Re: Why does "mapfile -d delim" (delim != '\n') use unbuffered read?

[Chet Ramey]

On 5/4/21 4:05 PM, Robert Elz wrote:
>      Date:        Tue, 4 May 2021 09:28:04 -0400
>      From:        Chet Ramey <chet.ramey@case.edu>
>      Message-ID:  <c8b1b097-d430-e840-017d-52a1a6a393d0@case.edu>
>
>    | The issue with the BSDs and terminal devices is that the current code
>    | only checks for -1/ESPIPE, but they return a different value for errno
>    | (EINVAL? I forget.)
>
> On traditional unix, since forever, lseek() on a terminal is simply a no-op.
> (The seek() sys call that preceded it, on 6th edition and earlier was the
> same.) No error, no effect -- or no useful effect, the "file offset" might
> get set, so you can't even:
>         pos = lseek(0,somewhere,0);
>         if (lseek(0, pos, 0) != somewhere)
>                 /* unseekable */
> as that would probably (seem to) succeed, but terminals don't use it.

Yeah, it looks like fstat/S_ISREG is the most portable mechanism.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/