Programs & Examples On #Dirent.h

header file for POSIX C containing directory-related functions and types.

How to resolve the "EVP_DecryptFInal_ex: bad decrypt" during file decryption

Errors: "Bad encrypt / decrypt" "gitencrypt_smudge: FAILURE: openssl error decrypting file"

There are various error strings that are thrown from openssl, depending on respective versions, and scenarios. Below is the checklist I use in case of openssl related issues:

  1. Ideally, openssl is able to encrypt/decrypt using same key (+ salt) & enc algo only.
  2. Ensure that openssl versions (used to encrypt/decrypt), are compatible. For eg. the hash used in openssl changed at version 1.1.0 from MD5 to SHA256. This produces a different key from the same password. Fix: add "-md md5" in 1.1.0 to decrypt data from lower versions, and add "-md sha256 in lower versions to decrypt data from 1.1.0

  3. Ensure that there is a single openssl version installed in your machine. In case there are multiple versions installed simultaneously (in my machine, these were installed :- 'LibreSSL 2.6.5' and 'openssl 1.1.1d'), make the sure that only the desired one appears in your PATH variable.

How to use S_ISREG() and S_ISDIR() POSIX Macros?

You're using S_ISREG() and S_ISDIR() correctly, you're just using them on the wrong thing.

In your while((dit = readdir(dip)) != NULL) loop in main, you're calling stat on currentPath over and over again without changing currentPath:

if(stat(currentPath, &statbuf) == -1) {
    return errno;

Shouldn't you be appending a slash and dit->d_name to currentPath to get the full path to the file that you want to stat? Methinks that similar changes to your other stat calls are also needed.

Checking if a file is a directory or just a file

Yes, there is better. Check the stat or the fstat function

Python BeautifulSoup extract text between element

soup = BeautifulSoup(html)
for hit in soup.findAll(attrs={'class' : 'MYCLASS'}):
  hit = hit.text.strip()
  print hit

This will print: THIS IS MY TEXT Try this..

How to specify jackson to only use fields - preferably globally

for jackson 1.9.10 I use

ObjectMapper mapper = new ObjectMapper();

mapper.setVisibility(JsonMethod.ALL, Visibility.NONE);
mapper.setVisibility(JsonMethod.FIELD, Visibility.ANY);

to turn of auto dedection.

Convert byte to string in Java

System.out.println(new String(new byte[]{ (byte)0x63 }, "US-ASCII"));

Note especially that converting bytes to Strings always involves an encoding. If you do not specify it, you'll be using the platform default encoding, which means the code can break when running in different environments.

What causes and what are the differences between NoClassDefFoundError and ClassNotFoundException?

I remind myself the following again and again when I need to refresh


Class Hierarchy

ClassNotFoundException extends ReflectiveOperationException extends Exception extends Throwable

While debugging

  1. Required jar, class is missing from the classpath.
  2. Verify all the required jars are in classpath of jvm.


Class Hierarchy

NoClassDefFoundError extends LinkageError  extends Error extends Throwable

While debugging

  1. Problem with loading a class dynamically, which was compiled properly
  2. Problem with static blocks, constructors, init() methods of dependent class and the actual error is wrapped by multiple layers [especially when you use spring, hibernate the actual exception is wrapped and you will get NoClassDefError]
  3. When you face "ClassNotFoundException" under a static block of dependent class
  4. Problem with versions of class. This happens when you have two versions v1, v2 of same class under different jar/packages, which was compiled successfully using v1 and v2 is loaded at the runtime which doesn't has the relevant methods/vars& you will see this exception. [I once resolved this issue by removing the duplicate of log4j related class under multiple jars that appeared in the classpath]

JavaScript Array to Set

If you start out with:

let array = [
    {name: "malcom", dogType: "four-legged"},
    {name: "peabody", dogType: "three-legged"},
    {name: "pablo", dogType: "two-legged"}

And you want a set of, say, names, you would do:

let namesSet = new Set( =>;

What is sharding and why is it important?

Is sharding mostly important in very large scale applications or does it apply to smaller scale ones?

Sharding is a concern if and only if your needs scale past what can be served by a single database server. It's a swell tool if you have shardable data and you have incredibly high scalability and performance requirements. I would guess that in my entire 12 years I've been a software professional, I've encountered one situation that could have benefited from sharding. It's an advanced technique with very limited applicability.

Besides, the future is probably going to be something fun and exciting like a massive object "cloud" that erases all potential performance limitations, right? :)

Pretty-print an entire Pandas Series / DataFrame


Nobody has proposed this simple plain-text solution:

from pprint import pprint


which produces results like the following:

{'% Diabetes': 0.06365372374283895,
 '% Obesity': 0.06365372374283895,
 '% Bachelors': 0.0,
 '% Poverty': 0.09548058561425843,
 '% Driving Deaths': 1.1775938892425206,
 '% Excessive Drinking': 0.06365372374283895}

Jupyter Notebooks

Additionally, when using Jupyter notebooks, this is a great solution.

Note: pd.Series() has no .to_html() so it must be converted to pd.DataFrame()

from IPython.display import display, HTML


which produces results like the following:

Display pd.Series as table in Jupyter notebooks

ValueError: all the input arrays must have same number of dimensions

(n,) and (n,1) are not the same shape. Try casting the vector to an array by using the [:, None] notation:

n_lists = np.append(n_list_converted, n_last[:, None], axis=1)

Alternatively, when extracting n_last you can use

n_last = n_list_converted[:, -1:]

to get a (20, 1) array.

How to call a stored procedure (with parameters) from another stored procedure without temp table

You can just call the Execute command.

EXEC spDoSomthing @myDate


Since you want to return data..that's a little harder. You can use user defined functions instead that return data.

How to make div fixed after you scroll to that div?

Adding on to @Alexandre Aimbiré's answer - sometimes you may need to specify z-index:1 to have the element always on top while scrolling. Like this:

position: -webkit-sticky; /* Safari & IE */
position: sticky;
top: 0;
z-index: 1;

How to remove all callbacks from a Handler?

Define a new handler and runnable:

private Handler handler = new Handler(Looper.getMainLooper());
private Runnable runnable = new Runnable() {
        public void run() {
            // Do what ever you want

Call post delayed:

handler.postDelayed(runnable, sleep_time);

Remove your callback from your handler:


Tree implementation in Java (root, parents and children)

The process of assembling tree nodes is similar to the process of assembling lists. We have a constructor for tree nodes that initializes the instance variables.

public Tree (Object cargo, Tree left, Tree right) { 
    this.cargo = cargo; 
    this.left = left; 
    this.right = right; 

We allocate the child nodes first:

Tree left = new Tree (new Integer(2), null, null); 
Tree right = new Tree (new Integer(3), null, null); 

We can create the parent node and link it to the children at the same time:

Tree tree = new Tree (new Integer(1), left, right); 

Android Webview - Webpage should fit the device screen

These settings worked for me:


setInitialScale(1) was missing in my attempts.

Although documentation says that 0 will zoom all the way out if setUseWideViewPort is set to true but 0 did not work for me and I had to set 1.

A Parser-blocking, cross-origin script is invoked via document.write - how to circumvent it?

According to Google Developers article, you can:

Unable to import a module that is definitely installed

I had this problem with 2.7 and 3.5 installed on my system trying to test a telegram bot with Python-Telegram-Bot.

I couldn't get it to work after installing with pip and pip3, with sudo or without. I always got:

Traceback (most recent call last):
  File "", line 2, in <module>
    from telegram.ext import Updater
  File "$USER/", line 2, in <module>
    from telegram.ext import Updater
ImportError: No module named 'telegram.ext'; 'telegram' is not a package

Reading the error message correctly tells me that python is looking in the current directory for a And right, I had a script lying there called and this was loaded by python when I called import.

Conclusion, make sure you don't have any in your current working dir when trying to import. (And read error message thoroughly).

How can I show an element that has display: none in a CSS rule?

document.getElementById('mybox').style.display = "block";

How to Identify port number of SQL server

  1. Open SQL Server Management Studio
  2. Connect to the database engine for which you need the port number
  3. Run the below query against the database

    select distinct local_net_address, local_tcp_port from sys.dm_exec_connections where local_net_address is not null

The above query shows the local IP as well as the listening Port number

How do I create a URL shortener?

Implementation in Scala:

class Encoder(alphabet: String) extends (Long => String) {

  val Base = alphabet.size

  override def apply(number: Long) = {
    def encode(current: Long): List[Int] = {
      if (current == 0) Nil
      else (current % Base).toInt :: encode(current / Base)
      .map(current => alphabet.charAt(current)).mkString

class Decoder(alphabet: String) extends (String => Long) {

  val Base = alphabet.size

  override def apply(string: String) = {
    def decode(current: Long, encodedPart: String): Long = {
      if (encodedPart.size == 0) current
      else decode(current * Base + alphabet.indexOf(encodedPart.head),encodedPart.tail)

Test example with Scala test:

import org.scalatest.{FlatSpec, Matchers}

class DecoderAndEncoderTest extends FlatSpec with Matchers {

  val Alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

  "A number with base 10" should "be correctly encoded into base 62 string" in {
    val encoder = new Encoder(Alphabet)
    encoder(127) should be ("cd")
    encoder(543513414) should be ("KWGPy")

  "A base 62 string" should "be correctly decoded into a number with base 10" in {
    val decoder = new Decoder(Alphabet)
    decoder("cd") should be (127)
    decoder("KWGPy") should be (543513414)


JavaScript Editor Plugin for Eclipse

Think that JavaScriptDevelopmentTools might do it. Although, I have eclipse indigo, and I'm pretty sure it does that kind of thing automatically.

How to re-sync the Mysql DB if Master and slave have different database incase of Mysql replication?

We are using master-master replication technique of MySQL and if one MySQL server say 1 is removed from the network it reconnects itself after the connection are restored and all the records that were committed in the in the server 2 which was in the network are transferred to the server 1 which has lost the connection after restoration. Slave thread in the MySQL retries to connect to its master after every 60 sec by default. This property can be changed as MySQL ha a flag "master_connect_retry=5" where 5 is in sec. This means that we want a retry after every 5 sec.

But you need to make sure that the server which lost the connection show not make any commit in the database as you get duplicate Key error Error code: 1062

Difference between long and int data types

You're on a 32-bit machine or a 64-bit Windows machine. On my 64-bit machine (running a Unix-derivative O/S, not Windows), sizeof(int) == 4, but sizeof(long) == 8.

They're different types — sometimes the same size as each other, sometimes not.

(In the really old days, sizeof(int) == 2 and sizeof(long) == 4 — though that might have been the days before C++ existed, come to think of it. Still, technically, it is a legitimate configuration, albeit unusual outside of the embedded space, and quite possibly unusual even in the embedded space.)

100% width table overflowing div container

update your CSS to the following: this should fix

.page {
    width: 280px;
    border:solid 1px blue;
    overflow-x: auto;

KERNELBASE.dll Exception 0xe0434352 offset 0x000000000000a49d

0xe0434352 is the SEH code for a CLR exception. If you don't understand what that means, stop and read A Crash Course on the Depths of Win32™ Structured Exception Handling. So your process is not handling a CLR exception. Don't shoot the messenger, KERNELBASE.DLL is just the unfortunate victim. The perpetrator is MyApp.exe.

There should be a minidump of the crash in DrWatson folders with a full stack, it will contain everything you need to root cause the issue.

I suggest you wire up, in your myapp.exe code, AppDomain.UnhandledException and Application.ThreadException, as appropriate.

How to exit in Node.js

It depends on the reason why you're willing to exit node.js process, but in any case process.exit() is the last option to consider. A quote from documentation:

It is important to note that calling process.exit() will force the process to exit as quickly as possible even if there are still asynchronous operations pending that have not yet completed fully, including I/O operations to process.stdout and process.stderr.

In most situations, it is not actually necessary to call process.exit() explicitly. The Node.js process will exit on it's own if there is no additional work pending in the event loop. The process.exitCode property can be set to tell the process which exit code to use when the process exits gracefully.

Let’s cover possible reasons why you might be willing to exit node.js process and why you should avoid process.exit():

Case 1 - Execution complete (command line script)

If script has reached its end and node interpreter doesn't exit, it indicates that some async operations are still pending. It’s wrong to force process termination with process.exit() at this point. It’s better to try to understand what is holding your script from exiting in expected way. And when you settle this, you can use process.exitCode to return any result to calling process.

Case 2 - Termination because of external signal (SIGINT/SIGTERM/other)

For example, if you’re willing to gracefully shut down an express app. Unlike command line script, express app keeps running infinitely, waiting for new requests. process.exit() will be a bad option here because it’s going to interrupt all requests which are in pipeline. And some of them might be non-idempotent (UPDATE, DELETE). Client will never know if those requests are completed or not on server side and it might be the reason of data inconsistency between client and server. The only good solution is to tell http server to stop accepting new requests and wait for pending ones to finish with server.close():

var express = require('express');
var app = express();
var server = app.listen(80);

process.on( 'SIGTERM', function () {
   server.close(function () {
     console.log("Finished all requests");

If it still doesn't exit - see Case 1.

Case 3 - Internal error

It's always better to throw an error, you’ll get a nicely formatted stack trace and error message. Upper levels of code can always decide if they can handle error (catch) or let it crash the process. On the other side, process.exit(1) will terminate process silently and there will be no chance to recover from this. It might be the only “benefit” of process.exit(), you can be sure that process will be terminated.

