Create a test user in PostgreSQL Updated 2025-07-16
In order to create a test user with password instead of peer authentication, let's create test user:
createuser -P user0
createdb user0
-P makes it prompt for the users password.
Alternatively, to create the password non-interactively stackoverflow.com/questions/42419559/postgres-createuser-with-password-from-terminal:
psql -c "create role NewRole with login password 'secret'"
Can't find a way using the createuser helper.
We can then login with that password with:
psql -U user0 -h localhost
which asks for the password we've just set, because the -h option turns off peer authentication, and turns off password authentication.
The password can be given non-interactively as shown at stackoverflow.com/questions/6405127/how-do-i-specify-a-password-to-psql-non-interactively with the PGPASSWORD environment variable:
PGPASSWORD=a psql -U user0 -h localhost
Now let's create a test database which user0 can access with an existing superuser account:
createdb user0db0
psql -c 'GRANT ALL PRIVILEGES ON DATABASE user0db0 TO user0'
We can check this permission with:
psql -c '\l'
which now contains:
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 user0db0  | ciro     | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 | =Tc/ciro             +
           |          |          |             |             | ciro=CTc/ciro        +
           |          |          |             |             | user0=CTc/ciro
The permission letters are explained at:
user0 can now do the usual table operations on that table:
PGPASSWORD=a psql -U user0 -h localhost user0db0 -c 'CREATE TABLE table0 (int0 INT, char0 CHAR(16));'
PGPASSWORD=a psql -U user0 -h localhost user0db0 -c "INSERT INTO table0 (int0, char0) VALUES (2, 'two'), (3, 'three'), (5, 'five'), (7, 'seven');"
PGPASSWORD=a psql -U user0 -h localhost user0db0 -c 'SELECT * FROM table0;'
Crown group Updated 2025-07-16
Kind of the opposite of a basal group.
Crucifixion Updated 2025-07-16
Crying Updated 2025-07-16
Cryogenic electron microscopy Updated 2025-07-16
This technique has managed to determine protein 3D structures for proteins that people were not able to crystallize for X-ray crystallography.
It is said however that cryoEM is even fiddlier than X-ray crystallography, so it is mostly attempted if crystallization attempts fail.
By looking at Figure 1. "A cryoEM image", you can easily understand the basics of cryoEM.
We just put a gazillion copies of our molecule of interest in a solution, and then image all of them in the frozen water.
Each one of them appears in the image in a random rotated view, so given enough of those point of view images, we can deduce the entire 3D structure of the molecule.
Ciro Santilli once watched a talk by Richard Henderson about cryoEM circa 2020, where he mentioned that he witnessed some students in the 1980's going to Germany, and coming into contact with early cryoEM. And when they came back, they just told their principal investigator: "I'm going to drop my PhD theme and focus exclusively on cryoEM". That's how hot the cryo thing was! So cool.
Figure 1. . Source. This is the type of image that you get out of a raw CryoEM experiment.
Video 1.
The structure of our cells by Matteo Allegretti
. Source. The start is useless. But the end at this timestamp shows an interesting technique where they actually cut up cells in fine slices and image them, that's cool.
Cryptosystem Updated 2025-07-16
Csound FLOSS manual Updated 2025-07-16
Includes introduction to the basic sound synthesis and their implementation in Csound.
Examples run on browser via Emscripten and just worked on Ubuntu 20.04!
Examples can also be downloaded all at once from: www.csound-tutorial.net/floss_manual/ Shame not in Git as standalone files.
CSS flex Updated 2025-07-16
  • css/flex.html: illustrates basic flex usage, including:
  • flex-grow: if there's space left, this determines how much extra space will be given to each.
  • flex-basis: the size the items want to be. But if there isnt' enough space, this can be cut up.
    Note that the minimal space required by children of the flex children cannot be necessarily cut up, and might lead things to overflow out of the container.
  • flex-shrink: if there's space missing, this determines how much extra space will be removed from each flex-basis
Other examples include:
That example calculates and displays the final widths via JavaScript, making it easier to understand the calculations being done.
csvtools Updated 2025-07-16
A fast version of a somewhat subset of csvkit, written in C.
Build failed with undefined reference to pcre_config on Ubuntu 23.04: github.com/DavyLandman/csvtools/issues/18
Unfortunately it is lacking some basic options, like optional header + selecting column by index on csvgrep (though csvcut has it). The project seems kind of dead.
Also unclear if it allows to filter + print only selected columns.
CUDA Updated 2025-07-16
Cuju Updated 2025-07-16
Lit. "to kick (leather) ball".
Figures notbaly in Water Margin, where it is played by Gao Qiu. The novel also suggests that it was considered a lesser art, e.g. as opposed to the scholarly four arts and the "proper" martial arts.
Video 1.
Ancient Chinese Football Freestylers by Tifo Football (2021)
Source. Mentions that it was popular in the Ming dynasty, but then, if you will, the ball fell off a bit.
Video 2.
Bernardo cuju challenge by Manchester City (2019)
Source.

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