Public and Global are nearly identical in their function, however Global can only be used in standard modules, whereas Public can be used in all contexts (modules, classes, controls, forms etc.) Global comes from older versions of VB and was likely kept for backwards compatibility, but has been wholly superseded by Public.

onchange equivalent in angular2

@Mark Rajcok gave a great solution for ion projects that include a range type input.

In any other case of non ion projects I will suggest this:


<input type="text" name="points" #points maxlength="8" [(ngModel)]="range" (ngModelChange)="range=saverange($event, points)">


    onChangeAchievement(eventStr: string, eRef): string {

      //Do something (some manipulations) on input and than return it to be saved:

       //In case you need to force of modifing the Element-Reference value on-focus of input:
       var eventStrToReplace = eventStr.replace(/[^0-9,eE\.\+]+/g, "");
       if (eventStr != eventStrToReplace) {
           eRef.value = eventStrToReplace;

      return this.getNumberOnChange(eventStr);


The idea here:

  1. Letting the (ngModelChange) method to do the Setter job:

    (ngModelChange)="range=saverange($event, points)

  2. Enabling direct access to the native Dom element using this call:

    eRef.value = eventStrToReplace;

Connect multiple devices to one device via Bluetooth

Yes you can do so and I have created a library for the same.
This allows you to connect up-to four devices to the main server device creating different channels for each client and running interactions on different threads.
To use this library simple add compile com.mdg.androble:library:0.1.2 in dependency section of your build.gradle .

Run ScrollTop with offset of element by ID

var top = ($(".apps_intro_wrapper_inner").offset() || { "top": NaN }).top;   
if (!isNaN(top)) {
$("#app_scroler").click(function () {   
$('html, body').animate({
            scrollTop: top
        }, 100);

if you want to scroll a little above or below from specific div that add value to the top like I add 800

var top = ($(".apps_intro_wrapper_inner").offset() || { "top": NaN }).top + 800;

Using CSS to align a button bottom of the screen using relative positions

<button style="position: absolute; left: 20%; right: 20%; bottom: 5%;"> Button </button>

How to make node.js require absolute? (instead of relative)

I don't think you need to solve this in the manner you described. Just sed if you want to change the same string in a large amount of files. In your example,

find . -name "*.js" -exec sed -i 's/\.\.\/\.\.\//\.\.\//g' {} +

would have ../../ changed to ../

Alternatively, you can require a configuration file that stores a variable containing the path to the library. If you store the following as config.js in the example directory

var config = {};
config.path = '../../';

and in your example file

myConfiguration = require('./config');
express = require(config.path);

You'll be able to control the configuration for every example from one file.

It's really just personal preference.

How can I control the width of a label tag?

label {
  display: inline-block;


label {
  display: inline-flex;


label {
  display: inline-table;

Create a directly-executable cross-platform GUI app using Python

PySimpleGUI wraps tkinter and works on Python 3 and 2.7. It also runs on Qt, WxPython and in a web browser, using the same source code for all platforms.

You can make custom GUIs that utilize all of the same widgets that you find in tkinter (sliders, checkboxes, radio buttons, ...). The code tends to be very compact and readable.

#!/usr/bin/env python
import sys
if sys.version_info[0] >= 3:
    import PySimpleGUI as sg
    import PySimpleGUI27 as sg

layout = [[ sg.Text('My Window') ],
          [ sg.Button('OK')]]

window = sg.Window('My window').Layout(layout)
button, value = window.Read()

Image created from posted PySimpleGUI code

As explained in the PySimpleGUI Documentation, to build the .EXE file you run:

pyinstaller -wF

Get rid of "The value for annotation attribute must be a constant expression" message

This is what a constant expression in Java looks like:

package com.mycompany.mypackage;

public class MyLinks {
  // constant expression
  public static final String GUESTBOOK_URL = "/guestbook";

You can use it with annotations as following:

import com.mycompany.mypackage.MyLinks;

@WebServlet(urlPatterns = {MyLinks.GUESTBOOK_URL})
public class GuestbookServlet extends HttpServlet {
  // ...

Cannot install packages inside docker Ubuntu image

From the docs in May 2017 2018 2019 2020

Always combine RUN apt-get update with apt-get install in the same RUN statement, for example

RUN apt-get update && apt-get install -y package-bar


Using apt-get update alone in a RUN statement causes caching issues and subsequent apt-get install instructions fail.


Using RUN apt-get update && apt-get install -y ensures your Dockerfile installs the latest package versions with no further coding or manual intervention. This technique is known as “cache busting”.

How do I iterate over an NSArray?

Add each method in your NSArray category, you gonna need it a lot

Code taken from ObjectiveSugar

- (void)each:(void (^)(id object))block {
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

Difference between SelectedItem, SelectedValue and SelectedValuePath

inspired by this question I have written a blog along with the code snippet here. Below are some of the excerpts from the blog

SelectedItem – Selected Item helps to bind the actual value from the DataSource which will be displayed. This is of type object and we can bind any type derived from object type with this property. Since we will be using the MVVM binding for our combo boxes in that case this is the property which we can use to notify VM that item has been selected.

SelectedValue and SelectedValuePath – These are the two most confusing and misinterpreted properties for combobox. But these properties come to rescue when we want to bind our combobox with the value from already created object. Please check my last scenario in the following list to get a brief idea about the properties.

How to use putExtra() and getExtra() for string data

Intent intent = new Intent(view.getContext(), ApplicationActivity.class);
                        intent.putExtra("int", intValue);
                        intent.putExtra("Serializable", object);
                        intent.putExtra("String", stringValue);
                        intent.putExtra("parcelable", parObject);


Intent intent = getIntent();
Bundle bundle = intent.getExtras();

if(bundle != null){
   int mealId = bundle.getInt("int");
   Object object = bundle.getSerializable("Serializable");
   String string = bundle.getString("String");
   T string = <T>bundle.getString("parcelable");

Fill username and password using selenium in python

from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from import Select
from import WebDriverWait

# If you want to open Chrome
driver = webdriver.Chrome()
# If you want to open Firefox
driver = webdriver.Firefox()

username = driver.find_element_by_id("username")
password = driver.find_element_by_id("password")

Overlay normal curve to histogram in R

Here's a nice easy way I found:

h <- hist(g, breaks = 10, density = 10,
          col = "lightgray", xlab = "Accuracy", main = "Overall") 
xfit <- seq(min(g), max(g), length = 40) 
yfit <- dnorm(xfit, mean = mean(g), sd = sd(g)) 
yfit <- yfit * diff(h$mids[1:2]) * length(g) 

lines(xfit, yfit, col = "black", lwd = 2)

Determining if an Object is of primitive type

you could determine if an object is wrapper type by beneath statements:


and you could also determine a primitive object by using the isPrimitive() method

Eclipse : Failed to connect to remote VM. Connection refused.

when you have Failed to connect to remote VM Connection refused error, restart your eclipse

Determine Pixel Length of String in Javascript/jQuery?

