cron random

sometimes we need some random time added on cron jobs, since cron of different machines may need to I/O outputs between them. randomness of several seconds is needed to prevent I/O at the same time. for example, perl can do this in one line:

# perl -le 'sleep rand 9000' && *command goes here*

REF: http://stackoverflow.com/questions/9049460/cron-jobs-and-random-times-within-giving-hours