2017-01-18 In addition to the test(1) command and its bracket alias, I wrote about yesterday, I felt the need to have a look at Korn shell's double bracket testing command as well. [0] In short: It was intentionally left out of POSIX because the problem was not seen in the test(1) command but in its misuse. I am happy about that because the closer you look at this double bracket thing, the more goosebumps you get: It works completely different to all other parts of the shell, defining new rules of evaluation and interpretation. This is not helpful! Some parts of the shell might be awkward, but at least they are consistent, and if you only get to understand a small set of rules, you understand the whole. This is the principle of Unix. The double bracket facility, however, breaks with this idea by making it easy but not simple. [0] https://debianforum.de/forum/viewtopic.php?f=34&t=163791#p1118374 http://marmaro.de/lue/ markus schnalke