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sem_post(3)

NAME

     sem_post -- increment (unlock) a semaphore

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <semaphore.h>

     int
     sem_post(sem_t *sem);

DESCRIPTION

     The sem_post() function increments (unlocks) the semaphore pointed to by
     sem.  If there are threads blocked on the semaphore when sem_post() is
     called, then the highest priority thread that has been blocked the long-
     est on the semaphore will be allowed to return from sem_wait().

     The sem_post() function is signal-reentrant and may be called within sig-
     nal handlers.

RETURN VALUES

     The sem_post() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS

     The sem_post() function will fail if:

     [EINVAL]		The sem argument points to an invalid semaphore.

SEE ALSO

     sem_trywait(3), sem_wait(3), sem(4)

STANDARDS

     The sem_post() function conforms to ISO/IEC 9945-1:1996 (``POSIX.1'').

FreeBSD 5.4		       February 15, 2000		   FreeBSD 5.4

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