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  • Generating random numbers in C

    - by moonstruckhorrors
    While searching for Tutorials on generating random numbers in C I found This Topic When I try to use the rand() function with parameters, I always get the random number generated 0. When I try to use the rand() function with parameters, I always get the value 41. And whenever I try to use arc4random() and random() functions, I get a LNK2019 error. Here's what I'm doing: #include <stdlib.h> int main() { int x; x = rand(6); printf("%d", x); } This code always generate 41. Where am I going wrong?? P.S. : I'm running Windows XP SP3 and using VS2010 Command Prompt as compiler. P.P.S. : Took me 15 minutes to learn how to format properly.

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  • how to callback a lua function from a c function

    - by pierr
    Hi, I have a c function test_callback accepting a point to a function as the parameter and It will "callback" that function. //typedef int(*data_callback_t)(int i); int test_callback(data_callback_t f) { f(3); } int datacallback(int a ) { printf("called back %d\n",a); return 0; } //example test_callback(datacallback); // print : called back 3 Now, I want to wrap test_callback so that they can be called from lua, suppose the name is lua_test_callback ;and also the input parameter to it would be a lua function. How should I achieve this goal? function lua_datacallback (a ) print "hey , this is callback in lua" ..a end lua_test_callback(lua_datacallback) //expect to get "hey this is callback in lua 3 "

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  • problem with the programme!!

    - by hopefulLLl
    kindly tell me what is the pblm with this function wont it help me find the sum of digits of a number?? #include<stdio.h> #include(math.h) void main() { int a,i=0,j=10,k,n=0,m; scanf("%d",&a); while((a%j!=0)&&i>=0) { m=pow(10,(i+1)); k=a%m; n=(a-(k*m)-n)/(m/10)+n; j=m*10; i++; } n=n+(n/(m/10)); printf("%d",n); } i know the parenthesis used with math.h are nt right..what else is the pblm..i need to use just while loop..or the for loop!

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  • How do I compile for windows XP under windows 7 / visual studio 2008

    - by Jon Cage
    I'm running Windows 7 and Visual Studio 2008 Pro and trying to get my application to work on Windows XP SP3. It's a really minimal command line program so should have any ridiculous dependencies: // XPBuild.cpp : Defines the entry point for the console application. // #include "stdafx.h" int _tmain(int argc, _TCHAR* argv[]) { printf("Hello world"); getchar(); return 0; } I read somewhere that defining several constants such as WINVER should allow me to compile for other platforms. I've tried the added the following to my /D compiler options: ;WINVER=0x0501;_WIN32_WINNT 0x0501;NTDDI_VERSION=NTDDI_WINXP But that made no difference. When I run it on my Windows XP machine (actually running in a virtualbox) I get the following error: This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem. So what have I missed? Is there something else required to run MSVC compiled programs or a different compiler option or something else?

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  • Force line-buffering of stdout when piping to tee

    - by houbysoft
    Usually, stdout is line-buffered. In other words, as long as your printf argument ends with a newline, you can expect the line to be printed instantly. This does not appear to hold when using a pipe to redirect to tee. I have a C++ program, a, that outputs strings, always \n-terminated, to stdout. When it is run by itself (./a), everything prints correctly and at the right time, as expected. However, if I pipe it to tee (./a | tee output.txt), it doesn't print anything until it quits, which defeats the purpose of using tee. I know that I could fix it by adding a fflush(stdout) after each printing operation in the C++ program. But is there a cleaner, easier way? Is there a command I can run, for example, that would force stdout to be line-buffered, even when using a pipe?

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  • Linux issues on setting a timer function

    - by laura
    I am creating a process with 2 children, 1 of the children is responsible to read questions (line by line from a file), output every question and reading the answer, and the other one is responsable to measure the time elapsed and notify the user at each past 1 minute about the remaining time. My problem is that i couldn't find any useful example of how i can make this set time function to work. Here is what i have tried so far. The problem is that it outputs the same elapsed time every time and never gets out from the loop. #include<time.h> #define T 600000 int main(){ clock_t start, end; double elapsed; start = clock(); end = start + T; while(clock() < end){ elapsed = (double) (end - clock()) / CLOCKS_PER_SEC; printf("you have %f seconds left\n", elapsed); sleep(60); } return 0; }

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  • How to run an exe using c prog

    - by Ujjwal
    Hi All, I am new to this forum. I am in need of a program in C that runs an exe file in Windows. While googling I found the code below : 1. Code: #include<stdlib.h> #include<stdio.h> int main() { (void)system("C:\\Windows\\notepad.exe"); return 0; } The above code compiles successfully in Borland Turbo C. But it fails to run Notepad. 2 Code: #include<stdlib.h> #include<stdio.h> void main() { int result ; result=system("C:\\Windows\\notepad.exe"); printf("%d",result); } The above code on running gives -1 as output. Why am I getting -1. My OS Windows XP Borland Turbo C Compiler Please help.

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  • error handling strategies in C?

    - by Leo
    Given the code below: typedef struct {int a;} test_t; arbitrary_t test_dosomething(test_t* test) { if (test == NULL) { //options: //1. print an error and let it crash //e.g. fprintf(stderr, "null ref at %s:%u", __FILE__, __LINE__); //2. stop the world //e.g. exit(1); //3. return (i.e. function does nothing) //4. attempt to re-init test } printf("%d", test->a); //do something w/ test } I want to get a compiler error if test is ever NULL, but I guess that's not possible in C. Since I need to do null checking at runtime, what option is the most proper way to handle it?

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  • Unix Sockets in Go

    - by marketer
    I'm trying to make a simple echo client and server that uses Unix sockets. In this example, the server can receive data from the client, but it can't send the data back. If I use tcp connections instead, it works great: Server package main import "net" import "fmt" func echoServer(c net.Conn) { for { buf := make([]byte, 512) nr, err := c.Read(buf) if err != nil { return } data := buf[0:nr] fmt.Printf("Received: %v", string(data)) _, err = c.Write(data) if err != nil { panic("Write: " + err.String()) } } } func main() { l, err := net.Listen("unix", "/tmp/echo.sock") if err != nil { println("listen error", err.String()) return } for { fd, err := l.Accept() if err != nil { println("accept error", err.String()) return } go echoServer(fd) } } Client package main import "net" import "time" func main() { c,err := net.Dial("unix","", "/tmp/echo.sock") if err != nil { panic(err.String()) } for { _,err := c.Write([]byte("hi\n")) if err != nil { println(err.String()) } time.Sleep(1e9) } }

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  • Can this example be done with pointers instead of global variable?

    - by Louise
    This is a simplified example of the problem I have: #include <stdio.h> #include <stdlib.h> void f2(int** a) { printf("a: %i\n", **a); } void f1(int* a) { f2(&a); } int main() { int a = 3; f1(&a); // prints "a: 3" f2(???); return 0; } The problem is that I would like to be able to use f2() both in main() and in f1(). Can that be done without using global variables?

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  • Should I use implicit conversions to enforce preconditions?

    - by Malvolio
    It occurs to me that I could use use implicit conversions to both announce and enforce preconditions. Consider this: object NonNegativeDouble { implicit def int2nnd(d : Double) : NonNegativeDouble = new NonNegativeDouble(d) implicit def nnd2int(d : NonNegativeDouble) : Double = d.v def sqrt(n : NonNegativeDouble) : NonNegativeDouble = scala.math.sqrt(n) } class NonNegativeDouble(val v : Double ) { if (v < 0) { throw new IllegalArgumentException("negative value") } } object Test { def t1 = { val d : Double = NonNegativeDouble.sqrt(3.0); printf("%f\n", d); val n : Double = NonNegativeDouble.sqrt(-3.0); } } Ignore for the moment the actual vacuity of the example: my point is, the subclass NonNegativeDouble expresses the notion that a function only takes a subset of the entire range of the class's values. First is this: A good idea, a bad idea, or an obvious idea everybody else already knows about Second, this would be most useful with basic types, like Int and String. Those classes are final, of course, so is there a good way to not only use the restricted type in functions (that's what the second implicit is for) but also delegate to all methods on the underlying value (short of hand-implementing every delegation)?

