Bash [ -z hello ]
And yet, the top search result is tldp. This is what #bash on freenode has to say about that site:>  The infamous "Advanced" Bash Scripting Guide should be avoided unless you know how to filter out the junk. It will teach you to write bugs, not scripts. In that light, the BashGuide was written: http://mywiki.wooledge.org/BashGuideNow, that site is on the second "page" of the search results.