The JSON variable is parsed in the shell to obtain the value of value1 corresponding to key1, as follows:

s="{"key1":"abc","key2":"value2","key3":"value3"}"
parse_json(){
echo "${1//\"/}" | sed "s/.*$2:\([^,}]*\).*/\1/"
}
value=$(parse_json $s "key1")
echo $value

----------------------
output abc