Programs & Examples On #Hole punching

Hole punching is the process of taking advantage of the standard way of implementing NAT to allow direct connection between computers in private networks.

Using node.js as a simple web server

The simpler version which I've came across is as following. For education purposes, it is best, because it does not use any abstract libraries.

var http = require('http'),
url = require('url'),
path = require('path'),
fs = require('fs');

var mimeTypes = {
  "html": "text/html",
  "mp3":"audio/mpeg",
  "mp4":"video/mp4",
  "jpeg": "image/jpeg",
  "jpg": "image/jpeg",
  "png": "image/png",
  "js": "text/javascript",
  "css": "text/css"};

http.createServer(function(req, res) {
    var uri = url.parse(req.url).pathname;
    var filename = path.join(process.cwd(), uri);
    fs.exists(filename, function(exists) {
        if(!exists) {
            console.log("not exists: " + filename);
            res.writeHead(200, {'Content-Type': 'text/plain'});
            res.write('404 Not Found\n');
            res.end();
            return;
        }
        var mimeType = mimeTypes[path.extname(filename).split(".")[1]];
        res.writeHead(200, {'Content-Type':mimeType});

        var fileStream = fs.createReadStream(filename);
        fileStream.pipe(res);

    }); //end path.exists
}).listen(1337);

Now go to browser and open following:

http://127.0.0.1/image.jpg

Here image.jpg should be in same directory as this file. Hope this helps someone :)

Mongoose: Get full list of users

Same can be done with async await and arrow function

server.get('/usersList', async (req, res) => {

const users = await User.find({});

const userMap = {};
users.forEach((user) => {
    userMap[user._id] = user;
});

res.send(userMap);

});

What is for Python what 'explode' is for PHP?

The alternative for explode in php is split.

The first parameter is the delimiter, the second parameter the maximum number splits. The parts are returned without the delimiter present (except possibly the last part). When the delimiter is None, all whitespace is matched. This is the default.

>>> "Rajasekar SP".split()
['Rajasekar', 'SP']

>>> "Rajasekar SP".split('a',2)
['R','j','sekar SP']

Uploading both data and files in one form using Ajax?

The problem I had was using the wrong jQuery identifier.

You can upload data and files with one form using ajax.

PHP + HTML

<?php

print_r($_POST);
print_r($_FILES);
?>

<form id="data" method="post" enctype="multipart/form-data">
    <input type="text" name="first" value="Bob" />
    <input type="text" name="middle" value="James" />
    <input type="text" name="last" value="Smith" />
    <input name="image" type="file" />
    <button>Submit</button>
</form>

jQuery + Ajax

$("form#data").submit(function(e) {
    e.preventDefault();    
    var formData = new FormData(this);

    $.ajax({
        url: window.location.pathname,
        type: 'POST',
        data: formData,
        success: function (data) {
            alert(data)
        },
        cache: false,
        contentType: false,
        processData: false
    });
});

Short Version

$("form#data").submit(function(e) {
    e.preventDefault();
    var formData = new FormData(this);    

    $.post($(this).attr("action"), formData, function(data) {
        alert(data);
    });
});

How to automatically generate a stacktrace when my program crashes

Linux

While the use of the backtrace() functions in execinfo.h to print a stacktrace and exit gracefully when you get a segmentation fault has already been suggested, I see no mention of the intricacies necessary to ensure the resulting backtrace points to the actual location of the fault (at least for some architectures - x86 & ARM).

The first two entries in the stack frame chain when you get into the signal handler contain a return address inside the signal handler and one inside sigaction() in libc. The stack frame of the last function called before the signal (which is the location of the fault) is lost.

Code

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#ifndef __USE_GNU
#define __USE_GNU
#endif

#include <execinfo.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ucontext.h>
#include <unistd.h>

/* This structure mirrors the one found in /usr/include/asm/ucontext.h */
typedef struct _sig_ucontext {
 unsigned long     uc_flags;
 ucontext_t        *uc_link;
 stack_t           uc_stack;
 sigcontext_t      uc_mcontext;
 sigset_t          uc_sigmask;
} sig_ucontext_t;

void crit_err_hdlr(int sig_num, siginfo_t * info, void * ucontext)
{
 void *             array[50];
 void *             caller_address;
 char **            messages;
 int                size, i;
 sig_ucontext_t *   uc;

 uc = (sig_ucontext_t *)ucontext;

 /* Get the address at the time the signal was raised */
#if defined(__i386__) // gcc specific
 caller_address = (void *) uc->uc_mcontext.eip; // EIP: x86 specific
#elif defined(__x86_64__) // gcc specific
 caller_address = (void *) uc->uc_mcontext.rip; // RIP: x86_64 specific
#else
#error Unsupported architecture. // TODO: Add support for other arch.
#endif

 fprintf(stderr, "signal %d (%s), address is %p from %p\n", 
  sig_num, strsignal(sig_num), info->si_addr, 
  (void *)caller_address);

 size = backtrace(array, 50);

 /* overwrite sigaction with caller's address */
 array[1] = caller_address;

 messages = backtrace_symbols(array, size);

 /* skip first stack frame (points here) */
 for (i = 1; i < size && messages != NULL; ++i)
 {
  fprintf(stderr, "[bt]: (%d) %s\n", i, messages[i]);
 }

 free(messages);

 exit(EXIT_FAILURE);
}

int crash()
{
 char * p = NULL;
 *p = 0;
 return 0;
}

int foo4()
{
 crash();
 return 0;
}

int foo3()
{
 foo4();
 return 0;
}

int foo2()
{
 foo3();
 return 0;
}

int foo1()
{
 foo2();
 return 0;
}

int main(int argc, char ** argv)
{
 struct sigaction sigact;

 sigact.sa_sigaction = crit_err_hdlr;
 sigact.sa_flags = SA_RESTART | SA_SIGINFO;

 if (sigaction(SIGSEGV, &sigact, (struct sigaction *)NULL) != 0)
 {
  fprintf(stderr, "error setting signal handler for %d (%s)\n",
    SIGSEGV, strsignal(SIGSEGV));

  exit(EXIT_FAILURE);
 }

 foo1();

 exit(EXIT_SUCCESS);
}

Output

signal 11 (Segmentation fault), address is (nil) from 0x8c50
[bt]: (1) ./test(crash+0x24) [0x8c50]
[bt]: (2) ./test(foo4+0x10) [0x8c70]
[bt]: (3) ./test(foo3+0x10) [0x8c8c]
[bt]: (4) ./test(foo2+0x10) [0x8ca8]
[bt]: (5) ./test(foo1+0x10) [0x8cc4]
[bt]: (6) ./test(main+0x74) [0x8d44]
[bt]: (7) /lib/libc.so.6(__libc_start_main+0xa8) [0x40032e44]

All the hazards of calling the backtrace() functions in a signal handler still exist and should not be overlooked, but I find the functionality I described here quite helpful in debugging crashes.

It is important to note that the example I provided is developed/tested on Linux for x86. I have also successfully implemented this on ARM using uc_mcontext.arm_pc instead of uc_mcontext.eip.

Here's a link to the article where I learned the details for this implementation: http://www.linuxjournal.com/article/6391

SQL Server copy all rows from one table into another i.e duplicate table

Duplicate your table into a table to be archived:

SELECT * INTO ArchiveTable FROM MyTable

Delete all entries in your table:

DELETE * FROM MyTable

List<T> or IList<T>

A principle of TDD and OOP generally is programming to an interface not an implementation.

In this specific case since you're essentially talking about a language construct, not a custom one it generally won't matter, but say for example that you found List didn't support something you needed. If you had used IList in the rest of the app you could extend List with your own custom class and still be able to pass that around without refactoring.

The cost to do this is minimal, why not save yourself the headache later? It's what the interface principle is all about.

Error in data frame undefined columns selected

Are you meaning?

data2 <- data1[good,]

With

data1[good]

you're selecting columns in a wrong way (using a logical vector of complete rows).

Consider that parameter pollutant is not used; is it a column name that you want to extract? if so it should be something like

data2 <- data1[good, pollutant]

Furthermore consider that you have to rbind the data.frames inside the for loop, otherwise you get only the last data.frame (its completed.cases)

And last but not least, i'd prefer generating filenames eg with

id <- 1:322
paste0( directory, "/", gsub(" ", "0", sprintf("%3d",id)), ".csv")

A little modified chunk of ?sprintf

The string fmt (in our case "%3d") contains normal characters, which are passed through to the output string, and also conversion specifications which operate on the arguments provided through .... The allowed conversion specifications start with a % and end with one of the letters in the set aAdifeEgGosxX%. These letters denote the following types:

  • d: integer

Eg a more general example

    sprintf("I am %10d years old", 25)
[1] "I am         25 years old"
          ^^^^^^^^^^
          |        |
          1       10

How to customize the back button on ActionBar

tray this:

getSupportActionBar().setHomeAsUpIndicator(R.drawable.ic_close);

inside onCreate();

Why does an onclick property set with setAttribute fail to work in IE?

Have you considered an event listener rather than setting the attribute? Among other things, it lets you pass parameters, which was a problem I ran into when trying to do this. You still have to do it twice for IE and Mozilla:

function makeEvent(element, callback, param, event) {
    function local() {
        return callback(param);
    }

    if (element.addEventListener) {
        //Mozilla
        element.addEventListener(event,local,false);
    } else if (element.attachEvent) {
        //IE
        element.attachEvent("on"+event,local);
    }
}

makeEvent(execBtn, alert, "hey buddy, what's up?", "click");

Just let event be a name like "click" or "mouseover".

Bash script processing limited number of commands in parallel

You can run 20 processes and use the command:

wait

Your script will wait and continue when all your background jobs are finished.

The Android emulator is not starting, showing "invalid command-line parameter"

I started Task Manager, made sure adb.exe is closed (it locks some files)

Create the folder C:\Android Moved folder + all files from C:\Program Files\android-sdk to C:\Android

Edited C:\Documents and Settings\All Users\Start Menu\Programs\Android SDK Tools shortcuts.

I considered uninstalling the SDK and re-installing, but for the life of me, where does it store the temp files?? I don't want to re-download the platforms, samples and doco that I have added to the SDK.

Difference between agile and iterative and incremental development

Agile is mostly used technique in project development.In agile technology peoples are switches from one technology to other ..Main purpose is to remove dependancy. Like Peoples shifted from production to development,and development to testing. Thats why dependancy will remove on a single team or person..

How to check the extension of a filename in a bash script?

Make

if [ "$file" == "*.txt" ]

like this:

if [[ $file == *.txt ]]

That is, double brackets and no quotes.

The right side of == is a shell pattern. If you need a regular expression, use =~ then.

IOCTL Linux device driver

The ioctl function is useful for implementing a device driver to set the configuration on the device. e.g. a printer that has configuration options to check and set the font family, font size etc. ioctl could be used to get the current font as well as set the font to a new one. A user application uses ioctl to send a code to a printer telling it to return the current font or to set the font to a new one.

int ioctl(int fd, int request, ...)
  1. fd is file descriptor, the one returned by open;
  2. request is request code. e.g GETFONT will get the current font from the printer, SETFONT will set the font on the printer;
  3. the third argument is void *. Depending on the second argument, the third may or may not be present, e.g. if the second argument is SETFONT, the third argument can be the font name such as "Arial";

int request is not just a macro. A user application is required to generate a request code and the device driver module to determine which configuration on device must be played with. The application sends the request code using ioctl and then uses the request code in the device driver module to determine which action to perform.

A request code has 4 main parts

    1. A Magic number - 8 bits
    2. A sequence number - 8 bits
    3. Argument type (typically 14 bits), if any.
    4. Direction of data transfer (2 bits).  

If the request code is SETFONT to set font on a printer, the direction for data transfer will be from user application to device driver module (The user application sends the font name "Arial" to the printer). If the request code is GETFONT, direction is from printer to the user application.

In order to generate a request code, Linux provides some predefined function-like macros.

1._IO(MAGIC, SEQ_NO) both are 8 bits, 0 to 255, e.g. let us say we want to pause printer. This does not require a data transfer. So we would generate the request code as below

#define PRIN_MAGIC 'P'
#define NUM 0
#define PAUSE_PRIN __IO(PRIN_MAGIC, NUM) 

and now use ioctl as

ret_val = ioctl(fd, PAUSE_PRIN);

The corresponding system call in the driver module will receive the code and pause the printer.

  1. __IOW(MAGIC, SEQ_NO, TYPE) MAGIC and SEQ_NO are the same as above, and TYPE gives the type of the next argument, recall the third argument of ioctl is void *. W in __IOW indicates that the data flow is from user application to driver module. As an example, suppose we want to set the printer font to "Arial".
#define PRIN_MAGIC 'S'
#define SEQ_NO 1
#define SETFONT __IOW(PRIN_MAGIC, SEQ_NO, unsigned long)

further,

char *font = "Arial";
ret_val = ioctl(fd, SETFONT, font); 

Now font is a pointer, which means it is an address best represented as unsigned long, hence the third part of _IOW mentions type as such. Also, this address of font is passed to corresponding system call implemented in device driver module as unsigned long and we need to cast it to proper type before using it. Kernel space can access user space and hence this works. other two function-like macros are __IOR(MAGIC, SEQ_NO, TYPE) and __IORW(MAGIC, SEQ_NO, TYPE) where the data flow will be from kernel space to user space and both ways respectively.

Please let me know if this helps!

Powershell Invoke-WebRequest Fails with SSL/TLS Secure Channel

It works for me...

if (-not ([System.Management.Automation.PSTypeName]'ServerCertificateValidationCallback').Type)
    {
    $certCallback = @"
        using System;
        using System.Net;
        using System.Net.Security;
        using System.Security.Cryptography.X509Certificates;
        public class ServerCertificateValidationCallback
        {
            public static void Ignore()
            {
                if(ServicePointManager.ServerCertificateValidationCallback ==null)
                {
                    ServicePointManager.ServerCertificateValidationCallback += 
                        delegate
                        (
                            Object obj, 
                            X509Certificate certificate, 
                            X509Chain chain, 
                            SslPolicyErrors errors
                        )
                        {
                            return true;
                        };
                }
            }
        }
    "@
        Add-Type $certCallback
     }
    [ServerCertificateValidationCallback]::Ignore()

Invoke-WebRequest -Uri https://apod.nasa.gov/apod/

Bash Templating: How to build configuration files from templates with Bash?

Here's a bash function that preserves whitespace:

# Render a file in bash, i.e. expand environment variables. Preserves whitespace.
function render_file () {
    while IFS='' read line; do
        eval echo \""${line}"\"
    done < "${1}"
}

Printing object properties in Powershell

Try this:

Write-Host ($obj | Format-Table | Out-String)

or

Write-Host ($obj | Format-List | Out-String)

How to implement custom JsonConverter in JSON.NET to deserialize a List of base class objects?

This is an expansion to totem's answer. It does basically the same thing but the property matching is based on the serialized json object, not reflect the .net object. This is important if you're using [JsonProperty], using the CamelCasePropertyNamesContractResolver, or doing anything else that will cause the json to not match the .net object.

Usage is simple:

[KnownType(typeof(B))]
public class A
{
   public string Name { get; set; }
}

public class B : A
{
   public string LastName { get; set; }
}

Converter code:

/// <summary>
/// Use KnownType Attribute to match a divierd class based on the class given to the serilaizer
/// Selected class will be the first class to match all properties in the json object.
/// </summary>
public class KnownTypeConverter : JsonConverter {
    public override bool CanConvert( Type objectType ) {
        return System.Attribute.GetCustomAttributes( objectType ).Any( v => v is KnownTypeAttribute );
    }

    public override bool CanWrite {
        get { return false; }
    }

    public override object ReadJson( JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer ) {
        // Load JObject from stream
        JObject jObject = JObject.Load( reader );

        // Create target object based on JObject
        System.Attribute[ ] attrs = System.Attribute.GetCustomAttributes( objectType );  // Reflection. 

