How to program thread in Unix OS??

I use KDevelop(2.1) and write a very simple program below:
#include
#include
#include
#include
void *Dosomething(void* arg)
{
char* str = (char*)agr;
printf(“%s”,str);
pthread_exit(NULL);
}

int main(int argc, char *argv[])
{

pthread_t p_thread;
char *agr = “Hello world”;
pthread_create(&p_thread,NULL, Dosomething,(void*)agr);

return EXIT_SUCCESS;
}

But when I debug the program, I have a serious error. I set a break point in a line 'pthread_create(...);' then start debugging. But the compiler notifies me with a message 'gdb message: Program received signal SIGSEGV,Segmentation fault '. The program is so simple that i can't understand the error. So i need some helps to solve this problem. I also need some documents to program with thread in Linux(Unix) environment.

Thanks very much for yours helps.

http://www.linuxquestions.org/questi...threadid=42910

do not ask the same question more than once, for any reason.

Moved, much more appropriate in Programming, also Crabby if you see this one, you might want to merge in the double post from Newbie.

Cheers,

Finegan