sync - Flush file system metadata and data from memory buffers to disk.
The sync utility runs the sync function, which flushes (writes) system
metadata and data from all unwritten memory buffers to disk. For example,
the data flushed includes, for UFS, modified inodes and delayed block I/O.
Other commands that bring the system down, such as the shutdown command,
issue their own sync functions.
Use this sync utility to ensure file system integrity should you need to
stop the system under unusual circumstances.
Note that the writing of buffers to disk, although scheduled, may not be
complete when the utility exits.
Specifies the command path