Interactive simulations <http://phet.colorado.edu/> 
http://www.regentsprep.org/Regents/phys ... icCode=03b

Faraday's Law


Ohm's Law


Battery-Resistor Circuit


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Check postfix logs for email delivery  

#!/bin/bash

# program: postfix log checker
# version: 1.2
# purpose: to check logs for mail transport
# usage: $0 from email@domain
# $0 to email@domain

argc=$# # argument count
argv[0]=$0 # argv[0] is a prog name

TEMP1=/tmp/$$.temp1
TEMP2=/tmp/$$.temp2
TEMP3=/tmp/$$.temp3

> $TEMP1
> $TEMP2
> $TEMP3

trap "rm -f $TEMP1 $TEMP2 $TEMP3; echo; echo 'program stopped by user'; exit" INT TERM

[ ! $1 ] && echo "please specify from or to, ie: from tomas" && exit
[ ! $2 ] && echo "please specify recipient email address, or a part of address" && exit

for foo in $( seq $argc )
do
eval "argv[${foo}]=\$${foo}"
done

[ $1 == "from" ] && SEARCH=" from="
[ $1 == "to" ] && SEARCH=" to="

email=${argv[2]}

echo "------------------------------------------------"
echo "search: ($SEARCH)*${email}*"
echo "------------------------------------------------"

for logfile in $( ls -1 /var/log/maillog* )
do
echo "parsing logfile ... $logfile"
if [ $( echo $logfile | grep -i "*gz$" ) ]; then
zcat $logfile | grep -i -E "${SEARCH}.${email}|${SEARCH}${email}" >> $TEMP1
else
cat $logfile | grep -i -E "${SEARCH}.${email}|${SEARCH}${email}" >> $TEMP1
fi
done

cat $TEMP1 | sed -e "s/ / /g" | cut -d" " -f 6 | sed -e "s/://g" | sort | uniq \
>> $TEMP2

EVENTS=$( cat $TEMP2 | wc -l )

echo "we have found $EVENTS records in our logs"
echo "compacting results"
echo "------------------------------------------------"

> $TEMP3
for event in $( cat $TEMP2 )
do
> $TEMP1
echo -n " $event"
for logfile in $( ls -1 /var/log/maillog* )
do
if [ $( echo $logfile | grep -i "*gz$" ) ]; then
zcat $logfile | grep -i $event | tr '\n' ' ' >> $TEMP1
else
cat $logfile | grep -i $event | tr '\n' ' ' >> $TEMP1
fi
echo -n "."
done

# here we have in $TEMP1 all the log events related to mail message"
# we have it as a single long line
# first, check for sender and recipient
sender=""; orig_recipient=""; recipient=""; status=""; datetime=""; timestamp=""

#cat $TEMP1

datetime=$( cat $TEMP1 | sed -e "s/ / /g" | cut -d" " -f1,2,3 ) > /dev/null
timestamp=$( date -d "$datetime" "+%s" )

REGULAR="s/.* \(from=[^ ,]*\).*/\1/p"
sender=$( cat $TEMP1 | sed -n "$REGULAR" ) > /dev/null

REGULAR="s/.* \(to=[^ ,]*\).*/\1/p"
recipient=$( cat $TEMP1 | sed -n "$REGULAR" ) > /dev/null

REGULAR="s/.* \(orig_to=[^ ,]*\).*/\1/p"
orig_recipient=$( cat $TEMP1 | sed -n "$REGULAR" ) > /dev/null

REGULAR="s/.* \(status=[^ ]*\).*/\1/p"
status=$( cat $TEMP1 | sed -n "$REGULAR" ) > /dev/null

if [ $orig_recipient ]; then
echo "$timestamp, $event, $datetime, $sender, $orig_recipient (yet forwarded!), $status" >> $TEMP3
else
echo "$timestamp, $event, $datetime, $sender, $recipient, $status" >> $TEMP3
fi
done

echo
echo "------------------------------------------------"
echo "generating list, please press space to continue"
echo "running more "
echo "q to quit "
echo "------------------------------------------------"
echo
sleep 3

sort -n --key=1,9 $TEMP3 | more

rm $TEMP1
rm $TEMP2
rm $TEMP3



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Lessons In Electric Circuits 
A free series of textbooks on the subjects of electricity and electronics
Copyright (C) 2000-2012, Tony R. Kuphaldt
http://openbookproject.net/electricCircuits/

Units
http://www.knowledgedoor.com/2/units_an ... fixes.html

Circuit Simulation DC only, Java
http://phet.colorado.edu/en/simulation/ ... ion-kit-dc

Calculating an resistor value
http://www.kpsec.freeuk.com/components/led.htm

Kirhoff's Law explained
http://electron9.phys.utk.edu/phys136d/ ... chhoff.htm
http://www.regentsprep.org/Regents/phys ... efault.htm
http://www.physics.uoguelph.ca/applets/ ... index.html


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UNIX signals 
signály jsou softwarová přerušení běhu procesu a slouží ke komunikaci mezi procesy nebo v rámci procesu.

