====== rsync ======
''rsync'' is a powerful tool for syncing files, either locally on the same machine or remotely between different machines. Use ''man rsync'' to read the manual pages to learn more.

===== Examples =====
If I want to sync (i.e., update all files that have been newly created or modified and remove all files that have been deleted) the ''~/active_project'' directory on my local workstation up to the server (oak.local in this example), the process can be completed in one command:
<code bash>
rsync -av --delete ~/active_project oak.local:~
</code>

Alternatively, if I want to copy only the files that have been changed in ''/scratch/chkuo/spiro1.02'' directory on the server (oak.local again) back to my local workstation, I can use:
<code bash>
rsync -av --delete oak.local:/scratch/chkuo/spiro1.02 /scratch/chkuo
</code>

This is better than using ''scp'' because ''rsync'' can skip files that already exist in the destination and have not been updated in the source.

It is **important** to note that the absence or presence of the trailing slash at the end of the source directory (i.e., ''~/active_project'' versus ''~/active_project/'') have different effects, so be careful.

===== Advanced uses =====
If we need to sync some directories quite often (like the ''~/active_project'' example above), it is easier to save the command in a schell script and place the script somewhere in the search path (''~/bin'' or ''~/script'' for example, see [[tutorials:bash|.bashrc]] for more info).