Re: Feature request: plain option for gsub

[Roberto Ierusalimschy <roberto@...>]

> I think this already demonstrates my point. Coming up with a regex
> that is safe and escapes everything is not trivial.
> 
> [...]
> >
> > On my system, '%p' does not match '[+$^]', so '%p' should become '[%p+$^]'.

This seems like a bug in his system (or else he is using some weird
locale...). '%p' corresponds to 'ispunct', and the C standard says this:

  In an implementation that uses the seven-bit US ASCII character set, the
  printing characters are those whose values lie from 0x20 (space) through
  0x7E (tilde);

  [...]

  In the "C" locale, ispunct returns true for every printing character for
  which neither isspace nor isalnum is true.

So, '[+$^]' must be all punctuations (and therefore match '%p').

If you assume a correct libC and a sane locale, '%p' is all you need.

-- Roberto