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Rename files in batch

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" }

list block devices
Shows all block devices in a tree with descruptions of what they are.

Instead of writing a multiline if/then/else/fi construct you can do that by one line
instead of writing: if [[ "$1" == "$2" ]]; then echo "$1 is equal $2" else echo "$1 differs from $2" fi do write: [[ "$1" == "$2" ]] && echo "$1 is equal $2" || echo "$1 differs from $2"

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 CSV to JSON
Replace 'csv_file.csv' with your filename.

list block devices
Shows all block devices in a tree with descruptions of what they are.

Show some trivia related to the current date
Contrary to logic, typing calendar won't show a calendar, that's the job of cal. Typing calendar will show some trivia related to the current date. Tested against many Linux distros and FreeBSD.

Two command output
Summarize established connections after netstat output. Using tee and /dev/stderr you can send one command output to terminal before executing wc so you can summarize at the bottom of the output.

Emulating netcat -e (netcat-traditional or netcat-openbsd) with the gnu-netcat
Then just nc servername 2600 and ./script.sh kill the client with ctrl+c. You can reconnect several times. kill the server with exit


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