Re: [Help-bash] confusion of shell's new option compat41

[MaShimiao]

On 01/17/2013 11:29 AM, Chet Ramey wrote:
> On 1/16/13 9:21 PM, MaShimiao wrote:
> > On 01/17/2013 03:42 AM, Chet Ramey wrote:
> > > On 1/16/13 1:06 PM, Ma Shimiao wrote:
> > > > According to changelog and manpage, I find compat as a new option is added.
> > > > I have read manpage for many times. But I actually can't find out what it
> > > > affects.
> > > > And I don't understand what special character means.
> > > >
> > > > ManPage as follow:
> > > > compat41
> > > >               If set, bash, when in posix mode, treats a single quote in
> > > > a dou‐
> > > >               ble-quoted  parameter expansion as a special character.
> > > > The sin‐
> > > >               gle quotes must match (an even number) and the characters
> > > > between
> > > >               the single quotes are considered quoted.  This is the
> > > > behavior of
> > > >               posix mode  through  version  4.1.   The  default  bash
> > > > behavior
> > > >               remains as in previous versions.
> > > >
> > > > Could someone give me a example shows how to use compat41?
> > > Look at what a bash-4.2 instance running in Posix mode does with this:
> > >
> > > echo "${HOME+'foo}"
> > >
> > > with and without compat41 enabled.
> > I test in Fedora16 and bash-4.2.28. there is nothing difference.
> That's actually a different problem -- the logic in bash-4.2 is broken for
> setting the compat41 option.  It's fixed in the development version (which
> is what I was testing on):
OK, I see. Thank you for helping me to solve the puzzle.
> $ ./bash ./x25
> 4.3.0(21)-devel
> 'bar
> ./x25: line 10: unexpected EOF while looking for matching `''
> ./x25: line 11: syntax error: unexpected end of file
> $ cat x25
> echo $BASH_VERSION
>
> set -o posix
> foo=bar
>
> shopt -u compat41
> echo "${HOME+'$foo}"
>
> shopt -s compat41
> echo "${HOME+'$foo}"