        // check known types for a match. 
        foreach( var attr in attrs.OfType<KnownTypeAttribute>( ) ) {
            object target = Activator.CreateInstance( attr.Type );

            JObject jTest;
            using( var writer = new StringWriter( ) ) {
                using( var jsonWriter = new JsonTextWriter( writer ) ) {
                    serializer.Serialize( jsonWriter, target );
                    string json = writer.ToString( );
                    jTest = JObject.Parse( json );
                }
            }

            var jO = this.GetKeys( jObject ).Select( k => k.Key ).ToList( );
            var jT = this.GetKeys( jTest ).Select( k => k.Key ).ToList( );

            if( jO.Count == jT.Count && jO.Intersect( jT ).Count( ) == jO.Count ) {
                serializer.Populate( jObject.CreateReader( ), target );
                return target;
            }
        }

        throw new SerializationException( string.Format( "Could not convert base class {0}", objectType ) );
    }

    public override void WriteJson( JsonWriter writer, object value, JsonSerializer serializer ) {
        throw new NotImplementedException( );
    }

    private IEnumerable<KeyValuePair<string, JToken>> GetKeys( JObject obj ) {
        var list = new List<KeyValuePair<string, JToken>>( );
        foreach( var t in obj ) {
            list.Add( t );
        }
        return list;
    }
}

Notice: Undefined variable: _SESSION in "" on line 9

Add

session_start();

at the beginning of your page before any HTML

You will have something like :

<?php session_start();
include("inc/incfiles/header.inc.php")?>
<html>
<head>
<meta http-equiv="Content-Type" conte...

Don't forget to remove the space you have before

Count lines in large files

I know the question is a few years old now, but expanding on Ivella's last idea, this bash script estimates the line count of a big file within seconds or less by measuring the size of one line and extrapolating from it:

#!/bin/bash
head -2 $1 | tail -1 > $1_oneline
filesize=$(du -b $1 | cut -f -1)
linesize=$(du -b $1_oneline | cut -f -1)
rm $1_oneline
echo $(expr $filesize / $linesize)

If you name this script lines.sh, you can call lines.sh bigfile.txt to get the estimated number of lines. In my case (about 6 GB, export from database), the deviation from the true line count was only 3%, but ran about 1000 times faster. By the way, I used the second, not first, line as the basis, because the first line had column names and the actual data started in the second line.

How to build an android library with Android Studio and gradle?

Gradle Build Tools 2.2.0+ - Everything just works

This is the correct way to do it

In trying to avoid experimental and frankly fed up with the NDK and all its hackery I am happy that 2.2.x of the Gradle Build Tools came out and now it just works. The key is the externalNativeBuild and pointing ndkBuild path argument at an Android.mk or change ndkBuild to cmake and point the path argument at a CMakeLists.txt build script.

android {
    compileSdkVersion 19
    buildToolsVersion "25.0.2"

    defaultConfig {
        minSdkVersion 19
        targetSdkVersion 19

        ndk {
            abiFilters 'armeabi', 'armeabi-v7a', 'x86'
        }

        externalNativeBuild {
            cmake {
                cppFlags '-std=c++11'
                arguments '-DANDROID_TOOLCHAIN=clang',
                        '-DANDROID_PLATFORM=android-19',
                        '-DANDROID_STL=gnustl_static',
                        '-DANDROID_ARM_NEON=TRUE',
                        '-DANDROID_CPP_FEATURES=exceptions rtti'
            }
        }
    }

    externalNativeBuild {
        cmake {
             path 'src/main/jni/CMakeLists.txt'
        }
        //ndkBuild {
        //   path 'src/main/jni/Android.mk'
        //}
    }
}

For much more detail check Google's page on adding native code.

After this is setup correctly you can ./gradlew installDebug and off you go. You will also need to be aware that the NDK is moving to clang since gcc is now deprecated in the Android NDK.

Boolean operators ( &&, -a, ||, -o ) in Bash

-a and -o are the older and/or operators for the test command. && and || are and/or operators for the shell. So (assuming an old shell) in your first case,

[ "$1" = 'yes' ] && [ -r $2.txt ]

The shell is evaluating the and condition. In your second case,

[ "$1" = 'yes' -a $2 -lt 3 ]

The test command (or builtin test) is evaluating the and condition.

Of course in all modern or semi-modern shells, the test command is built in to the shell, so there really isn't any or much difference. In modern shells, the if statement can be written:

[[ $1 == yes && -r $2.txt ]]

Which is more similar to modern programming languages and thus is more readable.

How to convert a string to an integer in JavaScript?

The safest way to ensure you get a valid integer:

let integer = (parseInt(value, 10) || 0);

Examples:

// Example 1 - Invalid value:
let value = null;
let integer = (parseInt(value, 10) || 0);
// => integer = 0
// Example 2 - Valid value:
let value = "1230.42";
let integer = (parseInt(value, 10) || 0);
// => integer = 1230
// Example 3 - Invalid value:
let value = () => { return 412 };
let integer = (parseInt(value, 10) || 0);
// => integer = 0

Generate pdf from HTML in div using Javascript

This is the simple solution. This works for me.You can use the javascript print concept and simple save this as pdf.

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script type="text/javascript">
        $("#btnPrint").live("click", function () {
            var divContents = $("#dvContainer").html();
            var printWindow = window.open('', '', 'height=400,width=800');
            printWindow.document.write('<html><head><title>DIV Contents</title>');
            printWindow.document.write('</head><body >');
            printWindow.document.write(divContents);
            printWindow.document.write('</body></html>');
            printWindow.document.close();
            printWindow.print();
        });
    </script>
</head>
<body>
    <form id="form1">
    <div id="dvContainer">
        This content needs to be printed.
    </div>
    <input type="button" value="Print Div Contents" id="btnPrint" />
    </form>
</body>
</html>

Updating a local repository with changes from a GitHub repository

With an already-set origin master, you just have to use the below command -

git pull "https://github.com/yourUserName/yourRepo.git"

SQL Server : export query as a .txt file

This is quite simple to do and the answer is available in other queries. For those of you who are viewing this:

select entries from my_entries where id='42' INTO OUTFILE 'bishwas.txt';

Using HTML5/Canvas/JavaScript to take in-browser screenshots

Get screenshot as Canvas or Jpeg Blob / ArrayBuffer using getDisplayMedia API:

FIX 1: Use the getUserMedia with chromeMediaSource only for Electron.js
FIX 2: Throw error instead return null object
FIX 3: Fix demo to prevent the error: getDisplayMedia must be called from a user gesture handler

// docs: https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getDisplayMedia
// see: https://www.webrtc-experiment.com/Pluginfree-Screen-Sharing/#20893521368186473
// see: https://github.com/muaz-khan/WebRTC-Experiment/blob/master/Pluginfree-Screen-Sharing/conference.js

function getDisplayMedia(options) {
    if (navigator.mediaDevices && navigator.mediaDevices.getDisplayMedia) {
        return navigator.mediaDevices.getDisplayMedia(options)
    }
    if (navigator.getDisplayMedia) {
        return navigator.getDisplayMedia(options)
    }
    if (navigator.webkitGetDisplayMedia) {
        return navigator.webkitGetDisplayMedia(options)
    }
    if (navigator.mozGetDisplayMedia) {
        return navigator.mozGetDisplayMedia(options)
    }
    throw new Error('getDisplayMedia is not defined')
}

function getUserMedia(options) {
    if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
        return navigator.mediaDevices.getUserMedia(options)
    }
    if (navigator.getUserMedia) {
        return navigator.getUserMedia(options)
    }
    if (navigator.webkitGetUserMedia) {
        return navigator.webkitGetUserMedia(options)
    }
    if (navigator.mozGetUserMedia) {
        return navigator.mozGetUserMedia(options)
    }
    throw new Error('getUserMedia is not defined')
}

async function takeScreenshotStream() {
    // see: https://developer.mozilla.org/en-US/docs/Web/API/Window/screen
    const width = screen.width * (window.devicePixelRatio || 1)
    const height = screen.height * (window.devicePixelRatio || 1)

    const errors = []
    let stream
    try {
        stream = await getDisplayMedia({
            audio: false,
            // see: https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamConstraints/video
            video: {
                width,
                height,
                frameRate: 1,
            },
        })
    } catch (ex) {
        errors.push(ex)
    }

    // for electron js
    if (navigator.userAgent.indexOf('Electron') >= 0) {
        try {
            stream = await getUserMedia({
                audio: false,
                video: {
                    mandatory: {
                        chromeMediaSource: 'desktop',
                        // chromeMediaSourceId: source.id,
                        minWidth         : width,
                        maxWidth         : width,
                        minHeight        : height,
                        maxHeight        : height,
                    },
                },
            })
        } catch (ex) {
            errors.push(ex)
        }
    }

    if (errors.length) {
        console.debug(...errors)
        if (!stream) {
            throw errors[errors.length - 1]
        }
    }

    return stream
}

async function takeScreenshotCanvas() {
    const stream = await takeScreenshotStream()

    // from: https://stackoverflow.com/a/57665309/5221762
    const video = document.createElement('video')
    const result = await new Promise((resolve, reject) => {
        video.onloadedmetadata = () => {
            video.play()
            video.pause()

            // from: https://github.com/kasprownik/electron-screencapture/blob/master/index.js
            const canvas = document.createElement('canvas')
            canvas.width = video.videoWidth
            canvas.height = video.videoHeight
            const context = canvas.getContext('2d')
            // see: https://developer.mozilla.org/en-US/docs/Web/API/HTMLVideoElement
            context.drawImage(video, 0, 0, video.videoWidth, video.videoHeight)
            resolve(canvas)
        }
        video.srcObject = stream
    })

    stream.getTracks().forEach(function (track) {
        track.stop()
    })
    
    if (result == null) {
        throw new Error('Cannot take canvas screenshot')
    }

    return result
}

// from: https://stackoverflow.com/a/46182044/5221762
function getJpegBlob(canvas) {
    return new Promise((resolve, reject) => {
        // docs: https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toBlob
        canvas.toBlob(blob => resolve(blob), 'image/jpeg', 0.95)
    })
}

async function getJpegBytes(canvas) {
    const blob = await getJpegBlob(canvas)
    return new Promise((resolve, reject) => {
        const fileReader = new FileReader()

        fileReader.addEventListener('loadend', function () {
            if (this.error) {
                reject(this.error)
                return
            }
            resolve(this.result)
        })

        fileReader.readAsArrayBuffer(blob)
    })
}

async function takeScreenshotJpegBlob() {
    const canvas = await takeScreenshotCanvas()
    return getJpegBlob(canvas)
}

async function takeScreenshotJpegBytes() {
    const canvas = await takeScreenshotCanvas()
    return getJpegBytes(canvas)
}

function blobToCanvas(blob, maxWidth, maxHeight) {
    return new Promise((resolve, reject) => {
        const img = new Image()
        img.onload = function () {
            const canvas = document.createElement('canvas')
            const scale = Math.min(
                1,
                maxWidth ? maxWidth / img.width : 1,
                maxHeight ? maxHeight / img.height : 1,
            )
            canvas.width = img.width * scale
            canvas.height = img.height * scale
            const ctx = canvas.getContext('2d')
            ctx.drawImage(img, 0, 0, img.width, img.height, 0, 0, canvas.width, canvas.height)
            resolve(canvas)
        }
        img.onerror = () => {
            reject(new Error('Error load blob to Image'))
        }
        img.src = URL.createObjectURL(blob)
    })
}

DEMO:

document.body.onclick = async () => {
    // take the screenshot
    var screenshotJpegBlob = await takeScreenshotJpegBlob()

    // show preview with max size 300 x 300 px
    var previewCanvas = await blobToCanvas(screenshotJpegBlob, 300, 300)
    previewCanvas.style.position = 'fixed'
    document.body.appendChild(previewCanvas)

    // send it to the server
    var formdata = new FormData()
    formdata.append("screenshot", screenshotJpegBlob)
    await fetch('https://your-web-site.com/', {
        method: 'POST',
        body: formdata,
        'Content-Type' : "multipart/form-data",
    })
}

// and click on the page

What is the best way to determine a session variable is null or empty in C#?

To follow on from what others have said. I tend to have two layers:

The core layer. This is within a DLL that is added to nearly all web app projects. In this I have a SessionVars class which does the grunt work for Session state getters/setters. It contains code like the following:

public class SessionVar
{
    static HttpSessionState Session
    {
        get
        {
            if (HttpContext.Current == null)
                throw new ApplicationException("No Http Context, No Session to Get!");

            return HttpContext.Current.Session;
        }
    }

    public static T Get<T>(string key)
    {
        if (Session[key] == null)
            return default(T);
        else
            return (T)Session[key];
    }

    public static void Set<T>(string key, T value)
    {
        Session[key] = value;
    }
}

Note the generics for getting any type.

I then also add Getters/Setters for specific types, especially string since I often prefer to work with string.Empty rather than null for variables presented to Users.

e.g:

public static string GetString(string key)
{
    string s = Get<string>(key);
    return s == null ? string.Empty : s;
}

public static void SetString(string key, string value)
{
    Set<string>(key, value);
}

And so on...

I then create wrappers to abstract that away and bring it up to the application model. For example, if we have customer details:

public class CustomerInfo
{
    public string Name
    {
        get
        {
            return SessionVar.GetString("CustomerInfo_Name");
        }
        set
        {
            SessionVar.SetString("CustomerInfo_Name", value);
        }
    }
}

You get the idea right? :)

NOTE: Just had a thought when adding a comment to the accepted answer. Always ensure objects are serializable when storing them in Session when using a state server. It can be all too easy to try and save an object using the generics when on web farm and it go boom. I deploy on a web farm at work so added checks to my code in the core layer to see if the object is serializable, another benefit of encapsulating the Session Getters and Setters :)

How can I get a specific number child using CSS?

For modern browsers, use td:nth-child(2) for the second td, and td:nth-child(3) for the third. Remember that these retrieve the second and third td for every row.

If you need compatibility with IE older than version 9, use sibling combinators or JavaScript as suggested by Tim. Also see my answer to this related question for an explanation and illustration of his method.

Passing multiple variables in @RequestBody to a Spring MVC controller using Ajax

request parameter exist for both GET and POST ,For Get it will get appended as query string to URL but for POST it is within Request Body

How to highlight cell if value duplicate in same column for google spreadsheet?

From the "Text Contains" dropdown menu select "Custom formula is:", and write: "=countif(A:A, A1) > 1" (without the quotes)

I did exactly as zolley proposed, but there should be done small correction: use "Custom formula is" instead of "Text Contains". And then conditional rendering will work.

Screenshot from menu

Java Inheritance - calling superclass method

Whenever you create child class object then that object has all the features of parent class. Here Super() is the facilty for accession parent.

If you write super() at that time parents's default constructor is called. same if you write super.

this keyword refers the current object same as super key word facilty for accessing parents.

Apply multiple functions to multiple groupby columns

For the first part you can pass a dict of column names for keys and a list of functions for the values:

In [28]: df
Out[28]:
          A         B         C         D         E  GRP
0  0.395670  0.219560  0.600644  0.613445  0.242893    0
1  0.323911  0.464584  0.107215  0.204072  0.927325    0
2  0.321358  0.076037  0.166946  0.439661  0.914612    1
3  0.133466  0.447946  0.014815  0.130781  0.268290    1

In [26]: f = {'A':['sum','mean'], 'B':['prod']}

In [27]: df.groupby('GRP').agg(f)
Out[27]:
            A                   B
          sum      mean      prod
GRP
0    0.719580  0.359790  0.102004
1    0.454824  0.227412  0.034060

UPDATE 1:

Because the aggregate function works on Series, references to the other column names are lost. To get around this, you can reference the full dataframe and index it using the group indices within the lambda function.

Here's a hacky workaround:

In [67]: f = {'A':['sum','mean'], 'B':['prod'], 'D': lambda g: df.loc[g.index].E.sum()}

In [69]: df.groupby('GRP').agg(f)
Out[69]:
            A                   B         D
          sum      mean      prod  <lambda>
GRP
0    0.719580  0.359790  0.102004  1.170219
1    0.454824  0.227412  0.034060  1.182901

Here, the resultant 'D' column is made up of the summed 'E' values.

UPDATE 2:

Here's a method that I think will do everything you ask. First make a custom lambda function. Below, g references the group. When aggregating, g will be a Series. Passing g.index to df.ix[] selects the current group from df. I then test if column C is less than 0.5. The returned boolean series is passed to g[] which selects only those rows meeting the criteria.

