two topics Thursday

[der.hans]

moin moin,

Thursday night PLUG has two topics in Big Blue Button. Per usual, we'll
start at 19:00.

Stammtisch is Tuesday at 19:00. We'll be at Boulders on Broadway, but also
have the Big Blue Button room open.

* Topic: Watch Blender Open Movies

Let's fire up the projector and watch a few Blender shorts.

Blender is a Free Software 3D modeller/renderer that is great for making
movies.

They make short movies to highlight features in new releases.

Let's enjoy a few together.

Attendees will get the opportunity to see:

* Spring ( 7:44 )
* Caminandes 1: Llama Drama ( 1:30 )
* Caminandes 2: Gran Dillama ( 2:26 )
* Caminandes 3: Llamigos ( 2:30 )

Supply your own popcorn.

* Topic: Anatomy of the Command Line part 1

Order matters when the shell executes a command, but isn't
strictly left to right. Redirects, functions, sub-shells,
{brace,tilde,parameter,variable,arithmetic} expansion, pipes, globbing,
regular expressions, command substitution and more.  What order does bash
evaluate the different parts of the command line and what effect does that
ordering have on the command? Which portions of the command are evaluated
by the shell and which aren't?

The presentation will use command line examples to illustrate evaluation
order for the various parts of a command.

For example:

grep foo file.txt >file.txt

That command results in file.txt being empty regardless of what the
previous contents were ( provided file permissions allow the user to write
to file.txt ). The reason is that the shell truncates file.txt before even
starting up grep, so grep is actually searching a newly truncated empty
file.

echo -n $( echo foo >>file.txt ) >file.txt

Again there is an empty file at the end even though foo is added to the
file.txt during the command. In this case, the command subtitution and
it's associated output redirection runs and completes before the outer
shell and it's redirection. As a result, file.txt gets a line of input,
then is truncated.

ciao,

der.hans
-- 
#  https://www.SpiralArray.com   https://www.PhxLinux.org
#  "It is a miracle that curiosity survives formal education."
#   -- Albert Einstein