Re: initialisation bash variables

[Francky Leyn]

On 8/15/2011 9:24 PM, Stephane CHAZELAS wrote:
> 2011-08-15, 17:15(+02), Francky Leyn:
> > Hello,
> >
> > if you have a variable, say VAR,
> > and you don't assign it a value,
> > and afterwards you test it,
> > what is the value of $VAR then?
> >
> > random, or an empty string?
> [...]
>
> Upon startup, the shell makes one shell variable per environment
> variable whose name is compatible with shell variable names.
>
> So for instance, if bash receives "VAR=foo" in its environemt,
> $VAR will expand to foo. If it's passed "1=bar", $1 will not be
> affected, and it's the same for a few special variables of the
> shell.
>
> If passed "A+B=C" or "=D" for instance, that obviously won't be
> mapped to shell variables. Some shells do discard variables from
> the environment that can't be mapped to shell variables. That's
> not the case of bash.

If you don't initialise a sh/bash variable, and ask it up
afterwards, which value does it have then? Is that random
or the empty string?

At the moment I'm doing the following:

VAR=FALSE
# some command line procesing, that can set VAR to "TRUE"
if [ $VAR = TRUE ]; then
...
fi

Must I effectively write that VAR=FALSE?
Or will the script work fine without?

Also, can't I write the test as

if [ $VAR ]; then
...
fi

Regards,

Francky