[SLUG] Shell Script question

["Aaron Binns" <abinns@xxxxxxxxxxxxxxxxxxxxxx>]

I don't have any manuals handy for this one so I thought Id ask the list my
newbie question.

I am writing a small shell script for work which reads in comma separated data
and parses it to another program. I want to check each field to see if it is
blank and if so exchange the blank for two single quotes (ie: '' ).

I am trying to use an if statement right now, but I cant figure out how to
represent a blank.

if [ $field -eq "" ]
then $do_something
else $do_something_else
fi

What's wrong with the above picture?

Aaron