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Linux man pages : sync (2)
SYNC(2)			   Linux Programmer's Manual		       SYNC(2)

NAME

sync - commit buffer cache to disk.

SYNOPSIS

#include <unistd.h> void sync(void);

DESCRIPTION

sync first commits inodes to buffers, and then buffers to disk.

CONFORMING TO

SVr4, SVID, X/OPEN, BSD 4.3

BUGS

According to the standard specification (e.g., SVID), sync() schedules the writes, but may return before the actual writing is done. However, since version 1.3.20 Linux does actually wait. (This still does not guarantee data integrity: modern disks have large caches.)

NOTES

Since glibc 2.2.2 the Linux prototype is as listed above, following the various standards. In libc4, libc5, and glibc up to 2.2.1 it was "int sync(void)", and sync always returned 0.

SEE ALSO

bdflush(2), fsync(2), fdatasync(2), update(8), sync(8) Linux 2.4 2001-10-10 SYNC(2)