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Realtime Library Functionssem_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_trywait(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 TYPEATTRIBUTE VALUE
MT-LevelMT-Safe

SEE ALSO

 

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


SunOS 5.9Go To TopLast Changed 22 Jun 1998

 
      
      
Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.