sem_post(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | EXAMPLES | SEE ALSO | COLOPHON

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

NAME         top

       sem_post - unlock a semaphore

SYNOPSIS         top

       #include <semaphore.h>

       int sem_post(sem_t *sem);

       Link with -pthread.

DESCRIPTION         top

       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         top

       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         top

       EINVAL sem is not a valid semaphore.

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

ATTRIBUTES         top

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

       ┌───────────┬───────────────┬─────────┐
       │Interface  Attribute     Value   │
       ├───────────┼───────────────┼─────────┤
       │sem_post() │ Thread safety │ MT-Safe │
       └───────────┴───────────────┴─────────┘

CONFORMING TO         top

       POSIX.1-2001.

NOTES         top

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

EXAMPLES         top

       See sem_wait(3) and shm_open(3).

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.10 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                          2020-08-13                    SEM_POST(3)

Pages that refer to this page: sem_close(3)sem_destroy(3)sem_getvalue(3)sem_init(3)sem_open(3)sem_timedwait(3p)sem_unlink(3)sem_wait(3)sem_overview(7)signal-safety(7)