sem_init man page on Archlinux

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SEM_INIT(3)		   Linux Programmer's Manual		   SEM_INIT(3)

       sem_init - initialize an unnamed semaphore

       #include <semaphore.h>

       int sem_init(sem_t *sem, int pshared, unsigned int value);

       Link with -pthread.

       sem_init()  initializes the unnamed semaphore at the address pointed to
       by sem.	The value argument specifies the initial value for  the	 sema‐

       The  pshared  argument indicates whether this semaphore is to be shared
       between the threads of a process, or between processes.

       If pshared has the value 0, then the semaphore is  shared  between  the
       threads	of  a  process,	 and should be located at some address that is
       visible to all threads (e.g., a global variable, or  a  variable	 allo‐
       cated dynamically on the heap).

       If  pshared is nonzero, then the semaphore is shared between processes,
       and should be located in a region of shared  memory  (see  shm_open(3),
       mmap(2),	 and  shmget(2)).   (Since a child created by fork(2) inherits
       its parent's memory mappings, it can also access the  semaphore.)   Any
       process	that  can  access  the shared memory region can operate on the
       semaphore using sem_post(3), sem_wait(3), and so on.

       Initializing a semaphore that has already been initialized  results  in
       undefined behavior.

       sem_init() returns 0 on success; on error, -1 is returned, and errno is
       set to indicate the error.

       EINVAL value exceeds SEM_VALUE_MAX.

       ENOSYS pshared is nonzero, but the system  does	not  support  process-
	      shared semaphores (see sem_overview(7)).

   Multithreading (see pthreads(7))
       The sem_init() function is thread-safe.


       Bizarrely,  POSIX.1-2001	 does  not  specify  the  value that should be
       returned by a successful call to	 sem_init().   POSIX.1-2008  rectifies
       this, specifying the zero return on success.

       sem_destroy(3), sem_post(3), sem_wait(3), sem_overview(7)

       This  page  is  part of release 3.65 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at

Linux				  2014-03-10			   SEM_INIT(3)

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