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• How can I login linux using C or C++

  - by jnblue

  I need to programmely switch the current user to another,then the followed code should be executed in the environment(such as path,authority..) of another user. I've find the 'chroot()','setuid()' may be associated with my case, but these functions need the root authority, I don't have root authority, but I have the password of the second user. what should I do? I have tried shell "su - " can switch current user, can this command help me in my C++ code? Don't laugh at me if my question is very stupid, I'm a true freshman on linux. :) Thanks!

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• overloading new operator in c++

  - by Angus

  I have a code for best fit algorithm. I want to try to use the best fit algorithm using the operator new. Every time I create an object I should give it from the already allocated memory say, 1]20 2]12 3]15 4]6 5]23 respectively. which ever minimum amount fits to the objects size(eg.21) I wanted to do it for different object types, so I need to write the overloaded operator new to be common functionality for all the class objects. Can I do it through friend functions, or is there any possible way to do it.

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• c++ compilation error

  - by clamp

  hello, i got a compile error which i do not understand. i have a h/cpp file combination that does not contain a class but just defines some utility functions. when i try to use a struct that is defined in another class i get the error: error C2027: use of undefined type so, stripped down to the problem, the h file looks like this namespace A { void foo(B::C::SStruct const & Var); } the definition of SStruct is in a class which is in another h-file, that is of course included. namespace B { Class C { struct SStruct { }; } } what am i missing here? thanks!

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• Are sessions modifiable by the client/user?

  - by Sev

  In my PHP Web-App I use sessions to store the user's data. For exmaple, if a user logs in, then an instance of the User class is generated and stored in a Session. I have access levels associated with each user to determine their privileges. Store the user in a session by: $_SESSION['currentUser'] = new User($_POST['username']); For example: if($_SESSION['currentUser'] -> getAccessLevel() == 1) { //allow administration functions } where getAccessLevel() is simply a get method in the User class that returns the _accesslevel member variable. Is this secure? Or can the client somehow modify their access level through session manipulation of some sort?

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• Page layout breaks only in Opera which is weird?

  - by Qwibble

  Okay so I'm working on an admin panel, in which everything should always be only within the view port until you hit the minimum widths and heights set. The current version of it can be seen here (its still in development) : http://qwibbledesigns.co.uk/preview/Admin/ In layout terms, it works flawlessly in all browsers, even down to ie6 =D. However, opera doesn't like it, and for some reason, always add's extra space to the bottom of the page, making it have an extra scrollbar, and I can't fathom it out which is highly annoying. Jquery is used to set the height of the container, sidebar, and content area so that they're always within the browser view port, and these functions rerun when the window is resized. I therefore cannot work out the the life of me what's wrong with opera. Would anyone mind taking a look and seeing if they can work it out? =D

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• JQuery create new select option

  - by nav

  Hi I have the below functions in regular javascript creating select options. Is there a way I can do this with JQuery without having to use the form object? function populate(form) { form.options.length = 0; form.options[0] = new Option("Select a city / town in Sweden",""); form.options[1] = new Option("Melbourne","Melbourne"); } Below is how I call the function above: populate(document.form.county); //county is the id of the dropdownlist to populate. Many Thanks,

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• MySQL Integer vs DateTime index

  - by David Kuridža

  Let me start by saying I have looked at many similar questions asked, but all of them relate to Timestamp and DateTime field type without indexing. At least that is my understanding. As we all know, there are certain advantages when it comes to DateTime. Putting them aside for a minute, and assuming table's engine is InnoDB with 10+ million records, which query would perform faster when criteria is based on: DateTime with index int with index In other words, it is better to store date and time as DateTime or UNIX timestamp in int? Keep in mind there is no need for any built-in MySQL functions to be used.

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• Issue with this function. The code is not executing.

