CMakeList.txt

cmake_minimum_required(VERSION 2.8.3)
project(beginner_tutorials)

## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)

## Find catkin macros and libraries
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
## is used, also find other catkin packages
find_package(catkin REQUIRED COMPONENTS
  roscpp
  rospy
  std_msgs
  message_generation
)

## Uncomment this if the package has a setup.py. This macro ensures
## modules and global scripts declared therein get installed
## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
# catkin_python_setup()

## Generate added messages and services with any dependencies listed here
generate_messages(
  DEPENDENCIES
  std_msgs
)

catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES beginner_tutorials
 CATKIN_DEPENDS #roscpp rospy std_msgs
#  DEPENDS system_lib
)

include_directories(
  ${catkin_INCLUDE_DIRS}
)

add_executable(sub_hello src/sub_hello.cpp)

add_dependencies(sub_hello ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

target_link_libraries(sub_hello
   ${catkin_LIBRARIES}
 )

package.xml

<?xml version="1.0"?>
<package format="2">
  <name>beginner_tutorials</name>
  <version>0.0.0</version>
  <description>The beginner_tutorials package</description>

  <!-- One maintainer tag required, multiple allowed, one person per tag -->
  <!-- Example:  -->
  <!-- <maintainer email="[email protected]">Jane Doe</maintainer> -->
  <maintainer email="[email protected]">nim</maintainer>


  <!-- One license tag required, multiple allowed, one license per tag -->
  <!-- Commonly used license strings: -->
  <!--   BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 -->
  <license>TODO</license>


  <!-- Url tags are optional, but multiple are allowed, one per tag -->
  <!-- Optional attribute type can be: website, bugtracker, or repository -->
  <!-- Example: -->
  <!-- <url type="website">http://wiki.ros.org/beginner_tutorials</url> -->


  <!-- Author tags are optional, multiple are allowed, one per tag -->
  <!-- Authors do not have to be maintainers, but could be -->
  <!-- Example: -->
  <!-- <author email="[email protected]">Jane Doe</author> -->


  <!-- The *depend tags are used to specify dependencies -->
  <!-- Dependencies can be catkin packages or system dependencies -->
  <!-- Examples: -->
  <!-- Use depend as a shortcut for packages that are both build and exec dependencies -->
  <!--   <depend>roscpp</depend> -->
  <!--   Note that this is equivalent to the following: -->
  <!--   <build_depend>roscpp</build_depend> -->
  <!--   <exec_depend>roscpp</exec_depend> -->
  <!-- Use build_depend for packages you need at compile time: -->
  <!--   <build_depend>message_generation</build_depend> -->
  <!-- Use build_export_depend for packages you need in order to build against this package: -->
  <!--   <build_export_depend>message_generation</build_export_depend> -->
  <!-- Use buildtool_depend for build tool packages: -->
  <!--   <buildtool_depend>catkin</buildtool_depend> -->
  <!-- Use exec_depend for packages you need at runtime: -->
  <!--   <exec_depend>message_runtime</exec_depend> -->
  <!-- Use test_depend for packages you need only for testing: -->
  <!--   <test_depend>gtest</test_depend> -->
  <!-- Use doc_depend for packages you need only for building documentation: -->
  <!--   <doc_depend>doxygen</doc_depend> -->
  <buildtool_depend>catkin</buildtool_depend>
  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>
  <build_depend>message_generation</build_depend>
  <build_export_depend>roscpp</build_export_depend>
  <build_export_depend>rospy</build_export_depend>
  <build_export_depend>std_msgs</build_export_depend>
  <exec_depend>roscpp</exec_depend>
  <exec_depend>rospy</exec_depend>
  <exec_depend>std_msgs</exec_depend>
  <exec_depend>message_runtime</exec_depend>


  <!-- The export tag contains other, unspecified, tags -->
  <export>
    <!-- Other tools can request additional information be placed here -->

  </export>
</package>

pub_hello.py

#!/usr/bin/env python

import rospy
from std_msgs.msg import String

def talker():
	pub = rospy.Publisher('hello', String, queue_size=10)
	rospy.init_node('pub_hello', anonymous=True)
	r=rospy.Rate(10)
	while not rospy.is_shutdown():
		str="hello world %s" %rospy.get_time()
		rospy.loginfo(str)
		pub.publish(str)
		r.sleep()
		
if __name__=='__main__':
	try:
		talker()
	except rospy.ROSInterruptException:
		pass

sub_hello.cpp

#include"ros/ros.h"
#include"std_msgs/String.h"

void cb_hello(const std_msgs::String::ConstPtr& msg){
	ROS_INFO("I heard: [%s]", msg->data.c_str());
}

int main(int argc, char **argv){
	ros::init(argc, argv, "sub_hello");
	ros::NodeHandle nh;
	ros::Subscriber sub = nh.subscribe("hello", 1000, cb_hello);
	
	ros::spin();
	
	return 0;
}