How to make clang compile to llvm IR

If you have multiple files and you don't want to have to type each file, I would recommend that you follow these simple steps (I am using clang-3.8 but you can use any other version):

  1. generate all .ll files

    clang-3.8 -S -emit-llvm *.c
  2. link them into a single one

    llvm-link-3.8 -S -v -o single.ll *.ll
  3. (Optional) Optimise your code (maybe some alias analysis)

    opt-3.8 -S -O3 -aa -basicaaa -tbaa -licm single.ll -o optimised.ll
  4. Generate assembly (generates a optimised.s file)

    llc-3.8 optimised.ll
  5. Create executable (named a.out)

    clang-3.8 optimised.s

React Native add bold or italics to single words in <Text> field

You can use <Text> like a container for your other text components. This is example:

  <Text>This is a sentence</Text>
  <Text style={{fontWeight: "bold"}}> with</Text>
  <Text> one word in bold</Text>

Here is an example.

Find duplicate lines in a file and count how many time each line was duplicated?

This will print duplicate lines only, with counts:

sort FILE | uniq -cd

or, with GNU long options (on Linux):

sort FILE | uniq --count --repeated

on BSD and OSX you have to use grep to filter out unique lines:

sort FILE | uniq -c | grep -v '^ *1 '

For the given example, the result would be:

  3 123
  2 234

If you want to print counts for all lines including those that appear only once:

sort FILE | uniq -c

or, with GNU long options (on Linux):

sort FILE | uniq --count

For the given input, the output is:

  3 123
  2 234
  1 345

In order to sort the output with the most frequent lines on top, you can do the following (to get all results):

sort FILE | uniq -c | sort -nr

or, to get only duplicate lines, most frequent first:

sort FILE | uniq -cd | sort -nr

on OSX and BSD the final one becomes:

sort FILE | uniq -c | grep -v '^ *1 ' | sort -nr

Adding simple legend to plot in R

Take a look at ?legend and try this:

legend('topright', names(a)[-1] , 
   lty=1, col=c('red', 'blue', 'green',' brown'), bty='n', cex=.75)

enter image description here

Find the host name and port using PSQL commands

service postgresql status

returns: 10/main (port 5432): online

I'm running Ubuntu 18.04

How to place a div below another div?

what about changing the position: relative on your #content #text div to position: absolute

#content #text {

then you can use the css properties left and top to position within the #content div

Test whether string is a valid integer

I like the solution using the -eq test, because it's basically a one-liner.

My own solution was to use parameter expansion to throw away all the numerals and see if there was anything left. (I'm still using 3.0, haven't used [[ or expr before, but glad to meet them.)

if [ "${INPUT_STRING//[0-9]}" = "" ]; then
  # yes, natural number
  # no, has non-numeral chars

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

It depends on the likelihood of a semicolon ending up near your &, causing it to display something quite different.

For example, when dealing with input from users (say, if you include the user-provided subject of a forum post in your title tags), you never know where they might be putting random semicolons, and it might randomly display strange entities. So always escape in that situation.

For your own static html, sure, you could skip it, but it's so trivial to include proper escaping, that there's no good reason to avoid it.

how to use free cloud database with android app?

Now there are a lot of cloud providers , providing solutions like MBaaS (Mobile Backend as a Service). Some only give access to cloud database, some will do the user management for you, some let you place code around cloud database and there are facilities of access control, push notifications, analytics, integrated image and file hosting etc.

Here are some providers which have a "free-tier" (may change in future):

  1. Firebase (Google) -
  2. AWS Mobile (Amazon) -
  3. Azure Mobile (Microsoft) -
  4. MongoDB Realm (MongoDB) -
  5. Back4app (Popular) -

Open source solutions:

  1. Parse -
  2. Apache User Grid -
  3. SupaBase (under development) -

MD5 hashing in Android

i have used below method to give me md5 by passing string for which you want to get md5

public static String getMd5Key(String password) {

//        String password = "12131123984335";

        try {
            MessageDigest md = MessageDigest.getInstance("MD5");

            byte byteData[] = md.digest();

            //convert the byte to hex format method 1
            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < byteData.length; i++) {
                sb.append(Integer.toString((byteData[i] & 0xff) + 0x100, 16).substring(1));

            System.out.println("Digest(in hex format):: " + sb.toString());

            //convert the byte to hex format method 2
            StringBuffer hexString = new StringBuffer();
            for (int i = 0; i < byteData.length; i++) {
                String hex = Integer.toHexString(0xff & byteData[i]);
                if (hex.length() == 1) hexString.append('0');
            System.out.println("Digest(in hex format):: " + hexString.toString());

            return hexString.toString();

        } catch (Exception e) {
            // TODO: handle exception

        return "";

Wordpress plugin install: Could not create directory

For me the problem was FTP server that WP is using to upload update. It had writting disabled in configuration, so just enabling it fixed the problem.

Shame on WordPress for providing such misleading error message.

How to check Oracle database for long running queries

  from v$sql sq, v$session se
 order by sq.ELAPSED_TIME desc, sq.LAST_LOAD_TIME desc;

How to append strings using sprintf?

int length = 0;
length += sprintf(Buffer+length, "Hello World");
length += sprintf(Buffer+length, "Good Morning");
length += sprintf(Buffer+length, "Good Afternoon");

Here is a version with some resistance to errors. It is useful if you do not care when errors happen so long as you can continue along your merry way when they do.

int bytes_added( int result_of_sprintf )
    return (result_of_sprintf > 0) ? result_of_sprintf : 0;

int length = 0;
length += bytes_added(sprintf(Buffer+length, "Hello World"));
length += bytes_added(sprintf(Buffer+length, "Good Morning"));
length += bytes_added(sprintf(Buffer+length, "Good Afternoon"));

How to test if JSON object is empty in Java

If empty array:

.size() == 0

if empty object:

.length() == 0

How can I generate an MD5 hash?

No need to make it too complicated.
DigestUtils works fine and makes you comfortable while working with md5 hashes.




Either you can use any other encryption methods such as sha or md.

Why can't non-default arguments follow default arguments?

All required parameters must be placed before any default arguments. Simply because they are mandatory, whereas default arguments are not. Syntactically, it would be impossible for the interpreter to decide which values match which arguments if mixed modes were allowed. A SyntaxError is raised if the arguments are not given in the correct order:

Let us take a look at keyword arguments, using your function.

def fun1(a="who is you", b="True", x, y):
...     print a,b,x,y

Suppose its allowed to declare function as above, Then with the above declarations, we can make the following (regular) positional or keyword argument calls:

func1("ok a", "ok b", 1)  # Is 1 assigned to x or ?
func1(1)                  # Is 1 assigned to a or ?
func1(1, 2)               # ?

How you will suggest the assignment of variables in the function call, how default arguments are going to be used along with keyword arguments.

>>> def fun1(x, y, a="who is you", b="True"):
...     print a,b,x,y

Reference O'Reilly - Core-Python
Where as this function make use of the default arguments syntactically correct for above function calls. Keyword arguments calling prove useful for being able to provide for out-of-order positional arguments, but, coupled with default arguments, they can also be used to "skip over" missing arguments as well.

How to Correctly Use Lists in R?

Just to address the last part of your question, since that really points out the difference between a list and vector in R:

Why do these two expressions not return the same result?

x = list(1, 2, 3, 4); x2 = list(1:4)

A list can contain any other class as each element. So you can have a list where the first element is a character vector, the second is a data frame, etc. In this case, you have created two different lists. x has four vectors, each of length 1. x2 has 1 vector of length 4:

> length(x[[1]])
[1] 1
> length(x2[[1]])
[1] 4

So these are completely different lists.

R lists are very much like a hash map data structure in that each index value can be associated with any object. Here's a simple example of a list that contains 3 different classes (including a function):

> complicated.list <- list("a"=1:4, "b"=1:3, "c"=matrix(1:4, nrow=2), "d"=search)
> lapply(complicated.list, class)
[1] "integer"
[1] "integer"
[1] "matrix"
[1] "function"

Given that the last element is the search function, I can call it like so:

> complicated.list[["d"]]()
[1] ".GlobalEnv" ...

As a final comment on this: it should be noted that a data.frame is really a list (from the data.frame documentation):

A data frame is a list of variables of the same number of rows with unique row names, given class ‘"data.frame"’

That's why columns in a data.frame can have different data types, while columns in a matrix cannot. As an example, here I try to create a matrix with numbers and characters:

> a <- 1:4
> class(a)
[1] "integer"
> b <- c("a","b","c","d")
> d <- cbind(a, b)
> d
 a   b  
[1,] "1" "a"
[2,] "2" "b"
[3,] "3" "c"
[4,] "4" "d"
> class(d[,1])
[1] "character"

Note how I cannot change the data type in the first column to numeric because the second column has characters:

> d[,1] <- as.numeric(d[,1])
> class(d[,1])
[1] "character"

What does -Xmn jvm option stands for

From GC Performance Tuning training documents of Oracle:

-Xmn[size]: Size of young generation heap space.

Applications with emphasis on performance tend to use -Xmn to size the young generation, because it combines the use of -XX:MaxNewSize and -XX:NewSize and almost always explicitly sets -XX:PermSize and -XX:MaxPermSize to the same value.

In short, it sets the NewSize and MaxNewSize values of New generation to the same value.

How to order citations by appearance using BibTeX?

Just a brief note - I'm using a modified version of plain.bst sitting in the directory with my Latex files; it turns out having sorting by order of appearance is a relatively easy change; just find the piece of code:

ITERATE {presort}


... and comment it - I turned it to:

%% % avoid sort:
%% ITERATE {presort}

... and then, after running bibtex, pdflatex, pdflatex - the citations will be sorted by order of appearance (that is, they will be unsorted :) ).


EDIT: just realized that what I wrote is actually in the comment by @ChrisN: "can you edit it to remove the SORT command" ;)

How to abort makefile if variable not set?

TL;DR: Use the error function:

ifndef MY_FLAG
$(error MY_FLAG is not set)

Note that the lines must not be indented. More precisely, no tabs must precede these lines.

Generic solution

In case you're going to test many variables, it's worth defining an auxiliary function for that:

# Check that given variables are set and all have non-empty values,
# die with an error otherwise.
# Params:
#   1. Variable name(s) to test.
#   2. (optional) Error message to print.
check_defined = \
    $(strip $(foreach 1,$1, \
        $(call __check_defined,$1,$(strip $(value 2)))))
__check_defined = \
    $(if $(value $1),, \
      $(error Undefined $1$(if $2, ($2))))

And here is how to use it:

$(call check_defined, MY_FLAG)

$(call check_defined, OUT_DIR, build directory)
$(call check_defined, BIN_DIR, where to put binary artifacts)
$(call check_defined, \
            LIB_INCLUDE_DIR \
            LIB_SOURCE_DIR, \
        library path)

This would output an error like this:

Makefile:17: *** Undefined OUT_DIR (build directory).  Stop.


The real check is done here:

$(if $(value $1),,$(error ...))

This reflects the behavior of the ifndef conditional, so that a variable defined to an empty value is also considered "undefined". But this is only true for simple variables and explicitly empty recursive variables:

# ifndef and check_defined consider these UNDEFINED:
explicitly_empty =
simple_empty := $(explicitly_empty)

# ifndef and check_defined consider it OK (defined):
recursive_empty = $(explicitly_empty)

As suggested by @VictorSergienko in the comments, a slightly different behavior may be desired:

$(if $(value $1) tests if the value is non-empty. It's sometimes OK if the variable is defined with an empty value. I'd use $(if $(filter undefined,$(origin $1)) ...


Moreover, if it's a directory and it must exist when the check is run, I'd use $(if $(wildcard $1)). But would be another function.

Target-specific check

It is also possible to extend the solution so that one can require a variable only if a certain target is invoked.

$(call check_defined, ...) from inside the recipe

Just move the check into the recipe:

foo :
    @:$(call check_defined, BAR, baz value)

The leading @ sign turns off command echoing and : is the actual command, a shell no-op stub.

Showing target name

The check_defined function can be improved to also output the target name (provided through the $@ variable):

check_defined = \
    $(strip $(foreach 1,$1, \
        $(call __check_defined,$1,$(strip $(value 2)))))
__check_defined = \
    $(if $(value $1),, \
        $(error Undefined $1$(if $2, ($2))$(if $(value @), \
                required by target `$@')))

So that, now a failed check produces a nicely formatted output:

Makefile:7: *** Undefined BAR (baz value) required by target `foo'.  Stop.

check-defined-MY_FLAG special target

Personally I would use the simple and straightforward solution above. However, for example, this answer suggests using a special target to perform the actual check. One could try to generalize that and define the target as an implicit pattern rule:

# Check that a variable specified through the stem is defined and has
# a non-empty value, die with an error otherwise.
#   %: The name of the variable to test.
check-defined-% : __check_defined_FORCE
    @:$(call check_defined, $*, target-specific)

# Since pattern rules can't be listed as prerequisites of .PHONY,
# we use the old-school and hackish FORCE workaround.
# You could go without this, but otherwise a check can be missed
# in case a file named like `check-defined-...` exists in the root 
# directory, e.g. left by an accidental `make -t` invocation.
.PHONY : __check_defined_FORCE
__check_defined_FORCE :


foo :|check-defined-BAR

Notice that the check-defined-BAR is listed as the order-only (|...) prerequisite.


  • (arguably) a more clean syntax


I believe, these limitations can be overcome using some eval magic and secondary expansion hacks, although I'm not sure it's worth it.

Best way to detect Mac OS X or Windows computers with JavaScript or jQuery

It's as simple as that:

function isMacintosh() {
  return navigator.platform.indexOf('Mac') > -1

function isWindows() {
  return navigator.platform.indexOf('Win') > -1

You can do funny things then like:

var isMac = isMacintosh();
var isPC = !isMacintosh();

How to remove last n characters from every element in the R vector

Similar to @Matthew_Plourde using gsub

However, using a pattern that will trim to zero characters i.e. return "" if the original string is shorter than the number of characters to cut:

cs <- c("foo_bar","bar_foo","apple","beer","so","a")
gsub('.{0,3}$', '', cs)
# [1] "foo_" "bar_" "ap"   "b"    ""    ""

Difference is, {0,3} quantifier indicates 0 to 3 matches, whereas {3} requires exactly 3 matches otherwise no match is found in which case gsub returns the original, unmodified string.

N.B. using {,3} would be equivalent to {0,3}, I simply prefer the latter notation.

See here for more information on regex quantifiers:

Dark color scheme for Eclipse

I played with customizing the colors. I went with the yellow text/blue background I've liked from Turbo Pascal. The problem I ran into was it let you set the colors of the editors but then the other views like Package Explorer or Navigator stayed with the default black-on-white colors. I'm sure you could do it programatically but there are waaaay to many settings for my patience.

Are these methods thread safe?

It follows the convention that static methods should be thread-safe, but actually in v2 that static api is a proxy to an instance method on a default instance: in the case protobuf-net, it internally minimises contention points, and synchronises the internal state when necessary. Basically the library goes out of its way to do things right so that you can have simple code.

Best way to simulate "group by" from bash?

It seems that you have to either use a big amount of code to simulate hashes in bash to get linear behavior or stick to the quadratic superlinear versions.

Among those versions, saua's solution is the best (and simplest):

sort -n ip_addresses.txt | uniq -c

I found But it's ugly as hell...

Android: I lost my android key store, what should I do?

I want to refine this a little bit because down-votes indicate to me that people don't understand that these suggestions are like "last hope" approach for someone who got into the state described in the question.

Check your console input history and/or ant scripts you have been using if you have them. Keep in mind that the console history will not be saved if you were promoted for password but if you entered it within for example signing command you can find it.

You mentioned you have a zip with a password in which your certificate file is stored, you could try just brute force opening that with many tools available. People will say "Yea but what if you used strong password, you should bla,bla,bla..." Unfortunately in that case tough-luck. But people are people and they sometimes use simple passwords. For you any tool that can provide dictionary attacks in which you can enter your own words and set them to some passwords you suspect might help you. Also if password is short enough with today CPUs even regular brute force guessing might work since your zip file does not have any limitation on number of guesses so you will not get blocked as if you tried to brute force some account on a website.

How to scroll to the bottom of a UITableView on the iPhone before the view appears

[self.tableViewInfo scrollRectToVisible:CGRectMake(0, self.tableViewInfo.contentSize.height-self.tableViewInfo.height, self.tableViewInfo.width, self.tableViewInfo.height) animated:YES];

How to find all positions of the maximum value in a list?

You can do it in various ways.

The old conventional way is,

maxIndexList = list() #this list will store indices of maximum values
maximumValue = max(a) #get maximum value of the list
length = len(a)       #calculate length of the array

for i in range(length): #loop through 0 to length-1 (because, 0 based indexing)
    if a[i]==maximumValue: #if any value of list a is equal to maximum value then store its index to maxIndexList

print(maxIndexList) #finally print the list

Another way without calculating the length of the list and storing maximum value to any variable,

maxIndexList = list()
index = 0 #variable to store index
for i in a: #iterate through the list (actually iterating through the value of list, not index )
    if i==max(a): #max(a) returns a maximum value of list.
        maxIndexList.append(index) #store the index of maximum value
index = index+1 #increment the index


We can do it in Pythonic and smart way! Using list comprehension just in one line,

maxIndexList = [i for i,j in enumerate(a) if j==max(a)] #here,i=index and j = value of that index

All my codes are in Python 3.

How can I include all JavaScript files in a directory via JavaScript file?

It can be done fully client side, but all javascript file names must be specified. For example, as array items:

function loadScripts(){
   var directory = 'script/';
   var extension = '.js';
   var files = ['model', 'view', 'controller'];  
   for (var file of files){ 
       var path = directory + file + extension; 
       var script = document.createElement("script");
       script.src = path;

Manually install Gradle and use it in Android Studio

If you are on LINUX follow the steps below:

  • Go to the download and download the latest zip file (currently 3.1 is the latest version)

  • Extract the downloaded zip file into /opt/android-studio/gradle/.

  • Open your project in Android Studio and hit Ctrl + Alt + S

  • Search for Gradle in the Search bar of the setting window

  • Select: (X) Use local gradle distribution and set Gradle home to /opt/andriod-studio/gradle/gradle.x.x (where x.x is the vesrion of the gradle zip file you just downloaded.). Then click on apply.

  • Try to sync Gradle again if the sync has already failed.If not close your project and reopen your project.

    Hope this solves your problem.

how to pass value from one php page to another using session

Use something like this:


$_SESSION['myValue']=3; // You can set the value however you like.

Any other PHP page:

echo $_SESSION['myValue'];

A few notes to keep in mind though: You need to call session_start() BEFORE any output, HTML, echos - even whitespace.

You can keep changing the value in the session - but it will only be able to be used after the first page - meaning if you set it in page 1, you will not be able to use it until you get to another page or refresh the page.

The setting of the variable itself can be done in one of a number of ways:


And if you want to check if the variable is set before getting a potential error, use something like this:

    echo $_SESSION['myValue'];
    echo "Session not set yet.";

How to convert integer into date object python?

This question is already answered, but for the benefit of others looking at this question I'd like to add the following suggestion: Instead of doing the slicing yourself as suggested above you might also use strptime() which is (IMHO) easier to read and perhaps the preferred way to do this conversion.

import datetime
s = "20120213"
s_datetime = datetime.datetime.strptime(s, '%Y%m%d')

Apache default VirtualHost

I will say what worked for me, the others answers above didn't help to my case at all. I hope it can help someone.

Actually, I'm using Virtual host configuration (sites-available / sites-enabled) on EC2 Linux AMI with Apache/2.4.39 (Amazon). So, I have 1 ec2 instance to serve many sites (domains).

Considering that you already have Virtual Host installed and working. In my folder /etc/httpd/sites-available, I have some files with domain names (suffix .conf), for example: Create a new file like that.

sudo nano /etc/httpd/sites-available/

<VirtualHost *:80>
    DocumentRoot /var/www/html/domain

For each file.conf in sites-available, I create a symbolic link:

sudo ln -s /etc/httpd/sites-available/ /etc/httpd/sites-enabled/

This is the default configuration, so, if access directly by IP of Server, you will be redirect to DocumentRoot of the first file (.conf) in sites-available folder, sorted by filename.

To have a default DocumentRoot folder when access by IP, you have to create a file named 0a.conf, then apache will serve this site because this new file will be the first in sites-available folder.

You must create a symbolic link:

sudo ln -s /etc/httpd/sites-available/0a.conf /etc/httpd/sites-enabled/0a.conf

To check serving order, use it:

sudo apachectl -S

Now, restart apache, and check out it.

Be happy =)

Determine installed PowerShell version

I found the easiest way to check if installed was to:

  • run a command prompt (Start, Run, cmd, then OK)
  • type powershell then hit return. You should then get the PowerShell PS prompt:


Windows PowerShell
Copyright (C) 2009 Microsoft Corporation. All rights reserved.

PS C:\Users\MyUser>

You can then check the version from the PowerShell prompt by typing $PSVersionTable.PSVersion:

PS C:\Users\MyUser> $PSVersionTable.PSVersion

Major  Minor  Build  Revision
-----  -----  -----  --------
2      0      -1     -1

PS C:\Users\MyUser>

Type exit if you want to go back to the command prompt (exit again if you want to also close the command prompt).

To run scripts, see

How to prevent a browser from storing passwords

You should be able to make a fake hidden password box to prevent it.

  <div style="display:none">_x000D_
    <input type="password" tabindex="-1"/>_x000D_
  <input type="text" name="username" placeholder="username"/>_x000D_
  <input type="password" name="password" placeholder="password"/>_x000D_

What is correct content-type for excel files?

Do keep in mind that the file.getContentType could also output application/octet-stream instead of the required application/vnd.openxmlformats-officedocument.spreadsheetml.sheet when you try to upload the file that is already open.

.crx file install in chrome

Update: appears to have stopped working since Chrome 80

Drag & Drop the '.crx' file on to the 'Extensions' page

  1. Settings - icon > Tools > Extensions
    ( the 'hamburger' icon in the top-right corner )

  2. Enable Developer Mode ( toggle button in top-right corner )

  3. Drag and drop the '.crx' extension file onto the Extensions page from step 1
    ( crx file should likely be in your Downloads directory )

  4. Install

Source: Chrome YouTube Downloader - install instructions

How to remove first 10 characters from a string?

str = "hello world!";
str.Substring(10, str.Length-10)

you will need to perform the length checks else this would throw an error

Export to CSV using jQuery and html

What if you have your data in CSV format and convert it to HTML for display on the web page? You may use the plugin. Check this example As you are already using jQuery library I have assumed you are able to add other javascript toolkit libraries.

If the data is in CSV format, you should be able to use the generic 'application/octetstream' mime type. All the 3 mime types you have tried are dependent on the software installed on the clients computer.

HttpContext.Current.Request.Url.Host what it returns?

The Host property will return the domain name you used when accessing the site. So, in your development environment, since you're requesting


It's returning localhost. You can break apart your URL like so:

Protocol: http
Host: localhost
Port: 950
PathAndQuery: /m/pages/SearchResults.aspx?search=knight&filter=kitchen

How to get the PYTHONPATH in shell?

Those of us using Python 3.x should do this:

python -c "import sys; print(sys.path)"

How to make an authenticated web request in Powershell?

For those that need Powershell to return additional information like the Http StatusCode, here's an example. Included are the two most likely ways to pass in credentials.

Its a slightly modified version of this SO answer:
How to obtain numeric HTTP status codes in PowerShell

$req = [system.Net.WebRequest]::Create($url)
# method 1 $req.UseDefaultCredentials = $true
# method 2 $req.Credentials = New-Object System.Net.NetworkCredential($username, $pwd, $domain); 
    $res = $req.GetResponse()
catch [System.Net.WebException]
    $res = $_.Exception.Response

$int = [int]$res.StatusCode
$status = $res.StatusCode
return "$int $status"

Parse string to date with moment.js

Maybe try the Intl polyfill for IE8 or the olyfill service ?


Get time difference between two dates in seconds

The Code

var startDate = new Date();
// Do your operations
var endDate   = new Date();
var seconds = (endDate.getTime() - startDate.getTime()) / 1000;

Or even simpler (endDate - startDate) / 1000 as pointed out in the comments unless you're using typescript.

The explanation

You need to call the getTime() method for the Date objects, and then simply subtract them and divide by 1000 (since it's originally in milliseconds). As an extra, when you're calling the getDate() method, you're in fact getting the day of the month as an integer between 1 and 31 (not zero based) as opposed to the epoch time you'd get from calling the getTime() method, representing the number of milliseconds since January 1st 1970, 00:00


Depending on what your date related operations are, you might want to invest in integrating a library such as date.js or moment.js which make things so much easier for the developer, but that's just a matter of personal preference.

For example in moment.js we would do moment1.diff(moment2, "seconds") which is beautiful.

Useful docs for this answer

Sending files using POST with HttpURLConnection

I tried the solutions above and none worked for me out of the box.

However Line 6 POST Multipart Request worked within seconds

public void whenSendMultipartRequestUsingHttpClient_thenCorrect() 
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("");

    MultipartEntityBuilder builder = MultipartEntityBuilder.create();
    builder.addTextBody("username", "John");
    builder.addTextBody("password", "pass");
    builder.addBinaryBody("file", new File("test.txt"),
      ContentType.APPLICATION_OCTET_STREAM, "file.ext");

    HttpEntity multipart =;

    CloseableHttpResponse response = client.execute(httpPost);

What's the -practical- difference between a Bare and non-Bare repository?

$ git help repository-layout

A Git repository comes in two different flavours:

  • a .git directory at the root of the working tree;
  • a .git directory that is a bare repository (i.e. without its own working tree), that is typically used for exchanging histories with others by pushing into it and fetching from it.

get one item from an array of name,value JSON

You can't do what you're asking natively with an array, but javascript objects are hashes, so you can say...

var hash = {};
hash['k1'] = 'abc';

Then you can retrieve using bracket or dot notation:

alert(hash['k1']); // alerts 'abc'
alert(hash.k1); // also alerts 'abc'

For arrays, check the underscore.js library in general and the detect method in particular. Using detect you could do something like...

