Now it is time to look at multi-threaded processes. The programming interface for threads is the POSIX threads API, which was first defined in IEEE POSIX 1003.1c standard (1995), commonly known as Pthreads. It was implemented as an additional part of the C library,
libpthread.so. There have been two versions of Pthreads over the last 15 years or so, Linux Threads and the Native POSIX Thread Library (NPTL). The latter is much more compliant with the specification, particularly with regard to the handling of signals and process IDs. It is pretty dominant now, but you may come across some older versions of uClibc that use Linux Threads.
The function to create a thread is
int pthread_create(pthread_t *thread, ...