On Thu, Dec 27, 2018 at 7:37 PM G. Branden Robinson <g.branden.robin...@gmail.com> wrote: > > At 2018-12-27T18:39:26-0600, Peng Yu wrote: > > What I meant in my original email is that I want something for testing > > if there is a command line argument (one or more, the exact number > > does not matter). $# gives more than that info, because it tells not > > only whether is any command line argument, but also how many. This > > could lead to slower performance if the goal is to just test if there > > is an argument. > > You should look into how integer comparisons are done in hardware. > > For instance, comparison and subtraction operations are often comparable > (or even identical) in cycle count because they both perform a > subtraction "under the hood". You need to be programming in assembly > language to influence execution at such depths. > > See, e.g., > > https://www.quora.com/What-is-the-difference-between-cmp-and-sub-instruction-in-8086microprocessor > > As others have noted, if you are worried about marginal performance > impacts this small, margin you are probably writing in the wrong > language, or distracting yourself with tiny details when you do not even > know the cyclomatic complexity of your code or the big-O classification > of your algorithms. > > Attack those problems first, and see what you discover.
The problem is that bash is not systematically profiled for performance at all. I am doing it step it by step. There are many more that I have already tested. You can not dismiss this one just because it may not have a large impact. -- Regards, Peng