_.detect(arr, function(x) { return == 'k1' });

Or more generally

MyCollection = function() {
  this.arr = [];

MyCollection.prototype.getByName = function(name) {
  return _.detect(this.arr, function(x) { return == name });

MyCollection.prototype.push = function(item) {


Spring 3 RequestMapping: Get path value

I have a similar problem and I resolved in this way:

@RequestMapping(value = "{siteCode}/**/{fileName}.{fileExtension}")
public HttpEntity<byte[]> getResource(@PathVariable String siteCode,
        @PathVariable String fileName, @PathVariable String fileExtension,
        HttpServletRequest req, HttpServletResponse response ) throws IOException {
    String fullPath = req.getPathInfo();
    // Calling http://localhost:8080/SiteXX/images/argentine/flag.jpg
    // fullPath conentent: /SiteXX/images/argentine/flag.jpg

Note that req.getPathInfo() will return the complete path (with {siteCode} and {fileName}.{fileExtension}) so you will have to process conveniently.

Export HTML page to PDF on user click using JavaScript

This is because you define your "doc" variable outside of your click event. The first time you click the button the doc variable contains a new jsPDF object. But when you click for a second time, this variable can't be used in the same way anymore. As it is already defined and used the previous time.

change it to:

$(function () {

    var specialElementHandlers = {
        '#editor': function (element,renderer) {
            return true;
 $('#cmd').click(function () {
        var doc = new jsPDF();
            $('#target').html(), 15, 15, 
            { 'width': 170, 'elementHandlers': specialElementHandlers }, 
            function(){'sample-file.pdf'); }


and it will work.

Submit two forms with one button

A form submission causes the page to navigate away to the action of the form. So, you cannot submit both forms in the traditional way. If you try to do so with JavaScript by calling form.submit() on each form in succession, each request will be aborted except for the last submission. So, you need to submit the first form asynchronously via JavaScript:

var f = document.forms.updateDB;
var postData = [];
for (var i = 0; i < f.elements.length; i++) {
    postData.push(f.elements[i].name + "=" + f.elements[i].value);
var xhr = new XMLHttpRequest();"POST", "mypage.php", true);
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");


How do I execute a string containing Python code in Python?

In the example a string is executed as code using the exec function.

import sys
import StringIO

# create file-like string to capture output
codeOut = StringIO.StringIO()
codeErr = StringIO.StringIO()

code = """
def f(x):
    x = x + 1
    return x

print 'This is my output.'

# capture output and errors
sys.stdout = codeOut
sys.stderr = codeErr

exec code

# restore stdout and stderr
sys.stdout = sys.__stdout__
sys.stderr = sys.__stderr__

print f(4)

s = codeErr.getvalue()

print "error:\n%s\n" % s

s = codeOut.getvalue()

print "output:\n%s" % s


An explicit value for the identity column in table can only be specified when a column list is used and IDENTITY_INSERT is ON SQL Server

In order to populate all of the column names into a comma-delimited list for a Select statement for the solutions mentioned for this question, I use the following options as they are a little less verbose than most responses here. Although, most responses here are still perfectly acceptable, however.


SELECT column_name + ',' 
FROM   information_schema.columns 
WHERE  table_name = 'YourTable'

2) This is probably the simplest approach to creating columns, if you have SQL Server SSMS.

1) Go to the table in Object Explorer and click on the + to the left of the table name or double-click the table name to open the sub list.

2) Drag the column subfolder over to the main query area and it will autopaste the entire column list for you.

continuing execution after an exception is thrown in java

If you throw the exception, the method execution will stop and the exception is thrown to the caller method. throw always interrupt the execution flow of the current method. a try/catch block is something you could write when you call a method that may throw an exception, but throwing an exception just means that method execution is terminated due to an abnormal condition, and the exception notifies the caller method of that condition.

Find this tutorial about exception and how they work -

Returning a boolean from a Bash function

Be careful when checking directory only with option -d !
if variable $1 is empty the check will still be successfull. To be sure, check also that the variable is not empty.

#! /bin/bash


    if [[ -d $1 ]] && [[ -n $1 ]] ; then
        return 0
        return 1


if is_directory $1 ; then
    echo "Directory exist"
    echo "Directory does not exist!" 

Checking for empty or null JToken in a JObject

There is also a type - JTokenType.Undefined.

This check must be included in @Brian Rogers answer.

token.Type == JTokenType.Undefined

makefile execute another target

If you removed the make all line from your "fresh" target:

fresh :
    rm -f *.o $(EXEC)

You could simply run the command make fresh all, which will execute as make fresh; make all.

Some might consider this as a second instance of make, but it's certainly not a sub-instance of make (a make inside of a make), which is what your attempt seemed to result in.

Check table exist or not before create it in Oracle

-- checks for table in specfic schema:

declare n number(10);

    Select count(*) into n  from SYS.All_All_Tables where owner = 'MYSCHEMA' and TABLE_NAME =  'EMPLOYEE';

   if (n = 0) then 
     execute immediate 
     'create table MYSCHEMA.EMPLOYEE ( ID NUMBER(3), NAME VARCHAR2(30) NOT NULL)';      
   end if;

How to make <input type="date"> supported on all browsers? Any alternatives?

best easy and working solution i have found is, working on following browsers

  1. Google Chrome
  2. Firefox
  3. Microsoft Edge
  4. Safari

    <!doctype html>
    <meta charset="utf-8">
    <title>Untitled Document</title>
    <h2>Poly Filler Script for Date/Time</h2>
    <form method="post" action="">
        <input type="date" />
        <input type="time" />
    <script src=""></script>
    <script src=""></script>
    <script src=""></script>
      webshims.setOptions('waitReady', false);
      webshims.setOptions('forms-ext', {type: 'date'});
      webshims.setOptions('forms-ext', {type: 'time'});
      webshims.polyfill('forms forms-ext');

Error: «Could not load type MvcApplication»

Check code behind information, provided in global.asax. They should correctly point to the class in its code behind.

sample global.asax:

<%@ Application Codebehind="Global.asax.cs" Inherits="MyApplicationNamespace.MyMvcApplication" Language="C#" %>

sample code behind:

   namespace MyApplicationNamespace
        public class MyMvcApplication : System.Web.HttpApplication
            protected void Application_Start( )
                AreaRegistration.RegisterAllAreas( );
                FilterConfig.RegisterGlobalFilters( GlobalFilters.Filters );
                RouteConfig.RegisterRoutes( RouteTable.Routes );
                BundleConfig.RegisterBundles( BundleTable.Bundles );

Android: how to convert whole ImageView to Bitmap?

It works in Kotlin after buildDrawingCache() being deprecated

 // convert imageView to bitmap
val bitmap = (imageViewId.getDrawable() as BitmapDrawable).getBitmap()

What is the difference between JOIN and JOIN FETCH when using JPA and Hibernate

If you have @oneToOne mapping set to FetchType.LAZY and you use second query (because you need Department objects to be loaded as part of Employee objects) what Hibernate will do is, it will issue queries to fetch Department objects for every individual Employee object it fetches from DB.

Later, in the code you might access Department objects via Employee to Department single-valued association and Hibernate will not issue any query to fetch Department object for the given Employee.

Remember, Hibernate still issues queries equal to the number of Employees it has fetched. Hibernate will issue same number of queries in both above queries, if you wish to access Department objects of all Employee objects

Troubleshooting misplaced .git directory (nothing to commit)

I just had this problem myself because I was in the wrong folder. I was nested 1 level in, so there were no git files to be found.

When I execute cd .. to the correct directory, I was able to commit, as expected.

Get only the Date part of DateTime in mssql

This may not be as slick as a one-liner, but I use it to perform date manipulation mainly for reports:

DECLARE @Date datetime

-- Set all time components to zero
SET @Date = DATEADD(ms, -DATEPART(ms, @Date), @Date) -- milliseconds = 0
SET @Date = DATEADD(ss, -DATEPART(ss, @Date), @Date) -- seconds = 0
SET @Date = DATEADD(mi, -DATEPART(mi, @Date), @Date) -- minutes = 0
SET @Date = DATEADD(hh, -DATEPART(hh, @Date), @Date) -- hours = 0

-- Extra manipulation for month and year
SET @Date = DATEADD(dd, -DATEPART(dd, @Date) + 1, @Date) -- day = 1
SET @Date = DATEADD(mm, -DATEPART(mm, @Date) + 1, @Date) -- month = 1

I use this to get hourly, daily, monthly, and yearly dates used for reporting and performance indicators, etc.

Insert data into a view (SQL Server)

Looks like you are running afoul of this rule for updating views from Books Online: "INSERT statements must specify values for any columns in the underlying table that do not allow null values and have no DEFAULT definitions."

Transpose a data frame

You'd better not transpose the data.frame while the name column is in it - all numeric values will then be turned into strings!

Here's a solution that keeps numbers as numbers:

# first remember the names
n <- df.aree$name

# transpose all but the first column (name)
df.aree <-[,-1]))
colnames(df.aree) <- n
df.aree$myfactor <- factor(row.names(df.aree))

str(df.aree) # Check the column types

Declaring abstract method in TypeScript

If you take Erics answer a little further you can actually create a pretty decent implementation of abstract classes, with full support for polymorphism and the ability to call implemented methods from the base class. Let's start with the code:

 * The interface defines all abstract methods and extends the concrete base class
interface IAnimal extends Animal {
    speak() : void;

 * The abstract base class only defines concrete methods & properties.
class Animal {

    private _impl : IAnimal;

    public name : string;

     * Here comes the clever part: by letting the constructor take an 
     * implementation of IAnimal as argument Animal cannot be instantiated
     * without a valid implementation of the abstract methods.
    constructor(impl : IAnimal, name : string) { = name;
        this._impl = impl;

        // The `impl` object can be used to delegate functionality to the
        // implementation class.
        console.log( + " is born!");

class Dog extends Animal implements IAnimal {
    constructor(name : string) {
        // The child class simply passes itself to Animal
        super(this, name);

    public speak() {

var dog = new Dog("Bob");
dog.speak(); //logs "bark"
console.log(dog instanceof Dog); //true
console.log(dog instanceof Animal); //true
console.log(; //"Bob"

Since the Animal class requires an implementation of IAnimal it's impossible to construct an object of type Animal without having a valid implementation of the abstract methods. Note that for polymorphism to work you need to pass around instances of IAnimal, not Animal. E.g.:

//This works
function letTheIAnimalSpeak(animal: IAnimal) {
    console.log( + " says:");
//This doesn't ("The property 'speak' does not exist on value of type 'Animal')
function letTheAnimalSpeak(animal: Animal) {
    console.log( + " says:");

The main difference here with Erics answer is that the "abstract" base class requires an implementation of the interface, and thus cannot be instantiated on it's own.

How to reset settings in Visual Studio Code?

To reset the default settings I'm not sure, but if you're just trying to get a menu bar back then try right clicking on the anywhere on the toolbar area and clicking the toolbar you need.

Figured out how to reset the settings Click on the tools button on the top, click "Import and Export Settings" and then click "Reset All Settings". Then go through the wizard from there.

What is the difference between a port and a socket?

A socket address is an IP address & port number         # IP address
               :1234    # port number    # socket address

A connection occurs when 2 sockets are bound together.

How to render a DateTime in a specific format in ASP.NET MVC 3?

If all your DateTime types are rendered the same way you can use a custom DateTime display template.

In your Views folder create a folder named "DisplayTemplates" either under your controller specific views folder, or under "Shared" folder (these work similar to partials).

Inside create a file named DateTime.cshtml that takes DateTime as the @model and code how you want to render your date:

@model System.DateTime

Now you can just use this in your views and it should work:

@Html.DisplayFor(mod => mod.MyDateTime)

As long as you follow the convention of adding it to the "DisplayTemplates" folder and naming the file to match the type your are displaying, MVC will automatically use that to display your values. This also works for editing scenarios using "EditorTemplates".

Here's some more information on templates.

Return values from the row above to the current row

Easier way for me is to switch to R1C1 notation and just use R[-1]C1 and switch back when done.

How to convert hashmap to JSON object in Java

I found another way to handle it.

Map obj=new HashMap();    
obj.put("age",new Integer(27));    
obj.put("salary",new Double(600000));   
String jsonText = JSONValue.toJSONString(obj);  

Hope this helps.


How can I detect keydown or keypress event in angular.js?

You can checkout Angular UI @ which provide details event handle callback function for detecting keydown,keyup,keypress (also Enter key, backspace key, alter key ,control key)

<textarea ui-keydown="{27:'keydownCallback($event)'}"></textarea>
<textarea ui-keypress="{13:'keypressCallback($event)'}"></textarea>
<textarea ui-keydown="{'enter alt-space':'keypressCallback($event)'}"> </textarea>
<textarea ui-keyup="{'enter':'keypressCallback($event)'}"> </textarea>

Show/Hide the console window of a C# console application

Here’s how:

using System.Runtime.InteropServices;

static extern IntPtr GetConsoleWindow();

static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

const int SW_HIDE = 0;
const int SW_SHOW = 5;

var handle = GetConsoleWindow();

// Hide
ShowWindow(handle, SW_HIDE);

// Show
ShowWindow(handle, SW_SHOW);

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

One option if the number of keys is small is to use chained gets:

value = myDict.get('lastName', myDict.get('firstName', myDict.get('userName')))

But if you have keySet defined, this might be clearer:

value = None
for key in keySet:
    if key in myDict:
        value = myDict[key]

The chained gets do not short-circuit, so all keys will be checked but only one used. If you have enough possible keys that that matters, use the for loop.

