add text start every line 1

[cbsm]

As you see with my question, I do not use unix script very often.
This is what i'd like to do :
I have a text file (.csv).
I want to add a few characters (";;;") at the start of each line :
test;abc;def
becomes
;;;test;abc;def

I tried different sorts of sed commands without any success.
for example sed -i "s/*/;;;*/g" myfile.csv > newfile.csv
I get the error "sed: illegal option --i"

Many thanks !

 

[hoinz]

A hint: ^ in sed means 'beginning of the line',
and so try:

sed -e "s/^/;;;/" myfile.csv > newfile.csv