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.Dd July 2, 2024
.Dt SYNC 2
.Os
.Sh NAME
.Nm sync
.Nd update super block
.Sh SYNOPSIS
.In unistd.h
.Ft void
.Fo sync
.Fa void
.Fc
.Sh DESCRIPTION
The
.Fn sync
function writes all information in memory that should be on disk, including
modified super blocks, modified inodes, and delayed block I/O.
.Pp
Unlike
.Xr fsync 3C ,
which completes the writing before it returns,
.Fn sync
schedules but does not necessarily complete the writing before returning.
To perform a blocking synchronization of a single file system, use the
.Xr syncfs 3C
function.
.Sh USAGE
The
.Fn sync
function should be used by applications that examine a file system, such as
.Xr fsck 8 ,
.Xr df 8 ,
and is mandatory before rebooting.
.Sh INTERFACE STABILITY
.Sy Committed
.Sh SEE ALSO
.Xr fsync 3C ,
.Xr syncfs 3C ,
.Xr attributes 7 ,
.Xr standards 7 ,
.Xr df 8 ,
.Xr fsck 8