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Remove columns from DataTable in C#

Aside from limiting the columns selected to reduce bandwidth and memory:

DataTable t;

What datatype should be used for storing phone numbers in SQL Server 2005?

Normalise the data then store as a varchar. Normalising could be tricky.

That should be a one-time hit. Then as a new record comes in, you're comparing it to normalised data. Should be very fast.

Is there a PowerShell "string does not contain" cmdlet or syntax?

If $arrayofStringsNotInterestedIn is an [array] you should use -notcontains:

Get-Content $FileName | foreach-object { `
   if ($arrayofStringsNotInterestedIn -notcontains $_) { $) }

or better (IMO)

Get-Content $FileName | where { $arrayofStringsNotInterestedIn -notcontains $_}

Any tools to generate an XSD schema from an XML instance document?

You can use an open source and cross-platform option: inst2xsd from Apache's XMLBeans. I find it very useful and easy.

Just download, unzip and play (it requires Java).

Bash or KornShell (ksh)?

I'm a korn-shell veteran, so know that I speak from that perspective.

However, I have been comfortable with Bourne shell, ksh88, and ksh93, and for the most I know which features are supported in which. (I should skip ksh88 here, as it's not widely distributed anymore.)

For interactive use, take whatever fits your need. Experiment. I like being able to use the same shell for interactive use and for programming.

I went from ksh88 on SVR2 to tcsh, to ksh88sun (which added significant internationalisation support) and ksh93. I tried bash, and hated it because it flattened my history. Then I discovered shopt -s lithist and all was well. (The lithist option assures that newlines are preserved in your command history.)

For shell programming, I'd seriously recommend ksh93 if you want a consistent programming language, good POSIX conformance, and good performance, as many common unix commands can be available as builtin functions.

If you want portability use at least both. And make sure you have a good test suite.

There are many subtle differences between shells. Consider for example reading from a pipe:

b=42 && echo one two three four |
    read a b junk && echo $b

This will produce different results in different shells. The korn-shell runs pipelines from back to front; the last element in the pipeline runs in the current process. Bash did not support this useful behaviour until v4.x, and even then, it's not the default.

Another example illustrating consistency: The echo command itself, which was made obsolete by the split between BSD and SYSV unix, and each introduced their own convention for not printing newlines (and other behaviour). The result of this can still be seen in many 'configure' scripts.

Ksh took a radical approach to that - and introduced the print command, which actually supports both methods (the -n option from BSD, and the trailing \c special character from SYSV)

However, for serious systems programming I'd recommend something other than a shell, like python, perl. Or take it a step further, and use a platform like puppet - which allows you to watch and correct the state of whole clusters of systems, with good auditing.

Shell programming is like swimming in uncharted waters, or worse.

Programming in any language requires familiarity with its syntax, its interfaces and behaviour. Shell programming isn't any different.

How to run a script as root on Mac OS X?

As in any unix-based environment, you can use the sudo command:

$ sudo script-name

It will ask for your password (your own, not a separate root password).

How do I check CPU and Memory Usage in Java?

The YourKit Java profiler is an excellent commercial solution. You can find further information in the docs on CPU profiling and memory profiling.

How do you force a CIFS connection to unmount

A lazy unmount will do the job for you.

umount -l <mount path>

How to convert DateTime to VarChar


How to do INSERT into a table records extracted from another table

inserting data form one table to another table in different DATABASE

insert into DocTypeGroup 
    Select DocGrp_Id,DocGrp_SubId,DocGrp_GroupName,DocGrp_PM,DocGrp_DocType 
    from Opendatasource( 'SQLOLEDB','Data Source=;UserID=sa;Password=gchaturthi').dbIPFMCI.dbo.DocTypeGroup

How to convert numbers between hexadecimal and decimal

This is not really easiest way but this source code enable you to right any types of octal number i.e 23.214, 23 and 0.512 and so on. Hope this will help you..

    public string octal_to_decimal(string m_value)
        double i, j, x = 0;
        Int64 main_value;
        int k = 0;
        bool pw = true, ch;
        int position_pt = m_value.IndexOf(".");
        if (position_pt == -1)
            main_value = Convert.ToInt64(m_value);
            ch = false;
            main_value = Convert.ToInt64(m_value.Remove(position_pt, m_value.Length - position_pt));
            ch = true;

        while (k <= 1)
                i = main_value % 10;                                        // Return Remainder
                i = i * Convert.ToDouble(Math.Pow(8, x));                   // calculate power
                if (pw)
                o_to_d = o_to_d + i;                                        // Saving Required calculated value in main variable
                main_value = main_value / 10;                               // Dividing the main value 
            while (main_value >= 1);
            if (ch)
                main_value = Convert.ToInt64(Reversestring(m_value.Remove(0, position_pt + 1)));
                k = 2;
            pw = false;
            x = -1;
        return (Convert.ToString(o_to_d));

What is the difference between explicit and implicit cursors in Oracle?

An implicit cursor is one created "automatically" for you by Oracle when you execute a query. It is simpler to code, but suffers from

  • inefficiency (the ANSI standard specifies that it must fetch twice to check if there is more than one record)
  • vulnerability to data errors (if you ever get two rows, it raises a TOO_MANY_ROWS exception)


SELECT col INTO var FROM table WHERE something;

An explicit cursor is one you create yourself. It takes more code, but gives more control - for example, you can just open-fetch-close if you only want the first record and don't care if there are others.


  CURSOR cur IS SELECT col FROM table WHERE something; 
  OPEN cur;
  FETCH cur INTO var;
  CLOSE cur;

Dropdownlist width in IE

Its tested in all version of IE, Chrome, FF & Safari

JavaScript code:

<!-- begin hiding
function expandSELECT(sel) { = '';

function contractSELECT(sel) { = '100px';
// end hiding -->

Html code:

<select name="sideeffect" id="sideeffect"  style="width:100px;" onfocus="expandSELECT(this);" onblur="contractSELECT(this);" >
  <option value="0" selected="selected" readonly="readonly">Select</option>
  <option value="1" >Apple</option>
  <option value="2" >Orange + Banana + Grapes</option>

String vs. StringBuilder

String and StringBuilder are actually both immutable, the StringBuilder has built in buffers which allow its size to be managed more efficiently. When the StringBuilder needs to resize is when it is re-allocated on the heap. By default it is sized to 16 characters, you can set this in the constructor.


StringBuilder sb = new StringBuilder(50);

Iterating through all the cells in Excel VBA or VSTO 2005

There are several methods to accomplish this, each of which has advantages and disadvantages; First and foremost, you're going to need to have an instance of a Worksheet object, Application.ActiveSheet works if you just want the one the user is looking at.

The Worksheet object has three properties that can be used to access cell data (Cells, Rows, Columns) and a method that can be used to obtain a block of cell data, (get_Range).

Ranges can be resized and such, but you may need to use the properties mentioned above to find out where the boundaries of your data are. The advantage to a Range becomes apparent when you are working with large amounts of data because VSTO add-ins are hosted outside the boundaries of the Excel application itself, so all calls to Excel have to be passed through a layer with overhead; obtaining a Range allows you to get/set all of the data you want in one call which can have huge performance benefits, but it requires you to use explicit details rather than iterating through each entry.

This MSDN forum post shows a VB.Net developer asking a question about getting the results of a Range as an array

What is the dual table in Oracle?

It is a dummy table with one element in it. It is useful because Oracle doesn't allow statements like


You can work around this restriction by writing



How can I start an interactive console for Perl?

I use the command line as a console:

$ perl -e 'print "JAPH\n"'

Then I can use my bash history to get back old commands. This does not preserve state, however.

This form is most useful when you want to test "one little thing" (like when answering Perl questions). Often, I find these commands get scraped verbatim into a shell script or makefile.

