Gary Robinson's Rants

Non-blocking raw_input for Python

I needed a way to allow a raw_input() call to time out. In case it's useful to anyone, I wrote this solution which works under Unix-like OS's.

Simply call nonBlockingRawInput("your prompt text", n) where n is the number of seconds you would like the prompt to wait until it times out. If it does time out, it will return with an empty string.

import signal

class AlarmException(Exception):
    pass

def alarmHandler(signum, frame):
    raise AlarmException

def nonBlockingRawInput(prompt='', timeout=20):
    signal.signal(signal.SIGALRM, alarmHandler)
    signal.alarm(timeout)
    try:
        text = raw_input(prompt)
        signal.alarm(0)
        return text
    except AlarmException:
        print '\nPrompt timeout. Continuing...'
    signal.signal(signal.SIGALRM, signal.SIG_IGN)
    return ''

[Edited Aug. 30, 2010 to fix a typo in the function name and generally improve formatting]

[Edited Feb 1, 2022 to add a tad more explanation, since the comments indicate people are still finding this!]

Snow Leopard Guest User data loss bug

I've seen a number of mentions today of a bug that can cause a Snow Leopard user to lose all their data:

The problem appears to manifest itself on machines which had the Guest account option enabled under Leopard and were subsequently upgraded to Snow Leopard. Users booting their machines have reported that upon start-up, they have been logged into the Guest account. Upon switching to their regular account, the affected users have been finding all of their user data missing and unrecoverable except from a backup. [MacRumors.]

One user reports a way to recover the lost data. Since it's buried in a discussion thread, I'm reproducing it here (also fixing a typo pointed out by a reader of this blog):

The files were still in /Users,
recovery was not too difficult.

1) su in terminal
2) mv username username.old
3) create account username
4) mv username username.new
5) mv username.old username
6) chown -R username username

I don't know whether it's a general fix. If you run into the bug and decide to try this solution, feel free to post your experience in the comments section!