Using Spring MVC Test to unit test multipart POST request

If you are using Spring4/SpringBoot 1.x, then it's worth mentioning that you can add "text" (json) parts as well . This can be done via MockMvcRequestBuilders.fileUpload().file(MockMultipartFile file) (which is needed as method .multipart() is not available in this version):

public void test() throws Exception {

         // file-part
         .file(makeMultipartFile( "file-part" "some/path/to/file.bin", "application/octet-stream"))
        // text part
         .file(makeMultipartTextPart("json-part", "{ \"foo\" : \"bar\" }", "application/json"))


   private MockMultipartFile(String requestPartName, String filename, 
       String contentType, String pathOnClassPath) {

       return new MockMultipartFile(requestPartName, filename, 
          contentType, readResourceFile(pathOnClasspath);

   // make text-part using MockMultipartFile
   private MockMultipartFile makeMultipartTextPart(String requestPartName, 
       String value, String contentType) throws Exception {

       return new MockMultipartFile(requestPartName, "", contentType,

   private byte[] readResourceFile(String pathOnClassPath) throws Exception {
      return Files.readAllBytes(Paths.get(Thread.currentThread().getContextClassLoader()


Understanding lambda in python and using it to pass multiple arguments

Why do you need to state both x and y before the :?

Because it's a function definition and it needs to know what parameters the function accepts, and in what order. It can't just look at the expression and use the variables names in that, because some of those names you might want to use existing local or global variable values for, and even if it did that, it wouldn't know what order it should expect to get them.

Your error message means that Tk is calling your lambda with one argument, while your lambda is written to accept no arguments. If you don't need the argument, just accept one and don't use it. (Demosthenex has the code, I would have posted it but was beaten to it.)

How to check 'undefined' value in jQuery

If you have names of the element and not id we can achieve the undefined check on all text elements (for example) as below and fill them with a default value say 0.0:

var aFieldsCannotBeNull=['ast_chkacc_bwr','ast_savacc_bwr'];
 jQuery.each(aFieldsCannotBeNull,function(nShowIndex,sShowKey) {
   var $_oField = jQuery("input[name='"+sShowKey+"']");
   if($_oField.val().trim().length === 0){

How (and why) to use display: table-cell (CSS)

After days trying to find the answer, I finally found

display: table;

There was surprisingly very little information available online about how to actually getting it to work, even here, so on to the "How":

To use this fantastic piece of code, you need to think back to when tables were the only real way to structure HTML, namely the syntax. To get a table with 2 rows and 3 columns, you'd have to do the following:


Similarly to get CSS to do it, you'd use the following:


<div id="table">
    <div class="tr">
        <div class="td"></div>
        <div class="td"></div>
        <div class="td"></div>
    <div class="tr">
        <div class="td"></div>
        <div class="td"></div>
        <div class="td"></div>


    display: table; 
    display: table-row; 
    display: table-cell; }

As you can see in the JSFiddle example below, the divs in the 3rd column have no content, yet are respecting the auto height set by the text in the first 2 columns. WIN!

It's worth noting that display: table; does not work in IE6 or 7 (thanks, FelipeAls), so depending on your needs with regards to browser compatibility, this may not be the answer that you are seeking.

Change background color of edittext in android

What you should do is to create a 9 patch image for edittext and set that image as edit text background. You can create 9 patches using this website

I am attaching a sample 9 patch image for your reference.Use it as edittext background and you will get an idea.Right click the image and select "save image as". When you save the image dont forget to give its extension as "9.png"

enter image description here

Change the On/Off text of a toggle button Android

It appears you no longer need toggleButton.setTextOff(textOff); and toggleButton.setTextOn(textOn);. The text for each toggled state will change by merely including the relevant xml characteristics. This will override the default ON/OFF text.

    android:textOff="ADD TEXT"
    android:textOn="CLOSE TEXT"

Oracle Insert via Select from multiple tables where one table may not have a row

insert into received_messages(id, content, status)
    values (RECEIVED_MESSAGES_SEQ.NEXT_VAL, empty_blob(), '');

How to run a stored procedure in oracle sql developer?

-- If no parameters need to be passed to a procedure, simply:


node: command not found

The problem is that your PATH does not include the location of the node executable.

You can likely run node as "/usr/local/bin/node".

You can add that location to your path by running the following command to add a single line to your bashrc file:

echo 'export PATH=$PATH:/usr/local/bin' >> $HOME/.bashrc

How to _really_ programmatically change primary and accent color in Android Lollipop?

from an activity you can do:

getWindow().setStatusBarColor(i color);

Class constructor type in typescript?

I am not sure if this was possible in TypeScript when the question was originally asked, but my preferred solution is with generics:

class Zoo<T extends Animal> {
    constructor(public readonly AnimalClass: new () => T) {

This way variables penguin and lion infer concrete type Penguin or Lion even in the TypeScript intellisense.

const penguinZoo = new Zoo(Penguin);
const penguin = new penguinZoo.AnimalClass(); // `penguin` is of `Penguin` type.

const lionZoo = new Zoo(Lion);
const lion = new lionZoo.AnimalClass(); // `lion` is `Lion` type.

Select Pandas rows based on list index

ind_list = [1, 3]

should do the trick! When I index with data frames I always use the .ix() method. Its so much easier and more flexible...

UPDATE This is no longer the accepted method for indexing. The ix method is deprecated. Use .iloc for integer based indexing and .loc for label based indexing.

How do I space out the child elements of a StackPanel?

My approach inherits StackPanel.


<Controls:ItemSpacer Grid.Row="2" Orientation="Horizontal" Height="30" CellPadding="15,0">
    <Label>Test 1</Label>
    <Label>Test 2</Label>
    <Label>Test 3</Label>

All that's needed is the following short class:

using System.Windows;
using System.Windows.Controls;
using System;

namespace Controls
    public class ItemSpacer : StackPanel
        public static DependencyProperty CellPaddingProperty = DependencyProperty.Register("CellPadding", typeof(Thickness), typeof(ItemSpacer), new FrameworkPropertyMetadata(default(Thickness), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnCellPaddingChanged));
        public Thickness CellPadding
                return (Thickness)GetValue(CellPaddingProperty);
                SetValue(CellPaddingProperty, value);
        private static void OnCellPaddingChanged(DependencyObject Object, DependencyPropertyChangedEventArgs e)

        private void SetPadding()
            foreach (UIElement Element in Children)
                (Element as FrameworkElement).Margin = this.CellPadding;

        public ItemSpacer()
            this.LayoutUpdated += PART_Host_LayoutUpdated;

        private void PART_Host_LayoutUpdated(object sender, System.EventArgs e)

JPA Query selecting only specific columns without using Criteria Query?

You can use something like this:

List<Object[]> list = em.createQuery("SELECT p.field1, p.field2 FROM Entity p").getResultList();

then you can iterate over it:

for (Object[] obj : list){

BUT if you have only one field in query, you get a list of the type not from Object[]

calling java methods in javascript code

When it is on server side, use web services - maybe RESTful with JSON.

  • create a web service (for example with Tomcat)
  • call its URL from JavaScript (for example with JQuery or dojo)

When Java code is in applet you can use JavaScript bridge. The bridge between the Java and JavaScript programming languages, known informally as LiveConnect, is implemented in Java plugin. Formerly Mozilla-specific LiveConnect functionality, such as the ability to call static Java methods, instantiate new Java objects and reference third-party packages from JavaScript, is now available in all browsers.

Below is example from documentation. Look at methodReturningString.

Java code:

public class MethodInvocation extends Applet {
    public void noArgMethod() { ... }
    public void someMethod(String arg) { ... }
    public void someMethod(int arg) { ... }
    public int  methodReturningInt() { return 5; }
    public String methodReturningString() { return "Hello"; }
    public OtherClass methodReturningObject() { return new OtherClass(); }

public class OtherClass {
    public void anotherMethod();

Web page and JavaScript code:

<applet id="app"
        code="MethodInvocation" ...>
<script language="javascript">
    var five = app.methodReturningInt();
    var hello = app.methodReturningString();

Iterating through a variable length array

here is an example, where the length of the array is changed during execution of the loop

import java.util.ArrayList;
public class VariableArrayLengthLoop {

public static void main(String[] args) {

    //create new ArrayList
    ArrayList<String> aListFruits = new ArrayList<String>();

    //add objects to ArrayList

    //iterate ArrayList using for loop
    for(int i = 0; i < aListFruits.size(); i++){

        System.out.println( aListFruits.get(i) + " i = "+i );
         if ( i == 2 ) {
                System.out.println( "added now a Fruit to the List "); 

How To Accept a File POST

I used Mike Wasson's answer before I updated all the NuGets in my webapi mvc4 project. Once I did, I had to re-write the file upload action:

    public Task<HttpResponseMessage> Upload(int id)
        HttpRequestMessage request = this.Request;
        if (!request.Content.IsMimeMultipartContent())
            throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.UnsupportedMediaType));

        string root = System.Web.HttpContext.Current.Server.MapPath("~/App_Data/uploads");
        var provider = new MultipartFormDataStreamProvider(root);

        var task = request.Content.ReadAsMultipartAsync(provider).
            ContinueWith<HttpResponseMessage>(o =>
                FileInfo finfo = new FileInfo(provider.FileData.First().LocalFileName);

                string guid = Guid.NewGuid().ToString();

                File.Move(finfo.FullName, Path.Combine(root, guid + "_" + provider.FileData.First().Headers.ContentDisposition.FileName.Replace("\"", "")));

                return new HttpResponseMessage()
                    Content = new StringContent("File uploaded.")
        return task;

Apparently BodyPartFileNames is no longer available within the MultipartFormDataStreamProvider.

How to List All Redis Databases?

Or you can just run the following command and you will see all databases of the Redis instance without firing up redis-cli:

$ redis-cli INFO | grep ^db

How to use shell commands in Makefile

Also, in addition to torek's answer: one thing that stands out is that you're using a lazily-evaluated macro assignment.

If you're on GNU Make, use the := assignment instead of =. This assignment causes the right hand side to be expanded immediately, and stored in the left hand variable.

FILES := $(shell ...)  # expand now; FILES is now the result of $(shell ...)

FILES = $(shell ...)   # expand later: FILES holds the syntax $(shell ...)

If you use the = assignment, it means that every single occurrence of $(FILES) will be expanding the $(shell ...) syntax and thus invoking the shell command. This will make your make job run slower, or even have some surprising consequences.

Batch file include external file for variables

Let's not forget good old parameters. When starting your *.bat or *.cmd file you can add up to nine parameters after the command file name:

call myscript.bat \\path\to\my\file.ext type
call myscript.bat \\path\to\my\file.ext "Del /F"

Example script

The myscript.bat could be something like this:

@Echo Off
Echo The path of this scriptfile %~0
Echo The name of this scriptfile %~n0
Echo The extension of this scriptfile %~x0
If "%~2"=="" (
   Echo Parameter missing, quitting.
   GoTo :EOF
If Not Exist "%~1" (
   Echo File does not exist, quitting.
   GoTo :EOF
Echo Going to %~2 this file: %~1
%~2 "%~1"
If %errorlevel%  NEQ 0 (
   Echo Failed to %~2 the %~1.
@Echo On

Example output

c:\>c:\bats\myscript.bat \\server\path\x.txt type
The path of this scriptfile c:\bats\myscript.bat
The name of this scriptfile myscript
The extension of this scriptfile .bat

Going to type this file: \\server\path\x.txt
This is the content of the file:
Some alphabets: ABCDEFG abcdefg
Some numbers: 1234567890

c:\>c:\bats\myscript.bat \\server\path\x.txt "del /f "
The path of this scriptfile c:\bats\myscript.bat
The name of this scriptfile myscript
The extension of this scriptfile .bat

Going to del /f  this file: \\server\path\x.txt


Spring @Autowired and @Qualifier

You can use @Qualifier along with @Autowired. In fact spring will ask you explicitly select the bean if ambiguous bean type are found, in which case you should provide the qualifier

For Example in following case it is necessary provide a qualifier

public Staff implements Person {}

public Manager implements Person {}

public Payroll {

    private Person person;

    public Payroll(@Qualifier("employee") Person person){
          this.person = person;



In Lombok 1.18.4 it is finally possible to avoid the boilerplate on constructor injection when you have @Qualifier, so now it is possible to do the following:

public Staff implements Person {}

public Manager implements Person {}

public Payroll {
   @Qualifier("employee") private final Person person;

provided you are using the new lombok.config rule copyableAnnotations (by placing the following in lombok.config in the root of your project):

# Copy the Qualifier annotation from the instance variables to the constructor
# see
lombok.copyableAnnotations += org.springframework.beans.factory.annotation.Qualifier

This was recently introduced in latest lombok 1.18.4.


If you are using field or setter injection then you have to place the @Autowired and @Qualifier on top of the field or setter function like below(any one of them will work)

public Payroll {
   @Autowired @Qualifier("employee") private final Person person;


public Payroll {
   private final Person person;
   public void setPerson(Person person) {
     this.person = person;

If you are using constructor injection then the annotations should be placed on constructor, else the code would not work. Use it like below -

public Payroll {

    private Person person;

    public Payroll(@Qualifier("employee") Person person){
          this.person = person;


Regex match everything after question mark?


If you want to match all chars after "?" you can use a group to match any char, and you'd better use the "$" sign to indicate the end of line.

