how to convert shell captures into anyevent style?

[Darin McBride]

On Thursday March 29 2012 6:48:09 PM Zsbán Ambrus wrote:
> On 3/29/12, Fulko Hew <fulko.hew at gmail.com> wrote:
> >     foreach (`prog|prog|prog`) {
> > 
> > What I obviously need to do is to turn my obtainer() into an event driven
> > aspect too!  And I think what I want is an 'IO Watcher', but...
> 
> Take a look at the run_cmd function in the AnyEvent::Util module.  It
> spawns you a program (in this case you'll ask it spawn a shell so it
> interprets all those inner pipe to you) and handles reading its
> output.  When it's finished, split the output to lines.

If you really want to go all the way with AE here, making it entirely 
asynchronous, run_cmd is still the right way, but you can set some callbacks 
for stdout and stderr such that you get the lines as they come in.  I see 
nothing in the docs that say, however, that you're guaranteed to get full 
lines, though, in general, assuming short enough lines, that's what I've been 
seeing in my own usage.  That may, however, be an artefact of how my 
subprograms produce their output (they may flush on line breaks, which is a 
reasonable default for stderr).

Also, you are likely to get more than one line at a time, again, depending on 
how the buffering works out.

I have code that accumulates the output into a separate buffer, splits that on 
line breaks, sends it on to the code that is interested, but keeps partial 
lines hidden away in the buffer for the next callback, so that the business-
logic code never sees a partial line, which greatly simplifies that code.

Personally, I've done the same thing with IO::Select and IPC::Open3.  
AnyEvent::Util::run_cmd is FAR simpler to use, and to get right.