přehled signálů, jak je popisuje standard POSIX.1-1990
------------------------------------------------------
Signal Value Action Comment
------------------------------------------------------
HUP 1 Term Hangup detected on controlling terminal
or death of controlling process
INT 2 Term Interrupt from keyboard
QUIT 3 Core Quit from keyboard
KILL 4 Core Illegal Instruction
ABRT 6 Core Abort signal from abort(3)
FPE 8 Core Floating point exception
KILL 9 Term Kill signal
SEGV 11 Core Invalid memory reference
PIPE 13 Term Broken pipe: write to pipe with no readers
ALRM 14 Term Timer signal from alarm(2)
TERM 15 Term Termination signal
TERM is a default signal sent by kill(1) command
------------------------------------------------------
Signal Value Action Comment
------------------------------------------------------
USR1 30,10,16 Term User-defined signal 1
USR2 31,12,17 Term User-defined signal 2
CHLD 20,17,18 Ign Child stopped or terminated
CONT 19,18,25 Cont Continue if stopped
STOP 17,19,23 Stop Stop process
TSTP 18,20,24 Stop Stop typed at tty
TTIN 21,21,26 Stop tty input for background process
TTOU 22,22,27 Stop tty output for background process

handler zajišťuje mapování signálu na obslužný kód. obsluhu signálů KILL a STOP přebírá vždy operační systém. v jiných případech je možno určit, zda signál je ignorován (SIG_IGN), zpracován v operačním systému definovaným obslužným programovým kódem - default (SIG_DFL), nebo obsloužen pro proces specifickým programovým kódem.

http://www.enderunix.org/docs/signals.pdf


Catching signal in BASH, example 1

#!/bin/bash
trap "echo 'ahoj ahoj, jsem signal USR1'" USR1
echo $$
while true
do
sleep 1
done



Catching signal in BASH, example 2

if [ ! -e $lockfile ]; then
trap "rm -f $lockfile; exit" INT TERM EXIT
touch $lockfile
critical-section
rm $lockfile
trap - INT TERM EXIT
else
echo "critical-section is already running"
fi



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www.mouser.com 
http://www.gme.cz/keramicke-kondenzator ... -p120-053/

0.01u je 10nF, 0.022u je 22n

www.mouser.com

http://cz.mouser.com/Home.aspx

skripta
http://elektross.gjn.cz/skripta/

Books
http://www.magsmoke.com/TH-101-Sheboygan-566-VCO.asp


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Capacitor Circuits 
http://www.youtube.com/watch?feature=en ... D-cNc6StVI

http://brightstorm.com/science/

http://www.youtube.com/watch?v=VrNLVQZ-CZo

simple vco
http://www.sentex.ca/~mec1995/gadgets/pll/pll.html

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SUPER SIMPLE THEORY OF OPERATION of the electronic components 
http://www.paia.com/bckit1/simpletheory.asp

Building Synthetizers
http://www.magsmoke.com/thomas_henry_books.asp

Stavebnice Voltik
http://e-shop.voltik.cz/stavebnice-volt ... 50047.html

Rozcestnik - DIY Effect Projects
http://www.squidoo.com/buildASynth

Electronic circuit simulator.
http://www.falstad.com/circuit/

Electronic circuit designer.
http://www.tina.com

Some other electronic cirtuit designers
http://www.electronics-lab.com/download ... index.html

A pad sound with Voyager
http://www.moogmusic.com/forum/viewtopic.php?t=8173

Roland Juno service manual
http://servicerepairmanuals.net/others/ ... ual-notes/

Roland Juno 80 schematics
http://www.fantasyjackpalance.com/fjp/s ... juno6.html

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Postfix: mail for root loops back to myself when using transport_maps (or, how make postfix use /etc/aliases BEFORE sending to smart relayhost? ) 
The aliases(5) file is used only for local(8) deliveries. When
mail is forwarded, you may be able to get by with the virtual(5)
alias map.

If the transport_maps or smart relay option is used and the server is a mail forwarder for a domain which he itself is a member of, then the root mail is also forwarded to the next hop as is defined in transport_maps or smart relay.

Iif the root mail should be sent to other address which has mailbox elsewhere than on a next hop, then the virtual must be used.

cat /etc/postfix/virtual

root@somedomain.cz             log@fsit.cz
root@somedomain.cz log@fsit.cz
localhost.somedomain.cz log@fsit.cz
root@localhost log@fsit.cz




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Linux: SAN 
snippets:

cat /sys/class/fc_host/host*/port_name | speed

multipath -v2 -d

http://www.softpanorama.org/Commercial_ ... ager.shtml

http://www.datadisk.co.uk/main/lvm.htm

----------


lvscan <- logical volume scan
lvremove vol1 vol2 <- remove logical vomumes
vgscan <- volume group scan
vgremove raid5 <- remove volume group
pvscan <- physical volume scan
pvremove /dev/cciss/c0d1 <- wipe the device rom lvm2


------------------------------------------------------
physical device to (pvcreate, pvremove, pvscan)
------------------------------------------------------
volume group of physical devices (vgcreate, vgremove, vgscan)
------------------------------------------------------
logical volume (lvcreate, lvremove, lvscan)
------------------------------------------------------

------------------------------------------------------
lvmdiskscan - reads all the partitions

---
pvs -vvvvv
vgs
lvs



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UNIX reminder: Sticky bits on directories 
Marking a directory sticky (t) directory users can have read and/or write permissions for that directory, but they can only remove or rename files that they own.
Marking a directory setgid (g+s) will make new files inherit the group ownership of the directory

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