Spacerats little techwiki

• Remove offending key from known_hosts file with one command

$ sed -i 18d .ssh/known_hosts

• Whats my WAN IP?

$ dig +short myip.opendns.com @resolver1.opendns.com

• Math on the cli

Basic operations

$ echo $((1+1))
2
$ echo $((3-1))
2
$ echo $((4/2))
2
$ echo $((1*2))
2

Basic ops using expr

$ expr 60 / 5
12

Floating point calculations

$ echo "2*2.2/2.2" | bc
2

$ echo "4.4+7/8-(4.74*3.14)" | bc
-10.48

using here-doc

$ bc <<< "4.4+7/8-(4.74*3.14)"
-10.48

a bash funtion, for your .bashrc

calc () {
    bc -l <<< "$@"
}

usage:

$ calc 65320*670
43764400