How to use jQuery with TypeScript

FOR Visual Studio Code

What works for me is to make sure I do the standard JQuery library loading via a < script > tag in the index.html.


npm install --save @types/jquery

Now the JQuery $ functions are available in all .ts files, no need of any other imports.

`React/RCTBridgeModule.h` file not found

In my case this particular problem happened when I was trying to archive a 0.40+ react-native app for iOS (solution was found here: Reliable build on ^0.39.2 fails when upgrading to ^0.40.0).

What happened was that Xcode was trying to build the react-native libraries in parallel and was building libraries with implicit react dependencies before actually building the react library.

The solution in my case was to:

  1. Disable the parallel builds:

    • Xcode menu -> Product -> Scheme -> Manage Shemes...
    • Double click on your application
    • Build tab -> uncheck Parallelize Build
  2. Add react as a project dependecy

    • Xcode Project Navigator -> drag React.xcodeproj from Libraries to root tree
    • Build Phases Tab -> Target Dependencies -> + -> add React

How to use zIndex in react-native

UPDATE: Supposedly, zIndex has been added to the react-native library. I've been trying to get it to work without success. Check here for details of the fix.

PHP MySQL Query Where x = $variable

What you are doing right now is you are adding . on the string and not concatenating. It should be,

$result = mysqli_query($con,"SELECT `note` FROM `glogin_users` WHERE email = '".$email."'");

or simply

$result = mysqli_query($con,"SELECT `note` FROM `glogin_users` WHERE email = '$email'");

How to block calls in android

It is possible and you don't need to code it on your own.

Just set the ringer volume to zero and vibration to none if incomingNumber equals an empty string. Thats it ...

Its just done for you with the application Nostalk from Android Market. Just give it a try ...

Now() function with time trim

I would prefer to make a function that doesn't work with strings:

' Procedure : RemoveTimeFromDate
' Author    : berend.nieuwhof
' Date      : 15-8-2013
' Purpose   : removes the time part of a String and returns the date as a date
Public Function RemoveTimeFromDate(DateTime As Date) As Date

    Dim dblNumber As Double

    RemoveTimeFromDate = CDate(Floor(CDbl(DateTime)))

End Function

Private Function Floor(ByVal x As Double, Optional ByVal Factor As Double = 1) As Double
    Floor = Int(x / Factor) * Factor
End Function

Post-increment and Pre-increment concept?


int x, y, z;

x = 1;
y = x++; //this means: y is assigned the x value first, then increase the value of x by 1. Thus y is 1;
z = x; //the value of x in this line and the rest is 2 because it was increased by 1 in the above line. Thus z is 2.


int x, y, z;

x = 1;
y = ++x; //this means: increase the value of x by 1 first, then assign the value of x to y. The value of x in this line and the rest is 2. Thus y is 2.
z = x; //the value of x in this line is 2 as stated above. Thus z is 2.

Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path $

I have faced this problem and I made research and didn't get anything, so I was trying and finally, I knew the cause of this problem. the problem on the API, make sure you have a good variable name I used $start_date and it caused the problem, so I try $startdate and it works!

as well make sure you send all parameter that declare on API, for example, $startdate = $_POST['startdate']; $enddate = $_POST['enddate'];

you have to pass this two variable from the retrofit.

as well if you use date on SQL statement, try to put it inside '' like '2017-07-24'

I hope it helps you.

Get the first element of each tuple in a list in Python

If you don't want to use list comprehension by some reasons, you can use map and operator.itemgetter:

>>> from operator import itemgetter
>>> rows = [(1, 2), (3, 4), (5, 6)]
>>> map(itemgetter(1), rows)
[2, 4, 6]

Changing CSS style from ASP.NET code

C#, because I don't want to typo the VB syntax.


<div runat="server" id="divControl">...</div>

Class of the Page:

protected System.Web.UI.HtmlControls.HtmlGenericControl divControl;

OnLoad/Other function:

divControl.Style.Add("height", number / anotherNumer);

List all tables in postgresql information_schema

You should be able to just run select * from information_schema.tables to get a listing of every table being managed by Postgres for a particular database.

You can also add a where table_schema = 'information_schema' to see just the tables in the information schema.

How to get screen dimensions as pixels in Android

You can do get the height size using :


and the width size using


Execute JavaScript code stored as a string

I was answering similar question and got yet another idea how to achieve this without use of eval():

const source = "alert('test')";
const el = document.createElement("script");
el.src = URL.createObjectURL(new Blob([source], { type: 'text/javascript' }));

In the code above you basically create Blob, containing your script, in order to create Object URL (representation of File or Blob object in browser memory). Since you have src property on <script> tag, the script will be executed the same way as if it was loaded from any other URL.

Why does C++ code for testing the Collatz conjecture run faster than hand-written assembly?

From comments:

But, this code never stops (because of integer overflow) !?! Yves Daoust

For many numbers it will not overflow.

If it will overflow - for one of those unlucky initial seeds, the overflown number will very likely converge toward 1 without another overflow.

Still this poses interesting question, is there some overflow-cyclic seed number?

Any simple final converging series starts with power of two value (obvious enough?).

2^64 will overflow to zero, which is undefined infinite loop according to algorithm (ends only with 1), but the most optimal solution in answer will finish due to shr rax producing ZF=1.

Can we produce 2^64? If the starting number is 0x5555555555555555, it's odd number, next number is then 3n+1, which is 0xFFFFFFFFFFFFFFFF + 1 = 0. Theoretically in undefined state of algorithm, but the optimized answer of johnfound will recover by exiting on ZF=1. The cmp rax,1 of Peter Cordes will end in infinite loop (QED variant 1, "cheapo" through undefined 0 number).

How about some more complex number, which will create cycle without 0? Frankly, I'm not sure, my Math theory is too hazy to get any serious idea, how to deal with it in serious way. But intuitively I would say the series will converge to 1 for every number : 0 < number, as the 3n+1 formula will slowly turn every non-2 prime factor of original number (or intermediate) into some power of 2, sooner or later. So we don't need to worry about infinite loop for original series, only overflow can hamper us.

So I just put few numbers into sheet and took a look on 8 bit truncated numbers.

There are three values overflowing to 0: 227, 170 and 85 (85 going directly to 0, other two progressing toward 85).

But there's no value creating cyclic overflow seed.

Funnily enough I did a check, which is the first number to suffer from 8 bit truncation, and already 27 is affected! It does reach value 9232 in proper non-truncated series (first truncated value is 322 in 12th step), and the maximum value reached for any of the 2-255 input numbers in non-truncated way is 13120 (for the 255 itself), maximum number of steps to converge to 1 is about 128 (+-2, not sure if "1" is to count, etc...).

Interestingly enough (for me) the number 9232 is maximum for many other source numbers, what's so special about it? :-O 9232 = 0x2410 ... hmmm.. no idea.

Unfortunately I can't get any deep grasp of this series, why does it converge and what are the implications of truncating them to k bits, but with cmp number,1 terminating condition it's certainly possible to put the algorithm into infinite loop with particular input value ending as 0 after truncation.

But the value 27 overflowing for 8 bit case is sort of alerting, this looks like if you count the number of steps to reach value 1, you will get wrong result for majority of numbers from the total k-bit set of integers. For the 8 bit integers the 146 numbers out of 256 have affected series by truncation (some of them may still hit the correct number of steps by accident maybe, I'm too lazy to check).

define a List like List<int,string>?

For that, you could use a Dictionary where the int is the key.

new Dictionary<int, string>();

If you really want to use a list, it could be a List<Tuple<int,string>>() but, Tuple class is readonly, so you have to recreate the instance to modifie it.

Must declare the scalar variable

Just FYI, I know this is an old post, but depending on the database COLLATION settings you can get this error on a statement like this,

SET @sql = @Sql + ' WHERE RowNum BETWEEN @RowFrom AND @RowTo;';

if for example you typo the S in the

SET @sql = @***S***ql 

sorry to spin off the answers already posted here, but this is an actual instance of the error reported.

Note also that the error will not display the capital S in the message, I am not sure why, but I think it is because the

Set @sql =

is on the left of the equal sign.

How to update array value javascript?

Why not use an object1?

var dict = { "a": 1, "b": 2, "c": 3 };

Then you can update it like so

dict.a = 23;


dict["a"] = 23;

If you wan't to delete2 a particular key, it's as simple as:

delete dict.a;

1 See Objects vs arrays in Javascript for key/value pairs.
2 See the delete operator.

How to configure "Shorten command line" method for whole project in IntelliJ

The latest 2020 build doesn't have the shorten command line option by default we need to add that option from the configuration.

Run > Edit Configurations > Select the corresponding run configuration and click on Modify options for adding the shorten command-line configuration to the UI. enter image description here

Select the shorten command line option enter image description here

Now choose jar manifest from the shorten command line option enter image description here

How to Find the Default Charset/Encoding in Java?



it seems to be the same encoding as the one used in your system's command line.

start MySQL server from command line on Mac OS Lion


mysql.server start

mysql.server stop

mysql.server restart

python: unhashable type error


You don't show what data is, but apparently when you loop through its rows, row[11] is turning out to be a list. Lists are mutable objects which means they cannot be used as dictionary keys. Trying to use row[11] as a key causes the defaultdict to complain that it is a mutable, i.e. unhashable, object.

The easiest fix is to change row[11] from a list to a tuple. Either by doing

counter[tuple(row[11])] += 1

or by fixing it in the caller before data is passed to medications_minimum3. A tuple simply an immutable list, so it behaves exactly like a list does except you cannot change it once it is created.

json Uncaught SyntaxError: Unexpected token :

I have spent the last few days trying to figure this out myself. Using the old json dataType gives you cross origin problems, while setting the dataType to jsonp makes the data "unreadable" as explained above. So there are apparently two ways out, the first hasn't worked for me but seems like a potential solution and that I might be doing something wrong. This is explained here [ ].

The one that worked for me is as follows: 1- download the ajax cross origin plug in [ ]. 2- add a script link to it just below the normal jQuery link. 3- add the line "crossOrigin: true," to your ajax function.

Good to go! here is my working code for this:

      crossOrigin: true,_x000D_
      url : ",151.195&radius=5000&type=ATM&keyword=ATM&key=MyKey",_x000D_
      type : "GET",_x000D_

When should I use UNSIGNED and SIGNED INT in MySQL?

UNSIGNED only stores positive numbers (or zero). On the other hand, signed can store negative numbers (i.e., may have a negative sign).

Here's a table of the ranges of values each INTEGER type can store:

MySQL INTEGER types and lengths

UNSIGNED ranges from 0 to n, while signed ranges from about -n/2 to n/2.

In this case, you have an AUTO_INCREMENT ID column, so you would not have negatives. Thus, use UNSIGNED. If you do not use UNSIGNED for the AUTO_INCREMENT column, your maximum possible value will be half as high (and the negative half of the value range would go unused).

Change SQLite database mode to read-write

If using Android.

Make sure you have added the permission to write to your EXTERNAL_STORAGE to your AndroidManifest.xml.

Add this line to your AndroidManifest.xml file above and outside your <application> tag.

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

This will allow your application to write to the sdcard. This will help if your EXTERNAL_STORAGE is where you have stored your database on the device.

What is "with (nolock)" in SQL Server?

Another case where it's usually okay is in a reporting database, where data is perhaps already aged and writes just don't happen. In this case, though, the option should be set at the database or table level by the administrator by changing the default isolation level.

In the general case: you can use it when you are very sure that it's okay to read old data. The important thing to remember is that its very easy to get that wrong. For example, even if it's okay at the time you write the query, are you sure something won't change in the database in the future to make these updates more important?

I'll also 2nd the notion that it's probably not a good idea in banking app. Or inventory app. Or anywhere you're thinking about transactions.

How to select a range of the second row to the last row

Try this:

Dim Lastrow As Integer
Lastrow = ActiveSheet.Cells(Rows.Count, 1).End(xlUp).Row

Range("A2:L" & Lastrow).Select

Let's pretend that the value of Lastrow is 50. When you use the following:

Range("A2:L2" & Lastrow).Select

Then it is selecting a range from A2 to L250.

How can I get a file's size in C++?

How to use lseek/fseek/stat/fstat to get filesize ?