How to terminate a Python script

In Python 3.5, I tried to incorporate similar code without use of modules (e.g. sys, Biopy) other than what's built-in to stop the script and print an error message to my users. Here's my example:

## My example:
if "ATG" in my_DNA: 
    ## <Do something & proceed...>
    print("Start codon is missing! Check your DNA sequence!")
    exit() ## as most folks said above

Later on, I found it is more succinct to just throw an error:

## My example revised:
if "ATG" in my_DNA: 
    ## <Do something & proceed...>
    raise ValueError("Start codon is missing! Check your DNA sequence!")

How to duplicate a whole line in Vim?

1 gotcha: when you use "p" to put the line, it puts it after the line your cursor is on, so if you want to add the line after the line you're yanking, don't move the cursor down a line before putting the new line.

How do I sort a list of dictionaries by a value of the dictionary?

import operator

'key' is used to sort by an arbitrary value and 'itemgetter' sets that value to each item's 'name' attribute.

How to do relative imports in Python?

From Python doc,

In Python 2.5, you can switch import‘s behaviour to absolute imports using a from __future__ import absolute_import directive. This absolute- import behaviour will become the default in a future version (probably Python 2.7). Once absolute imports are the default, import string will always find the standard library’s version. It’s suggested that users should begin using absolute imports as much as possible, so it’s preferable to begin writing from pkg import string in your code

How do I capitalize first letter of first name and last name in C#?

CultureInfo.CurrentCulture.TextInfo.ToTitleCase ("my name");

returns ~ My Name

But the problem still exists with names like McFly as stated earlier.

How do you detect Credit card type based on number?

Do not try to detect credit card type as part of processing a payment. You are risking of declining valid transactions.

If you need to provide information to your payment processor (e.g. PayPal credit card object requires to name the card type), then guess it from the least information available, e.g.

$credit_card['pan'] = preg_replace('/[^0-9]/', '', $credit_card['pan']);
$inn = (int) mb_substr($credit_card['pan'], 0, 2);

// @see
if ($inn >= 40 && $inn <= 49) {
    $type = 'visa';
} else if ($inn >= 51 && $inn <= 55) {
    $type = 'mastercard';
} else if ($inn >= 60 && $inn <= 65) {
    $type = 'discover';
} else if ($inn >= 34 && $inn <= 37) {
    $type = 'amex';
} else {
    throw new \UnexpectedValueException('Unsupported card type.');

This implementation (using only the first two digits) is enough to identify all of the major (and in PayPal's case all of the supported) card schemes. In fact, you might want to skip the exception altogether and default to the most popular card type. Let the payment gateway/processor tell you if there is a validation error in response to your request.

The reality is that your payment gateway does not care about the value you provide.

Accessing Websites through a Different Port?

when viewing a website it gets assigned a random port, it will always come from port 80 (usually always, unless the server admin has changed the port) there's no way for someone to change that port unless you have control of the server.

How often should Oracle database statistics be run?

Whenever the data changes "significantly".

If a table goes from 1 row to 200 rows, that's a significant change. When a table goes from 100,000 rows to 150,000 rows, that's not a terribly significant change. When a table goes from 1000 rows all with identical values in commonly-queried column X to 1000 rows with nearly unique values in column X, that's a significant change.

Statistics store information about item counts and relative frequencies -- things that will let it "guess" at how many rows will match a given criteria. When it guesses wrong, the optimizer can pick a very suboptimal query plan.

How do I migrate an SVN repository with history to a new Git repository?

I´m on a windows machine and made a small Batch to transfer a SVN repo with history (but without branches) to a GIT repo by just calling


Perhaps anybody can use it. It creates a TMP-folder checks out the SVN repo there with git and adds the new origin and pushes it... and deletes the folder again.

@echo off 
SET TO=%2 
SET TMP=tmp_%random%

echo from:  %FROM% 
echo to:    %TO% 
echo tmp:   %TMP%


git svn clone  --no-metadata --authors-file=users.txt %FROM% %TMP%  
cd %TMP% 
git remote add origin %TO% 
git push --set-upstream origin master

cd .. 
echo delete %TMP% ... 

rmdir /s /q %TMP%

You still need the users.txt with your user-mappings like

User1 = User One <[email protected]>

Create Generic method constraining T to an Enum

I do have specific requirement where I required to use enum with text associated with enum value. For example when I use enum to specify error type it required to describe error details.

public static class XmlEnumExtension
    public static string ReadXmlEnumAttribute(this Enum value)
        if (value == null) throw new ArgumentNullException("value");
        var attribs = (XmlEnumAttribute[]) value.GetType().GetField(value.ToString()).GetCustomAttributes(typeof (XmlEnumAttribute), true);
        return attribs.Length > 0 ? attribs[0].Name : value.ToString();

    public static T ParseXmlEnumAttribute<T>(this string str)
        foreach (T item in Enum.GetValues(typeof(T)))
            var attribs = (XmlEnumAttribute[])item.GetType().GetField(item.ToString()).GetCustomAttributes(typeof(XmlEnumAttribute), true);
            if(attribs.Length > 0 && attribs[0].Name.Equals(str)) return item;
        return (T)Enum.Parse(typeof(T), str, true);

public enum MyEnum
    [XmlEnum("First Value")]
    [XmlEnum("Second Value")]

 static void Main()
    // Parsing from XmlEnum attribute
    var str = "Second Value";
    var me = str.ParseXmlEnumAttribute<MyEnum>();
    // Parsing without XmlEnum
    str = "Three";
    me = str.ParseXmlEnumAttribute<MyEnum>();
    me = MyEnum.One;

Is there a C++ gdb GUI for Linux?

I use DDD a lot, and it's pretty powerful once you learn to use it. One thing I would say is don't use it over X over the WAN because it seems to do a lot of unnecessary screen updates.

Also, if you're not mated to GDB and don't mind ponying up a little cash, then I would try TotalView. It has a bit of a steep learning curve (it could definitely be more intuitive), but it's the best C++ debugger I've ever used on any platform and can be extended to introspect your objects in custom ways (thus allowing you to view an STL list as an actual list of objects, and not a bunch of confusing internal data members, etc.)

How do I programmatically set the value of a select box element using JavaScript?

Suppose your form is named form1:

function selectValue(val)
  var lc = document.form1.leaveCode;
  for (i=0; i&lt;lc.length; i++)
    if (lc.options[i].value == val)
        lc.selectedIndex = i;

Is there an effective tool to convert C# code to Java code?

They don't convert directly, but it allows for interoperability between .NET and J2EE.

Deep cloning objects

Create an extension:

public static T Clone<T>(this T theObject)
    string jsonData = JsonConvert.SerializeObject(theObject);
    return JsonConvert.DeserializeObject<T>(jsonData);

And call it like this:

NewObject = OldObject.Clone();

How do you get a string from a MemoryStream?

byte[] array = Encoding.ASCII.GetBytes("MyTest1 - MyTest2");
MemoryStream streamItem = new MemoryStream(array);

// convert to string
StreamReader reader = new StreamReader(streamItem);
string text = reader.ReadToEnd();

Why doesn't Java offer operator overloading?

There are a lot of posts complaining about operator overloading.

I felt I had to clarify the "operator overloading" concepts, offering an alternative viewpoint on this concept.

#Code obfuscating?

This argument is a fallacy.

##Obfuscating is possible in all languages...

