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• fgets, sscanf, and writing to arrays

  - by alldavidsluck

  beginner question here, I haven't been able to find examples that relate. I'm working on a C program that will take integer input from stdin using fgets and sscanf, and then write it to an array. However, I'm not sure how to make fgets write to the array. #define MAXINT 512 char input[MAXINT] int main(void) { int i; int j; int count=0; int retval; while (1==1) { fgets(input, MAXINT[count], stdin); retval = sscanf(input, "%d", &i); if (retval == 1) { count = count++; } else if (retval != 1) { break; } } Would I simply put fgets in a for loop? or is it more complicated than that?

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• scanf() (C Language ) confused me

  - by Nano HE

  Hello. When do I need to insert/don't insert & for scanf() in C? Thank you. int main() { char s1[81], s2[81], s3[81]; scanf("%s%s%s", s1, s2, s3); // If replace scanf() with the expression below, it works too. // scanf("%s%s%s", &s1, &s2, &s3); printf("\ns1 = %s\ns2 = %s\ns3 = %s", s1, s2, s3); return 0; } //programming is fun // //s1 = programming //s2 = is //s3 = fun

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• SQLite SQLite column can't be updated to any value but zero (real type)

  - by user1065320

  Hi I'm trying to create a three fields table (date,text,real), I can insert and update the first two fields but can't set or update the last one. createSQL = @"CREATE TABLE IF NOT EXISTS ACTIVITIES (MYDATE DATETIME PRIMARY KEY, ACTIVITY TEXT , LENGTH REAL);"; try to insert char *update = "INSERT OR REPLACE INTO ACTIVITIES (MYDATE, ACTIVITY , LENGTH) VALUES (?, ? ,?);"; sqlite3_stmt *stmt; if (sqlite3_prepare_v2(database, update , -1, &stmt, nil) == SQLITE_OK) { sqlite3_bind_double(stmt, 1, valueToWrite); sqlite3_bind_text(stmt, 2, [task UTF8String], -1, NULL); sqlite3_bind_double(stmt, 3, 1.5); } if (sqlite3_step(stmt) != SQLITE_DONE) { NSAssert1(0, @"Error updating table: %s", errorMsg); } sqlite3_finalize(stmt); sqlite3_close(database); The first two values are updated but the last one remains 0 even if I'm writing a value like 1.5 or put a double variable with a different value Thanks

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• fopen in C(Linux) returns "Too many open files"

  - by liv2hak

  static char filename[128] = "trace.txt"; g_file = fopen(filename, "w"); if(NULL == g_file) { printf("Cannot open file %s.error %s\n",filename,strerror(errno)); exit(1); } I am trying to open a empty text file named trace.txt in write mode (in my working directory.) The program is creating an empty file trace.txt in my directory.but the check (NULL == g_file) is returning true and it is returning error code 24 (Too many open files.).Any idea why this is.This is the first file I am opening in my program.

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• Using memory mapping in C for reading binary

  - by user1320912

  I am trying to read data from a binary file and process it.It is a very large file so I thought I would use memory mapping. I am trying to use memory mapping so I can read the file byte by byte. I am getting a few compiler errors while doing this. I am doing this on a linux platform #include <unistd.h> #include <sys/types.h> #include <sys/mman.h> int fd; char *data; fd = open("data.bin", O_RDONLY); pagesize = 4000; data = mmap((caddr_t)0, pagesize, PROT_READ, MAP_SHARED, fd, pagesize); The errors i get are : caddr not initialized, R_RDONLY not initialized, mmap has too few arguments. Could someone help me out ?

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• QMap inheritance with QMapIterator

  - by gregseth

  Hi, I made a personnal class which inherits QMap: class CfgMgr : public QMap<QString, CfgSet*> {...} I'm trying to iterate over all its elements like that: CfgMgr* m_pDefaults = new CfgMgr; // .../... QMapIterator<QString, CfgSet*> ics(*m_pDefaults); while (ics.hasNext()) { // doing my stuff } And I get the compile error: Can't convert parameter 1 from 'CfgMgr' to 'const QMap< Key,T &' with [ Key=QString, T=CfgSet * ] I tried with a dynamic_cast: QMapIterator<QString, CfgSet*> ics( *dynamic_cast< QMap<QString,CfgSet*>* >(m_pDefaults) ); it compiles, but always returns NULL. What's wrong? How can I solve this?

