Pass variable into pthread_create function - c

Question

I'm building a multi-threaded network chat program, but I can't figure out how to pass variables into pthread_create.
I have the following line of code that creates a thread:
pthread_create(&thread, NULL, receive, (void *) socket_fd);
My receive function looks like this:
void * receive(void * socket) {
int socket_fd, response;
char message[MESSAGE_BUFFER];
socket_fd = (int) socket;
while(true) {
response = recvfrom(socket_fd, message, MESSAGE_BUFFER, 0, NULL, NULL);
if (response) {
printf("\nServer> %s", message);
printf("%s", prompt);
}
}
}
How can I pass a prompt variable into this receive function, when calling receive in pthread_create?

Answer 1

You can pack all of the data you want to pass to your thread on creation in a single struct and pass its pointer through the last parameter of pthread_create. in short:
define a struct:
typedef struct{
char* prompt;
int socket;
} thread_data;
and then call pthread_create:
thread_data data;
// place code here to fill in the struct members...
pthread_create(&thread, NULL, receive, (void *) &data);
in your receive function:
void * receive(void * threadData) {
int socket_fd, response;
char message[MESSAGE_BUFFER];
thread_data* pData = (thread_data*)threadData;
socket_fd = pData->socket;
char* prompt = pData->prompt;
while(true) {
response = recvfrom(socket_fd, message, MESSAGE_BUFFER, 0, NULL, NULL);
if (response) {
printf("\nServer> %s", message);
printf("%s", prompt);
}
}
}
Hope this helps.