It is as easy to obfuscate code in C or Java through functions/methods as it is in C++ through operator overloads:

// C++
T operator + (const T & a, const T & b) // add ?
   T c ;
   c.value = a.value - b.value ; // subtract !!!
   return c ;

// Java
static T add (T a, T b) // add ?
   T c = new T() ;
   c.value = a.value - b.value ; // subtract !!!
   return c ;

/* C */
T add (T a, T b) /* add ? */
   T c ;
   c.value = a.value - b.value ; /* subtract !!! */
   return c ;

##...Even in Java's standard interfaces

For another example, let's see the Cloneable interface in Java:

You are supposed to clone the object implementing this interface. But you could lie. And create a different object. In fact, this interface is so weak you could return another type of object altogether, just for the fun of it:

class MySincereHandShake implements Cloneable
    public Object clone()
       return new MyVengefulKickInYourHead() ;

As the Cloneable interface can be abused/obfuscated, should it be banned on the same grounds C++ operator overloading is supposed to be?

We could overload the toString() method of a MyComplexNumber class to have it return the stringified hour of the day. Should the toString() overloading be banned, too? We could sabotage MyComplexNumber.equals to have it return a random value, modify the operands... etc. etc. etc..

In Java, as in C++, or whatever language, the programmer must respect a minimum of semantics when writing code. This means implementing a add function that adds, and Cloneable implementation method that clones, and a ++ operator than increments.

#What's obfuscating anyway?

Now that we know that code can be sabotaged even through the pristine Java methods, we can ask ourselves about the real use of operator overloading in C++?

##Clear and natural notation: methods vs. operator overloading?

We'll compare below, for different cases, the "same" code in Java and C++, to have an idea of which kind of coding style is clearer.

###Natural comparisons:

// C++ comparison for built-ins and user-defined types
bool    isEqual          = A == B ;
bool    isNotEqual       = A != B ;
bool    isLesser         = A <  B ;
bool    isLesserOrEqual  = A <= B ;

// Java comparison for user-defined types
boolean isEqual          = A.equals(B) ;
boolean isNotEqual       = ! A.equals(B) ;
boolean isLesser         = A.comparesTo(B) < 0 ;
boolean isLesserOrEqual  = A.comparesTo(B) <= 0 ;

Please note that A and B could be of any type in C++, as long as the operator overloads are provided. In Java, when A and B are not primitives, the code can become very confusing, even for primitive-like objects (BigInteger, etc.)...

###Natural array/container accessors and subscripting:

// C++ container accessors, more natural
value        = myArray[25] ;         // subscript operator
value        = myVector[25] ;        // subscript operator
value        = myString[25] ;        // subscript operator
value        = myMap["25"] ;         // subscript operator
myArray[25]  = value ;               // subscript operator
myVector[25] = value ;               // subscript operator
myString[25] = value ;               // subscript operator
myMap["25"]  = value ;               // subscript operator

// Java container accessors, each one has its special notation
value        = myArray[25] ;         // subscript operator
value        = myVector.get(25) ;    // method get
value        = myString.charAt(25) ; // method charAt
value        = myMap.get("25") ;     // method get
myArray[25]  = value ;               // subscript operator
myVector.set(25, value) ;            // method set
myMap.put("25", value) ;             // method put

In Java, we see that for each container to do the same thing (access its content through an index or identifier), we have a different way to do it, which is confusing.

In C++, each container uses the same way to access its content, thanks to operator overloading.

###Natural advanced types manipulation

The examples below use a Matrix object, found using the first links found on Google for "Java Matrix object" and "C++ Matrix object":

// C++ YMatrix matrix implementation on CodeProject
// A, B, C, D, E, F are Matrix objects;
E =  A * (B / 2) ;
E += (A - B) * (C + D) ;
F =  E ;                  // deep copy of the matrix

// Java JAMA matrix implementation (seriously...)
// A, B, C, D, E, F are Matrix objects;
E = A.times(B.times(0.5)) ;
E.plusEquals(A.minus(B).times( ;
F = E.copy() ;            // deep copy of the matrix

And this is not limited to matrices. The BigInteger and BigDecimal classes of Java suffer from the same confusing verbosity, whereas their equivalents in C++ are as clear as built-in types.

###Natural iterators:

// C++ Random Access iterators
++it ;                  // move to the next item
--it ;                  // move to the previous item
it += 5 ;               // move to the next 5th item (random access)
value = *it ;           // gets the value of the current item
*it = 3.1415 ;          // sets the value 3.1415 to the current item
(*it).foo() ;           // call method foo() of the current item

// Java ListIterator<E> "bi-directional" iterators
value = ;     // move to the next item & return the value
value = it.previous() ; // move to the previous item & return the value
it.set(3.1415) ;        // sets the value 3.1415 to the current item

###Natural functors:

// C++ Functors
myFunctorObject("Hello World", 42) ;

// Java Functors ???
myFunctorObject.execute("Hello World", 42) ;

###Text concatenation:

// C++ stream handling (with the << operator)
                    stringStream   << "Hello " << 25 << " World" ;
                    fileStream     << "Hello " << 25 << " World" ;
                    outputStream   << "Hello " << 25 << " World" ;
                    networkStream  << "Hello " << 25 << " World" ;
anythingThatOverloadsShiftOperator << "Hello " << 25 << " World" ;

// Java concatenation
myStringBuffer.append("Hello ").append(25).append(" World") ;

Ok, in Java you can use MyString = "Hello " + 25 + " World" ; too... But, wait a second: This is operator overloading, isn't it? Isn't it cheating???


##Generic code?

The same generic code modifying operands should be usable both for built-ins/primitives (which have no interfaces in Java), standard objects (which could not have the right interface), and user-defined objects.

For example, calculating the average value of two values of arbitrary types:

// C++ primitive/advanced types
template<typename T>
T getAverage(const T & p_lhs, const T & p_rhs)
   return (p_lhs + p_rhs) / 2 ;

int     intValue     = getAverage(25, 42) ;
double  doubleValue  = getAverage(25.25, 42.42) ;
complex complexValue = getAverage(cA, cB) ; // cA, cB are complex
Matrix  matrixValue  = getAverage(mA, mB) ; // mA, mB are Matrix

// Java primitive/advanced types
// It won't really work in Java, even with generics. Sorry.

#Discussing operator overloading

Now that we have seen fair comparisons between C++ code using operator overloading, and the same code in Java, we can now discuss "operator overloading" as a concept.

##Operator overloading existed since before computers

Even outside of computer science, there is operator overloading: For example, in mathematics, operators like +, -, *, etc. are overloaded.

Indeed, the signification of +, -, *, etc. changes depending on the types of the operands (numerics, vectors, quantum wave functions, matrices, etc.).

Most of us, as part of our science courses, learned multiple significations for operators, depending on the types of the operands. Did we find them confusing, them?

##Operator overloading depends on its operands

This is the most important part of operator overloading: Like in mathematics, or in physics, the operation depends on its operands' types.

So, know the type of the operand, and you will know the effect of the operation.

##Even C and Java have (hard-coded) operator overloading

In C, the real behavior of an operator will change according to its operands. For example, adding two integers is different than adding two doubles, or even one integer and one double. There is even the whole pointer arithmetic domain (without casting, you can add to a pointer an integer, but you cannot add two pointers...).

In Java, there is no pointer arithmetic, but someone still found string concatenation without the + operator would be ridiculous enough to justify an exception in the "operator overloading is evil" creed.

It's just that you, as a C (for historical reasons) or Java (for personal reasons, see below) coder, you can't provide your own.

##In C++, operator overloading is not optional...

In C++, operator overloading for built-in types is not possible (and this is a good thing), but user-defined types can have user-defined operator overloads.

As already said earlier, in C++, and to the contrary to Java, user-types are not considered second-class citizens of the language, when compared to built-in types. So, if built-in types have operators, user types should be able to have them, too.

The truth is that, like the toString(), clone(), equals() methods are for Java (i.e. quasi-standard-like), C++ operator overloading is so much part of C++ that it becomes as natural as the original C operators, or the before mentioned Java methods.

Combined with template programming, operator overloading becomes a well known design pattern. In fact, you cannot go very far in STL without using overloaded operators, and overloading operators for your own class.

