meaning of if [ -z $SOMETHING....] in bash shell

darwinianlo · 08-09-2007, 01:17 AM

Hi,
I have the following in a bash script file if [ -z "$SOMETHING" ]
I have searched for the -z option for an hour in Bash References, every other option is covered except for '-z' I assume this means is $SOMETHING defined in the environment but can anyone give me a definitive answer.

unSpawn · 08-09-2007, 01:21 AM

I applaud you searching around but "man test" is what you're looking for (string with length zero).

darwinianlo · 08-09-2007, 02:37 AM

I never would have guessed 'man test', but surprised I couldn't google for if [ -z,

thanks for the help.

chrism01 · 08-09-2007, 03:21 AM

To google it you'd prob need single quote marks around that.

Daws · 08-09-2007, 06:05 AM

"man [" would have worked too.

syg00 · 08-09-2007, 06:35 AM

And people wonder why *nux is considered not newbie friendly ...
For the greater proportion of the human race, that is just too arcane.

colucix · 08-09-2007, 08:57 AM

Quote:

Originally Posted by syg00

For the greater proportion of the human race, that is just too arcane.

Not if a newbie had the patience to read a good beginners' guide!

student04 · 08-09-2007, 10:34 AM

Quote:

Originally Posted by darwinianlo

Hi,
I have the following in a bash script file if [ -z "$SOMETHING" ]
I have searched for the -z option for an hour in Bash References, every other option is covered except for '-z' I assume this means is $SOMETHING defined in the environment but can anyone give me a definitive answer.

Example 7-2 in
http://www.tldp.org/LDP/abs/html/testconstructs.html

rupertwh · 08-09-2007, 11:02 AM

Quote:

Originally Posted by syg00

For the greater proportion of the human race, that is just too arcane.

I would hazard a guess that "the greater proportion of the human race" isn't involved in shell scripting at all. Which kind of makes your point moot.