I often wondered about the circumstance which led to | because it felt like the oddest pipe in the world to me. Its zero pipe units long, its just an entry and an exit, bolted together. I thought = would have been much better. I guess there was a good reason that wouldn't fly. But then I learned there was some clumsy pre-ur-pipe notations which bolted what > and < do together somehow. I guess if you were there, it made perfect sense. Confusing as well that | and || both have to co-exist in the shell, one for IO redirection and process chaining, and one for expression short circuit operation. So, clearly a lexer is in the mix, which means maybe == could have worked. Thats a pipe! I also had long beer filled arguments about how if | was a process, not just IO bolting, it could be instrumented. Somebody said I should do that in tee and I did play with that a bit, putting a box on tee to say what flowed through the pipe. So, maybe the pipe symbol | could have been modified to be T and then you had a side flow to monitor on. Designing things is hard. I guess the reality is, you do the bare minimum neccessary to make it work. Anything else is adding cost. (I hesitate to say <- and -> might have worked too. few pipes are bi-directional. Also, the = is being used in ls -lF to denote what things are non-normal files...) G On Sun, Feb 25, 2018 at 1:07 PM, Doug McIlroy &lt;doug(a)cs.dartmouth.edu&gt; wrote: