sys/sem_post.2

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