In [95]: cust = lambda g: g[df.loc[g.index]['C'] < 0.5].sum()

In [96]: f = {'A':['sum','mean'], 'B':['prod'], 'D': {'my name': cust}}

In [97]: df.groupby('GRP').agg(f)
Out[97]:
            A                   B         D
          sum      mean      prod   my name
GRP
0    0.719580  0.359790  0.102004  0.204072
1    0.454824  0.227412  0.034060  0.570441

CodeIgniter PHP Model Access "Unable to locate the model you have specified"

Change your model file name, start with upper case letter like this: Logon_model.php

This happens when we migrate our project from windows server to LINUX server because linux is case sensitive while windows is not.

So, on windows even if don't write file name with upper case then also it will work fine but not on linux.

Why is my JavaScript function sometimes "not defined"?

A syntax error in the function -- or in the code above it -- may cause it to be undefined.

How to enable local network users to access my WAMP sites?

Put your wamp server onlineenter image description here

and then go to control panel > system and security > windows firewall and turn windows firewall off

now you can access your wamp server from another computer over local network by the network IP of computer which have wamp server installed like http://192.168.2.34/mysite

NSAttributedString add text alignment

Swift 4 answer:

// Define paragraph style - you got to pass it along to NSAttributedString constructor
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = .center

// Define attributed string attributes
let attributes = [NSAttributedStringKey.paragraphStyle: paragraphStyle]

let attributedString = NSAttributedString(string:"Test", attributes: attributes)

Force DOM redraw/refresh on Chrome/Mac

CSS only. This works for situations where a child element is removed or added. In these situations, borders and rounded corners can leave artifacts.

el:after { content: " "; }
el:before { content: " "; }

How can I find script's directory?

You need to call os.path.realpath on __file__, so that when __file__ is a filename without the path you still get the dir path:

import os
print(os.path.dirname(os.path.realpath(__file__)))

ASP.NET MVC How to pass JSON object from View to Controller as Parameter

This answer is a follow up to DaRKoN_'s answer that utilized the object filter:

[ObjectFilter(Param = "postdata", RootType = typeof(ObjectToSerializeTo))]
    public JsonResult ControllerMethod(ObjectToSerializeTo postdata) { ... }

I was having a problem figuring out how to send multiple parameters to an action method and have one of them be the json object and the other be a plain string. I'm new to MVC and I had just forgotten that I already solved this problem with non-ajaxed views.

What I would do if I needed, say, two different objects on a view. I would create a ViewModel class. So say I needed the person object and the address object, I would do the following:

public class SomeViewModel()
{
     public Person Person { get; set; }
     public Address Address { get; set; }
}

Then I would bind the view to SomeViewModel. You can do the same thing with JSON.

[ObjectFilter(Param = "jsonViewModel", RootType = typeof(JsonViewModel))] // Don't forget to add the object filter class in DaRKoN_'s answer.
public JsonResult doJsonStuff(JsonViewModel jsonViewModel)
{
     Person p = jsonViewModel.Person;
     Address a = jsonViewModel.Address;
     // Do stuff
     jsonViewModel.Person = p;
     jsonViewModel.Address = a;
     return Json(jsonViewModel);
}

Then in the view you can use a simple call with JQuery like this:

var json = { 
    Person: { Name: "John Doe", Sex: "Male", Age: 23 }, 
    Address: { Street: "123 fk st.", City: "Redmond", State: "Washington" }
};

$.ajax({
     url: 'home/doJsonStuff',
     type: 'POST',
     contentType: 'application/json',
     dataType: 'json',
     data: JSON.stringify(json), //You'll need to reference json2.js
     success: function (response)
     {
          var person = response.Person;
          var address = response.Address;
     }
});

Is there a way to reset IIS 7.5 to factory settings?

This link has some useful suggestions: http://forums.iis.net/t/1085990.aspx

It depends on where you have the config settings stored. By default IIS7 will have all of it's configuration settings stored in a file called "ApplicationHost.Config". If you have delegation configured then you will see site/app related config settings getting written to web.config file for the site/app. With IIS7 on vista there is an automatica backup file for master configuration is created. This file is called "application.config.backup" and it resides inside "C:\Windows\System32\inetsrv\config" You could rename this file to applicationHost.config and replace it with the applicationHost.config inside the config folder. IIS7 on server release will have better configuration back up story, but for now I recommend using APPCMD to backup/restore your configuration on regualr basis. Example: APPCMD ADD BACK "MYBACKUP" Another option (really the last option) is to uninstall/reinstall IIS along with WPAS (Windows Process activation service).

How to get content body from a httpclient call?

The way you are using await/async is poor at best, and it makes it hard to follow. You are mixing await with Task'1.Result, which is just confusing. However, it looks like you are looking at a final task result, rather than the contents.

I've rewritten your function and function call, which should fix your issue:

async Task<string> GetResponseString(string text)
{
    var httpClient = new HttpClient();

    var parameters = new Dictionary<string, string>();
    parameters["text"] = text;

    var response = await httpClient.PostAsync(BaseUri, new FormUrlEncodedContent(parameters));
    var contents = await response.Content.ReadAsStringAsync();

    return contents;
}

And your final function call:

Task<string> result = GetResponseString(text);
var finalResult = result.Result;

Or even better:

var finalResult = await GetResponseString(text);

How to annotate MYSQL autoincrement field with JPA annotations

can you check whether you connected to the correct database. as i was faced same issue, but finally i found that i connected to different database.

identity supports identity columns in DB2, MySQL, MS SQL Server, Sybase and HypersonicSQL. The returned identifier is of type long, short or int.

More Info : http://docs.jboss.org/hibernate/orm/3.5/reference/en/html/mapping.html#mapping-declaration-id

append multiple values for one key in a dictionary

Here is an alternative way of doing this using the not in operator:

# define an empty dict
years_dict = dict()

for line in list:
    # here define what key is, for example,
    key = line[0]
    # check if key is already present in dict
    if key not in years_dict:
        years_dict[key] = []
    # append some value 
    years_dict[key].append(some.value)

JAX-WS - Adding SOAP Headers

Also, if you're using Maven to build your project, you'll need to add the following dependency:

    <dependency>
        <groupId>com.sun.xml.ws</groupId>
        <artifactId>jaxws-rt</artifactId>
        <version>{currentversion}/version>
    </dependency>

This provides you with the class com.sun.xml.ws.developer.WSBindingProvider.

Link: https://mvnrepository.com/artifact/com.sun.xml.ws/jaxws-rt

In Java, how to append a string more efficiently?

You can use StringBuffer or StringBuilder for this. Both are for dynamic string manipulation. StringBuffer is thread-safe where as StringBuilder is not.

Use StringBuffer in a multi-thread environment. But if it is single threaded StringBuilder is recommended and it is much faster than StringBuffer.

Disable a Button

in order for this to work:

yourButton.isEnabled = false

you need to create an outlet in addition to your UI button.

PHP Multidimensional Array Searching (Find key by specific value)

Try this

function recursive_array_search($needle,$haystack) {
        foreach($haystack as $key=>$value) {
            $current_key=$key;
            if($needle==$value['uid'] OR (is_array($value) && recursive_array_search($needle,$value) !== false)) {
                return $current_key;
            }
        }
        return false;
    }

Print PHP Call Stack

phptrace is a great tool to print PHP stack anytime when you want without installing any extensions.

There are two major function of phptrace: first, print call stack of PHP which need not install anything, second, trace php execution flows which needs to install the extension it supplies.

as follows:

$ ./phptrace -p 3130 -s             # phptrace -p <PID> -s
phptrace 0.2.0 release candidate, published by infra webcore team
process id = 3130
script_filename = /home/xxx/opt/nginx/webapp/block.php
[0x7f27b9a99dc8]  sleep /home/xxx/opt/nginx/webapp/block.php:6
[0x7f27b9a99d08]  say /home/xxx/opt/nginx/webapp/block.php:3
[0x7f27b9a99c50]  run /home/xxx/opt/nginx/webapp/block.php:10 

facebook Uncaught OAuthException: An active access token must be used to query information about the current user

Had the same problem and the solution was to reauthorize the user. Check it here:

<?php

 require_once("src/facebook.php");

  $config = array(
      'appId' => '1424980371051918',
      'secret' => '2ed5c1260daa4c44673ba6fbc348c67d',
      'fileUpload' => false // optional
  );

  $facebook = new Facebook($config);

//Authorizing app:

?>
<a href="<?php echo $facebook->getLoginUrl(); ?>">Login con fb</a>

Saved project and opened on my test enviroment and it worked again. As I did, you can comment your previous code and try.

Http Post request with content type application/x-www-form-urlencoded not working in Spring

You have to tell Spring what input content-type is supported by your service. You can do this with the "consumes" Annotation Element that corresponds to your request's "Content-Type" header.

@RequestMapping(value = "/", method = RequestMethod.POST, consumes = {"application/x-www-form-urlencoded"})

It would be helpful if you posted your code.

Visualizing decision tree in scikit-learn

I copy and change a part of your code as the below:

from pandas import read_csv, DataFrame
from sklearn import tree
from sklearn.tree import DecisionTreeClassifier
from os import system

data = read_csv('D:/training.csv')
Y = data.Y
X = data.ix[:,"X0":"X33"]

dtree = tree.DecisionTreeClassifier(criterion = "entropy")
dtree = dtree.fit(X, Y)

After making sure you have dtree, which means that the above code runs well, you add the below code to visualize decision tree:

Remember to install graphviz first: pip install graphviz

import graphviz 
from graphviz import Source
dot_data = tree.export_graphviz(dtree, out_file=None, feature_names=X.columns)
graph = graphviz.Source(dot_data) 
graph.render("name of file",view = True)

I tried with my data, visualization worked well and I got a pdf file viewed immediately.

Does WhatsApp offer an open API?

WhatsApp does not have a API available for public use. As you put it, it's a closed system.

However, they provide several other ways in which your iPhone application can interact with WhatsApp: through custom URL schemes, share extension and through the Document Interaction API.

See this WhatsApp FAQ article.

What is the proper way to comment functions in Python?

I would go a step further than just saying "use a docstring". Pick a documentation generation tool, such as pydoc or epydoc (I use epydoc in pyparsing), and use the markup syntax recognized by that tool. Run that tool often while you are doing your development, to identify holes in your documentation. In fact, you might even benefit from writing the docstrings for the members of a class before implementing the class.

Oracle: how to UPSERT (update or insert into a table?)

The MERGE statement merges data between two tables. Using DUAL allows us to use this command. Note that this is not protected against concurrent access.

create or replace
procedure ups(xa number)
as
begin
    merge into mergetest m using dual on (a = xa)
         when not matched then insert (a,b) values (xa,1)
             when matched then update set b = b+1;
end ups;
/
drop table mergetest;
create table mergetest(a number, b number);
call ups(10);
call ups(10);
call ups(20);
select * from mergetest;

A                      B
---------------------- ----------------------
10                     2
20                     1

What is the 'dynamic' type in C# 4.0 used for?

I am surprised that nobody mentioned multiple dispatch. The usual way to work around this is via Visitor pattern and that is not always possible so you end up with stacked is checks.

So here is a real life example of an application of my own. Instead of doing:

public static MapDtoBase CreateDto(ChartItem item)
{
    if (item is ElevationPoint) return CreateDtoImpl((ElevationPoint)item);
    if (item is MapPoint) return CreateDtoImpl((MapPoint)item);
    if (item is MapPolyline) return CreateDtoImpl((MapPolyline)item);
    //other subtypes follow
    throw new ObjectNotFoundException("Counld not find suitable DTO for " + item.GetType());
}

You do:

public static MapDtoBase CreateDto(ChartItem item)
{
    return CreateDtoImpl(item as dynamic);
}

private static MapDtoBase CreateDtoImpl(ChartItem item)
{
    throw new ObjectNotFoundException("Counld not find suitable DTO for " + item.GetType());
}

private static MapDtoBase CreateDtoImpl(MapPoint item)
{
    return new MapPointDto(item);
}

private static MapDtoBase CreateDtoImpl(ElevationPoint item)
{
    return new ElevationDto(item);
}

Note that in first case ElevationPoint is subclass of MapPoint and if it's not placed before MapPointit will never be reached. This is not the case with dynamic, as the closest matching method will be called.

As you might guess from the code, that feature came handy while I was performing translation from ChartItem objects to their serializable versions. I didn't want to pollute my code with visitors and I didn't want also to pollute my ChartItem objects with useless serialization specific attributes.

Clear an input field with Reactjs?

Also after React v 16.8+ you have an ability to use hooks

import React, {useState} from 'react';

const ControlledInputs = () => {
  const [firstName, setFirstName] = useState(false);

  const handleSubmit = (e) => {
    e.preventDefault();
    if (firstName) {
      console.log('firstName :>> ', firstName);
    }
  };

  return (
    <>
      <form onSubmit={handleSubmit}>
          <label htmlFor="firstName">Name: </label>
          <input
            type="text"
            id="firstName"
            name="firstName"
            value={firstName}
            onChange={(e) => setFirstName(e.target.value)}
          />
        <button type="submit">add person</button>
      </form>
    </>
  );
};

Apache: client denied by server configuration

if you are having the

Allow from All

in httpd.conf then make sure us have

index.php

like in the below line in httpd.conf

DirectoryIndex index.html index.php

HTTP post XML data in C#

In General:

An example of an easy way to post XML data and get the response (as a string) would be the following function:

public string postXMLData(string destinationUrl, string requestXml)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(destinationUrl);
    byte[] bytes;
    bytes = System.Text.Encoding.ASCII.GetBytes(requestXml);
    request.ContentType = "text/xml; encoding='utf-8'";
    request.ContentLength = bytes.Length;
    request.Method = "POST";
    Stream requestStream = request.GetRequestStream();
    requestStream.Write(bytes, 0, bytes.Length);
    requestStream.Close();
    HttpWebResponse response;
    response = (HttpWebResponse)request.GetResponse();
    if (response.StatusCode == HttpStatusCode.OK)
    {
        Stream responseStream = response.GetResponseStream();
        string responseStr = new StreamReader(responseStream).ReadToEnd();
        return responseStr;
    }
    return null;
}

In your specific situation:

Instead of:

request.ContentType = "application/x-www-form-urlencoded";

use:

request.ContentType = "text/xml; encoding='utf-8'";

Also, remove:

string postData = "XMLData=" + Sendingxml;

And replace:

byte[] byteArray = Encoding.UTF8.GetBytes(postData);

with:

byte[] byteArray = Encoding.UTF8.GetBytes(Sendingxml.ToString());

Error creating bean with name 'entityManagerFactory' defined in class path resource : Invocation of init method failed

Try adding the following dependencies.

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
   <groupId>com.h2database</groupId>
   <artifactId>h2</artifactId>
</dependency> 

jquery .on() method with load event

To run function onLoad

jQuery(window).on("load", function(){
    ..code..
});

To run code onDOMContentLoaded (also called onready)

jQuery(document).ready(function(){
    ..code..
});

or the recommended shorthand for onready

jQuery(function($){
    ..code.. ($ is the jQuery object)
});

onready fires when the document has loaded

onload fires when the document and all the associated content, like the images on the page have loaded.

How to get the last element of a slice?

For just reading the last element of a slice:

sl[len(sl)-1]

For removing it:

sl = sl[:len(sl)-1]

See this page about slice tricks

Whether a variable is undefined

function my_url (base, opt)
{
    var retval = ["" + base];
    retval.push( opt.page_name ? "&page_name=" + opt.page_name : "");
    retval.push( opt.table_name ? "&table_name=" + opt.table_name : "");
    retval.push( opt.optionResult ? "&optionResult=" + opt.optionResult : "");
    return retval.join("");
}

my_url("?z=z",  { page_name : "pageX" /* no table_name and optionResult */ } );

/* Returns:
     ?z=z&page_name=pageX
*/

This avoids using typeof whatever === "undefined". (Also, there isn't any string concatenation.)

What is Vim recording and how can it be disabled?

Type :h recording to learn more.