  - by Tapha

  The function is supposed to update the values in the database. Here is the code: //Functions //Function to Update users networth function update_net($name) { //Get worth & balance at the time $sql_to_get_worth_balance = "SELECT * FROM user WHERE username = '$name'"; $sql_query = mysql_query($sql_to_get_worth_balance); while ($rows = mysql_fetch_assoc($sql_query)) { $worth = $rows['worth']; $balance_ = $rows['cash_balance']; } //Get net_worth now $new_net_worth = $worth + $balance; //Update net_worth $sql_for_new_worth = "UPDATE user SET net_worth = '$new_net_worth'"; $sql_worth_query = mysql_query($sql_worth); } It is used here: //Get username $username = $_SESSION['username']; if (isset($username)) { //Update networth $update_worth = update_net($username);

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• Any good idioms for error handling in straight C programs?

  - by Will Hartung

  Getting back in to some C work. Many of my functions look like this: int err = do_something(arg1, arg2, arg3, &result); With the intent the result gets populated by the function, and the return value is the status of the call. The darkside is you get something naive like this: int err = func1(...); if (!err) { err = func2(...); if (!err) { err = func3(...); } } return err; I could macro it I suppose: #define ERR(x) if (!err) { err = (x) } int err = 0; ERR(func1(...)); ERR(func2(...)); ERR(func3(...)); return err; But that only works if I'm chaining function calls, vs doing other work. Obviously Java, C#, C++ have exceptions that work very well for these kinds of things. I'm just curious what other folks do and how other folks do error handling in their C programs nowadays.

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• Initializing a array after declaration

  - by robUK

  Hello, gcc 4.4.3 c89 I have the following code as a sample of what I am trying to do. I don't know the actual size of the array, until I enter the function. However, I don't think I can set the array size after I have declared it. I need it global as some other functions will need to access the device names. Many thanks for any suggestions, /* global */ char *devices_names[]; void fill_devices(size_t num_devices) { devices_names[num_devices]; /* start filling */ }

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• using ajax url to call function

  - by Steven Vanerp

  Hopefully I can ask this correctly cuz I know what I want it to do but can't seem to find any answers from searching. I have a func.php page where I have all my functions and I want ajax to use one function from that page. func.php function toptable() { echo"something happens in here"; } index.php <?php include 'func.php'; ?> <script type="text/javascript"> function check_username() { uname=document.getElementById("username").value; var params = "user_id="+uname; var url = "topoftable()"; $.ajax({ type: 'POST', url: url, dataType: 'html', data: params, beforeSend: function() { document.getElementById("right").innerHTML= 'checking' ; }, complete: function() { }, success: function(html) { document.getElementById("right").innerHTML= html ; } }); } </script> Make sense?

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• func_get_args detect context

  - by Steve

  I have a script where it accepts a varying number of arguments. I want to use func_get_args to perform operations on said arguments. If I have one function like this: function Something() { foreach(func_get_args($this) as $functions) { // Do something } // Return.. } I want to be able to call this function in, for example, another function to add/save entries. The add/save function would have arguments 'title', 'description' etc.. I basically want to know if there is a way to detect the context of a function call. Can I pass something to func_get_args that will let it know that its called in a certain function? So if I do: function Save($title, $desc) { $vars = $this->Something(); } I want $vars to contain $title and $desc after modifying them.

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• Calling C++ function from C.

  - by claws

  I know this. Calling C function from C++: If my application was in C++ and I had to call functions from a library written in C. Then I would have used //main.cpp extern "C" void C_library_function(int x, int y);//prototype C_library_function(2,4);// directly using it. This wouldn't mangle the name C_library_function and linker would find the same name in its input *.lib files and problem is solved. Calling C++ function from C??? But here I'm extending a large application which is written in C and I need to use a library which is written in C++. Name mangling of C++ is causing trouble here. Well I cannot use C++ compiler over my C project because thats breaking lot of other stuff. What is the way out? By the way I'm using MSVC

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• What is the precedence of characters when sorting in MySQL, PHP, or just in general?

