SYNC(2) | System Calls Manual | SYNC(2)

# NAME

`sync` — synchronize disk block in-core status with that on disk

# SYNOPSIS

`#include <unistd.h>`

void
`sync`(void);

# DESCRIPTION

The `sync`() function 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`() call is issued frequently by the in-kernel process update (about every 30 seconds).

The function fsync(2) may be used to synchronize individual file descriptor attributes.

# SEE ALSO

fsync(2), sync(8)

# STANDARDS

The `sync`() function conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

# HISTORY

A `sync`() function appeared in Version 2 AT&T UNIX.

# BUGS

`sync`() may return before the buffers are completely flushed.

March 31, 2022 | Debian