[plug] How to check for an empty string in a bash script.

[Bevan Broun]

on Wed, Dec 15, 1999 at 10:44:33AM +0800, Buddrige, David <david.buddrige at mitswa.com.au> wrote:
> Hi all, 
> 
> I have the following code in a bash script that I am writing...
> 
> if [ THE_PATH="" ]; then
> 	echo "The Path is:" $THE_PATH
> 	echo "FAIL! FILE DOES NOT EXIST."	
> fi
> 
> In another part of the script, the variable "THE_PATH" is populated with a
> filename that is the result of a search of the filesystem.  If the file was
> not found that value should be empty.  However, when I run this code, it is
> printing out the filename for which I searched (indicating that the variable
> "THE_PATH" is NOT empty, yet still it is making into the TRUE part of this
> if statement and subsequently echoing "FAIL! FILE DOES NOT EXIST."
> 
> My question:  How does one check a variable in a bash script to see if it is
> empty?

see http://207.213.123.70/book/ for an online bourne shell programming
reference. I think you are after -z 

if [ -z $THE_PATH ];then

BB
-- 
Bevan Broun                                           ph (08) 9380 1587
Computer Systems Officer                             fax (08) 9380 1065
Dept. Electrical and Electronic Engineering      
University of Western Australia                                 rm. G70