---
name: "sync"
section: "2freebsd"
platform: "linux"
package: "freebsd-manpages"
version: "12.2-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/sync/2freebsd"
---

# sync(2freebsd)

schedule file system updates

## NAME

**sync** – schedule file system updates

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<unistd.h\>**

*void*\

**sync**(*void*);

## DESCRIPTION

The **sync**() system call forces a write of dirty (modified) buffers in the block buffer cache out to disk. The kernel keeps this information in core to reduce the number of disk I/O transfers required by the system. As information in the cache is lost after a system crash, a **sync**() system call is issued frequently by the kernel process [syncer(4)](/syncer/4.md) (about every 30 seconds).

The [fsync(2)](/fsync/2.md) system call may be used to synchronize individual file descriptor attributes.

## SEE ALSO

[fsync(2)](/fsync/2.md), [syncer(4)](/syncer/4.md), [sync(8)](/sync/8.md)

## HISTORY

The **sync**() function appeared in Version 3 AT&T UNIX.

## BUGS

The **sync**() system call may return before the buffers are completely flushed.