boost::process write to stdin

boost, c++, process, stdin

Solution

Here's a demo adapted from sample here:

You can see it Live on Coliru Sadly that's pushing the limits of Coliru. May be later:

#include <boost/process.hpp> 
#include <boost/assign/list_of.hpp> 
#include <string> 
#include <vector> 
#include <iostream> 

using namespace boost::process; 

int main() 
{ 
    std::string exec = find_executable_in_path("rev"); 
    std::vector<std::string> args = boost::assign::list_of("rev"); 

    context ctx; 
    ctx.environment = self::get_environment(); 
    ctx.stdin_behavior = capture_stream(); 
    ctx.stdout_behavior = capture_stream(); 
    child c = launch(exec, args, ctx); 

    postream &os = c.get_stdin();
    pistream &is = c.get_stdout(); 

    os << "some\ncookies\nfor\ntasting";
    os.close();

    std::cout << is.rdbuf(); 
}

Output:

emos
seikooc
rof
gnitsat

Now, if you need it truly asynchronous, there's another sample using Boost Asio further down that page

Problem

I have a thread starting a boost::process application, with the code the thread runs like this: ``` void Service::Run() { printf("Starting thread for service ID %i\n", this->sid); // Set up a stream sink for stdout, stderr and stdin bprocess::pipe pstdIn = create_pipe(); bprocess::pipe pstdOut = create_pipe(); file_descriptor_sink fdSink(pstdIn.sink, close_handle); file_descriptor_source fdSrc(pstdOut.sink, close_handle); // Set up the read write streams this->stdIn = new fdistream(fdSink); this->stdOut = new fdostream(fdSrc); // Execute the service try { child proc = execute( set_args(this->args), inherit_env(), bind_stdin(fdSrc), throw_on_error() ); printf("PID: %i\n", proc.pid); // Wait for the application to end then call a cleanup function int exit_code = wait_for_exit(proc); printf("Service died, error code: %i\n", exit_code); } catch(boost::system::system_error err) { printf("Something went wrong: %s\n", err.what()); } this->manager->ServiceDie(this->sid); return; } ``` As this function is a blocking one, it essentially waits for the service to be killed (Externally or as I need; input via stdin to gracefully stop the application). I have no idea how to write to the stdin of the child process. I have tried this: ``` *(this->stdIn) << "stop\n"; ``` inside a public function in the class of `Service` that's being called in another thread (`Manager` class). However this yeilds no results. How can I write to the stdin of the child `proc`?

Original source