How often does gnucash update stock quote?

[Chris Henderson]

I am tracking some stocks in two different stock market in two
different time zones. Does gnucash update stock quote in real time
while it's open and when the stock market is open for that time zone
or do I need to go to tools - price editor - get quotes every time I
need an updated price or does gnucash update stock quote every time I
open and close the application itself?

I have noticed section 8.6.3.2. of
http://gnucash.org/docs/v2.4/C/gnucash-guide/invest-stockprice1.html
but if I do

/Applications/Gnucash.app/Contents/MacOS/Gnucash --add-price-quotes ~/foobar
Don't have write access to /Library
dyld: DYLD_ environment variables being ignored because main
executable (/bin/ps) is setuid or setgid
Application Path /Applications/Gnucash.app/Contents/MacOS/Gnucash-bin
Found Finance::Quote version 1.18

cat ~/foobar
cat: /Users/tanman/foobar: No such file or directory

Thanks.