Issue
is it possible to specify non-capturing groups in sed?
if so, how?
Solution
The answer, is that as of writing, you can't - sed does not support it.
Non-capturing groups have the syntax of (?:a)
and are a PCRE syntax.
Sed supports BRE(Basic regular expressions), aka POSIX BRE, and if using GNU sed, there is the option -r
that makes it support ERE(extended regular expressions) aka POSIX ERE, but still not PCRE)
Perl will work, for windows or linux
examples here
https://superuser.com/questions/416419/perl-for-matching-with-regular-expressions-in-terminal
e.g. this from cygwin in windows
$ echo -e 'abcd' | perl -0777 -pe 's/(a)(?:b)(c)(d)/\1/s'
a
$ echo -e 'abcd' | perl -0777 -pe 's/(a)(?:b)(c)(d)/\2/s'
c
There is a program albeit for Windows, which can do search and replace on the command line, and does support PCRE. It's called rxrepl. It's not sed of course, but it does search and replace with PCRE support.
C:\blah\rxrepl>echo abc | rxrepl -s "(a)(b)(c)" -r "\1"
a
C:\blah\rxrepl>echo abc | rxrepl -s "(a)(b)(c)" -r "\3"
c
C:\blah\rxrepl>echo abc | rxrepl -s "(a)(b)(?:c)" -r "\3"
Invalid match group requested.
C:\blah\rxrepl>echo abc | rxrepl -s "(a)(?:b)(c)" -r "\2"
c
C:\blah\rxrepl>
The author(not me), mentioned his program in an answer over here https://superuser.com/questions/339118/regex-replace-from-command-line
It has a really good syntax.
The standard thing to use would be perl, or almost any other programming language that people use.
Answered By - barlop Answer Checked By - Terry (WPSolving Volunteer)