base 16 notes

data/base_16.md

@@ -3,6 +3,24 @@ title: "Base 16"
 tags: [ "data" ]
 ---
 
-```bash
+Base 16 numbers often use `0x` at the start, so '10' just means '10', but `0x10` means '10 in base 16' which means '16'.
+
+For small numbers, use `printf`.
+
+```sh
 printf "%x" $NUMBER
 ```
+
+For any number, use `bc`.
+
+
+```sh
+fortune | md5sum  | cut -d' ' -f1 | tr [:lower:] [:upper:] | bc
+```
+
+- Inputting base 16 uses `ibase=16`.
+- Outputting base 10 uses `ibase=10`
+
+```sh
+echo 'ibase=16;' $(echo cbb478ac825f0dce7671254be035d0bc | tr [:lower:] [:upper:]) | bc
+```