                           *q* *recording*
q{0-9a-zA-Z"}           Record typed characters into register {0-9a-zA-Z"}
                        (uppercase to append).  The 'q' command is disabled
                        while executing a register, and it doesn't work inside
                        a mapping.  {Vi: no recording}

q                       Stops recording.  (Implementation note: The 'q' that
                        stops recording is not stored in the register, unless
                        it was the result of a mapping)  {Vi: no recording}


                                                        *@*
@{0-9a-z".=*}           Execute the contents of register {0-9a-z".=*} [count]
                        times.  Note that register '%' (name of the current
                        file) and '#' (name of the alternate file) cannot be
                        used.  For "@=" you are prompted to enter an
                        expression.  The result of the expression is then
                        executed.  See also |@:|.  {Vi: only named registers}

Confusion: @NotNull vs. @Column(nullable = false) with JPA and Hibernate

@NotNull is a JSR 303 Bean Validation annotation. It has nothing to do with database constraints itself. As Hibernate is the reference implementation of JSR 303, however, it intelligently picks up on these constraints and translates them into database constraints for you, so you get two for the price of one. @Column(nullable = false) is the JPA way of declaring a column to be not-null. I.e. the former is intended for validation and the latter for indicating database schema details. You're just getting some extra (and welcome!) help from Hibernate on the validation annotations.

"Could not find bundler" error

Just in case, I had similar error with bundler 2.1.2 and solved it with:

sudo gem install bundler -v 1.17.3

If you have several bundler versions installed, then you can run specific version of bundle this way: bundle _1.17.3_ exec rspec

Though seems like later bundler versions are pretty buggy (had issues on 3 different projects on 2 operation systems), having one old bundler may work the best, at least this is what I have on my Ubuntu & MacOS

Latest bundler versions may override stable bundler -v 1.17.3. It can be not easy to remove latest bundler from system, here is what helped me:

Need to remove href values when printing in Chrome

_x000D_
_x000D_
@media print {_x000D_
   a[href]:after {_x000D_
      display: none;_x000D_
      visibility: hidden;_x000D_
   }_x000D_
}
_x000D_
_x000D_
_x000D_

Work's perfect.

Eclipse: Error ".. overlaps the location of another project.." when trying to create new project

Go to the actual FILE menu and create a new general project.

If the project type isn't recognized, preventing one of these import methods from working, then try this. Once you add the generic project, you can then add support for whatever language you require.

Pass entire form as data in jQuery Ajax function

serialize() is not a good idea if you want to send a form with post method. For example if you want to pass a file via ajax its not gonna work.

Suppose that we have a form with this id : "myform".

the better solution is to make a FormData and send it:

    var myform = document.getElementById("myform");
    var fd = new FormData(myform );
    $.ajax({
        url: "example.php",
        data: fd,
        cache: false,
        processData: false,
        contentType: false,
        type: 'POST',
        success: function (dataofconfirm) {
            // do something with the result
        }
    });

How to find the last day of the month from date?

An other way using mktime and not date('t') :

$dateStart= date("Y-m-d", mktime(0, 0, 0, 10, 1, 2016)); //2016-10-01
$dateEnd = date("Y-m-d", mktime(0, 0, 0, 11, 0, 2016)); //This will return the last day of october, 2016-10-31 :)

So this way it calculates either if it is 31,30 or 29

SQLPLUS error:ORA-12504: TNS:listener was not given the SERVICE_NAME in CONNECT_DATA

You're missing service name:

 SQL> connect username/password@hostname:port/SERVICENAME

EDIT

If you can connect to the database from other computer try running there:

select sys_context('USERENV','SERVICE_NAME') from dual

and

select sys_context('USERENV','SID') from dual

How can I match on an attribute that contains a certain string?

EDIT: see bobince's solution which uses contains rather than start-with, along with a trick to ensure the comparison is done at the level of a complete token (lest the 'atag' pattern be found as part of another 'tag').

"atag btag" is an odd value for the class attribute, but never the less, try:

//*[starts-with(@class,"atag")]

There is no ViewData item of type 'IEnumerable<SelectListItem>' that has the key 'xxx'

Check the Namespace.

You might assign System.Web.Webpages.Html.SelectListItem in the Controller, instead of System.Web.Mvc.SelectListItem.

CakePHP find method with JOIN

There are two main ways that you can do this. One of them is the standard CakePHP way, and the other is using a custom join.

It's worth pointing out that this advice is for CakePHP 2.x, not 3.x.

The CakePHP Way

You would create a relationship with your User model and Messages Model, and use the containable behavior:

class User extends AppModel {
    public $actsAs = array('Containable');
    public $hasMany = array('Message');
}

class Message extends AppModel {
    public $actsAs = array('Containable');
    public $belongsTo = array('User');
}

You need to change the messages.from column to be messages.user_id so that cake can automagically associate the records for you.

Then you can do this from the messages controller:

$this->Message->find('all', array(
    'contain' => array('User')
    'conditions' => array(
        'Message.to' => 4
    ),
    'order' => 'Message.datetime DESC'
));

The (other) CakePHP way

I recommend using the first method, because it will save you a lot of time and work. The first method also does the groundwork of setting up a relationship which can be used for any number of other find calls and conditions besides the one you need now. However, cakePHP does support a syntax for defining your own joins. It would be done like this, from the MessagesController:

$this->Message->find('all', array(
    'joins' => array(
        array(
            'table' => 'users',
            'alias' => 'UserJoin',
            'type' => 'INNER',
            'conditions' => array(
                'UserJoin.id = Message.from'
            )
        )
    ),
    'conditions' => array(
        'Message.to' => 4
    ),
    'fields' => array('UserJoin.*', 'Message.*'),
    'order' => 'Message.datetime DESC'
));

Note, I've left the field name messages.from the same as your current table in this example.

Using two relationships to the same model

Here is how you can do the first example using two relationships to the same model:

class User extends AppModel {
    public $actsAs = array('Containable');
    public $hasMany = array(
        'MessagesSent' => array(
            'className'  => 'Message',
            'foreignKey' => 'from'
         )
    );
    public $belongsTo = array(
        'MessagesReceived' => array(
            'className'  => 'Message',
            'foreignKey' => 'to'
         )
    );
}

class Message extends AppModel {
    public $actsAs = array('Containable');
    public $belongsTo = array(
        'UserFrom' => array(
            'className'  => 'User',
            'foreignKey' => 'from'
        )
    );
    public $hasMany = array(
        'UserTo' => array(
            'className'  => 'User',
            'foreignKey' => 'to'
        )
    );
}

Now you can do your find call like this:

$this->Message->find('all', array(
    'contain' => array('UserFrom')
    'conditions' => array(
        'Message.to' => 4
    ),
    'order' => 'Message.datetime DESC'
));

WARNING in budgets, maximum exceeded for initial

What is Angular CLI Budgets? Budgets is one of the less known features of the Angular CLI. It’s a rather small but a very neat feature!

As applications grow in functionality, they also grow in size. Budgets is a feature in the Angular CLI which allows you to set budget thresholds in your configuration to ensure parts of your application stay within boundaries which you setOfficial Documentation

Or in other words, we can describe our Angular application as a set of compiled JavaScript files called bundles which are produced by the build process. Angular budgets allows us to configure expected sizes of these bundles. More so, we can configure thresholds for conditions when we want to receive a warning or even fail build with an error if the bundle size gets too out of control!

How To Define A Budget? Angular budgets are defined in the angular.json file. Budgets are defined per project which makes sense because every app in a workspace has different needs.

Thinking pragmatically, it only makes sense to define budgets for the production builds. Prod build creates bundles with “true size” after applying all optimizations like tree-shaking and code minimization.

Oops, a build error! The maximum bundle size was exceeded. This is a great signal that tells us that something went wrong…

  1. We might have experimented in our feature and didn’t clean up properly
  2. Our tooling can go wrong and perform a bad auto-import, or we pick bad item from the suggested list of imports
  3. We might import stuff from lazy modules in inappropriate locations
  4. Our new feature is just really big and doesn’t fit into existing budgets

First Approach: Are your files gzipped?

Generally speaking, gzipped file has only about 20% the size of the original file, which can drastically decrease the initial load time of your app. To check if you have gzipped your files, just open the network tab of developer console. In the “Response Headers”, if you should see “Content-Encoding: gzip”, you are good to go.

How to gzip? If you host your Angular app in most of the cloud platforms or CDN, you should not worry about this issue as they probably have handled this for you. However, if you have your own server (such as NodeJS + expressJS) serving your Angular app, definitely check if the files are gzipped. The following is an example to gzip your static assets in a NodeJS + expressJS app. You can hardly imagine this dead simple middleware “compression” would reduce your bundle size from 2.21MB to 495.13KB.

const compression = require('compression')
const express = require('express')
const app = express()
app.use(compression())

Second Approach:: Analyze your Angular bundle

If your bundle size does get too big you may want to analyze your bundle because you may have used an inappropriate large-sized third party package or you forgot to remove some package if you are not using it anymore. Webpack has an amazing feature to give us a visual idea of the composition of a webpack bundle.

enter image description here

It’s super easy to get this graph.

  1. npm install -g webpack-bundle-analyzer
  2. In your Angular app, run ng build --stats-json (don’t use flag --prod). By enabling --stats-json you will get an additional file stats.json
  3. Finally, run webpack-bundle-analyzer ./dist/stats.json and your browser will pop up the page at localhost:8888. Have fun with it.

ref 1: How Did Angular CLI Budgets Save My Day And How They Can Save Yours

ref 2: Optimize Angular bundle size in 4 steps

How to configure robots.txt to allow everything?

That file will allow all crawlers access

User-agent: *
Allow: /

This basically allows all user agents (the *) to all parts of the site (the /).

Autoreload of modules in IPython

REVISED - please see Andrew_1510's answer below, as IPython has been updated.

...

It was a bit hard figure out how to get there from a dusty bug report, but:

It ships with IPython now!

import ipy_autoreload
%autoreload 2
%aimport your_mod

# %autoreload? for help

... then every time you call your_mod.dwim(), it'll pick up the latest version.

multiple where condition codeigniter

you can use an array and pass the array.

Associative array method:
$array = array('name' => $name, 'title' => $title, 'status' => $status);

$this->db->where($array); 

// Produces: WHERE name = 'Joe' AND title = 'boss' AND status = 'active'

Or if you want to do something other than = comparison

$array = array('name !=' => $name, 'id <' => $id, 'date >' => $date);

$this->db->where($array);

Strange Jackson exception being thrown when serializing Hibernate object

I am New to Jackson API, when i got the "org.codehaus.jackson.map.JsonMappingException: No serializer found for class com.company.project.yourclass" , I added the getter and setter to com.company.project.yourclass, that helped me to use the ObjectMapper's mapper object to write the java object into a flat file.

HTML Input Box - Disable

<input type="text" required="true" value="" readonly>

Not the.

<input type="text" required="true" value="" readonly="true">

$(document).ready equivalent without jQuery

Works in all known browsers (tested via BrowserStack). IE6+, Safari 1+, Chrome 1+, Opera, etc. Uses DOMContentLoaded, with fallbacks to document.documentElement.doScroll() and window.onload.

/*! https://github.com/Kithraya/DOMContentLoaded v1.2.6 | MIT License */

DOMContentLoaded.version = "1.2.6";

function DOMContentLoaded() { "use strict";
    
    var ael = 'addEventListener', rel = 'removeEventListener', aev = 'attachEvent', dev = 'detachEvent';
    var alreadyRun = false, // for use in the idempotent function ready()
        funcs = arguments;
    
    // old versions of JS return '[object Object]' for null.
    function type(obj) { return (obj === null) ? 'null' : Object.prototype.toString.call(obj).slice(8,-1).toLowerCase() }
    function microtime() { return + new Date() } 
    
     /* document.readyState === 'complete' reports correctly in every browser I have tested, including IE.
        But IE6 to 10 don't return the correct readyState values as per the spec:
        readyState is sometimes 'interactive', even when the DOM isn't accessible in IE6/7 so checking for the onreadystatechange event like jQuery does is not optimal
        readyState is complete at basically the same time as 'window.onload' (they're functionally equivalent, within a few tenths of a second)
        Accessing undefined properties of a defined object (document) will not throw an error (in case readyState is undefined).
     */
    
    // Check for IE < 11 via conditional compilation
    /// values: 5?: IE5, 5.5?: IE5.5, 5.6/5.7: IE6/7, 5.8: IE8, 9: IE9, 10: IE10, 11*: (IE11 older doc mode), undefined: IE11 / NOT IE
    var jscript_version = Number( new Function("/*@cc_on return @_jscript_version; @*\/")() ) || NaN;
    
    // check if the DOM has already loaded
    if (document.readyState === 'complete') { ready(null); return; }  // here we send null as the readyTime, since we don't know when the DOM became ready.
    
    if (jscript_version < 9) { doIEScrollCheck(); return; } // For IE<9 poll document.documentElement.doScroll(), no further actions are needed.
    
     /* 
        Chrome, Edge, Firefox, IE9+, Opera 9+, Safari 3.1+, Android Webview, Chrome for Android, Edge Mobile, 
        Firefox for Android 4+, Opera for Android, iOS Safari, Samsung Internet, etc, support addEventListener
        And IE9+ supports 'DOMContentLoaded' 
     */
        
    if (document[ael]) {
        document[ael]("DOMContentLoaded", ready, false); 
        window[ael]("load", ready, false); // fallback to the load event in case addEventListener is supported, but not DOMContentLoaded
    } else 
    if (aev in window) { window[aev]('onload', ready);
        /* Old Opera has a default of window.attachEvent being falsy, so we use the in operator instead
           https://dev.opera.com/blog/window-event-attachevent-detachevent-script-onreadystatechange/

           Honestly if somebody is using a browser so outdated AND obscure (like Opera 7 where neither addEventListener 
           nor "DOMContLoaded" is supported, they deserve to wait for the full page).
           I CBA testing whether readyState === 'interactive' is truly interactive in browsers designed in 2003. I just assume it isn't (like in IE6-8). 
        */
    } else { // fallback to queue window.onload that will always work
       addOnload(ready);
    }
    
    
    // This function allows us to preserve any original window.onload handlers (in super old browsers where this is even necessary), 
    // while keeping the option to chain onloads, and dequeue them.
    
    function addOnload(fn) { var prev = window.onload; // old window.onload, which could be set by this function, or elsewhere
        
        // we add a function queue list to allow for dequeueing 
        // addOnload.queue is the queue of functions that we will run when when the DOM is ready
        if ( type( addOnload.queue ) !== 'array') { addOnload.queue = [];
            if ( type(prev) === 'function') { addOnload.queue.push( prev ); } // add the previously defined event handler
        }
        
        if (typeof fn === 'function') { addOnload.queue.push(fn) }

        window.onload = function() { // iterate through the queued functions
            for (var i = 0; i < addOnload.queue.length; i++) { addOnload.queue[i]() } 
        };
    }   

    // remove a queued window.onload function from the chain (simplified); 
    
    function dequeueOnload(fn) { var q = addOnload.queue, i = 0;
    
        // sort through the queued functions in addOnload.queue until we find `fn`
        if (type( q ) === 'array') {        // if found, remove from the queue
            for (; i < q.length; i++) { ;;(fn === q[i]) ? q.splice(i, 1) : 0; } // void( (fn === q[i]) ? q.splice(i, 1) : 0 ) 
        }
    }
    
    function ready(ev) { // idempotent event handler function
        if (alreadyRun) {return} alreadyRun = true; 
        
        // this time is when the DOM has loaded (or if all else fails, when it was actually possible to inference the DOM has loaded via a 'load' event)
        // perhaps this should be `null` if we have to inference readyTime via a 'load' event, but this functionality is better.
        var readyTime = microtime(); 
        
        detach(); // detach any event handlers
                        
        // run the functions
        for (var i=0; i < funcs.length; i++) {  var func = funcs[i];
            
            if (type(func) === 'function') {
                func.call(document, { 'readyTime': (ev === null ? null : readyTime), 'funcExecuteTime': microtime() }, func); 
                // jquery calls 'ready' with `this` being set to document, so we'll do the same. 
            }       
        }
    }

    function detach() {
        if (document[rel]) { 
            document[rel]("DOMContentLoaded", ready); window[rel]("load", ready);
        } else
        if (dev in window) { window[dev]("onload", ready); } 
        else {
            dequeueOnload(ready);
        }                                                               
    }
    
    function doIEScrollCheck() { // for use in IE < 9 only.
        if ( window.frameElement ) { 
            // we're in an <iframe> or similar
            // the document.documentElemeent.doScroll technique does not work if we're not at the top-level (parent document)

            try { window.attachEvent("onload", ready); } catch (e) { } // attach to onload if were in an <iframe> in IE as there's no way to tell otherwise
            
            return;
        } 
        try {
            document.documentElement.doScroll('left');  // when this statement no longer throws, the DOM is accessible in old IE
        } catch(error) {
            setTimeout(function() {
                (document.readyState === 'complete') ? ready() : doIEScrollCheck();
            }, 50);
            return;
        }
        ready();
    }
}

Usage:

<script>
DOMContentLoaded(function(e) { console.log(e) });
</script>

Is there a way to use shell_exec without waiting for the command to complete?

