Re: altchars for base64

[Assaf Gordon]

Hello,

On 2020-03-15 12:12 a.m., Kaz Kylheku (Coreutils) wrote:
> On 2020-03-14 22:20, Peng Yu wrote:
> > Python base64 decoder has the altchars option.
[...]
> > But I don't see such an option in coreutils' base64. Can this option
> > be added? Thanks.
>
> # use %* instead of +/:
> base64 whatever | tr '+/' '%*'

The reason for alternative characters is typically do use then in URLs,
where "/" and "+" are problematic.

A new command "basenc" was introduced in coreutils version 8.31
(released last year) which supports multiple encodings.
One of these is a "web-safe" variant of base64, as defined in
RFC4648 section 5:

  $ printf '\376\117\202' | basenc --base64
  /k+C

  $ printf '\376\117\202' | basenc --base64url
  _k-C

regards,
 - assaf

P.S.
The other supported encodings are (basenc --help):

  --base64          same as 'base64' program (RFC4648 section 4)
  --base64url       file- and url-safe base64 (RFC4648 section 5)
  --base32          same as 'base32' program (RFC4648 section 6)
  --base32hex       extended hex alphabet base32 (RFC4648 section 7)
  --base16          hex encoding (RFC4648 section 8)
  --base2msbf       bit string with most significant bit (msb) first
  --base2lsbf       bit string with least significant bit (lsb) first