Dixi quod…
>Martijn Dekker dixit:
>
>>to be a bug in POSIX terms; 'exec' is supposed to launch a program that
>>overlays the current shell[2], implying the program launched by 'exec'
>>is always external to the shell.
>
>The built-in utility is “the program implementing command”,
>and, with exec, it is not returning to the shell.
POSIX even provides for that otherplace:
The term "built-in" implies that the shell can execute the utility
directly and
does not need to search for it. An implementation may choose to make any
utility
a built-in; [… something about special builtins]
And:
The special built-in utilities in this section need not be provided in a
manner
accessible via the exec family of functions defined in the System
Interfaces
volume of POSIX.1-2008.
This specifically means that builtins MAY be made available
to exec, and that that’s an expected modus operandi.
Whether “echo” is a builtin or not is an implementation detail.
Heck, things like “true”, “false”, … are (and others can be)
implemented in some operating systems by symlinking them to the
shell executable (either ksh93 *or* mksh… not even considering
busybox).
So whether the program code implementing the utility is part
of the same on-disc executable file as the shell, or even
implemented in terms of shell structures, is a transparent
implementation detail, as long as the shell replaces itself
with that utility (which boils down to just never returning
to the invoking shell and “without creating a new process”).
And we’ve already seen above that the “command” argument to
exec may be a builtin especially considering “Command Search
and Execution”. Heck, you can exec a function!
bye,
//mirabilos
--
11:56⎜«liwakura:#!/bin/mksh» also, i wanted to add mksh to my own distro │
i was disappointed that there is no makefile │ but somehow the Build.sh is
the least painful built system i've ever seen │ honours CC, {CPP,C,LD}FLAGS
properly │ looks cleary like done by someone who knows what they are doing
