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msem_lock(3)							  msem_lock(3)

NAME
       msem_lock - Lock a semaphore

SYNOPSIS
       #include <sys/mman.h>

       int msem_lock(
	       msemaphore *sem,
	       int condition );

LIBRARY
       Standard C Library (libc)

PARAMETERS
       Points  to  an msemaphore structure which specifies the semaphore to be
       locked.	Determines whether the msem_lock() function waits for  a  cur‐
       rently locked semaphore to unlock.

DESCRIPTION
       The msem_lock() function attempts to lock a binary semaphore.

       If  the	semaphore  is  not  currently  locked,	it  is	locked and the
       msem_lock() function returns successfully.

       If the semaphore is currently locked, and the  condition	 parameter  is
       MSEM_IF_NOWAIT, then the msem_lock() function returns with an error. If
       the semaphore is currently locked, and the  condition  parameter	 is  0
       (zero),	then  msem_lock()  will	 not  return  until either the calling
       process is able to successfully lock the semaphore, or an error	condi‐
       tion occurs.

       All  calls to msem_lock() and msem_unlock() by multiple processes shar‐
       ing a common msemaphore structure behave as if the calls	 were  serial‐
       ized.

       If  the	msemaphore  structure  contains any value not resulting from a
       call to msem_init() followed by a (possibly empty) sequence of calls to
       msem_lock()  and	 msem_unlock(), the results are undefined. The address
       of an msemaphore structure may be significant. If the msemaphore struc‐
       ture  contains  any value copied from an msemaphore structure at a dif‐
       ferent address, the result is undefined.

NOTES
       Trial use

RETURN VALUES
       On successful completion, the msem_lock() function returns 0 (zero). On
       error,  the  msem_lock() function returns -1 and sets errno to indicate
       the error.

ERRORS
       If the msem_lock() function fails, errno may be set to one of the  fol‐
       lowing  values:	MSEM_IF_NOWAIT	was  specified	and  the semaphore was
       already locked.	The sem parameter points to  an	 msemaphore  structure
       which  specifies	 a  semaphore which has been removed, or the condition
       parameter is invalid.  The msem_lock() function was  interrupted	 by  a
       signal which was caught.

SEE ALSO
       Functions: msem_init(3), msem_remove(3), msem_unlock(3)

								  msem_lock(3)
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