Re: case modification won't work with pattern

[Chris F.A. Johnson]

On Thu, 10 Mar 2011, Chet Ramey wrote:

> On 3/10/11 9:04 PM, Clark J. Wang wrote:
> > On Thu, Mar 10, 2011 at 9:31 PM, Greg Wooledge <wooledg@eeg.ccf.org> wrote:
> >
> > > On Thu, Mar 10, 2011 at 10:22:12AM +0800, Jerry Wang wrote:
> > > >       var="abcabc"
> > > >       echo "var: ${var}"
> > > >       echo "replace the leading \"ab\" to uppercase: ${var^ab}" # expect
> > > to get "ABcabc" ?
> > >
> > > The documentation is a bit terse, admittedly.
> >
> >
> > Agree. Almost all of the poeple around me don't understand why it works that
> > way. Maybe some background of the feature requirement can help us to
> > understand better.
>
> The original requests were for a way to change the first letter or
> every letter to uppercase or lowercase, like ksh typeset -l/-u, using
> word expansion syntax (one request was for a new builtin command to
> do it).  That's what you get if you don't use the pattern part of the
> expansion.  I invented the pattern following the case specifier to allow
> each character to be separately modified.

  I suggested using parameter expansion with patterns in
  <http://lists.gnu.org/archive/html/bug-bash/2006-02/msg00020.html>:

$ foo=bar
$ echo ${foo^}  ## Convert first character
Bar
$ echo ${foo^^}  ## Convert all characters
BAR
$ echo ${foo^[a-m]} ## Convert first character that matches pattern
Bar
$ echo ${foo^^[a-m]} ## Convert all characters that match pattern
BAr

--
   Chris F.A. Johnson, <http://cfajohnson.com/>
   Author:
   Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress)
   Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)