pthreadcreate

pthread_create is a function provided by the POSIX Threads (pthreads) library, used to create a new thread of execution in a program. The function is declared in the header <pthread.h> and has the following prototype: pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg). When called, the operating system creates a new thread, assigns it a unique thread identifier stored in thread, and begins execution at the function pointed to by start_routine. The start_routine function receives a single argument arg and typically returns a void pointer that can be retrieved via pthread_join.

The attr parameter allows specification of thread attributes such as stack size, scheduling policy, and detach state. If attr is NULL, default attributes are used. The thread is created in a joinable state unless the DETACHED attribute was set in attr; joinable threads must be waited on with pthread_join to reclaim resources, whereas detached threads do not require a join and free resources immediately upon termination.

pthread_create returns 0 on success. On failure, it returns an error number and the thread is not created. Common error codes include EAGAIN (insufficient resources), EINVAL (invalid attributes), and EPERM (insufficient permissions). Typical usage involves creating worker threads, performing background tasks, or parallelizing computations.

In practice, a program might spawn several worker threads with pthread_create, each performing a portion of a workload, and later use pthread_join to wait for their completion and collect return values. Proper synchronization primitives such as mutexes and condition variables are often used in conjunction to coordinate between threads and protect shared data.