SEM_POST

Section: Linux Programmer's Manual (3)
Updated: 2006-03-25
Index Return to Main Contents
 

NAME

sem_post - unlock a semaphore  

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.
 

CONFORMING TO

POSIX.1-2001.  

NOTES

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

SEE ALSO

sem_getvalue(3), sem_wait(3), sem_overview(7)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO

linux.jgfs.net manual pages