You can also give your output back to the client instantly and continue processing your PHP code afterwards.

This is the method I am using for long-waiting Ajax calls which would not have any effect on client side:

ob_end_clean();
ignore_user_abort();
ob_start();
header("Connection: close");
echo json_encode($out);
header("Content-Length: " . ob_get_length());
ob_end_flush();
flush();
// execute your command here. client will not wait for response, it already has one above.

You can find the detailed explanation here: http://oytun.co/response-now-process-later

ActionController::UnknownFormat

You can also modify your config/routes.rb file like:

 get 'ajax/:action', to: 'ajax#:action', :defaults => { :format => 'json' }

Which will default the format to json. It is working fine for me in Rails 4.

Or if you want to go even further and you are using namespaces, you can cut down the duplicates:

namespace :api, defaults: {format: 'json'} do
   #your controller routes here ...
end

with the above everything under /api will be formatted as json by default.

I can't find my git.exe file in my Github folder

The path for the latest version of Git is changed, In my laptop, I found it in

C:\Users\Anum Sheraz\AppData\Local\Programs\Git\bin\git.exe

This resolved my issue of path. Hope that helps to someone :)

End-line characters from lines read from text file, using Python

Simple. Use splitlines()

L = open("myFile.txt", "r").read().splitlines();
for line in L: 
    process(line) # this 'line' will not have '\n' character at the end

How do I replace all line breaks in a string with <br /> elements?

This worked for me when value came from a TextBox:

string.replace(/\n|\r\n|\r/g, '<br/>');

Angular 2 How to redirect to 404 or other path if the path does not exist

As shaishab roy says, in the cheat sheet you can find the answer.

But in his answer, the given response was :

{path: '/home/...', name: 'Home', component: HomeComponent}
{path: '/', redirectTo: ['Home']},
{path: '/user/...', name: 'User', component: UserComponent},
{path: '/404', name: 'NotFound', component: NotFoundComponent},

{path: '/*path', redirectTo: ['NotFound']}

For some reasons, it doesn't works on my side, so I tried instead :

{path: '/**', redirectTo: ['NotFound']}

and it works. Be careful and don't forget that you need to put it at the end, or else you will often have the 404 error page ;).

Do not want scientific notation on plot axis

Use options(scipen=5) or some other high enough number. The scipen option determines how likely R is to switch to scientific notation, the higher the value the less likely it is to switch. Set the option before making your plot, if it still has scientific notation, set it to a higher number.

open_basedir restriction in effect. File(/) is not within the allowed path(s):

Modify the open_basedir settings in your PHP configuration (See Runtime Configuration).

The open_basedir setting is primarily used to prevent PHP scripts for a particular user from accessing files in another user's account. So usually, any files in your own account should be readable by your own scripts.

Example settings via .htaccess if PHP runs as Apache module on a Linux system:

<DirectoryMatch "/home/sites/site81/">
    php_admin_value open_basedir "/home/sites/site81/:/tmp/:/"
</DirectoryMatch>

How to convert 'binary string' to normal string in Python3?

Decode it.

>>> b'a string'.decode('ascii')
'a string'

To get bytes from string, encode it.

>>> 'a string'.encode('ascii')
b'a string'

HTML input arrays

It's just PHP, not HTML.

It parses all HTML fields with [] into an array.

So you can have

<input type="checkbox" name="food[]" value="apple" />
<input type="checkbox" name="food[]" value="pear" />

and when submitted, PHP will make $_POST['food'] an array, and you can access its elements like so:

echo $_POST['food'][0]; // would output first checkbox selected

or to see all values selected:

foreach( $_POST['food'] as $value ) {
    print $value;
}

Anyhow, don't think there is a specific name for it

GridView Hide Column by code

This was the code that worked for me when the column Id is unknown and the AutoGenerateColumns == true;

<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Drawing" %>
<html>
<head runat="server">
    <script runat="server">
        protected void Page_Load(object sender, EventArgs eventArgs)
        {
            DataTable data = new DataTable();
            data.Columns.Add("Id", typeof(int));
            data.Columns.Add("Notes", typeof(string));
            data.Columns.Add("RequestedDate", typeof(DateTime));
            for (int idx = 0; idx < 5; idx++)
            {
                DataRow row = data.NewRow();
                row["Id"] = idx;
                row["Notes"] = string.Format("Note {0}", idx);
                row["RequestedDate"] = DateTime.Now.Subtract(new TimeSpan(idx, 0, 0, 0, 0));
                data.Rows.Add(row);
            }
            listData.DataSource = data;
            listData.DataBind();
        }

        private void GridView_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            foreach (TableCell tableCell in e.Row.Cells)
            {
                DataControlFieldCell cell = (DataControlFieldCell)tableCell;
                if (cell.ContainingField.HeaderText == "Id")
                {
                    cell.Visible = false;
                    continue;
                }
                if (cell.ContainingField.HeaderText == "Notes")
                {
                    cell.Width = 400;
                    cell.BackColor = Color.Blue;
                    continue;
                }
                if (cell.ContainingField.HeaderText == "RequestedDate")
                {
                    cell.Width = 130;
                    continue;
                }
            }
        }

    </script>
</head>
<body>
    <form runat="server">
        <asp:GridView runat="server" ID="listData" AutoGenerateColumns="True" HorizontalAlign="Left"
            PageSize="20" OnRowDataBound="GridView_RowDataBound" EmptyDataText="No Data Available."
            Width="95%">
        </asp:GridView>
    </form>
</body>
</html>

Hashmap with Streams in Java 8 Streams to collect value of Map

Maybe the sample is oversimplified, but you don't need the Java stream API here. Just use the Map directly.

 List<String> list1 = id1.get(1); // this will return the list from your map

What does "commercial use" exactly mean?

I suggest this discriminative question:

Is the open-source tool necessary in your process of making money?

  • a blog engine on your commercial web site is necessary: commercial use.
  • winamp for listening to music is not necessary: non-commercial use.

How do I generate sourcemaps when using babel and webpack?

In order to use source map, you should change devtool option value from true to the value which available in this list, for instance source-map

devtool: 'source-map'

devtool: 'source-map' - A SourceMap is emitted.

SELECT DISTINCT on one column

SELECT min (id) AS 'ID', min(sku) AS 'SKU', Product
    FROM TestData
    WHERE sku LIKE 'FOO%' -- If you want only the sku that matchs with FOO%
    GROUP BY product 
    ORDER BY 'ID'

Force unmount of NFS-mounted directory

Try running

lsof | grep /mnt/data

That should list any process that is accessing /mnt/data that would prevent it from being unmounted.

Javascript - Track mouse position

I believe that we are overthinking this,

_x000D_
_x000D_
function mouse_position(e)_x000D_
{_x000D_
//do stuff_x000D_
}
_x000D_
<body onmousemove="mouse_position(event)"></body>
_x000D_
_x000D_
_x000D_

Run javascript function when user finishes typing instead of on key up?

Modifying the accepted answer to handle additional cases such as paste:

//setup before functions
var typingTimer;                //timer identifier
var doneTypingInterval = 2000;  //time in ms, 2 second for example
var $input = $('#myInput');

// updated events 
$input.on('input propertychange paste', function () {
    clearTimeout(typingTimer);
    typingTimer = setTimeout(doneTyping, doneTypingInterval);      
});

//user is "finished typing," do something
function doneTyping () {
  //do something
}

Adding click event for a button created dynamically using jQuery

Use

$(document).on("click", "#btn_a", function(){
  alert ('button clicked');
});

to add the listener for the dynamically created button.

alert($("#btn_a").val());

will give you the value of the button

How to change node.js's console font color?

paint-console

Simple colorable log. Support inspect objects and single line update This package just repaint console.

install

npm install paint-console

usage

require('paint-console');

console.info('console.info();');
console.warn('console.warn();');
console.error('console.error();');
console.log('console.log();');

demo

Powershell Execute remote exe with command line arguments on remote computer

$sb = ScriptBlock::Create("$command")
Invoke-Command -ScriptBlock $sb

This should work and avoid misleading the beginners.

Ansible: filter a list by its attributes

I've submitted a pull request (available in Ansible 2.2+) that will make this kinds of situations easier by adding jmespath query support on Ansible. In your case it would work like:

- debug: msg="{{ addresses | json_query(\"private_man[?type=='fixed'].addr\") }}"

would return:

ok: [localhost] => {
    "msg": [
        "172.16.1.100"
    ]
}

Migration: Cannot add foreign key constraint

I had this issue with laravel 5.8 and i fixed this code, as shown here in Laravel documentation, to where ever i am adding a foreign key.

$table->unsignedBigInteger('user_id');
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

then i ran $ php artisan migrate:refresh

Since this syntax is rather verbose, Laravel provides additional, terser methods that use convention to provide a better developer experience. The example above could be written like so:

Schema::table('posts', function (Blueprint $table) {
    $table->foreignId('user_id')->constrained()->onDelete('cascade');
});

How to loop over files in directory and change path and add suffix to filename

for file in Data/*.txt
do
    for ((i = 0; i < 3; i++))
    do
        name=${file##*/}
        base=${name%.txt}
        ./MyProgram.exe "$file" Logs/"${base}_Log$i.txt"
    done
done

The name=${file##*/} substitution (shell parameter expansion) removes the leading pathname up to the last /.

The base=${name%.txt} substitution removes the trailing .txt. It's a bit trickier if the extensions can vary.

How to hide a div after some time period?

Here's a complete working example based on your testing. Compare it to what you have currently to figure out where you are going wrong.

<html> 
  <head> 
    <title>Untitled Document</title> 
    <script type="text/javascript" src="http://code.jquery.com/jquery-latest.js"></script>
    <script type="text/javascript"> 
      $(document).ready( function() {
        $('#deletesuccess').delay(1000).fadeOut();
      });
    </script>
  </head> 
  <body> 
    <div id=deletesuccess > hiiiiiiiiiii </div> 
  </body> 
</html>

404 Not Found The requested URL was not found on this server

In my case (running the server locally on windows) I needed to clean the cache after changing the httpd.conf file.

\modules\apache\bin> ./htcacheclean.exe -t

Environment.GetFolderPath(...CommonApplicationData) is still returning "C:\Documents and Settings\" on Vista

I was looking for a listing of macOS but found nothing, maybe this helps someone.

Output on macOS Catalina (10.15.7) using net5.0

# SpecialFolders (Only with value)
SpecialFolder.ApplicationData: /Users/$USER/.config
SpecialFolder.CommonApplicationData: /usr/share
SpecialFolder.Desktop: /Users/$USER/Desktop
SpecialFolder.DesktopDirectory: /Users/$USER/Desktop
SpecialFolder.Favorites: /Users/$USER/Library/Favorites
SpecialFolder.Fonts: /Users/$USER/Library/Fonts
SpecialFolder.InternetCache: /Users/$USER/Library/Caches
SpecialFolder.LocalApplicationData: /Users/$USER/.local/share
SpecialFolder.MyDocuments: /Users/$USER
SpecialFolder.MyMusic: /Users/$USER/Music
SpecialFolder.MyPictures: /Users/$USER/Pictures
SpecialFolder.ProgramFiles: /Applications
SpecialFolder.System: /System
SpecialFolder.UserProfile: /Users/$USER

# SpecialFolders (All)
SpecialFolder.AdminTools: 
SpecialFolder.ApplicationData: /Users/$USER/.config
SpecialFolder.CDBurning: 
SpecialFolder.CommonAdminTools: 
SpecialFolder.CommonApplicationData: /usr/share
SpecialFolder.CommonDesktopDirectory: 
SpecialFolder.CommonDocuments: 
SpecialFolder.CommonMusic: 
SpecialFolder.CommonOemLinks: 
SpecialFolder.CommonPictures: 
SpecialFolder.CommonProgramFiles: 
SpecialFolder.CommonProgramFilesX86: 
SpecialFolder.CommonPrograms: 
SpecialFolder.CommonStartMenu: 
SpecialFolder.CommonStartup: 
SpecialFolder.CommonTemplates: 
SpecialFolder.CommonVideos: 
SpecialFolder.Cookies: 
SpecialFolder.Desktop: /Users/$USER/Desktop
SpecialFolder.DesktopDirectory: /Users/$USER/Desktop
SpecialFolder.Favorites: /Users/$USER/Library/Favorites
SpecialFolder.Fonts: /Users/$USER/Library/Fonts
SpecialFolder.History: 
SpecialFolder.InternetCache: /Users/$USER/Library/Caches
SpecialFolder.LocalApplicationData: /Users/$USER/.local/share
SpecialFolder.LocalizedResources: 
SpecialFolder.MyComputer: 
SpecialFolder.MyDocuments: /Users/$USER
SpecialFolder.MyMusic: /Users/$USER/Music
SpecialFolder.MyPictures: /Users/$USER/Pictures
SpecialFolder.MyVideos: 
SpecialFolder.NetworkShortcuts: 
SpecialFolder.PrinterShortcuts: 
SpecialFolder.ProgramFiles: /Applications
SpecialFolder.ProgramFilesX86: 
SpecialFolder.Programs: 
SpecialFolder.Recent: 
SpecialFolder.Resources: 
SpecialFolder.SendTo: 
SpecialFolder.StartMenu: 
SpecialFolder.Startup: 
SpecialFolder.System: /System
SpecialFolder.SystemX86: 
SpecialFolder.Templates: 
SpecialFolder.UserProfile: /Users/$USER
SpecialFolder.Windows: 

I have replaced my username with $USER.

Code Snippet from pogosama.

foreach(Environment.SpecialFolder f in Enum.GetValues(typeof(Environment.SpecialFolder)))
{
    string commonAppData = Environment.GetFolderPath(f);
    Console.WriteLine("{0}: {1}", f, commonAppData);
}
Console.ReadLine();

How to remove an item from an array in Vue.js

You can delete item through id

<button @click="deleteEvent(event.id)">Delete</button>

Inside your JS code

deleteEvent(id){
  this.events = this.events.filter((e)=>e.id !== id )
}

Vue wraps an observed array’s mutation methods so they will also trigger view updates. Click here for more details.

You might think this will cause Vue to throw away the existing DOM and re-render the entire list - luckily, that is not the case.

How do I set the background color of my main screen in Flutter?

There are many ways of doing it, I am listing few here.

  1. Using backgroundColor

    Scaffold(
      backgroundColor: Colors.black,
      body: Center(...),
    )
    
  2. Using Container in SizedBox.expand

    Scaffold(
      body: SizedBox.expand(
        child: Container(
          color: Colors.black,
          child: Center(...)
        ),
      ),
    )
    
  3. Using Theme

    Theme(
      data: Theme.of(context).copyWith(scaffoldBackgroundColor: Colors.black),
      child: Scaffold(
        body: Center(...),
      ),
    )
    

Swift alert view with OK and Cancel: which button tapped?

You may want to consider using SCLAlertView, alternative for UIAlertView or UIAlertController.

UIAlertController only works on iOS 8.x or above, SCLAlertView is a good option to support older version.

github to see the details

example:

let alertView = SCLAlertView()
alertView.addButton("First Button", target:self, selector:Selector("firstButton"))
alertView.addButton("Second Button") {
    print("Second button tapped")
}
alertView.showSuccess("Button View", subTitle: "This alert view has buttons")

How to update values in a specific row in a Python Pandas DataFrame?

