sem_destroy(3) [php man page]

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

NAME

       sem_destroy - destroy an unnamed semaphore

SYNOPSIS

       #include <semaphore.h>

       int sem_destroy(sem_t *sem);

       Link with -pthread.

DESCRIPTION

       sem_destroy() destroys the unnamed semaphore at the address pointed to by sem.

       Only a semaphore that has been initialized by sem_init(3) should be destroyed using sem_destroy().

       Destroying a semaphore that other processes or threads are currently blocked on (in sem_wait(3)) produces undefined behavior.

       Using a semaphore that has been destroyed produces undefined results, until the semaphore has been reinitialized using sem_init(3).

RETURN VALUE

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

ERRORS

       EINVAL sem is not a valid semaphore.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       +--------------+---------------+---------+
       |Interface     | Attribute     | Value	|
       +--------------+---------------+---------+
       |sem_destroy() | Thread safety | MT-Safe |
       +--------------+---------------+---------+
CONFORMING TO

       POSIX.1-2001, POSIX.1-2008.

NOTES

       An  unnamed  semaphore  should be destroyed with sem_destroy() before the memory in which it is located is deallocated.	Failure to do this
       can result in resource leaks on some implementations.

SEE ALSO

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

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux								    2017-09-15							    SEM_DESTROY(3)

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)