##...but it should not be abused

Operator overloading should strive to respect the semantics of the operator. Do not subtract in a + operator (as in "do not subtract in a add function", or "return crap in a clone method").

Cast overloading can be very dangerous because they can lead to ambiguities. So they should really be reserved for well defined cases. As for && and ||, do not ever overload them unless you really know what you're doing, as you'll lose the the short circuit evaluation that the native operators && and || enjoy.

#So... Ok... Then why it is not possible in Java?

Because James Gosling said so:

I left out operator overloading as a fairly personal choice because I had seen too many people abuse it in C++.

James Gosling. Source:

Please compare Gosling's text above with Stroustrup's below:

Many C++ design decisions have their roots in my dislike for forcing people to do things in some particular way [...] Often, I was tempted to outlaw a feature I personally disliked, I refrained from doing so because I did not think I had the right to force my views on others.

Bjarne Stroustrup. Source: The Design and Evolution of C++ (1.3 General Background)

##Would operator overloading benefit Java?

Some objects would greatly benefit from operator overloading (concrete or numerical types, like BigDecimal, complex numbers, matrices, containers, iterators, comparators, parsers etc.).

In C++, you can profit from this benefit because of Stroustrup's humility. In Java, you're simply screwed because of Gosling's personal choice.

##Could it be added to Java?

The reasons for not adding operator overloading now in Java could be a mix of internal politics, allergy to the feature, distrust of developers (you know, the saboteur ones that seem to haunt Java teams...), compatibility with the previous JVMs, time to write a correct specification, etc..

So don't hold your breath waiting for this feature...

##But they do it in C#!!!


While this is far from being the only difference between the two languages, this one never fails to amuse me.

Apparently, the C# folks, with their "every primitive is a struct, and a struct derives from Object", got it right at first try.

##And they do it in other languages!!!

Despite all the FUD against used defined operator overloading, the following languages support it: Kotlin, Scala, Dart, Python, F#, C#, D, Algol 68, Smalltalk, Groovy, Perl 6, C++, Ruby, Haskell, MATLAB, Eiffel, Lua, Clojure, Fortran 90, Swift, Ada, Delphi 2005...

So many languages, with so many different (and sometimes opposing) philosophies, and yet they all agree on that point.

Food for thought...

How do you run CMD.exe under the Local System Account?

I would recommend you work out the minimum permission set that your service really needs and use that, rather than the far too privileged Local System context. For example, Local Service.

Interactive services no longer work - or at least, no longer show UI - on Windows Vista and Windows Server 2008 due to session 0 isolation.

How to access the last value in a vector?

I use the tail function:

tail(vector, n=1)

The nice thing with tail is that it works on dataframes too, unlike the x[length(x)] idiom.

When to throw an exception?

If it's code running inside a loop that will likely cause an exception over and over again, then throwing exceptions is not a good thing, because they are pretty slow for large N. But there is nothing wrong with throwing custom exceptions if the performance is not an issue. Just make sure that you have a base exception that they all inherite, called BaseException or something like that. BaseException inherits System.Exception, but all of your exceptions inherit BaseException. You can even have a tree of Exception types to group similar types, but this may or may not be overkill.

So, the short answer is that if it doesn't cause a significant performance penalty (which it should not unless you are throwing a lot of exceptions), then go ahead.

How to automatically generate a stacktrace when my program crashes

Ive been looking at this problem for a while.

And buried deep in the Google Performance Tools README

talks about libunwind

Would love to hear opinions of this library.

The problem with -rdynamic is that it can increase the size of the binary relatively significantly in some cases

How to get progress from XMLHttpRequest

For the bytes uploaded it is quite easy. Just monitor the xhr.upload.onprogress event. The browser knows the size of the files it has to upload and the size of the uploaded data, so it can provide the progress info.

For the bytes downloaded (when getting the info with xhr.responseText), it is a little bit more difficult, because the browser doesn't know how many bytes will be sent in the server request. The only thing that the browser knows in this case is the size of the bytes it is receiving.

There is a solution for this, it's sufficient to set a Content-Length header on the server script, in order to get the total size of the bytes the browser is going to receive.

For more go to .

Example: My server script reads a zip file (it takes 5 seconds):


header("Content-Length: " . $filesize); // set header length
// if the headers is not set then the evt.loaded will be 0
exit 0;

Now I can monitor the download process of the server script, because I know it's total length:

function updateProgress(evt) 
   if (evt.lengthComputable) 
   {  // evt.loaded the bytes the browser received
      // the total bytes set by the header
      // jQuery UI progress bar to show the progress on screen
     var percentComplete = (evt.loaded / * 100;  
     $('#progressbar').progressbar( "option", "value", percentComplete );
function sendreq(evt) 
    var req = new XMLHttpRequest(); 
    req.onprogress = updateProgress;'GET', 'test.php', true);  
    req.onreadystatechange = function (aEvt) {  
        if (req.readyState == 4) 
             //run any callback here

General guidelines to avoid memory leaks in C++

You'll want to look at smart pointers, such as boost's smart pointers.

Instead of

int main()
    Object* obj = new Object();
    delete obj;

boost::shared_ptr will automatically delete once the reference count is zero:

int main()
    boost::shared_ptr<Object> obj(new Object());
    // destructor destroys when reference count is zero

Note my last note, "when reference count is zero, which is the coolest part. So If you have multiple users of your object, you won't have to keep track of whether the object is still in use. Once nobody refers to your shared pointer, it gets destroyed.

This is not a panacea, however. Though you can access the base pointer, you wouldn't want to pass it to a 3rd party API unless you were confident with what it was doing. Lots of times, your "posting" stuff to some other thread for work to be done AFTER the creating scope is finished. This is common with PostThreadMessage in Win32:

void foo()
   boost::shared_ptr<Object> obj(new Object()); 

   // Simplified here
   PostThreadMessage(...., (LPARAM)ob.get());
   // Destructor destroys! pointer sent to PostThreadMessage is invalid! Zohnoes!

As always, use your thinking cap with any tool...

SOAP or REST for Web Services?

In sense with "PHP-universe" PHP support for any advanced SOAP sucks big time. You will end up using something like as soon as you cross the basic needs, even to enable WS-Security or WS-RM no inbuilt support.

SOAP envelope creation I feel is lot messy in PHP, the way it creates namespaces, xsd:nil, xsd:anytype and old styled soap Services which use SOAP Encoding (God knows how's that different) with in SOAP messages.

Avoid all this mess by sticking to REST, REST is nothing really big we have been using it since the start of WWW. We realized only when this paper came out it shows how can we use HTTP capabilities to implement RESTFul Services. HTTP is inherently REST, that doesn't mean just using HTTP makes your services RESTFul.

SOAP neglects the core capabilities of HTTP and considers HTTP just as an transport protocol, hence it is transport protocol independent in theory (in practical it's not the case have you heard of SOAP Action header? if not google it now!).

With JSON adaption increasing and HTML5 with javascript maturing REST with JSON has become the most common way of dealing with services. JSON Schema has also been defined can be used for enterprise level solutions (still in early stages) along with WADL if needed.

PHP support for REST and JSON is definitely better than existing inbuilt SOAP support it has.

Adding few more BUZZ words here SOA, WOA, ROA

by the way I do love SOAP especially for the WS-Security spec, this is one good spec and if someone thinking in Enterprise JSON adaption definetly need to come with some thing similar for JSON, like field level encryption etc.

Change the color of a bullet in a html list?

You could use CSS to attain this. By specifying the list in the color and style of your choice, you can then also specify the text as a different color.

Follow the example at

Using MySQL with Entity Framework

If you interested in running Entity Framework with MySql on mono/linux/macos, this might be helpful

How can I open Java .class files in a human-readable way?

