sem_init(3c) [opensolaris man page]

sem_init(3C)						   Standard C Library Functions 					      sem_init(3C)

NAME

       sem_init - initialize an unnamed semaphore

SYNOPSIS

       #include <semaphore.h>

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

DESCRIPTION

       The  sem_init()	function  is used to initialize the unnamed semaphore referred to by sem. The value of the initialized semaphore is value.
       Following a successful call to sem_init(), the semaphore may be used in subsequent calls to  sem_wait(3C),  sem_trywait(3C),  sem_post(3C),
       and sem_destroy(3C). This semaphore remains usable until the semaphore is destroyed.

       If the pshared argument has a non-zero value, then the semaphore is shared between processes; in this case, any process that can access the
       semaphore sem can use sem for performing sem_wait(3C), sem_trywait(3C), sem_post(3C), and sem_destroy(3C) operations.

       Only sem itself may be used for performing synchronization. The result of referring to copies of sem in	calls  to  sem_wait(3C),  sem_try-
       wait(3C), sem_post(3C), and sem_destroy(3C), is undefined.

       If  the	pshared  argument is zero, then the semaphore is shared between threads of the process; any thread in this process can use sem for
       performing sem_wait(3C), sem_trywait(3C), sem_post(3C), and sem_destroy(3C) operations. The use of the  semaphore  by  threads  other  than
       those created in the same process is undefined.

       Attempting to initialize an already initialized semaphore results in undefined behavior.

RETURN VALUES

       Upon successful completion, the function initializes the semaphore in sem. Otherwise, it returns -1 and sets errno to indicate the error.

ERRORS

       The sem_init() function will fail if:

       EINVAL	  The value argument exceeds  SEM_VALUE_MAX.

       ENOSPC	  A  resource  required  to  initialize  the  semaphore  has been exhausted, or the resources have reached the limit on semaphores
		  (SEM_NSEMS_MAX).

       ENOSYS	  The sem_init() function is not supported by the system.

       EPERM	  The process lacks the appropriate privileges to initialize the semaphore.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |ATTRIBUTE TYPE		     |ATTRIBUTE VALUE		   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sem_destroy(3C), sem_post(3C), sem_wait(3C), attributes(5), standards(5)

SunOS 5.11							    5 Feb 2008							      sem_init(3C)

Check Out this Related Man Page

sem_init(2)							System Calls Manual						       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 sema-
       phore  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 semaphore 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 following 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 semaphore 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), <semaphore.h>.

STANDARDS CONFORMANCE

																       sem_init(2)

Linux and UNIX Man Pages

sem_init(3c) [opensolaris man page]

Check Out this Related Man Page