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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" }

unbuffered tcpdump
Sometimes the question comes up: How to get unbuffered tcpdump output into the next program in the pipe? i.e. if your OS forces you to wait for the buffer to fill before the next program sees any of the output If you use -Uw- then you can't use -A (or -X or -XX) at the same time. When the question comes up, I've never seen anyone suggest this simple solution: chaining 2 tcpdump instances.

send file to remote machine and unzip using ssh
This version transfers gzipped data which is unzipped as it arrives at the remote host.

How to run a command on a list of remote servers read from a file
dsh - Distributed shell, or dancer?s shell ;-) you can put your servers into /etc/dsh/machines.list than you don't have to serperate them by commata or group them in different files and only run commands for this groups dsh -M -c -a -- "apt-get update"

Detect encoding of a text file
This command gives you the charset of a text file, which would be handy if you have no idea of the encoding.

bash pause command
Waiting for a key stroke. You can use this with a ";" behind to build a command chain.

Erase a word
hit BACKSPACE more than once to delete more words

Get the current gold price
Returns the current price of a troy ounce of gold, in USD. Requires the "jq" JSON parser.

find out how many days since given date
You can also do this for seconds, minutes, hours, etc... Can't use dates before the epoch, though.

Backup all MySQL Databases to individual files


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