Re: magic/absurd bash interpreter/compiler ?

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:
> In comp.compilers Eric <eric@deptj.eu> wrote:
>
> (snip, I wrote)
> >> One problem with many unix shells is that redirection is done too early.
> >> Specifically, before an if test is done.
>
> > I am tempted to think that this is a conceptual misunderstanding, so an
> > example would be useful.
>
> From the man page for csh:
>
> "The single-command form of if does output redirection even if the
> expression is false and the command is not executed."
>
> echo false > file
> if( 1 > 2 ) echo true > file
>
> The if statement will open (and truncate) file before
> testing the condition. At least for csh, I didn't try others.
>
> -- glen
> [That's one of the many, many bugs in csh. In posix shells such as
> sh and bash, they do what you'd expect:
>
> if [ 1 \> 2 ]; then echo true > file; fi # doesn't create the file
> if [ 1 \> 2 ]; then echo true; fi > file # does create it
>
> -John]


csh is so broken, it's best ignored when talking about "Unix shells" in
general. Even more so when someone says "many Unix shells", since one
exception hardly counts as "many".


--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
[Several other people wrote to agree that csh is bad news. -John]

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