Re: [boost] How to bind program termination with end-of-stream in Boost.Process 0.5?

Subject: Re: [boost] How to bind program termination with end-of-stream in Boost.Process 0.5?
From: alfC (alfredo.correa_at_[hidden])
Date: 2012-09-18 01:48:02

Hi Boris,

Thank you very much for your help. See below for proposed code for your library.

On Mon, Sep 17, 2012 at 7:29 PM, Alfredo Correa
<alfredo.correa_at_[hidden]> wrote:
> On Sun, Sep 16, 2012 at 11:54 AM, Boris Schaeling [via Boost]
> <ml-node+s2283326n4635834h32_at_[hidden]> wrote:
> I guess it is not not late to provide "convenience"
> pistream/postream/piostream classes that wrap up all the complexity.

If you don't mind, let me propose the following wrapper class for the
casual user. I had to play a little bit with protected inheritance to
make it work. I remember other cases where protected inheritance was
necessary in order to define derived stream classes. I kept it simple
to communicate the idea, I guess more template const Initializer& can
be passed through the constructor. An equivalent one can be made for
postream, and even piostream.

// ...
// Copyright (c) 2012 Alfredo Correa
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

/**
 * \file boost/process/pistream.hpp
 *
 * Convenience pistream class prototype
 */

#include <boost/process.hpp> // version 0.5
#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/stream.hpp>
#include <string>

namespace boost{
namespace process{

class pistream :
        protected pipe,
        protected iostreams::file_descriptor_source,
        public iostreams::stream<boost::iostreams::file_descriptor_source>{
        public:
        pistream(const std::string& cmd) :
                pipe(create_pipe()),
                file_descriptor_source(this->source, iostreams::close_handle),
                stream<file_descriptor_source>((file_descriptor_source&)(*this)){
                execute(
                        initializers::run_exe(cmd),
                        initializers::bind_stdout(iostreams::file_descriptor_sink(this->sink,
iostreams::close_handle))
                );
        }
};

}}

// example code
int main(){
    boost::process::pistream pis("/usr/bin/ls");
    std::string s;
    while(std::getline(pis, s)){
        std::cout << "read: " << s << std::endl;
    }
}

Thanks,
Alfredo

>
> boost::pistream pis("/bin/ls");
> for(std::string line; std::getline(pis, line); ){
>    std::cout << "line: " << line << std::endl;
> }
> std::cout << "end" << std::endl;
>
>>
>>> [...]ok, since there is no conclusive solution, so maybe to end this
>>> thread
>>> let me file this as a possible bug (or confirm it is the expected
>>> behavior), the symptom is that the program never ends (linux, fedora
>>> 17, boost 1.48):
>>
>> Can you try this program? It works for me:
>
> Thanks, the program worked (boost 1.48) and I posted the solution in
> stakoverflow: http://stackoverflow.com/a/12469478/225186
> I don't have any idea why this works vs. the other. I wonder if I have
> to do the same for doing output to the process.
>
> Thanks,
> Alfredo
>
>> -----
>> #include <boost/process.hpp>
>> #include <boost/iostreams/device/file_descriptor.hpp>
>> #include <boost/iostreams/stream.hpp>
>> #include <string>
>>
>> using namespace boost::process;
>> using namespace boost::process::initializers;
>> using namespace boost::iostreams;
>>
>> int main()
>> {
>>    boost::process::pipe p = create_pipe();
>>    {
>>      file_descriptor_sink sink(p.sink, close_handle);
>>      execute(run_exe("/bin/ls"), bind_stdout(sink));
>>    }
>>    file_descriptor_source source(p.source, close_handle);
>>    stream<file_descriptor_source> is(source);
>>    std::string s;
>>    while(std::getline(is, s)){
>>      std::cout << "read: " << s << std::endl;
>>    }
>>    std::clog << "end" << std::endl;
>> }
>> -----
>>
>> Boris
>>
>>> [...]
>>
>>
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>
>
>
> --
> Alfredo

-- 
Alfredo
--
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