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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.

.inputrc keybinding to wrap current line in inotifytools for instant compile/test-as-you-save-loop
Assuming you've written all of make -j hfst-tokenize && echo doavtter gr?dakursa|./hfst-tokenize --gtd tokeniser-gramcheck-gt-desc.pmhfst and want that to execute every time you :w in vim (or C-xC-s in Emacs), just hit and it'll turn into $ while true; do ( make -j hfst-tokenize && e doavtter gr?dakursa|./hfst-tokenize --gtd tokeniser-gramcheck-gt-desc.pmhfst ); inotifywait -q -e modify -e close_write *; done with the cursor right before the ')'. Hit enter, and it'll run on each save. Requires the package inotify-tools installed.

Ripping VCD in Linux
Ripping VCD in Linux

Notepad in a browser (type this in the URL bar)
It doesn't save your notes, but it's great for jotting something down quickly.

Stop long commands wrapping around and over-writing itself in the Bash shell
add the command either in /etc/profile or ~/.bash_profile so that this is available to your shell.

convert unixtime to human-readable

Use nroff to view the man pages
Using nroff , it is possible to view the otherwise garbled man page with col command.

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

Monitor a file's size
use "watch" instead of while-loops in these simple cases

Double your disk read performance in a single command
(WARN) This will absolutely not work on all systems, unless you're running large, high speed, hardware RAID arrays. For example, systems using Dell PERC 5/i SAS/SATA arrays. If you have a hardware RAID array, try it. It certainly wont hurt. You may be can test the speed disk with some large file in your system, before and after using this: $ time dd if=/tmp/disk.iso of=/dev/null bs=256k To know the value of block device parameter known as readahead. $ blockdev --getra /dev/sdb And set the a value 1024, 2048, 4096, 8192, and maybe 16384... it really depends on the number of hard disks, their speed, your RAID controller, etc. (see sample)


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