[phobos] Suggestions for std.process

[Steve Schveighoffer]

I can help you with some aspects of it, I revamped tangos' Process object a while back.

Some things about my experience with Tango's Process:

1. I included a similar "redirect flags" option for the process, with the added ability to redirect stdout to stderr and vice versa.
2. About the searchPath flag -- Windows' function to create a process already takes into account the PATH variable, so I'm guessing that flag will be a noop on Windows?  Also, execlp and execvp already take into account the PATH.  I can't imagine you would need to build your own PATH parsing/searching method, or to run a command without taking the PATH into account (you can do this anyways by prepending a './').  My advice is to simply use one of those versions of exec, and get rid of the searchPath flag.
3. Tango's Process object included a means to specify the environment for the child process (a useful feature).  A simple argument with a string[string] for the environment variables would be useful.
4. For Windows, you do not pass in the command as an array of parameters, you pass it in as one string.  The parsing required for doing so is extremely convoluted and I only could figure it out by trial and error (documentation was incomplete).  I can help you with that.
5. Some version that parses a command line would be useful.  For example, it would be nice to be able to simply do spawn("ls -l");
6. I think your method of getting the stdout/stderr/stdin handles is a bad idea.  One can see someone not simply storing the stdout/stderr/stdin properties in an external variable and using them later, but rather always accessing the property to work with it.  This means you create a new FILE* and a new File object for each access.  I think you should store the File object directly in the Pid struct, and simply refer to it later.
7. Windows has an additional flag to specify that no console should be created.  This is very essential for things like plugins (where you don't want a black console box to pop up while running a child process).  The way I handled this in Tango is to add a gui flag which was a noop in Linux.

That's all I can think of right now.  I agree that std.process is very lacking, it is good someone is working on this.

-Steve



----- Original Message ----
> From: Andrei Alexandrescu <andrei at erdani.com>
> To: Discuss the phobos library for D <phobos at puremagic.com>
> Sent: Thu, March 4, 2010 8:18:50 AM
> Subject: Re: [phobos] Suggestions for std.process
> 
> Looks good to me. If everybody else agrees, I'd be glad to extend you an offer 
> for write access to Phobos so you can commit the changes yourself.
> 
> Andrei
> 
> Lars Tandle Kyllingstad wrote:
> > Hi,
> > 
> > Recently, I found myself in need of the functionality that is (or should have 
> been) in std.process, but unfortunately I found it lacking in many respects.  
> Assuming that improving it currently isn't at the top of the to-do list for 
> Phobos, I decided not to wait, and rather to write my own version.  If you want 
> you can check it out here:
> > 
> > Code:   http://github.com/kyllingstad/ltk/blob/master/ltk/process.d
> > Docs:   http://kyllingen.net/code/ltk/doc/process.html
> > 
> > I don't know if any of it is usable for Phobos, but if it is, I'd be happy to 
> contribute.
> > 
> > I've tried to write it in the style of std.concurrency, with a function 
> spawnProcess() that returns a Pid struct.  Currently it is for POSIX only, since 
> I have no experience at all with the Windows API.
> > 
> > -Lars
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