Re: null command and parameter expansion for "Display error if null or unset"

[Dave Rutherford]

On 7/31/06, Poor Yorick <org.gnu.lists.bug-bash@pooryorick.com> wrote:
> The following line does not perform the "echo" command.
>
> : ${FAKEVAR?} || echo hello
>
> This seems inconsistent, since the return status is set to one, not to mention 
> that the null command is documented to return a zero exit code.  It would be a 
> convenient and concise syntax for acting on unset variables.

Try this and then run your script:

export FAKEVAR="echo This could have been rm -rf $HOME"

to see why not to do it this way.

On the other hand, if you already know FAKEVAR is not set,
why are you performing a test?

Dave