choice of control operators in scripts

[Denys Vlasenko]

On Monday 12 May 2008 23:06, Paul Fox wrote:
>  > > If you fell paranoid today (highly recommended),
>  > > add x"" to guard against less than ideal implementations of []
>  > > which can be confused by e.g. foo=-n :
>  > >
>  > > [ x"$foo" = x"bar" ]
>  > 
>  > I have no experience of shells that are _so_ buggy.  Do you mean this:
>  > 
>  > [ x-n = xbar ]
>  > 
>  > might confuse any non-buggy shell?
> 
> no.  he means that this:
>   [ "-n" = "bar" ]
> 
> might confuse a shell that interprets it as:
>   [ -n = bar ]
> 
> i've never seen such a shell.  i think adding the 'x' "just in
> case" is very ugly.

It's not "just in case". There are shells and [ programs
which are known to be buggy. Hell, not so long ago bbox's
one was fixed for a similar bug!

> just putting the args to test in double 
> quotes has always been enough for me.

Double quotes are removed before parameters are passed to the executable
(or shell builtin), and as such they cannot matter.

[ -n = bar ] works because [ has code
which decides that if you have 3 args, it must be "val1 op val2". etc.
Look into test.c in bbox tree.
--
vda