  - by FireCoding

  Question: Where can I find the precedence of characters when sorting in MySQL, PHP, or just in general on Linux and Windows OS? For example, everybody knows that a comes before b when performing an ascending sort on a string in MySQL. But what about other characters? Does the dollar-sign $ come before asterisk * ? Does a space come before an exclamation-mark? etc... What dictates the sort order? Does it use underlying ascii / UTF-8 values? Is it different for different technologies? Technologies to consider: Databases - MySQL / SQL / SQLite / Oracle / etc Programming languages (for string-sorting functions) - PHP / Javascript / ASP.NET / Visual C# / Python / Ruby / Objective C OS (i.e., sorting files by filename) - Windows / Linux / MacOS / iOS / Android

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• Callback Timer function in C++

  - by user3596609

  I am trying to implement a callback timer function in C++ which should do a callback after a timeout. I am listening on a socket and then waiting for messages on it. so if I have something like getMessages() and I want to pass the timer function in it as an argument. So how can it be implemented that after the receive of a message, the timer is started and the callback happens if there is a timeout before the next messages arrives. I am new to callback functions. Any help is greatly appreciated. Thanks!

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• Just how much do I want to make virtual?

  - by Alex

  I am writing an abstract superclass where literally every method is going to be overridden. There is some default functionality I could implement, but most of the time it's enough to leave the implementation to the subclass writer. Since just about every method is going to be overwritten, how much should I make virtual and how much should I just leave as regular methods? In the current incarnation, everything is virtual, but I still haven't let this loose to anyone to use, so the design is flexible. What advantages/disadvantages are there to virtual functions? Links to good reading material about this would be appreciated.

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• Why does the Win32-API have so many custom types?

  - by sub

  I'm new to the Win32 API and the many new types begin to confuse me. Some functions take 1-2 ints and 3 UINTS as arguments. Why can't they just use ints? What are UINTS? Then, there are those other types: DWORD LPCWSTR LPBOOL Again, I think the "primitive" C types would be enough - why introduce 100 new types? This one was a pain: WCHAR* I had to iterate through it and push_back every character to an std::string as there wasn't another way to convert it to one. Horrible. Why WCHAR? Why reinvent the wheel? They could have just used char* instead, or?

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• Jquery mobile function calls before Ajax Request end

  - by rpmlins

  Here is my problem. When My Home page shows, I call the LoadUser functions, which on success, sets the globalUser variable with the returned json, and after it loads I call the alert function but it says globalUser is undefined. I have tried many other work arounds, but I always get the undefined mesage. If I call the alert(globalUser); on the success function, it works as expected alerting the object. $('#Home').live('pageshow', function(event) { $.when(LoadUser()).done(function(a1) { alert(globalUser); }); }); function LoadUser() { $.ajax({ // connects with the web service and validate de user input url: "http://localhost:51396/Icademy.asmx/GetUser", contentType: "application/json; charset=utf-8", data: { "userName": "'rodrigo'" }, dataType: "jsonp", success: function(json) { globalUser = JSON.parse(json.d); return globalUser; }, error: function(ret) { alert("Um erro ocorreu, tente novamente mais tarde."); } }); }

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• PotgreSQL 2D array to rows

  - by PostGreSQL newbie

  Hello, I am new to PostgreSQL array's. I am trying to a write a procedure to convert array-into-rows, and wanted following output: alphabet | number ---------+---------- A | 10 B | 10 C | 6 D | 9 E | 3 from following: id | alphabet_series -------+-------------------------------------------------------------------------------------------------- 1 | {{A,10},{B,10},{C,6},{D,9},{E,3},{F,9},{I,10},{J,17},{K,16},{L,17},{M,20},{N,13},{O,19}} I have searched for array-to-rows functions, but they all seems to accept 1-d array. but in this case, it is 2-d array. Any pointers will be appreciated. Many thanks.

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• Changing the way widgets are rendered/displayed in a form on the template

  - by user334017

  I have a form with a few other embedded forms and some various widgets. The widgets are all saved in an array $form['elements'] and for some of them, I want to display labels and things, but for others I only want to display the basic rendering. foreach($form['elements'] as $elem) echo $elem->render(); this displays everything about the widget. The way it is right now, I couldn't for example call $elem['..'] because the different subforms appear in a random order and have different variable names. I assume I could still put some checks in the template, but it seems easier to fix this in the widget class, like override one of the render functions or something. How would I go about doing this or do you have any links that could help me understand how do do this? on a side note, one of my widgets is the sfWidgetFormChoice and I have no clue where it actually renders or how renderer_classes work

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• Is there a way to read 10000 lines from a file in python?

  - by windsound

  I am relatively new in python, was working on C a lot. Since I was seeing so many new functions in python that I do not know, I was wondering if there is a function that can request 10000 lines from a file in python. Something like this is what I expect if that kind of function exist: lines = get_10000_lines(file_pointer) Did python have a build-in function or is there any module that I can download for this? If not, how do I do this to be easiest way. I need to analyze a huge file so I want to read 10000 lines and analyze per time to save memory. Thanks for helping!

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• C++ Static Array Initialization - Memory Issue

  - by donalmg

  Hi, I have a header file which contains a member variable declaration of a static char array: class ABC { public: static char newArray[4]; // other variables / functions private: void setArray(int i, char * ptr); } In the CPP file, I have the array initialized to NULL: char ABC::newArray[4] = {0}; In the ABC constructor, I need to overwrite this value with a value constructed at runtime, such as the encoding of an integer: ABC::ABC() { int i; //some int value defined at runtime memset(newArray, 0, 4); // not sure if this is necessary setArray(i,newArray); } ... void setArray(int i, char * value) { // encoding i to set value[0] ... value [3] } When I return from this function, and print the modified newArray value, it prints out many more characters than the 4 specified in the array declaration. Any ideas why this is the case. I just want to set the char array to 4 characters and nothing further. Thanks...

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• Processing a method after the view has loaded..

  - by Susanth

  Hi ! I have implemented a subview which is supposed to load immediately when I click a button in the parent view. After loading the subview(which is basically holding an activityindicator), the program is supposed to process a method(which gets data from a server, so takes time) in it. However, I am unable to do it. What happens now is, when I click the button on the parent view, it processes the method first and only after that does the subview load on screen. Why is this so? Is there any specific functions I could use to make my method load only after the view has loaded?

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• C++ Boost bind value type {solved}

  - by aaa

  hello. I look in documentation and source code but cannot figure out how to get return value type of boost bind functor. I am trying to accomplish following: 35 template<typename T,size_t N, class F> 36 boost::array<typename F::value_type, N> make_array(T (&input)[N], F unary) { 37 boost::array<typename F::value_type, N> array; 38 std::transform(input, input + N, array.begin(), unary); 39 return array; 40 } where F can be bind functor. the above does not work because functor does not have value_type. for that matter, is there standard interface for unary/binary functor as far as return value. solution: it should be result_type. also equivalent defined are argument_type and first/second_argument_type for binary functions Thanks

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• Method to register method to be called when event is raised

  - by zaidwaqi

  I have a Panel which contains 20 PictureBox controls. If a user clicks on any of the controls, I want a method within the Panel to be called. How do I do this? public class MyPanel : Panel { public MyPanel() { for(int i = 0; i < 20; i++) { Controls.Add(new PictureBox()); } } // DOESN'T WORK. // function to register functions to be called if the pictureboxes are clicked. public void RegisterFunction( <function pointer> func ) { foreach ( Control c in Controls ) { c.Click += new EventHandler( func ); } } } How do I implement RegisterFunction()? Also, if there are cool C# features that can make the code more elegant, please share.

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