#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>

fseek_filesize(const char *filename)
    FILE *fp = NULL;
    long off;

    fp = fopen(filename, "r");
    if (fp == NULL)
        printf("failed to fopen %s\n", filename);

    if (fseek(fp, 0, SEEK_END) == -1)
        printf("failed to fseek %s\n", filename);

    off = ftell(fp);
    if (off == (long)-1)
        printf("failed to ftell %s\n", filename);

    printf("[*] fseek_filesize - file: %s, size: %ld\n", filename, off);

    if (fclose(fp) != 0)
        printf("failed to fclose %s\n", filename);

fstat_filesize(const char *filename)
    int fd;
    struct stat statbuf;

    fd = open(filename, O_RDONLY, S_IRUSR | S_IRGRP);
    if (fd == -1)
        printf("failed to open %s\n", filename);

    if (fstat(fd, &statbuf) == -1)
        printf("failed to fstat %s\n", filename);

    printf("[*] fstat_filesize - file: %s, size: %lld\n", filename, statbuf.st_size);

    if (close(fd) == -1)
        printf("failed to fclose %s\n", filename);

stat_filesize(const char *filename)
    struct stat statbuf;

    if (stat(filename, &statbuf) == -1)
        printf("failed to stat %s\n", filename);

    printf("[*] stat_filesize - file: %s, size: %lld\n", filename, statbuf.st_size);


seek_filesize(const char *filename)
    int fd;
    off_t off;

    if (filename == NULL)
        printf("invalid filename\n");

    fd = open(filename, O_RDONLY, S_IRUSR | S_IRGRP);
    if (fd == -1)
        printf("failed to open %s\n", filename);

    off = lseek(fd, 0, SEEK_END);
    if (off == (off_t)-1)
        printf("failed to lseek %s\n", filename);

    printf("[*] seek_filesize - file: %s, size: %lld\n", filename, off);

    if (close(fd) == -1)
        printf("failed to close %s\n", filename);

main(int argc, const char *argv[])
    int i;

    if (argc < 2)
        printf("%s <file1> <file2>...\n", argv[0]);

    for(i = 1; i < argc; i++)

    return 0;

How to kill a running SELECT statement

If you want to stop process you can kill it manually from task manager onother side if you want to stop running query in DBMS you can stop as given here for ms sqlserver T-SQL STOP or ABORT command in SQL Server Hope it helps you

What is the best way to generate a unique and short file name in Java

Why not use synchronized to process multi thread. here is my solution,It's can generate a short file name , and it's unique.

private static synchronized String generateFileName(){
    String name = make(index);
    index ++;
    return name;
private static String make(int index) {
    if(index == 0) return "";
    return String.valueOf(chars[index % chars.length]) + make(index / chars.length);
private static int index = 1;
private static char[] chars = {'a','b','c','d','e','f','g',

blew is main function for test , It's work.

public static void main(String[] args) {
    List<String> names = new ArrayList<>();
    List<Thread> threads = new ArrayList<>();
    for (int i = 0; i < 100; i++) {
        Thread thread = new Thread(new Runnable() {
            public void run() {
                for (int i = 0; i < 1000; i++) {
                    String name = generateFileName();

    for (int i = 0; i < 10; i++) {
        try {
        } catch (InterruptedException e) {



Web scraping with Java

Your best bet is to use Selenium Web Driver since it

  1. Provides visual feedback to the coder (see your scraping in action, see where it stops)

  2. Accurate and Consistent as it directly controls the browser you use.

  3. Slow. Doesn't hit web pages like HtmlUnit does but sometimes you don't want to hit too fast.

    Htmlunit is fast but is horrible at handling Javascript and AJAX.

Python & Matplotlib: Make 3D plot interactive in Jupyter Notebook


%matplotlib notebook

see jakevdp reply here

EDIT for JupyterLab users:

Follow the instructions to install jupyter-matplotlib

Then the magic command above is no longer needed, as in the example:

# Enabling the `widget` backend.
# This requires jupyter-matplotlib a.k.a. ipympl.
# ipympl can be install via pip or conda.
%matplotlib widget
# aka import ipympl

import matplotlib.pyplot as plt

plt.plot([0, 1, 2, 2])

Finally, note Maarten Breddels' reply; IMHO ipyvolume is indeed very impressive (and useful!).

XML Schema How to Restrict Attribute by Enumeration

The numerical value seems to be missing from your price definition. Try the following:

<xs:simpleType name="curr">
  <xs:restriction base="xs:string">
    <xs:enumeration value="pounds" />
    <xs:enumeration value="euros" />
    <xs:enumeration value="dollars" />

<xs:element name="price">
            <xs:extension base="xs:decimal">
              <xs:attribute name="currency" type="curr"/>

Compile c++14-code with g++

Follow the instructions at to set up the gcc version you need - gcc 5 or gcc 6 - on Ubuntu 14.04. The instructions include configuring update-alternatives to allow you to switch between versions as you need to.

form confirm before submit

sample fiddle:


<form id="uguu" action="">
    <input type="submit" value="text 1" />


$("#uguu").submit(function() {
    if ($("input[type='submit']").val() == "text 1") {
        alert("Please confirm if everything is correct");
        $("input[type='submit']").val("text 2");
        return false;

Angular 2 @ViewChild annotation returns undefined

My solution to this was to move the ngIf from outside of the child component to inside of the child component on a div that wrapped the whole section of html. That way it was still getting hidden when it needed to be, but was able to load the component and I could reference it in the parent.

How to add an extra language input to Android?

I don't know about sliding the space bar. I have a small box on the left of my keyboard that indicates which language is selected ( when english is selected it shows the words EN with a small microphone on top. Being that I also have spanish as one of my languages, I just tap that button and it swithces back and forth from spanish to english.

Difference between r+ and w+ in fopen()

There are 2 differences, unlike r+, w+ will:

  • create the file if it does not already exist
  • first truncate it, i.e., will delete its contents

How do I get an element to scroll into view, using jQuery?

My UI has a vertical scrolling list of thumbs within a thumbbar The goal was to make the current thumb right in the center of the thumbbar. I started from the approved answer, but found that there were a few tweaks to truly center the current thumb. hope this helps someone else.


<ul id='thumbbar'>
    <li id='thumbbar-123'></li>
    <li id='thumbbar-124'></li>
    <li id='thumbbar-125'></li>


// scroll the current thumb bar thumb into view
heightbar   = $('#thumbbar').height();
heightthumb = $('#thumbbar-' + pageid).height();
offsetbar   = $('#thumbbar').scrollTop();

    scrollTop: - heightbar / 2 - offsetbar - 20

Differences between INDEX, PRIMARY, UNIQUE, FULLTEXT in MySQL?


  • KEY or INDEX refers to a normal non-unique index. Non-distinct values for the index are allowed, so the index may contain rows with identical values in all columns of the index. These indexes don't enforce any restraints on your data so they are used only for access - for quickly reaching certain ranges of records without scanning all records.

  • UNIQUE refers to an index where all rows of the index must be unique. That is, the same row may not have identical non-NULL values for all columns in this index as another row. As well as being used to quickly reach certain record ranges, UNIQUE indexes can be used to enforce restraints on data, because the database system does not allow the distinct values rule to be broken when inserting or updating data.

    Your database system may allow a UNIQUE index to be applied to columns which allow NULL values, in which case two rows are allowed to be identical if they both contain a NULL value (the rationale here is that NULL is considered not equal to itself). Depending on your application, however, you may find this undesirable: if you wish to prevent this, you should disallow NULL values in the relevant columns.

  • PRIMARY acts exactly like a UNIQUE index, except that it is always named 'PRIMARY', and there may be only one on a table (and there should always be one; though some database systems don't enforce this). A PRIMARY index is intended as a primary means to uniquely identify any row in the table, so unlike UNIQUE it should not be used on any columns which allow NULL values. Your PRIMARY index should be on the smallest number of columns that are sufficient to uniquely identify a row. Often, this is just one column containing a unique auto-incremented number, but if there is anything else that can uniquely identify a row, such as "countrycode" in a list of countries, you can use that instead.

    Some database systems (such as MySQL's InnoDB) will store a table's records on disk in the order in which they appear in the PRIMARY index.

  • FULLTEXT indexes are different from all of the above, and their behaviour differs significantly between database systems. FULLTEXT indexes are only useful for full text searches done with the MATCH() / AGAINST() clause, unlike the above three - which are typically implemented internally using b-trees (allowing for selecting, sorting or ranges starting from left most column) or hash tables (allowing for selection starting from left most column).

    Where the other index types are general-purpose, a FULLTEXT index is specialised, in that it serves a narrow purpose: it's only used for a "full text search" feature.


  • All of these indexes may have more than one column in them.

  • With the exception of FULLTEXT, the column order is significant: for the index to be useful in a query, the query must use columns from the index starting from the left - it can't use just the second, third or fourth part of an index, unless it is also using the previous columns in the index to match static values. (For a FULLTEXT index to be useful to a query, the query must use all columns of the index.)

Twitter Bootstrap dropdown menu

I had a similar problem and it was the version of bootstrap.js included in my visual studio project. I linked to here and it worked great

 <script src="//"></script>

Variable might not have been initialized error

because of your a and b variable is not have been initialized. You must initialized this variables for excample if you declare this variable like this int a=0; int b=0; than your code run without error.

Executing periodic actions in Python

Simply sleeping for 10 seconds or using threading.Timer(10,foo) will result in start time drift. (You may not care about this, or it may be a significant source of problems depending on your exact situation.) There can be two causes for this - inaccuracies in the wake up time of your thread or execution time for your function.

You can see some results at the end of this post, but first an example of how to fix it. You need to track when your function should next be called as opposed to when it actually got called and account for the difference.

Here's a version that drifts slightly:

import datetime, threading

def foo():
    threading.Timer(1, foo).start()


Its output looks like this:

2013-08-12 13:05:36.483580
2013-08-12 13:05:37.484931
2013-08-12 13:05:38.485505
2013-08-12 13:05:39.486945
2013-08-12 13:05:40.488386
2013-08-12 13:05:41.489819
2013-08-12 13:05:42.491202
2013-08-12 13:05:43.492486
2013-08-12 13:05:44.493865
2013-08-12 13:05:45.494987
2013-08-12 13:05:46.496479
2013-08-12 13:05:47.497824
2013-08-12 13:05:48.499286
2013-08-12 13:05:49.500232

You can see that the sub-second count is constantly increasing and thus, the start time is "drifting".

This is code that correctly accounts for drift:

import datetime, threading, time

next_call = time.time()

def foo():
  global next_call
  next_call = next_call+1
  threading.Timer( next_call - time.time(), foo ).start()


Its output looks like this:

2013-08-12 13:21:45.292565
2013-08-12 13:21:47.293000
2013-08-12 13:21:48.293939
2013-08-12 13:21:49.293327
2013-08-12 13:21:50.293883
2013-08-12 13:21:51.293070
2013-08-12 13:21:52.293393

Here you can see that there is no longer any increase in the sub-second times.

If your events are occurring really frequently you may want to run the timer in a single thread, rather than starting a new thread for each event. While accounting for drift this would look like:

import datetime, threading, time

def foo():
    next_call = time.time()
    while True:
        next_call = next_call+1;
        time.sleep(next_call - time.time())

timerThread = threading.Thread(target=foo)

However your application will not exit normally, you'll need to kill the timer thread. If you want to exit normally when your application is done, without manually killing the thread, you should use

timerThread = threading.Thread(target=foo)
timerThread.daemon = True

Why do table names in SQL Server start with "dbo"?

dbo is the default schema in SQL Server. You can create your own schemas to allow you to better manage your object namespace.

Spark - load CSV file as DataFrame?

To read from relative path on the system use System.getProperty method to get current directory and further uses to load the file using relative path.

scala> val path = System.getProperty("user.dir").concat("/../2015-summary.csv")
scala> val csvDf ="inferSchema","true").option("header", "true").csv(path)
scala> csvDf.take(3)

spark:2.4.4 scala:2.11.12

How to adjust text font size to fit textview

I had this pain in my projects for soooo long until I found this library:

compile 'me.grantland:autofittextview:0.2.+'

You just need to add the xml by your needs and it's done. For example:


Is it possible to write to the console in colour in .NET?

Above comments are both solid responses, however note that they aren't thread safe. If you are writing to the console with multiple threads, changing colors will add a race condition that can create some strange looking output. It is simple to fix though:

public class ConsoleWriter
    private static object _MessageLock= new object();

    public void WriteMessage(string message)
        lock (_MessageLock)
            Console.BackgroundColor = ConsoleColor.Red;

How to get < span > value?

<div id="test">
<div id="test2"></div>

<script type="text/javascript">
    var getDiv = document.getElementById('test');
    var getSpan = getDiv.getElementsByTagName('span');???
    var divDump = document.getElementById('test2');

    for (var i=0; i<getSpan.length; i++) {
        divDump.innerHTML = divDump.innerHTML + ' ' + getSpan[i].innerHTML;


sed: print only matching group

Match the whole line, so add a .* at the beginning of your regex. This causes the entire line to be replaced with the contents of the group

echo "foo bar <foo> bla 1 2 3.4" |
 sed -n  's/.*\([0-9][0-9]*[\ \t][0-9.]*[ \t]*$\)/\1/p'
2 3.4

ASP.NET MVC JsonResult Date Format

Moment.js is an extensive datetime library that also supports this.

ex: moment("/Date(1198908717056-0700)/")

It might help. plunker output

How to post data in PHP using file_get_contents?

Sending an HTTP POST request using file_get_contents is not that hard, actually : as you guessed, you have to use the $context parameter.

There's an example given in the PHP manual, at this page : HTTP context options (quoting) :

$postdata = http_build_query(
        'var1' => 'some content',
        'var2' => 'doh'

$opts = array('http' =>
        'method'  => 'POST',
        'header'  => 'Content-Type: application/x-www-form-urlencoded',
        'content' => $postdata

$context  = stream_context_create($opts);

$result = file_get_contents('', false, $context);

Basically, you have to create a stream, with the right options (there is a full list on that page), and use it as the third parameter to file_get_contents -- nothing more ;-)

As a sidenote : generally speaking, to send HTTP POST requests, we tend to use curl, which provides a lot of options an all -- but streams are one of the nice things of PHP that nobody knows about... too bad...

How to replace multiple strings in a file using PowerShell

With version 3 of PowerShell you can chain the replace calls together:

 (Get-Content $sourceFile) | ForEach-Object {
    $_.replace('something1', 'something1').replace('somethingElse1', 'somethingElse2')
 } | Set-Content $destinationFile

Is it possible to use 'else' in a list comprehension?

