Compiling a YARP hello world program

The easiest way to write your first program using YARP is with CMake.

Make a directory called hello, and within it put a CMakeLists.txt file like this:

# SPDX-FileCopyrightText: 2006-2021 Istituto Italiano di Tecnologia (IIT)
# SPDX-FileCopyrightText: 2006-2010 RobotCub Consortium
# SPDX-License-Identifier: BSD-3-Clause
 
# YARP needs CMake 3.0 or greater
cmake_minimum_required(VERSION 3.19)
 
# find YARP
find_package(YARP COMPONENTS os REQUIRED)
 
# set up our program
add_executable(hello)
 
# declare our source files
target_sources(hello PRIVATE hello.cpp)
 
# link with YARP libraries
target_link_libraries(hello PRIVATE YARP::YARP_os
                                    YARP::YARP_init)

And here's a simple test program, call it hello.cpp

/*
 * SPDX-FileCopyrightText: 2006-2021 Istituto Italiano di Tecnologia (IIT)
 * SPDX-FileCopyrightText: 2006-2010 RobotCub Consortium
 * SPDX-License-Identifier: BSD-3-Clause
 */
 
#include <yarp/os/all.h>
#include <stdio.h>
using namespace yarp::os;
 
int main(int argc, char *argv[]) {
 
  // Set up YARP
  Network yarp;
 
  // Make two ports called /hello/in and /hello/out
  // We'll send "Bottles" (a simple nested list container) between these ports
  BufferedPort<Bottle> inPort, outPort;
  bool ok = inPort.open("/hello/in");
  ok = ok && outPort.open("/hello/out");
  if (!ok) {
    fprintf(stderr, "Failed to create ports.\n");
    fprintf(stderr, "Maybe you need to start a nameserver (run 'yarpserver')\n");
    return 1;
  }
 
  // Make a connection between the output port and the input port
  yarp.connect(outPort.getName(),inPort.getName());
 
  for (int i=0; i<10; i++) {
 
    // prepare a message to send
    Bottle&out = outPort.prepare();
    out.clear();
    out.addString("Hello");
    out.addInt32(i);
    printf("Sending %s\n", out.toString().c_str());
 
    // send the message
    outPort.write(true);
 
    // read the message
    Bottle *in = inPort.read();
    if (in==NULL) {
      fprintf(stderr, "Failed to read message\n");
      return 1;
    }
    printf("Received %s\n", in->toString().c_str());
  }
 
  return 0;
}

Now make a build directory inside the hello folder, then from the build directory run CMake (see Using CMake), and compile!

This example is available in the example/cmake/hello directory of the YARP source code.