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  • C input loop for shell

    - by AustinM
    So I'm working on creating a very simple C program that just preforms shell commands. This is what I have so far: #include <stdio.h> int main() { char input[30]; fputs("$ ", stdout); fflush(stdout); fgets(input, sizeof input, stdin); system(input); } It works, but only for one command. For example if I compile and type ./cmd I get the $ prompt. If I type ls I get what I'm supposed to get. But then it exits and goes back to the regular system shell. How can I make it so after the user types a command it goes back to the "$" input.

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  • C++, WCHAR[] to std::cout and comparision

    - by michal
    Hi, I need to put WCHAR[] to std::cout ... It is a part of PWLAN_CONNECTION_NOTIFICATION_DATA passed from Native Wifi API callback. I tried simply std::cout << var; but it prints out the numeric address of first char. the comparision (var == L"some text") doesn't work either. The debugger returns the expected value, however the comparision returns 0. How can I convert this array to a standard string(std::string)? Thanks in advance

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  • Strange macro declaration in C

    - by Andrey Atapin
    Exploring libusb-1.0.9 source code, I have found such line (./os/poll_windows.c:78): #define CHECK_INIT_POLLING do {if(!is_polling_set) init_polling();} while(0) As for me this is the same like: #define CHECK_INIT_POLLING if(!is_polling_set) init_polling(); Is there any reason to loop that expression? UPDATE: I couldn't still realize what'd be wrong after the answers, and the following example helped: #include <stdio.h> #define TEST if(test) foo(); #define TEST_DO do { if(test) foo(); } while(0) int test = 1; void foo() { printf("%s", "Foo called"); } int main(int argc, char** argv) { if(argc > 1) TEST_DO; /* LINE 12 */ else printf("%s", "skipping..."); return 0; } If you put TEST at line 12, a compiler will give an error "error: ‘else’ without a previous ‘if’". Hope, this will help someone.

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  • Reading long lines from text file

    - by sonofdelphi
    I am using the following code for reading lines from a text-file. What is the best method for handling the case where the line is greater than the limit SIZE_MAX_LINE? void TextFileReader::read(string inFilename) { ifstream xInFile(inFilename.c_str()); if(!xInFile){ return; } char acLine[SIZE_MAX_LINE + 1]; while(xInFile){ xInFile.getline(acLine, SIZE_MAX_LINE); if(xInFile){ m_sStream.append(acLine); //Appending read line to string } } xInFile.close(); }

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  • SQL SELECT using in() but excluding others.

    - by Pickledegg
    I have a table called 'countries' linked to another table 'networks' with a many to many relationship: countries countries_networks networks +-------------+----------+ +-------------+----------+ +-------------+---------------+ | Field | Type | | Field | Type | | Field | Type | +-------------+----------+ +-------------+----------+ +-------------+---------------+ | id | int(11) | | id | int(11) | | id | int(11) | | countryName | char(35) | | country_id | int(11) | | name | varchar(100) | +-------------+----------+ | network_id | int(11) | | description | varchar(255) | To retrieve all countries that have a network_id of 6 & 7, I just do the following: ( I could go further to use the networks.name but I know the countries_networks.network_id so i just use those to reduce SQL.) SELECT DISTINCT countryName FROM countries AS Country INNER JOIN countries_networks AS n ON Country.id = n.country_id WHERE n.network_id IN (6,7) This is fine, but I then want to retrieve the countries with a network_id of JUST 8, and no others. I'ver tried the following but its still returning networks with 6 & 7 in. Is it something to do with my JOIN? SELECT DISTINCT countryName FROM countries AS Country INNER JOIN countries_networks AS n ON Country.id = n.country_id WHERE n.network_id IN (8) AND n.network_id not IN(6,7) Thanks.

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  • MySQLi String comparisons using keys

    - by asdasd
    I have a table with lets say 2 columns. id number, and value. Value is a string (var char). Lets say i have a number x, and a list of numbers a1, a2, a3, a4, a5..... where x is not in the list. All of these numbers correspond to a unique row in the table. I want to know if the string value for x in the table is contained in one of the string values for any table entry for a1, a2, a3, a4... Lets say i have these rows: x, aaa a1, bbb a2, ccc a3, ddd a4, aaabbbcc then i want somehow a confirmation that yes, the value for x is included in one of the values in my list of numbers (a4 contains x). I know i can do this in a couple queries and shove it down some PHP and get my answer. But can i do this with one query?

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  • c++: how can i read a file line by line to a string type variable?

    - by ufk
    Hiya. I'm trying to read a file line by line to a string type variable using the following code: #include <iostream> #include <fstream> ifstream file(file_name); if (!file) { cout << "unable to open file"; exit(1); } string line; while (!file.eof()) { file.getline(line,256); cout<<line; } file.close(); it won't compile when I try to use String class, only when i use char file[256] instead. how can I get line by line into a string class? thanks!

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  • How to call a function from a shared library?

    - by Frank
    What is the easiest and safest way to call a function from a shared library / dll? I am mostly interested in doing this on linux, but it would be better if there were a platform-independent way. Could someone provide example code to show how to make the following work, where the user has compiled his own version of foo into a shared library? // function prototype, implementation loaded at runtime: std::string foo(const std::string); int main(int argc, char** argv) { LoadLibrary(argv[1]); // loads library implementing foo std::cout << "Result: " << foo("test"); return 0; } BTW, I know how to compile the shared lib (foo.so), I just need to know an easy way to load it at runtime.

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  • How to check whether iterators form a contiguous memory zone?

    - by Vincent
    I currently have the following function to read an array or a vector of raw data (_readStream is a std::ifstream) : template<typename IteratorType> inline bool MyClass::readRawData( const IteratorType& first, const IteratorType& last, typename std::iterator_traits<IteratorType>::iterator_category* = nullptr ) { _readStream.read(reinterpret_cast<char*>(&*first), (last-first)*sizeof(*first)); return _readStream.good(); } First question : does this function seem ok for you ? As we read directly a block of memory, it will only work if the memory block from first to last is contiguous in memory. How to check that ?

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  • The glutKeyboardFunc does not react to key presses immediately

    - by Nibirue
    I have a function glutKeyboardFunc(keyboard), where keyboard has: void keyboard(unsigned char key, int x, int y){ float alpha = 1.0; switch(key){ case 'c': glClearColor(1,0,0,alpha); printf("success"); break; } } This is a summary of the function; it works properly, but only once some other action has occurred. For instance, the printf statement reports success immediately on keystroke 'c', but the background color does not become active until I click somewhere else on the canvas. I want all keystrokes to have an immediate effect.

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  • c++: strange syntax in what() method of std::exception

    - by Patrick Oscity
    When i am inheriting from std::exception in order to define my own exception type, i need to override the what() method, which has the following signature: virtual const char* what() const throw(); This definitely looks strange to me, like if there were two method names in the signature. Is this some very specific syntax, like with pure virtual methods, e.g.: virtual int method() const = 0; or is this a feature, that could somehow be used in another context, too? And if so, for what could it be used?

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  • Resolve circular typedef dependency?

    - by Nick
    What is the best way to resolve the following circular dependency in typedef-ing these structs? Note the C language tag - I'm looking for a solution in standard gcc C. typedef struct { char* name; int age; int lefthanded; People* friends; } Person; typedef struct { int count; int max; Person* data; } People;

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  • why it is up to the compiler to decide what value to assign when assigning an out-of-range value to

    - by Allopen
    in C++ Primer 4th edition 2.1.1, it says "when assigning an out-of-range value to a signed type, it is up to the compiler to decide what value to assign". I can't understand it. I mean, if you have code like "char 5 = 299", certainly the compiler will generate asm code like "mov BYTE PTR _sc$[ebp], 43"(VC) or "movb $43, -2(%ebp)"(gcc+mingw), it IS decided by the compiler. but what if we assign a value that is given by the user input? like, via command line? and the asm code generated will be "movb %al, -1(%ebp)"(gcc+mingw) and " mov cl, BYTE PTR _i$[ebp] mov BYTE PTR _sc$[ebp], cl "(VC), so now how can compiler decide what will happen? I think now it is decided by the CPU. Can you give me a clear explanation?

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  • const ready only local copies

    - by robUK
    Hello gcc 4.4.4 c89 I am just wondering is it worth passing a const into a function. i.e. void do_something(const char *dest, const int size) The size is a ready-only so I don't want to change it. However, some developers never have this as const has it is a local copy that is being used. The pointer is const as you can change the value in the calling routine. I always have a const on ready-only local copies, as it confirms to anyone reading my code that it is a ready-only variable. And also, when coding I don't make the mistake of changing it without realizing. Many thanks for any suggestions,

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  • another file_exists with special chars problem

    - by Camran
    I have some folders with special characters in their names. I run currently at a test-computer with Windows OS, but later I will use LINUX. My problem is that the folders with special chars in their names cannot be recognized somehow. ex: file_exists('../Bilar/27733691_1.jpg') // TRUE file_exists('../Båtar/27733691_1.jpg') // FALSE because of the special char in folder name... How should I solve this? I plan to run LINUX in the future when website is online... would that matter? Please explain thoroughly because I am a newb at this Thanks

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  • Single C++/CLI method to wrap many type specific C functions

    - by T33C
    I am wrapping a C library using C++/CLI so that the C library can be used easily from C# in a C#'ish way. Some of the functions in this library are for putting a value into a container. There are no generics in C so there exists a function per type CLIB_SetBool(BOOL value), CLIB_SetInt(int value), CLIB_SetString(char* string) and so on. To make it easier to use from C#, I have created a single Set function which takes a System::Object. I have two related questions: With my method how would you use a switch statement on the type of System::Object to call the correct CLIB_Setxxxx function. [typeid is only for unmanaged code and I can't seem to use GetType.] Is there a better way to wrap these functions like using a Generic? [I started using template specialisation but then realised that C# doesn't see templates.] Thanks.

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  • Looking at the C++ new[] cookie. How portable is this code?

    - by carleeto
    I came up with this as a quick solution to a debugging problem - I have the pointer variable and its type, I know it points to an array of objects allocated on the heap, but I don't know how many. So I wrote this function to look at the cookie that stores the number of bytes when memory is allocated on the heap. template< typename T > int num_allocated_items( T *p ) { return *((int*)p-4)/sizeof(T); } //test #include <iostream> int main( int argc, char *argv[] ) { using std::cout; using std::endl; typedef long double testtype; testtype *p = new testtype[ 45 ]; //prints 45 std::cout<<"num allocated = "<<num_allocated_items<testtype>(p)<<std::endl; delete[] p; return 0; } I'd like to know just how portable this code is.

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  • Oracle spatial search within distance

    - by KA_lin
    I have the following table Cities: ID(int),City(char),latitude(float),longitude(float). Now based on a user`s longitude(ex:44.8) and latitude(ex:46.3) I want to search for all the cities near him within 100 miles/KM. I have found some examples but don`t know how to adapt them to my case select * from GEO.Cities a where SDO_WITHIN_DISTANCE([I don`t know], MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(44.8,46.3, NULL) ,NULL, NULL), 'distance = 1000') = 'TRUE'; Any help would be appreciated. P.S: If it is possible to have the distance and to be sorted P.P.S: I want to do it in this way due to performance issues, I have done this in this way http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL but it takes too long...

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  • can we write this in C++ switch ?

    - by jellly
    #include <iostream> using namespace std; int main(){ char i; cin >>i; switch (i){ case ('e'||'i'||'o'||'u'||'a'): cout<<"Vowel"; break; case ('+'||'-'||'/'||'*'||'%'): cout<<"Op"; break; } return 0; } if not than how can we use comparison or logical operators in switch ? & why cant we declare and initialize variable in single case without using scope ?

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  • Best way to get a date in .NET?

    - by frenchie
    I'm getting a string back from my page and I want to make sure it's a date. This is what I have so far (it works) and I just want to know if this is the "best" way to do it. I'm using .NET 4. int TheMonth =0; int TheDay = 0; int TheYear = 0; DateTime NewDate; var TheIncomingParam = Request.Params.Get("__EVENTARGUMENT").ToString(); char[] TheBreak = { '/' }; string[] TheOutput = TheIncomingParam.Split(TheBreak); try { TheMonth = Convert.ToInt32(TheOutput[0]); } catch { } try { TheDay = Convert.ToInt32(TheOutput[1]); } catch { } try { TheYear = Convert.ToInt32(TheOutput[2]); } catch { } if (TheMonth!=0 && TheDay!=0 && TheYear!=0) { try { NewDate = new DateTime(TheYear, TheMonth, TheDay); } catch { var NoDate = true; } }

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  • crc24 from c to python

    - by biiiiiaw
    can someone please translate this code to python? i have tried and tried again, but have not managed it: #define CRC24_INIT 0xB704CEL #define CRC24_POLY 0x1864CFBL typedef long crc24; crc24 crc_octets(unsigned char *octets, size_t len) { crc24 crc = CRC24_INIT; int i; while (len--) { crc ^= (*octets++) << 16; for (i = 0; i < 8; i++) { crc <<= 1; if (crc & 0x1000000) crc ^= CRC24_POLY; } } return crc & 0xFFFFFFL; } i have the rotate left function (ROL24(value,bits_to_rotate_by)), which i know works since i got it from a source code of a reputable programmer, but i dont get the * and ++ on octet. i only sort of understand how ++ works in c++, and i dont know what * is at all

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  • user buffer after doing 'write' to file opened with O_DIRECT

    - by user1868481
    I'm using the O_DIRECT flag to write to the disk directly from the user buffer. But as far as I understand, Linux doesn't guarantee that after this call, the data is written. It just writes directly from the user buffer to the physical device using DMA or anything else... Therefore, I don't understand if I can write to the user buffer after the call to 'write' function. I'm sure that example code will help to understand my question: char *user_buff = malloc(...); /* assume it is aligned as needed */ fd = open(..., O_DIRECT); write(fd, ...) memset(user_buff, 0, ...) Is the last line (memset) legal? Is writing to the user buffer valid that is maybe used by DMA to transfer data to the device?

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  • Possible to convert list of #defines into strings (C++)

    - by brandonC
    Suppose I have a list of #defines in a header file for an external library. These #defines represent error codes returned from functions. I want to write a conversion function that can take as an input an error code and return as an output a string literal representing the actual #define name. As an example, if I have #define NO_ERROR 0 #define ONE_KIND_OF_ERROR 1 #define ANOTHER_KIND_OF_ERROR 2 I would like a function to be able to called like int errorCode = doSomeLibraryFunction(); if (errorCode) writeToLog(convertToString(errorCode)); And have convertToString() be able to auto-convert that error code without being a giant switch-case looking like const char* convertToString(int errorCode) { switch (errorCode) { case NO_ERROR: return "NO_ERROR"; case ONE_KIND_OF_ERROR: return "ONE_KIND_OF_ERROR"; ... ... ... I have a feeling that if this is possible, it would be possible using templates and metaprogramming, but that would only work the error codes were actually a type and not a bunch of processor macros. Thanks

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  • How do I get the inner arrays length in a 2d array in C#?

    - by Phukab
    Lets say I create a jagged 2d array like so: public static char[,] phoneLetterMapping = { {'0'}, {'1'}, {'A', 'B', 'C'} }; Now, given the first index of the array, I would like to be able to get the length of the inner array. So, I would like to be able to do something like: phoneLetterMapping[2].length I can do that in Java. But the intellisense menu doesn't return the normal members of an array when I type in the first bracket of the [][] 2d array. So, how do I get the inner array lengths in my 2d array in C#?

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  • SQL tables using VARCHAR with UTF8 (with respect to multi byte character length)

    - by Elius
    Like in Oracle VARCHAR( 60 CHAR ) I would like to specify a varchar field with variable length depending on the inserted characters. for example: create table X (text varchar(3)) insert into X (text) VALUES ('äöü') Should be possible (with UTF8 as the default charset of the database). On DB2 I got this Error: DB2 SQL Error: SQLCODE=-302, SQLSTATE=22001 (Character data, right truncation occurred; for example, an update or insert value is a string that is too long for the column, or a datetime value cannot be assigned to a host variable, because it is too small.) I'm looking for solutions for DB2, MsSql, MySql, Hypersonic.

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