The contexts used for HTML Canvases have a built-in method for checking the size of a font. This method returns a TextMetrics object, which has a width property that contains the width of the text.

function getWidthOfText(txt, fontname, fontsize){
    if(getWidthOfText.c === undefined){
    var fontspec = fontsize + ' ' + fontname;
    if(getWidthOfText.ctx.font !== fontspec)
        getWidthOfText.ctx.font = fontspec;
    return getWidthOfText.ctx.measureText(txt).width;

Or, as some of the other users have suggested, you can wrap it in a span element:

function getWidthOfText(txt, fontname, fontsize){
    if(getWidthOfText.e === undefined){
        getWidthOfText.e = document.createElement('span'); = "none";
    if( !== fontsize) = fontsize;
    if( !== fontname) = fontname;
    getWidthOfText.e.innerText = txt;
    return getWidthOfText.e.offsetWidth;

EDIT 2020: added font name+size caching at Igor Okorokov's suggestion.

SignalR Console app example

To build on @dyslexicanaboko's answer for dotnet core, here is a client console application:

Create a helper class:

using System;
using Microsoft.AspNetCore.SignalR.Client;

namespace com.stackoverflow.SignalRClientConsoleApp
    public class SignalRConnection
        public async void Start()
            var url = "http://signalr-server-url/hubname";

            var connection = new HubConnectionBuilder()

            // receive a message from the hub
            connection.On<string, string>("ReceiveMessage", (user, message) => OnReceiveMessage(user, message));

            var t = connection.StartAsync();


            // send a message to the hub
            await connection.InvokeAsync("SendMessage", "ConsoleApp", "Message from the console app");

        private void OnReceiveMessage(string user, string message)
            Console.WriteLine($"{user}: {message}");


Then implement in your console app's entry point:

using System;

namespace com.stackoverflow.SignalRClientConsoleApp
    class Program
        static void Main(string[] args)
            var signalRConnection = new SignalRConnection();


How can I solve ORA-00911: invalid character error?

I'm using a 3rd party program that executes Oracle SQL and I encountered this error. Prior to a SELECT statement, I had some commented notes that included special characters. Removing the comments resolved the issue.

Return multiple values from a SQL Server function

Erland Sommarskog has an exhaustive post about passing data in SQL Server located here:

He covers SQL Server 2000, 2005, and 2008, and it should probably be read in its full detail as there is ample coverage of each method's advantages and drawbacks. However, here are the highlights of the article (frozen in time as of July 2015) for the sake of providing search terms that can be used to look greater details:

This article tackles two related questions:

  • How can I use the result set from one stored procedure in another, also expressed as How can I use the result set from a stored
    procedure in a SELECT statement?
  • How can I pass a table data in a parameter from one stored procedure to another?

OUTPUT Parameters

  • Not generally applicable, but sometimes overlooked.

Table-valued Functions

  • Often the best choice for output-only, but there are several restrictions.
  • Examples:
    • Inline Functions: Use this to reuse a single SELECT.
    • Multi-statement Functions: When you need to encapsulate more complex logic.

Using a Table

  • The most general solution. My favoured choice for input/output scenarios.
  • Examples:
    • Sharing a Temp Table: Mainly for a single pair of caller/callee.
    • Process-keyed Table: Best choice for many callers to the same callee.
    • Global Temp Tables: A variation of process-keyed.

Table-valued Parameters

  • Req. Version: SQL 2008
  • Mainly useful when passing data from a client.


  • Deceivingly appealing, but should be used sparingly.

Using the CLR

  • Req. Version: SQL 2005
  • Complex, but useful as a last resort when INSERT-EXEC does not work.


  • Tricky with many pitfalls. Discouraged.

Using XML

  • Req. Version: SQL 2005
  • A bit of a kludge, but not without advantages.

Using Cursor Variables

  • Not recommendable.

How to generate XML file dynamically using PHP?

To create an XMLdocument in PHP you should instance a DOMDocument class, create child nodes and append these nodes in the correct branch of the document tree.

For reference you can read

Now we will take a quick tour of the code below.

  • at line 2 we create an empty xml document (just specify xml version (1.0) and encoding (utf8))
  • now we need to populate the xml tree:
    • We have to create an xmlnode (line 5)
    • and we have to append this in the correct position. We are creating the root so we append this directly to the domdocument.
    • Note create element append the element to the node and return the node inserted, we save this reference to append the track nodes to the root node (incidentally called xml).

These are the basics, you can create and append a node in just a line (13th, for example), you can do a lot of other things with the dom api. It is up to you.

    /* create a dom document with encoding utf8 */
    $domtree = new DOMDocument('1.0', 'UTF-8');

    /* create the root element of the xml tree */
    $xmlRoot = $domtree->createElement("xml");
    /* append it to the document created */
    $xmlRoot = $domtree->appendChild($xmlRoot);

    $currentTrack = $domtree->createElement("track");
    $currentTrack = $xmlRoot->appendChild($currentTrack);

    /* you should enclose the following two lines in a cicle */
    $currentTrack->appendChild($domtree->createElement('title','title of song1.mp3'));

    $currentTrack->appendChild($domtree->createElement('title','title of song2.mp3'));

    /* get the xml printed */
    echo $domtree->saveXML();

Edit: Just one other hint: The main advantage of using an xmldocument (the dom document one or the simplexml one) instead of printing the xml,is that the xmltree is searchable with xpath query

What is "pom" packaging in maven?

pom packaging is simply a specification that states the primary artifact is not a war or jar, but the pom.xml itself.

Often it is used in conjunction with "modules" which are typically contained in sub-directories of the project in question; however, it may also be used in certain scenarios where no primary binary was meant to be built, all the other important artifacts have been declared as secondary artifacts

Think of a "documentation" project, the primary artifact might be a PDF, but it's already built, and the work to declare it as a secondary artifact might be desired over the configuration to tell maven how to build a PDF that doesn't need compiled.

How can I get last characters of a string

EDIT: As others have pointed out, use slice(-5) instead of substr. However, see the .split().pop() solution at the bottom of this answer for another approach.

Original answer:

You'll want to use the Javascript string method .substr() combined with the .length property.

var id = "ctl03_Tabs1";
var lastFive = id.substr(id.length - 5); // => "Tabs1"
var lastChar = id.substr(id.length - 1); // => "1"

This gets the characters starting at id.length - 5 and, since the second argument for .substr() is omitted, continues to the end of the string.

You can also use the .slice() method as others have pointed out below.

If you're simply looking to find the characters after the underscore, you could use this:

var tabId = id.split("_").pop(); // => "Tabs1"

This splits the string into an array on the underscore and then "pops" the last element off the array (which is the string you want).

Find the min/max element of an array in JavaScript

.apply is often used when the intention is to invoke a variadic function with a list of argument values, e.g.

The Math.max([value1[,value2, ...]]) function returns the largest of zero or more numbers.

Math.max(10, 20); // 20
Math.max(-10, -20); // -10
Math.max(-10, 20); // 20

The Math.max() method doesn't allow you to pass in an array. If you have a list of values of which you need to get the largest, you would normally call this function using Function.prototype.apply(), e.g.

Math.max.apply(null, [10, 20]); // 20
Math.max.apply(null, [-10, -20]); // -10
Math.max.apply(null, [-10, 20]); // 20

However, as of the ECMAScript 6 you can use the spread operator:

The spread operator allows an expression to be expanded in places where multiple arguments (for function calls) or multiple elements (for array literals) are expected.

