Editing crontab via ksh

Hi all,

I am trying the following

I am hoping that the crontab would be changed.
but it prints the previous crontab and says

Can anyone tell me the correct ksh command that should be used here?
I don't want to edit the crontab with crontab -e, I need to edit it via ksh.

Thank you,
Sara

crontab -l > cron
echo "#this is a test" >> cron
crontab cron

Super! Thanks