The echo command can be used to convert a base 16 hexadecimal string to decimal integer. For example, lets say you have the following base 16 hexadecimal string.

`0x6599648e208ee4f6`

0x is the prefix, and 6599648e208ee4f6 is the base 16 hexadecimal string (there are 16 characters, hence base 16). The following command will convert 0x6599648e208ee4f6 to decimal. In this example, 7320993230861821174 is the decimal.

```
~]# echo $((0x6599648e208ee4f6))
7320993230861821174
```

You can also convert a decimal string to hexadecimal. In this example, decimal string 7320993230861821174 is converted back into hexadecimal, without the leading 0x prefix.

```
~]# echo "obase=16; 7320993230861821174" | bc
6599648e208ee4f6
```