Using the spread operator, the above can be rewritten as such:

Math.max(...[10, 20]); // 20
Math.max(...[-10, -20]); // -10
Math.max(...[-10, 20]); // 20

When calling a function using the variadic operator, you can even add additional values, e.g.

Math.max(...[10, 20], 50); // 50
Math.max(...[-10, -20], 50); // 50


Spread operator enables you to use the array literal syntax to create new arrays in situations where in ES5 you would need to fall back to imperative code, using a combination of push, splice, etc.

let foo = ['b', 'c'];
let bar = ['a',, 'd', 'e']; // ['a', 'b', 'c', 'd', 'e']

Google access token expiration time

Have a look at:

It says:

Other parameters included in the response include expires_in and token_type. These parameters describe the lifetime of the token in seconds...

Access IP Camera in Python OpenCV

This works with my IP camera:

import cv2

#print("Before URL")
cap = cv2.VideoCapture('rtsp://admin:[email protected]/H264?ch=1&subtype=0')
#print("After URL")

while True:

    #print('About to start the Read command')
    ret, frame =
    #print('About to show frame of Video.')

    if cv2.waitKey(1) & 0xFF == ord('q'):


I found the Stream URL in the Camera's Setup screen: IP Camera Setup Screen

Note that I added the Username (admin) and Password (123456) of the camera and ended it with an @ symbol before the IP address in the URL (admin:123456@)

Is there a way to use two CSS3 box shadows on one element?

You can comma-separate shadows:

box-shadow: inset 0 2px 0px #dcffa6, 0 2px 5px #000;

Soft Edges using CSS?

Another option is to use one of my personal favorite CSS tools: box-shadow.

A box shadow is really a drop-shadow on the node. It looks like this:

-moz-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
-webkit-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
box-shadow: 1px 2px 3px rgba(0,0,0,.5);

The arguments are:

1px: Horizontal offset of the effect. Positive numbers shift it right, negative left.
2px: Vertical offset of the effect. Positive numbers shift it down, negative up.
3px: The blur effect.  0 means no blur.
color: The color of the shadow.

So, you could leave your current design, and add a box-shadow like:

box-shadow: 0px -2px 2px rgba(34,34,34,0.6);

This should give you a 'blurry' top-edge.

This website will help with more information:

Automatic date update in a cell when another cell's value changes (as calculated by a formula)

You could fill the dependend cell (D2) by a User Defined Function (VBA Macro Function) that takes the value of the C2-Cell as input parameter, returning the current date as ouput.

Having C2 as input parameter for the UDF in D2 tells Excel that it needs to reevaluate D2 everytime C2 changes (that is if auto-calculation of formulas is turned on for the workbook).


Here is some code:

For the UDF:

    Public Function UDF_Date(ByVal data) As Date

        UDF_Date = Now()

    End Function

As Formula in D2:


You will have to give the D2-Cell a Date-Time Format, or it will show a numeric representation of the date-value.

And you can expand the formula over the desired range by draging it if you keep the C2 reference in the D2-formula relative.

Note: This still might not be the ideal solution because every time Excel recalculates the workbook the date in D2 will be reset to the current value. To make D2 only reflect the last time C2 was changed there would have to be some kind of tracking of the past value(s) of C2. This could for example be implemented in the UDF by providing also the address alonside the value of the input parameter, storing the input parameters in a hidden sheet, and comparing them with the previous values everytime the UDF gets called.


Here is a sample implementation of an UDF that tracks the changes of the cell values and returns the date-time when the last changes was detected. When using it, please be aware that:

  • The usage of the UDF is the same as described above.

  • The UDF works only for single cell input ranges.

  • The cell values are tracked by storing the last value of cell and the date-time when the change was detected in the document properties of the workbook. If the formula is used over large datasets the size of the file might increase considerably as for every cell that is tracked by the formula the storage requirements increase (last value of cell + date of last change.) Also, maybe Excel is not capable of handling very large amounts of document properties and the code might brake at a certain point.

  • If the name of a worksheet is changed all the tracking information of the therein contained cells is lost.

  • The code might brake for cell-values for which conversion to string is non-deterministic.

  • The code below is not tested and should be regarded only as proof of concept. Use it at your own risk.

    Public Function UDF_Date(ByVal inData As Range) As Date
        Dim wb As Workbook
        Dim dProps As DocumentProperties
        Dim pValue As DocumentProperty
        Dim pDate As DocumentProperty
        Dim sName As String
        Dim sNameDate As String
        Dim bDate As Boolean
        Dim bValue As Boolean
        Dim bChanged As Boolean
        bDate = True
        bValue = True
        bChanged = False
        Dim sVal As String
        Dim dDate As Date
        sName = inData.Address & "_" & inData.Worksheet.Name
        sNameDate = sName & "_dat"
        sVal = CStr(inData.Value)
        dDate = Now()
        Set wb = inData.Worksheet.Parent
        Set dProps = wb.CustomDocumentProperties
    On Error Resume Next
        Set pValue = dProps.Item(sName)
        If Err.Number <> 0 Then
            bValue = False
        End If
    On Error GoTo 0
        If Not bValue Then
            bChanged = True
            Set pValue = dProps.Add(sName, False, msoPropertyTypeString, sVal)
            bChanged = pValue.Value <> sVal
            If bChanged Then
                pValue.Value = sVal
            End If
        End If
    On Error Resume Next
        Set pDate = dProps.Item(sNameDate)
        If Err.Number <> 0 Then
            bDate = False
        End If
    On Error GoTo 0
        If Not bDate Then
            Set pDate = dProps.Add(sNameDate, False, msoPropertyTypeDate, dDate)
        End If
        If bChanged Then
            pDate.Value = dDate
            dDate = pDate.Value
        End If
        UDF_Date = dDate
     End Function

Make the insertion of the date conditional upon the range.

This has an advantage of not changing the dates unless the content of the cell is changed, and it is in the range C2:C2, even if the sheet is closed and saved, it doesn't recalculate unless the adjacent cell changes.

Adapted from this tip and @Paul S answer

Private Sub Worksheet_Change(ByVal Target As Range)
 Dim R1 As Range
 Dim R2 As Range
 Dim InRange As Boolean
    Set R1 = Range(Target.Address)
    Set R2 = Range("C2:C20")
    Set InterSectRange = Application.Intersect(R1, R2)

  InRange = Not InterSectRange Is Nothing
     Set InterSectRange = Nothing
   If InRange = True Then
     R1.Offset(0, 1).Value = Now()
   End If
     Set R1 = Nothing
     Set R2 = Nothing
 End Sub

Intersection and union of ArrayLists in Java

Intersection of two list of different object based on common key - Java 8

 private List<User> intersection(List<User> users, List<OtherUser> list) {

                .flatMap(OtherUser ->
                        .filter(user -> user.getId()

Could not find an implementation of the query pattern

I had the same error as described by title, but for me it was simply installing Microsoft access 12.0 oledb redistributable to use with LinqToExcel.

How to use string.substr() function?

substr(i,j) means that you start from the index i (assuming the first index to be 0) and take next j chars. It does not mean going up to the index j.

