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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"

split a multi-page PDF into separate files
Simple alternative to the previous submitted one

memory usage

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

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 host name
With sed you can replace strings on the fly.

seq can produce the same thing as Perl's ... operator.
Optionally, one can use {1..50} instead of seq. E.g. for i in {1..50} ; do echo Iteration $i ; done

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

Get your outgoing IP address
should be very consistent cause it's google :-)

get function's source
no need to reinvent the wheel. Thanks to the OP for the "obsolete" hint. 'declare' may come in pretty handy on systems paranoid about "up-to-dateness"


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