VI:
In vi, to copy the whole line and have it repeated (I use when doing mass mv or cp commands)
:%s/.*/& &/
REDIRECTION:
Dump to a file:
ls -1a > output.txt
Append to a file:
ls -1a >> output.txt
Redirect standard error:
ls -1a 2> error.txt
Run a script to redirect to a file AND show on the screen:
ls -1a | tee -a output.txt