Can I store images in MySQL

Yes, you can store images in the database, but it's not advisable in my opinion, and it's not general practice.

A general practice is to store images in directories on the file system and store references to the images in the database. e.g. path to the image,the image name, etc.. Or alternatively, you may even store images on a content delivery network (CDN) or numerous hosts across some great expanse of physical territory, and store references to access those resources in the database.

Images can get quite large, greater than 1MB. And so storing images in a database can potentially put unnecessary load on your database and the network between your database and your web server if they're on different hosts.

I've worked at startups, mid-size companies and large technology companies with 400K+ employees. In my 13 years of professional experience, I've never seen anyone store images in a database. I say this to support the statement it is an uncommon practice.

Using Java 8's Optional with Stream::flatMap

Null is supported by the Stream provided My library AbacusUtil. Here is code:

Stream.of(things).map(e -> resolve(e).orNull()).skipNull().first();

Angular2 http.get() ,map(), subscribe() and observable pattern - basic understanding


Observables in short tackles asynchronous processing and events. Comparing to promises this could be described as observables = promises + events.

What is great with observables is that they are lazy, they can be canceled and you can apply some operators in them (like map, ...). This allows to handle asynchronous things in a very flexible way.

A great sample describing the best the power of observables is the way to connect a filter input to a corresponding filtered list. When the user enters characters, the list is refreshed. Observables handle corresponding AJAX requests and cancel previous in-progress requests if another one is triggered by new value in the input. Here is the corresponding code:

    .switchMap(data => this.httpService.getListValues(data))
    .subscribe(data => console.log('new list values', data));

(textValue is the control associated with the filter input).

Here is a wider description of such use case: How to watch for form changes in Angular 2?.

There are two great presentations at AngularConnect 2015 and EggHead:

Christoph Burgdorf also wrote some great blog posts on the subject:

In action

In fact regarding your code, you mixed two approaches ;-) Here are they:

  • Manage the observable by your own. In this case, you're responsible to call the subscribe method on the observable and assign the result into an attribute of the component. You can then use this attribute in the view for iterate over the collection:

      template: `
        <h1>My Friends</h1>
          <li *ngFor="#frnd of result">
            {{}} is {{frnd.age}} years old.
    export class FriendsList implement OnInit, OnDestroy {
      constructor(http: Http) {
      ngOnInit() {
        this.friendsObservable = http.get('friends.json')
                      .map(response => response.json())
                      .subscribe(result => this.result = result);
       ngOnDestroy() {

    Returns from both get and map methods are the observable not the result (in the same way than with promises).

  • Let manage the observable by the Angular template. You can also leverage the async pipe to implicitly manage the observable. In this case, there is no need to explicitly call the subscribe method.

      template: `
        <h1>My Friends</h1>
          <li *ngFor="#frnd of (result | async)">
            {{}} is {{frnd.age}} years old.
    export class FriendsList implement OnInit {
      constructor(http: Http) {
      ngOnInit() {
        this.result = http.get('friends.json')
                      .map(response => response.json());

You can notice that observables are lazy. So the corresponding HTTP request will be only called once a listener with attached on it using the subscribe method.

You can also notice that the map method is used to extract the JSON content from the response and use it then in the observable processing.

Hope this helps you, Thierry

SQL Query To Obtain Value that Occurs more than once

For postgresql:

SELECT * AS rec 
    SELECT lastname, COUNT(*) AS counter 
    FROM students 
    GROUP BY lastname) AS tbl 
WHERE counter > 1;

Getting the client IP address: REMOTE_ADDR, HTTP_X_FORWARDED_FOR, what else could be useful?

It depends on the nature of your site.

I happen to work on a bit of software where IP tracking is important, and within a field consumed by parter sites I'd guess some 20% - 40% of requests are either detectably spoofed IPs or headers blanked out, depending on the time of day and where they came from. For a site which gets organic traffic (i.e. not through partners) I'd expect a much higher ratio of good IPs.

As Kosi said, be careful what you're doing with this - IPs are in no way a reliable way to identify unique visitors.

Ruby get object keys as array

Use the keys method: {"apple" => "fruit", "carrot" => "vegetable"}.keys == ["apple", "carrot"]

How to use If Statement in Where Clause in SQL?

  FROM Customer
 WHERE (I.IsClose=@ISClose OR @ISClose is NULL)  
   AND (C.FirstName like '%'+@ClientName+'%' or @ClientName is NULL )    
   AND (isnull(@Value,1) <> 2
        OR I.RecurringCharge = @Total
        OR @Total is NULL )    
   AND (isnull(@Value,2) <> 3
        OR I.RecurringCharge like '%'+cast(@Total as varchar(50))+'%'
        OR @Total is NULL )

Basically, your condition was

if (@Value=2)
   TEST FOR => (I.RecurringCharge=@Total  or @Total is NULL )    

flipped around,

AND (isnull(@Value,1) <> 2                -- A
        OR I.RecurringCharge = @Total    -- B
        OR @Total is NULL )              -- C

When (A) is true, i.e. @Value is not 2, [A or B or C] will become TRUE regardless of B and C results. B and C are in reality only checked when @Value = 2, which is the original intention.

The best way to calculate the height in a binary search tree? (balancing an AVL-tree)

Here's an alternate way of finding height. Add an additional attribute to your node called height:

class Node
data value; //data is a custom data type
node right;
node left;
int height;

Now, we'll do a simple breadth-first traversal of the tree, and keep updating the height value for each node:

int height (Node root)
Queue<Node> q = Queue<Node>();
Node lastnode;
//reset height
root.height = 0;

while(q.Count > 0)
   lastnode = q.Dequeue();
   if (lastnode.left != null){
      lastnode.left.height = lastnode.height + 1; 

   if (lastnode.right != null){
      lastnode.right.height = lastnode.height + 1;
return lastnode.height; //this will return a 0-based height, so just a root has a height of 0


Execute write on doc: It isn't possible to write into a document from an asynchronously-loaded external script unless it is explicitly opened.

An asynchronously loaded script is likely going to run AFTER the document has been fully parsed and closed. Thus, you can't use document.write() from such a script (well technically you can, but it won't do what you want).

You will need to replace any document.write() statements in that script with explicit DOM manipulations by creating the DOM elements and then inserting them into a particular parent with .appendChild() or .insertBefore() or setting .innerHTML or some mechanism for direct DOM manipulation like that.

For example, instead of this type of code in an inline script:

<div id="container">
document.write('<span style="color:red;">Hello</span>');

You would use this to replace the inline script above in a dynamically loaded script:

var container = document.getElementById("container");
var content = document.createElement("span"); = "red";
content.innerHTML = "Hello";

Or, if there was no other content in the container that you needed to just append to, you could simply do this:

var container = document.getElementById("container");
container.innerHTML = '<span style="color:red;">Hello</span>';

Difference between filter and filter_by in SQLAlchemy

We actually had these merged together originally, i.e. there was a "filter"-like method that accepted *args and **kwargs, where you could pass a SQL expression or keyword arguments (or both). I actually find that a lot more convenient, but people were always confused by it, since they're usually still getting over the difference between column == expression and keyword = expression. So we split them up.

Carriage return in C?

