Re: NON-trivial regular expression problem (could not find on google)

[William Park]

In comp.unix.shell Instant Democracy <democrat@india.com> wrote:
> "dir.name/../dir/../file"
> "dir/../d2/../file.ext"
> "d1/d2/../../file.ext"
> 
> The "" are part of the string, and not just string delimiters. These
> strings are inside regular text on the line. The paths are never
> absolute so that you will not encounter "/d1/file.ext".
> 
> The task is to eliminate patterns such as 
>    DIRNAME/../
> from the path because they are redundant.
> 
> For lines which do not have ../.. in them, this is
> trivial, for example by regexp in sed, emacs etc.
> 
> The real problem is constructing a regular expression for
> the DIRNAME before the /..
> 
> This DIRNAME can be described as a string that contains neither
> / not double-dot but anything else. Perhaps I am overlooking
> something else about DIRNAME.
> 
> The regular expression for the first two cases is demonstrated by this
> sed script although the lisp variants are identical.
> 
> sed 's,\(^.*\)\(/\|"\)\([^/][^/]*/\.\./\)\(.*"\),\1\2\4,'
> 
> The regex I use for DIRNAME is [^/]+ written above using * because
> sed is without plus.

What's wrong with that?  ie.
    sed 's,[^/]\+/\.\./,,g'

> 
> I will follow all the cross-posted newsgroups. If you prefer, because
> some people are allergic to any cross-posting, you can post your reply
> in just one of the groups pertaining to your application, ie 
> lisp/elisp/sed/awk.

-- 
William Park, Open Geometry Consulting, <opengeometry@yahoo.ca>
Linux solution for data management and processing.