Moving sources (base/ports) from /usr

[Polytropon]

On Wed, 20 May 2020 13:49:19 +0200, Ede Wolf wrote:
> Sometimes, being pedantic helps quite a bit:
> 
> ... (fresh login)
> # echo $SOURCEDIR
> /clutter/src
> # env | grep SOURCEDIR
> #
> # SOURCEDIR="/clutter/src"
> # export SOURCEDIR
> # env | grep SOURCEDIR
> SOURCEDIR=/clutter/src
> 
> Even if this distinction is currently raising more question than it 
> answers, it at least explains the behaviour.

It does. My assumption (and therefore not thinking about this
possibility) was that you had set and exported (!) the variable
to the environment. The common forms

	FOO="bar"
	export FOO

and

	export FOO="bar"

are the forms typically found when you want to modify tne
environment, and _that_ is what's being passed from one instance
of the shell to the next instance (subshell). Regular variables
do not get passed that way:

	$ FOO=bar
	$ echo $FOO
	bar
	$ sh
	$ echo $FOO
	
	$ _

If you use "export" here, you can easily see the difference:

	$ FOO=bar
	$ echo $FOO
	bar
	$ export FOO
	$ sh
	$ echo $FOO
	bar
	$ _

The mentioned form

	$ export FOO=bar

would lead to the same effect. Checking with "env" is a good
idea if you want to explicitely (!) confirm that a certain
variable is set in the environment, not just as a mere shell
variable.

This doesn't just apply to shell scripts invoked by shell scripts,
but also to program that query *envp[], the (optional) third
parameter of the standard main() function.



> And I know I need to rethink my understanding of shell vs. environment 
> variables (and the corresponding files).

The files can set shell variables and environmental variables.
The case for _which_ kind of shell this applies (login shell,
interactive shell, scripting shell) depends on the file name,
as explained in "man sh", section "Invocation".



> Thanks for the heads up, with that in mind I'll reread the comment on 
> sh(1) and .shrc from before and, well, have a talk with my favourite 
> search enginge.

It's a search engine, not a listening engine. ;-)

However, it is not a bad idea to visit fundamental knowledge
and shell basics from time to time. It makes life easier,
especially for those corner cases where you expect a certain
behaviour, but it strangely does not happen.



-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...