Re: [feature request] add associative array support to mapfile

[Chet Ramey]

On 12/17/20 11:58 AM, Léa Gris wrote:
> Le 17/12/2020 à 17:35, Chet Ramey écrivait :
> > One problem I see with it is that it assumes the introduction of word
> > splitting into mapfile, with the burden on the user to ensure that there
> > are exactly two resultant fields.
>
> It is just meant to be a replacement to looping on:
>
> IFS=<FieldSeparator> read -r -d <record delimiter> k v
>
> So yes it has only two fields per record/line regardless, the first IFS 
> character will delimit the key from the value, and the value is allowed to 
> contain any of IFS except newline, unless the record delimiter is assigned 
> a different character.
>
> The incentive behind this feature request is, to allow mapping key-values 
> pairs from a character stream/file, safely into a Bash's associative array 
> with a single built-in command.

Then these requirements suggest that the best way to proceed is to add a
loadable builtin to handle this case. You could start with the `csv' and
`cut' loadable builtins in bash-5.1, and could probably put together a `kv'
builtin in a couple of hours.

> These days, people are going out of their way to parse key value pairs out 
> of foreign config files or result streams from jq processed JSON.
>
> Maybe (it is clearly open to discussion), the associative array mapping 
> could be allowed to:
> - skip blank/comment only lines (1)
> - allow key without value
> - optionally trim trailing comment (1)

All of this would be better added to a new builtin, since it's all 
orthogonal to what mapfile provides.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/