Manpage of SEM_POST

SEM_POST

Section: Linux Programmer's Manual (3)
Updated: 2015-03-02
Index
 

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 errnois set to indicate the error.  

ERRORS

EINVAL
semis 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).
InterfaceAttributeValue
sem_post() Thread safetyMT-Safe
 

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)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
NOTES
EXAMPLE
SEE ALSO

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