SYNC(2) System Calls Manual SYNC(2) 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 in- formation in the cache is lost after a system crash, a sync() system call is issued frequently by the kernel process syncer(4) (about every 30 sec- onds). The fsync(2) system call may be used to synchronize individual file de- scriptor attributes. SEE ALSO fsync(2), syncer(4), sync(8) HISTORY The sync() function appeared in Version 3 AT&T UNIX. BUGS The sync() system call may return before the buffers are completely flushed. FreeBSD 15.1 STABLE December 1, 2017 SYNC(2)
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