Sed cannot convert upper case to lower case

Question

I want to change the variance of the "email address" in the lower case jSON message. I tried using sed, but could not, as the \ L option does not work for me. Did I miss something?

a="{"id":null,"enabled":true,"password":"","email":"[e-mail]","lastName":"Foo","firstName":"lol"}"
echo $a | sed -e 's/email:[[:graph:]].*,last/\L&/g'

Result:

{id:null,enabled:true,password:,{L}email:[e-mail],lastName:Foo,firstName:lol}

As a result, I want:

{id:null,enabled:true,password:,email:[e-mail],lastName:Foo,firstName:lol}

Answer 1

I am going to assume that you do not have GNU sed and therefore no access to \L. Try perl instead:

echo "$a" | perl -pe 's/(email:[[:graph:]]*,last)/\L\1/'

Answer 2

Here awk

awk -F, '{for (i=1;i<=NF;i++) if ($i~/email/) $i=tolower($i)}1' <<< "$a"
{id:null enabled:true password: email:[e-mail] lastName:Foo firstName:lol}