Re: [bug-gawk] There are cases where regexp in FPAT does not work

[arnold]

Thanks Wolfgang for your explanations. They are correct. I recommend
that Hyunho Cho review the section on regular expressions in the
manual, paticularly the bits about interval expressions.

Thanks,

Arnold

Wolfgang Laun <address@hidden> wrote:

> I should have explained this one as well:
> $ echo '{{111}} design will serve {{111}} ...' |
> awk '{ print FPAT; print $1; print $2; gsub($1,"xxx",$0); print  }'
> FPAT='{{[0-9]+}}'
> {{[0-9]+}}
> {{111}}
> {{111}}
> {{111}} design will serve {{111}} ...
>
> The pattern /{{111}}/ describes a string consisting of 111 times '{'
> followed by '}'. Making this a little easier to write, we can observe it
> working:
>
> $ echo '{{11}} design will serve {{{{{{{{{{{} ...' | awk '{ print FPAT;
> print $1; gsub($1,"xxx",$0); print  }' FPAT='\\{\\{[0-9]+\\}\\}'
> \{\{[0-9]+\}\}
> {{11}}
> {{11}} design will serve xxx ...
>
> This is an incomplete effort to make the matched string work as a pattern,
> disabling some magic characters:
>
> $ echo '{{111}} design will serve {{111}} ...' | awk '{ print FPAT; print
> $1; print $2; h=$1; gsub(/[\][{}*+]/,"\\\\&",h); print h; gsub(h,"xxx",$0);
> print  }' FPAT='\\{\\{[0-9]+\\}\\}'
> \{\{[0-9]+\}\}
> {{111}}
> {{111}}
> \{\{111\}\}
> xxx design will serve xxx ...
>
> -W
>
>
> On Fri, 8 Feb 2019 at 22:46, Hyunho Cho <address@hidden> wrote:
>
> > $ awk --version
> > GNU Awk 4.2.1, API: 2.0 (GNU MPFR 4.0.1, GNU MP 6.1.2)
> > Copyright (C) 1989, 1991-2018 Free Software Foundation.
> >
> > $ lsb_release -a
> > No LSB modules are available.
> > Distributor ID: Ubuntu
> > Description:    Ubuntu 18.10
> > Release:        18.10
> > Codename:       cosmic
> >
> > $ uname -a
> > Linux EliteBook 4.18.0-14-generic #15-Ubuntu SMP Mon Jan 14 09:01:02
> > UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
> >
> >
> > #####################################################################
> >
> >
> > There are cases where regexp in FPAT does not work.
> > If i change "{{111}}"  to "{{AAA}} in input string and
> > FPAT='{{[A-Z]+}}' then it WORK
> >
> >
> > ### FPAT='{{[0-9]+}}' NOT WORK!
> > $ echo '{{111}} design will serve {{111}} ...' |
> > awk '{ gsub($1,"xxx",$0); print  }' FPAT='{{[0-9]+}}'
> > {{111}} design will serve {{111}} ...
> >
> > ### FPAT='{{[0-9]+}' NOT WORK!
> > $ echo '{{111}} design will serve {{111}} ...' |
> > awk '{ gsub($1,"xxx",$0); print  }' FPAT='{{[0-9]+}'
> > {{111}} design will serve {{111}} ...
> >
> > ### FPAT='{[0-9]+}' WORK!
> > $ echo '{{111}} design will serve {{111}} ...' |
> > awk '{ gsub($1,"xxx",$0); print  }' FPAT='{[0-9]+}'
> > {xxx} design will serve {xxx} ...
> >
> > ### FPAT='{[0-9]+}}' WORK!
> > $ echo '{{111}} design will serve {{111}} ...' |
> > awk '{ gsub($1,"xxx",$0); print  }' FPAT='{[0-9]+}}'
> > {xxx design will serve {xxx ...
> >
> > ###  WORK!
> > $ echo '{{111}} design will serve {{111}} ...' |
> > awk '{ gsub("{{[0-9]+}}","xxx",$0); print  }'
> > xxx design will serve xxx ...
> >
> > ### NOT WORK!
> > $ echo '[[111]] design will serve [[111]] ...' |
> > awk '{ gsub($1,"xxx",$0); print  }' FPAT='\\[\\[[0-9]+]]'
> > [[11xxx] design will serve [[11xxx] ...
> >
> > ### WORK!
> > $ echo '[[111]] design will serve [[111]] ...' |
> > awk '{ gsub("\\[\\[[0-9]+]]","xxx",$0); print  }'
> > xxx design will serve xxx ...
> >
> >