I needed to update and add suffix to few rows of the dataframe on conditional basis based on the another column's value of the same dataframe -

df with column Feature and Entity and need to update Entity based on specific feature type

df2= df1 df.loc[df.Feature == 'dnb', 'Entity'] = 'duns_' + df.loc[df.Feature == 'dnb','Entity']

Disable output buffering

Variant that works without crashing (at least on win32; python 2.7, ipython 0.12) then called subsequently (multiple times):

def DisOutBuffering():
    if sys.stdout.name == '<stdout>':
        sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)

    if sys.stderr.name == '<stderr>':
        sys.stderr = os.fdopen(sys.stderr.fileno(), 'w', 0)

Creating an instance using the class name and calling constructor

Another helpful answer. How do I use getConstructor(params).newInstance(args)?

return Class.forName(**complete classname**)
    .getConstructor(**here pass parameters passed in constructor**)
    .newInstance(**here pass arguments**);

In my case, my class's constructor takes Webdriver as parameter, so used below code:

return Class.forName("com.page.BillablePage")
    .getConstructor(WebDriver.class)
    .newInstance(this.driver);

Aggregate / summarize multiple variables per group (e.g. sum, mean)

With the dplyr package, you can use summarise_all, summarise_at or summarise_if functions to aggregate multiple variables simultaneously. For the example dataset you can do this as follows:

library(dplyr)
# summarising all non-grouping variables
df2 <- df1 %>% group_by(year, month) %>% summarise_all(sum)

# summarising a specific set of non-grouping variables
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(x1, x2), sum)
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(-date), sum)

# summarising a specific set of non-grouping variables using select_helpers
# see ?select_helpers for more options
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(starts_with('x')), sum)
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(matches('.*[0-9]')), sum)

# summarising a specific set of non-grouping variables based on condition (class)
df2 <- df1 %>% group_by(year, month) %>% summarise_if(is.numeric, sum)

The result of the latter two options:

    year month        x1         x2
   <dbl> <dbl>     <dbl>      <dbl>
1   2000     1 -73.58134  -92.78595
2   2000     2 -57.81334 -152.36983
3   2000     3 122.68758  153.55243
4   2000     4 450.24980  285.56374
5   2000     5 678.37867  384.42888
6   2000     6 792.68696  530.28694
7   2000     7 908.58795  452.31222
8   2000     8 710.69928  719.35225
9   2000     9 725.06079  914.93687
10  2000    10 770.60304  863.39337
# ... with 14 more rows

Note: summarise_each is deprecated in favor of summarise_all, summarise_at and summarise_if.


As mentioned in my comment above, you can also use the recast function from the reshape2-package:

library(reshape2)
recast(df1, year + month ~ variable, sum, id.var = c("date", "year", "month"))

which will give you the same result.

System.loadLibrary(...) couldn't find native library in my case

Try to call your library after include PREBUILT_SHARED_LIBRARY section:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE    := libcalculate
LOCAL_SRC_FILES := <PATH>/libcalculate.so
include $(PREBUILT_SHARED_LIBRARY)

#...

LOCAL_SHARED_LIBRARIES += libcalculate

Update:

If you will use this library in Java you need compile it as shared library

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE    := libcalculate
LOCAL_SRC_FILES := <PATH>/libcalculate.so
include $(BUILD_SHARED_LIBRARY)

And you need deploy the library in the /vendor/lib directory.

How to determine the Schemas inside an Oracle Data Pump Export file

Assuming that you do not have the log file from the expdp job that generated the file in the first place, the easiest option would probably be to use the SQLFILE parameter to have impdp generate a file of DDL (based on a full import). Then you can grab the schema names from that file. Not ideal, of course, since impdp has to read the entire dump file to extract the DDL and then again to get to the schema you're interested in, and you have to do a bit of text file searching for the various CREATE USER statements, but it should be doable.

git commit error: pathspec 'commit' did not match any file(s) known to git

In my case, this error was due to special characters what I was considering double quotes as I copied the command from a web page.

How to uncheck checkbox using jQuery Uniform library

Looking at their docs, they have a $.uniform.update feature to refresh a "uniformed" element.

Example: http://jsfiddle.net/r87NH/4/

$("input:checkbox").uniform();

$("body").on("click", "#check1", function () {
    var two = $("#check2").attr("checked", this.checked);
    $.uniform.update(two);
});

git remote add with other SSH port

You can just do this:

git remote add origin ssh://user@host:1234/srv/git/example

1234 is the ssh port being used

How do I loop through or enumerate a JavaScript object?

Since ES2015 you can use the for of loop, to access the element directly:

// before ES2015
for(var key of elements){
  console.log(elements[key]);
}


// ES2015
for(let element of elements){
  console.log(element);
}

Hope this helps someone.

How to change checkbox's border style in CSS?

Styling checkboxes (and many other input elements for that mater) is not really possible with pure css if you want to drastically change the visual appearance.

Your best bet is to implement something like jqTransform does which actually replaces you inputs with images and applies javascript behaviour to it to mimic a checkbox (or other element for that matter)

Java method to swap primitives

I think this is the closest you can get to a simple swap, but it does not have a straightforward usage pattern:

int swap(int a, int b) {  // usage: y = swap(x, x=y);
   return a;
}

y = swap(x, x=y);

It relies on the fact that x will pass into swap before y is assigned to x, then x is returned and assigned to y.

You can make it generic and swap any number of objects of the same type:

<T> T swap(T... args) {   // usage: z = swap(a, a=b, b=c, ... y=z);
    return args[0];
}

c = swap(a, a=b, b=c)

Which programming languages can be used to develop in Android?

Scala is supported. See example.

Support for other languages is problematic:

7) Something like the dx tool can be forced into the phone, so that Java code could in principle continue to generate bytecodes, yet have them be translated into a VM-runnable form. But, at present, Java code cannot be generated on the fly. This means Dalvik cannot run dynamic languages (JRuby, Jython, Groovy). Yet. (Perhaps the dex format needs a detuned variant which can be easily generated from bytecodes.)

Error: Uncaught (in promise): Error: Cannot match any routes Angular 2

I also had the same issue. Tried all ways and it didn't work out until I added the following in app.module.ts

import { Ng4LoadingSpinnerModule } from 'ng4-loading-spinner';

And add the following in your imports in app.module.ts

Ng4LoadingSpinnerModule.forRoot()

This case might be rare but I hope this helps someone out there

XAMPP on Windows - Apache not starting

my friend this the will fix ur problem ;)

in root of folder ( xampp ) just run this file ( setup_xampp.bat ) then press enter

and try to start the apache server

every things will work like charm ;)

Invoking Java main method with parameters from Eclipse

AFAIK there isn't a built-in mechanism in Eclipse for this.

The closest you can get is to create a wrapper that prompts you for these values and invokes the (hardcoded) main. You then get you execution history as long as you don't clear terminated processes. Two variations on this are either to use JUNit, or to use injection or parameter so that your wrapper always connects to the correct class for its main.

Android - How to achieve setOnClickListener in Kotlin?

Add clickListener on button like this

    btUpdate.setOnClickListener(onclickListener)

add this code in your activity

 val onclickListener: View.OnClickListener = View.OnClickListener { view ->
        when (view.id) {
            R.id.btUpdate -> updateData()


        }
    }

How does JavaScript .prototype work?

It's just that you already have an object with Object.new but you still don't have an object when using the constructor syntax.

Any reason not to use '+' to concatenate two strings?

There is nothing wrong in concatenating two strings with +. Indeed it's easier to read than ''.join([a, b]).

You are right though that concatenating more than 2 strings with + is an O(n^2) operation (compared to O(n) for join) and thus becomes inefficient. However this has not to do with using a loop. Even a + b + c + ... is O(n^2), the reason being that each concatenation produces a new string.

CPython2.4 and above try to mitigate that, but it's still advisable to use join when concatenating more than 2 strings.

Retrieving a random item from ArrayList

The solution is not good, even you fixed your naming and unreachable statement of that print out.

things you should pay attention also 1. randomness seed, and large data, will num of item is so big returned num of that random < itemlist.size().

  1. you didn't handle multithread, you might get index out of bound exception

Is it possible to run an .exe or .bat file on 'onclick' in HTML

You can do it on Internet explorer with OCX component and on chrome browser using a chrome extension chrome document in any case need additional settings on the client system!

Important part of chrome extension source:

var port = chrome.runtime.connectNative("your.app.id"); 
      port.onMessage.addListener(onNativeMessage); 
      port.onDisconnect.addListener(onDisconnected);
      port.postMessage("send some data to STDIO");

permission file:

{
      "name": "your.app.id",
      "description": "Name of your extension",
      "path": "myapp.exe",
      "type": "stdio",
      "allowed_origins": [
            "chrome-extension://IDOFYOUREXTENSION_lokldaeplkmh/"
      ]
}

and windows registry settings:

HKEY_CURRENT_USER\Software\Google\Chrome\NativeMessagingHosts\your.app.id
REG_EXPAND_SZ : c:\permissionsettings.json

Convert JS object to JSON string

Check out updated/better way by Thomas Frank:

Update May 17, 2008: Small sanitizer added to the toObject-method. Now toObject() will not eval() the string if it finds any malicious code in it.For even more security: Don't set the includeFunctions flag to true.

Douglas Crockford, father of the JSON concept, wrote one of the first stringifiers for JavaScript. Later Steve Yen at Trim Path wrote a nice improved version which I have used for some time. It's my changes to Steve's version that I'd like to share with you. Basically they stemmed from my wish to make the stringifier:

  • handle and restore cyclical references
  • include the JavaScript code for functions/methods (as an option)
  • exclude object members from Object.prototype if needed.

Cannot find reference 'xxx' in __init__.py - Python / Pycharm

This is a bug in pycharm. PyCharm seems to be expecting the referenced module to be included in an __all__ = [] statement.

For proper coding etiquette, should you include the __all__ statement from your modules? ..this is actually the question we hear young Spock answering while he was being tested, to which he responded: "It is morally praiseworthy but not morally obligatory."

To get around it, you can simply disable that (extremely non-critical) (highly useful) inspection globally, or suppress it for the specific function or statement.

To do so:

  • put the caret over the erroring text ('choice', from your example above)
  • Bring up the intention menu (alt-enter by default, mine is set to alt-backspace)
  • hit the right arrow to open the submenu, and select the relevant action

PyCharm has its share of small bugs like this, but in my opinion its benefits far outweigh its drawbacks. If you'd like to try another good IDE, there's also Spyder/Spyderlib.

I know this is quite a bit after you asked your question, but I hope this helps (you, or someone else).

Edited: Originally, I thought that this was specific to checking __all__, but it looks like it's the more general 'Unresolved References' check, which can be very useful. It's probably best to use statement-level disabling of the feature, either by using the menu as mentioned above, or by specifying # noinspection PyUnresolvedReferences on the line preceding the statement.

Adding <script> to WordPress in <head> element

In your theme's functions.php:

function my_custom_js() {
    echo '<script type="text/javascript" src="myscript.js"></script>';
}
// Add hook for admin <head></head>
add_action( 'admin_head', 'my_custom_js' );
// Add hook for front-end <head></head>
add_action( 'wp_head', 'my_custom_js' );

C++ undefined reference to defined function

This could also happen if you are using CMake. If you have created a new class and you want to instantiate it, at the constructor call you will receive this error -even when the header and the cpp files are correct- if you have not modified CMakeLists.txt accordingly.

With CMake, every time you create a new class, before using it the header, the cpp files and any other compilable files (like Qt ui files) must be added to CMakeLists.txt and then re-run cmake . where CMakeLists.txt is stored.

For example, in this CMakeLists.txt file:

cmake_minimum_required(VERSION 2.8.11)

project(yourProject)

file(GLOB ImageFeatureDetector_SRC *.h *.cpp)

### Add your new files here ###
add_executable(yourProject YourNewClass.h YourNewClass.cpp otherNewFile.ui})

target_link_libraries(imagefeaturedetector ${SomeLibs})

If you are using the command file(GLOB yourProject_SRC *.h *.cpp) then you just need to re-run cmake . without modifying CMakeLists.txt.

Java2D: Increase the line width

What is Stroke:

The BasicStroke class defines a basic set of rendering attributes for the outlines of graphics primitives, which are rendered with a Graphics2D object that has its Stroke attribute set to this BasicStroke.

https://docs.oracle.com/javase/7/docs/api/java/awt/BasicStroke.html

Note that the Stroke setting:

Graphics2D g2 = (Graphics2D) g;
g2.setStroke(new BasicStroke(10));

is setting the line width,since BasicStroke(float width):

Constructs a solid BasicStroke with the specified line width and with default values for the cap and join styles.

And, it also effects other methods like Graphics2D.drawLine(int x1, int y1, int x2, int y2) and Graphics2D.drawRect(int x, int y, int width, int height):

The methods of the Graphics2D interface that use the outline Shape returned by a Stroke object include draw and any other methods that are implemented in terms of that method, such as drawLine, drawRect, drawRoundRect, drawOval, drawArc, drawPolyline, and drawPolygon.

How to get index using LINQ?

myCars.TakeWhile(car => !myCondition(car)).Count();

It works! Think about it. The index of the first matching item equals the number of (not matching) item before it.

Story time

I too dislike the horrible standard solution you already suggested in your question. Like the accepted answer I went for a plain old loop although with a slight modification:

public static int FindIndex<T>(this IEnumerable<T> items, Predicate<T> predicate) {
    int index = 0;
    foreach (var item in items) {
        if (predicate(item)) break;
        index++;
    }
    return index;
}

Note that it will return the number of items instead of -1 when there is no match. But let's ignore this minor annoyance for now. In fact the horrible standard solution crashes in that case and I consider returning an index that is out-of-bounds superior.

What happens now is ReSharper telling me Loop can be converted into LINQ-expression. While most of the time the feature worsens readability, this time the result was awe-inspiring. So Kudos to the JetBrains.

Analysis

Pros

  • Concise
  • Combinable with other LINQ
  • Avoids newing anonymous objects
  • Only evaluates the enumerable until the predicate matches for the first time

Therefore I consider it optimal in time and space while remaining readable.

Cons

  • Not quite obvious at first
  • Does not return -1 when there is no match

Of course you can always hide it behind an extension method. And what to do best when there is no match heavily depends on the context.

How to find the size of a table in SQL?

SQL Server:-

sp_spaceused 'TableName'

Or in management studio: Right Click on table -> Properties -> Storage

MySQL:-

SELECT table_schema, table_name, data_length, index_length FROM information_schema.tables

Sybase:-

sp_spaceused 'TableName'

Oracle:- how-do-i-calculate-tables-size-in-oracle

How to append to a file in Node?

Using fs.appendFile or fsPromises.appendFile are the fastest and the most robust options when you need to append something to a file.

In contrast to some of the answers suggested, if the file path is supplied to the appendFile function, It actually closes by itself. Only when you pass in a filehandle that you get by something like fs.open() you have to take care of closing it.

I tried it with over 50,000 lines in a file.

Examples :

(async () => {
  // using appendFile.
  const fsp = require('fs').promises;
  await fsp.appendFile(
    '/path/to/file', '\r\nHello world.'
  );

  // using apickfs; handles error and edge cases better.
  const apickFileStorage = require('apickfs');
  await apickFileStorage.writeLines(
    '/path/to/directory/', 'filename', 'Hello world.'
  );
})();

enter image description here

Ref: https://github.com/nodejs/node/issues/7560
Example Execution: https://github.com/apickjs/apickFS/blob/master/writeLines.js

Bootstrap 4 Center Vertical and Horizontal Alignment

None has worked for me. But his one did.

Since the Bootstrap 4 .row class is now display:flex you can simply use the new align-self-center flexbox utility on any column to vertically center it:

<div class="row">
   <div class="col-6 align-self-center">
      <div class="card card-block">
      Center
      </div>
   </div>
   <div class="col-6">
      <div class="card card-inverse card-danger">
      Taller
      </div>
   </div>
</div>

I learned about it from https://medium.com/wdstack/bootstrap-4-vertical-center-1211448a2eff

How to create a XML object from String in Java?

