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Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.
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What do you do when nmap is not available and you want to see the hosts responding to an icmp echo request ? This one-liner will print all hosts responding with their ipv4 address.
Waiting for your server to finish rebooting? Issue the command above and you will hear a beep when it comes online. The -i 60 flag tells ping to wait for 60 seconds between ping, putting less strain on your system. Vary it to your need. The -a flag tells ping to include an audible bell in the output when a package is received (that is, when your server comes online).
On Linux and Mac systems (I have not tested with other Unix systems), the ping command will keep on pinging until the user interrupts it with Ctrl+C. On Windows system, ping will execute for a number of times then quit. The -c flag on Linux and Mac will make this happen
this is very useful when there is a different network host to determine which are turned on or not
Ping machine once, waiting 1 second for response until failing. Upon fail, ssh globally, otherwise ssh locally.
The tee (as in "T" junction) command is very useful for redirecting output to two places.