Re: grep -P in OF template Makefile: really useful?

[Julien Bect]

Le 04/03/2017 à 23:31, Mike Miller a écrit :
> On Sat, Mar 04, 2017 at 23:18:29 +0100, Julien Bect wrote:
> > Hi everyone,
> >
> > The template Makefile for OF packages
> > (https://octave.sourceforge.io/templates/Makefile) contains this line:
> >
> > PKG_ADD := $(shell grep -sPho '(?<=(//|\#\#) PKG_ADD: ).*' $(CC_SOURCES)
> > $(M_SOURCES))
> >
> > It turns out that this can cause problems on some platforms where grep -P is
> > not supported [1].
> >
> > Could anybody familiar enough with regexps tell me if the -P flag is
> > actually useful for this particular regexp?
> >
> > If it is, could we find a way to rewrite the regexp that would not require
> > PCRE?
> I guess you're using the lookbehind syntax to just avoid matching that
> part of the line when using the -o option?

I have no idea why it is written like that.  I didn't write it.


> That looks like overkill to
> me. The -h and -o options are also not specified by the POSIX definition
> of grep.
>
> IMHO this is a much safer and more portable alternative:
>
>    sed -n 's/^\(##\|\/\/\) PKG_ADD: \(.*\)/\2/p' ...


I will try that, thanks.