cvs commit: src/bin/test test.1

[John Baldwin]

On Thursday 27 July 2006 15:08, Yar Tikhiy wrote:
> yar         2006-07-27 19:08:21 UTC
> 
>   FreeBSD src repository
> 
>   Modified files:
>     bin/test             test.1 
>   Log:
>   Document that both sides of -a or -o are always evaluated.  This
>   "feature" doesn't seem to be in the standards or elsewhere, and
>   it is against what we are used to in C and sh(1), so put the
>   paragraph under BUGS.
>   
>   Pointed out by: dougb
>   MFC after:      3 days

This isn't a bug, it's the only way it can work.  What you are missing is that 
the shell has to evaluate the arguments and then pass them to test(1).  Thus, 
when you do:

if [ foo ] && [ bar ]; then
	...
fi

The shell runs evaluates all of '[ foo ]' as needed and runs it.  It then 
decides whether to evaluate and run '[ bar ]' after the first command runs.  
When you do:

if [ foo -a bar ]; then
	...
fi

The shell has to evaluate all of '[ foo -a bar ]' and run the single command 
and make the decision based on what it returns.

I don't think this is really a bug, it's more the fact of realizing that even 
if [ maybe optimized to be a built-in, when you are using it, you have to 
treat it as the shell executing a separate program, just as you would expect:

if grep -q ${FOO} < ${BAR}; then
	...
fi

To evaluate both ${FOO} and ${BAR} before running grep.

-- 
John Baldwin