From 5.2.2/2 (character display semantics) :

\b (backspace) Moves the active position to the previous position on the current line. If the active position is at the initial position of a line, the behavior of the display device is unspecified.

\n (new line) Moves the active position to the initial position of the next line.

\r (carriage return) Moves the active position to the initial position of the current line.

Here, your code produces :

  • <new_line>ab
  • \b : back one character
  • write si : overrides the b with s (producing asi on the second line)
  • \r : back at the beginning of the current line
  • write ha : overrides the first two characters (producing hai on the second line)

In the end, the output is :


How do I set the path to a DLL file in Visual Studio?

I had the same problem and my problem had nothing to do with paths. One of my dll-s was written in c++ and it turnes out that if your visual studio doesn't know how to open a dll file it will say that it did not find it. What i did was locate which dll it did not find, than searched for that dll in my directories and opened it in a separate visual studio window. When trying to navigate through Solution explorer of that project, visual studio said that it cannot show what is inside and that i need some extra extensions, so that it can open those files. Surely enough, after installing the recomended extension (in my case something to do with c++) the

"This application has failed to start because xxx.dll was not found."

error miraculously dissapeared.

Skipping every other element after the first

def altElement(a):
    return a[::2]

Check if a variable is of function type

If you use Lodash you can do it with _.isFunction.

// => true

// => false

// => false

// => false

This method returns true if value is a function, else false.

Convert string to JSON Object

Quick answer, this eval work:

eval('var obj = {"TeamList" : [{"teamid" : "1","teamname" : "Barcelona"}]}')

How many bytes in a JavaScript string?

I'm working with an embedded version of the V8 Engine. I've tested a single string. Pushing each step 1000 characters. UTF-8.

First test with single byte (8bit, ANSI) Character "A" (hex: 41). Second test with two byte character (16bit) "O" (hex: CE A9) and the third test with three byte character (24bit) "?" (hex: E2 98 BA).

In all three cases the device prints out of memory at 888 000 characters and using ca. 26 348 kb in RAM.

Result: The characters are not dynamically stored. And not with only 16bit. - Ok, perhaps only for my case (Embedded 128 MB RAM Device, V8 Engine C++/QT) - The character encoding has nothing to do with the size in ram of the javascript engine. E.g. encodingURI, etc. is only useful for highlevel data transmission and storage.

Embedded or not, fact is that the characters are not only stored in 16bit. Unfortunally I've no 100% answer, what Javascript do at low level area. Btw. I've tested the same (first test above) with an array of character "A". Pushed 1000 items every step. (Exactly the same test. Just replaced string to array) And the system bringt out of memory (wanted) after 10 416 KB using and array length of 1 337 000. So, the javascript engine is not simple restricted. It's a kind more complex.

Initialising an array of fixed size in python

If you are working with bytes you could use the builtin bytearray. If you are working with other integral types look at the builtin array.

Specifically understand that a list is not an array.

If, for example, you are trying to create a buffer for reading file contents into you could use bytearray as follows (there are better ways to do this but the example is valid):

with open(FILENAME, 'rb') as f:
    data = bytearray(os.path.getsize(FILENAME))

In this snippet the bytearray memory is preallocated with the fixed length of FILENAMEs size in bytes. This preallocation allows the use of the buffer protocol to more efficiently read the file into a mutable buffer without an array copy. There are yet better ways to do this but I believe this provides one answer to your question.

How to store token in Local or Session Storage in Angular 2?

we can store session storage like that

store token should be like

 localStorage.setItem('user', JSON.stringify({ token: token, username: username }));

Store Session in to sessionStorage

You can store both string and array into session storage

String Ex.

    let key = 'title'; 
    let value = 'session';
    sessionStorage.setItem(key, value);

Array Ex.

    let key = 'user'; 
    let value = [{'name':'shail','email':'[email protected]'}];

    value = JSON.stringify(value);

    sessionStorage.setItem(key, value);

Get stored session from sessionStorage by key

const session = sessionStorage.getItem('key');

Delete saved session from sessionStorage by key


Delete all saved sessions from sessionStorage

  1. store Local storage should be like

Store items in to localStorage

You can store both string and array into location storage

String Ex.

 let key = 'title'; 
 let value = 'session';
 localStorage.setItem(key, value);

Array Ex.

let key = 'user'; 
let value = [{'name':'shail','email':'[email protected]'}];

value = JSON.stringify(value);

localStorage.setItem(key, value);

Get stored items from localStorage by key

const item = localStorage.getItem('key');

Delete saved session from localStorage by key


Delete all saved items from localStorage


HttpServletRequest get JSON POST data

Are you posting from a different source (so different port, or hostname)? If so, this very very recent topic I just answered might be helpful.

The problem was the XHR Cross Domain Policy, and a useful tip on how to get around it by using a technique called JSONP. The big downside is that JSONP does not support POST requests.

I know in the original post there is no mention of JavaScript, however JSON is usually used for JavaScript so that's why I jumped to that conclusion

How to use comparison and ' if not' in python?

You can do:

if not (u0 <= u <= u0+step):
    u0 = u0+ step # change the condition until it is satisfied
    do sth. # condition is satisfied

Using a loop:

while not (u0 <= u <= u0+step):
   u0 = u0+ step # change the condition until it is satisfied
do sth. # condition is satisfied

Get Request and Session Parameters and Attributes from JSF pages

You can also use a bean (request scoped is suggested) and directly access the context by way of the FacesContext.

You can get the HttpServletRequest and HttpServletResposne objects by using the following code:

HttpServletRequest req = (HttpServletRequest)FacesContext.getCurrentInstance().getExternalContext().getRequest();
HttpServletResponse res = (HttpServletResponse)FacesContext.getCurrentInstance().getExternalContext().getResponse();

After this, you can access individual parameters via getParameter(paramName) or access the full map via getParameterMap() req object

The reason I suggest a request scoped bean is that you can use these during initialization (worst case scenario being the constructor. Most frameworks give you some place to do code at bean initialization time) and they will be done as your request comes in.

It is, however, a bit of a hack. ;) You may want to look into seeing if there is a JSF Acegi module that will allow you to get access to the variables you need.

CSS flexbox vertically/horizontally center image WITHOUT explicitely defining parent height

Just add the following rules to the parent element:

display: flex;
justify-content: center; /* align horizontal */
align-items: center; /* align vertical */

Here's a sample demo (Resize window to see the image align)

Browser support for Flexbox nowadays is quite good.

For cross-browser compatibility for display: flex and align-items, you can add the older flexbox syntax as well:

display: -webkit-box;
display: -webkit-flex;
display: -moz-box;
display: -ms-flexbox;
display: flex;
-webkit-flex-align: center;
-ms-flex-align: center;
-webkit-align-items: center;
align-items: center;

Simulate user input in bash script

Here is a snippet I wrote; to ask for users' password and set it in /etc/passwd. You can manipulate it a little probably to get what you need:

echo -n " Please enter the password for the given user: "
read userPass
useradd $userAcct && echo -e "$userPass\n$userPass\n" | passwd $userAcct > /dev/null 2>&1 && echo " User account has been created." || echo " ERR -- User account creation failed!"

How can I call a function using a function pointer?

