Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

sem_post(3) [linux man page]

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 3.27 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)

Check Out this Related Man Page

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 -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 3.44 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 2012-05-13 SEM_POST(3)
Man Page

4 More Discussions You Might Find Interesting

1. Programming

Example for use of kernel semaphore

Hi friends I'm doing a project and in that I need to use kernel semaphore but I'm not very clear about how to use it. I've used system V semaphore. What I find difficult to understand is that in system V semaphore, a semaphore set is registered to the system (the semid returned from semget call... (3 Replies)
Discussion started by: Rakesh Ranjan
3 Replies

2. UNIX for Advanced & Expert Users

synchronize processes

hi. i am writing a c program under bash shell. i would like to use semaphore functions like sem_wait(), sem_post() and i included <semaphore.h> and it compailes fine but when i try to run it gives me an error "undefined reference to sem_wait() , sem_post() , sem_init()" what have i missed... (2 Replies)
Discussion started by: emil2006
2 Replies

3. UNIX for Dummies Questions & Answers

Explain the need for a semaphore in Linux kernel.

Explain the need for a semaphore in Linux kernel. (0 Replies)
Discussion started by: anupa
0 Replies

4. HP-UX

avoid semphore lock

we developed a set of system V semphore interface for our application, in general, all of them work normal, seldom cause the deadlock. Here are some important sem_wait and sem_post interface, pls point some suggestion to fixed the deadlock problem: int sem_wait_V(int id, struct sembuf *sem_pv)... (1 Reply)
Discussion started by: Frank2004
1 Replies