I have Slackware 10.1 installed and I logg as a root.

I was trying to use cron, I wrote commands to crontab file, but although it writes commands in log file there is no effect of that, commands are not executed. For example

* * * * * /bin/date

* * * * * /bin/echo "hello"

Nothing is showed on the screen.

The command
* * * * * /bin/chown root /home/ftp/*
also has no effect

the output of those commands will be emailed to the user who's crontab it is, in your case root, and not to the screen.

If you have a mail server installed and configured, look in root's mailbox or whoever recieves root's mail. Otherwise there should be entries in your cron log file complaining it can't email the output

Oh looking reading the rest of your post the above isn't your problem, but it is why the output of cronjobs never gets output to the screen, does `crontab -l` show your jobs listed? If not then the commands haven't been loaded into cron.

I put all my cronjobs in a file say ~/cron.tab and then run `crontab cron.tab` as the user to load the jobs when I update the cron.tab file

add this as the first line:

Thank you for your help. I have at the beginning of my crontab file:
MAILTO="" and there are complaints in log file

'failed user root parsing MAILTO="" '

but it appears only once after updating crontab file (to update I do the same as you do)

I tried another command and this time it worked.

Could I redirect the output so it shows the effect of some commands on the screen?

I suppose you could redirect the output to a terminal, for example though it will only work if the person doing the echoing is logged in at that terminal otherwise you will get permission denied, unless you do it as root