Re: Inconsistent quote and escape handling in substitution part of parameter expansions.

[Roman Rakus]

On 02/28/2012 02:36 PM, Chet Ramey wrote:
> On 2/28/12 4:17 AM, lhunath@lyndir.com wrote:
> > Configuration Information [Automatically generated, do not change]:
> > Machine: i386
> > OS: darwin11.2.0
> > Compiler: /Developer/usr/bin/clang
> > Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i386' 
> > -DCONF_OSTYPE='darwin11.2.0' -DCONF_MACHTYPE='i386-apple-darwin11.2.0' 
> > -DCONF_VENDOR='apple' -DLOCALEDIR='/opt/local/share/locale' -DPACKAGE='bash' 
> > -DSHELL -DHAVE_CONFIG_H -DMACOSX   -I.  -I. -I./include -I./lib  
> > -I/opt/local/include -pipe -O2 -arch x86_64
> > uname output: Darwin mbillemo.lin-k.net 11.3.0 Darwin Kernel Version 11.3.0: 
> > Thu Jan 12 18:47:41 PST 2012; root:xnu-1699.24.23~1/RELEASE_X86_64 x86_64
> > Machine Type: i386-apple-darwin11.2.0
> >
> > Bash Version: 4.2
> > Patch Level: 20
> > Release Status: release
> >
> > Description:
> >         The handling of backslash and quotes is completely inconsistent, 
> > counter-intuitive and in violation of how the syntax works elsewhere in bash.
> >
> >      ' appears to introduce a single-quoted context and \ appears to escape 
> > special characters.  That's good.
> >      A substitution pattern of ' causes bash to be unable to find the closing 
> > quote.  That's good.
> >      A substitution pattern of '' SHOULD equal an empty quoted string.  The 
> > result, however, is ''.  That's NOT good.  Suddenly the quotes are literal?
> >      A substitution pattern of '$var' SHOULD disable expansion inside the 
> > quotes. The result, however, is '[contents-of-var]'.  That's NOT good.  In 
> > fact, it looks like quoting doesn't work here at all.
> >      \\ is a disabled backslash, and the syntactical backslash is removed.  The 
> > result is \.  That's good.
> >      \' is a disabled single quote, but the syntactical backslash is NOT 
> > removed.  The result is \'.  That's NOT good.
> >
> >      It mostly looks like all the rules for handling quoting and escaping are 
> > out the window and some random and utterly inconsistent set of rules is being 
> > applied instead.
> >
> > Fix:
> >         Change parsing of the substitution pattern so that it abides by all the 
> > standard documented rules regarding quotes and escaping.
> It would go better if you gave some examples of what you consider
> incorrect behavior.  This description isn't helpful as it stands.
Maybe something like this:

# ttt=ggg
# ggg="asd'ddd'g"
# echo "'${!ttt//\'/'\''}'"
>  ^C
# echo "'${!ttt//\'/\'\\\'\'}'"
'asd\'\\'\'ddd\'\\'\'g'



Anyway, I thought that single quote retains its special meaning in 
double quotes.
$ echo "'a'"
'a'

RR