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Quick glance at who's been using your system recently
This command takes the output of the 'last' command, removes empty lines, gets just the first field ($USERNAME), sort the $USERNAMES in reverse order and then gives a summary count of unique matches.

list files recursively by size

Safe Delete
remove file that has sensitive info safely. Overwrites it 33 times with zeros

Greets the user appropriately

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" }

Make vim open in tabs by default (save to .profile)
I always add this to my .profile rc so I can do things like: "vim *.c" and the files are opened in tabs.

Matrix Style
I like the fact the Patola's version uses only ones and zeros, but I also like the sparse output of the other versions. This one combines both of those features and eliminates some unnecessary cruft. You can vary the sparseness by changing "$(($RANDOM % 5))" to another number. The number in this term "$(($RANDOM % 4))" controls how frequently the numbers are output bold.

find out which directories in /home have the most files currently open

identify exported sonames in a path
This provides a list of shared object names (sonames) that are exported by a given tree. This is usually useful to make sure that a given required dependency (NEEDED entry) is present in a firmware image tree. The shorter (usable) version for it would be $ scanelf -RBSq -F "+S#f" But I used the verbose parameters in the command above, for explanation.

Sort a one-per-line list of email address, weeding out duplicates


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