---
name: "sem"
section: "4"
platform: "linux"
package: "freebsd-manpages"
version: "6.0-5"
release: "Debian 4.0 (Etch)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/sem/4"
---

# sem(4)

POSIX semaphores

## NAME

**sem** – POSIX semaphores

## SYNOPSIS

To link into the kernel:

**options P1003\_1B\_SEMAPHORES**

To load as a kernel loadable module:

```
kldload sem
```

## DESCRIPTION

The **sem** facility provides system calls used by the standard C library (*libc*) to implement POSIX semaphores. It is available both as a kernel option for static inclusion and as a dynamic kernel module.

## SEE ALSO

[sem\_destroy(3)](/sem_destroy/3.md), [sem\_getvalue(3)](/sem_getvalue/3.md), [sem\_init(3)](/sem_init/3.md), [sem\_open(3)](/sem_open/3.md), [sem\_post(3)](/sem_post/3.md), [sem\_wait(3)](/sem_wait/3.md), [config(8)](/config/8.md), [kldload(8)](/kldload/8.md), [kldunload(8)](/kldunload/8.md)

## HISTORY

The **sem** facility appeared as a kernel option in FreeBSD 3.0. The **sem** kernel module appeared in FreeBSD 5.0.