Re: purposes of quotearg

On 2026-05-29 16:34, Pádraig Brady wrote:
> On 29/05/2026 23:51, Bruno Haible via Gnulib discussion list wrote:
>> Other purposes that I missed?
> Avoid printing shell meta-characters,
> which may cause side effects if pasted back to a shell command.

Also, avoid over-quoting, i.e., quoting that is unnecessary and 
therefore makes strings harder for humans to interpret.

Also, quote correctly, i.e., so that a parser for a particular notation 
will recover the original string unchanged, byte-for-byte.

As a corollary, do so portably, i.e., cater to idiosyncrasies of target 
parsers for the notation, even if they may have bugs. (In some cases, I 
expect, it's impossible to quote correctly and portably.)

Also, be able to quote strings correctly even if they contain NUL bytes 
or encoding errors.

It'd also be helpful to mention which goals are the most important, 
e.g., correctness is more important than avoiding over-quoting.

I've probably forgotten some goals....


>    * Avoid printing characters that are "unprintable" in the terminal's
>      encoding. If that encoding is not UTF-8, they would typically leave
>      no traces on screen, thus end up presenting misleading results. 

Although this is nice to have, it's not possible to avoid misleading 
displays in general even if we assume UTF-8, because many terminals 
swallow some Unicode characters with no visible effects (which they are 
required to do for characters like U+200B ZERO WIDTH SPACE). And even if 
they didn't silently swallow characters, this is just a subset of the 
more-general problem, a problem that also includes confusables.