If you need help with complex definitions, like

double (*(*pf)())[3][4];

take a look at my right-left rule here.

What is difference between arm64 and armhf?

armhf stands for "arm hard float", and is the name given to a debian port for arm processors (armv7+) that have hardware floating point support.

On the beaglebone black, for example:

:~$ dpkg --print-architecture

Although other commands (such as uname -a or arch) will just show armv7l

:~$ cat /proc/cpuinfo 
processor       : 0
model name      : ARMv7 Processor rev 2 (v7l)
BogoMIPS        : 995.32
Features        : half thumb fastmult vfp edsp thumbee neon vfpv3 tls

The vfpv3 listed under Features is what refers to the floating point support.

Incidentally, armhf, if your processor supports it, basically supersedes Raspbian, which if I understand correctly was mainly a rebuild of armhf with work arounds to deal with the lack of floating point support on the original raspberry pi's. Nowdays, of course, there's a whole ecosystem build up around Raspbian, so they're probably not going to abandon it. However, this is partly why the beaglebone runs straight debian, and that's ok even if you're used to Raspbian, unless you want some of the special included non-free software such as Mathematica.

Vertical align middle with Bootstrap responsive grid

.row {
    letter-spacing: -.31em;
    word-spacing: -.43em;
.col-md-4 {
    float: none;
    display: inline-block;
    vertical-align: middle;

Note: .col-md-4 could be any grid column, its just an example here.

Using Composer's Autoload

The autoload config does start below the vendor dir. So you might want change the vendor dir, e.g.

    "config": {
        "vendor-dir": "../vendor/"
    "autoload": {
        "psr-0": {"AppName": "src/"}

Or isn't this possible in your project?

Android: Clear the back stack

Advanced, Reuseable Kotlin:

You can set the flag directly using setter method. In Kotlin or is the replacement for the Java bitwise or |.


If use this more than once, create an Intent extension function

fun Intent.clearStack() {

You can then directly call this function before starting the intent


If you need the option to add additional flags in other situations, add an optional param to the extension function.

fun Intent.clearStack(additionalFlags: Int = 0) {
    flags = additionalFlags or Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK

Passing variable from Form to Module in VBA

Don't declare the variable in the userform. Declare it as Public in the module.

Public pass As String

In the Userform

Private Sub CommandButton1_Click()
    pass = UserForm1.TextBox1
    Unload UserForm1
End Sub

In the Module

Public pass As String

Public Sub Login()
    '~~> Rest of the code
    driver.findElementByName("PASSWORD").SendKeys pass
    '~~> Rest of the code
End Sub

You might want to also add an additional check just before calling the driver.find... line?

If Len(Trim(pass)) <> 0 Then

This will ensure that a blank string is not passed.

JNI converting jstring to char *

Thanks Jason Rogers's answer first.

In Android && cpp should be this:

const char *nativeString = env->GetStringUTFChars(javaString, nullptr);

// use your string

env->ReleaseStringUTFChars(javaString, nativeString);

Can fix this errors:

1.error: base operand of '->' has non-pointer type 'JNIEnv {aka _JNIEnv}'

2.error: no matching function for call to '_JNIEnv::GetStringUTFChars(JNIEnv*&, _jstring*&, bool)'

3.error: no matching function for call to '_JNIEnv::ReleaseStringUTFChars(JNIEnv*&, _jstring*&, char const*&)'

4.add "env->DeleteLocalRef(nativeString);" at end.

Easy way to get a test file into JUnit

You can try doing:

String myResource = IOUtils.toString(this.getClass().getResourceAsStream("yourfile.xml")).replace("\n","");

Creating a new column based on if-elif-else condition

To formalize some of the approaches laid out above:

Create a function that operates on the rows of your dataframe like so:

def f(row):
    if row['A'] == row['B']:
        val = 0
    elif row['A'] > row['B']:
        val = 1
        val = -1
    return val

Then apply it to your dataframe passing in the axis=1 option:

In [1]: df['C'] = df.apply(f, axis=1)

In [2]: df
   A  B  C
a  2  2  0
b  3  1  1
c  1  3 -1

Of course, this is not vectorized so performance may not be as good when scaled to a large number of records. Still, I think it is much more readable. Especially coming from a SAS background.


Here is the vectorized version

df['C'] = np.where(
    df['A'] == df['B'], 0, np.where(
    df['A'] >  df['B'], 1, -1)) 

Android SDK installation doesn't find JDK

My problem was that i run studio.exe instead of studio64.exe. I'm running Windows 8 64bits

PHP removing a character in a string

$splitPos = strpos($url, "?/");
if ($splitPos !== false) {
    $url = substr($url, 0, $splitPos) . "?" . substr($url, $splitPos + 2);

JavaScript listener, "keypress" doesn't detect backspace?

Something I wrote up incase anyone comes across an issue with people hitting backspace while thinking they are in a form field

window.addEventListener("keydown", function(e){
     * keyCode: 8
     * keyIdentifier: "U+0008"
    if(e.keyCode === 8 && document.activeElement !== 'text') {
        alert('Prevent page from going back');

Java - How to create new Entry (key, value)

You can just implement the Map.Entry<K, V> interface yourself:

import java.util.Map;

final class MyEntry<K, V> implements Map.Entry<K, V> {
    private final K key;
    private V value;

    public MyEntry(K key, V value) {
        this.key = key;
        this.value = value;

    public K getKey() {
        return key;

    public V getValue() {
        return value;

    public V setValue(V value) {
        V old = this.value;
        this.value = value;
        return old;

And then use it:

Map.Entry<String, Object> entry = new MyEntry<String, Object>("Hello", 123);

Alter column, add default constraint

I use the stored procedure below to update the defaults on a column.

It automatically removes any prior defaults on the column, before adding the new default.

Examples of usage:

-- Update default to be a date.
exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column','getdate()';
-- Update default to be a number.
exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column,'6';
-- Update default to be a string. Note extra quotes, as this is not a function.
exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column','''MyString''';

Stored procedure:


-- Sample function calls:
--exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','ColumnName','getdate()';
--exec [dbol].[AlterDefaultForColumn] '[dbo].[TableName]','Column,'6';
--exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column','''MyString''';
create PROCEDURE [dbo].[ColumnDefaultUpdate]
        -- Table name, including schema, e.g. '[dbo].[TableName]'
        @TABLE_NAME VARCHAR(100), 
        -- Column name, e.g. 'ColumnName'.
        @COLUMN_NAME VARCHAR(100),
        -- New default, e.g. '''MyDefault''' or 'getdate()'
        -- Note that if you want to set it to a string constant, the contents
        -- must be surrounded by extra quotes, e.g. '''MyConstant''' not 'MyConstant'
    -- Trim angle brackets so things work even if they are included.

    print 'Table name: ' + @TABLE_NAME;
    print 'Column name: ' + @COLUMN_NAME;
    DECLARE @ObjectName NVARCHAR(100)
    SELECT @ObjectName = OBJECT_NAME([default_object_id]) FROM SYS.COLUMNS
    WHERE [object_id] = OBJECT_ID(@TABLE_NAME) AND [name] = @COLUMN_NAME;

    IF @ObjectName <> '' 
        print 'Removed default: ' + @ObjectName;
        --print('ALTER TABLE ' + @TABLE_NAME + ' DROP CONSTRAINT ' + @ObjectName)
        EXEC('ALTER TABLE ' + @TABLE_NAME + ' DROP CONSTRAINT ' + @ObjectName)

    print 'Added default of: ' + @NEW_DEFAULT;

Errors this stored procedure eliminates

If you attempt to add a default to a column when one already exists, you will get the following error (something you will never see if using this stored proc):

-- Using the stored procedure eliminates this error:
Msg 1781, Level 16, State 1, Line 1
Column already has a DEFAULT bound to it.
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.