If you don't mind reading bytecode, javap should work fine. It's part of the standard JDK installation.

Usage: javap <options> <classes>...

where options include:
   -c                        Disassemble the code
   -classpath <pathlist>     Specify where to find user class files
   -extdirs <dirs>           Override location of installed extensions
   -help                     Print this usage message
   -J<flag>                  Pass <flag> directly to the runtime system
   -l                        Print line number and local variable tables
   -public                   Show only public classes and members
   -protected                Show protected/public classes and members
   -package                  Show package/protected/public classes
                             and members (default)
   -private                  Show all classes and members
   -s                        Print internal type signatures
   -bootclasspath <pathlist> Override location of class files loaded
                             by the bootstrap class loader
   -verbose                  Print stack size, number of locals and args for methods
                             If verifying, print reasons for failure

How can I delete a service in Windows?

If they are .NET created services you can use the installutil.exe with the /u switch its in the .net framework folder like C:\Windows\Microsoft.NET\Framework64\v2.0.50727

When are you supposed to use escape instead of encodeURI / encodeURIComponent?

Also remember that they all encode different sets of characters, and select the one you need appropriately. encodeURI() encodes fewer characters than encodeURIComponent(), which encodes fewer (and also different, to dannyp's point) characters than escape().

How to implement Enums in Ruby?

The most idiomatic way to do this is to use symbols. For example, instead of:

enum {

myFunc(FOO); can just use symbols:

# You don't actually need to declare these, of course--this is
# just to show you what symbols look like.


This is a bit more open-ended than enums, but it fits well with the Ruby spirit.

Symbols also perform very well. Comparing two symbols for equality, for example, is much faster than comparing two strings.

How do I check to see if a value is an integer in MySQL?

Suppose we have column with alphanumeric field having entries like


and you want highest numeric value from this db column (in this case it is 9582) then this query will help you

SELECT Max(column_name) from table_name where column_name REGEXP '^[0-9]+$'

Converting a Uniform Distribution to a Normal Distribution

function distRandom(){
  return x;

How do I dump the data of some SQLite3 tables?

Not the best way, but at lease does not need external tools (except grep, which is standard on *nix boxes anyway)

sqlite3 database.db3 .dump | grep '^INSERT INTO "tablename"'

but you do need to do this command for each table you are looking for though.

Note that this does not include schema.

Best way to convert pdf files to tiff files

Disclaimer: work for product I am recommending

Atalasoft has a .NET library that can convert PDF to TIFF -- we are a partner of FOXIT, so the PDF rendering is very good.

What are the uses of "using" in C#?

using can be used to call IDisposable. It can also be used to alias types.

using (SqlConnection cnn = new SqlConnection()) { /*code*/}
using f1 = System.Windows.Forms.Form;

Getting all types in a namespace via reflection

As FlySwat says, you can have the same namespace spanning in multiple assemblies (for eg System.Collections.Generic). You will have to load all those assemblies if they are not already loaded. So for a complete answer:

                       .SelectMany(t => t.GetTypes())
                       .Where(t => t.IsClass && t.Namespace == @namespace)

This should work unless you want classes of other domains. To get a list of all domains, follow this link.

Which is the best Linux C/C++ debugger (or front-end to gdb) to help teaching programming?

Perhaps it is indirect to gdb (because it's an IDE), but my recommendations would be KDevelop. Being quite spoiled with Visual Studio's debugger (professionally at work for many years), I've so far felt the most comfortable debugging in KDevelop (as hobby at home, because I could not afford Visual Studio for personal use - until Express Edition came out). It does "look something similar to" Visual Studio compared to other IDE's I've experimented with (including Eclipse CDT) when it comes to debugging step-through, step-in, etc (placing break points is a bit awkward because I don't like to use mouse too much when coding, but it's not difficult).

How to vertically align elements in a div?

#3 ways to make center child div in a parent div

  • Absolute Positioning Method
  • Flexbox Method
  • Transform/Translate Method

    enter image description here


/* 1st way */_x000D_
.parent1 {_x000D_
  background: darkcyan;_x000D_
   width: 200px;_x000D_
   height: 200px;_x000D_
   position: relative;_x000D_
.child1 {_x000D_
  background: white;_x000D_
  height: 30px;_x000D_
  width: 30px;_x000D_
  position: absolute;_x000D_
  top: 50%;_x000D_
  left: 50%;_x000D_
  margin: -15px;_x000D_
/* 2nd way */_x000D_
.parent2 {_x000D_
  display: flex;_x000D_
  justify-content: center;_x000D_
  align-items: center;_x000D_
  background: darkcyan;_x000D_
  height: 200px;_x000D_
  width: 200px;_x000D_
.child2 {_x000D_
  background: white;_x000D_
  height: 30px;_x000D_
  width: 30px;_x000D_
/* 3rd way */_x000D_
.parent3 {_x000D_
  position: relative;_x000D_
  height: 200px;_x000D_
  width: 200px;_x000D_
  background: darkcyan;_x000D_
.child3 {_x000D_
  background: white;_x000D_
  height: 30px;_x000D_
  width: 30px;_x000D_
  position: absolute;_x000D_
  top: 50%;_x000D_
  left: 50%;_x000D_
  transform: translate(-50%, -50%);_x000D_
<div class="parent1">_x000D_
  <div class="child1"></div>_x000D_
<hr />_x000D_
<div class="parent2">_x000D_
  <div class="child2"></div>_x000D_
<hr />_x000D_
<div class="parent3">_x000D_
  <div class="child3"></div>_x000D_

How to get the file path from HTML input form in Firefox 3

Simply you cannot do it with FF3.

The other option could be using applet or other controls to select and upload files.

How do the PHP equality (== double equals) and identity (=== triple equals) comparison operators differ?

In regards to JavaScript:

The === operator works the same as the == operator, but it requires that its operands have not only the same value, but also the same data type.

For example, the sample below will display 'x and y are equal', but not 'x and y are identical'.

var x = 4;
var y = '4';
if (x == y) {
    alert('x and y are equal');
if (x === y) {
    alert('x and y are identical');

How can I concatenate two arrays in Java?

If you use this way so you no need to import any third party class.

If you want concatenate String

Sample code for concate two String Array

public static String[] combineString(String[] first, String[] second){
        int length = first.length + second.length;
        String[] result = new String[length];
        System.arraycopy(first, 0, result, 0, first.length);
        System.arraycopy(second, 0, result, first.length, second.length);
        return result;

If you want concatenate Int

Sample code for concate two Integer Array

public static int[] combineInt(int[] a, int[] b){
        int length = a.length + b.length;
        int[] result = new int[length];
        System.arraycopy(a, 0, result, 0, a.length);
        System.arraycopy(b, 0, result, a.length, b.length);
        return result;

Here is Main method

    public static void main(String[] args) {

            String [] first = {"a", "b", "c"};
            String [] second = {"d", "e"};

            String [] joined = combineString(first, second);
            System.out.println("concatenated String array : " + Arrays.toString(joined));

            int[] array1 = {101,102,103,104};
            int[] array2 = {105,106,107,108};
            int[] concatenateInt = combineInt(array1, array2);

            System.out.println("concatenated Int array : " + Arrays.toString(concatenateInt));


We can use this way also.

How to match all occurrences of a regex

if you have a regexp with groups:

str="A 54mpl3 string w1th 7 numbers scatter3r ar0und"

you can use String's scan method to find matching groups:

str.scan re
#> [["54"], ["1"], ["3"]]

To find the matching pattern:

str.to_enum(:scan,re).map {$&}
#> ["54m", "1t", "3r"]

How to Truncate a string in PHP to the word closest to a certain number of characters?

I would use the preg_match function to do this, as what you want is a pretty simple expression.

