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Delete all but the latest 5 files, ignoring directories

convert filenames in current directory to lowercase

extracts 64 bytes of random digits from random lines out of /dev/random sent to stdio
Use this the next time you need to come up with a reasonably random bitstring, like for a WPA/WPA2 PSK or something. Takes a continuous stream of bytes coming from /dev/urandom, runs it through od(1), picking a random field ($0 and $1 excluded) from a random line and then prints it.

Show drive names next to their full serial number (and disk info)
As of this writing, this requires a fairly recent version of util-linux, but is much simpler than the previous alternatives. Basically, lsblk gives a nice, human readable interface to all the blkid stuff. (Of course, I wouldn't recommend this if you're going to be parsing the output.) This command takes all the fun out of the previous nifty pipelines, but I felt I ought to at least mention it as an alternative since it is the most practical.

backup delicious bookmarks
Useful script to backup all your delicious bookmarks. With decilicious shutting down soon , it could be useful

Download all Red Hat Manuals - A better way by user Flatcap
Let's give Flatcap credit for this elegant solution, instead of leaving it hidden as a comment. Tested on RHEL6 and it works. Nice and clean.

Get your outgoing IP address

Calculate pi to an arbitrary number of decimal places
Change the scale to adjust number of decimal places prefix the command with "time" to benchmark the computer (compare how long it takes to calculate 10000 digits of pi on various computers).

Output files without comments or empty lines
Filter comments and empty lines in files. I find this very useful when trying to find what values are actually set in a very long example config file. I often set an alias for it, like : alias nocomment='grep -v "^\($\|#\)"'

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" }


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