How to create a Thread using C Programming

We know that Linux or Unix systems are multi-user and multi-tasking environments. Hence the processes in these environments can cooperate with each other. In a multi-threaded system, generally, threads share a segment of memory instead of allocating memory for each thread separately.

Advantages of Threads

• It is useful to design a program to do multiple tasks simultaneously.
• It improves the performance of the application by utilizing multiple processor cores.
• In the case of context switching, thread switching requires the lesser effort from the operating system compared to process switching.

Drawbacks of Threads

• The designer of a thread should be very careful otherwise it may create a huge problem due to memory sharing.
• Debugging is very hard.
• On a single processor system, the use of threads does not give any benefit.

In the following program, we have shown how to create a thread. First, we have defined a function, my_thread_function, which we want to run a thread.

The function pthread_create creates a thread taking my_thread_function as an argument.

Program to handle thread (mythreadtest.c)

#include <pthread.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <unistd.h> void *my_thread_function(void *arg); char msg[] = "My First Thread Program"; int main(void) { pthread_t mythread; void *thread_result; if (pthread_create(&mythread, NULL, my_thread_function, (void *)msg)) { printf("Error in creating a thread!"); exit(EXIT_FAILURE); } printf("Waiting for the thraed to finish...."); if (pthread_join(mythread, &thread_result)) { printf("Error in joining this thread!"); exit(EXIT_FAILURE); } printf("Thread joined successfully and it returned %s\n", (char *)thread_result); printf("Message is %s\n", msg); exit(EXIT_SUCCESS); } void *my_thread_function(void *arg) { int i; printf("my_thread_function has been started. Argument is %s\n", (char *)arg); for (i = 0; i < 5; i++) { printf("I am in a thread!\n"); sleep(1); strcpy(msg, "Bye!"); } pthread_exit("my_thread_function is being completed."); }

Compile it as

$ gcc mythreadtest.c -o mythreadtest -lpthread

Run it as

$ ./mythreadtest

Happy Exploring!