fsync - synchronize a file's complete in-core state with that on disk #include <unistd.h> int fsync(int fd); DESCRIPTION fsync copies all in-core parts of a file to disk, and waits until the device reports that all parts are on stable storage. It also updates metadata stat information. It does not necessarily ensure that the entry in the directory containing the file has also reached disk. For that an explicit fsync on the file descriptor of the directory is also needed.