It is, regrettably, not the case that all people who work as software engineers can e.g. code a for loop which counts the numbers of lower-case As in a string. This is true even if you spot them the syntax for a for loop and finding the Nth character in a string. It is equally true if you allow them to complete the task in isolation, at their own computer, given an arbitrary amount of time to complete it.

I am, naturally, constrained from saying "Here's a list of three of them." It would not be difficult.

It is also, regretfully, not the case that all applications one receives to an advertised position of Senior Ruby on Rails Programmer would be from people who had ever opened a command line.

Both of these are very difficult things to accept. They may be even more difficult to accept if one is extraordinarily smart/diligent and one studies/works solely in organizations which apply brutal IQ/diligence filters before one is granted even a scintilla of the admission committee's time.

I remember, rather vividly, the first time I figured out that an engineer couldn't program. I was attempting to tell him where a value was being assigned in a program. After failing to do so over email, I went over to his desk and asked him to navigate to the file at issue. He was unable to do so. I told him I would do it, assuming that he was unfamiliar with the directory structure in that part of the program, and opened the file. I then said "So you see, the assignment is made in the fooBar subroutine." He couldn't find the fooBar subroutine. I said "It is the third method on your screen." He couldn't find it. I said "It is this one, here, which I am pointing to with my finger." He said "OK, that one. Where is the assignment?"

The fooBar subroutine was one statement long.

A coworker, having overheard the conversation, stopped at my desk later, and explained to me that, if I had pressing engineering issues, coworkers X and Y would be excellent senior systems engineers to address them to, but that Z should be allowed to "continue to devote his full attention to work which he is well-suited for."

The industry has many destructively untrue beliefs about hiring practices. That there exist at least some people who are not presently capable of doing productive engineering work is not one of these beliefs.