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  • CryptGenRandom to generate asp.net session id

    - by DoDo
    Hi! does anyone have working example of CryptGenrRandom class to generate session id (need to use in my iis module). HCRYPTPROV hCryptProv; BYTE pbData[16]; if(CryptAcquireContext( &hCryptProv, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) { if(CryptGenRandom(hCryptProv, 8, pbData)) { std::string s(( const char *) pbData); printf(s.c_str()); } else { MyHandleError("Error during CryptGenRandom."); } } else { MyHandleError("Error during CryptAcquireContext!\n"); } i tried this code but, its not working quite well (i get it from msdn) and this example don't work for me ( http://www.codeproject.com/KB/security/plaintextsessionkey.aspx ) so if anyone know how to generate sessionid using this class plz let me know tnx anyway!

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  • How can I access a global pointer outside of a C function?

    - by patrick
    I am trying to access the data of*tkn within a different function in my program for example: putchar(*tkn); It is a global variable but its not working correctly. Any ideas? #define MAX 20 // globals char *tkn; char array[MAX]; ... void tokenize() { int i = 0, j = 0; char *delim = " "; tkn = strtok (str," "); // get token 1 if (tkn != NULL) { printf("token1: "); while ((*tkn != 0) && (tkn != NULL)) { putchar(*tkn); array[i] = *tkn; *tkn++; i++; } } }

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  • How to return a string literal from a function

    - by skydoor
    Hi I am always confused about return a string literal or a string from a function. I was told that there might be memory leak because you don't know when the memory will be deleted? For example, in the code below, how to implement foo() so that make the output of the code is "Hello World"? void foo ( ) // you can add parameters here. { } int main () { char *c; foo ( ); printf ("%s",c); return 0; } Also if the return type of foo() is not void, but you can return char*, what should it be.

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  • Treat a void function as a value

    - by Brendan Long
    I'm writing some terrible, terrible code, and I need a way to put a free() in the middle of a statement. The actual code is: int main(){ return printf("%s", isPalindrome(fgets(malloc(1000), 1000, stdin))?"Yes!\n":"No!\n") >= 0; // leak 1000 bytes of memory } I was using alloca(), but I can't be sure that will actually work on my target computer. My problem is that free returns void, so my code has this error message: error: void value not ignored as it ought to be The obvious idea I had was: int myfree(char *p){ free(p); return 0; } Which is nice in that it makes the code even more unreadable, but I'd prefer not to add another function. I also briefly tried treating free() as a function pointer, but I don't know if that would work, and I don't know enough about C to do it properly. Note: I know this is a terrible idea. Don't try this at home kids.

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  • Elegant way for a recursive C++ template to do something different with the leaf class?

