MacFUSE
MacFUSE is a software that allows you to write arbitrary file systems as user-space programs. MacFUSE can be downloaded from here
For me, the immediate use of MacFUSE is to mount a remote filesystem (like my webserver) as a local directory. Eg:
$ sshfs pradeep@pradeepgowda.com:/home/pradeep /Users/pradeep/pgowda -ocache=no -onolocalcaches -ovolname=ssh
The above command mounts the home directory of my account on the remote server (pradeepgowda.com) locally on /Users/pradeep/pgowda.
To edit a file on my remote machine, I just have to cd to ~/pgowda.
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