Re: plus sign appears not to work as expected

[Bill Gradwohl]

On Tue, Feb 14, 2012 at 4:27 PM, Bob Proulx <address@hidden> wrote:

> Bill Gradwohl wrote:
> > address@hidden wrote:
> > > For grep, you need '^[[:alpha:]]\+'.
> >
> > That backslash did it.
> >
> > Now I'm going into the docs to find where it says I need a backslash for
> > the + but nothing for the *.
>
> It starts with this part:
>
>    grep understands two different versions of regular expression syntax:
>    "basic" and "extended."  In GNU grep, there is no difference in
>    available functionality using either syntax.  In other implementations,
>    basic regular expressions are less powerful.  The following description
>    applies to extended regular expressions; differences for basic regular
>    expressions are summarized afterwards.
>
> 'grep' handles basic regular expressions.  'egrep' is the old name for
> 'grep -E' and it handles extended regular expressions.  * is a basic
> regular expression and + is an extended regular expression.
>
> GNU grep handles both in a compatible way.  If you call 'grep' then it
> handles the basic regular expressions like * and also the extended
> expressions if the extended one is escaped.
>
> If you call it with 'grep' then you should use the basic syntax.  But
> the extended is available if it is escaped.
>
>  grep    '^[[:alpha:]]\+'
>
> If you call it with -E then you get the full extended syntax.
>
>  grep -E '^[[:alpha:]]+'
>
> Bob
>

Thanks Bob. I did find the explanation in the docs. Just one more example
of how poorly written the docs are.

So much of grep, bash, and a host of other utilities show their age by the
numerous patches and consequently convoluted docs that support them.

Now I realize why people are heading for things like Python to write
scripts as opposed to bash. Bash has too much baggage, as does grep. Python
starts from a clean slate and can ignore backward compatibility issues as
there are none. It's time to replace grep too to jettison antique idioms
and come up with a cleaner utility that does a modern job.

With new code comes new docs to support it, and less need of this type of
forum.


-- 
Bill Gradwohl