    - by Costas
    I have a C++ class template that makes an Array of pointers. This also gets typedefed to make Arrays of Arrays and so on: typedef Array<Elem> ElemArray; typedef Array<ElemArray> ElemArrayArray; typedef Array<ElemArrayArray> ElemArrayArrayArray; I would like to be able to set one leaf node from another by copying the pointer so they both refer to the same Elem. But I also want to be able to set one Array (or Array of Arrays etc) from another. In this case I don't want to copy the pointers, I want to keep the arrays seperate and descend into each one until I get to the leaf node, at where I finally copy the pointers. I have code that does this (below). When you set something in an Array it calls a CopyIn method to do the copying. But because this is templated it also has to call the CopyIn method on the leaf class, which means I have to add a dummy method to every leaf class that just returns false. I have also tried adding a flag to the template to tell it whether it contains Arrays or not, and so whether to call the CopyIn method. This works fine - the CopyIn method of the leaf nodes never gets called, but it still has to be there for the compile to work! Is there a better way to do this? #include <stdio.h> class Elem { public: Elem(int v) : mI(v) {} void Print() { printf("%d\n",mI); } bool CopyIn(Elem *v) { return false; } int mI; }; template < typename T > class Array { public: Array(int size) : mB(0), mN(size) { mB = new T* [size]; for (int i=0; i<mN; i++) mB[i] = new T(mN); } ~Array() { for (int i=0; i<mN; i++) delete mB[i]; delete [] mB; } T* Get(int i) { return mB[i]; } void Set(int i, T* v) { if (! mB[i]->CopyIn(v) ) { // its not an array, so copy the pointer mB[i] = v; } } bool CopyIn(Array<T>* v) { for (int i=0; i<mN; i++) { if (v && i < v->mN ) { if ( ! mB[i]->CopyIn( v->mB[i] )) { // its not an array, so copy the pointer mB[i] = v->mB[i]; } } else { mB[i] = 0; } } return true; // we did the copy, no need to copy pointer } void Print() { for (int i=0; i<mN; i++) { printf("[%d] ",i); mB[i]->Print(); } } private: T **mB; int mN; }; typedef Array<Elem> ElemArray; typedef Array<ElemArray> ElemArrayArray; typedef Array<ElemArrayArray> ElemArrayArrayArray; int main () { ElemArrayArrayArray* a = new ElemArrayArrayArray(2); ElemArrayArrayArray* b = new ElemArrayArrayArray(3); // In this case I need to copy the pointer to the Elem into the ElemArrayArray a->Get(0)->Get(0)->Set(0, b->Get(0)->Get(0)->Get(0)); // in this case I need go down through a and b until I get the to Elems // so I can copy the pointers a->Set(1,b->Get(2)); b->Get(0)->Get(0)->Get(0)->mI = 42; // this will also set a[0,0,0] b->Get(2)->Get(1)->Get(1)->mI = 96; // this will also set a[1,1,1] // should be 42,2, 2,2, 3,3, 3,96 a->Print(); }

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  • Ajax / GroovyGrails Post data coming over with unexpected leading character. Who is encoding/decod

    - by ?????
    I'm having an encoding issue, and I'm not sure where to look for the problem. I have this Ajax.Request function (prototype library) sending data to a Groovy/Grails encoder var myAjax = new Ajax.Request(url, {method:'post', encoding:'UTF-8', contentType:'application/x-www-form-urlencoded', parameters:{'content':new_content}, onSuccess:success, onFailure:failure}); The data is coming in with an unexpected %A0 at the beginning: I have this simple controller that just echos the content back: def titlechange = { def content = URLDecoder.decode(params['content']) printf("Content: %s; DecodedContent = %s\n", params['content'], content) response.characterEncoding='UTF-8' render content } the debug print statement shows: Content: %A0Hello%2C%20world%21; DecodedContent = †Hello, world! Where is that %A0 coming from? My grails configuration has this: // The default codec used to encode data with ${} grails.views.default.codec="none" // none, html, base64 grails.views.gsp.encoding="UTF-8" grails.converters.encoding="UTF-8 Is the issue on the grails side or on the JavaScript side?

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  • How do I get Java to parse and format a date/time with the same time zone? I keep getting the local timezone

    - by fishtoprecords
    My application keeps all Java Date's in UTC. Parsing them is easy, but when I print them out, the display shows the computer's local time zone, and I want to show it as UTC. Example code: String sample = "271210 200157 UTC"; SimpleDateFormat dfmt = new SimpleDateFormat("ddMMyy HHmmss Z"); Date result = dfmt.parse(sample); System.out.printf("%tc\n", result); the result is Mon Dec 27 15:01:57 EST 2010 What I want is Mon Dec 27 20:01:57 UTC 2010 Clearly I have to set some Locale and TimeZone values, but I don't see where to put them. Thanks Pat

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  • How to integrate an open source C program instead of calling its executable through a system call?

    - by ihamer
    I have an executable (fossil scm) that is being invoked by my program externally through ::CreateProcess windows call. The stdout and stderr are then captured. Since the source code for fossil is available, I would prefer to create a static library out of it and issue calls directly. Currently, communication to fossil is done through the command line parameters, and the communication back is through the process return code, stdout and stderr. Fossil writes to stdout/err through printf and fprintf calls. What is the best way to solve this with minimum alteration of fossil source? Is there a reliable and cross-platform way to intercept stdout/err and send it into a memory buffer?

