msem_lock(3)						     Library Functions Manual						      msem_lock(3)

NAME

       msem_lock - Locks a semaphore

LIBRARY

       Standard C Library (libc.a)

SYNOPSIS

       #include <sys/mman.h>
       int msem_lock (	    msemaphore *sem,	  int condition );

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 condition occurs.

       All calls to msem_lock() and msem_unlock() by multiple processes sharing 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
       structure contains any value copied from an msemaphore structure at a different 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 indi-
       cate the error.

ERRORS

       If the msem_lock() function fails, errno may be set to one of the following 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.

RELATED INFORMATION

       Functions: msem_init(3), msem_remove(3), msem_unlock(3) delim off

																      msem_lock(3)