msem_lock - Lock a semaphore
int condition );
Standard C Library (libc)
Points to an msemaphore structure which specifies the
semaphore to be locked. Determines whether the
msem_lock() function waits for a currently locked
semaphore to unlock.
The msem_lock() function attempts to lock a binary
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 serialized.
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.
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.
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.
Functions: msem_init(3), msem_remove(3), msem_unlock(3)
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