If you can create a string xml you can easily transform it to the xml document object e.g. -

String xmlString = "<?xml version=\"1.0\" encoding=\"utf-8\"?><a><b></b><c></c></a>";  

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();  
DocumentBuilder builder;  
try {  
    builder = factory.newDocumentBuilder();  
    Document document = builder.parse(new InputSource(new StringReader(xmlString)));  
} catch (Exception e) {  
    e.printStackTrace();  
} 

You can use the document object and xml parsing libraries or xpath to get back the ip address.

Formatting a float to 2 decimal places

The first thing you need to do is use the decimal type instead of float for the prices. Using float is absolutely unacceptable for that because it cannot accurately represent most decimal fractions.

Once you have done that, Decimal.Round() can be used to round to 2 places.

react hooks useEffect() cleanup for only componentWillUnmount?

instead of creating too many complicated functions and methods what I do is I create an event listener and automatically have mount and unmount done for me without having to worry about doing it manually. Here is an example.

//componentDidMount
useEffect( () => {

    window.addEventListener("load",  pageLoad);

    //component will unmount
    return () => {
       
        window.removeEventListener("load", pageLoad);
    }

 });

now that this part is done I just run anything I want from the pageLoad function like this.

const pageLoad = () =>{
console.log(I was mounted and unmounted automatically :D)}

Excel Macro - Select all cells with data and format as table

Try this one for current selection:

Sub A_SelectAllMakeTable2()
    Dim tbl As ListObject
    Set tbl = ActiveSheet.ListObjects.Add(xlSrcRange, Selection, , xlYes)
    tbl.TableStyle = "TableStyleMedium15"
End Sub

or equivalent of your macro (for Ctrl+Shift+End range selection):

Sub A_SelectAllMakeTable()
    Dim tbl As ListObject
    Dim rng As Range

    Set rng = Range(Range("A1"), Range("A1").SpecialCells(xlLastCell))
    Set tbl = ActiveSheet.ListObjects.Add(xlSrcRange, rng, , xlYes)
    tbl.TableStyle = "TableStyleMedium15"
End Sub

Refused to apply inline style because it violates the following Content Security Policy directive

You can use in Content-security-policy add "img-src 'self' data:;" And Use outline CSS.Don't use Inline CSS.It's secure from attackers.

Validation failed for one or more entities while saving changes to SQL Server Database using Entity Framework

This might be due to the maximum number of characters allowed for a specific column, like in sql one field might have following Data Type nvarchar(5) but the number of characters entered from the user is more than the specified, hence the error arises.

Setting a spinner onClickListener() in Android

Personally, I use that:

    final Spinner spinner = (Spinner) (view.findViewById(R.id.userList));
    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {                

            userSelectedIndex = position;
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {
        }
    });  

pandas dataframe convert column type to string or categorical

To convert a column into a string type (that will be an object column per se in pandas), use astype:

df.zipcode = zipcode.astype(str)

If you want to get a Categorical column, you can pass the parameter 'category' to the function:

df.zipcode = zipcode.astype('category')

Import pfx file into particular certificate store from command line

To anyone else looking for this, I wasn't able to use certutil -importpfx into a specific store, and I didn't want to download the importpfx tool supplied by jaspernygaard's answer in order to avoid the requirement of copying the file to a large number of servers. I ended up finding my answer in a powershell script shown here.

The code uses System.Security.Cryptography.X509Certificates to import the certificate and then moves it into the desired store:

function Import-PfxCertificate { 

    param([String]$certPath,[String]$certRootStore = “localmachine”,[String]$certStore = “My”,$pfxPass = $null) 
    $pfx = new-object System.Security.Cryptography.X509Certificates.X509Certificate2 

    if ($pfxPass -eq $null) 
    {
        $pfxPass = read-host "Password" -assecurestring
    } 

    $pfx.import($certPath,$pfxPass,"Exportable,PersistKeySet") 

    $store = new-object System.Security.Cryptography.X509Certificates.X509Store($certStore,$certRootStore) 
    $store.open("MaxAllowed") 
    $store.add($pfx) 
    $store.close() 
}

ThreadStart with parameters

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;

namespace ConsoleApp6
{
    class Program
    {
        static void Main(string[] args)
        {

            int x = 10;
            Thread t1 =new Thread(new ParameterizedThreadStart(order1));
            t1.IsBackground = true;//i can stope 
            t1.Start(x);

            Thread t2=new Thread(order2);
            t2.Priority = ThreadPriority.Highest;
            t2.Start();

            Console.ReadKey();
        }//Main

        static void  order1(object args)
        {
            int x = (int)args;


                for (int i = 0; i < x; i++)
            {
                Console.ForegroundColor = ConsoleColor.Green;
                Console.Write(i.ToString() + " ");
            }
        }

        static void order2()
        {
            for (int i = 100; i > 0; i--)
            {
                Console.ForegroundColor = ConsoleColor.Red;
                Console.Write(i.ToString() + " ");
            }
        }`enter code here`
    }
}

Is it possible to decompile a compiled .pyc file into a .py file?

Uncompyle6 works for Python 3.x and 2.7 - recommended option as it's most recent tool, aiming to unify earlier forks and focusing on automated unit testing. The GitHub page has more details.

  • if you use Python 3.7+, you could also try decompile3, a fork of Uncompyle6 focusing on 3.7 and higher.
  • do raise GitHub issues on these projects if needed - both run unit test suites on a range of Python versions

With these tools, you get your code back including variable names and docstrings, but without the comments.

The older Uncompyle2 supports Python 2.7 only. This worked well for me some time ago to decompile the .pyc bytecode into .py, whereas unpyclib crashed with an exception.

Subprocess check_output returned non-zero exit status 1

The command yum that you launch was executed properly. It returns a non zero status which means that an error occured during the processing of the command. You probably want to add some argument to your yum command to fix that.

Your code could show this error this way:

import subprocess
try:
    subprocess.check_output("dir /f",shell=True,stderr=subprocess.STDOUT)
except subprocess.CalledProcessError as e:
    raise RuntimeError("command '{}' return with error (code {}): {}".format(e.cmd, e.returncode, e.output))

php mail setup in xampp

Unless you have a mail server set up on your local computer, setting SMTP = localhost won't have any effect.

In days gone by (long ago), it was sufficient to set the value of SMTP to the address of your ISP's SMTP server. This now rarely works because most ISPs insist on authentication with a username and password. However, the PHP mail() function doesn't support SMTP authentication. It's designed to work directly with the mail transport agent of the local server.

You either need to set up a local mail server or to use a PHP classs that supports SMTP authentication, such as Zend_Mail or PHPMailer. The simplest solution, however, is to upload your mail processing script to your remote server.

Vue.js—Difference between v-model and v-bind

v-model is for two way bindings means: if you change input value, the bound data will be changed and vice versa. But v-bind:value is called one way binding that means: you can change input value by changing bound data but you can't change bound data by changing input value through the element.

v-model is intended to be used with form elements. It allows you to tie the form element (e.g. a text input) with the data object in your Vue instance.

Example: https://jsfiddle.net/jamesbrndwgn/j2yb9zt1/1/

v-bind is intended to be used with components to create custom props. This allows you to pass data to a component. As the prop is reactive, if the data that’s passed to the component changes then the component will reflect this change

Example: https://jsfiddle.net/jamesbrndwgn/ws5kad1c/3/

Hope this helps you with basic understanding.

LaTeX: remove blank page after a \part or \chapter

A solution that works:

Wrap the part of the document that needs this modified behavior with the code provided below. In my case the portion to wrap is a \part{} and some text following it.

\makeatletter\@openrightfalse
\part{Whatever}

Some text

\chapter{Foo}
\@openrighttrue\makeatother 

The wrapped portion should also include the chapter at the beginning of which this behavior needs to stop. Otherwise LaTeX may generate an empty page before this chapter.

Source: folks at the #latex IRC channel on irc.freenode.net

pow (x,y) in Java

Additionally for what was said, if you want integer powers of two, then 1 << x (or 1L << x) is a faster way to calculate 2x than Math.pow(2,x) or a multiplication loop, and is guaranteed to give you an int (or long) result.

It only uses the lowest 5 (or 6) bits of x (i.e. x & 31 (or x & 63)), though, shifting between 0 and 31 (or 63) bits.

HTML CSS Button Positioning

try changing that line-height change to a margin-top or padding-top change instead

#btnhome:active{
margin-top : 25px;
}

Edit: You could also try adding a span inside the button

<div id="header">           
    <button id="btnhome"><span>Home</span></button>          
    <button id="btnabout">About</button>
    <button id="btncontact">Contact</button>
    <button id="btnsup">Help Us</button>           
</div>

Then style that

#btnhome span:active { padding-top:25px;}

Way to insert text having ' (apostrophe) into a SQL table

try this

INSERT INTO exampleTbl VALUES('he doesn''t work for me')

How to recognize swipe in all 4 directions

You need to have one UISwipeGestureRecognizer for each direction. It's a little weird because the UISwipeGestureRecognizer.direction property is an options-style bit mask, but each recognizer can only handle one direction. You can send them all to the same handler if you want, and sort it out there, or send them to different handlers. Here's one implementation:

override func viewDidLoad() {
    super.viewDidLoad()

    let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(respondToSwipeGesture))
    swipeRight.direction = .right
    self.view.addGestureRecognizer(swipeRight)

    let swipeDown = UISwipeGestureRecognizer(target: self, action: #selector(respondToSwipeGesture))
    swipeDown.direction = .down
    self.view.addGestureRecognizer(swipeDown)
}

@objc func respondToSwipeGesture(gesture: UIGestureRecognizer) {

    if let swipeGesture = gesture as? UISwipeGestureRecognizer {

        switch swipeGesture.direction {
        case .right:
            print("Swiped right")
        case .down:
            print("Swiped down")
        case .left:
            print("Swiped left")
        case .up:
            print("Swiped up")
        default:
            break
        }
    }
}

Swift 3:

override func viewDidLoad() {
    super.viewDidLoad()

    let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(self.respondToSwipeGesture))
    swipeRight.direction = UISwipeGestureRecognizerDirection.right
    self.view.addGestureRecognizer(swipeRight)

    let swipeDown = UISwipeGestureRecognizer(target: self, action: #selector(self.respondToSwipeGesture))
    swipeDown.direction = UISwipeGestureRecognizerDirection.down
    self.view.addGestureRecognizer(swipeDown)
}

func respondToSwipeGesture(gesture: UIGestureRecognizer) {
    if let swipeGesture = gesture as? UISwipeGestureRecognizer {
        switch swipeGesture.direction {
        case UISwipeGestureRecognizerDirection.right:
            print("Swiped right")
        case UISwipeGestureRecognizerDirection.down:
            print("Swiped down")
        case UISwipeGestureRecognizerDirection.left:
            print("Swiped left")
        case UISwipeGestureRecognizerDirection.up:
            print("Swiped up")
        default:
            break
        }
    }
}

How to escape a single quote inside awk

This maybe what you're looking for:

awk 'BEGIN {FS=" ";} {printf "'\''%s'\'' ", $1}'

That is, with '\'' you close the opening ', then print a literal ' by escaping it and finally open the ' again.

inline if statement java, why is not working

The ternary operator ? : is to return a value, don't use it when you want to use if for flow control.

if (compareChar(curChar, toChar("0"))) getButtons().get(i).setText("§");

would work good enough.

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/operators.html

Eclipse error ... cannot be resolved to a type

Solved the problem by dropping the jar into WEB_INF/lib.

Read binary file as string in Ruby

To avoid leaving the file open, it is best to pass a block to File.open. This way, the file will be closed after the block executes.

contents = File.open('path-to-file.tar.gz', 'rb') { |f| f.read }

Finding the average of a list

suppose that

x = [
    [-5.01,-5.43,1.08,0.86,-2.67,4.94,-2.51,-2.25,5.56,1.03],
    [-8.12,-3.48,-5.52,-3.78,0.63,3.29,2.09,-2.13,2.86,-3.33],
    [-3.68,-3.54,1.66,-4.11,7.39,2.08,-2.59,-6.94,-2.26,4.33]
]

you can notice that x has dimension 3*10 if you need to get the mean to each row you can type this

theMean = np.mean(x1,axis=1)

don't forget to import numpy as np

How to get current formatted date dd/mm/yyyy in Javascript and append it to an input

You edit an element's value by editing it's .value property.

document.getElementById('DATE').value = 'New Value';

when do you need .ascx files and how would you use them?

It's an extension for the User Controls you have in your project.

A user control is a kind of composite control that works much like an ASP.NET Web page—you can add existing Web server controls and markup to a user control, and define properties and methods for the control. You can then embed them in ASP.NET Web pages, where they act as a unit.

Simply, if you want to have some functionality that will be used on many pages in your project then you should create a User control or Composite control and use it in your pages. It just helps you to keep the same functionality and code in one place. And it makes it reusable.

Modify XML existing content in C#

Forming a XML file

XmlTextWriter xmlw = new XmlTextWriter(@"C:\WINDOWS\Temp\exm.xml",System.Text.Encoding.UTF8);
xmlw.WriteStartDocument();            
xmlw.WriteStartElement("examtimes");
xmlw.WriteStartElement("Starttime");
xmlw.WriteString(DateTime.Now.AddHours(0).ToString());
xmlw.WriteEndElement();
xmlw.WriteStartElement("Changetime");
xmlw.WriteString(DateTime.Now.AddHours(0).ToString());
xmlw.WriteEndElement();
xmlw.WriteStartElement("Endtime");
xmlw.WriteString(DateTime.Now.AddHours(1).ToString());
xmlw.WriteEndElement();
xmlw.WriteEndElement();
xmlw.WriteEndDocument();  
xmlw.Close();           

To edit the Xml nodes use the below code

XmlDocument doc = new XmlDocument(); 
doc.Load(@"C:\WINDOWS\Temp\exm.xml"); 
XmlNode root = doc.DocumentElement["Starttime"]; 
root.FirstChild.InnerText = "First"; 
XmlNode root1 = doc.DocumentElement["Changetime"]; 
root1.FirstChild.InnerText = "Second"; 
doc.Save(@"C:\WINDOWS\Temp\exm.xml"); 

Try this. It's C# code.

Bind event to right mouse click

To disable right click context menu on all images of a page simply do this with following:

jQuery(document).ready(function(){
    // Disable context menu on images by right clicking
    for(i=0;i<document.images.length;i++) {
        document.images[i].onmousedown = protect;
    }
});

function protect (e) {
    //alert('Right mouse button not allowed!');
    this.oncontextmenu = function() {return false;};
}

MySQL select statement with CASE or IF ELSEIF? Not sure how to get the result

Syntax:

CASE value WHEN [compare_value] THEN result 
[WHEN [compare_value] THEN result ...] 
[ELSE result] 
END

Alternative: CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...]

mysql> SELECT CASE  WHEN 2>3 THEN 'this is true' ELSE 'this is false' END; 
+-------------------------------------------------------------+
| CASE  WHEN 2>3 THEN 'this is true' ELSE 'this is false' END |
+-------------------------------------------------------------+
| this is false                                               | 
+-------------------------------------------------------------+

I am use:

SELECT  act.*,
    CASE 
        WHEN (lises.session_date IS NOT NULL AND ses.session_date IS NULL) THEN lises.location_id
        WHEN (lises.session_date IS NULL AND ses.session_date IS NOT NULL) THEN ses.location_id
        WHEN (lises.session_date IS NOT NULL AND ses.session_date IS NOT NULL AND lises.session_date>ses.session_date) THEN ses.location_id
        WHEN (lises.session_date IS NOT NULL AND ses.session_date IS NOT NULL AND lises.session_date<ses.session_date) THEN lises.location_id
    END AS location_id
FROM activity AS act
LEFT JOIN li_sessions AS lises ON lises.activity_id = act.id AND  lises.session_date >= now()
LEFT JOIN session AS ses ON  ses.activity_id = act.id AND  ses.session_date >= now()
WHERE act.id

Uint8Array to string in Javascript

I was frustrated to see that people were not showing how to go both ways or showing that things work on none trivial UTF8 strings. I found a post on codereview.stackexchange.com that has some code that works well. I used it to turn ancient runes into bytes, to test some crypo on the bytes, then convert things back into a string. The working code is on github here. I renamed the methods for clarity:

// https://codereview.stackexchange.com/a/3589/75693
function bytesToSring(bytes) {
    var chars = [];
    for(var i = 0, n = bytes.length; i < n;) {
        chars.push(((bytes[i++] & 0xff) << 8) | (bytes[i++] & 0xff));
    }
    return String.fromCharCode.apply(null, chars);
}

// https://codereview.stackexchange.com/a/3589/75693
function stringToBytes(str) {
    var bytes = [];
    for(var i = 0, n = str.length; i < n; i++) {
        var char = str.charCodeAt(i);
        bytes.push(char >>> 8, char & 0xFF);
    }
    return bytes;
}

The unit test uses this UTF-8 string:

    // http://kermitproject.org/utf8.html
    // From the Anglo-Saxon Rune Poem (Rune version) 
    const secretUtf8 = `?????????????????????????????
?????????????????????????????????????????
?????????????????????????????????????`;

Note that the string length is only 117 characters but the byte length, when encoded, is 234.

