hi,

I need to run a main script on a number of servers after sleeping for a random seconds. My plan is to add this random-number-selection-shell-script at the beginning of this main script.
Below is the idea:

random_list={0,1800,3600, 5400,....,86400}
sleep $random_list
..........
main script follows..
..........

Here $random_list should take a random value from the above list. Please help on this!!

Regards,
Emlyn Jose

Hi

You could use a bash array and pull a random item from the array.

Do you have a range?

perl -e 'print int rand(86400)'

or

od -d -N 2 /dev/urandom| awk '{print $2}'

Thank you for the codes above.
@Rinndalir: This works but I need values from the list of given values with 1800 as difference.
@Guttorm: This really works. But I am planning to give a range from 0 to 86400 with 1800 as difference. Can you please help me with that?
i.e., list = { 0 - 86400 }
so that $list will have values like 0,1800,3600, 5400,7200, ......., 86400.

Also it will be helpful if you explain the snippet. Like, i did not understand what echo ${list[$RANDOM ${#list[@]} ]} does But it does give the result.

BR,Emlyn Jose

You can't have incremental ranges (that I'm aware of) using {}
But you could always do this:

$RANDOM will produce a random number from 0-32767. In a nutshell to create a certain range you use the modulo function and so the equation below will generate numbers from 0 to X-1.

r=$(( $RANDOM % X ))

Guttorm's code generates a random number in the same manner using the number of elements in the array as X. So ${list[$RANDOM % ${#list[@]} ]} actually in the posted example is ${list[$RANDOM % 5]}. So the values will be list[0]=0, list[1]=1800 ... list[4]=86400.

As Sefyir posted you can create an array in a similar manner but is not required.


r=$(( $RANDOM%49*1800 ))