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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" }

Have an ssh session open forever
Open a ssh session opened forever, great on laptops losing Internet connectivity when switching WIFI spots.

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"

Go to directory or creat it and go to
For use in scripts this command is very usefull

Route outbound SMTP connections through a addtional IP address rather than your primary

Use top to monitor only all processes with the same name fragment 'foo'
top accecpts a comma separated list of PIDs.

find and remove old compressed backup files
remove all compressed files in /home/ folder not created in the last 10 days

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"

Concatenate (join) video files
Use mencoder to concatenate (join) multiple video files together.

Delete empty directories
Recursively delete empty directories. Use with care.


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