If I uncomment the console.log lines I can see that the string that is decoded is the same string that was encoded (with the bytes passed through Shamir's secret sharing algorithm!):

unit test that demos encoding and decoding

What is the difference between pip and conda?

pip is a package manager.

conda is both a package manager and an environment manager.

Detail:

enter image description here

References

How can I hash a password in Java?

Among all the standard hash schemes, LDAP ssha is the most secure one to use,

http://www.openldap.org/faq/data/cache/347.html

I would just follow the algorithms specified there and use MessageDigest to do the hash.

You need to store the salt in your database as you suggested.

Is SMTP based on TCP or UDP?

In theory SMTP can be handled by either TCP, UDP, or some 3rd party protocol.

As defined in RFC 821, RFC 2821, and RFC 5321:

SMTP is independent of the particular transmission subsystem and requires only a reliable ordered data stream channel.

In addition, the Internet Assigned Numbers Authority has allocated port 25 for both TCP and UDP for use by SMTP.

In practice however, most if not all organizations and applications only choose to implement the TCP protocol. For example, in Microsoft's port listing port 25 is only listed for TCP and not UDP.


The big difference between TCP and UDP that makes TCP ideal here is that TCP checks to make sure that every packet is received and re-sends them if they are not whereas UDP will simply send packets and not check for receipt. This makes UDP ideal for things like streaming video where every single packet isn't as important as keeping a continuous flow of packets from the server to the client.

Considering SMTP, it makes more sense to use TCP over UDP. SMTP is a mail transport protocol, and in mail every single packet is important. If you lose several packets in the middle of the message the recipient might not even receive the message and if they do they might be missing key information. This makes TCP more appropriate because it ensures that every packet is delivered.

How to create a simple checkbox in iOS?

Yeah, no checkbox for you in iOS (-:

Here, this is what I did to create a checkbox:

UIButton *checkbox;
BOOL checkBoxSelected;
checkbox = [[UIButton alloc] initWithFrame:CGRectMake(x,y,20,20)];
// 20x20 is the size of the checkbox that you want
// create 2 images sizes 20x20 , one empty square and
// another of the same square with the checkmark in it
// Create 2 UIImages with these new images, then:

[checkbox setBackgroundImage:[UIImage imageNamed:@"notselectedcheckbox.png"]
                    forState:UIControlStateNormal];
[checkbox setBackgroundImage:[UIImage imageNamed:@"selectedcheckbox.png"]
                    forState:UIControlStateSelected];
[checkbox setBackgroundImage:[UIImage imageNamed:@"selectedcheckbox.png"]
                    forState:UIControlStateHighlighted];
checkbox.adjustsImageWhenHighlighted=YES;
[checkbox addTarget:(nullable id) action:(nonnull SEL) forControlEvents:(UIControlEvents)];
[self.view addSubview:checkbox];

Now in the target method do the following:

-(void)checkboxSelected:(id)sender
{
    checkBoxSelected = !checkBoxSelected; /* Toggle */
    [checkbox setSelected:checkBoxSelected];
}

That's it!

Find the similarity metric between two strings

Solution #1: Python builtin

use SequenceMatcher from difflib

pros: native python library, no need extra package.
cons: too limited, there are so many other good algorithms for string similarity out there.

example :
>>> from difflib import SequenceMatcher
>>> s = SequenceMatcher(None, "abcd", "bcde")
>>> s.ratio()
0.75

Solution #2: jellyfish library

its a very good library with good coverage and few issues. it supports:
- Levenshtein Distance
- Damerau-Levenshtein Distance
- Jaro Distance
- Jaro-Winkler Distance
- Match Rating Approach Comparison
- Hamming Distance

pros: easy to use, gamut of supported algorithms, tested.
cons: not native library.

example:

>>> import jellyfish
>>> jellyfish.levenshtein_distance(u'jellyfish', u'smellyfish')
2
>>> jellyfish.jaro_distance(u'jellyfish', u'smellyfish')
0.89629629629629637
>>> jellyfish.damerau_levenshtein_distance(u'jellyfish', u'jellyfihs')
1

UL list style not applying

All I can think of is that something is over-riding this afterwards.

You are including the reset styles first, right?

'0000-00-00 00:00:00' can not be represented as java.sql.Timestamp error

Append the following statement to the JDBC-mysql protocol:

?zeroDateTimeBehavior=convertToNull&autoReconnect=true&characterEncoding=UTF-8&characterSetResults=UTF-8

for example:

jdbc:mysql://localhost/infra?zeroDateTimeBehavior=convertToNull&autoReconnect=true&characterEncoding=UTF-8&characterSetResults=UTF-8

Split string based on a regular expression

By using (,), you are capturing the group, if you simply remove them you will not have this problem.

>>> str1 = "a    b     c      d"
>>> re.split(" +", str1)
['a', 'b', 'c', 'd']

However there is no need for regex, str.split without any delimiter specified will split this by whitespace for you. This would be the best way in this case.

>>> str1.split()
['a', 'b', 'c', 'd']

If you really wanted regex you can use this ('\s' represents whitespace and it's clearer):

>>> re.split("\s+", str1)
['a', 'b', 'c', 'd']

or you can find all non-whitespace characters

>>> re.findall(r'\S+',str1)
['a', 'b', 'c', 'd']

how to set "camera position" for 3d plots using python/matplotlib?

By "camera position," it sounds like you want to adjust the elevation and the azimuth angle that you use to view the 3D plot. You can set this with ax.view_init. I've used the below script to first create the plot, then I determined a good elevation, or elev, from which to view my plot. I then adjusted the azimuth angle, or azim, to vary the full 360deg around my plot, saving the figure at each instance (and noting which azimuth angle as I saved the plot). For a more complicated camera pan, you can adjust both the elevation and angle to achieve the desired effect.

    from mpl_toolkits.mplot3d import Axes3D
    ax = Axes3D(fig)
    ax.scatter(xx,yy,zz, marker='o', s=20, c="goldenrod", alpha=0.6)
    for ii in xrange(0,360,1):
        ax.view_init(elev=10., azim=ii)
        savefig("movie%d.png" % ii)

How to find out the number of CPUs using python

If you have python with a version >= 2.6 you can simply use

import multiprocessing

multiprocessing.cpu_count()

http://docs.python.org/library/multiprocessing.html#multiprocessing.cpu_count

XAMPP PORT 80 is Busy / EasyPHP error in Apache configuration file:

SQL Server Reporting Services (SSRS)
SSRS can remain active even if you uninstall SQL Server.
To stop the service:

Open SQL Server Configuration Manager. Select “SQL Server Services” in the left-hand pane. Double-click “SQL Server Reporting Services”. Hit Stop. Switch to the Service tab and set the Start Mode to “Manual”.


Skype
Irritatingly, Skype can switch to port 80. To disable it, select
Tools > Options > Advanced > Connection then uncheck
“Use port 80 and 443 as alternatives for incoming connections”.


IIS (Microsoft Internet Information Server)

For Windows 7 (or vista) its the most likely culprit. You can stop the service from the command line.

Open command line cmd.exe and type:

net stop was /y

For older versions of Windows type:

net stop iisadmin /y

Other

If this does not solve the problem further detective work is necessary if IIS, SSRS and Skype are not to blame. Enter the following on the command line:

netstat -ao

The active TCP addresses and ports will be listed. Locate the line with local address “0.0.0.0:80" and note the PID value. Start Task Manager. Navigate to the Processes tab and, if necessary, click View > Select Columns to ensure “PID (Process Identifier)” is checked. You can now locate the PID you noted above. The description and properties should help you determine which application is using the port.

How to show "if" condition on a sequence diagram?

If else condition, also called alternatives in UML terms can indeed be represented in sequence diagrams. Here is a link where you can find some nice resources on the subject http://www.ibm.com/developerworks/rational/library/3101.html

branching with alt

Regular vs Context Free Grammars

Regular grammar:- grammar containing production as follows is RG:

V->TV or VT
V->T

where V=variable and T=terminal

RG may be Left Linear Grammar or Right Liner Grammar, but not Middle linear Grammar.

As we know all RG are Linear Grammar but only Left Linear or Right Linear Grammar are RG.

A regular grammar can be ambiguous.

S->aA|aB
A->a
B->a

Ambiguous Grammar:- for a string x their exist more than one LMD or More than RMD or More than one Parse tree or One LMD and One RMD but both Produce different Parse tree.

                S                   S

              /   \               /   \
             a     A             a     B
                    \                   \
                     a                   a

this Grammar is ambiguous Grammar because two parse tree.

CFG:- A grammar said to be CFG if its Production is in form:

   V->@   where @ belongs to (V+T)*

DCFL:- as we know all DCFL are LL(1) Grammar and all LL(1) is LR(1) so it is Never be ambiguous. so DCFG is Never be ambiguous.

We also know all RL are DCFL so RL never be ambiguous. Note that RG may be ambiguous but RL not.

CFL: CFl May or may not ambiguous.

Note: RL never be Inherently ambiguous.

Modifying a query string without reloading the page

If you are looking for Hash modification, your solution works ok. However, if you want to change the query, you can use the pushState, as you said. Here it is an example that might help you to implement it properly. I tested and it worked fine:

if (history.pushState) {
    var newurl = window.location.protocol + "//" + window.location.host + window.location.pathname + '?myNewUrlQuery=1';
    window.history.pushState({path:newurl},'',newurl);
}

It does not reload the page, but it only allows you to change the URL query. You would not be able to change the protocol or the host values. And of course that it requires modern browsers that can process HTML5 History API.

For more information:

http://diveintohtml5.info/history.html

https://developer.mozilla.org/en-US/docs/Web/Guide/API/DOM/Manipulating_the_browser_history

Location for session files in Apache/PHP

The default session.save_path is set to "" which will evaluate to your system's temp directory. See this comment at https://bugs.php.net/bug.php?id=26757 stating:

The new default for save_path in upcoming releaess (sic) will be the empty string, which causes the temporary directory to be probed.

You can use sys_get_temp_dir to return the directory path used for temporary files

To find the current session save path, you can use

Refer to this answer to find out what the temp path is when this function returns an empty string.

Calculate age based on date of birth

Reference Link http://www.calculator.net/age-calculator.html

$hours_in_day   = 24;
$minutes_in_hour= 60;
$seconds_in_mins= 60;

$birth_date     = new DateTime("1988-07-31T00:00:00");
$current_date   = new DateTime();

$diff           = $birth_date->diff($current_date);

echo $years     = $diff->y . " years " . $diff->m . " months " . $diff->d . " day(s)"; echo "<br/>";
echo $months    = ($diff->y * 12) + $diff->m . " months " . $diff->d . " day(s)"; echo "<br/>";
echo $weeks     = floor($diff->days/7) . " weeks " . $diff->d%7 . " day(s)"; echo "<br/>";
echo $days      = $diff->days . " days"; echo "<br/>";
echo $hours     = $diff->h + ($diff->days * $hours_in_day) . " hours"; echo "<br/>";
echo $mins      = $diff->h + ($diff->days * $hours_in_day * $minutes_in_hour) . " minutest"; echo "<br/>";
echo $seconds   = $diff->h + ($diff->days * $hours_in_day * $minutes_in_hour * $seconds_in_mins) . " seconds"; echo "<br/>";

list.clear() vs list = new ArrayList<Integer>();

Tried the below program , With both the approach. 1. With clearing the arraylist obj in for loop 2. creating new New Arraylist in for loop.

List al= new ArrayList();
        for(int i=0;i<100;i++)
        {
            //List al= new ArrayList();

            for(int j=0;j<10;j++)
            {
                al.add(Integer.parseInt("" +j+i));
                //System.out.println("Obj val " +al.get(j));
            }
            //System.out.println("Hashcode : " + al.hashCode());
            al.clear();

        }

and to my surprise. the memory allocation didnt change much.

With New Arraylist approach.

Before loop total free memory: 64,909 ::

After loop total free memory: 64,775 ::

with Clear approach,

Before loop total free memory: 64,909 :: After loop total free memory: 64,765 ::

So this says there is not much difference in using arraylist.clear from memory utilization perspective.

What does the restrict keyword mean in C++?

Since header files from some C libraries use the keyword, the C++ language will have to do something about it.. at the minimum, ignoring the keyword, so we don't have to #define the keyword to a blank macro to suppress the keyword.

How to tell if UIViewController's view is visible

You want to use the UITabBarController's selectedViewController property. All view controllers attached to a tab bar controller have a tabBarController property set, so you can, from within any of the view controllers' code:

if([[[self tabBarController] selectedViewController] isEqual:self]){
     //we're in the active controller
}else{
     //we are not
}

CSS: Set a background color which is 50% of the width of the window

This is an example that will work on most browsers.
Basically you use two background colors, the first one starting from 0% and ending at 50% and the second one starting from 51% and ending at 100%

I'm using horizontal orientation:

background: #000000;
background: -moz-linear-gradient(left,  #000000 0%, #000000 50%, #ffffff 51%, #ffffff 100%);
background: -webkit-gradient(linear, left top, right top, color-stop(0%,#000000), color-stop(50%,#000000), color-stop(51%,#ffffff), color-stop(100%,#ffffff));
background: -webkit-linear-gradient(left,  #000000 0%,#000000 50%,#ffffff 51%,#ffffff 100%);
background: -o-linear-gradient(left,  #000000 0%,#000000 50%,#ffffff 51%,#ffffff 100%);
background: -ms-linear-gradient(left,  #000000 0%,#000000 50%,#ffffff 51%,#ffffff 100%);
background: linear-gradient(to right,  #000000 0%,#000000 50%,#ffffff 51%,#ffffff 100%);
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#000000', endColorstr='#ffffff',GradientType=1 );

For different adjustments you could use http://www.colorzilla.com/gradient-editor/

Implement paging (skip / take) functionality with this query

In order to do this in SQL Server, you must order the query by a column, so you can specify the rows you want.

Example:

select * from table order by [some_column] 
offset 10 rows
FETCH NEXT 10 rows only

And you can't use the "TOP" keyword when doing this.

You can learn more here: https://technet.microsoft.com/pt-br/library/gg699618%28v=sql.110%29.aspx

Installing lxml module in python

Just do:

sudo apt-get install python-lxml

For Python 2 (e.g., required by Inkscape):

sudo apt-get install python2-lxml

If you are planning to install from source, then albertov's answer will help. But unless there is a reason, don't, just install it from the repository.

How to load a controller from another controller in codeigniter?

you cannot call a controller method from another controller directly

my solution is to use inheritances and extend your controller from the library controller

class Controller1 extends CI_Controller {

    public function index() {
        // some codes here
    }

    public function methodA(){
        // code here
    }
}

in your controller we call it Mycontoller it will extends Controller1

include_once (dirname(__FILE__) . "/controller1.php");

class Mycontroller extends Controller1 {

    public function __construct() {
        parent::__construct();
    }

    public function methodB(){
        // codes....
    }
}

and you can call methodA from mycontroller

http://example.com/mycontroller/methodA

http://example.com/mycontroller/methodB

this solution worked for me

jquery how to get the page's current screen top position?

var top = $('html').offset().top;

should do it.

edit: this is the negative of $(document).scrollTop()

Access restriction: Is not accessible due to restriction on required library ..\jre\lib\rt.jar

i've solved this issue with these steps: expand your project, right click "JRE System Library" > Properties > choose 3rd option "Workspace default JRE" > OK . Hope it help you too