wolframroesler / childprocess

C++17 class to manage Unix child processes

Child Process Management Library

Features:

• Run a child process in the background
• Specify exact parameters, not a shell command line
• Write into the process' standard input
• Read from the process' standard output and standard error
• Wait until the process has terminated
• Get the process' exit status
• In short, encapsulates the Unix fork/exec/kill/wait system calls

Also:

• Send a termination signal to the process (in the dtor)
• Run an initialization function in the child process
• Thread-safe
• Exception-safe
• Can be used instead of system(3) and popen(3) in CERT-compliant applications

Prerequisites:

• C++17
• Boost
• Unix-like system

How to build and run the test program

This repository contains the child process library (childprocess.hpp, childprocess.cpp) together with a Boost.Test unit test program. To build and run the unit tests:

$ mkdir build
$ cd build
$ cmake ..
$ make
$ make test

How to use it in your own projects

Copy childprocess.hpp and childprocess.cpp to locations of your choise and add them to your build settings. Install and link with boost (see CMakeLists.txt for reference).

Examples

Reference code only. For complete examples refer to the unit test program (test.cpp).

Start a process and wait for termination

Run make -j test, wait for completion, and check exit status.

#include <childprocess.hpp>

auto chld = sdb::ChildProcess("/usr/bin/make", { "-j", "test" });
const auto status = child.join();
if (status!=0) {
    // Failed
}

Write to stdin, read from stdout

Run sed to convert Hello world into Good night world.

#include <childprocess.hpp>

auto chld = sdb::ChildProcess(
    "/bin/sed",
    { "s/Hello/Good night/g" },
    sdb::ChildProcess::IN | sdb::ChildProcess::OUT
);

auto in = chld.make_stdin([&data](std::ostream& os) {
    os << "Hello world\n";
});

std::string input;
auto out = chld.get_stdout([&input](std::istream& is) {
    input.assign(std::istreambuf_iterator<char>(is),std::istreambuf_iterator<char>());
});

in.get();
out.get();

const auto status = chld.join();
if (status!=0) {
    // Failed
}

// Now input is "Good night world"

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Wolfram Rösler • [email protected] • https://gitlab.com/wolframroesler • https://twitter.com/wolframroesler • https://www.linkedin.com/in/wolframroesler/