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sem_init(2)							   sem_init(2)

NAME
       sem_init - initialize an unnamed POSIX semaphore

SYNOPSIS
DESCRIPTION
       is  used to initialize an unnamed semaphore.  A successful call to will
       create a new unnamed semaphore referred to by  sem,  if	one  does  not
       exist, initialize the unnamed semaphore descriptor, referred to by sem,
       to the non-negative value specified by value.  If the unnamed semaphore
       already exists, i.e. created by a previous call to it is re-initialized
       only if its current value is equal to its initial  value	 (set  by  the
       last  successful	 call to If so, the initial value of the unnamed sema‐
       phore is re-initialized to the  value  argument.	 Otherwise,  the  call
       fails.

       The  argument  pshared  specifies  if the unnamed semaphore is sharable
       with other processes. If pshared is equal to 0, the  unnamed  semaphore
       is  not	shared	with  other  processes.	  If  pshared is non-zero, the
       unnamed semaphore is sharable with any processes that can  access  sem.
       The  access  mode  specified  for the unnamed semaphore allows read and
       write permissions to all processes.  If the calling process may	attach
       to the shared structure, it is assumed it may operate on the semaphore.

       To use this function, link in the realtime library by specifying on the
       compiler or linker command line.

EXAMPLES
       The following call to will create a new unnamed semaphore  referred  to
       by  sem,	 if  one  does	not  exist,  initialize	 the unnamed semaphore
       descriptor, referred to by sem, to the non-negative value specified  by
       value.

RETURN VALUE
       If the semaphore was created and initialized, returns 0 to the caller.

       If  the semaphore could not be created/initialized, the call returns -1
       and sets to indicate the error.

ERRORS
       fails and does not perform the requested operation if any of  the  fol‐
       lowing conditions are encountered:

	      [EPERM]	     The  calling process does not have the privileges
			     necessary to initialize the semaphore.

	      [EBUSY]	     There are threads currently blocked on the	 sema‐
			     phore  or there are outstanding locks held on the
			     semaphore.

	      [EINVAL]	     The argument value is greater than

	      [ENOSPC]	     There are insufficient resources to  perform  the
			     operation	or  the	 upper	limit on the number of
			     semaphores is reached.

SEE ALSO
       sem_destroy(2),	sem_post(2),   sem_trywait(2),	 sem_wait(2),	<sema‐
       phore.h>.

STANDARDS CONFORMANCE
								   sem_init(2)

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