Ok. I have solved the problem.
From what I understood, even if we run ruby script from cron, that doesn't mean that we have enough rights.
So, first I made: added one fix to sudoers - providing root with NOPASSWD.
Next: I check out all pathes in script as they must be full (i.e.:
Than I add SUDO command in my script:
<?php $test = shell_exec('sudo ruby /home/test/test.rb'); ?>
Don't forget also chmod +x file.php
In cron I used:
crontab -e * * * * * php5 /home/test/test.php
And that's all :) Now all works fine. Some of my mistakes:
don't forget to do test output from the file (i.e.: sh run.sh > test.txt);
Use mail alerter with cron, it may help as well
If you running something from cron - better use full path
Thanks mudasobwa for advices and time :)