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  • Usage of atoi in the c language

    - by maddy
    I don't understand the results of the following C code. main() { char s[] = "AAA"; advanceString(s); } void advanceString(p[3]) { int val = atoi(p); printf("The atoi val is %d\n",val); } Here the atoi val is shown as 0. But I could not figure out the exact reason. As per my understanding, it should be the summation of decimal equivalent of each values in the array.? Please correct me if I am wrong.

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  • how to parse from command line arguements in yacc ?

    - by user205688
    how to parse from command line arguements in yacc ? of course i undefined input in both lex & yacc and then wrote int input(void) { printf("in input\n:"); char c; if(target > limit) return 0; if((c = target[0][offset++]) != '\0') return (c); target++; offset =0; return (' '); } where target contains the command line arguements. But only the standard input is getting excueted how to make dis input function get executed.

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  • MPFR Rounding 0.9999 to 1?

    - by Silmaersti
    I'm attempting to store the value 0.9999 into an mpfr_t variable But 0.9999 is rounded to 1 (or some other value != 0.9999) during storage, no matter the round value (GMP_RNDD, GMP_RNDU, GMP_RNDN, GMP_RNDZ) So what's the best method to store 0.9999 in an mpfr_t variable? Is it possible? Here is my test program, it prints "buffer is: 1", instead of the wanted "buffer is: 0.9999": int main() { size_t precision = 4; mpfr_t mpfrValue; mpfr_init2(mpfrValue, precision); mpfr_set_str(mpfrValue, "0.9999", 10, GMP_RNDN); char *buffer = (char*)malloc((sizeof(char) * precision) + 3); mp_exp_t exponent; mpfr_get_str(buffer, &exponent, 10, precision, mpfrValue, GMP_RNDN); printf("buffer is: %s\n", buffer); free(buffer); mpfr_clear(mpfrValue); return 0; } Thanks for any help !

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  • Hiredis waiting for message

    - by Vivek Goel
    I am using hiredis C library to connect to redis server. I am not able to figure out how to wait for new messages after subscribing to new message. My code look like: signal(SIGPIPE, SIG_IGN ); struct event_base *base = event_base_new(); redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379); if (c->err) { /* Let *c leak for now... */ printf("Error: %s\n", c->errstr); return 1; } redisLibeventAttach(c, base); redisAsyncSetConnectCallback(c, connectCallback); redisAsyncSetDisconnectCallback(c, disconnectCallback); redisAsyncCommand(c, NULL, NULL, "SET key %b", argv[argc - 1], strlen(argv[argc - 1])); redisAsyncCommand(c, getCallback, (char*) "end-1", "GET key"); redisAsyncCommand(c, getCallback, (char*) "end-1", "SUBSCRIBE foo"); Now how to tell hiredis to wait for message on channel ?

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  • Copy a function in memory and execute it

    - by Elinghton
    Hi everybody, I would like to know how in C in can copy the content of a function into memroy and the execute it? I'm trying to do something like this: typedef void(*FUN)(int *); char * myNewFunc; char *allocExecutablePages (int pages) { template = (char *) valloc (getpagesize () * pages); if (mprotect (template, getpagesize (), PROT_READ|PROT_EXEC|PROT_WRITE) == -1) { perror ("mprotect"); } } void f1 (int *v) { *v = 10; } // allocate enough spcae but how much ?? myNewFunc = allocExecutablePages(...) /* Copy f1 somewere else * (how? assume that i know the size of f1 having done a (nm -S foo.o)) */ ((FUN)template)(&val); printf("%i",val); Thanks for your answers

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  • Why would I get a bus error or segmentation fault when calling free() normally?

    - by chucknelson
    I have a very simple test program, running on Solaris 5.8: #include <stdio.h> #include <stdlib.h> int main(void) { char *paths; paths = getenv("PATH"); printf("Paths: %s\n", paths); free(paths); // this causes a bus error return 0; } If I don't call free() at the end, it displays the message fine and exits. If I include the free() call, it crashes with a bus error. I've had other calls to free(), in other programs, cause segmentation faults as well. Even if I allocate the memory for *paths myself, free() will cause a bus error. Is there some reason trying to free up the memory is causing a crash?

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