$matches = array();
$result = preg_match("/^(.{1,199})[\s]/i", $text, $matches);

The expression means "match any substring starting from the beginning of length 1-200 that ends with a space." The result is in $result, and the match is in $matches. That takes care of your original question, which is specifically ending on any space. If you want to make it end on newlines, change the regular expression to:

$result = preg_match("/^(.{1,199})[\n]/i", $text, $matches);

Visual Studio opens the default browser instead of Internet Explorer

Right-click on an aspx file and choose 'browse with'. I think there's an option there to set as default.

What and where are the stack and heap?

What is a stack?

A stack is a pile of objects, typically one that is neatly arranged.

Enter image description here

Stacks in computing architectures are regions of memory where data is added or removed in a last-in-first-out manner.
In a multi-threaded application, each thread will have its own stack.

What is a heap?

A heap is an untidy collection of things piled up haphazardly.

Enter image description here

In computing architectures the heap is an area of dynamically-allocated memory that is managed automatically by the operating system or the memory manager library.
Memory on the heap is allocated, deallocated, and resized regularly during program execution, and this can lead to a problem called fragmentation.
Fragmentation occurs when memory objects are allocated with small spaces in between that are too small to hold additional memory objects.
The net result is a percentage of the heap space that is not usable for further memory allocations.

Both together

In a multi-threaded application, each thread will have its own stack. But, all the different threads will share the heap.
Because the different threads share the heap in a multi-threaded application, this also means that there has to be some coordination between the threads so that they don’t try to access and manipulate the same piece(s) of memory in the heap at the same time.

Which is faster – the stack or the heap? And why?

The stack is much faster than the heap.
This is because of the way that memory is allocated on the stack.
Allocating memory on the stack is as simple as moving the stack pointer up.

For people new to programming, it’s probably a good idea to use the stack since it’s easier.
Because the stack is small, you would want to use it when you know exactly how much memory you will need for your data, or if you know the size of your data is very small.
It’s better to use the heap when you know that you will need a lot of memory for your data, or you just are not sure how much memory you will need (like with a dynamic array).

Java Memory Model

Enter image description here

The stack is the area of memory where local variables (including method parameters) are stored. When it comes to object variables, these are merely references (pointers) to the actual objects on the heap.
Every time an object is instantiated, a chunk of heap memory is set aside to hold the data (state) of that object. Since objects can contain other objects, some of this data can in fact hold references to those nested objects.

How to convert local time string to UTC?

First, parse the string into a naive datetime object. This is an instance of datetime.datetime with no attached timezone information. See its documentation.

Use the pytz module, which comes with a full list of time zones + UTC. Figure out what the local timezone is, construct a timezone object from it, and manipulate and attach it to the naive datetime.

Finally, use datetime.astimezone() method to convert the datetime to UTC.

Source code, using local timezone "America/Los_Angeles", for the string "2001-2-3 10:11:12":

from datetime import datetime   
import pytz

local = pytz.timezone("America/Los_Angeles")
naive = datetime.strptime("2001-2-3 10:11:12", "%Y-%m-%d %H:%M:%S")
local_dt = local.localize(naive, is_dst=None)
utc_dt = local_dt.astimezone(pytz.utc)

From there, you can use the strftime() method to format the UTC datetime as needed:

utc_dt.strftime("%Y-%m-%d %H:%M:%S")

A regex for version number parsing

This might work:


At the top level, "*" is a special case of a valid version number. Otherwise, it starts with a number. Then there are zero, one, or two ".nn" sequences, followed by an optional ".*". This regex would accept 1.2.3.* which may or may not be permitted in your application.

The code for retrieving the matched sequences, especially the (\.\d+){0,2} part, will depend on your particular regex library.

Is it possible to print a variable's type in standard C++?

#include <iostream>
#include <typeinfo>
using namespace std;
#define show_type_name(_t) \
    system(("echo " + string(typeid(_t).name()) + " | c++filt -t").c_str())

int main() {
    auto a = {"one", "two", "three"};
    cout << "Type of a: " << typeid(a).name() << endl;
    cout << "Real type of a:\n";
    for (auto s : a) {
        if (string(s) == "one") {
            cout << "Type of s: " << typeid(s).name() << endl;
            cout << "Real type of s:\n";
        cout << s << endl;

    int i = 5;
    cout << "Type of i: " << typeid(i).name() << endl;
    cout << "Real type of i:\n";
    return 0;


Type of a: St16initializer_listIPKcE
Real type of a:
std::initializer_list<char const*>
Type of s: PKc
Real type of s:
char const*
Type of i: i
Real type of i:

How do I kill a VMware virtual machine that won't die?

If you are using Windows, the virtual machine should have it's own process that is visible in task manager. Use sysinternals Process Explorer to find the right one and then kill it from there.

Where do I find the current C or C++ standard documents?

The actual standards documents may not be the most useful. Most compilers do not fully implement the standards and may sometimes actually conflict. So the compiler documentation that you would already have will be more useful. Additionally, the documentation will contain platform-specific remarks and notes on any caveats.

What IDE to use for Python?


Spreadsheet version

spreadsheet screenshot

Alternatively, in plain text: (also available as a a screenshot)

