Re: [Help-bash] getting weird output out of 'echo' w/args

[Roman Rakus]

Changing the list to help-bash, I think this belongs here.

This is common misconception about filename expansion (globbing). Since 
globbing is done nearly always (*) people know only about "star" 
character. The fact is that "star", "question mark" and "opening 
bracket" (*, ?, [) all have special meaning for globbing. See 
http://www.gnu.org/software/bash/manual/bashref.html#Filename-Expansion

Many times I saw using tr like this:
somecommand | tr -s [a-z] ''
somecommand | tr -s [:space:] ' '

Please note that argument for tr undergo globbing (by bash), because it 
is not quoted.

RR

* It's not always, but it is good practise to double-quote variable 
expansions.

On 05/30/2013 10:56 AM, Chris Down wrote:
> Pierre is referring to the fact that [i++] is evaluated as a glob by
> the shell, the reason it doesn't work is because $i is postincremented
> instead of preincremented. You can see what he means here:
>
> $ shopt -u nullglob
> $ i=0
> $ while read a[++i]; do
> >      echo "${a[i]}"
> > done <<< hello
> hello
> $ shopt -s nullglob
> $ while read a[++i]; do
> >      echo "${a[i]}"
> > done <<< hello
>
> $
>
>
>
> On 30 May 2013 16:49, Davide Brini <address@hidden> wrote:
> > On Thu, 30 May 2013 08:53:48 +0300, Pierre Gaston <address@hidden>
> > wrote:
> >
> > > Missing quotes around [ ]  can be nasty eg
> > >
> > > #!/bin/bash
> > > shopt -s nullglob # sounds a good idea!
> > > .....
> > > .....
> > > i=0
> > > while read a[i++]; do
> > >    echo "${a[i]}" #  why oh why nothing is printed!
> > > done <<< "hello"
> >
> > It seems to me this has nothing to do with missing quotes around [ ], or I
> > don't get what you mean.
> >
> > --
> > D.