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commandlinefu.com is the place to record those command-line gems that you return to again and again. 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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Fetch all GPG keys that are currently missing in your keyring
For instance, if people have signed your key, this will fetch the signers' keys.

Convert camelCase to underscores (camel_case)
Useful for switching over someone else's coding style who uses camelCase notation to your style using all lowercase with underscores.

Report the established connections for a particular port

diff two unsorted files without creating temporary files
bash/ksh subshell redirection (as file descriptors) used as input to diff

Ping sweep without NMAP
Ping sweep without NMAP

Convert a flv video file to avi using mencoder

One command line web server on port 80 using nc (netcat)
Very simple web server listening on port 80 will serve index.html file or whatever file you like pointing your browser at http://your-IP-address/index.html for example. If your web server is down for maintenance and you'd like to inform your visitors about it, quickly and easily, you just have to put into the index.html file the right HTML code and you are done! Of course you need to be root to run the command using port 80.

Android PNG screenshot
Works with *rooted* Android devices. 400x800 are the screen dimensions of a typical handheld smartphone.

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"

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }


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