Unable to capture standard output of process using Boost.Process

Question

Currently am using Boost.Process from the Boost sandbox, and am having issues getting it to capture my standard output properly; wondering if someone can give me a second pair of eyeballs into what I might be doing wrong. I'm trying to take thumbnails out of RAW camera images using DCRAW (latest version), and capture them for conversion to QT QImage's. The process launch function: ``` namespace bf = ::boost::filesystem; namespace bp = ::boost::process; QImage DCRawInterface::convertRawImage(string path) { // commandline: dcraw -e -c -> piped to stdout. if ( bf::exists( path ) ) { std::string exec = "bin\dcraw.exe"; std::vector args; args.push_back("-v"); args.push_back("-c"); args.push_back("-e"); args.push_back(path); bp::context ctx; ctx.stdout_behavior = bp::capture_stream(); bp::child c = bp::launch(exec, args, ctx); bp::pistream &is = c.get_stdout(); ofstream output("C:\temp\testcfk.jpg"); streamcopy(is, output); } return (NULL); } inline void streamcopy…

Accepted Answer

Well I think that you need to redirect correctly the output stream. In my application something like this works :

```
[...]

bp::command_line cl(_commandLine);
bp::launcher l;

l.set_stdout_behavior(bp::redirect_stream);
l.set_stdin_behavior(bp::redirect_stream);
l.set_merge_out_err(true);

bp::child c = l.start(cl);
bp::pistream& is = c.get_stdout();

string result;
string line;
while (std::getline(is, line) && !_isStopped)
{
    result += line;
}

c.wait();

[...]
```

Without the redirect the stdout will go nowhere if I remember correctly. It is a good practice to wait for the process end if you want to get the whole output.

EDIT:

I'm on Linux with perhaps an old version of boost.process. i realize that your code is similar to the snippet I gave you. The c.wait() might be the key ...

EDIT: Boost.process 0.1 :-)

Unable to capture standard output of process using Boost.Process

Solution

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