Shell stuff

A couple of shell related things I gathered:

• Cool guide
• Bash's `:' forces to return 1. For example, use it as in ` || :'
• trap ' DEBUG|EXIT' (EXIT overrides all installed signal handlers!)
• ${X:} stuff. All string operations are interesting but hard to remember
  
• s/\(\)/\1/
• set - Very handy -- look at -x/-u/-n for instance
• Awk Kownledge Base.