How to decode base64 string

echo "cmF3IGRhdGEK"  | base64 -d 

raw data

base64

Base64 encode or decode FILE, or standard input, to standard output.

With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.

-d, --decode

decode data

-i, --ignore-garbage

when decoding, ignore non-alphabet characters

-w, --wrap=,COLS/

wrap encoded lines after COLS character (default 76). Use 0 to disable line wrapping

--help

display this help and exit

--version

output version information and exit

The data are encoded as described for the base64 alphabet in RFC 4648. When decoding, the input may contain newlines in addition to the bytes of the formal base64 alphabet. Use --ignore-garbage to attempt to recover from any other non-alphabet bytes in the encoded stream.