sem_init(3rt) [sunos man page]

sem_init(3RT)						    Realtime Library Functions						     sem_init(3RT)

NAME

       sem_init - initialize an unnamed semaphore

SYNOPSIS

       cc [ flag... ] file... -lrt [ library... ]
       #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(3RT), sem_trywait(3RT), sem_post(3RT),
       and sem_destroy(3RT). 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(3RT), sem_trywait(3RT), sem_post(3RT), and sem_destroy(3RT) operations.

       Only sem itself may be used for performing synchronization. The result of referring to copies of sem in calls  to  sem_wait(3RT),  sem_try-
       wait(3RT), sem_post(3RT), and sem_destroy(3RT), 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(3RT), sem_trywait(3RT), sem_post(3RT), and sem_destroy(3RT) 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	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

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

SunOS 5.10							    28 Jun 2002 						     sem_init(3RT)

Check Out this Related Man Page

sem_getvalue(3RT)					    Realtime Library Functions						 sem_getvalue(3RT)

NAME

       sem_getvalue - get the value of a semaphore

SYNOPSIS

       cc [ flag... ] file... -lrt [ library... ]
       #include <semaphore.h>

       int sem_getvalue(sem_t *restrict sem, int *restrict sval);

DESCRIPTION

       The sem_getvalue() function updates the location referenced by the sval argument to have the value of the semaphore referenced by sem with-
       out affecting the state of the semaphore. The updated value represents an actual semaphore value that occurred  at  some  unspecified  time
       during the call, but it need not be the actual value of the semaphore when it is returned to the calling process.

       If  sem is locked, then the value returned by sem_getvalue() is either zero or a negative number whose absolute value represents the number
       of processes waiting for the semaphore at some unspecified time during the call.

       The value set in sval may be 0 or positive. If sval is 0, there may be other processes (or LWPs or threads) waiting for the  semaphore;	if
       sval is positive, no process is waiting.

RETURN VALUES

       Upon successful completion, sem_getvalue() returns 0. Otherwise, it returns -1 and sets errno to indicate the error.

ERRORS

       The  sem_getvalue() function will fail if:

       EINVAL	       The sem argument does not refer to a valid semaphore.

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

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       semctl(2), semget(2), semop(2), sem_post(3RT), sem_wait(3RT), attributes(5), standards(5)

SunOS 5.10							    1 Nov 2003							 sem_getvalue(3RT)

Linux and UNIX Man Pages

sem_init(3rt) [sunos man page]

Check Out this Related Man Page