sem_post(3) [netbsd man page]

SEM_POST(3)						   BSD Library Functions Manual 					       SEM_POST(3)

NAME

     sem_post -- increment (unlock) a semaphore

LIBRARY

     POSIX Real-time Library (librt, -lrt)

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 longest on the semaphore will be allowed to return from sem_wait().

     sem_post() is signal-reentrant and may be called within signal 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 indi-
     cate the error.

ERRORS

     sem_post() will fail if:

     [EINVAL]		sem points to an invalid semaphore.

SEE ALSO

     sem_trywait(3), sem_wait(3)

STANDARDS

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

BSD
								 January 22, 2003							       BSD

SEM_POST(3)						     Linux Programmer's Manual						       SEM_POST(3)

NAME

       sem_post - unlock a semaphore

SYNOPSIS

       #include <semaphore.h>

       int sem_post(sem_t *sem);

       Link with -lrt or -pthread.

DESCRIPTION

       sem_post()  increments  (unlocks)  the  semaphore pointed to by sem.  If the semaphore's value consequently becomes greater than zero, then
       another process or thread blocked in a sem_wait(3) call will be woken up and proceed to lock the semaphore.

RETURN VALUE

       sem_post() returns 0 on success; on error, the value of the semaphore is left unchanged, -1 is returned, and errno is set to  indicate  the
       error.

ERRORS

       EINVAL sem is not a valid semaphore.

       EOVERFLOW
	      The maximum allowable value for a semaphore would be exceeded.

CONFORMING TO

       POSIX.1-2001.

NOTES

       sem_post() is async-signal-safe: it may be safely called within a signal handler.

EXAMPLE

       See sem_wait(3).

SEE ALSO

       sem_getvalue(3), sem_wait(3), sem_overview(7)

COLOPHON

       This  page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2009-03-30							       SEM_POST(3)