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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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Convert all PNG images in directory to JPEG using ImageMagick, and delete the old PNG images.
This should work on any unix platform running bash. Just type the program into cat and give it a ^D when you're done, at which time it will compile, run, and remove the program. Obviously, you can run it without the "rm a.out" if you'd like to keep the binary. If you want to keep the source, well, you might as well just write it in vi or emacs first then.
This uses mpg123 to convert the files to wav before burning, but you can use mplayer or mencoder or ffmpeg or lame with the --decode option, or whatever you like.
remove files with access time older than a given date.
If you want to remove files with a given modification time replace %A@ with %T@. Use %C@ for the modification time.
The time is expressed in epoc but is easy to use any other ordered format.
This command creates and burns a gapless audio CD with 99 tracks. Each track is a 30 second sine wave, the first is 1 Hz, the second 2 Hz, and so on, up to 99 Hz. This is useful for testing audio systems (how low can your bass go?) and for creating the constant vibrations needed to make non-Newtonian fluids (like cornstarch and water) crawl around.
Note, this temporarily creates 500MB of .cdda files in the current directory. If you don't use the "rm" at the end of the command, you can burn more disks using
cdrdao write cdrdao.toc
Prerequisites: a blank CD-R in /dev/cdrw, sox (http://sox.sourceforge.net/), and cdrdao (http://cdrdao.sourceforge.net/). I'm also assuming a recent version of bash for the brace expansion (which just looks nicer than using seq(1), but isn't necessary).
Note the space before the command; that prevents your history eliminating command from being recorded. ' history -c && rm -f ~/.bash_history' Both steps are needed. 'history -c' clears what you see in the history command. 'rm -f ~/.bash_history' deletes the history file in your home directory.
For all of the jpgs in a directory, determine their size and if below a threshold remove them forcefully.
plays with bash arrays. instead of storing the list of files in a temp file, this stores the list in ram, retrieves the last element in the array (the last html file), then removes it.
Converts a .vdi file to a .vmdk file for use in a vmware virtual machine. The benefit: using this method actually works. There are others out there that claim to give you a working .vmdk by simply using the qemu-img command alone. Doing that only results in pain for you because the .vmdk file will be created with no errors, but it won't boot either.
Be advised that these conversions are very disk-intensive by nature; you are probably dealing with disk images several gigabytes in size.
Once finished, the process of using the new .vmdk file is left as an exercise to the reader.
Some malicious program appends a iframe or script tag to you web pages on some server, use this command to clean them in batch.
Check out the usage of 'trap', you may not have seen this one much. This command provides a way to schedule commands at certain times by running them after sleep finishes sleeping. In the example 'sleep 2h' sleeps for 2 hours. What is cool about this command is that it uses the 'trap' builtin bash command to remove the SIGHUP trap that normally exits all processes started by the shell upon logout. The 'trap 1' command then restores the normal SIGHUP behaviour.
It also uses the 'nice -n 19' command which causes the sleep process to be run with minimal CPU.
Further, it runs all the commands within the 2nd parentheses in the background. This is sweet cuz you can fire off as many of these as you want. Very helpful for shell scripts.
Remove your BASH history and then link it to /dev/null
Best way I know to get rid of .bash_history and don't allow bash to save the current one on exit
Edit: added ~/ before .bash_history, just in case... ;)
this string of commands will release your dhcp address, change your mac address, generate a new random hostname and then get a new dhcp lease.
USAGE: gate listening_port host port
Creates listening socket and connects to remote device at host:port. It uses pipes for connection between two sockets. Traffic which goes through pipes is wrote to stdout. I use it for debug network scripts.
Remove everything in current directory except files starting with "ca".
This helped me find a botnet that had made into my system. Of course, this is not a foolproof or guarantied way to find all of them or even most of them. But it helped me find it.