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Run a command for a given time
or "Execute a command with a timeout" Run a command in background, sleep 10 seconds, kill it. $! is the process id of the most recently executed background command. You can test it with: find /& sleep10; kill $!

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"

copy ACL of one file to another using getfacl and setfacl

display typedefs, structs, unions and functions provided by a header file
will display typedefs, structs, unions and functions declared in 'stdio.h'(checkout _IO_FILE structure). It will be helpful if we want to know what a particular header file will offer to us. Command 'cpp' is GNU's C Preprocessor.

Download all data from Google Ngram Viewer
To learn more about Google Ngram Viewer: http://ngrams.googlelabs.com/info

Produce a pseudo random password with given length in base 64
Of course you will have to install Digest::SHA and perl before this will work :) Maximum length is 43 for SHA256. If you need more, use SHA512 or the hexadecimal form: sha256_hex()

Get a shell with a not available account

Watch Star Wars via telnet
Use Ctrl-] to stop it.

Port Knocking!
Knock on ports to open a port to a service (ssh for example) and knock again to close the port. You have to install knockd. See example config file below. [options] logfile = /var/log/knockd.log [openSSH] sequence = 3000,4000,5000 seq_timeout = 5 command = /sbin/iptables -A INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT tcpflags = syn [closeSSH] sequence = 5000,4000,3000 seq_timeout = 5 command = /sbin/iptables -D INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT tcpflags = syn

Show numerical values for each of the 256 colors in bash
Same as http://www.commandlinefu.com/commands/view/5876, but for bash. This will show a numerical value for each of the 256 colors in bash. Everything in the command is a bash builtin, so it should run on any platform where bash is installed. Prints one color per line. If someone is interested in formatting the output, paste the alternative.


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