sem_post(3)                Library Functions Manual                sem_post(3)

NAME
       sem_post - unlock a semaphore

LIBRARY
       POSIX threads library (libpthread, -lpthread)

SYNOPSIS
       #include <semaphore.h>

       int sem_post(sem_t *sem);

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.

ATTRIBUTES
       For an explanation of the terms used in this section, see
       attributes(7).

       +--------------------------------------------+---------------+---------+
       |Interface                                   | Attribute     | Value   |
       +--------------------------------------------+---------------+---------+
       |sem_post ()                                 | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       POSIX.1-2008.

HISTORY
       POSIX.1-2001.

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

EXAMPLES
       See sem_wait(3) and shm_open(3).

SEE ALSO
       sem_getvalue(3), sem_wait(3), sem_overview(7), signal-safety(7)

Linux man-pages 6.7               2023-10-31                       sem_post(3)