Can I simultaneously declare and assign a variable in VBA?

You can sort-of do that with objects, as in the following.

Dim w As New Widget

But not with strings or variants.

Return JSON response from Flask view

If you don't want to use jsonify for some reason, you can do what it does manually. Call flask.json.dumps to create JSON data, then return a response with the application/json content type.

from flask import json

def summary():
    data = make_summary()
    response = app.response_class(
    return response

flask.json is distinct from the built-in json module. It will use the faster simplejson module if available, and enables various integrations with your Flask app.

Count the number of items in my array list

The number of itemIds in your list will be the same as the number of elements in your list:

int itemCount = list.size();

However, if you're looking to count the number of unique itemIds (per @pst) then you should use a set to keep track of them.

Set<String> itemIds = new HashSet<String>();

itemId = p.getItemId();

//... later ...
int uniqueItemIdCount = itemIds.size();

How to sort an array of integers correctly

TypeScript variant

const compareNumbers = (a: number, b: number): number => a - b


Import an Excel worksheet into Access using VBA

Pass the sheet name with the Range parameter of the DoCmd.TransferSpreadsheet Method. See the box titled "Worksheets in the Range Parameter" near the bottom of that page.

This code imports from a sheet named "temp" in a workbook named "temp.xls", and stores the data in a table named "tblFromExcel".

Dim strXls As String
strXls = CurrentProject.Path & Chr(92) & "temp.xls"
DoCmd.TransferSpreadsheet acImport, , "tblFromExcel", _
    strXls, True, "temp!"

CSS selector based on element text?

Not with CSS directly, you could set CSS properties via JavaScript based on the internal contents but in the end you would still need to be operating in the definitions of CSS.

Is it not possible to stringify an Error using JSON.stringify?

Modifying Jonathan's great answer to avoid monkey patching:

var stringifyError = function(err, filter, space) {
  var plainObject = {};
  Object.getOwnPropertyNames(err).forEach(function(key) {
    plainObject[key] = err[key];
  return JSON.stringify(plainObject, filter, space);

var error = new Error('testing');
error.detail = 'foo bar';

console.log(stringifyError(error, null, '\t'));

Laravel redirect back to original destination after login

You may use Redirect::intended function. It will redirect the user to the URL they were trying to access before being caught by the authenticaton filter. A fallback URI may be given to this method in case the intended destinaton is not available.

In post login/register:

return Redirect::intended('defaultpageafterlogin');

Concatenate chars to form String in java

Try this:

 str = String.valueOf(a)+String.valueOf(b)+String.valueOf(c);



Set session variable in laravel

For example, To store data in the session, you will typically use the putmethod or the session helper:

// Via a request instance...
$request->session()->put('key', 'value');


// Via the global helper...
session(['key' => 'value']);

for retrieving an item from the session, you can use get :

$value = $request->session()->get('key', 'default value');

or global session helper :

$value = session('key', 'default value');

To determine if an item is present in the session, you may use the has method:

if ($request->session()->has('users')) {

Difference between private, public, and protected inheritance

Protected data members can be accessed by any classes that inherit from your class. Private data members, however, cannot. Let's say we have the following:

class MyClass {
        int myPrivateMember;    // lol
        int myProtectedMember;

From within your extension to this class, referencing this.myPrivateMember won't work. However, this.myProtectedMember will. The value is still encapsulated, so if we have an instantiation of this class called myObj, then myObj.myProtectedMember won't work, so it is similar in function to a private data member.

How to remove the default link color of the html hyperlink 'a' tag?

You can use System Color (18.2) values, introduced with CSS 2.0, but deprecated in CSS 3.

a:link, a:hover, a:active { color: WindowText; }

That way your anchor links will have the same color as normal document text on this system.

Maximum size of a varchar(max) variable

As far as I can tell there is no upper limit in 2008.

In SQL Server 2005 the code in your question fails on the assignment to the @GGMMsg variable with

Attempting to grow LOB beyond maximum allowed size of 2,147,483,647 bytes.

the code below fails with

REPLICATE: The length of the result exceeds the length limit (2GB) of the target large type.

However it appears these limitations have quietly been lifted. On 2008


SET @y = REPLICATE(@y,92681);




I ran this on my 32 bit desktop machine so this 8GB string is way in excess of addressable memory


select internal_objects_alloc_page_count
from sys.dm_db_task_space_usage
WHERE session_id = @@spid



so I presume this all just gets stored in LOB pages in tempdb with no validation on length. The page count growth was all associated with the SET @y = REPLICATE(@y,92681); statement. The initial variable assignment to @y and the LEN calculation did not increase this.

The reason for mentioning this is because the page count is hugely more than I was expecting. Assuming an 8KB page then this works out at 16.36 GB which is obviously more or less double what would seem to be necessary. I speculate that this is likely due to the inefficiency of the string concatenation operation needing to copy the entire huge string and append a chunk on to the end rather than being able to add to the end of the existing string. Unfortunately at the moment the .WRITE method isn't supported for varchar(max) variables.


I've also tested the behaviour with concatenating nvarchar(max) + nvarchar(max) and nvarchar(max) + varchar(max). Both of these allow the 2GB limit to be exceeded. Trying to then store the results of this in a table then fails however with the error message Attempting to grow LOB beyond maximum allowed size of 2147483647 bytes. again. The script for that is below (may take a long time to run).

SET @y1 = @y1 + @y1;
SELECT LEN(@y1), DATALENGTH(@y1)  /*4294967294, 4294967292*/

SET @y2 = @y2 + @y2;
SELECT LEN(@y2), DATALENGTH(@y2)  /*2147483646, 4294967292*/

DECLARE @y3 NVARCHAR(MAX) = @y2 + @y1
SELECT LEN(@y3), DATALENGTH(@y3)   /*6442450940, 12884901880*/

/*This attempt fails*/
SELECT @y1 y1, @y2 y2, @y3 y3

How to delete all data from solr and hbase

To delete all documents of a Solr collection, you can use this request:

curl -X POST -H 'Content-Type: application/json' --data-binary '{"delete":{"query":"*:*" }}' http://localhost:8983/solr/my_collection/update

It uses JSON body.

Stop executing further code in Java

return to come out of the method execution, break to come out of a loop execution and continue to skip the rest of the current loop. In your case, just return, but if you are in a for loop, for example, do break to stop the loop or continue to skip to next step in the loop

Color theme for VS Code integrated terminal

Simply. You can go to 'File -> Preferences -> Color Theme' option in visual studio and change the color of you choice.

