Re: [boost] Boost.Process article: Tutorial and request for comments

Subject: Re: [boost] Boost.Process article: Tutorial and request for comments
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2009-04-25 13:25:09

Hi,
----- Original Message ----- 
From: "Phil Endecott" <spam_from_boost_dev_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Saturday, April 25, 2009 4:13 PM
Subject: Re: [boost] Boost.Process article: Tutorial and request for comments

> 
> Boris Schaeling wrote:
>> On Tue, 21 Apr 2009 20:15:11 +0200, Phil Endecott wrote:
> 
>>> Re the environment: I'm not enthusiastic that you have copied the  
>>> environment into your own data structure.  Why can't your environment  
>>> type just wrap getenv() and setenv()?   i.e.
> 
>> The type environment is also used to setup a new environment for a child  
>> process, eg.:
>>
>> context ctx;
>> ctx.environment.insert(environment::value_type("PATH", "/newpath"));
>> launch(..., ctx);
> 
> Typically I would write:
> 
> fork();
> setenv("PATH","/newpath");
> exec();
> 
> So the new child process gets the parent's environment with any new 
> variables added or changed.  This seems a lot simpler than copying the 
> whole environment.

Yes, this seems much more efficient. So the Process library should use the environement filed as a list of environment variable to set on the child process.

>>> Why don't you boil it down to:
>>>
>>>    launch_process("notepad.exe");
>>
>> Currently the environment variables of the current process are not  
>> automatically inherited by a child process. I agree that it should be  
>> easier to launch a new process. But then environment variables should  
>> probably be inherited by default?
> 
> The environment is inherited across fork() and all those versions of 
> exec() that don't explicitly set a new environment.

I agree that the default must inherit the environement variables, no need to state this explictly, not need to copy it.
 
>>>> it is very important to refer to the executable with an absolute path -  
>>>> on all platforms including POSIX systems
>>>
>>> Why do you say that?
>>
>> It's a requirement of Boost.Process. It doesn't need to be an absolute  
>> path but can also be a relative path of course.
> 
> Right, so it doesn't need to be an absolute path.
> 
>> What's not guaranteed  
>> though is that an executable is automatically found when only a filename  
>> is given. There is a function which searches for an executable and returns  
>> an absolute path. Would you like to see Boost.Process search for an  
>> executable automatically?
> 
> No, I'd like to see it use one of the versions of exec() that does this 
> for you.

I agree again.

Best,
Vicente