This gives people running bitcoind a way of getting alerts in a timely manner, instead of needing to poll with "getinfo" and parse the "errors" array.
Example usage in a bitcoin.conf:
alertnotify=echo %s | mail -s "URGENT: bitcoind alert" admin@service.com
The command string is passed to the shell, with %s replaced by the alert message enclosed in single quotes.
We really need a -setalertkey option to use a non-standard alert key for testing, along with tools to create alert messages. Make CAlert::CheckSignature() use a single pszAlertKey and then set that key appropriately at startup, as well as have a contrib/alerts directory with some simple Python scripts to create alerts. It'd let the unit tests include actual alerts with a known testing key too.
Runs a shell command when an AppliesToMe() alert is received.
%s in the <cmd> string is replaced with the alert.strStatusBar
message.
@petertodd : good idea. That can be done in a subsequent pull.
Reworked/rebased to whitelist the characters in the alert message, as suggested by @jgarzik.
ACK, though I wonder about the conditions of when fThread is true or false (and alertnotify will be in a free thread, or not)
fThread == false was implemented just so the unit test doesn't have to Sleep() and keep it's fingers crossed that it waited long enough for the thread to finish.
Normally fThread is true, so the main event processing loop doesn't wait.
You should mention it in the warning that's printed if you don't have a bitcoin.conf (with a username/password). That way people who are setting up Bitcoin for the first time are guaranteed to see it and consider using it.
Automatic sanity-testing: PASSED, see http://jenkins.bluematt.me/pull-tester/3d9d2d423bbdf97ef729b8c4a2dddc30a01e1415 for binaries and test log.
ACK