sys.subproj/sem_post.2

   1 .\"     $Darwin$
   2 .\"
   3 .\" Wilfredo Sanchez, wsanchez@apple.com
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  24 .Dd June 8, 2000
  25 .Dt SEM_POST 2
  26 .Os Darwin
  27 .Sh NAME
  28 .Nm sem_post
  29 .Nd unlock a semaphore
  30 .Sh SYNOPSIS
  31 .Fd #include <semaphore.h>
  32 .Ft int
  33 .Fn sem_post "sem_t *sem"
  34 .Sh DESCRIPTION
  35 The the semaphore referenced by
  36 .Fa sem
  37 is unlocked, the value of the semaphore is incremented, and all
  38 threads which are waiting on the semaphore are awakened.
  39 .Pp
  40 .Fn sem_post
  41 is reentrant with respect to signals and may be called from within a
  42 signal hanlder.
  43 .Pp
  44 If successful,
  45 .Fn sem_post
  46 will return 0.  Otherwise, -1 is returned and
  47 .Va errno
  48 is set.
  49 .Sh ERRORS
  50 .Fn sem_post
  51 succeeds unless:
  52 .Bl -tag -width Er
  53 .It Bq Er EINVAL
  54 .Fa sem
  55 is not a valid semaphore descriptor.
  56 .El
  57 .Sh SEE ALSO
  58 .Xr semctl 2 ,
  59 .Xr semget 2 ,
  60 .Xr semop 2 ,
  61 .Xr sem_open 2 ,
  62 .Xr sem_trywait 2 ,
  63 .Xr sem_wait 2
  64 .Sh HISTORY
  65 .Fn sem_post
  66 is specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995).