                         Bracket Matching -.  .- Line Numbering
                          Smart Indent -.  |  |  .- UML Editing / Viewing
         Source Control Integration -.  |  |  |  |  .- Code Folding
                    Error Markup -.  |  |  |  |  |  |  .- Code Templates
  Integrated Python Debugging -.  |  |  |  |  |  |  |  |  .- Unit Testing
    Multi-Language Support -.  |  |  |  |  |  |  |  |  |  |  .- GUI Designer (Qt, Eric, etc)
   Auto Code Completion -.  |  |  |  |  |  |  |  |  |  |  |  |  .- Integrated DB Support
     Commercial/Free -.  |  |  |  |  |  |  |  |  |  |  |  |  |  |  .- Refactoring
   Cross Platform -.  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |     
Atom              |Y |F |Y |Y*|Y |Y |Y |Y |Y |Y |  |Y |Y |  |  |  |  |*many plugins
Editra            |Y |F |Y |Y |  |  |Y |Y |Y |Y |  |Y |  |  |  |  |  |
Emacs             |Y |F |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |  |  |  |
Eric Ide          |Y |F |Y |  |Y |Y |  |Y |  |Y |  |Y |  |Y |  |  |  |
Geany             |Y |F |Y*|Y |  |  |  |Y |Y |Y |  |Y |  |  |  |  |  |*very limited
Gedit             |Y |F |Y¹|Y |  |  |  |Y |Y |Y |  |  |Y²|  |  |  |  |¹with plugin; ²sort of
Idle              |Y |F |Y |  |Y |  |  |Y |Y |  |  |  |  |  |  |  |  |
IntelliJ          |Y |CF|Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |
JEdit             |Y |F |  |Y |  |  |  |  |Y |Y |  |Y |  |  |  |  |  |
KDevelop          |Y |F |Y*|Y |  |  |Y |Y |Y |Y |  |Y |  |  |  |  |  |*no type inference
Komodo            |Y |CF|Y |Y |Y |Y |Y |Y |Y |Y |  |Y |Y |Y |  |Y |  |
NetBeans*         |Y |F |Y |Y |Y |  |Y |Y |Y |Y |Y |Y |Y |Y |  |  |Y |*pre-v7.0
Notepad++         |W |F |Y |Y |  |Y*|Y*|Y*|Y |Y |  |Y |Y*|  |  |  |  |*with plugin
Pfaide            |W |C |Y |Y |  |  |  |Y |Y |Y |  |Y |Y |  |  |  |  |
PIDA              |LW|F |Y |Y |  |  |  |Y |Y |Y |  |Y |  |  |  |  |  |VIM based
PTVS              |W |F |Y |Y |Y |Y |Y |Y |Y |Y |  |Y |  |  |Y*|  |Y |*WPF bsed
PyCharm           |Y |CF|Y |Y*|Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |*JavaScript
PyDev (Eclipse)   |Y |F |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |Y |  |  |  |
PyScripter        |W |F |Y |  |Y |Y |  |Y |Y |Y |  |Y |Y |Y |  |  |  |
PythonWin         |W |F |Y |  |Y |  |  |Y |Y |  |  |Y |  |  |  |  |  |
SciTE             |Y |F¹|  |Y |  |Y |  |Y |Y |Y |  |Y |Y |  |  |  |  |¹Mac version is
ScriptDev         |W |C |Y |Y |Y |Y |  |Y |Y |Y |  |Y |Y |  |  |  |  |    commercial
Spyder            |Y |F |Y |  |Y |Y |  |Y |Y |Y |  |  |  |  |  |  |  |
Sublime Text      |Y |CF|Y |Y |  |Y |Y |Y |Y |Y |  |Y |Y |Y*|  |  |  |extensible w/Python,
TextMate          |M |F |  |Y |  |  |Y |Y |Y |Y |  |Y |Y |  |  |  |  |    *PythonTestRunner
UliPad            |Y |F |Y |Y |Y |  |  |Y |Y |  |  |  |Y |Y |  |  |  |
Vim               |Y |F |Y |Y |Y |Y |Y |Y |Y |Y |  |Y |Y |Y |  |  |  |
Visual Studio     |W |CF|Y |Y |Y |Y |Y |Y |Y |Y |? |Y |? |? |Y |? |Y |
Visual Studio Code|Y |F |Y |Y |Y |Y |Y |Y |Y |Y |? |Y |? |? |? |? |Y |uses plugins
WingIde           |Y |C |Y |Y*|Y |Y |Y |Y |Y |Y |  |Y |Y |Y |  |  |  |*support for C
Zeus              |W |C |  |  |  |  |Y |Y |Y |Y |  |Y |Y |  |  |  |  |
   Cross Platform -'  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |     
     Commercial/Free -'  |  |  |  |  |  |  |  |  |  |  |  |  |  |  '- Refactoring
   Auto Code Completion -'  |  |  |  |  |  |  |  |  |  |  |  |  '- Integrated DB Support
    Multi-Language Support -'  |  |  |  |  |  |  |  |  |  |  '- GUI Designer (Qt, Eric, etc)
  Integrated Python Debugging -'  |  |  |  |  |  |  |  |  '- Unit Testing
                    Error Markup -'  |  |  |  |  |  |  '- Code Templates
         Source Control Integration -'  |  |  |  |  '- Code Folding
                          Smart Indent -'  |  |  '- UML Editing / Viewing
                         Bracket Matching -'  '- Line Numbering

Acronyms used:

 L  - Linux
 W  - Windows
 M  - Mac
 C  - Commercial
 F  - Free
 CF - Commercial with Free limited edition
 ?  - To be confirmed

I don't mention basics like syntax highlighting as I expect these by default.

This is a just dry list reflecting your feedback and comments, I am not advocating any of these tools. I will keep updating this list as you keep posting your answers.

PS. Can you help me to add features of the above editors to the list (like auto-complete, debugging, etc.)?

We have a comprehensive wiki page for this question

Submit edits to the spreadsheet

Difference between BYTE and CHAR in column datatypes

One has exactly space for 11 bytes, the other for exactly 11 characters. Some charsets such as Unicode variants may use more than one byte per char, therefore the 11 byte field might have space for less than 11 chars depending on the encoding.

See also

How do I set up access control in SVN?

@Stephen Bailey

To complete your answer, you can also delegate the user rights to the project manager, through a plain text file in your repository.

To do that, you set up your SVN database with a default authz file containing the following:

# The content of this file always precedes the content of the
# $REPOS/admin/acl_descriptions.txt file.
# It describes the immutable permissions on main folders.
svnadmins = xxx,yyy,....

@svnadmins = rw
* = r
@svnadmins = rw
@projadmins = r
* =

@projadmins = rw

This default authz file authorizes the SVN administrators to modify a visible plain text file within your SVN repository, called '/admin/acl_descriptions.txt', in which the SVN administrators or project managers will modify and register the users.

Then you set up a pre-commit hook which will detect if the revision is composed of that file (and only that file).

If it is, this hook's script will validate the content of your plain text file and check if each line is compliant with the SVN syntax.

Then a post-commit hook will update the \conf\authz file with the concatenation of:

  • the TEMPLATE authz file presented above
  • the plain text file /admin/acl_descriptions.txt

The first iteration is done by the SVN administrator, who adds:

projadmins = zzzz

He commits his modification, and that updates the authz file.

Then the project manager 'zzzz' can add, remove or declare any group of users and any users he wants. He commits the file and the authz file is updated.

That way, the SVN administrator does not have to individually manage any and all users for all SVN repositories.

Most efficient way to increment a Map value in Java

The various primitive wrappers, e.g., Integer are immutable so there's really not a more concise way to do what you're asking unless you can do it with something like AtomicLong. I can give that a go in a minute and update. BTW, Hashtable is a part of the Collections Framework.

How to move the cursor word by word in the OS X Terminal

I have Alt+/ working: open Preferences » Settings » Keyboard, set the entry for option cursor left to send string to shell: \033b, and set option cursor right to send string to shell: \033f. You can also use this for other Control key combinations.

How can I view the allocation unit size of a NTFS partition in Vista?

You can use SysInternals NTFSInfo by Mark Russinovich from the command line and it converts fsutil fsinfo ntfsinfo into more readable information, especially MFT Table info.

Converting an integer to a hexadecimal string in Ruby

You can give to_s a base other than 10:

10.to_s(16)  #=> "a"

Note that in ruby 2.4 FixNum and BigNum were unified in the Integer class. If you are using an older ruby check the documentation of FixNum#to_s and BigNum#to_s

Is there a macro to conditionally copy rows to another worksheet?

If this is just a one-off exercise, as an easier alternative, you could apply filters to your source data, and then copy and paste the filtered rows into your new worksheet?

How do I use WPF bindings with RelativeSource?

I created a library to simplify the binding syntax of WPF including making it easier to use RelativeSource. Here are some examples. Before:

{Binding Path=PathToProperty, RelativeSource={RelativeSource Self}}
{Binding Path=PathToProperty, RelativeSource={RelativeSource AncestorType={x:Type typeOfAncestor}}}
{Binding Path=PathToProperty, RelativeSource={RelativeSource TemplatedParent}}
{Binding Path=Text, ElementName=MyTextBox}


{BindTo PathToProperty}
{BindTo Ancestor.typeOfAncestor.PathToProperty}
{BindTo Template.PathToProperty}
{BindTo #MyTextBox.Text}

Here is an example of how method binding is simplified. Before:

// C# code
private ICommand _saveCommand;
public ICommand SaveCommand {
 get {
  if (_saveCommand == null) {
   _saveCommand = new RelayCommand(x => this.SaveObject());
  return _saveCommand;

private void SaveObject() {
 // do something

{Binding Path=SaveCommand}


// C# code
private void SaveObject() {
 // do something

{BindTo SaveObject()}

You can find the library here:

Note in the 'BEFORE' example that I use for method binding that code was already optimized by using RelayCommand which last I checked is not a native part of WPF. Without that the 'BEFORE' example would have been even longer.

Adding a guideline to the editor in Visual Studio

This will also work in Visual Studio 2010 (Beta 2), as long as you install Paul Harrington's extension to enable the guidelines from the VSGallery or from the extension manager inside VS2010. Since this is version 10.0, you should use the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\10.0\Text Editor

Also, Paul wrote an extension that adds entries to the editor's context menu for adding/removing the entries without needing to edit the registry directly. You can find it here:

Setting the default ssh key location

man ssh gives me this options would could be useful.

