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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" }

Fetch the requested virtual domains and their hits from log file
The command will read the apache log file and fetch the virtual host requested and the number of requests.

Get memory total from /proc/meminfo in Gigs

Find the package that installed a command

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"

Quick key/value display within /proc or /sys
Within /proc and /sys there are a lot of subdirectories, which carry pseudofiles with only one value as content. Instead of cat-ing all single files (which takes quite a time) or do a "cat *" (which makes it hard to find the filename/content relation), just grep recursively for . or use "grep . /blabla/*" (star instead of -r flag). For better readability you might also want to pipe the output to "column -t -s : ".

List all databases in Postgres and their (byte/human) sizes, ordering by byte size descending
Get a listing of all of your databases in Postgres and their sizes, ordering by the largest size first. Requires that you give the -d parameter a valid database name that you can connect to.

Grab IP address on machine with multiple interfaces
Instead of hard-coding in a check to scrape info from ifconfig based on a specific interface, do it in a more portable way. This works really well if you switch between wired, wireless, bluetooth or even VPN connections. You can get your current IP in a script (since it'll be something like tun0 instead of eth0 or wlan1). This uses a well known public ip address 8.8.8.8, but it doesn't actually connect to it, it just shows you the route it would take.

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"

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


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