Due to unforeseen circumstances, we've had a last minute cancellation.
Joe Giron will not be able to make the meeting tomorrow so his
presentation on MassScan will be postponed till next month. Thankfully
Aaron Jones has volunteered to step in in his place so we still have 2
presentations for our meeting on Thursday.
Aaron Jones: CLI way to do things usually done with a GUI
Aaron is a web developer who enjoys using new technologies. He began
using Linux while still a kid and is pro- VIM, GIT, CMUS, and
NEWSBEUTER. His workflow is command line based and he hope's to help
others learn more about computing, linux ,and the tools out there to
make them more productive.
der hans: Anatomy of the Command Line
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.
We go for food/Discussion afterward the meeting to BJs at the nearby mall.
---
The meeting will start at 7pm at The Desert Breeze Substation. People
start arriving as early as 6pm, so if you would like to help setup
and/or chat for a while, arrive a little early.
Desert Breeze Substation
251 North Desert Breeze Blvd
Chandler, AZ 85226
The Desert Breeze Substation is on Chandler Blvd and Desert Breeze Blvd,
which is half way between McClintock and Rural. It is very close
to both the south 202 and 101 freeways. Public transportation is
available into the late hours.
See
http://phxlinux.org/meetings/14-east-valley-meeting.html for a map
and other info.
See you there,
Brian Cluff
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