View contents of database file in Android Studio

I had to pull the database from phone to PC. Now I use this very well made and free app which has a lot of features. It works on API 4.1+with a Rooted device.
Let me know if you find how to make it work without root.

Screenshot SqlitePrime

Add and remove attribute with jquery

If you want to do this, you need to save it in a variable first. So you don't need to use id to query this element every time.

var el = $("#page_navigation1");



File content into unix variable with newlines

The envdir utility provides an easy way to do this. envdir uses files to represent environment variables, with file names mapping to env var names, and file contents mapping to env var values. If the file contents contain newlines, so will the env var.


Android: disabling highlight on listView click

Add this to your xml:


And for the problem this may work (I'm not sure and I don't know if there are better solutions):

You could apply a ColorStateList to your TextView.

Java: Calling a super method which calls an overridden method

"this" keyword refers to current class reference. That means, when it is used inside the method, the 'current' class is still SubClass and so, the answer is explained.

How do I restrict a float value to only two places after the decimal point in C?

this function takes the number and precision and returns the rounded off number

float roundoff(float num,int precision)
      int temp=(int )(num*pow(10,precision));
      int num1=num*pow(10,precision+1);
      return num;

it converts the floating point number into int by left shifting the point and checking for the greater than five condition.

Remove all newlines from inside a string

strip() returns the string with leading and trailing whitespaces(by default) removed.

So it would turn " Hello World " to "Hello World", but it won't remove the \n character as it is present in between the string.

Try replace().

str = "Hello \n World"
str2 = str.replace('\n', '')
print str2

How to connect to a MySQL Data Source in Visual Studio

unfortunately this is not supported in the builtin tools in visual studio. however, you can create your own data provider using mysql connector but still have to integrate it from code

Upload Image using POST form data in Python-requests

For Rest API to upload images from host to host:

import urllib2
import requests

api_host = ''
headers = {'Content-Type' : 'image/jpeg'}
image_url = ''

img_file = urllib2.urlopen(image_url)

response =,, headers=headers, verify=False)

You can use option verify set to False to omit SSL verification for HTTPS requests.

How to resolve symbolic links in a shell script

Is your path a directory, or might it be a file? If it's a directory, it's simple:

(cd "$DIR"; pwd -P)

However, if it might be a file, then this won't work:

DIR=$(cd $(dirname "$FILE"); pwd -P); echo "${DIR}/$(readlink "$FILE")"

because the symlink might resolve into a relative or full path.

On scripts I need to find the real path, so that I might reference configuration or other scripts installed together with it, I use this:

while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink
  DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
  SOURCE="$(readlink "$SOURCE")"
  [[ $SOURCE != /* ]] && SOURCE="$DIR/$SOURCE" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located

You could set SOURCE to any file path. Basically, for as long as the path is a symlink, it resolves that symlink. The trick is in the last line of the loop. If the resolved symlink is absolute, it will use that as SOURCE. However, if it is relative, it will prepend the DIR for it, which was resolved into a real location by the simple trick I first described.

starting file download with JavaScript

We do it that way: First add this script.

<script type="text/javascript">
function populateIframe(id,path) 
    var ifrm = document.getElementById(id);
    ifrm.src = "download.php?path="+path;

Place this where you want the download button(here we use just a link):

<iframe id="frame1" style="display:none"></iframe>
<a href="javascript:populateIframe('frame1','<?php echo $path; ?>')">download</a>

The file 'download.php' (needs to be put on your server) simply contains:

   header("Content-Type: application/octet-stream");
   header("Content-Disposition: attachment; filename=".$_GET['path']);

So when you click the link, the hidden iframe then gets/opens the sourcefile 'download.php'. With the path as get parameter. We think this is the best solution!

It should be noted that the PHP part of this solution is a simple demonstration and potentially very, very insecure. It allows the user to download any file, not just a pre-defined set. That means they could download parts of the source code of the site itself, possibly containing API credentials etc.

How to force garbage collection in Java?

.gc is a candidate for elimination in future releases - a Sun Engineer once commented that maybe fewer than twenty people in the world actually know how to use .gc() - I did some work last night for a few hours on a central / critical data-structure using SecureRandom generated data, at somewhere just past 40,000 objects the vm would slow down as though it had run out of pointers. Clearly it was choking down on 16-bit pointer tables and exhibited classic "failing machinery" behavior.

I tried -Xms and so on, kept bit twiddling until it would run to about 57,xxx something. Then it would run gc going from say 57,127 to 57,128 after a gc() - at about the pace of code-bloat at camp Easy Money.

Your design needs fundamental re-work, probably a sliding window approach.

List All Google Map Marker Images

var pinIcon = new google.maps.MarkerImage(
    null, /* size is determined at runtime */
    null, /* origin is 0,0 */
    null, /* anchor is bottom center of the scaled image */
    new google.maps.Size(12, 18)

sed: print only matching group

And for yet another option, I'd go with awk!

echo "foo bar <foo> bla 1 2 3.4" | awk '{ print $(NF-1), $NF; }'

This will split the input (I'm using STDIN here, but your input could easily be a file) on spaces, and then print out the last-but-one field, and then the last field. The $NF variables hold the number of fields found after exploding on spaces.

The benefit of this is that it doesn't matter if what precedes the last two fields changes, as long as you only ever want the last two it'll continue to work.

Force the origin to start at 0

xlim and ylim don't cut it here. You need to use expand_limits, scale_x_continuous, and scale_y_continuous. Try:

df <- data.frame(x = 1:5, y = 1:5)
p <- ggplot(df, aes(x, y)) + geom_point()
p <- p + expand_limits(x = 0, y = 0)
p # not what you are looking for

enter image description here

p + scale_x_continuous(expand = c(0, 0)) + scale_y_continuous(expand = c(0, 0))

enter image description here

You may need to adjust things a little to make sure points are not getting cut off (see, for example, the point at x = 5 and y = 5.

Use Mockito to mock some methods but not others

Partial mocking using Mockito's spy method could be the solution to your problem, as already stated in the answers above. To some degree I agree that, for your concrete use case, it may be more appropriate to mock the DB lookup. From my experience this is not always possible - at least not without other workarounds - that I would consider as being very cumbersome or at least fragile. Note, that partial mocking does not work with ally versions of Mockito. You have use at least 1.8.0.

I would have just written a simple comment for the original question instead of posting this answer, but StackOverflow does not allow this.

Just one more thing: I really cannot understand that many times a question is being asked here gets comment with "Why you want to do this" without at least trying to understand the problem. Escpecially when it comes to then need for partial mocking there are really a lot of use cases that I could imagine where it would be useful. That's why the guys from Mockito provided that functionality. This feature should of course not be overused. But when we talk about test case setups that otherwise could not be established in a very complicated way, spying should be used.

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It is also beneficial to store data into sessionStorage

// Save data to sessionStorage
sessionStorage.setItem('key', 'value');

// Get saved data from sessionStorage
var data = sessionStorage.getItem('key');

// Remove saved data from sessionStorage

// Remove all saved data from sessionStorage

for details

UTC Date/Time String to Timezone

How about:

$timezone = new DateTimeZone('UTC');
$date = new DateTime('2011-04-21 13:14', $timezone);
echo $date->format;