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FSYNC(2) System Calls Manual FSYNC(2)

fsyncsynchronize a file's in-core state with that on disk

#include <unistd.h>

int
fsync(int fd);

() causes all modified data and attributes of fd to be moved to a permanent storage device. This normally results in all in-core modified copies of buffers for the associated file to be written to a disk.

() should be used by programs that require a file to be in a known state, for example, in building a simple transaction facility.

A 0 value is returned on success. A -1 value indicates an error.

The fsync() fails if:

[]
fd is not a valid descriptor.
[]
fd refers to a socket, not to a file.
[]
An I/O error occurred while reading from or writing to the file system.

sync(2), sync(8)

The fsync() function call appeared in 4.2BSD.

April 29, 2011 OpenBSD-5.1