> From windows to/from attu:

 Winscp OR
 Filezilla OR whatever your favorite graphical scp/sftp client 
 Running cygwin use scp or sftp
 (Note to use scp on cygwin you will need to install the openssh package,
 which does not get installed by default:
http://www.question-defense.com/2010/01/07/how-to-install-scp-and-ssh-on-windows-7-using-cygwin)

> From mac to/from attu:

 scp or sftp at terminal

> From Virtual machine to/from attu:

 scp or sftp at terminal OR
 mkdir csehomedir &&
 sshfs username@attu.cs.washington.edu:/homes/iws/username csehomedir/  OR
 view attu directory in file browser - mount attu home dir

> From Virtual machine to local machine (mac or windows):

 drag and drop from the vm to desktop
 You may also be able to copy and paste using right click 
 or control-c, control-v.

> From attu from a URL

 wget - to get a file from a url

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For more info look at the slides linked on the homework page:

http://courses.cs.washington.edu/courses/cse390a/13au/handouts/MovingAndEditingFiles_12sp.pdf