Most powerful examples of Unix commands or scripts every programmer should know

Question

There are many things that all programmers should know, but I am particularly interested in the Unix/Linux commands that we should all know. For accomplishing tasks that we may

Answer 1

I use this so much I am actually ashamed of myself. Remove spaces from all filenames and replace them with an underscore:

[removespaces.sh]

#!/bin/bash
find .  -type f -name "* *" | while read file
do
   mv "$file" "${file// /_}"
done