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pthread_mutex_init(3)
NAME
  pthread_mutex_init - Initializes a mutex with attributes specified by the
  attr argument.

LIBRARY
  DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS
  #include <pthread.h>

  int	pthread_mutex_init(
			pthread_mutex_t	  *mutex,
			const pthread_mutexattr_t *attr);

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS
  mutex	    Mutex created.

  attr	    Mutex attributes object to be used to initialize the
	    characteristics of the created mutex.

DESCRIPTION
  This routine initializes a mutex with the attributes specified by the mutex
  attributes object specified in the attr argument.  A mutex is a
  synchronization object that allows multiple threads to serialize their
  access to shared data.


  The mutex is initialized and set to the unlocked state.  If attr is set to
  NULL, the default mutex attributes are used.	The
  pthread_mutexattr_settype(3) routine can be used to specify the type of
  mutex that is created (normal, recursive, or errorcheck).

  A mutex is a resource of the process, not part of any particular thread.  A
  mutex is neither destroyed nor unlocked automatically when any thread
  exits.  Because mutexes are shared, they may be allocated in heap or static
  memory, but not on a stack.

  Use the PTHREAD_MUTEX_INITIALIZER macro to statically initialize a mutex
  without calling this routine.	 Statically initialized mutexes need not be
  destroyed using pthread_mutex_destroy(3).  Use this macro as follows:

  pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER

  Only normal mutexes can be statically initialized.



RETURN VALUES
  If an error condition occurs, this routine returns an integer value
  indicating the type of error, the mutex is not initialized, and the
  contents of mutex are undefined.  Possible return values are as follows:

  0	    Successful completion.

  [EAGAIN]  The system lacks the necessary resources to initialize the mutex.

  [ENOMEM]  Insufficient memory exists to initialize the mutex.

  [EBUSY]   The implementation has detected an attempt to reinitialize the
	    mutex (a previously initialized, but not yet destroyed mutex).

  [EINVAL]  The value specified by mutex is invalid.

  [EPERM]   The caller does not have privileges to perform the operation.

ERRORS
  None

RELATED INFORMATION
  Functions: pthread_mutexattr_init(3), pthread_mutexattr_gettype(3),
  pthread_mutexattr_settype(3), pthread_mutex_lock(3),
  pthread_mutex_trylock(3), pthread_mutex_unlock(3)

  Manuals: Guide to DECthreads and Programmer's Guide