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Simple multi-user encrypted chat server for 5 users
Client ~$ ncat --ssl localhost 9876 Change localhost to the correct ip address.

Delete all non-printing characters from a file
tr has some predefined sets of characters that are more convenient to use than characters codes

Rsync a directory excluding pesky .svn dirs

revert a file with svn

Empty a file
The downside of output redirection is that you need permissions. So something like $ > file won't play nicely w/ sudo. You'd need to do something like $ bash -c '> file' instead, you could go w/ $ sudo truncate -s0 file

Hardlink all identical files in the current directory (regain some disk space)
Meaning of switches (see man page too): v verbose p ignore mode (permissions) o ignore owner, group t ignore time of modification Disadvantage: If you modify any linked file, this will propagate to all other files which occupy the same space.

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

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" }

Change user, assume environment, stay in current dir
I've used this a number of times troubleshooting user permissions. Instead of just 'su - user' you can throw another hyphen and stay in the original directory.

Show biggest files/directories, biggest first with 'k,m,g' eyecandy
I use this on debian testing, works like the other sorted du variants, but i like small numbers and suffixes :)


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