-i identity_file Selects a file from which the identity (private key) for RSA or DSA authentication is read. The default is ~/.ssh/identity for protocol version 1, and ~/.ssh/id_rsa and ~/.ssh/id_dsa for pro- tocol version 2. Identity files may also be specified on a per- host basis in the configuration file. It is possible to have multiple -i options (and multiple identities specified in config- uration files).

So you could create an alias in your bash config with something like

alias ssh="ssh -i /path/to/private_key"

I haven't looked into a ssh configuration file, but like the -i option this too could be aliased

-F configfile Specifies an alternative per-user configuration file. If a configuration file is given on the command line, the system-wide configuration file (/etc/ssh/ssh_config) will be ignored. The default for the per-user configuration file is ~/.ssh/config.

Curl command line for consuming webServices?

Wrong. That doesn't work for me.

For me this one works:

-H 'SOAPACTION: ""'   
-H 'Content-type: text/xml'   
-d @/tmp/pinrequest.xml

Remove spaces from std::string in C++

std::string::iterator end_pos = std::remove(str.begin(), str.end(), ' ');
str.erase(end_pos, str.end());

How do I call a SQL Server stored procedure from PowerShell?

Use sqlcmd instead of osql if it's a 2005 database

How can I extract a predetermined range of lines from a text file on Unix?

 # print section of file based on line numbers
 sed -n '16224 ,16482p'               # method 1
 sed '16224,16482!d'                 # method 2

Reading PDF documents in .Net

PDFClown might help, but I would not recommend it for a big or heavy use application.

What's wrong with foreign keys?

In DB2, if MQTs (Materialized Query Tables) are used, foreign key constraints are required for the optimizer to choose the right plan for any given query. Since they contain the cardinality information, the optimizer uses the metadata heavily to use a MQT or not.

Why not use tables for layout in HTML?

No arguments in DIVs favour from me.

I'd say : If the shoe fits, wear it.

It's worth noting that it's difficult if not impossible to find a good DIV+CSS method of rendering contents in two or three columns, that is consistent on all browsers, and still looks just the way I intended.

This tips the balance a bit towards tables in most of my layouts, and altough I feel guilty of using them (dunny why, people just say it's bad so I try to listen to them), in the end , the pragmatic view is it's just easier and faster for me to use TABLEs. I'm not being payed by the hour, so tables are cheaper for me.

ORA-03113: end-of-file on communication channel after long inactivity in ASP.Net app

You could try this registry hack:


If it works, just keep increasing the KeepAliveTime. It is currently set for 2 minutes.

Before and After Suite execution hook in jUnit 4.x

Provided that all your tests may extend a "technical" class and are in the same package, you can do a little trick :

public class AbstractTest {
  private static int nbTests = listClassesIn(<package>).size();
  private static int curTest = 0;

  public static void incCurTest() { curTest++; }

  public static void closeTestSuite() {
      if (curTest == nbTests) { /*cleaning*/ }             

public class Test1 extends AbstractTest {
   public void check() {}
public class Test2 extends AbstractTest {
   public void check() {}

Be aware that this solution has a lot of drawbacks :

  • must execute all tests of the package
  • must subclass a "techincal" class
  • you can not use @BeforeClass and @AfterClass inside subclasses
  • if you execute only one test in the package, cleaning is not done
  • ...

For information: listClassesIn() => How do you find all subclasses of a given class in Java?

How to list the tables in a SQLite database file that was opened with ATTACH?

Via a union all, combine all tables into one list.

select name
from sqlite_master 
where type='table'

union all 

select name 
from sqlite_temp_master 
where type='table'

How do I check whether a file exists without exceptions?

You have the os.path.exists function:

import os.path

This returns True for both files and directories but you can instead use


to test if it's a file specifically. It follows symlinks.

Convert DOS line endings to Linux line endings in Vim

The following steps can convert the file format for DOS to Unix:

:e ++ff=dos     Edit file again, using dos file format ('fileformats' is ignored).[A 1]
:setlocal ff=unix     This buffer will use LF-only line endings when written.[A 2]
:w     Write buffer using Unix (LF-only) line endings.

Reference: File format

svn over HTTP proxy

In /etc/subversion/servers you are setting http-proxy-host, which has nothing to do with svn:// which connects to a different server usually running on port 3690 started by svnserve command.

If you have access to the server, you can setup svn+ssh:// as explained here.

Update: You could also try using connect-tunnel, which uses your HTTPS proxy server to tunnel connections:

connect-tunnel -P -T

Then you would use

svn checkout svn://localhost:10234/path/to/trunk

How do I use sudo to redirect output to a location I don't have permission to write to?

sudo at now  
at> echo test > /tmp/test.out  
at> <EOT>  
job 1 at Thu Sep 21 10:49:00 2017  

Why is using the JavaScript eval function a bad idea?

It's not necessarily that bad provided you know what context you're using it in.

If your application is using eval() to create an object from some JSON which has come back from an XMLHttpRequest to your own site, created by your trusted server-side code, it's probably not a problem.

Untrusted client-side JavaScript code can't do that much anyway. Provided the thing you're executing eval() on has come from a reasonable source, you're fine.

Does C# have an equivalent to JavaScript's encodeURIComponent()?

I tried to do full compatible analog of javascript's encodeURIComponent for c# and after my 4 hour experiments I found this

c# CODE:

string a = "!@#$%^&*()_+ some text here ??? ??????? ????";
a = System.Web.HttpUtility.UrlEncode(a);
a = a.Replace("+", "%20");

the result is: !%40%23%24%25%5e%26*()_%2b%20some%20text%20here%20%d0%b0%d0%bb%d0%b8%20%d0%bc%d0%b0%d0%bc%d0%b5%d0%b4%d0%be%d0%b2%20%d0%b1%d0%b0%d0%ba%d1%83

After you decode It with Javascript's decodeURLComponent();

you will get this: !@#$%^&*()_+ some text here ??? ??????? ????

Thank You for attention

How do I upload a file to an SFTP server in C# (.NET)?

Unfortunately, it's not in the .NET Framework itself. My wish is that you could integrate with FileZilla, but I don't think it exposes an interface. They do have scripting I think, but it won't be as clean obviously.

I've used CuteFTP in a project which does SFTP. It exposes a COM component which I created a .NET wrapper around. The catch, you'll find, is permissions. It runs beautifully under the Windows credentials which installed CuteFTP, but running under other credentials requires permissions to be set in DCOM.

What’s the best way to reload / refresh an iframe?

Now to make this work on chrome 66, try this:

const reloadIframe = (iframeId) => {
    const el = document.getElementById(iframeId)
    const src = el.src
    el.src = ''
    setTimeout(() => {
        el.src = src

Select current date by default in ASP.Net Calendar control

DateTime.Now will not work, use DateTime.Today instead.

How can I get Git to follow symlinks?

I used to add files beyond symlinks for quite some time now. This used to work just fine, without making any special arrangements. Since I updated to Git 1.6.1, this does not work any more.

You may be able to switch to Git 1.6.0 to make this work. I hope that a future version of Git will have a flag to git-add allowing it to follow symlinks again.

How do I ignore files in Subversion?

I found the article .svnignore Example for Java.

Example: .svnignore for Ruby on Rails,




And after that:

svn propset svn:ignore -F .svnignore .

Examples for .gitignore. You can use for your .svnignore

How do I create a folder in VB if it doesn't exist?

Since the question didn't specify .NET, this should work in VBScript or VB6.

Dim objFSO, strFolder
strFolder = "C:\Temp"
Set objFSO = CreateObject("Scripting.FileSystemObject")
If Not objFSO.FolderExists(strFolder) Then
End If