Some useful commands

1, Multiple Files Search and Replace:
perl -pi -w -e 's/search/replace/g;' *.txt

2, unzip and tar:
gunzip -c foo.tar.gz | tar xopf -
or,
tar xzvf foo.tar.gz

3, disk usage
du -sh "/vws/rqj/*"
df -h

4, show difference between versions in Clearcase.
vt ct diff filename@@/main/1 filename@@/main/2

5, Enable copy&paste for VNC
vncconfig -nowin &