How to replace comma by slash using sed in an UTF8 file

Shell Programming and Scripting
1

Hello all,

I'd like to replace "," by "/" in a utf8 file from postion X to Y. Comma "," is also defined as delimiter.

12345678901234567890,123456789012345,12345678901234567890,
aaaa,aaaa,aaaaa ,bbb,bbbb,bbbbb ,cccccc,cc ,

Result should be
12345678901234567890,123456789012345,12345678901234567890,
aaaa/aaaa/aaaaa ,bbb/bbbb/bbbbb ,cccccc/cc ,

Example:
replace "," by "/" from postion 1 to 20
skip "," in the postion 21
replace "," by "/" from postion 22 to 35
skip "," in the postion 36
replace "," by "/" from postion 37 to 56
skip "," in the postion 57

Thank you for your support

2

How about substrings?

OUT=$( echo "${IN:$(($X-1)):$(($Y-$X))}" | sed 's/,/\//' )

(Reference)