V3/usr/man/man2/sync.2

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NAME		sync -- update super-block
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SYNOPSIS	sys sync  / sync = 36.; not in assembler
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DESCRIPTION	sync____
causes the super block for all file systems to be written out.
It is only necessary on systems in which
this writing may be delayed
for a long time, i.e., those which
incorporate hardware protection facilities.

It should be used by programs which examine a file system,
for example check, df, tm, etc.
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SEE ALSO	--
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DIAGNOSTICS	--
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BUGS		--