[CALUG] Shell script question.

[Jim Bauer]

Brian Debelius wrote:
> Hi,
> 
>    Looking at Bacula scripts and other scripts, I see a test for an 
> empty string performed by adding an 'x' before the variable, and then 
> comparing this to another string that is just an 'x'.
> 
>    The shell test function has a -z string test that returns true if the 
> string is empty.
> 
> It appears to me that more people use the 'x' comparison.  Is there a 
> technical reason why one would be preferable to the other?
> 
>     Why would you do this:
> 
> if [ "x$var" = "x" ]; then
> ...
> fi
> 
>    Instead of this:
> 
> if [ -z $var ]; then
> ...
> fi

To protect against an error if var was something like '-a'.  Most modern
shells don't get tripped up over things like that.  But older systems
would generate an error.

And your -z version above has a bug.  Try it with var="a b".
Use "$var" not $var to fix it.