2021-04-16 14:07:01 +0100, Martijn Dekker via austin-group-l at The Open Group:
> Op 15-04-21 om 22:43 schreef Harald van Dijk:
> [...]
> > In specific cases, the shell may be able to detect that these issues
> > cannot be a problem. In those specific cases, the optimisation should be
> > perfectly valid and any reasons why it should or should not be performed
> > are not of a technical nature.
>
> It makes sense now: instead of stdio, ksh93 uses libast's sfio, which on
> most systems is capable of peeking ahead on arbitrary files without
> consuming data. And it doesn't care if the input is a file or a string
> because both are turned into sfio input streams. Thanks to Chet and Harald
> for confirming that I've not overlooked some reason why the optimisation
> shouldn't be re-enabled.
[...]
Also consider a script such as:
#! /bin/sh -
trap 'echo "that was round $n"' EXIT
n=0; oncemore() { n="$(( n + 1 ))"; }
echo oncemore >> "$0"
Which keeps track of how many times it has been executed.
Or someone adding more lines to a script while it is being run,
expecting those to be interpreted.
(both quite far fetched scenarios though).
--
Stephane
