let str = replace_str str "\r" "\\r" in
let str = replace_str str "\n" "\\n" in
let str = replace_str str "\t" "\\t" in
let str = replace_str str "\000" "\\0" in
let str = replace_str str "\r" "\\r" in
let str = replace_str str "\n" "\\n" in
let str = replace_str str "\t" "\\t" in
let str = replace_str str "\000" "\\0" in