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List the size (in human readable form) of all sub folders from the current location
Tested on MacOS and GNU/Linux. It works in dirs containing files starting with '-'. It runs 'du' only once. It sorts according to size. It treats 1K=1000 (and not 1024)

Compute the average number of KB per file for each dir
Shorter version using --tag

Adding Prefix to File name

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" }

Display information sent by browser
Have netcat listen on port 8000, point browser to http://localhost:8000/ and you see the information sent. netcat terminates as soon as your browser disconnects. I tested this command on my Fedora box but linuxrawkstar pointed out that he needs to use $ nc -l -p 8000 instead. This depends on the netcat version you use. The additional '-p' is required by GNU netcat that for example is used by Debian but not by the OpenBSD netcat port used by my Fedora system.

Finding all files on local file system with SUID and SGID set

Leap year calculation

Get last sleep time on a Mac
Similarly for last wake time: $ sysctl -a | grep waketime

Getting ESP and EIP addresses from running processes
'ps' let you specify the format that you want to see on the output.

tee to a file descriptor
the tee command does fine with file names, but not so much with file descriptors, such as &2 (stderr). This uses process redirection to tee to the specified descriptor. In the sample output, it's being used to tee to stderr, which is connected with the terminal, and to wc -l, which is also outputting to the terminal. The result is the output of bash --version followed by the linecount


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