env_helper

[Jeremy Huddleston]

On Mar 16, 2009, at 08:55, Bradley Giesbrecht wrote:

> On Mar 15, 2009, at 7:21 PM, Jeremy Huddleston wrote:
>
>> I think this is a bit too many files lying around.
>
> I really don't understand what the implied problem is here. Can you  
> explain?

Clutter is bad.  It's better to have everything in one file if  
possible.  This way if you have one port that wants to set PATH,  
MANPATH, C_INCLUDE_PATH, OBJC_INCLUDE_PATH, PKG_CONFIG_PATH, ... it  
just needs to create ONE file rather than one file per variable

>> Why have separate directories/files for each environment variable.
>
> That's the way path_helper does it.

Yes, and that is a problem.  It doesn't scale well.

>> It seems cleaner to me to have:
>>
>> ${etcdir}/paths.d contain a set of files (one file per port).   
>> These files are newline-delimited in the form:
>> ENVIRONMENT_VARIABLE=VALUE
>>
>> so you would have:
>>
>> ${etcdir}/paths.d/mysql contain:
>> PATH=/opt/local/lib/mysql5/bin
>>
>> ${etcdir}/paths.d/perl5 contain:
>> MANPATH=/opt/local/share/p5/man
>>
>> It would be nice to actually have this be backwards compatible with  
>> path_helper, so if ${etcdir}/paths.d/myapp contained:
>> /opt/local/lib/some/bin
> That's what my script does now.  paths.d is renamed PATH.d but  
> that's the only diff. The files in PATH.d can be written exactly  
> like path_helper files or they CAN use ${PREFIX} so the ports would  
> use the system could have pre-written support files that would just  
> be copied in place.

That's great, but that's only the backwards compatibility that I  
mentioned, not the main idea.  You said you have separate files per  
port per variable:
/opt/local/etc/env_helper/paths/<VARIABLE>/<PORT>

I'm saying we should have one file per port:
/opt/local/etc/paths.d/<PORT>

> So you would parse the file into left and right side values and add  
> them to the beginning of the current env var?
> echo $PATH
> /sbin:/bin
> becomes
> /opt/local/lib/mysql5/bin/sbin:/bin

I'm guessing you meant:
/opt/local/lib/mysql5/bin:/sbin:/bin

> This is obviously doable but it's more work then I wanted to put  
> into it before I knew whether or not there is even an audience.

I don't think it's any more work than what you currently proposed, and  
yes, there's certainly an audience.  I wanted to do this last year,  
but I never got around to it.

>> it would default to assume an implicit PATH=.  Similarly, it could  
>> support ${etcdir}/manpaths.d with an implicit MANPATH
>>
>> I thought about that last year, but I never got around to doing  
>> anything about it ;)
>
> If you or someone wants to contribute parsing left and right of  
> equal into vars go ahead and I'll support that.
>
> The thing is, when you have ENVIRONMENT_VARIABLE=VALUE how are you  
> going to know whether or not you should prepend current var values  
> with the new value and a path separator.

The same way you know now whether or not to prepend the current values  
with the new value and a path separator.  I don't understand the  
confusion.

MANPATH=${PARSED_VALUE}${MANPATH+:${MANPATH}}

> I think your script wound have to be smart enough to know what to do  
> with names.

I'm not sure what you mean by that.

> By having a path TYPE var we can drop anything in this dir and treat  
> it the same knowing nothing about the var name.

And by having a line of the form "TYPE=VALUE", we know the exact same  
information.

> I don't need to know what PERL5LIB is used for, it's in the paths  
> dir, I'm going to concat with sep.

You don't need to know what PERL5LIB is used for any more in the  
scenario that I proposed.  The scenarios are bijective, so there's  
nothing different in terms of expressibility or capability.  It's just  
a matter of organization.

Example (yes, this uses eval... no, I didn't feel like finding another  
way):

simple_parse() {
     local LINE VALUE VARIABLE
     while read LINE ; do
         VARIABLE=${LINE%%=*}
         VALUE=${LINE#*=}
         eval ${VARIABLE}=${VALUE}${!VARIABLE+:${!VARIABLE}}
     done < ${1}
}

~ $ cat test
MYVAR=1234
MYVAR2=4567:3223

~ $ cat test2
MYVAR=432
MYVAR2=467:33

~ $ simple_parse test

~ $ echo $MYVAR
1234

~ $ echo $MYVAR2
4567:3223

~ $ simple_parse test2

~ $ echo $MYVAR
432:1234

~ $ echo $MYVAR2
467:33:4567:3223