On Thu, Jun 22, 2000 at 05:25:06PM +1000, Cameron Simpson wrote:
> | > 1. if [ -n $dirname ] && [ \( -d $dirname \) -a \( -x $dirname \) ];
> | > then
> | > 2. if [ -n $dirname ] && [ -d $dirname ] && [ -x $dirname ]; then
>
> Well, it's only worth it for expensive tests or tests when some depend
> on success of others.
Actually, it's a good habit to use &&/|| in place of -a/-o for the reason
below.
> | Also, to use -a safely you have to put in those ugly
> | brackets :)
>
> Not so. They're only needed if you have precedence issues, which don't
> obtains in the examples cited.
Consider "$dirname" := "=", and we had
[ -d $dirname -a -x $dirname ]
Since = has the highest precedence among all operators, this becomes
[ \( -d = -a \) -d = ]
which causes an error.
This can be avoided by either using brackets or &&.
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