commandlinefu.com is the place to record those command-line gems that you return to again and again.
Delete that bloated snippets file you've been using and share your personal repository with the world. 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.
If you have a new feature suggestion or find a bug, please get in touch via http://commandlinefu.uservoice.com/
You can sign-in using OpenID credentials, or register a traditional username and password.
First-time OpenID users will be automatically assigned a username which can be changed after signing in.
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.
Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):
Subscribe to the feed for:
Alternative to the ping check if your firewall blocks ping. Uses curl to get the landing page silently, or fail with an error code. You can probably do this with wget as well.
Joker wants an email if the Brand X server is down. Set a cron job for every 5 mins with this line and he gets an email when/if a ping takes longer than 3 seconds.
After this, just type:
You need to install "beep" before this would make the beep sound.
Save it in your .profile if you want to use it later
WARNING: this command won't exit until it is successful. You won't be able to CONTROL+C out of it.
If you need to ssh into a computer on the local network but you're unsure of the ip to use, then ping them and see if you get a response. If you do, print out the address you got it from. Adjust the range to suit your network.
In the vein of "can you do it better", here is my take on using "ping" to emulate sleep in a DOS/BAT script. If one can use ping at all then the multicast address will be valid but will not respond. By doing only one ping (-n 1) and setting a timeout in milliseconds (-w 10000) you have a fairly accurate timer. This example gives about a 10 second sleep.
Ping sweep without NMAP
When run on a mac, this command will bring up a dialog box in the Terminal when server HOSTNAME first responds to a ping.
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.