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.
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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.
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,…):
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Wow, didn't really expect you to read this far down. The latest iteration of the site is in open beta. It's a gentle open beta-- not in prime-time just yet. It's being hosted over at UpGuard (link) and you are more than welcome to give it a shot. Couple things:
If you spend all day editing in vi then switching your fingers to Emacs mode just for the command line can be difficult. Use set -o vi in your bash shell and enjoy the power of a real editor.
Einstein's razor: As simple as possible, but not simpler.
On the destination machine netcat listens on any port (1234 in the example) and sends anything it receives into a file or pipe. On the source machine a separate netcat takes input from a file or pipe and sends it over the network to the listener.
This is great between machines on a LAN where you don't care about authentication, encryption, or compression and I would recommend it for being simpler than anything else in this situation. Over the internet you should use something with better security.
At some point you want to know what packets are flowing on your network. Use tcpdump for this. The man page is obtuse, to say the least, so here are some simple commands to get you started.
-n means show IP numbers and don't try to translate them to names.
-l means write a line as soon as it is ready.
-i eth0 means trace the packets flowing through the first ethernet interface.
src or dst w.x.y.z traces only packets going to or from IP address w.x.y.z.
port 80 traces only packets for HTTP.
proto udp traces only packets for UDP protocol.
Once you are happy with each option combine them with 'and' 'or' 'not' to get the effects you want.
If you are already running screen then you often want to start a command in a fresh window. You use this alias by typing 's whatever' from your command line and 'whatever' starts running in a new window. Good with interactive commands like info, vim, and nethack.
Fool date by setting the timezone out by 24 hours and you get yesterday's date. Try TZ=XYZ-24 to get tomorrow's date. I live in TZ=GMT0BST so you might need to shift the number 24 by the hours in your timezone.
I find this handy for linking all the bin files in a package to /usr/bin or all the man files to /usr/share/man. You can replace * with */* to operate on all the files in subdirectories.