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NAME    [Toc]    [Back]

     sem_init - initialize an unnamed semaphore

SYNOPSIS    [Toc]    [Back]

     #include <semaphore.h>

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

DESCRIPTION    [Toc]    [Back]

     The sem_init() function initializes  the  unnamed  semaphore
pointed to by
     sem  to  have the value value.  A non-zero value for pshared
specifies a
     shared semaphore that can be  used  by  multiple  processes,
which this implementation
 is not capable of.

     Following  a  successful call to sem_init(), sem can be used
as an argument
     in subsequent calls to sem_wait, sem_trywait, sem_post,  and
     sem   is   no  longer  valid  after  a  successful  call  to

RETURN VALUES    [Toc]    [Back]

     The sem_init() function returns the value 0  if  successful;
otherwise the
     value -1 is returned and the global variable errno is set to
indicate the

ERRORS    [Toc]    [Back]

     sem_init() will fail if:

     [EINVAL]      value exceeds SEM_VALUE_MAX.

     [ENOSPC]      Memory allocation error.

     [EPERM]       Unable to initialize a shared semaphore.

SEE ALSO    [Toc]    [Back]

     sem_destroy(3), sem_post(3), sem_trywait(3), sem_wait(3)

STANDARDS    [Toc]    [Back]

     sem_init() conforms to ISO/IEC 9945-1:1996 (``POSIX'').

     This implementation does not support shared semaphores,  and
reports this
     fact  by  setting errno to EPERM.  This is perhaps a stretch
of the intention
 of POSIX,  but  is  compliant,  with  the  caveat  that
sem_init() always
     reports  a  permissions  error  when  an attempt to create a
shared semaphore
     is made.

OpenBSD     3.6                        February     15,      2000
[ Back ]
 Similar pages
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sem_init Tru64 Initializes an unnamed semaphore (P1003.1b)
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sem_getvalue IRIX get the value of a posix named or unnamed semaphore
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