do something else while waiting for an event, such as reboot

until (ssh [email protected] 2> /dev/null); do date; sleep 15; done
until (ssh [email protected] 2> /dev/null); do date; sleep 15; done In this case will execute "date" then "sleep 15" until we are able to ssh into server, such as after a reboot Could also be like: until ( ping 10.1.1.39 1> /dev/null); do echo "server 10.1.1.39 is down"; sleep 15; done
Sample Output
admin01 00:34 ~/ $ until (ssh [email protected] 2> /dev/null); do date; sleep 15; done
Tue Mar  8 00:34:57 PST 2011
Tue Mar  8 00:35:12 PST 2011
[email protected]'s password: 
Last login: Mon Mar  7 13:12:20 2011 from server001
[[email protected] ~]#

8
By: greggster
2011-03-08 08:42:12

What Others Think

Not that it makes any significant difference in this case, but those parentheses around the commands are not necessary. Also, that ping command will go on pinging forever unless you give it a count with the -c option, and as far as I'm aware, GNU ping only sets an error code if it also fails to transmit any packets. Which means, as long as ping's able to transmit its echo requests, 'echo "server 10.1.1.39 is down"; sleep 15' won't run even if ping doesn't receive any responses.
eightmillion · 498 weeks and 6 days ago
yes the ping will need a -c arg - else it will as you say ping forever...
greggster · 421 weeks and 4 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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