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sync() - Unix, Linux System Call
sync - commit buffer cache to disk
sync() first commits inodes to buffers, and then buffers to disk.
This function is always successful.
SVr4, 4.3BSD, POSIX.1-2001.
According to the standard specification (e.g., POSIX.1-2001),
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
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.