pthread

除了要#include <pthread.h>
編譯的時候還要下-pthread指令

ex:gcc test.c -o test -pthread

pthread_create(pid,NULL,*void,(*void)arg);
第三項是pthread要跑的function位置，這個function只能接受一個argument傳入，限定為void type，有需求傳入多個arguments時，定一個struct把需要的arguments都包起來。可以回傳值，所以也限定為void*，因此function定義時要定成void* mydeffunc(void* arg)

ex:


void *doit(void *arg);

/*define a struct to wrap needed arguments*/
struct myDefStruct
{
struct sockaddr_in servaddr;
int sockfd;
};

/*call pthread_create的時候*/
/*when call pthread_create*/
struct myDefStruct *myDefPtr;
for ( ; ; ) {
clilen = sizeof(cliaddr);
connfd = accept(listenfd, (__SOCKADDR_ARG) &cliaddr, &clilen);
myDefPtr= (struct myDefStruct*)malloc(sizeof(struct myDefStruct));
myDefPtr->servaddr = cliaddr;
myDefPtr->sockfd = connfd;
pthread_create(&tid, NULL, &doit, (void*)myDefPtr);
 }


/*如何取出void*型別的資訊*/
/*How to retrieve the data in void* type by casting*/
void *doit(void *arg)
{
int sockfd = ((struct myDefStruct*)arg)->sockfd;
struct sockaddr_in servaddr = ((struct myDefStruct*)arg)->servaddr;
...............
}