Commands by jtopian (1)

What's this? is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

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Replace *** with the appropiate values

Calculating series with awk: add numbers from 1 to 100
"seq 100" outputs 1,2,..,100, separated by newlines. awk adds them up and displays the sum. "seq 1 2 11" outputs 1,3,..,11. Variations: 1+3+...+(2n-1) = n^2 $ seq 1 2 19 | awk '{sum+=$1} END {print sum}' # displays 100 1/2 + 1/4 + ... = 1 $ seq 10 | awk '{sum+=1/(2**$1)} END {print sum}' # displays 0.999023

List open TCP/UDP ports

Get list of servers with a specific port open
Change the -p argument for the port number. See "man nmap" for different ways to specify address ranges.

Find the package that installed a command

Optimal way of deleting huge numbers of files

Limit bandwidth usage by apt-get
Limits the usage of bandwidth by apt-get, in the example the command will use 30Kb/s ;) It should work for most apt-get actions (install, update, upgrade, dist-upgrade, etc.)

Dump android contacts, sms
Crude, but works. Note for security, /data/ will be inaccessible unless your device has been *rooted*. On the other hand, if a device has been rooted, its data is now wide open to anyone with a USB cable and the above "one-liner". `adb` is one of the platform tools in the android SDK. To get SMS messages: $ adb pull /data/data/ ; sqlite3 -batch

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Find out how old a web page is
I is for headers only s is for silence curl -Is outputs ONLY headers the pipe and grep is to filter them to Modified only..

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