THREADS IN POSIX

To find out if an operating system might support the POSIX®.1 specification, ask "Does it support the fork() call?"

Fork() calls are scattered throughout Unix®/Linux® code. To support fork(), an operating system must first support the concept of parent-child relationships between processes. If fork() and other common POSIX.1 calls are not supported, the vast majority of your Unix/Linux code will not port to that operating system without major rewrites.

Understanding fork()

The fork() system call creates a new process called a child. The original process is called the parent, and the child is a near-exact copy of the parent. The child's run time is set to zero and file locks are not inherited.

The child has its own process ID and its own copy of the parent's file descriptors.

A parent process can recover the exit status of a child using the wait() or waitpid() function.

"But is it POSIX-conformant?"

POSIX for embedded developers What is POSIX? POSIX.1, .1b and .1c POSIX Function Calls Reference Processes and Virtual Memory Parent-Child Processes Threads in POSIX Signals in POSIX LynxOS: POSIX-conformant RTOS POSIX PDF BROCHURE (170 kB) POSIX TRAINING: Real-time system course O'REILLY PROGRAMMING GUIDES for LynuxWorks operating systems POSIX Programmers Guide Pthreads Programming POSIX.4 Programmers Guide A savvy engineer just needs to ask a few quick questions about an operating system in order to determine if it might fully support the POSIX standards. "Does each process in the operating system reside in a different name space and have its own symbols table? "Does the operating system support the fork() call?" "Can the operating system distinguish between threads and processes?" "Does the operating system support signals?"

THREADS IN POSIX