Very Computer

Why are the KornShell special built-in commands special?
I understand how they're treated differently, but why?
Historical reasons? Because they have side effects?

TIA,
Mike

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Mike Woinoski                      Pine Needle Consulting

: Why are the KornShell special built-in commands special?
: I understand how they're treated differently, but why?
: Historical reasons? Because they have side effects?
: TIA, Mike

There is absolutely no documentation that explains why some builtins
were and are designated as "special"; however, my experience indicates
that special builtins are those designated as those capable of
modifying the environment. This hypothesis is supported by the newest
version of ksh (ksh93) that now makes the "unset" builtin a "special"
builtin, which it did not used to be.

This could be another way of saying that these builtins are those that
have the side-effect of being able to modify the environment, yes....

BTW, how many times in someone's script have you seen:

var1=foo
export var1
var2=bar
export var2

Since every special builtin has "variable list separation" performed
for "free", and since the most logical optimization of code is to
minimize the number of commands iterated through, the below is
preferable, _and_ documented since V7 sh!

var1=foo export var1
var2=bar export var2

or even better, because most commands can take multiple arguments:

var1=foo var2=bar export var1 var2

P.S.    ... or even better yet, especially if one has a lot of variables to
        set and export:

        set -a
        var1=foo var2=bar ...

-Brian
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: Why are the KornShell special built-in commands special?
: I understand how they're treated differently, but why?
: Historical reasons? Because they have side effects?
: TIA, Mike

Because they (may) affect the environment in some way. For the previous
reason.  Of course.  As mentioned above, yes. See page 209 of B&K, new
edition.

Maybe I'm being dense, but I don't see the pattern here.

Mike

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Mike Woinoski                      Pine Needle Consulting