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• Unit testing with serialization mock objects in C++

  - by lhumongous

  Greetings, I'm fairly new to TDD and ran across a unit test that I'm not entirely sure how to address. Basically, I'm testing a couple of legacy class methods which read/write a binary stream to a file. The class functions take a serializable object as a parameter, which handles the actual reading/writing to the file. For testing this, I was thinking that I would need a serialization mock object that I would pass to this function. My initial thought was to have the mock object hold onto a (char*) which would dynamically allocate memory and memcpy the data. However, it seems like the mock object might be doing too much work, and might be beyond the scope of this particular test. Is my initial approach correct, or can anyone think of another way of correctly testing this? Thanks!

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• How to read the whole istream correctly?

  - by L.Lawliet

  Here is a simple code to print all characters of a txt file on screen: #include <iostream> #include <fstream> #include <string> using namespace std; int main() { int **i; int j,k; char a; ifstream test("test.txt", ios::binary); while((a=test.get())!=-1)//if I use "while(!test.eof())" here, how to avoid the output of the last character(-1) to std::cout, or any ostream objects? { putchar(a);//also change this to putchar(test.get()); } getchar(); } As I noted in the code, if I use "test.eof()" to judge the end of test.txt, I'll always get an extra blank at the end of the output. How to avoid it?

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• Does C++ have a proper implementation of interface that does not use vtable?

  - by gilbertc

  Does C++ have a proper implementation of interface that does not use vtable? for example class BaseInterface{ public: virtual void func() const = 0; } class BaseInterfaceImpl:public BaseInterface{ public: void func(){ std::cout<<"called."<<endl; } } BaseInterface* obj = new BaseInterfaceImpl(); obj->func(); the call to func at the last line goes to vtable to find the func ptr of BaseInterfaceImpl::func, but is there any C++ way to do that directly as the BaseInterfaceImpl is not subclassed from any other class besides the pure interface class BaseInterface? Thanks. Gil.

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• how to validate the input parameters before using in the static query?? SQL server 2005

  - by Guru

  consider table1 with 2 columns.. table1: column1 int, column2 char create procedure SP1(@col1,@col2) as begin select * from table1 where _ end Question: User may enter valid input for either (col1 or col2) or (both col1 and col2).so i need to validate the user input and use those correct column(s) in the satic query. eg: if both inputs are correct then, the query will be. select * from table1 where column1=@col1 and column2 =@col2 if only col2 is valid and col1 is not a valida one, then select * from table1 where column2=@col2 how to validate the input parameters before using in the static query?? in sql server 2005

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• iPhone OpenGL Template is cheating?

  - by carrots

  XCode's OpenGL template seems to be cheating to solve this "stretched" viewport problem I've been trying to understand for the last 3 hours. In the iphone "OpenGL ES Application" template, the colorful square that bounces up and down on the screen is not really a square at all! ES1Renderer.m (the ES2 file as well) static const GLfloat squareVertices[] = { -0.5f, -0.33f, 0.5f, -0.33f, -0.5f, 0.33f, 0.5f, 0.33f, }; But it comes out looking square on the device/simulator due to the stretching/squashing effect of a non-square viewport. I tried to fix it by fiddling with glFrustumf() but that doesn't seem to change the aspect ratio. I was able to get things looking good (not-stretched) when I fed glViewport() with a 1:1 widht:height.. But this doesn't seem like the answer because it offsets the viewport placement. What's the right way to correct for this stretching and why doesn't XCode do it that way?

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• How to create a GtkImage from a Cairo context?

  - by Zurbo82

  I got a paint function that works using a Cairo context and the end result should be a GtkImage (without intermediate image creation). I tried to use the gdk_cairo_create function but this code: ... GdkPixbuf *pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, 22, 22); GtkWidget *image = gtk_image_new_from_pixbuf (pixbuf); GdkDrawable *drawable = image->window; cairo_t *ctx = gdk_cairo_create (drawable); my_cairo_paint_function (ctx); ... fails with: Gdk-CRITICAL **: IA__gdk_cairo_create: assertion `GDK_IS_DRAWABLE (drawable)' failed Same with a simple: #include <gtk/gtk.h> #include <cairo.h> int main (int argc, char *argv[]) { gtk_init(&argc, &argv); cairo_t *ctx = gdk_cairo_create (gtk_widget_get_window (gtk_image_new_from_file ("foobar.png"))); gtk_main(); return 0; } I don't understand why this fails. Any help is appreciated!

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• std::string constructor corrupts pointer

  - by computergeek6

  I have an Entity class, which contains 3 pointers: m_rigidBody, m_entity, and m_parent. Somewhere in Entity::setModel(std::string model), it's crashing. Apparently, this is caused by bad data in m_entity. The weird thing is that I nulled it in the constructor and haven't touched it since then. I debugged it and put a watchpoint on it, and it comes up that the m_entity member is being changed in the constructor for std::string that's being called while converting a const char* into an std::string for the setModel call. I'm running on a Mac, if that helps (I think I remember some problem with std::string on the Mac). Any ideas about what's going on?

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• Boost::asio bug in MSVC10 - Failing BOOST_WORKAROUND in ~buffer_debug_check() in buffer.hpp

  - by shaz

  A straight compilation of example http://www.boost.org/doc/libs/1_43_0/doc/html/boost_asio/tutorial/tutdaytime3/src.html results in a runtime null pointer exception. Stack trace points to the buffer_debug_check destructor which contains this comment: // MSVC's string iterator checking may crash in a std::string::iterator // object's destructor when the iterator points to an already-destroyed // std::string object, unless the iterator is cleared first. The test #if BOOST_WORKAROUND(BOOST_MSVC, = 1400) succeeds in MSVC10 and (but) results in a null pointer exception in c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\xutility line 123 _Iterator_base12& operator=(const _Iterator_base12& _Right) { // assign an iterator if (_Myproxy != _Right._Myproxy) _Adopt(_Right._Myproxy->_Mycont); return (*this); } _Right._Myproxy is NULL

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• c, pass awk syntax as argument to execl

  - by Skuja

  I want to run following command in c to read systems cpu and memory usage: ps aux|awk 'NR > 0 { cpu +=$3; ram+=$4 }; END {print cpu,ram}' I am trying to pass it to execl command and after that read its output: execl("/bin/ps", "/bin/ps", "aux|awk", "'NR > 0 { cpu +=$3; ram+=$4 }; END {print cpu,ram}'",(char *) 0); but in terminal i am getting following error: ERROR: Unsupported option (BSD syntax) I would like to know how to properly pass awk as argument to execl?

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• VBScript Permission Denied on CopyFile

  - by Chris

  I'm running a VBScript in SQL Agent but I get a 'Permission Denied' on line 34 (the first copy attempt). I've run this script outside SQL Agent with no problems Function Main() Const SourceDrive As String = "X:\" Dim fso Dim Today Dim FileName Dim FromFile Dim FromDrive Dim ArchivePath Set fso = CreateObject("Scripting.FileSystemObject") Today = Format(Now, "yyyyMMdd") 'To add more sources just add them to the array list Dim Sources() As Variant Sources() = Array("Item1", _ "Item2") 'To add more targets just add them to the array list Dim Targets() As Variant Targets() = Array("C:\Users\myalias\Desktop\MyToFolder", _ "C:\Users\myalias\Desktop\MyToFolder2") For i = 0 To UBound(Sources) FileName = "WebSurveyAlertCallbacks_" & Sources(i) & "_" & Today & ".xls" FromDrive = fso.BuildPath(SourceDrive, Sources(i)) FromFile = fso.BuildPath(FromDrive, FileName) ArchivePath = fso.BuildPath(FromDrive, "Archive") If fso.FileExists(FromFile) Then For t = 0 To UBound(Targets) fso.CopyFile FromFile, fso.BuildPath(Targets(t), FileName), True Next fso.CopyFile FromFile, fso.BuildPath(ArchivePath, FileName), True fso.DeleteFile FromFile End If Next Set fso = Nothing Main = DTSTaskExecResult_Success End Function

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• Twitter widget stops page from rendering in IE 8, anybody know why?

  - by ro

  The widget works fine in Firefox but it completely stops the page from being rendered in IE8. This is the error report it gives me: Webpage error details User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; Media Center PC 3.0; .NET CLR 1.0.3705; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.648; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729) Timestamp: Fri, 23 Apr 2010 20:12:25 UTC Message: 'document.getElementsByTagName(...).0' is null or not an object Line: 9 Char: 8365 Code: 0 URI: http://widgets.twimg.com/j/2/widget.js Can anybody help?

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• How can I evaluate a deferred Linq statement when debugging?

  - by DanO

  I'm debugging in VS2010, and I want to inspect a string value but all I can get the debugger to show me (through watches, hovering, locals, etc.) is: "System.Linq.Enumerable+<TakeIterator>d__3a`1[System.Char]" I don't care if there are side effects from premature evaluation or whatever, I just want to see what the expression would evaluate to if I evaluate it right now at the current breakpoint. How is this done? Also can I change my code in such a way that it evaluates earlier? Not that I care when I'm not debugging... but just wondering. In case it is relevant... (I doubt it.) I'm stuffing a new entity object before saving it to the database... some fields are assigned with LINQ statements, I'm not sure when they get evaluated under the covers of EF. The DB update fails with 'string or binary data would be truncated... So I'm trying to find the too-long field.

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• Using charAt in java

  - by ThuL?nå F?rñ?nDö

  This is my assignment: Write a program where the user enters a string, and the program echoes it to the monitor with one character per line: C:\>java LinePerChar Enter a string: Octopus O c t o p u s I have tried, but I'm getting some compilation errors. Here's my code: import java.util.*; class CharactorEcho{ public static void main(String args []){ Scanner sc = new Scanner(System.in); System.out.println("Enter a string :"); try { String inputString = sc.nextLine(); for(int i=0; i < sc.length(); i++) { char c = inputString.charAt(i); System.out.println("" + c); } } catch(IOException e) { } } }

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• Using .dll methods to load data from file in C# code

  - by Espinas.iss

  I want to use in C# these methods: * int LibRaw::open_datastream(LibRaw_abstract_datastream *stream) * int LibRaw::open_file(const char *rawfile) * int LibRaw::open_buffer(void *buffer, size_t bufsize) * int LibRaw::unpack(void) * int LibRaw::unpack_thumb(void) that are stored in a libraw.dll. These functions one by one load data from file... I've been reading about P/Invoke but i'm not sure how to invoke them. Can anyone show me an example how to use all of these functions together in C# to load file (raw image stored in folder) or just how to PIvoke one of them. Thanx!

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• Are macro definitions compatible between MIPS and Intel C compiler?

  - by Derek

  I seem to be having a problem with a macro that I have defined in a C program. I compile this software and run it sucessfully with the MIPS compiler. It builds OK but throws the error "Segmentation fault" at runtime when using icc. I compiled both of these on 64 bit architectures (MIPS on SGI, with -64 flag and icc on an intel platform). Is there some magic switch I need to use to make this work correctly on both system? I turned on warnings for the intel compiler, and EVERY one of the places in my program where a macro is invoked throws a warning. Usually something along the lines of mismatched types on the macro's parameters (int to char *) or some such thing.

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• How to print an isosceles triangle

  - by Steve

  Hello, I'm trying to learn programming by myself, I'm working from a book that has the following problem which I can't solve: Allow the user to input two values: a character to be used for printing an isosceles triangle and the size of the peak for the triangle. For example, if the user inputs # for the character and 6 for the peak, you should produce the following display: # ## ### #### ##### ###### ##### #### ### ## # This is the code I've got so far: char character; int peak; InputValues(out character, out peak); for (int row = 1; row < peak * 2; row++) { for (int col = 1; col <= row; col++) { Console.Write(character); } Console.WriteLine(); } Console.Read() // hold console open Thanks in advance.

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• Floating point precision nuances.

  - by user247077

  Hi, I found this code in NVIDIA's cuda SDK samples. void computeGold( float* reference, float* idata, const unsigned int len) { reference[0] = 0; double total_sum = 0; unsigned int i; for( i = 1; i < len; ++i) { total_sum += idata[i-1]; reference[i] = idata[i-1] + reference[i-1]; } // Here it should be okay to use != because we have integer values // in a range where float can be exactly represented if (total_sum != reference[i-1]) printf("Warning: exceeding single-precision accuracy. Scan will be inaccurate.\n"); } (C) Nvidia Corp Can somebody please tell me a case where the warning would be printed, and most importantly, why. Thank you very much.

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• how to wrapper a c function whose parameters are a point to struct so that it can be called by lua s

  - by pierr

  Hi, I have follwing C function. How should I wrapper it so it can be called by lua script? typedef struct tagT{ int a ; int b ; }type_t; int lib_a_f_4(type_t *t) { return t->a * t->b ; } I know how to wrapper it if the function parameter type were int or char *. Should I use table type for a C structure? I am a lua beginner and thanks for help.

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• Constructor/Destructor involving a class and a struct

  - by Bogdan Maier

  I am working on a program and need to make an array of objects, specifically I have a 31x1 array where each position is an object, (each object is basically built out of 6 ints). Here is what I have but something is wrong and i could use some help thank you. 31x1 struct header" const int days=31; struct Arr{ int days; int *M; }; typedef Arr* Array; 31x1 matrix constructor: void constr(){ int *M; M = new Expe[31]; // Expe is the class class header: class Expe { private: //0-HouseKeeping, 1-Food, 2-Transport, 3-Clothing, 4-TelNet, 5-others int *obj; } Class object constructor: Expe::Expe() { this->obj=new int[6]; } help please... because i`m pretty lost.

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