Shell Programming and Scripting

Hi there

I have a script which is running a remote command on hundreds of boxes, it takes around 5 minutes to return an output from this command and because i am running this all from a central box, it goes off to each box in my for loop sequentially meaning that my script will wait for output before moving to the next machine

so as an example i will use the command `sleep 30`. I tried putting an ambersand into the script to no avail...the output on my central server still sits and waits for each box to sleep for 30 seconds rather than sending the command off to a box, letting that box deal with it and moving onto the next box with no delay

an example

Code:

for hostname in $list
do
/usr/ucb/echo -n  "$hostname - "
ssh $hostname 'sleep 30 &'
done

output ....ZZZZzzzzz

Code:

myserver1 -                       (waits 30 seconds then..)
myserver2 - 
..
..
..

Is there a way to do this ??

First of all, you'll want the "ssh" command to return. So you add the ampersand to the ssh command, not (only) the sleep command.

Second problem: as the ssh returns, the remote server might terminate the process. Use "nohup" to fix that.

ssh $hostname 'nohup sleep 30 &' &

How's that do?

ill give it a go, be right back

mmm, didnt work,

I added the & to the nohup command first and the central script still waited 30 secnonds before moving on to the next box.

Adding the additional & to the overall ssh command, did the same thing but just put it all in the background on the central server, so i didnt get any output ....still took just as long

any other ideas?

try this:

ssh $hostname 'nohup sleep 30 > /dev/null 2>&1 &'


SSH Frequently Asked Questions

cheers Minkie youre a legend