Also, would I be right in concluding that a list comprehension is the most efficient way to do this?

Maybe. List comprehensions are not inherently computationally efficient. It is still running in linear time.

From my personal experience: I have significantly reduced computation time when dealing with large data sets by replacing list comprehensions (specifically nested ones) with for-loop/list-appending type structures you have above. In this application I doubt you will notice a difference.

Getter and Setter of Model object in Angular 4

The way you declare the date property as an input looks incorrect but its hard to say if it's the only problem without seeing all your code. Rather than using @Input('date') declare the date property like so: private _date: string;. Also, make sure you are instantiating the model with the new keyword. Lastly, access the property using regular dot notation.

Check your work against this example from :

let passcode = "secret passcode";

class Employee {
    private _fullName: string;

    get fullName(): string {
        return this._fullName;

    set fullName(newName: string) {
        if (passcode && passcode == "secret passcode") {
            this._fullName = newName;
        else {
            console.log("Error: Unauthorized update of employee!");

let employee = new Employee();
employee.fullName = "Bob Smith";
if (employee.fullName) {

And here is a plunker demonstrating what it sounds like you're trying to do:

How do you execute an arbitrary native command from a string?

If you want to use the call operator, the arguments can be an array stored in a variable:

$prog = 'c:\windows\system32\cmd.exe'
$myargs = '/c','dir','/x'
& $prog $myargs

The call operator works with ApplicationInfo objects too.

$prog = get-command cmd
$myargs = -split '/c dir /x'
& $prog $myargs

XAMPP Apache won't start

It's simple if you guys have and use your skype ports turn them ports off from the skype settings->Connections and unmark the port like where it sez ports 80 till 443.

Problem Solved!!!

Moving uncommitted changes to a new branch

Just move to the new branch. The uncommited changes get carried over.

git checkout -b ABC_1

git commit -m <message>

Identifying Exception Type in a handler Catch Block

When dealing with situations where I don't exactly know what type of exception might come out of a method, a little "trick" I like to do is to recover the Exception's class name and add it to the error log so there is more information.


} catch ( Exception caughtEx )
   throw new Exception("Unknown Exception Thrown: "
                       + "\n  Type:    " + caughtEx.GetType().Name
                       + "\n  Message: " + caughtEx.Message);

I do vouch for always handling Exceptions types individually, but the extra bit of info can be helpful, specially when dealing with code from people who love to capture catch-all generic types.

How to strip HTML tags with jQuery?

You can use the existing split function

One easy and choppy exemple:

var str = '<p> example ive got a string</P>';
var substr = str.split('<p> ');
// substr[0] contains ""
// substr[1] contains "example ive got a string</P>"
var substr2 = substr [1].split('</p>');
// substr2[0] contains "example ive got a string"
// substr2[1] contains ""

The example is just to show you how the split works.

How to increase font size in the Xcode editor?

I also found that you can change the fonts for printing which is controlled by the "Printing" theme. I wanted the print output to be the same as the default, but with a larger font.

  1. rename "printing" to "printing1" (select the printing theme and click on it and it should allow you to change the name).

  2. click the "+" and select "Default" from the "New Theme From Template" selection

  3. rename it "Printing"

  4. click in the font area for "Source Editor" and cmd-A to select all of the fonts

  5. change the font size to some desired value (I like 12 point) by clicking the "T" icon and selecting the desired font size

After this the printouts should match the new "Printing" template (i.e. in color and bigger, or however you make the template), the key is that printing takes its formating from the "Printing" Theme.

Factory Pattern. When to use factory methods?

Factory classes are useful for when the object type that they return has a private constructor, when different factory classes set different properties on the returning object, or when a specific factory type is coupled with its returning concrete type.

WCF uses ServiceHostFactory classes to retrieve ServiceHost objects in different situations. The standard ServiceHostFactory is used by IIS to retrieve ServiceHost instances for .svc files, but a WebScriptServiceHostFactory is used for services that return serializations to JavaScript clients. ADO.NET Data Services has its own special DataServiceHostFactory and ASP.NET has its ApplicationServicesHostFactory since its services have private constructors.

If you only have one class that's consuming the factory, then you can just use a factory method within that class.

What's the difference between next() and nextLine() methods from Scanner class?

  • Just for another example of and nextLine() is that like below : nextLine() does not let user type while next() makes Scanner wait and read the input.

     Scanner sc = new Scanner(;
     do {
        System.out.println("The values on dice are :");
        for(int i = 0; i < n; i++) {
            System.out.println(ran.nextInt(6) + 1);
        System.out.println("Continue : yes or no");
     } while("yes"));
    // while(sc.nextLine().equals("yes"));

Merge two Excel tables Based on matching data in Columns

Teylyn's answer worked great for me, but I had to modify it a bit to get proper results. I want to provide an extended explanation for whoever would need it.

My setup was as follows:

  • Sheet1: full data of 2014
  • Sheet2: updated rows for 2015 in A1:D50, sorted by first column
  • Sheet3: merged rows
  • My data does not have a header row

I put the following formula in cell A1 of Sheet3:


Read this as follows: Take the value of the first column in Sheet1 (old data). Look up in Sheet2 (updated rows). If present, output the value from the indicated column in Sheet2. On error, output the value for the current column of Sheet1.


  • In my version of the formula, ";" is used as parameter separator instead of ",". That is because I am located in Europe and we use the "," as decimal separator. Change ";" back to "," if you live in a country where "." is the decimal separator.

  • A$1: means always take column 1 when copying the formula to a cell in a different column. $A$1 means: always take the exact cell A1, even when copying the formula to a different row or column.

After pasting the formula in A1, I extended the range to columns B, C, etc., until the full width of my table was reached. Because of the $-signs used, this gives the following formula's in cells B1, C1, etc.:


and so forth. Note that the lookup is still done in the first column. This is because VLOOKUP needs the lookup data to be sorted on the column where the lookup is done. The output column is however the column where the formula is pasted.

Next, select a rectangle in Sheet 3 starting at A1 and having the size of the data in Sheet1 (same number of rows and columns). Press Ctrl-D to copy the formulas of the first row to all selected cells.

Cells A2, A3, etc. will get these formulas:


Because of the use of $-signs, the lookup area is constant, but input data is used from the current row.

mssql '5 (Access is denied.)' error during restoring database

The account does not have access to the location for backup file. Take the following steps to access the SQL Server Configuration Manager via Computer Manager easily

  1. Click the Windows key + R to open the Run window.
  2. Type compmgmt.msc in the Open: box.
  3. Click OK.
  4. Expand Services and Applications.
  5. Expand SQL Server Configuration Manager.
  6. Change User Account in Log On As tab .

Now you can Restore Data Base easily

Can you use if/else conditions in CSS?

You could create two separate stylesheets and include one of them based on the comparison result

In one of the you can put

background-position : 150px 8px;

In the other one

background-position : 4px 8px;

I think that the only check you can perform in CSS is browser recognition:


How should the ViewModel close the form?

I ended up blending Joe White's answer and some code from Adam Mills's answer, since I needed to show a user control in a programmatically created window. So the DialogCloser need not be on the window, it can be on the user control itself

<UserControl ...
    xw:DialogCloser.DialogResult="{Binding DialogResult}">

And the DialogCloser will find the window of the user control if it was not attached to the window itself.

namespace Wpf
  public static class DialogCloser
    public static readonly DependencyProperty DialogResultProperty =
            new PropertyMetadata(DialogResultChanged));

    private static void DialogResultChanged(
        DependencyObject d,
        DependencyPropertyChangedEventArgs e)
      var window = d.GetWindow();
      if (window != null)
        window.DialogResult = e.NewValue as bool?;

    public static void SetDialogResult(DependencyObject target, bool? value)
      target.SetValue(DialogResultProperty, value);

  public static class Extensions
    public static Window GetWindow(this DependencyObject sender_)
      Window window = sender_ as Window;        
      return window ?? Window.GetWindow( sender_ );

XPath to select element based on childs child value

Almost there. In your predicate, you want a relative path, so change

./book[/author/name = 'John'] 

to either

./book[author/name = 'John'] 


./book[./author/name = 'John'] 

and you will match your element. Your current predicate goes back to the root of the document to look for an author.

Create Hyperlink in Slack

In addition to the ?ShiftU/CtrlShiftU solution, you can also add a link quickly by doing the following:

  1. Copy a URL to the clipboard
  2. Select the text in a slack message you are writing that you want to be a link
  3. Press ?V on Mac or CtrlV

I couldn't find it documented anywhere, but it works, and seems very handy.

dd: How to calculate optimal blocksize?

The optimal block size depends on various factors, including the operating system (and its version), and the various hardware buses and disks involved. Several Unix-like systems (including Linux and at least some flavors of BSD) define the st_blksize member in the struct stat that gives what the kernel thinks is the optimal block size:

#include <sys/stat.h>
#include <stdio.h>

int main(void)
    struct stat stats;

    if (!stat("/", &stats))
        printf("%u\n", stats.st_blksize);

The best way may be to experiment: copy a gigabyte with various block sizes and time that. (Remember to clear kernel buffer caches before each run: echo 3 > /proc/sys/vm/drop_caches).

However, as a rule of thumb, I've found that a large enough block size lets dd do a good job, and the differences between, say, 64 KiB and 1 MiB are minor, compared to 4 KiB versus 64 KiB. (Though, admittedly, it's been a while since I did that. I use a mebibyte by default now, or just let dd pick the size.)

Are there any Open Source alternatives to Crystal Reports?

How about i-net Clear Reports (used to be i-net Crystal-Clear).

Though not free, you should also consider this low-cost, non-free, non-open-source reporting solution that can fully compete with Crystal Reports - and is Java-based.

I think it's even more cost efficient than "free ones". A small company may have to think closely about free things, but will then have to invest into manpower to find out how everything works and so on. Large companies will for sure subscribe to premium support services that cost a lot. See this article for reference

i-net Clear Reports has a very low price tag with great support for free and even better premium support via yearly subscriptions.

Disclosure: Yeah, I work for the company who built this, so I'm biased. But I honestly believe in what I just wrote.

UIView's frame, bounds, center, origin, when to use what?

They are related values, and kept consistent by the property setter/getter methods (and using the fact that frame is a purely synthesized value, not backed by an actual instance variable).

The main equations are:

frame.origin = center - bounds.size / 2

(which is the same as)

center = frame.origin + bounds.size / 2

(and there’s also)

frame.size = bounds.size

That's not code, just equations to express the invariant between the three properties. These equations also assume your view's transform is the identity, which it is by default. If it's not, then bounds and center keep the same meaning, but frame can change. Unless you're doing non-right-angle rotations, the frame will always be the transformed view in terms of the superview's coordinates.

This stuff is all explained in more detail with a useful mini-library here:

Xcode stuck on Indexing

My case: it was not the project.xcworkspace file, it was not the Derived Data folder.

I've wasted a lot of time. Worse, no error message. No clue on the part of Xcode. Absolutely lost.

Finally this function (with more than 10 parameters) is responsible.

func animationFrames(level: Float,
                     image: String,
                     frame0: String,
                     frame1: String,
                     frame2: String,
                     frame3: String,
                     frame4: String,
                     frame5: String,
                     frame6: String,
                     frame7: String,
                     frame8: String,
                     frame9: String,
                     frame10: String) {

To go crazy! The truth is that it is worrisome (because there is no syntax error, or any type)

SQL Server FOR EACH Loop



-- variable for storing start date
Declare @StartYear as int
-- Variable for the End date 
Declare @EndYear as int 

-- Setting the value in strat Date
select @StartYear = Value from   rat.Configuration where Name = 'REPORT_START_YEAR'; 

-- Setting the End date 
select @EndYear = Value from   rat.Configuration where Name = 'REPORT_END_YEAR'; 

-- Creating Tem table 
    with [Years] as
        --Selecting the Year
        select @StartYear [Year] 
        --doing Union 
        union all
         -- doing the loop in Years table 
         select Year+1 Year from [Years] where Year < @EndYear
    --Selecting the Year table 

mysqli::query(): Couldn't fetch mysqli

I had the same problem. I changed the localhost parameter in the mysqli object to '' instead of writing 'localhost'. It worked; I’m not sure how or why.

$db_connection = new mysqli("","root","","db_name");

Hope it helps.

How to create an alert message in jsp page after submit process is complete

in your servlet

 return mapping.findForward("success");

In your jsp

<c:if test="${not empty submitDone}">
  <script>alert("Form submitted");

Xcode - iPhone - profile doesn't match any valid certificate-/private-key pair in the default keychain

I had a similar situation: multiple developers using the same private key, but I couldn't find mine anymore after upgrade to Lion. The very simple fix was to export the private key for the specific certificate (in my case the Development cert) from the other machine, move it to my computer and drag it into keychain access there. Xcode immediately picked it up and I was good to go.

How to invert a grep expression

Use command-line option -v or --invert-match,

ls -R |grep -v -E .*[\.exe]$\|.*[\.html]$

Configure nginx with multiple locations with different root folders on subdomain

The Location directive system is

Like you want to forward all request which start /static and your data present in /var/www/static

So a simple method is separated last folder from full path , that means

Full path : /var/www/static

Last Path : /static and First path : /var/www

location <lastPath> {
    root <FirstPath>;

So lets see what you did mistake and what is your solutions

Your Mistake :

location /static {
    root /web/;

Your Solutions :

location /static {
    root /web/;