Hello

I'm trying to write shell script "replace.sh" but I have following problem :
My script take three parameters like this:
./repalce.sh <pairs > <input_file > < output_file >
Where
<pairs> = p1/w1,p2/w2 , .. ,pn/wn .
My script change all ocurrences p1 to w1 , p2 to w2 ... pn to wn
in <input_file > and write all the changes to output_file .
I'm trying to write the script with 'sed' but I have problem with the
strange argument <pairs > - there is no space between p1/w1,p2/w2,.. ,pn/wn
but only ',' .

I was trying to split <pairs> by changing ',' sign on space , but it don't work.